JP2007262643A - Coated paper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coated paper which is adapted to a large off-set printing machine and which does not adhere to the printing cylinder and does not form wrinkles during printing, which has an improved ink-drying property, an improved printability, a high white paper glossiness, and a low basis weight. <P>SOLUTION: The coated paper has at least one side of a base paper provided with two or more coating layers including a pigment and an adhesive as main components, the coated paper has a base coating layer in contact with the base paper including at least 50 pts mass of a flat pigment per 100 pts mass of the total amount of the pigments, the flat pigment satisfies the following conditions (1) and (2), and has a Clark stiffness in a CD direction of at least 14 cm and a white paper glossiness of at least 45%, wherein (1) an average particle size of 0.2-5.0 μm, determined by the sedimentation method: (2) an aspect ratio (major diameter/thickness) of 25-120. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention is compatible with a large offset printing press, has no sticking to the printing cylinder or wrinkles during printing, has good ink drying properties, improved printing workability, high blank paper gloss, 80 g / It relates to coated paper having a basis weight of m ² or less.

  In general, a coated paper for printing is manufactured by applying a coating liquid mainly composed of a pigment and an adhesive to at least one side of a base paper and drying it. The coated paper for printing is classified into cast coated paper, art paper, coated paper, fine coated paper, and the like depending on the coating amount of the coating liquid and the finishing method of the coated paper. These coated papers are subjected to multicolor printing or single color printing, and are widely used as commercial printed materials such as flyers, brochures and posters, or as publications such as books and magazines.

  In recent years, direct mail has been visualized and colored in order to increase the level of attention from customers by providing information. With direct mail, the mailing fee varies depending on the weight of the contents, so there is a strong demand for lighter and thinner printed coated paper for cost reduction. In addition, there is a trend toward shorter delivery times.

  In order to improve the rigidity of the coated paper for printing, a technique for improving the rigidity by increasing the bulk of the coated paper by decreasing the density of the coated paper and increasing the thickness of the paper has been proposed. Specifically, a method of making the base paper itself bulky by adding a bulking agent (see Patent Documents 1 and 2), a method of treating the coating layer applied on the base paper with a thermal soft calender or the like (Patent Documents 3 to 5) For example, a method of using a hollow plastic pigment as a pigment to be blended in the coating layer (see Patent Documents 6 to 7) has been conventionally proposed.

  In other words, the conventional proposal for increasing the bulk is to use a relatively bulky base paper as a base paper for printing coated paper, and to apply a calendar treatment to the coated paper obtained by applying the coating liquid onto the base paper. It is to reduce the pressing force applied to the base paper and the coating layer as much as possible. However, when the pressing force during the calendar process is reduced, the smoothing improving effect of the coating layer due to the calendar process may be smaller than when the pressing force is not reduced. The rigidity cannot be achieved. In addition, no technology has yet been found that can achieve both white paper glossiness and ink drying properties.

JP 2002-155494 A JP 2003-171893 A Japanese Patent Laid-Open No. 06-192996 JP 09-228298 A Japanese Patent Laid-Open No. 06-294100 Japanese Patent Laid-Open No. 2002-22095 JP 09-1119090 A

  The present invention aims to ameliorate the above problems, and when printed with a large offset printing press, there is no sticking to the printing cylinder or generation of wrinkles and good ink drying properties. Thus, a low basis weight coated paper having improved printing workability and high white paper gloss is provided.

  As a result of intensive investigations to achieve the above object, the present inventors have found that in a coated paper in which two or more coating layers mainly composed of a pigment and an adhesive are provided on at least one side of the base paper, The pigment component of the undercoat coating layer in contact with the coating layer has a coating layer containing at least 50 parts by mass of a flat pigment in 100 parts by mass of the total pigment, and the coated paper having predetermined physical properties is applied to the printing cylinder. It has been found that the generation of wrinkles and wrinkles is suppressed, the ink drying property is good, and the printing workability can be remarkably improved.

That is, the coated paper according to the present invention is provided with at least one coating layer mainly composed of a pigment and an adhesive on at least one side of the base paper, and preferably in the undercoat coating layer in contact with the base paper. The coated paper contains 50 parts by mass or more of a flat pigment that satisfies the following conditions (1) and (2) per 100 parts by mass of the total pigment, and the coated paper has a Clark stiffness in the CD direction. Is 14 cm or more, and the white paper glossiness of the surface is 45% or more.
(1) Average particle diameter measured by sedimentation method: 0.2 to 5.0 μm
(2) Aspect ratio (major axis / thickness): 25-120
The flat pigment is preferably engineered kaolin. The air permeability of the coated paper is preferably 7000 seconds or less. Furthermore, it is preferable that the adhesive agent component of the said undercoat coating layer is 5-30 mass parts per 100 mass parts of pigment components contained in an undercoat coating layer.
The fiber orientation ratio of the base paper is preferably 1.00 to 1.50, and the fiber orientation ratio measured from the surface of the coated paper is preferably 1.00 to 1.50. The basis weight of the coated paper is preferably 35~80g / m ^2. Furthermore, it is preferable that 0.5 g / m ² or more of fine particles having a particle size of 500 nm or less are contained in the overcoat layer on the undercoat layer. Preferably, spherical particles having an average particle diameter of 1 to 50 μm are contained in the undercoat coating layer.

  The coated paper obtained according to the present invention has no sticking to the printing cylinder or wrinkles when printed on a large offset printing press, has fast ink drying properties, improves printing workability, and is glossy on white paper. A product having a high degree and a low basis weight is obtained, which is practically useful.

  The flat pigment contained in the coating layer of the present invention preferably has an average particle diameter of 0.2 to 5.0 μm by a precipitation method and an aspect ratio (major diameter / thickness) in the range of 25 to 120, more preferably. An average particle diameter exists in the range of 0.2-4.0 micrometers, and a more preferable aspect ratio exists in the range of 30-100. When the average particle diameter is larger than 5.0 μm or the aspect ratio is larger than 120, the CD stiffness of the resulting coated paper is increased, but the air permeability is increased or the white paper glossiness is decreased. In some cases, the glossiness of the white paper and the air permeability of 7000 seconds or less, preferably 5000 seconds or less, more preferably 4000 seconds or less may not be achieved. On the other hand, when the average particle diameter is smaller than 0.2 μm or the aspect ratio is smaller than 25, high white paper glossiness is obtained, but this may lead to an increase in air permeability and a decrease in CD stiffness.

  Further, the flat pigment contained in the undercoat layer of the coated paper according to the present invention, preferably only in the undercoat layer, has an average particle diameter of 0.2 to 5.0 μm by the precipitation method, and has an aspect ratio. The ratio is preferably in the range of 25 to 120, the more preferable average particle diameter is in the range of 0.2 to 4.0 μm, and the more preferable aspect ratio is in the range of 30 to 100. Such flat pigment is preferably engineered kaolin. The degree of flatness (flatness) of ordinary delaminated kaolin is generally expressed using the aspect ratio (major axis / thickness). The higher the aspect ratio, the thinner and wider the pigment particle shape, and the larger flatness. It represents a pigment shape of (high flatness). Although the numerical value of the aspect ratio of delaminate kaolin generally used is about 15 to 20, the flat pigment used in the present invention has a high flatness of about 25 to 120 as described above, and the aspect ratio is 30-100 are more preferable.

  As mentioned above, it is not yet fully understood that flat pigments with a high aspect ratio shape have the effect of increasing the CD stiffness, but the flat pigments are layered and laterally connected, increasing the stiffness. It is estimated that.

  In the present invention, it is particularly effective to blend the flat pigment into the undercoat layer, but it is also possible to blend it into the overcoat layer as long as the desired quality is not deteriorated.

  Other pigments used in combination with flat pigments as the pigment component of the undercoat coating layer include calcium carbonate, kaolin, calcined kaolin, delaminated kaolin, talc, calcium sulfate, barium sulfate, aluminum hydroxide, satin white, and nitric oxide. Inorganic pigments such as titanium, zinc oxide, alumina, magnesium carbonate, magnesium oxide, silica, magnesium aluminosilicate, calcium silicate bentonite, zeolite, sericite, smectite, polystyrene resin, styrene-acrylic copolymer resin, urea resin, melamine resin Organic pigments such as solid, hollow or through-hole type resins such as acrylic resin, vinylidene chloride resin and benzoguanamine resin can also be used, and one or more of them may be appropriately selected.

  The adhesive component of the undercoat coating layer is preferably 5 to 30 parts by mass, more preferably 7 to 20 parts by mass, per 100 parts by mass of the pigment component contained in the undercoat coating layer. If the adhesive component is less than 5 parts by mass, the strength of the coating layer is low, and printing may not be possible. On the other hand, if it exceeds 20 parts by mass, it may lead to a decrease in ink drying due to a rapid increase in air permeability and a decrease in glossiness of the coated paper due to a decrease in smoothness.

  The adhesive component of the undercoat coating layer includes conjugated diene polymer latex such as styrene-butadiene copolymer and methyl methacrylate-butadiene copolymer, acrylic polymer latex, vinyl such as ethylene-vinyl acetate copolymer, etc. Examples thereof include a polymer latex. 1 type (s) or 2 or more types can be used suitably for the said adhesive agent.

  A water-soluble adhesive can also be used in combination. Examples of water-soluble adhesives include various starches such as oxidized starch, esterified starch and cold water soluble starch, proteins such as casein, soy protein and synthetic protein, cellulose derivatives such as carboxymethylcellulose and methylcellulose, polyvinyl alcohol and modified products thereof. Etc. can be exemplified.

  The spherical particles in the undercoat coating layer preferably have an average particle diameter of 1 to 50 μm. More preferably, spherical particles having a particle diameter larger than the thickness of the undercoat coating layer can be used. Moreover, it is preferable that the compounding quantity of the spherical particle in an undercoat coating layer is 1-40 mass parts per 100 mass parts of all the pigment components. By the way, when the average particle size is smaller than 1 μm, or when the blended amount of the spherical particles is less than 1 part by mass, it is difficult to form convex portions on the surface of the coating layer or the number of convex portions is small, so that coating is performed. As a result, the friction coefficient of the layer surface increases, and as a result, the adhesion between papers increases, and double feeding may occur in the paper feeding unit of the printing press. When the average particle size is larger than 50 μm, or when the amount of the spherical particles is more than 40 parts by mass, the adhesion between papers is reduced, so that the occurrence of double feeding in the paper feeding unit can be prevented. The degree decreases.

  Among the spherical particles used in the present invention, examples of the inorganic pigment include light calcium carbonate, magnesium carbonate, and the like, and one or more of these are appropriately selected and used.

  Among the spherical particles used in the present invention, solid-type, hollow-type, and through-hole type organic pigments include polystyrene resins, styrene-acrylic copolymer resins, urea resins, melamine resins, and acrylic resins. , Vinylidene chloride-based resins, benzoguanamine-based resins, and the like, and one or more of them are appropriately selected and used. Moreover, you may use together and use an inorganic pigment and an organic pigment.

  The spherical particles used in the present invention are characterized in that they are blended in the undercoat layer, but can also be blended in the top coat layer as long as the desired quality is not deteriorated.

The undercoat coating layer of the coated paper according to the present invention is formed by coating on one side or both sides of the base paper and drying. For coating, roll coating, air knife coating, bar coating, blade coating, spray coating, curtain coating, die coating and the like can be employed. The coating amount is selected in the range of ² to 10 g / m ² per side of the base paper. The smoothness of the undercoat coating layer is preferably adjusted to a range of 30 to 500 seconds.

  When forming the top coat layer to be described in detail later, when adopting blade coating, if the smoothness of the undercoat layer exceeds 500 seconds, streaks or scratches may occur in the top coat layer. is there. However, if the smoothness of the undercoat coating layer is less than 500 seconds, streaks or scratches can be completely prevented.

The top coat layer of the coated paper according to the present invention has an average particle diameter in the range of 0.01 to 3.0 μm, preferably in the range of 0.01 to 1.0 μm, alone or in combination with an organic pigment or an inorganic pigment. In combination, the topcoat coating layer coating solution containing 1 to 20 parts by mass of the adhesive per 100 parts by mass of the pigment is applied to the surface of the undercoat coating layer formed on the base paper and dried. Formed by. For coating, roll coating, air knife coating, bar coating, blade coating, spray coating, curtain coating, die coating and the like can be employed. The coating amount of the topcoat coating layer is less than the coating amount of the undercoat coating layer described above, and is selected in the range of 0.5 to 8 g / m ² per side.

  The reason for defining the average particle diameter of the organic pigment and inorganic pigment contained in the top coat layer as described above is to obtain desired blank paper glossiness and air permeability. On the other hand, when the coating amount exceeds the above range, the air permeability increases and the air permeability may be inferior. On the other hand, when the coating amount is small, the target glossiness may not be obtained.

  Examples of the inorganic pigment used for the top coat layer include calcium carbonate, calcined kaolin, engineered kaolin, delaminated kaolin, talc, calcium sulfate, barium sulfate, aluminum hydroxide, satin white, titanium dioxide, zinc oxide, alumina, Examples thereof include magnesium carbonate, magnesium oxide, silica, magnesium aluminosilicate, calcium silicate bentonite, zeolite, sericite, and smectite. Examples of organic pigments include polystyrene resins, styrene-acrylic copolymer resins, urea resins, melamine resins, acrylic resins, vinylidene chloride resins, benzoguanamine resins, and organic pigments such as hollow and through-hole resins. it can. One or more of these can be appropriately selected and used. Furthermore, as a result of intensive studies on the expression of gloss, it has been found that it is particularly preferable to blend fine particles such as plastic pigments and binder pigments having a particle diameter of 500 nm or less. The amount of the fine particles is preferably 50% by mass or more of the top coat layer.

  As in the case of the above-described undercoat layer, the adhesive component of the topcoat layer includes conjugated diene polymer latex such as styrene-butadiene copolymer and methyl methacrylate-butadiene copolymer, and acrylic polymer. Examples thereof include latex and vinyl polymer latex such as ethylene-vinyl acetate copolymer. A water-soluble adhesive can also be used in combination. Examples of water-soluble adhesives include various starches such as oxidized starch, esterified starch and cold water soluble starch, proteins such as casein, soy protein and synthetic protein, cellulose derivatives such as carboxymethylcellulose and methylcellulose, polyvinyl alcohol and modified products thereof. Etc. can be exemplified. These 1 type (s) or 2 or more types can be used as an adhesive agent component of topcoat coating layer.

  The coating liquid used for the formation of the undercoat coating layer and the coating liquid used for the formation of the topcoat coating layer may be blue or purple dyes, colored pigments, fluorescent dyes, thickening agents as necessary. As appropriate, various auxiliary agents such as agents, water retention agents, antioxidants, anti-aging agents, conductivity-inducing agents, antifoaming agents, ultraviolet absorbers, dispersants, pH adjusters, mold release agents, water-resistant agents, water-repellent agents Can be blended.

  The coated paper coated with the coating liquid to form the top coat layer is subjected to a finishing process, and in this process, for example, a super calendar, a gloss calendar, a soft calendar, etc. can be used. Among these, it is preferable to employ a calendar provided with a hard resin roll.

In the present invention, the average particle diameter of the pigment component contained in each of the undercoat coating layer and the topcoat coating layer is specified, and the undercoat coating layer and the topcoat coating layer are provided on one side or both sides of the base paper. Unless a particularly high pressing force is adopted for the calendar, a coated paper for printing having a density of 1.10 g / cm ³ or less can be obtained by calendar finishing commonly used in the industry.

  If the coated paper according to the present invention has a stiffness of less than 14 cm, in a printing press or dry electrophotographic system, the paper is likely to stick to the roll of the fixing unit due to heat at the time of toner fixing, which may cause poor running. If the glossiness of the white paper on the surface is less than 45%, the gloss difference from the image area is large, and a high-quality image having the desired glossiness may not be obtained.

  The moisture of the coated paper according to the present invention is usually adjusted to a range of 3 to 10%. More preferably, it is 4 to 8% of range. When the water content cannot reach the range of 3 to 10%, the coated paper may be curled and stable printing cannot be performed.

Generation of wrinkles due to dampening water during printing when the basis weight of the coated paper according to the present invention is 35 to 80 g / m ² , preferably 45 to 75 g / m ² , and the basis weight is less than 35 g / m ^2. Becomes prominent. Moreover, as a result of earnestly examining the prevention of wrinkles due to dampening water during printing, the fiber orientation ratio of the base paper is preferably 1.00 to 1.50, more preferably adjusted to 1.00 to 1.40. By doing so, it was found that wrinkle generation can be prevented. Specific measures include adjustment of papermaking conditions such as jet / wire ratio and shaking conditions (especially using a Duo Shake method) in a paper machine, and drying conditions (draw during drying, Adjusting drying temperature etc.). If the fiber orientation ratio of the base paper is greater than 1.50, the CD stiffness of the coated paper becomes small, and wrinkles due to dampening water during printing may occur. Similarly, even when the fiber orientation ratio is measured from the surface of the coated paper, the fiber orientation ratio is preferably 1.00 to 1.50, more preferably 1.00 to 1.40.

  Regarding the pulp of the base paper, there is no particular limitation on the production method, type, etc., mechanical pulp such as KP, SGP, RGP, BCTMP, CTMP, waste paper pulp such as deinked pulp, or kefna, bamboo, straw, hemp It is also possible to use non-wood pulp such as non-wood pulp, organic synthetic fiber such as polyamide fiber, polyester fiber and polynosic fiber, and inorganic fiber such as glass fiber, ceramic fiber and carbon fiber. Further, chlorine-free pulp such as ECF pulp or TCF pulp is preferably used. Further, from the viewpoint of resource protection, it is preferable to use pulp obtained from so-called forest certified certified forest, planted tree or thinned wood chips.

  Moreover, a filler can be mix | blended with a base paper as needed. The filler in this case is not particularly limited, but various pigments generally used for fine paper, such as kaolin, calcined kaolin, calcium carbonate, calcium sulfate, barium sulfate, titanium dioxide, talc, zinc oxide, alumina, Organic substances such as mineral pigments such as magnesium carbonate, magnesium oxide, silica, white carbon, bentonite, zeolite, sericite, smectite, polystyrene resin, urea resin, melamine resin, acrylic resin, vinylidene chloride resin and their fine hollow particles Pigments.

  In addition to pulp fibers and fillers in the paper material, various anionic, nonionic, cationic or amphoteric yield improvers that have been used in the past as long as the desired effects of the present invention are not impaired. Various paper-making internal additives such as a drainage improver, a paper strength enhancer, and an internal additive sizing agent can be appropriately selected and used as necessary. Furthermore, internal additives for papermaking such as dyes, fluorescent brighteners, pH adjusters, antifoaming agents, pitch control agents, slime control agents and the like can be appropriately added depending on the use of the paper.

The papermaking method is not particularly limited. For example, an acidic papermaking method in which the papermaking pH is around 4.5, an alkaline filler such as calcium carbonate as a main component, and a papermaking pH of about 6 to a weakness of about 9 The present invention can be applied to all paper making methods such as an alkaline neutral paper making method, and the paper machine can be suitably used a long net paper machine, a twin wire paper machine, a round net paper machine, and a Yankee paper machine. The basis weight of the obtained base paper is preferably 30 to 75 g / m ^2.

  The coated paper obtained by the above method can be used not only as an offset printing paper but also as an image recording paper for non-impact printing methods such as an electrophotographic method and a thermal transfer method because of the high smoothness and high air permeability of the surface. I can do it.

  In the image recording, particularly in an electrophotographic system in which an image is formed with toner particles of about 5 to 7 μm, an extremely high quality image can be obtained by using the above-mentioned coated paper. For example, when an image is formed and evaluated using an electrophotographic printer based on a method in conformity with ISO-13660 draft standard QEA (Quality Engineering Associates, Inc.), the motor at a tile size of 40 μm is 10 GSV (Gray Scale). (Value) or less, the line ragedness (jaggedness) is 10 μm or less, and the brilliance (blurring degree) is 11 μm or less, and an extremely good image can be obtained.

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

Example 1
[Preparation of undercoat coating solution]
Engineered kaolin (trade name: Contour 1500, average particle diameter 0.46 μm, aspect ratio 59) as a flat pigment in an aqueous solution obtained by adding 0.1 part of sodium polyacrylate as a dispersant to 100 parts of engineered kaolin to be dispersed 100 parts of Imeris Co.) was added and dispersed with a Coreless disperser to prepare a pigment slurry. To this slurry, 4.0 parts of oxidized starch (trade name: Ace A, manufactured by Oji Cornstarch Co., Ltd.), styrene-butadiene copolymer latex (trade name: 2531-H, manufactured by JSR) 10 Part (both solid content conversion), an antifoaming agent and a dye were added as auxiliary agents, and finally a coating solution having a solid content concentration of 50% was prepared.

[Preparation of top coat solution]
As a pigment, 100 parts of slurry-like plastic pigment (trade name: POT 7099: particle size 60 nm, manufactured by Nippon Zeon Co., Ltd.), 2 parts of oxidized starch (trade name: Oji Ace A, manufactured by Oji Cornstarch Co., Ltd.), styrene-butadiene copolymer Latex (trade name: 2531-H, manufactured by JSR) 5 parts (all in terms of solid content), defoaming agent and dye added as an auxiliary agent, and finally a coating with a solid content concentration of 40% A liquid was prepared.

[Preparation of coated paper]
Fine base paper (basis weight 50 g / m) having a fiber orientation ratio of 1.30 and a density of 0.75 g / cm ³ by adjusting the ratio of the raw material discharge speed from the inlet / wire speed (hereinafter referred to as J / W). Paper ² ) was made. The undercoat coating solution was applied to both surfaces of the base paper using a blade coater so that the dry weight per side was 5 g / m ^2, and this was dried to provide an undercoat coating layer. Next, the top coat liquid is applied onto each undercoat layer using a blade coater so that the dry weight per side is 2 g / m ^2, and this is dried to provide an overcoat layer. It was. The coated paper thus obtained was passed through a super calender at a temperature of 35 ° C. and a linear pressure of 80 KN / m to obtain a coated paper having a tenacity of 1.00 g / cm ³ .

Example 2
A coated paper was obtained in the same manner as in Example 1 except that the basis weight of the base paper used in Example 1 was changed to 46 g / m ² and the coating amount of the undercoat coating solution was changed to 7 g / m ² .

Example 3
A coated paper was obtained in the same manner as in Example 1 except that the basis weight of the base paper used in Example 1 was changed to 54 g / m ² and the coating amount of the undercoat coating solution was changed to 3 g / m ² .

Example 4
A coated paper was obtained in the same manner as in Example 1 except that the fiber orientation ratio of the base paper used in Example 1 was changed to 1.50 by adjusting J / W.

Example 5
A coated paper was obtained in the same manner as in Example 1 except that the topcoat pigment used in Example 1 was changed to kaolin (trade name: Kaogros 0.4 μm, manufactured by Huber).

Example 6
In Example 1, a pigment having a particle diameter of 250 nm (trade name: S2577A: made by JSR) was used instead of a plastic pigment having a particle diameter of 60 nm (trade name: POT 7099: made by Nippon Zeon) as the pigment of the topcoat coating layer. A coated paper was obtained in the same manner as in Example 1 except that.

Example 7
A coated paper was obtained in the same manner as in Example 1 except that the coating amount of the topcoat coating layer was changed to 0.5 g / m ² and the basis weight of the base paper was changed to 53 g / m ² .

Example 8
In Example 1, the basis weight of the base paper is 48 g / m ² , the coating amount of the top coat layer is 3.0 g / m ² , the undercoat pigment is engineered kaolin (trade name: Contour Xtrem, average particle size 0. A coated paper was obtained in the same manner as in Example 1 except that the thickness was changed to 26 μm and the aspect ratio was 33 (made by Imeris Corporation).

Example 9
90 parts of engineered kaolin (trade name: Contour 1500, average particle size 0.46 μm, aspect ratio 59, manufactured by Imeris Co.) used in Example 1 and 10 spherical particles (light calcium carbonate of 10 μm particle size, manufactured by Yonesho Lime Industry) were used. Coated paper was obtained in the same manner as in Example 1 except that the part was changed to the part.

Comparative Example 1
Coating was performed in the same manner as in Example 1 except that the pigment component of the undercoat coating solution of Example 1 was changed to deramikaolin (trade name: CapimNP: average particle size 0.75 μm: aspect ratio 20, manufactured by Imeris Co.). Obtained paper.

Comparative Example 2
Coating was carried out in the same manner as in Example 1 except that the pigment component of the undercoat coating liquid of Example 1 was changed to kaolin (trade name: Capim DG: average particle diameter 0.6 μm: aspect ratio 11, manufactured by Imeris). Obtained paper.

Comparative Example 3
The same as in Example 1 except that the pigment component of the top coat liquid of Example 1 was changed to a plastic pigment (trade name: AE851) having a particle diameter of 1 μm instead of a plastic pigment (trade name: POT7099) having a particle diameter of 60 nm. Thus, a coated paper was obtained.

Quality evaluation of coated paper The quality of each coated paper obtained in Examples 1 to 9 and Comparative Examples 1 to 3 was evaluated by the following items. Evaluation was performed in an environment of 23 ° C. and 50 RH% unless otherwise specified. The results are shown in Tables 1 to 3.

[Measurement of average particle size of pigment by precipitation method]
The particle size distribution of the pigment was measured using a Sedigraph 5100 manufactured by Micromeritex, Inc., USA, and the average particle size corresponding to 50 cumulative mass% was determined. The pigment dispersion used for the measurement was prepared by adding a pigment slurry prepared by adding 0.05% of a dispersant (sodium polyacrylate) to a pigment with a 0.1% aqueous solution of a phosphate dispersant (nancarin). The pigment solid content concentration was diluted to 5%.

[Measurement of pigment aspect ratio and shape observation]
The image was magnified 15000 times with an electron microscope, and the aspect ratio was measured and the shape was observed.

[density]
The tension of the coated paper and the base paper after the calendar treatment was measured according to the provisions of ISO 534: 1988.

[Measurement of glossiness of coated paper]
In accordance with TAPPI test method: T 480 om-92, the glossiness was measured under the conditions of an incident angle and a light receiving angle of 75 degrees. Measuring instrument: Trade name GLOSS METER MODEL GM-26D (manufactured by Murakami Color Research Laboratory) was used.

[Measurement of air permeability of coated paper]
Measured with a Oken air permeability meter.

[Measurement of CD stiffness of paper]
In accordance with TAPPI T451, the transverse (CD) stiffness of the paper was measured with a Clark meter.

[Measurement of fiber orientation ratio]
As a fiber orientation measuring device, an ultrasonic propagation velocity measuring device (device type name SST: Sonic Sheet Tester, manufactured by Nomura Corporation) was used for measurement.

[Measurement of convexity on coated paper surface]
The projections on the surface of the coating layer were measured 100 times with an electron microscope, and converted into the number per square mm.

[Printing coated paper]
Printing was performed at a printing speed of 8000 sheets / hour using a printing ink (trade name: Values-G black S type, manufactured by Dainippon Ink & Chemicals, Inc.) with a Mitsubishi lithographic printing press (model: Diamond 4E4 type).

[Evaluation of runnability during printing]
Excellent: 0 times sticking to the blanket. There is no problem in practical use.
Good: Occurrence of sticking to the blanket 1 to 3 times. There is no problem in practical use.
Yes: 4-10 times sticking to blanket. There are practical problems.
Impossibility: At least 11 occurrences of sticking to the blanket. There is a problem in practical use, and it is remarkably inferior.

[Ink drying evaluation]
One hour after printing, high-quality paper was applied to the printed surface, and ink transfer was evaluated according to the following evaluation criteria.
Excellent: Ink transfer is not observed. There is no problem in practical use.
Good: Slight ink transfer is observed. There is no problem in practical use.
Yes: Ink transfer is frequently observed. There are practical problems.
Impossible: Ink transfer was noticeable. There is a problem in practical use, and it is remarkably inferior.

[Evaluate wrinkle generation state of sample after printing]
Excellent: Excellent without wrinkles.
Good: Some wrinkles are observed, but there is no practical problem.
Yes: Wrinkles are observed and there is a problem in practical use.
Impossibility: The occurrence of wrinkles is noticeable and there are practical problems.

When the coated paper according to the present invention is printed on a large offset printing press, there is no sticking to the printing cylinder or wrinkles, the ink drying property is fast, the printing workability is improved, and the blank paper glossiness is improved. It has a high basis weight of 80 g / m ² or less and is extremely useful in practice.

Claims (9)

In a coated paper in which two or more coating layers mainly composed of a pigment and an adhesive are provided on at least one side of the base paper, the following conditions (under 100 parts by weight of the total pigment in the undercoat coating layer in contact with the base paper: The coated paper contains 50 parts by mass or more of a flat pigment satisfying 1) and (2), and the coated paper has a Clark stiffness in the CD direction of 14 cm or more and a blank paper glossiness of 45% or more on the surface thereof. Coated paper characterized by:
(1) Average particle diameter measured by sedimentation method: 0.2 to 5.0 μm
(2) Aspect ratio (major axis / thickness): 25-120.   The coated paper according to claim 1, wherein the flat pigment is engineered kaolin.   The coated paper according to claim 1 or 2, wherein the air permeability of the coated paper is 7000 seconds or less.   The coated paper according to any one of claims 1 to 3, wherein the adhesive component of the undercoat coating layer is 5 to 30 parts by mass per 100 parts by mass of the pigment component contained in the undercoat coating layer.   The coated paper according to any one of claims 1 to 4, wherein a fiber orientation ratio of the base paper is 1.00 to 1.50.   The coated paper according to any one of claims 1 to 5, wherein the fiber orientation ratio measured from the surface of the coated paper is 1.00 to 1.50. Coated paper according to any one of the coated paper according to claim 6 basis weight of 35~80g / m ² of. The undercoat in the coating layer topcoat coating layer on, coated paper of any one of claims 1 to 7, the particle diameter 500nm or less fine particles contain 0.5 g / m ² or more.   The coated paper according to any one of claims 1 to 8, wherein the undercoat coating layer contains spherical particles having an average particle diameter of 1 to 50 µm.