JP2009007690A - Coated paper for printing and method for producing the same - Google Patents

Abstract

The present invention provides a coated paper for printing excellent in white paper glossiness, white paper surface properties, print gloss and printability, and a method for producing the same.
SOLUTION: At least one surface of a base paper has one or more pigment coating layers, and a surface layer formed on the pigment coating layer by a spray coating method, and the surface layer is a surface layer. It contains a plastic pigment having a total solid content of 25 to 90% by mass and is smoothed. The plastic pigment is preferably a hollow type. The surface layer preferably contains 5 to 70% by mass of a thermoplastic polymer latex having a glass transition temperature (Tg) of 40 ° C. or higher and lower than 80 ° C. with respect to the total solid content of the surface layer.
[Selection figure] None

Description

  The present invention relates to a coated paper for printing and a method for producing the same.

In general, coated paper for printing is manufactured by applying an aqueous coating composition containing pigment and adhesive as the main components on a base paper and drying it. The coating amount of the coating composition and the finish of the coated paper Depending on the method, it is classified into cast coated paper, art paper, coated paper, fine coated paper, and the like. 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, with the progress of visualization and colorization of printed matter, the appearance of coated paper for printing, such as glossiness and smoothness, is more important than ever.
The glossiness of the white paper of the coated paper for printing is highest in cast coated paper, and then decreases in the order of art paper, coated paper, and finely coated paper. Cast coated paper with the highest glossiness is manufactured with a cast coater having a mirror drum, but after applying a coating liquid containing a pigment and an adhesive as the main components on the base paper, it is in a wet plastic state. Since it is pressed against a heated mirror drum for a while, dried, and then released to give a high gloss finish, there is a problem that the production speed is considerably slower than that of general art paper and coated paper.

  In order to solve this problem, a coating solution using a resin latex having a specific glass transition temperature or a polymer latex having a specific monomer composition is applied on a base paper, and then pressed against a heated mirror drum after drying (patent) Documents 1 and 2) have been proposed. According to these methods, the production speed is improved as compared with general cast-coated paper, but it is still at a much lower level than the production speed of general art paper and coated paper.

In addition, as a method for obtaining high gloss paper, a coating liquid using a polymer latex having a specific glass transition temperature is applied to a base paper, dried, and pressure-bonded to a heating calendar above the glass transition temperature of the polymer latex. A method (see Patent Document 3), a method of coating a coating liquid containing a specific polymer latex and a specific release agent on a base paper, drying and high-temperature calendering (see Patent Document 4), specific There has been proposed a method (see Patent Document 5) in which a coating liquid containing kaolin and a hollow plastic pigment is coated on a base paper, dried, and subjected to thermal calendaring.
In addition, a coating liquid containing a specific amount of a specific hollow organic pigment is coated on a base paper, dried, and surface-finished with a super calender (see Patent Document 6), a coating containing plastic pigment and satin white A method of manufacturing by coating a liquid with a blade (see Patent Document 7), a method of coating a coating liquid containing a specific plastic pigment and a specific satin white on a base paper, drying and heating calendar processing (See Patent Document 8) and the like have also been proposed.
According to these methods, the production speed is fast and the productivity is excellent, but in any method, in order to obtain a glossiness as high as art paper, it is necessary to use a large amount of expensive raw materials, There is a problem that the manufacturing cost becomes high, and the present situation is that a high gloss level comparable to cast-coated paper cannot be obtained.

  Furthermore, as another method, a method of providing a coating layer made of a mixture of two or more thermoplastic synthetic resins having different minimum film forming temperatures on a base paper (see Patent Document 9), a pigment on a support. A coated paper for printing having a surface layer made of a thermoplastic polymer latex having a secondary transition temperature of 80 ° C. or higher on a pigment coating layer of a base material provided with a coating layer, wherein the surface layer comprises two layers A method in which a calendar treatment is performed at a temperature lower than or equal to the next transition temperature (see Patent Document 10), a support having a pigment-containing layer on at least one surface, an average particle size of 100 nm or less on the pigment-containing layer, and a secondary transition temperature A method in which a surface layer containing thermoplastic polymer latex particles of 80 ° C. or higher is provided, and the surface layer is not calendered (see Patent Document 11), a base in which a pigment coating layer is provided on a support On the pigment coating layer of the material. A method of providing a surface layer having a thermoplastic polymer latex having a temperature of 80 ° C. or higher and a surface sizing agent (see Patent Document 12), a coating paper for printing having a coating layer on a specific base paper, and a coating composition Although a method in which a specific amount of colloidal silica is blended in a product has been proposed (see Patent Document 13), further improvement is required in terms of blank paper glossiness, blank paper surface properties, print gloss, and printability. .

Japanese Patent Laid-Open No. 9-67772 Japanese Patent Laid-Open No. 10-96189 JP-A-56-68188 Japanese Patent Laid-Open No. 9-95897 JP-A-6-235194 Japanese Patent No. 3249212 Japanese Patent Laid-Open No. 9-256295 Japanese Patent Laid-Open No. 2-14098 JP 59-22683 A JP-A-3-167396 JP-A-8-13390 JP 2002-363848 A Japanese Patent Laid-Open No. 3-199491

  The present invention provides a coated paper for printing excellent in white paper glossiness, white paper surface properties, print gloss and printability, and a method for producing the same.

The printing coated paper and the method for producing the same according to the present invention include one or more pigment coating layers on at least one side of a base paper, and a surface layer formed on the pigment coating layer by a spray coating method. The surface layer contains 25 to 90% by mass of a plastic pigment of the total solid content of the surface layer, and is smoothed.
The white paper glossiness at an incident / light receiving angle of 75 degrees based on ISO 8254-1 (1999) is preferably 80 or more.
The white paper glossiness at an incident / light-receiving angle of 20 degrees based on ISO 8254-3 (2004) is preferably 8 or more.
The plastic pigment is preferably a hollow type.
The surface layer preferably contains 5 to 70% by mass of a thermoplastic polymer latex having a glass transition temperature (Tg) of 40 ° C. or higher and lower than 80 ° C. with respect to the total solid content of the surface layer.
The coating amount after drying of the surface layer is preferably 0.1 to 3.0 g / m ² per side.
On at least one side of the continuously running base paper,
(A) a step of forming one or more pigment coating layers,
(B) A plastic pigment occupying 25 to 90% by mass of the total solid content of the coating liquid is contained on the pigment coating layer, the viscosity is 5 to 800 mPa · s, the surface tension is 55 mN / m or less, and the following formula is used. A step of applying a surface layer coating solution having a Tan δ of 1 to 100 by a spray coating method and drying,
Tanδ = G ″ / G ′
G ′, G ″: Viscoelasticity measuring machine DAR-100 (manufactured by Jusco International Co., Ltd.), using a cone and plate (cone diameter 40 mm, angle 1 degree) as a measuring jig, measuring temperature 25 ° C., The measurement result of the elastic term and the viscosity term of the coating liquid performed at an oscillation mode frequency of 1 Hz and a stress of 6 Pa is shown.
(C) a step of smoothing the dried surface layer,
It is characterized by comprising.
The spray coating method is preferably a one-fluid spray.
It is preferable that the PPS smoothness measured by ISO8791-4 of the pigment coating layer formed in the step (a) immediately before the step (b) is 3.8 μm or less.
It is preferable that the pigment coating layer formed in the step (a) is smoothed immediately before the step (b).
It is preferable that at least one or all layers of the pigment coating layer in the step (a) are formed on the base paper by a blade coater.
The pigment coating layer formed in step (a) immediately before step (b) preferably satisfies at least one of the following conditions (1) to (3).
(1) The average particle diameter measured by the precipitation method of all pigments is 1.0 μm or less, and the ratio of pigments having a particle diameter exceeding 2.0 μm is 10% by mass or less.
(2) The delaminated kaolin specified below is contained in the total pigment in an amount of 10 to 100% by mass.
Delaminated kaolin:
The average particle size d50 ₁ as measured by light scattering method is in the range of 2.0～5.0Myuemu, the average particle diameter d50 ₂ as measured by sedimentation method is in the range of 0.30～0.55Myuemu, moreover , an average particle size d50 ₁ as the average particle diameter d50 ₂ ratio _(d50 1 / d50 ₂₎ is delaminated kaolin is 4 or more.
(3) 3 to 20% by mass of satin white having an average particle diameter of 1.5 μm or less measured by a precipitation method is contained in all pigments.

  The coated paper for printing according to the present invention is excellent in white paper glossiness, white paper surface properties, print gloss and printability.

  From the actual situation as described above, the inventors of the present invention have conducted intensive studies to obtain a coated paper for printing excellent in both quality and productivity with respect to the coated paper for printing. As a result, at least one side of the base paper has a pigment coating layer, and the surface layer is provided on the pigment coating layer by providing a surface layer containing a specific amount of a specific plastic pigment by a spray coating method. As a result, the present inventors have found that a coated paper for printing excellent in white paper glossiness, white paper surface properties, print gloss and printability can be obtained without impairing printability practically compared to the case where the printability is not obtained. It came to do.

Details of the present invention will be described below.
The most important point in the present invention is that a specific surface layer is provided by a spray coating method, which makes it possible to provide uniform and favorable ink absorbency in printing such as offset printing and gravure printing. It became.

  The spray coating method used for coating the surface layer in the present invention is a kind of coating method called a contour coating method, and by providing the surface layer defined in the present invention on the pigment coating layer, The coating layer thickness of the surface layer becomes extremely uniform, and as a result, the ink absorbability during printing can be made uniform. Furthermore, by including a plastic pigment in the surface layer, it is possible to improve not only the white paper gloss but also the print gloss. In addition, since the white paper glossiness measured at a general incident angle / light receiving angle of 75 degrees is extremely high and the white paper glossiness measured at an incident angle / light reception angle of 20 degrees is also high, the conventional cast paper is used. Has comparable white paper gloss and texture.

  In the present invention, by providing a surface layer mainly composed of a resin on the pigment coating layer, very excellent white paper gloss is exhibited. Specifically, since the specific plastic pigment is contained in the surface layer, it is possible to extremely increase the white paper gloss of the coated paper in the smoothing step after coating and drying. The content of the plastic pigment in the surface layer is 25 to 90% by mass with respect to the total solid content of the surface layer, and the average particle size of the plastic pigment is 0.15 to 2.0 μm. is necessary. When the content of the plastic pigment is less than 25% by mass or when the average particle size is less than 0.15 μm, the effect of improving the white paper gloss of the obtained coated paper is diminished, the printability is poor, and the other content is When the amount exceeds 90% by mass, or when the average particle size is larger than 2.0 μm, the plastic pigment in the surface layer falls off in the coating / drying / smoothing step or the printing step. It becomes easy to deteriorate printing workability. The lower limit of the content of the plastic pigment in the surface layer is preferably 30% by mass or more and the upper limit is preferably less than 70% by mass with respect to the total solid content of the surface layer. Further, the lower limit of the average particle diameter of the plastic pigment in the surface layer is more preferably 0.2 μm or more, and the upper limit is more preferably 1.5 μm or less.

  As the plastic pigment contained in the surface layer, various types such as a solid type, a bowl type, and a hollow type can be used. Among them, the hollow type is most preferably used because it has the highest gloss expression.

  Since the coated paper obtained by the present invention contains a plastic pigment in the surface layer, it is very excellent in the effect of increasing the white paper gloss by a glossing treatment such as a calendar, and has a white paper gloss comparable to cast paper. . As the white paper gloss of the coated paper after the smoothing treatment, the white paper glossiness at an incident / light receiving angle of 75 degrees based on ISO 8254-1 (1999) is 80 or more, and the incident / light receiving angle based on ISO 8254-3 (2004). A preferred embodiment is a 20 degree white paper glossiness of 8 or higher, a quality that is easily achieved by the technique of the present invention. The 75 degree gloss is more preferably 85 or more, and the 20 degree gloss is more preferably 10 or more.

  The surface layer is applied by a spray coating method, and the viscosity of the coating solution needs to be 5 to 800 mPa · s. In the present invention, in the spray coating method that is essential for the formation of the surface layer, the coating liquid formed into droplets is applied by landing on the traveling substrate, but the coating liquid viscosity is too high The coating liquid formed into droplets is difficult to spread on the pigment coating layer, and a uniform coating layer cannot be obtained. On the other hand, if the viscosity of the coating solution is too low, the penetration of the surface layer coating solution into the pigment coating layer becomes significant, and even if the coating amount is increased, the blank paper quality and the printing quality are simultaneously satisfied. The desired coated paper of the present invention cannot be obtained. For this reason, it is necessary to set it as 5-800 mPa * s as a viscosity of the coating liquid which forms a surface layer. In addition, as an upper limit of a viscosity, 500 mPa * s or less is more preferable, and 300 mPa * s or less is still more preferable. Moreover, as a lower limit of a viscosity, 10 mPa * s or more is more preferable, and 15 mPa * s or more is a more preferable range.

  It is preferable that the surface layer contains a thermoplastic polymer latex having a glass transition temperature (Tg) of 40 ° C. or higher and lower than 80 ° C. in an amount of 5 to 70% by mass with respect to 100% by mass of the total solid content of the surface layer. It is. In the present invention, the plastic pigment essential as a component in the surface layer has a Tg of around 100 ° C., and does not melt during drying in a normal coated paper production process, and maintains the original particle shape. For this reason, it has the outstanding gloss imparting effect at the time of the smoothing process after coating. Moreover, in order to make the adhesive strength of the surface layer more preferable, it is preferable to use a binder component together. As a result of investigations by the inventors, a thermoplastic polymer latex having a Tg of 40 ° C. or more and less than 80 ° C. By including 5 to 70% by mass with respect to the total solid content of the surface layer, it became possible to obtain the target white paper appearance and excellent print quality.

  The thermoplastic polymer latex used in the surface layer of the present invention is a polymer or copolymer emulsion exhibiting thermoplasticity. There is no particular limitation on the type of monomer constituting the thermoplastic polymer latex and the production method, and it may be adjusted so that the glass transition temperature is in the range of 40 ° C. or more and less than 80 ° C.

  If the glass transition temperature of the thermoplastic polymer latex is in the range of 40 ° C. or more and less than 80 ° C., the surface layer can be attached to the calender roll when calendering, and there is no problem in practice, and offset printing, gravure printing, etc. In this printing, the absorption of printing ink is good and there is no problem of poor ink drying. In addition, the surface strength of the obtained coated paper for printing is also good, and there is no risk of problems related to surface strength such as picking and blanket piling in printing such as offset printing and gravure printing, and ink landing Unevenness is not a problem for practical use.

  Examples of the thermoplastic polymer latex used in the present invention include aliphatic conjugated diene monomers such as 1,3-butadiene and 2-methyl-1,3-butadiene, and aromatic vinyl such as styrene and α-methylstyrene. Monomers, ethylenically unsaturated acid monomers such as acrylic acid, methacrylic acid, itaconic acid, fumaric acid, and maleic acid, unsaturated carboxylic acid esters such as methyl acrylate and ethyl acrylate, and ethylenically unsaturated monomers such as acrylonitrile and methacrylonitrile. Examples thereof include polymers obtained by polymerizing amides of unsaturated carboxylic acids such as saturated nitrile compounds, acrylamide and methacrylamide, and derivatives thereof. The thermoplastic polymer latex of the present invention may be a copolymer using two or more kinds of monomers in combination, if necessary, or may be a substituted derivative of these polymers or copolymers. . Examples of substituted derivatives include carboxylated derivatives.

  The amount of the thermoplastic polymer latex having a glass transition temperature of 40 ° C. or higher and lower than 80 ° C. used in the present invention is preferably 5 to 70% by mass with respect to the total solid content of the surface layer, and is applied for printing. From the viewpoint of the balance between paper strength and print quality, the amount of the thermoplastic polymer latex used is more preferably 10% by mass or more as the lower limit and 60% by mass or less as the upper limit.

  In the present invention, it is preferable to use a thermoplastic polymer latex having a glass transition temperature (Tg) of 40 ° C. or higher and lower than 80 ° C. as a component of the surface layer. It is also possible to use a thermoplastic polymer latex having a temperature of less than 40 ° C. and / or 80 ° C. or higher.

  Further, the average particle diameter of the thermoplastic polymer latex used in the present invention is not particularly limited, but it is 60 nm as the lower limit of the average particle diameter in terms of coating liquid covering property and white paper glossiness. As described above, the upper limit is preferably 400 nm or less, the lower limit is preferably 100 nm or more, and the upper limit is more preferably 380 nm or less.

  The average particle size of the plastic pigment and the thermoplastic polymer latex was determined by taking a photograph of a sample containing the plastic pigment or the thermoplastic polymer latex with a transmission electron microscope at a magnification of 50,000 times, and from the obtained micrograph. The particle diameters of about 200 particles were measured and determined by number average.

  When the average particle diameter of the thermoplastic polymer latex is in the range of 60 to 400 nm, a coated paper for printing having a more excellent blank paper gloss, white paper surface, print gloss and printability (particularly ink inking property) is obtained. be able to.

  In addition, it is possible to use a binder other than the thermoplastic polymer latex in the surface layer. For example, when using starch or the like, it is used because the decrease in gloss and smoothness of white paper of the resulting coated paper is remarkable. Care must be taken with respect to the type and amount of binder used so as not to interfere with the desired effects of the present invention.

  When the surface tension of the surface layer coating liquid is 55 mN / m or less, it is preferable because the coating liquid spreads more uniformly on the pigment coating layer and a good coating surface can be obtained compared to the case where it is not. . The upper limit value of the coating liquid surface tension is more preferably 37 mN / m or less, and even more preferably 32 mN / m or less. The lower limit of the surface tension is not particularly limited. However, if the amount of the surfactant to be used is increased, problems such as background staining may occur during printing, and therefore, practically 20 mN / m or more is preferable. In addition, the surface tension said by this invention refers to the static surface tension measured by the Wilhelmy plate method etc.

  Although it is preferable that the surface tension of the surface layer coating liquid be in the above specific range, the method for adjusting the surface tension includes the use of a surfactant. The surfactant used in the present invention is not particularly limited, and for example, sulfosuccinic acid-based, ethylene glycol-based, fluorine-based, and silicon-based surfactants can be used, and the ionicity of the surfactant is not limited. Any of anion type, nonion type, and cation type can be used. If the surface tension of the coating liquid is within the desired range of the present invention, the amount of the surfactant used is not particularly limited, but if the amount added is extremely small, the surface tension is too high and the coating stability is poor, while the other addition If the amount is too large, the printability deteriorates when the coated paper is printed. Therefore, generally about 0.01 to 3.0% by mass with respect to the total solid content of the surface layer is used, and 0.05 to 2 0.0 mass% is the range used more suitably.

  In order to suppress the penetration of the surface layer coating solution into the pigment coating layer with respect to the pigment coating layer coating solution in contact with the surface layer, for example, alkyl ketene dimer type, alkenyl succinic anhydride type, styrene-acrylic Substances that impart hydrophobicity such as sizing agents such as sizing agents, higher fatty acid sizing agents, petroleum resin sizing agents, and rosin sizing agents, and water repellents may be added. However, if the hydrophobicity is too strong, the surface layer coating solution may not be fixed on the pigment coating layer, or the surface strength of the resulting coated paper may be extremely reduced. The amount of the hydrophobicity-imparting substance added to the coating liquid that forms the pigment coating layer in contact with the layer is preferably 2.0% by mass or less based on the total solid content of the pigment coating layer. .

  In the present invention, the content of a natural polysaccharide thickener such as carboxymethylcellulose and / or a synthetic thickener such as an alkali swelling type is 2.0 mass relative to 100 mass% of the total solid content of the surface layer. % Or less is preferable. The mixture of the plastic pigment used in the present invention and the thermoplastic polymer latex having a specific Tg generally has a low viscosity, and since the effect is exhibited with a small amount of coating, the concentration of the coating liquid is low. Because of this tendency, it is of course possible to use a thickener together if necessary, but natural polysaccharide thickeners such as carboxymethylcellulose and / or alkali swelling type that are generally used as thickeners. When a large amount of a synthetic thickener such as the above is used, there is a case where the resulting coated paper is remarkably deteriorated in white paper gloss and the like, and it is difficult to obtain the desired effect of the present invention. For this reason, as content of natural polysaccharide type thickeners, such as carboxymethylcellulose, and / or synthetic thickeners, such as an alkali swelling type, it is 2.0 mass% with respect to 100 mass% of total solid of a surface layer. The following is preferable. The lower limit of the content is not particularly limited, and even if it is 0% by mass, there is no problem. On the other hand, the upper limit of the content is more preferably 1.5% by mass or less, and still more preferably 1.0% by mass or less. The natural polysaccharide thickeners referred to in the present invention are cellulose derivatives such as carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, methyl cellulose, gums such as guar gum, gellan gum, locust bean gum, tara gum, xanthan gum, casein and It refers to substances that are naturally produced such as salts thereof, alginic acid and the like and derivatives thereof. Synthetic thickeners such as alkali swelling type are acrylic resins such as polyacrylic acid, sodium polyacrylate, acrylic acid / maleic acid copolymer salt, acrylic acid / sulfonic acid monomer copolymer salt, It refers to a polymer having a molecular weight of about 50,000 to 10,000,000 obtained by chemical synthesis, such as urethane resin and polyethylene oxide.

  The surface layer coating solution applied by spray coating spreads on the pigment coating layer due to inertial force after the droplets land on the running substrate, but this is due to the elasticity of the coating solution. The elastic recovery force tends to inhibit the spread of the droplets. As a result of investigations by the inventors, as a physical property of a coating liquid applied by a spray coating method, Tanδ which is an elastic / viscous ratio is used, and Tanδ is set to a specific range, so that a more uniform coating surface can be obtained. It turned out to be obtained.

That is, when Tan δ calculated by the following formula (1) of the surface layer coating solution applied by spray coating is 1 to 100, a better coated surface is obtained as compared to the case where it is not. Since it can be obtained, it is a preferred form in the present invention.
Tanδ = G ″ / G ′ (1)
Here, G ′: Elastic term of coating liquid G ″: Viscosity term of coating liquid G ′, G ″ Measuring conditions: Viscoelasticity measuring machine DAR-100 (manufactured by Jusco International Co., Ltd.) A cone and plate (cone diameter 40 mm, angle 1 degree) was used as a measurement jig, measurement temperature 25 ° C., oscillation mode frequency 1 Hz, stress 6 Pa. Tan δ is measured with a viscoelasticity measuring device that can be measured under the same measurement conditions, and if the accuracy is equal to or higher than DAR-100, a viscoelasticity measuring device other than DAR-100 used for the measurement in the present invention can also be used. It can be used.

  The Tan δ can be adjusted by adjusting the concentration of the surface layer coating solution, the type / amount of the adhesive used, and the type / amount of the thickener. The upper limit value of Tan δ is more preferably 50 or less, and further preferably 20 or less. Further, the lower limit value of Tan δ is more preferably 2 or more.

  In the present invention, an aqueous coating solution containing a plastic pigment having a specific average particle diameter can be applied and dried to form a surface layer, but as long as the effect is not impaired, as necessary. Thermoplastic polymer latex other than the above, various starches such as oxidized starch and esterified starch, synthetic resin adhesives such as polyvinyl alcohol, proteins such as casein, soy protein, synthetic protein, cellulose such as carboxycellulose and methylcellulose Derivatives and the like can be used in combination. In addition, pigments, dispersants, thickeners, lubricants, antifoams that are commonly used in the preparation of coated paper for printing to adjust whiteness, ink acceptability, blocking resistance, viscosity, fluidity, etc. Various auxiliary agents such as a colorant, a colorant, a dye, an antistatic agent, and an antiseptic can be added as appropriate.

  In particular, a lubricant is preferably added to improve the long-term continuous operability in the calendar process. Examples of the lubricant include fatty acids such as stearic acid and oleic acid and ammonium salts and metal salts thereof, hydrocarbons such as polyethylene emulsion, higher alcohols such as cetyl alcohol and stearyl alcohol, and various surfactants such as fluorine-containing surfactants. , Funnel oil, lecithin, fluorine-based polymers such as tetrafluoroethylene polymer and ethylene-tetrafluoroethylene polymer.

Further, preferably per side 0.1 to 3.0 g / ^{m 2} for coating amount after drying of the surface layer, 0.3~2.5g / ^{m 2} is more preferable. If it is the range of 0.1-3.0 g / m < ² >, the target white paper glossiness, white paper surface property, and printing gloss will be obtained, and the coated paper for printing excellent in printability can be obtained.

  As a spray coating method used for coating the surface layer in the present invention, a one-fluid method and a multi-flow-pair spray can be used. For example, two fluids of a coating solution and air are used. It is preferable to use a one-fluid type spray rather than a multi-fluid spray method such as a two-fluid spray method because of the uniformity of the obtained coating surface.

  In the present invention, the surface layer is provided by a spray coating method, but the coating method is not limited in the pigment coating layer adjacent to the surface layer.

In the present invention, there is no particular limitation on the coating apparatus for the aqueous coating liquid mainly containing a pigment and an adhesive, which is used when the pigment coating layer is provided, and is a tray generally used in the industry. Ring, flexible, roll application, fountain application, short dwell and other bevel type and vent type blade coaters, air knife coaters, bar coaters, rod blade coaters, champ flex coaters, gate roll coaters, gravure coaters, spray coaters, etc. Engineering equipment can be used as appropriate. Above all, when a blade coater is used, a surface layer with high smoothness can be obtained, and a coated paper for printing excellent in blank paper glossiness, blank paper surface properties, printing gloss and printability, particularly in ink unevenness can be obtained. At the same time, since the coating speed is relatively fast, it can be produced efficiently, which is preferable. Of course, these devices may be on-machine or off-machine. The pigment coating layer may be one layer or two or more layers.
As a method for drying the wet coating layer, for example, various methods such as steam drying, gas heater drying, electric heater drying, infrared heater drying and the like can be adopted.

  When the PPS smoothness measured by ISO 8791-4 of the pigment coating layer formed on the base paper before the surface layer is formed by the spray coating method is 3.8 μm or less, compared to the case where it is not And since it is excellent in the blank paper glossiness and smoothness of the coated paper finally obtained, it is a preferable form. The PPS smoothness after forming the pigment coating layer is more preferably 3.5 μm or less, more preferably 3.0 μm or less, and particularly preferably 2.8 μm or less. In order to obtain a pigment coating layer having a PPS smoothness of 3.8 μm or less, a method using a specific pigment described later, more preferably using a specific pigment described later, and forming a pigment coating layer with a blade coater. The method of forming, the method of smoothing the pigment coating layer formed using the general pigment, etc. can be considered.

It is preferable that the surface of the base paper in contact with the surface layer has a pigment coating layer satisfying at least one selected from the following conditions, since the glossiness and smoothness of the coated paper for printing can be improved.
(1) The average particle diameter measured by the precipitation method of all pigments is 1.0 μm or less, and the ratio of pigments having a particle diameter exceeding 2.0 μm is 10% by mass or less.
(2) The delaminated kaolin specified below is contained in the total pigment in an amount of 10 to 100% by mass.
Delaminated kaolin:
The average particle size d50 ₁ as measured by light scattering method is in the range of 2.0～5.0Myuemu, the average particle diameter d50 ₂ as measured by sedimentation method is in the range of 0.30～0.55Myuemu, moreover , an average particle size d50 ₁ and an average particle diameter d50 ₂ ratio _(d50 1 / d50 ₂₎ is delaminated kaolin is 4 or more.
(3) 3 to 20% by mass of satin white having an average particle diameter of 1.5 μm or less measured by a precipitation method is contained in all pigments.
It is preferable to satisfy at least one of the above conditions (1) to (3) because the smoothness of the pigment coating layer on the base paper can be improved as compared to the case where it is not.

  For example, in (1), since the surface of the obtained pigment coating layer is occupied by fine pigments, the smoothness of the pigment coating layer is improved as compared to the case where it is not. When the average particle diameter of all the pigments exceeds 1.0 μm, or when the ratio of the pigments having a particle diameter exceeding 2.0 μm is more than 10% by mass even if the average particle diameter of all the pigments is 1.0 μm or less, the present invention In some cases, it is difficult to obtain preferable smoothness. The ratio of the pigment having a particle diameter exceeding 2.0 μm is more preferably 7% by mass or less, and more preferably 5% by mass or less.

The above (2) uses a specific delaminated kaolin. The shape characteristic of a flat particle such as delaminated kaolin can be defined by the ratio (aspect ratio) of the major axis d to the thickness t. In the present invention, the shape characteristic of delaminated kaolin the average particle size d50 ₁ due to scattering method, is defined by the average particle diameter d50 ₂ by sedimentation method.
In the measurement of the average particle size d50 ₁ by light scattering method, the diameters are measured all the individual particles are regarded as spherical particles. Meanwhile, the average particle size d50 ₂ measured by sedimentation method, is measured for particle shape influences the sedimentation properties, shape as the flat plate-like or flat precipitated slow particles, apparently, as the diameter of small particles . Therefore, as the particle aspect ratio of the large average particle diameter d50 ₁ and the ratio of the average particle diameter d50 ₂ by sedimentation method using a light scattering method _(d50 1 / d50 ₂₎ it is considered to increase.
In the present invention, a laser diffraction particle size distribution analyzer SALD-2000 (manufactured by Shimadzu Corporation) is used for measurement of the average particle size by the light scattering method, and a Cedi graph is used for measurement of the average particle size by the precipitation method. 5100 (manufactured by Micromeritics, USA) was used.
In the present invention, d50 ₁ of delaminated kaolin to be contained in the pigment coating layer is in the range of 2.0～5.0Myuemu, preferably in the range of 2.2～4.7Myuemu, the d50 ₂ 0. It is in the range of 30 to 0.55 μm, preferably 0.35 to 0.50 μm. The ratio of d50 ₁ and d50 ₂ , d50 ₁ / d50 _2, is 4 or more, preferably 5 or more.
Incidentally, delaminated d50 ₁ and d50 ₂ kaolin to be contained in the pigment coating layer is, when it is less than each less than 2.0μm and 0.30μm, it delaminated kaolin in coated liquid, the base paper Therefore, it becomes difficult to form a coating layer with high smoothness. Moreover, it is difficult to form a coating layer with high smoothness even when d50 ₁ and d50 ₂ exceed 5.0 μm and 0.55 μm, respectively. Even when d50 ₁ / d50 ₂ is less than 4, since the flatness (flatness) of the pigment is low, it is excessively permeated into the base paper and it becomes difficult to form a coating layer with high smoothness. There is a fear.

  The reason (3) is that the surface of the pigment coating layer is smoothed by adding satin white to the pigment coating layer, and the average particle size of the satin white is 1.5 μm or less. preferable. When the average particle diameter exceeds 1.5 μm or the content is less than 3% by mass, the smoothing effect due to the addition of satin white may be difficult to develop, and the blending amount exceeds 20% by mass. In many cases, the coating layer strength may be reduced.

  The pigment used in the aqueous coating liquid for a pigment coating layer of the present invention is preferably a pigment satisfying at least one selected from the above (1) to (3), but does not impair the effects of the present invention. Pigments that do not meet the conditions to a certain extent, such as kaolin, talc, clay, calcined kaolin, heavy calcium carbonate, light calcium carbonate, titanium dioxide, satin white, calcium sulfite, gypsum, barium sulfate, white carbon, amorphous In addition to inorganic pigments such as silica, diatomaceous earth, magnesium carbonate, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, zinc hydroxide, zinc oxide, magnesium oxide, bentonite, sericite, urea formalin resin fine particles, fine hollow particles, etc. Organic pigments and other pigments known for general coated paper are used alone or in combination Door can be.

  The adhesive used in the pigment coating layer is not particularly limited. For example, proteins such as casein and soy protein, conjugated diene series of styrene-butadiene copolymer and methyl methacrylate-butadiene copolymer Polymeric latex, acrylic polymer latex, vinyl polymer latex such as vinyl polymer such as ethylene-vinyl acetate copolymer, or these various polymers with functional group-containing monomers such as carboxyl groups, Functional group-modified alkali-soluble or alkali-insoluble polymer latex, polyvinyl alcohol, olefin-maleic anhydride resin, melamine resin and other synthetic resin adhesives, positive starch, oxidized starch, esterified starch, etc. Cellulose such as starches, carboxymethylcellulose, hydroxymethylcellulose Conductors, etc., an adhesive known as a general coated paper can be used alone or in combination. In addition, the usage-amount of the adhesive agent in a pigment coating layer is 5-50 mass parts with respect to 100 mass parts of pigments, Preferably it is about 10-30 mass parts.

  Further, in the aqueous coating liquid for pigment coating layer used in the present invention, a blue or purple dye or colored pigment, a fluorescent dye, a thickener, a water retention agent, as long as the effect of the present invention is not hindered. Various auxiliary agents such as an antioxidant, an anti-aging agent, a conductive treatment agent, an antifoaming agent, an ultraviolet absorber, a dispersant, a pH adjuster, a mold release agent, a water-resistant agent, and a water repellent can be appropriately blended. .

  Even if the base paper surface in contact with the surface layer uses a base paper having a pigment coating layer subjected to the smoothing process described later, the blank paper gloss and smoothness of the finally obtained coated paper can be improved. It is a preferred form.

  The coated paper for printing of the present invention is a pigment after the surface layer is formed or before spray coating, if necessary, in consideration of the blank paper quality, print quality and printability of the resulting coated paper for printing. Also for the coating layer, it is necessary to perform a smoothing process with various calendar devices. Examples of the calendar device that can be used include a calendar device that performs gloss finishing such as a hard nip calendar, a super calendar, a soft calendar, and a gloss calendar. Further, as the calender finishing conditions, the temperature of the rigid roll, the calender pressure, the number of nips, the roll speed, the paper moisture before the calender, and the like are appropriately adjusted according to the required quality. There are two types of calendar devices, an off-type that is separate from the coater and an on-type that is integrated with the coater. The material of the calendar apparatus to be used is a roll which is mirror-finished with a metal or a hard chrome plating on the surface of a rigid roll. As the elastic roll, a roll obtained by molding a resin roll such as urethane resin, epoxy resin, polyamide resin, phenol resin, polyacrylate resin, or the like, cotton, nylon, asbestos, aramid fiber, or the like is appropriately used. Of course, it is also possible to use a suitable combination of a water coating device, an electrostatic humidifier, a steam humidifier, and the like for humidity control and humidification of the coated paper after finishing with a calendar.

  Next, the base paper used in the present invention will be described. The base paper used for the coated paper for printing of the present invention is not particularly limited, and the following materials are appropriately selected and used as long as the desired effects of the present invention are not hindered.

  Examples of the pulp include generally used bleached chemical pulps such as LBKP and NBKP, ground wood pulp (GP), pressurized ground wood pulp (PGW), refined ground wood pulp (RGP), and thermomechanical pulp (TMP). Pulp, deinked waste paper pulp (DIP), waste paper, and the like are appropriately mixed and used. Moreover, 1 type, or 2 or more types, such as a pulp fiber obtained from non-wood fiber raw materials, such as kenaf, a synthetic pulp, an inorganic fiber, can also be mix | blended with a base paper. Mechanical pulp and DIP can be used after being bleached if necessary, and the degree of bleaching can be arbitrarily performed. For bleaching pulp, it is preferable to use a bleaching process that does not use molecular chlorine such as chlorine gas or chlorine compounds such as chlorine dioxide from the viewpoint of environmental conservation. Pulp that has undergone such bleaching process is used. Examples thereof include ECF pulp and TCF pulp.

  Examples of the filler internally added to the base paper include heavy calcium carbonate, light calcium carbonate, calcium sulfite, gypsum, talc, kaolin, clay, calcined kaolin, white carbon, amorphous silica, delaminated kaolin, diatomaceous earth, carbonic acid. Examples include inorganic pigments such as magnesium, titanium dioxide, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, and zinc hydroxide, and organic pigments such as urea formalin resin fine particles and fine hollow particles, and are included in waste paper and waste paper. The filler can also be reused. Two or more fillers can be used in combination. The blending amount of the filler is generally added so that the paper (base paper) ash content is in the range of 3 to 20% by mass.

  In addition to the pulp and filler, the base paper is exemplified by an internally added sizing agent, anionic, nonionic, cationic or amphoteric yield improver, freeness improver, paper strength enhancer, bulkiness agent and the like. Various types of internal additive for papermaking can be added as necessary. Specific examples of the internally added sizing agent include alkyl ketene dimer, alkenyl succinic anhydride, styrene-acrylic, higher fatty acid, petroleum resin sizing agent, rosin sizing agent and the like. Specific examples of yield improvers, drainage improvers, and paper strength enhancers include, for example, polyvalent metal compounds such as aluminum (specifically, sulfate bands, aluminum chloride, sodium aluminate, basic aluminum compounds). Etc.), various starches, polyacrylamide, urea resin, polyamide / polyamine resin, polyethyleneimine, polyamine, polyvinyl alcohol, polyethylene oxide and the like. Specific examples of bulking agents include higher alcohol ethylene oxide adducts, higher alcohol propylene oxide adducts, higher alcohol butylene oxide adducts, nonionic surfactants such as polyhydric alcohol and fatty acid ester compounds, fats Group polyamidoamines, polyalkylene glycols and the like.

In general, the basis weight of the base paper used for the printing coated paper of the present invention is appropriately adjusted within a range of about 30 to 450 g / m ² . Moreover, the papermaking conditions of the base paper are not particularly limited. As the paper machine, for example, a commercial paper machine such as a long paper machine, a gap former paper machine, a circular paper machine, or a short paper machine can be selected and used as appropriate according to the purpose. . The papermaking method may be any method such as acidic papermaking, neutral papermaking, or weak alkaline papermaking. However, in recent years, since paper preservation is required, base paper made by neutral papermaking is preferred. In addition, in order to improve the surface strength, size-pressing a surface-size solution such as starch, polyvinyl alcohol, polyacrylamide, etc., and to improve the surface smoothness of the base paper, the surface-size solution is used for the pigment coating layer. You may use the surface size liquid which mix | blended the pigment used for an aqueous coating liquid.

The aqueous coating liquid for pigment coating layer composed of the above materials is generally prepared to a solid content concentration of about 20 to 70% by mass, and 5 to 25 g / m per side by dry weight on at least one side of the base paper. ² , More preferably, the pigment coating layer is formed by coating and drying so as to be about 7 to ²⁰ g / m ² .

  Next, the present invention will be specifically described with reference to examples. However, the present invention is not limited to these examples. Unless otherwise specified, “parts” and “%” in the examples represent “solid mass parts” and “solid mass%”, respectively.

  The viscosity, surface tension, Tan δ, and quality of the base paper and coated paper were evaluated by the following methods.

(viscosity)
The B type viscosity measured under the condition of 60 rpm with a B type viscometer (manufactured by Tokyo Keiki Co., Ltd., model: BM) was defined as the viscosity of the coating liquid.

(surface tension)
The surface tension measured with a Wilhelmy plate type surface tension meter (manufactured by Kyowa Interface Science Co., Ltd., model: CBVP-Z) was defined as the surface tension of the coating liquid.

(Tanδ)
Using a viscoelasticity measuring device DAR-100 (manufactured by Jusco International Co., Ltd.), using a cone and plate (cone diameter 40 mm, angle 1 degree) as a measurement jig, measuring temperature 25 ° C., oscillation mode frequency 1 Hz, stress Measurement was performed at 6 Pa to determine the elasticity term (G ′) and viscosity term (G ″) of the coating solution, and Tan δ of the coating solution was calculated from the following equation.
Tan δ = G ″ / G ′

(Blank gloss)
Using a gloss meter (model: GM-26D, manufactured by Murakami Color Research Laboratory Co., Ltd.), the measurement result was 75 degrees according to ISO 8254-1 (1999) under an incident angle / light receiving angle of 75 degrees. Glossy. Moreover, the glossiness meter (model: GM-26D, manufactured by Murakami Color Research Laboratory Co., Ltd.) was used, and the results measured under conditions of incident angle / light receiving angle of 20 degrees according to ISO 8254-3 (2004) The gloss was 20 degrees.

(Smoothness)
In accordance with ISO 8791-4, a Parker Print Surf (PPS) surface smoothness tester (model name: MODEL M-569 type, manufactured by MESSMER BUCHEL, UK) was used, backing disk: soft rubber, clamp pressure: 0. The result measured at 98 MPa was defined as smoothness. The smaller the measured value (unit: μm), the higher the smoothness.

(Blank paper surface)
The surface property of the blank paper was visually evaluated. Evaluation was performed by the following five-step evaluation.
Those having a rating of 5 (excellent) -1 (inferior) and having an evaluation of 2 or less have practical problems.

(Print gloss)
Using an RI printing tester, printing was performed using 0.6 cc of printing ink (trade name: Varius G ink S type, manufactured by Dainippon Ink Co., Ltd.) and left for 48 hours in an atmosphere of 23 ° C. and 50% RH. The ink was dried, and the 60 ° gloss was measured using a gloss meter (model: GM-26D, manufactured by Murakami Color Research Laboratory) to obtain a print gloss.

(Ink setting)
Using an RI printing tester, printing is performed using 0.6 cc of printing ink (trade name: Varius G ink S type, manufactured by Dainippon Ink, Inc.). After 3 minutes, the blank paper and the printing surface are overlapped, and RI printing is performed again. The density of the ink nipped with a tester and transferred onto a white paper was visually evaluated. Evaluation was performed by the following five-step evaluation. 5 (excellent: low concentration) -1 (poor: high concentration) and a rating of 2 or less has a practical problem.

(Surface strength)
Using an RI printing tester, printing was performed a plurality of times using 0.4 cc of printing ink (ink red for paper test, manufactured by Toyo Ink Co., Ltd.), and the degree of picking on the printed surface was visually evaluated. Evaluation was performed by the following five-step evaluation.
Those having a rating of 5 (excellent) -1 (inferior) and having an evaluation of 2 or less have practical problems.

(Water absorption suitability)
Immediately after wetting with an RI printing tester, printing was performed using 0.5 cc of printing ink (trade name: Varius G ink S type, manufactured by Dainippon Ink Co., Ltd.), and the print density and ink unevenness were visually evaluated. did. Evaluation was carried out by a five-step evaluation.
Those having a rating of 5 (excellent) -1 (inferior) and having an evaluation of 2 or less have practical problems.

(Ink unevenness)
In the RI printing tester, printing was performed using 0.5 cc of printing ink (trade name: TOYOKING TKU CC Ai, manufactured by Toyo Ink Co., Ltd.) for the first color, and different printing inks (ink red for paper testing, Toyo Ink Co., Ltd.) is used, and the time after the first color printing is changed to 15 seconds, 30 seconds, 60 seconds, 90 seconds, 120 seconds, and 180 seconds. The meat unevenness was visually evaluated. The most inferior ink unevenness was evaluated, and the evaluation was performed in a five-step evaluation.
Those having a rating of 5 (excellent) -1 (inferior) and having an evaluation of 2 or less have practical problems.

  The coated paper for printing obtained in each example and comparative example was evaluated by the above method, and the results are shown in Table 1.

Example 1
<Preparation of base paper>
65 parts of LBKP (CSF 500 ml) bleached in multiple steps in the process consisting of oxygen-ozone-sodium hydroxide-hydrogen peroxide-chlorine dioxide and multi-stage bleaching in the process consisting of oxygen-ozone-sodium hydroxide-hydrogen peroxide-chlorine dioxide After adding light calcium carbonate (trade name: Tama Pearl TP-121, manufactured by Okutama Kogyo Co., Ltd.) as a filler to 100 parts of pulp slurry consisting of 35 parts of NBKP (CSF 500 ml), pulp slurry Of aluminum sulfate, 0.5 parts of cationic starch (trade name: Ace K-100, manufactured by Oji Cornstarch), alkyl ketene dimer sizing agent (trade name: Size Pine K-287, Arakawa Chemical Co., Ltd.) 0.1 parts, polyacrylamide (trade name: Polystron 851, Arakawa Chemical) Company Ltd.) were added sequentially 0.02 parts, was prepared stock. The obtained stock is made with an on-top twin-wire paper machine, and then oxidized starch (trade name: Ace A, manufactured by Oji Cornstarch) is 1.5 g / m ² (solid content) on both sides with a gate roll size press. A base paper having a basis weight of 64 g / m ² was prepared by coating.

<Preparation of aqueous coating liquid A for pigment coating layer>
To an aqueous solution to which 0.1 part of a dispersant (trade name: Aron T-50, manufactured by Toagosei Co., Ltd.) was added, kaolin (trade name: Milagros, manufactured by Engelhard, Inc., having an average particle size of 0.26 μm and a particle size of 2 μm or less. (95% ratio) Add 20 parts and disperse with a Coreless disperser, and further heavy calcium carbonate (trade name: Hydrocurve 90, manufactured by Bihoku Flour Industry Co., Ltd., average particle size 0.7 μm, particle size 2 μm or less 90%) 80 parts were added to prepare a pigment slurry. For 100 parts of pigment in the pigment slurry, 3 parts of starch (trade name: Ace A, manufactured by Oji Cornstarch Co., Ltd.) and styrene-butadiene copolymer latex (trade name: OJ-1000, manufactured by JSR) are used as an adhesive. 8 parts were added, an antifoaming agent and a dye were sequentially added as auxiliary agents, and water was further added to obtain an aqueous coating liquid A for a pigment coating layer having a solid content concentration of 63%.

<Preparation of aqueous coating liquid J for surface layer>
Coreless dispersion of 50 parts of hollow plastic pigment having an average particle diameter of 1.0 μm (trade name: MH8101, manufactured by Nippon Zeon Co., Ltd.), 50 parts of a thermoplastic polymer latex having a glass transition temperature of 70 ° C. and an average particle diameter of 0.20 μm After mixing and dispersing with a machine, 0.4 part of CMC sodium (trade name: Serogen BSH12) was added as a thickener and mixed until completely dissolved. Thereafter, 1.5 parts of a surfactant (trade name: Orphin WE-003, manufactured by Nissin Chemical Co., Ltd.) is added, and after adding an antifoaming agent and a dye sequentially as an auxiliary agent, water is added to add a solid content concentration. An aqueous coating solution J for a surface layer having 14.3%, a viscosity of 100 mPa · s, and a surface tension of 30 mN / m was prepared. In addition, Tanδ of this coating solution was 3.5.

<Preparation of coated paper for printing>
After the base paper made under the above conditions is coated with an aqueous coating liquid A for a pigment coating layer on a double side with a roll coater and dried at a coating speed of 1000 m / min so that the dry weight is 9 g / m ^{2 on} one side. The surface layer aqueous coating solution J was coated on both sides with a one-fluid spray coater so that the dry weight was 1.5 g / m ^{2 on} one side, dried, and then super calendered, with a basis weight of 85 g / m ^2. A coated paper for printing m ² was obtained. The PPS smoothness of the pigment coating layer was 4.3 μm.

Example 2
In Example 1, coated paper was obtained in the same manner as in Example 1 except that the coating method of the aqueous coating liquid A for the pigment coating layer was changed from the roll coating method to the blade coating method. In addition, the PPS smoothness of the pigment coating layer of a present Example was 3.8 micrometers.

Example 3
In Example 2, the amount of heavy calcium carbonate (trade name: Hydrocurve 90, supra) in the aqueous coating liquid A for the pigment coating layer was changed from 80 parts to 30 parts, and kaolins with different kaolins were used. (Trade name: Hydra Gloss 90, manufactured by J.M. Huber, average particle size 0.23 μm, ratio 99% of particle size 2 μm or less) and the blending amount was changed from 20 parts to 70 parts, Coated paper was obtained in the same manner as Example 2. In addition, the PPS smoothness of the base paper before applying the surface layer with the spray coater after coating and drying the pigment coating layer was 2.8 μm.

Example 4
In Example 2, the number of parts of heavy calcium carbonate in the aqueous coating liquid A for the pigment coating layer was changed from 80 parts to 50 parts, and the kaolins were different kaolins (trade names: Contour 1500, d50 ₁ : 4). .58 μm, d50 ₂ : 0.46 μm, d50 ₁ / d50 ₂ : 10, 88% ratio of particle size of 2 μm or less, manufactured by Imeris Minerals Japan Co., Ltd. A coated paper was obtained in the same manner as in Example 2 except that the partial concentration was changed from 63% to 60%. The PPS smoothness of the pigment coating layer was 3.3 μm.

Example 5
In Example 2, 0.3 part of sodium hydroxide was further added to the aqueous solution to which the dispersant was added, and the number of parts of heavy calcium carbonate in the aqueous coating liquid A for the pigment coating layer was changed from 80 parts to 70 parts. Furthermore, 10 parts of satin white (trade name: SW-B, manufactured by Shiroishi Kogyo Co., Ltd., average particle size 1.0 μm, ratio of particle size 2 μm or less 90%) was added, and the solid content concentration was changed from 63% to 59%. A coated paper was obtained in the same manner as in Example 2 except that. The PPS smoothness of the pigment coating layer was 3.1 μm.

Example 6
In Example 2, a nip group composed of a metal roll and a resin roll so that the PPS smoothness of the pigment coating layer is 3.0 μm after the aqueous coating liquid A for the pigment coating layer is applied and dried. A coated paper was obtained in the same manner as in Example 2 except that the paper was passed and smoothed.

Example 7
<Preparation of aqueous coating liquid B for pigment coating layer>
To an aqueous solution to which 0.1 part of a dispersant (trade name: Aron A-9, manufactured by Toagosei Co., Ltd.) has been added, 50 parts of kaolin (trade name: Milagros, supra) is added and dispersed with a Coreless disperser. 50 parts of heavy calcium carbonate (trade name: Hydrocurve 90, supra) was added to prepare a pigment slurry. For 100 parts of pigment in this pigment slurry, 3 parts of starch (trade name: Ace A, supra) and 8 parts of styrene-butadiene copolymer latex (trade name: OJ-1000, supra) are used as adhesives. Further, an antifoaming agent and a dye were sequentially added as auxiliary agents, and water was further added to obtain an aqueous coating liquid B for a pigment coating layer having a solid content concentration of 63%.

<Preparation of coated paper for printing>
In Example 1, after the aqueous coating liquid A for pigment coating layer was applied and dried by the roll coating method, the aqueous coating liquid B for pigment coating layer was further dried at a weight of 9 on one side. as a .5g / m ² provided by the blade coating method, except that to obtain a coated paper having a basis weight of 104 g / m ^2, to obtain a coated paper in the same manner as in example 1.

Example 8
In Example 7, a coated paper was obtained in the same manner as in Example 7 except that the coating method of the aqueous coating liquid A for the pigment coating layer was changed from the roll coating method to the blade coating method.

Example 9
In Example 2, the plastic pigment (trade name: MH8101, supra) in the aqueous coating liquid J for the surface layer was changed from 50 parts to 25 parts, and the number of parts of the thermoplastic polymer latex P was changed from 50 parts to 75 parts. A coated paper was obtained in the same manner as in Example 2 except that. The coating solution had a viscosity of 110 mPa · s, a surface tension of 29.8 mN / m, and Tan δ of 3.2.

Example 10
In Example 2, the thickener (trade name: Serogen BSH12, supra) in the aqueous coating liquid J for the surface layer was changed from 0.4 part to 1.5 parts, and further 0.1 part of sodium hydroxide And an acrylic alkali thickening type thickener (trade name: Somalex 270, manufactured by Somaru Co., Ltd.) 0.5 part, for a surface layer having a viscosity of 500 mPa · s and a surface tension of 30.3 mN / m A coated paper was obtained in the same manner as in Example 2 except that the aqueous coating solution was used. The Tan δ of this coating solution was 0.8.

Example 11
In Example 2, the viscosity was 35 mPa · s obtained by changing the thickener (trade name: Serogen BSH12, supra) in the aqueous coating liquid J for the surface layer from 0.4 part to 0.1 part. A coated paper was obtained in the same manner as in Example 2 except that the surface layer aqueous coating solution having a surface tension of 30 mN / m was used. The Tan δ of this coating solution was 12.

Example 12
In Example 11, water was further added to the aqueous coating liquid J for the surface layer, and the solid content concentration was changed from 14.3% to 7%. The viscosity was 8 mPa · s and the surface tension was 30 mN / m. A coated paper was obtained in the same manner as in Example 2 except that the surface layer aqueous coating solution was used. The Tan δ of this coating solution was 60.

Example 13
In Example 2, from a hollow plastic pigment (trade name: MH8101, supra) in the aqueous coating liquid J for the surface layer, a solid plastic pigment (trade name: V1004, manufactured by Nippon Zeon Co., Ltd., average particle size 0. 32 μm), the blending amount was changed from 50 parts to 70 parts, and the coating amount of the thermoplastic polymer latex P was further changed from 50 parts to 30 parts. Obtained. The coating solution had a viscosity of 90 mPa · s, a surface tension of 30.5 mN / m, and Tan δ of 3.8.

Example 14
In Example 2, the thermoplastic polymer latex P in the surface layer aqueous coating liquid J was changed to a thermoplastic polymer latex Q having a glass transition temperature of 30 ° C. and an average particle size of 0.26 μm. In the same manner as in Example 2, a coated paper was obtained. The coating solution had a viscosity of 100 mPa · s, a surface tension of 30 mN / m, and Tan δ of 3.5.

Example 15
In Example 2, except that the thermoplastic polymer latex P in the surface layer aqueous coating liquid J was changed to a thermoplastic polymer latex S having a glass transition temperature of 90 ° C. and an average particle diameter of 0.20 μm. In the same manner as in Example 2, a coated paper was obtained. The coating solution had a viscosity of 100 mPa · s, a surface tension of 30 mN / m, and Tan δ of 3.5.

Example 16
In Example 2, a coated paper was prepared in the same manner as in Example 2 except that the coating amount of the surface layer was changed from 1.5 g / m ² to 4.0 g / m ² , and the basis weight was 91 g / m ² . Coated paper was obtained.

Example 17
In Example 2, a coated paper was obtained in the same manner as in Example 2 except that the amount of the surfactant in the surface layer aqueous coating liquid J was changed from 1.5 parts to 0.1 parts. The coating solution had a viscosity of 100 mPa · s, a surface tension of 46 mN / m, and Tan δ of 3.0.

Example 18
In Example 2, coated paper was obtained in the same manner as in Example 2 except that the one-fluid spray was changed to a two-fluid spray of the coating liquid and air.

Comparative Example 1
In Example 2, after applying and drying the aqueous coating liquid A for the pigment coating layer, smoothing treatment with a super calendar was performed without applying the aqueous coating liquid J for the surface layer, and a basis weight of 82 g / except that to obtain a coated paper of m ² was obtained a coated paper in the same manner as in example 2.

Comparative Example 2
In Example 2, a coated paper was obtained in the same manner as in Example 2 except that after the surface layer was coated and dried, the smoothing process using a super calender was not performed.

Comparative Example 3
In Example 2, the blending amount of the hollow plastic pigment (trade name: MH8101, supra) in the aqueous coating liquid J for the surface layer was changed from 50 parts to 5 parts, and the blending amount of the thermoplastic polymer latex P was changed. A coated paper was obtained in the same manner as in Example 2 except that the amount was changed from 50 parts to 95 parts. The coating solution had a viscosity of 120 mPa · s, a surface tension of 29.5 mN / m, and Tan δ of 3.0.

Comparative Example 4
In Example 2, the compounding amount of the hollow plastic pigment (trade name: MH8101, supra) in the aqueous coating liquid J for the surface layer was changed from 50 parts to 95 parts, and the compounding amount of the thermoplastic polymer latex P was changed. A coated paper was obtained in the same manner as in Example 2 except that the amount was changed from 50 parts to 5 parts. The coating solution had a viscosity of 85 mPa · s, a surface tension of 31 mN / m, and Tan δ of 4.0.

Comparative Example 5
In Example 2, when adjusting the aqueous coating solution J for the surface layer, no thickener is added, and the dilution amount with water is adjusted to a solid content concentration of 40%. A coated paper was obtained in the same manner as in Example 2 except that was changed from the spray coating method to the blade coating method. In addition, as a result of observing the surface of the coated paper obtained by this comparative example with an electron microscope, the number of plastic pigments on the surface of the obtained coated paper is significantly lower than the blending ratio in the aqueous coating solution, It is presumed that the plastic pigment was scraped off during the blade coating and was not normally transferred onto the pigment coating layer.

Comparative Example 6
In Example 2, a viscosity of 1200 mPa · s obtained by changing the thickener (trade name: Serogen BSH12, supra) in the aqueous coating liquid J for the surface layer from 0.4 parts to 4.0 parts. A coated paper was obtained in the same manner as in Example 2 except that the surface layer aqueous coating solution was used. The surface tension of this coating solution was 30.5 mN / m, and Tan δ was 1.2.

Claims (17)

  At least one surface of the base paper has one or more pigment coating layers, and a surface layer formed on the pigment coating layer by a spray coating method, and the surface layer has a total solid content of the surface layer. A coated paper for printing, comprising 25 to 90% by mass of a plastic pigment and smoothed.   The coated paper for printing according to claim 1, wherein the blank paper glossiness at an incident / light receiving angle of 75 degrees is 80 or more based on ISO 8254-1 (1999).   The coated paper for printing according to claim 1 or 2, wherein the blank paper glossiness at an incident / light-receiving angle of 20 degrees based on ISO 8254-3 (2004) is 8 or more.   The coated paper for printing according to any one of claims 1 to 3, wherein the plastic pigment is a hollow type.   The thermoplastic polymer latex having a glass transition temperature (Tg) of 40 ° C. or higher and lower than 80 ° C. is contained in the surface layer in an amount of 5 to 70% by mass based on the total solid content of the surface layer. The coated paper for printing as described in any one of. The coated paper for printing as described in any one of Claim 1 to 5 whose coating amount after drying of the said surface layer is 0.1-3.0 g / m < ² > per single side | surface. On at least one side of the continuously running base paper,
(A) a step of forming one or more pigment coating layers,
(B) A plastic pigment occupying 25 to 90% by mass of the total solid content of the coating liquid is contained on the pigment coating layer, the viscosity is 5 to 800 mPa · s, the surface tension is 55 mN / m or less, and the following formula is used. A step of applying a surface layer coating solution having a Tan δ of 1 to 100 by a spray coating method and drying,
Tanδ = G ″ / G ′
G ′, G ″: Viscoelasticity measuring machine DAR-100 (manufactured by Jusco International Co., Ltd.), using a cone and plate (cone diameter 40 mm, angle 1 degree) as a measuring jig, measuring temperature 25 ° C., The measurement result of the elastic term and the viscosity term of the coating liquid performed at an oscillation mode frequency of 1 Hz and a stress of 6 Pa is shown.
(C) a step of smoothing the dried surface layer,
A method for producing a coated paper for printing, comprising:   The method according to claim 7, wherein the white paper glossiness at an incident / light-receiving angle of 75 degrees is 80 or more based on ISO8254-1 (1999) of the coated paper after the smoothing treatment step (c).   The method according to claim 7 or 8, wherein the white paper glossiness at an incident / light receiving angle of 20 degrees based on ISO 8254-3 (2004) of the coated paper after the smoothing treatment step (c) is 8 or more.   The method according to any one of claims 7 to 9, wherein the plastic pigment of the surface coating liquid in the step (b) is a hollow type.   The said surface coating liquid of a process (b) contains the thermoplastic polymer latex whose glass transition temperature (Tg) which occupies 5-70 mass% of coating liquid total solids is 40 degreeC or more and less than 80 degreeC. The method according to any one of 7 to 10. The method according to any one of claims 7 to 11, wherein the coating amount of the surface layer in the step (b) is 0.1 to 3.0 g / m ² per side.   The method according to any one of claims 7 to 12, wherein the spray coating method uses a one-fluid spray.   The method according to any one of claims 7 to 13, wherein the PPS smoothness measured by ISO8791-4 of the pigment coating layer formed in step (a) immediately before step (b) is 3.8 µm or less.   The method according to any one of claims 7 to 14, wherein the pigment coating layer formed in the step (a) is smoothened immediately before the step (b).   The method according to any one of claims 7 to 15, wherein at least one or all of the pigment coating layers in the step (a) are formed on a base paper by a blade coater. The method according to any one of claims 7 to 16, wherein the pigment coating layer formed in step (a) immediately before step (b) satisfies at least one of the following conditions (1) to (3).
(1) The average particle diameter measured by the precipitation method of all pigments is 1.0 μm or less, and the ratio of pigments having a particle diameter exceeding 2.0 μm is 10% by mass or less.
(2) The delaminated kaolin specified below is contained in the total pigment in an amount of 10 to 100% by mass.
Delaminated kaolin:
The average particle size d50 ₁ as measured by light scattering method is in the range of 2.0～5.0Myuemu, the average particle diameter d50 ₂ as measured by sedimentation method is in the range of 0.30～0.55Myuemu, moreover , an average particle size d50 ₁ and an average particle diameter d50 ₂ ratio _(d50 1 / d50 ₂₎ is delaminated kaolin is 4 or more.
(3) 3 to 20% by mass of satin white having an average particle diameter of 1.5 μm or less measured by a precipitation method is contained in all pigments.