JP2006328574A - Coated white paperboard - Google Patents

Abstract

【Task】
Regarding coated white paperboard, more specifically, coated whiteboard that has a beautifully decorated white paper appearance with excellent surface properties and that can be used for both offset and gravure printing, and has no printing trouble etc. To provide paper.
[Solution]
In the coated white paperboard, 3 to 10% by mass of rutile-type titanium dioxide as a pigment of the whole coating layer including the undercoat layer and the topcoat layer is contained in the total amount of the solid content per pigment of the whole coating layer. The content of rutile-type titanium dioxide is 0.3 to 1.0 in the entire coating layer including the undercoat and topcoat layers, thereby covering and concealing undeinked fibers derived from waste paper pulp and increasing the base paper coverage Thus, it becomes possible to obtain a coated white paperboard having a more excellent white paper appearance.
[Selection]
None

Description

The present invention relates to coated white paperboard. More particularly, the present invention relates to a coated white paperboard that has a cosmetics white paper appearance with excellent surface properties and that can be used for both offset and gravure printing, has no printing trouble, and has excellent printability.

The coated white paperboard is mainly used after printing into a decorative box, a soap box, or a gift case box. Therefore, it is required not only that the printability is excellent, but also that the white surface of the coated surface is good. However, it is not only coated white paperboard but also general paperboard, and the raw material that makes up the base paper layer uses waste paper pulp that is disaggregated and carefully selected from newspapers, magazines, flyers, etc. Compared with bleached chemical pulp that has been subjected to the treatment, the whiteness is low, and the fine paper has not been thoroughly selected.

Therefore, in constituting the base paper layer, many bleached chemical pulps are blended in the surface layer, many expensive high white pigments are blended in the coating layer coated on these base paper layers, and the coating layer For example, it is currently commercialized by the methods of Patent Document 1, Patent Document 2, and Patent Document 3, for example. In particular, in Patent Document 3, the printing opacity of the coated paper for printing is greatly improved by using deinked waste paper pulp and coating with titanium dioxide on the base paper. Further improvement is desired for dullness caused by ink.

Furthermore, in recent years, as part of building a recycling-oriented society, there is a social demand for the use of recycled materials as much as possible. In light of this, considering coated white paperboard, it is possible to increase the amount of waste paper pulp as much as possible, and to use a coating layer composed of pigments as mineral resources or synthetic adhesives manufactured from petroleum resources. It is desirable to reduce it as much as possible.

However, there is a conflict with the required quality of the current paper, and the required quality has been improving year by year, and there has been a demand for coated white paperboard with a more beautiful cosmetic appearance and good white paper appearance. At present, satisfactory coated white paperboard has not yet existed.
JP 2000-336593 A JP 2000-054288 A Japanese Examined Patent Publication No. 06-043676

The present invention relates to a coated white paperboard which has a cosmetics white paper appearance with excellent surface properties and can be used for both offset and gravure printing and has no printing trouble and has excellent printability. .

The present invention adopts the following configurations (1) to (3) as means for solving the above problems.
(1) Using recycled paper pulp obtained by disaggregating / selecting used paper, the surface of the laminated base paper composed of at least three layers of a surface layer, a middle layer, and a back layer contains a pigment and an adhesive as main components. In coated white paperboard having two coating layers, rutile type titanium dioxide is used as the pigment of the entire coating layer including the undercoat layer and the topcoat layer in a solid content ratio of 3 to 10% by mass relative to the total pigment of all the coating layers. A coated white paperboard, characterized in that the content of rutile titanium dioxide in the undercoat layer satisfies the following conditions.
0.3 <a / b ≦ 1.0
a: Content of rutile titanium dioxide used in the undercoat layer b: Content of rutile titanium dioxide in all coating layers including the undercoat and topcoat layers (2) 90% by mass of the particle size distribution of the rutile titanium dioxide The coated white paperboard as set forth in the item (1), wherein the ratio of the particle size to 50% by mass is less than 2.0.
(3) The coating apparatus according to (1) or (2), wherein the coating apparatus for forming the undercoat layer and the overcoat layer is formed by using a rod coater for the undercoat layer and a blade coater for the overcoat layer. White paperboard.

According to the present invention, it is possible to provide a coated white paperboard that has a cosmetics white paper appearance with excellent surface properties, can be shared for offset and gravure printing, and does not cause printing troubles and has excellent printability. .

Generally, coated white paperboard which has two coating layers on the surface of the laminated base paper composed of at least three layers of surface layer, middle layer and back layer, using waste paper pulp that is obtained by disaggregating and carefully selecting waste paper In this case, the whiteness and the appearance of the white paper are reduced due to the use of the used paper pulp. In order to compensate for this, it is common to add a lot of bleached chemical pulp to the base paper layer, particularly the base paper surface layer side, but this is not preferable because of high cost. In addition, expensive white pigments such as calcium carbonate, titanium dioxide, calcined kaolin, etc. are generally used as countermeasures in the coating layer, but these pigments have poor glossiness, and gloss increases when the formulation is increased. There is a problem of declining. Furthermore, as a method for solving this problem, there is a method of thickening the coating layer, that is, a method of increasing the coating amount, but this is liable to cause troubles such as deterioration of ruled cracks when used as a paper container after printing and is expensive This is not preferable because of the high cost combined with the high white pigment blending.

Therefore, as a result of intensive studies to solve the above-mentioned problems, the present inventors use waste paper pulp obtained by disaggregating and carefully selecting waste paper, and have at least three layers of a surface layer, a middle layer, and a back layer. In coated white paperboard having two coating layers containing pigment and adhesive as main components on the surface of laminated base paper composed of layers, as a pigment for all coating layers including undercoat layer and topcoat layer When the rutile type titanium dioxide is contained in an amount of 3 to 10% by mass relative to the total pigment content of all the coating layers and the content of the rutile type titanium dioxide in the undercoat layer satisfies the following conditions, sufficient white paper appearance Have
0.3 <a / b ≦ 1.0
a: Content of rutile titanium dioxide used in the undercoat layer b: Content of rutile titanium dioxide in all coating layers including the undercoat and topcoat layers, and can be used for offset and gravure printing, and printing troubles, etc. It was possible to obtain coated white paperboard having no printability and excellent in printability, and the desired purpose of the present invention could be achieved.

In addition, the following requirements are extremely important factors in completing the present invention.
1. A coated white paperboard, wherein the ratio of the particle size distribution of 90% by mass and the particle size of 50% by mass of the particle size distribution of rutile-type titanium dioxide which is a pigment of the entire coating layer is less than 2.0.
2. A coated white paperboard, characterized in that, as a coating apparatus for forming the undercoat and topcoat layers of the coating layer, the undercoat layer is formed by a rod coater and the topcoat layer is formed by a blade coater.

The reason why the printability is excellent while satisfying the excellent white surface appearance of the coated surface with the coating layer structure as described above is not necessarily clear, but is estimated as follows.
That is, the titanium dioxide used in the coating layer of the present invention is a pigment generally known in the field of coated paper for printing as a high white opaque pigment having excellent hiding properties among pigments. This high white pigment, titanium dioxide, is blended in a specific amount in a coating layer consisting of two layers of coated white paperboard, and contained in a specific amount of the undercoat layer to cover and conceal undeinked fibers derived from waste paper pulp. In addition, it has been found that the coated whiteboard having a more excellent white paper appearance can be obtained than the case where the base paper coverage is increased, and the coated whiteboard is usually formed only by using titanium dioxide in the overcoat layer. .

Further, it is particularly important to contain a specific amount in the undercoat layer here. In general, coated white paperboard is coated, dried, and then smoothed using a super calender or soft calender for glossing. At this time, the pigment in the outermost layer of the coating layer is oriented, the latex of the adhesive is plasticized, and as a result, the opacity of the outermost layer of the coating layer is lowered. Therefore, it is considered that the effect of titanium dioxide is expressed more by blending into the undercoat layer than blending titanium dioxide into the overcoat layer forming the outermost layer of the coating layer.

Furthermore, it is more preferable to use and mix rutile type titanium dioxide as the titanium dioxide for obtaining the effects of the present invention. Titanium dioxide is generally classified into two types: rutile type and anatase type. It has been conventionally known that the rutile type is more concealed and exhibits higher opacity than the anatase type. This is a more preferable pigment for obtaining the above effect.

In addition, in the particle size distribution of rutile-type titanium dioxide as described above, by containing rutile-type titanium dioxide in which the ratio of the particle size of 90% by mass to the particle size of 50% by mass is less than 2.0, a white paper appearance Excellent coated white paperboard can be obtained.

In addition, by coating with a rod coater as a coating device for forming the undercoat layer, it becomes possible to coat the surface of the white paperboard base paper in a more contoured manner, and undeinked fibers derived from waste paper pulp as a whole The effect of coating and using the titanium dioxide in the coating layer is further enhanced.
For the reasons described above, it is considered that a coated white paperboard which is excellent in surface appearance and has a beautiful white paper appearance, which can be used for both offset and gravure printing, and which has excellent printability.

In the present invention, it is important that 3 to 10% by mass of titanium dioxide is contained as a pigment of the entire coating layer in comparison with the solid content per total pigment, and the content of the undercoat layer satisfies the following conditions.
0.3 <a / b ≦ 1.0
a: Content of titanium dioxide used in undercoat layer b: Content of titanium dioxide in all coating layers including undercoat and topcoat layers As described above, titanium dioxide is a highly concealing pigment, and it is divided into two layers. It is derived from the waste paper pulp that constitutes the base paper more by blending and containing in the undercoat layer of the coating layer in a ratio and range of 0.3 to 1.0 with respect to the content of titanium dioxide in the entire coating layer. The non-deinked fiber concealability is improved, and a coated white paperboard having an excellent white paper appearance is obtained.

As a compounding quantity, it is important to contain 3-10 mass% with respect to solid content with respect to all the coating layer all pigments, More preferably, it is 5-10 mass%. If it is less than 3% by mass, sufficient concealability cannot be obtained. On the other hand, if it exceeds 10% by weight, the glossiness of the white paper is lowered, and it is expensive compared with the pigment used in the general coated paper field, which is not preferable because of high cost. In addition, the ratio of the blending of the two coating layers into the undercoat layer is in the range of 0.3 to 1.0 with respect to the content of titanium dioxide in the entire coating layer. As described above, this means that titanium dioxide having high concealment and high opacity is distributed to the coating layer composed of two layers, or blended in the undercoat layer alone, and particularly in obtaining the effects of the present invention. is important. When the ratio to the undercoat layer is less than 0.3, the distribution of the entire titanium dioxide coating layer is not uniform, and the concealing effect is not sufficiently exhibited.

Further, as described above, it is more preferable to use and blend rutile type titanium dioxide as titanium dioxide for obtaining the effects of the present invention.
In addition, the particle size distribution of the rutile titanium dioxide measured with an X-ray transmission type particle size distribution analyzer (Cedigraph 5000-01 / manufactured by Shimadzu Corporation) is 90% by mass and 50% by mass. Specific rutile-type titanium dioxide having a ratio of less than 2.0 is included. This indicates that the particle size distribution is relatively uniform from fine to coarse, and the one with such a particle size distribution more uniformly covers the surface of the paperboard with relatively large irregularities. However, since it is easy to form a uniform coating layer, it is estimated that the coverage of the base paper is improved as a result.

Moreover, as a coating apparatus for forming the undercoat layer, coating with a rod coater is effective in expressing the titanium dioxide concealing ability. It is not limited to white paperboard, but various coating devices are used in the general coated paper field. Among them, the rod coater has a uniform coating layer along the contour of the surface of the paperboard with relatively large irregularities. This is because it is a coating device that is easy to form.

As described above, the present invention can be obtained by blending a specific amount of specific titanium dioxide in the entire coating layer composed of two layers and mixing a specific amount of specific titanium dioxide in the undercoat layer. It is possible to achieve an excellent effect. Moreover, as other materials, it can use suitably in the range which does not impair the outstanding effect of this invention.

First, as the pigment, pigments other than titanium dioxide defined in the present invention, such as ordinary kaolin, heavy calcium carbonate, light calcium carbonate, aluminum hydroxide, silica, talc, and satin white are used in the general coated paper manufacturing field. Both the undercoat layer and the overcoat layer can be used as appropriate as long as at least one of the known publicly used pigments does not impair the effects of the present invention.

Next, the adhesive which is a main component other than the pigment of the coating layer is not particularly limited, and an adhesive used in the field of manufacturing general coated paper can be appropriately used. Specific examples include, for example, proteins such as casein, soybean protein, synthetic protein, starches such as positive starch, oxidized starch and thermochemically modified starch, cellulose derivatives such as carboxymethyl cellulose and hydroxyethyl cellulose, polyvinyl alcohol, olefin / maleic anhydride Examples thereof include synthetic resin latex such as resin, melamine resin, styrene-butadiene copolymer latex, vinyl acetate copolymer latex, acrylic copolymer latex, and urethane copolymer latex. These adhesives may be used alone or in combination of two or more.
In addition, if necessary, in paint, 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 also be added suitably.

As the coating amount of the coating material, 5 to 15 g / m ² on a dry weight for the undercoat layer, at 3 to 15 g / m ² on a dry weight for overcoat layer and the undercoat, the sum of the coating amount of overcoat It is desirable to prepare in the range of 8-25 g / m < ² > by dry mass. Incidentally, if the undercoat layer is less than 5 g / m ² , the surface of the base paper cannot be sufficiently covered, and the desired white paper appearance of the present invention cannot be obtained. If it exceeds 15 g / m ² , a ruled line is put in the box during box making. In such a case, the coating layer may be cracked. Further, the overcoat layer is sufficiently cause ink transfer failure or the like can not be clothing the undercoat layer surface is less than 3 g / m ^2, offset, quality that satisfies can not be obtained for gravure printing both exceeds 15 g / m ² As in the case of the undercoat layer, if a ruled line is put into a box at the time of boxing, the coating layer may be cracked, which is not preferable.

The coating apparatus for applying the paint to the base paper and the paper provided with the undercoat layer is not particularly limited. For example, air knife coater, blade coater, rod coater, bar coater and gate roll coater, size press, etc. Roll coater, bill blade coater, velbapa coater, etc. are used in appropriate combinations within the range not impairing the effects of the present invention, more preferably as a base paper coating apparatus, a rod coater, to a paper provided with an undercoat layer. As the coating apparatus, a blade coater exhibits the effects of the present invention more preferably.

As described above, the rod coater as an undercoat paint coating device can relatively apply contour coating along the unevenness of the surface of the base paper, and can also perform high concentration and high speed coating. In addition, the blade coater as a top coater coating device can provide a highly smooth coated surface, and as a result, it is easy to obtain smoothness that satisfies printability. Also, as with the undercoat rod coater, it is suitable for high concentration and high speed coating. Because of its superiority.

In addition, the smoothing process of the paper which provided the base paper and the undercoat layer previously can also be performed using a machine calendar, a soft calendar, a Yankee dryer, etc. before coating. Further, it is desirable to apply a smoothing treatment using a machine calendar, a soft calendar, a super calendar, or the like after coating and drying the overcoat layer paint.

The base paper is composed of at least three layers of surface, middle and back layers, and the pulp used is not particularly limited. For example, bleached or unbleached chemical pulp, mechanical pulp, One kind of ink or undeinked waste paper pulp, or a mixture of two or more kinds is used as appropriate. In general, as white paperboard, used paper pulp or bleached chemical pulp is used for the surface layer and the lower surface layer. Ink waste paper pulp is often used to form the base paper of coated white paperboard. In addition, a sizing agent, a paper strength agent, a chemical stabilizer, a filtering agent, a filler, a dye, and the like can be appropriately added to the base paper as necessary. Incidentally, the basis weight of the base paper is usually 150~650g / m ² approximately.

The present invention will be specifically described below with reference to examples. Of course, the present invention is not limited to these examples. In addition, unless otherwise indicated, the part and% in an example show "mass part" and "mass%", respectively.

<Example 1>
[Preparation of undercoat paint]
As pigments, 45 parts of structured kaolin (trade name: Mirana 894 / Engelhard), 50 parts of heavy calcium carbonate (trade name: Hydrocurve 60 / Bihoku Powder Chemical Co., Ltd.), rutile titanium dioxide (trade name: JR600A) / Taika Co., Ltd.) 5 parts were used, 0.2 part of sodium polyacrylate was added to the pigment as a dispersant, and a pigment slurry having a solid content concentration of 70% was prepared using a Coreless disperser. 5 parts of oxidized starch (trade name: Ace A / Oji Cornstarch) and 15 parts of styrene-butadiene copolymer latex (trade name: X-400A / JSR) having a glass transition temperature of −23 ° C. were added to this slurry. Then, water was further added to prepare a paint having a solid content concentration of 62%.

[Preparation of top coat]
As pigments, kaolin (trade name: UW-90 / Engelhard) 60 parts, light calcium carbonate (trade name: TP-221-GS / Okutama Kogyo) 38 parts, rutile titanium dioxide (trade name: JR600A / Taika) 2 parts), 0.2 part of sodium polyacrylate as a dispersant was added to the pigment, and a pigment slurry having a solid content of 68% was prepared using a Coreless disperser. To this slurry, 3 parts of phosphate esterified starch (trade name: MS-4600 / Nihon Shokuhin Kako Co., Ltd.) and styrene-butadiene copolymer latex (trade name: L-1825 / Asahi Kasei Co., Ltd.) with a glass transition temperature of 8 ° C. 18 Each part was added, and water was further added to prepare a paint having a solid content of 60%.

[Preparation of base paper]
On the surface layer of the base paper white board of 290 g / m ² , which is made up of 5 layers using undeinked waste paper pulp for the surface layer, lower surface layer, and undeinked waste paper pulp for the middle layer and the back layer, The undercoat paint obtained in (1) was coated using a rod coater so that the dry weight per side was 10 g / m ² and dried to obtain an undercoat base paper.

[Coating of coated white paperboard]
The base coat obtained in this way was coated and dried with the above-described overcoating paint using a blade coater so that the dry weight per side was 10 g / m ^2, and then the metal roll surface temperature was 150 ° C. The paper was passed through a 2-nip soft calender to obtain a coated white board with two coating layers.

<Example 2>
In the preparation of the undercoat paint of Example 1, 3 parts of rutile titanium dioxide (trade name: JR600A / supra) and 47 parts of structured kaolin (trade name: Mirrorana 894 / supra) are used as pigments. Coating was carried out in the same manner as in Example 1 except that 6 parts of rutile titanium dioxide (trade name: JR600A / supra) and 34 parts of light calcium carbonate (trade name: TP-221-GS / supra) were used as pigments. White paperboard was obtained.

<Example 3>
In the preparation of the undercoat paint of Example 1, 7 parts of rutile titanium dioxide (trade name: JR600A / supra) and 43 parts of structured kaolin (trade name: Mirrorana 894 / supra) are used as pigments. In the same manner as in Example 1 except that 40 parts of light calcium carbonate (trade name: TP-221-GS / Okutama Kogyo Co., Ltd.) and rutile titanium dioxide (trade name: JR600A / supra) were not added as pigments. Coated white paperboard was obtained.

<Example 4>
In the preparation of the top coat of Example 1, except that 10 parts of rutile titanium dioxide (trade name: JR600A / supra) and 30 parts of light calcium carbonate (trade name: TP-221-GS / supra) were used as pigments. In the same manner as in Example 1, a coated white paperboard was obtained.

<Comparative Example 1>
A coated white paperboard is obtained in the same manner as in Example 1 except that anatase type titanium dioxide (TCA123 / Sakai Chemical Industry Co., Ltd.) is used instead of rutile type titanium dioxide / JR600A. It was.

<Comparative Example 2>
In the preparation of the undercoat paint of Example 1, 50 parts of structured kaolin (trade name: Mirana 894 / supra) and rutile-type titanium dioxide (trade name: JR600A / supra) were not added as pigments to prepare a top coat. In Example 1, except that 5 parts of rutile titanium dioxide (trade name: JR600A / supra) and 35 parts of light calcium carbonate (trade name: TP-221-GS / supra) were used as pigments. White paperboard was obtained.

<Comparative Example 3>
In the preparation of the undercoat paint of Example 1, 50 parts of structured kaolin (trade name: Mirana 894 / supra) and rutile-type titanium dioxide (trade name: JR600A / supra) were not added as pigments to prepare a top coat. In Example 1, except that 40 parts of light calcium carbonate (trade name: TP-221-GS / Okutama Kogyo Co., Ltd.) and rutile type titanium dioxide (trade name: JR600A / supra) were not added. White paperboard was obtained.

<Comparative example 4>
In the preparation of the undercoat paint of Example 1, 2 parts of rutile type titanium dioxide (trade name: JR600A / supra) and 48 parts of structured kaolin (trade name: Mirana 894 / supra) are used as pigments. As a pigment, 12 parts of rutile titanium dioxide (trade name: JR600A / supra) and 28 parts of light calcium carbonate (trade name: TP-221-GS / supra) are used instead of the rod coater in the preparation of the base paper. A coated white paperboard was obtained in the same manner as in Example 1 except that the blade coater was used.

The coated white paperboards in Examples and Comparative Examples obtained as described above were conditioned for 6 hours under the conditions in accordance with JIS P8111, evaluated for white paper appearance, surface strength / ink transferability in offset printing (ink absorption unevenness) ), And evaluation of misdots in gravure printing and ink transferability (ink absorption unevenness).
The coating composition of the coating layer in each Example and Comparative Example is shown in Table 1, and the evaluation results are shown in Table 2. In addition, each evaluation test was implemented according to the following.

(Blank paper appearance): The coated surface was visually evaluated.
A: There are no black spots derived from deinked fibers and no uneven gloss.
◯: There is no gloss unevenness, but black spots derived from deinked fibers are slightly observed.
Δ: Some uneven gloss and black spots derived from deinked fibers are observed.
X: Uneven gloss, black spots derived from deinked fibers are conspicuous, and the white paper appearance is remarkably inferior.

(Ink transferability in offset printing): Offset printing was performed using an offset sheet-fed printing machine (Mitsubishi Diamond 4E-4 / Mitsubishi Heavy Industries), and visually evaluated.
A: The transfer of the ink onto the coated surface is uniform and there is no uneven absorption.
○: Some absorption unevenness is recognized depending on the gradation part.
(Triangle | delta): Transferability is somewhat non-uniform | heterogenous and some absorption unevenness is recognized.
X: Transfer is poor and uneven absorption is poor.

(Surface Strength): Visually evaluated after printing using an offset ink with an RI printing machine (manufactured by Meisei Seisakusho): Very good. ○: Good. Δ: Slightly inferior X: Inferior.

(Misdot): Gravure printing was performed using a Ministry of Finance gravure printing tester, and the degree of dot missing (miss dot) was visually evaluated.
A: There are no missing dots.
○: Some missing dots are recognized depending on the gradation part (low gradation part).
Δ: Some halftone dots are missing even in the high gradation part.
X: Many missing dots are observed in all gradation portions.

(Ink transferability in gravure printing): Gravure printing was performed using a Ministry of Finance gravure printing tester and visually evaluated.
A: The transfer of the ink onto the coated surface is uniform and there is no uneven absorption.
○: Some absorption unevenness is recognized depending on the gradation part.
(Triangle | delta): Transferability is somewhat non-uniform | heterogenous and some absorption unevenness is recognized.
X: Transfer is poor and uneven absorption is poor.

表２より明らかなように、本発明に係る塗工白板紙は、表面性の優れた美粧性のある白紙外観を有し、オフセットおよびグラビア印刷に共用可能で印刷トラブル等の発生のない、いずれの印刷適性にも優れた塗工白板紙を提供できる。

As is apparent from Table 2, the coated white paperboard according to the present invention has a cosmetics white paper appearance with excellent surface properties, can be shared for offset and gravure printing, and does not cause printing troubles. It is possible to provide coated white paperboard having excellent printability.

INDUSTRIAL APPLICABILITY The present invention can be used for coated white paperboard that has a cosmetics white paper appearance with excellent surface properties and can be used for offset and gravure printing.

Claims (3)

A two-layer paper containing a pigment and an adhesive as the main components on the surface of a laminated base paper composed of at least three layers of a surface layer, a middle layer and a back layer, using waste paper pulp obtained by disaggregating and carefully selecting waste paper In the coated white paperboard having the coating layer, as a pigment of the entire coating layer including the undercoat layer and the topcoat layer, rutile titanium dioxide is contained in an amount of 3 to 10% by mass relative to the solid content of all pigments of the entire coating layer. The coated white paperboard is characterized in that the content of rutile titanium dioxide in the undercoat layer satisfies the following conditions.
0.3 <a / b ≦ 1.0
a: Content of rutile type titanium dioxide used for undercoat layer b: Content of rutile type titanium dioxide in all coating layers including undercoat and topcoat layer 2. The coated white paperboard according to claim 1, wherein a ratio of a particle size of 90% by mass to a particle size of 50% by mass in the particle size distribution of the rutile titanium dioxide is less than 2.0. The coated white paperboard according to claim 1 or 2, wherein as the coating apparatus for forming the undercoat and overcoat layers, the undercoat layer is formed with a rod coater and the overcoat layer is formed with a blade coater.