JP2005213698A - Coated paper for printing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coated paper for printing having high bulkiness and white paper glossiness and excellent printability such as printing gloss and printing smoothness. <P>SOLUTION: The coated paper for printing is produced by applying coating layers on both surfaces of a base paper using delaminated kaolin as the pigment component of the coating layer. The amount of the delaminated kaolin is ≥50 mass% of the total pigment in the coating layer. Preferably, the delaminated kaolin has an average particle diameter d50<SB>1</SB>of 2.0-3.5μm measured by light-scattering, an average particle diameter d50<SB>2</SB>of 0.35-0.55μm measured by precipitation method and a d50<SB>1</SB>/d50<SB>2</SB>ratio of ≥4. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a coated paper having a coating layer mainly composed of a pigment and an adhesive on both sides of a base paper. More specifically, the present invention has a relatively white paper gloss despite its low density. The present invention relates to a coated paper for printing that is high and has excellent printability such as print gloss and print smoothness.

In general, coated paper for printing is manufactured by coating and drying a coating liquid mainly composed of pigment and adhesive on a base paper, and depending on the coating amount of the coating liquid and the method of finishing the coated paper, it can be cast. Classified into coated paper, art paper, coated paper, finely coated paper, and the like. These coated papers are subjected to multicolor printing or single color printing and used as commercial printed materials such as leaflets, brochures, posters, etc., and are widely used as publications such as books and magazines. In recent years, with the progress of visualization and colorization of printed matter, the appearance of the coated paper for printing, such as whiteness and smoothness, is more important than ever.
In the production of coated paper, the higher the required quality of product coated paper, the more the coating amount of the coating liquid is increased, and it is common to perform relatively severe smoothing treatment such as supercalendering. However, doing so increases the density of the coated paper. Incidentally, the glossy coated paper having a high gloss of white paper has a density of usually 1.15 g / cm ³ or more, whereas the density of a matte coated paper having a low white gloss of 0.9 g / cm2 is usually used. cm ³ or more and less than 1.15 g / cm ³ .

  On the other hand, from the viewpoint of reducing not only the manufacturing cost of the coated paper itself but also the logistics costs of printed publications printed on the coated paper, there is a strong demand for lighter coated paper for printing. . The weight reduction of coated paper can be realized by reducing the coating amount of the coating liquid and the basis weight of the base paper, but the former impairs printing quality such as printing smoothness and printing gloss, and the latter is paper. There is a problem that the printing workability is deteriorated due to the thickness reduction, the volume of the booklet is lost, and the touch feeling is deteriorated. For this reason, in the industry, there is a demand for the appearance of a bulky coated paper that does not cause a reduction in paper thickness even if the coated paper is lightened.

  A coated paper that has not been subjected to a smoothing treatment such as a matte coated paper or a super calendar generally has a higher paper thickness and a lower density than a glossy coated paper. This is largely due to differences in the smoothing process conditions such as supercalender, and in order to keep the paper thickness high, smoothing process is not performed at all, or even if it is performed (specifically, the calendering temperature, pressure, The number of processing stages, etc.) must be mild. However, if the smoothing process is omitted or if the processing conditions are not reduced, the surface smoothness of the product-coated paper may be lowered, and the print quality such as print smoothness and print gloss may be deteriorated.

  As one of the methods for obtaining a coated paper with a low basis weight but not so thin, that is, a bulky coated paper, a method of adopting a thermal soft calender in the finishing process of coated paper production has been proposed. (See Patent Documents 1 and 2). However, as a matter of course, the installation of a thermal soft calender is indispensable for this method, and even if a thermal soft calender is used, it is satisfactory if a general base paper or coating liquid composition is used. It is difficult to obtain high-quality bulky coated paper, and in order to obtain the desired bulky coated paper, consideration must be given to the base paper and coating liquid composition used there.

One way to increase the bulk of the base paper itself is to mix mechanical pulp with the base paper. In general, mechanical pulp is more effective in increasing the bulk of the base paper because the fiber is rigid compared to chemical pulp. However, although mechanical pulp varies depending on the type and degree of beating, generally the surface strength is weak, so the coated paper obtained by providing a coating layer on a base paper with a relatively large amount of mechanical pulp is not suitable for printing. There is a difficulty that mess is likely to occur. Furthermore, in addition to the surface smoothness being inferior, this type of base paper has a drawback that the performance of the coating liquid cannot be sufficiently brought out because the coating liquid easily permeates excessively.
As a technique for improving the printing quality of coated paper obtained from a base paper blended with mechanical pulp, it is known to blend bulky kaolin with a high sedimentation volume in the coating layer (see Patent Document 3). When the method is used, the balance between the density of the coated paper and the gloss of the white paper is not sufficient, and it is difficult to obtain a coated paper excellent in printing gloss and printing smoothness. In addition, as a technique to improve the print quality of coated paper obtained from base paper containing mechanical pulp and amorphous silica as a filler, a pigment with a narrow particle size distribution is selected and used as the coating liquid pigment. (Refer to Patent Document 4), however, when this method is used, a filler that inhibits interfiber bonding is blended, so that there is a problem that the surface strength is lowered, and excellent printability and density are obtained. It is difficult to balance.

In addition, as another method for making the base paper bulky, a technique is known in which the base paper contains a bulking agent such as a softening agent (see Patent Document 5). However, since the above bulking agent is originally intended to inhibit the binding between pulp fibers, it is difficult for the coated paper obtained from the base paper blended with the pulp fiber to maintain an appropriate printing strength. . In addition to this, the base paper containing the bulking agent is not only poor in surface smoothness as in the case of the base paper containing a large amount of mechanical pulp, but the coating liquid easily penetrates too much. There is a grudge that cannot fully draw out the performance.
As a method for improving the printing quality of coated paper containing a bulking agent in the base paper, a method of blending a plastic pigment has been proposed (see Patent Document 6). However, in this method, a super calendar is used under relatively severe conditions. Finishing is necessary, and it is virtually impossible to keep the density of the coated paper below about 1.0 g / cm ³ .

  As a conventional technique for obtaining a bulky coated paper, in addition to the above, blending of a specific delaminated kaolin into a coating layer has been proposed (see Patent Documents 7 to 9). However, all of these proposals use a delaminated kaolin having a relatively large particle size, so that only a coated paper with a relatively low blank gloss is obtained.

As described above, according to the conventional technology, even if the density is low, it is not possible to obtain a coated paper having a relatively high white paper gloss and excellent printability such as print gloss and print smoothness.
JP-A-9-228298 JP-A-6-294100 JP-A-5-98596 JP 2001-214395 A JP 2002-155494 A JP 2003-171893 A JP-A-11-302998 JP 2002-105889 A JP 2002-194698 A

  The present invention is a coated paper for printing having a coating layer mainly composed of a pigment and an adhesive on both sides of a base paper, and has a relatively high white paper gloss despite its low density. One of the objects is to provide a coated paper for printing excellent in printability such as print smoothness.

One of the printing coated papers according to the present invention is a printing coated paper that is provided with a coating layer mainly composed of a pigment and an adhesive on both sides of the base paper, and is then subjected to a smoothing process, and is in contact with the base paper. The coating layer contains 50% by weight or more of delaminated kaolin, 1 to 6% by weight of water-soluble adhesive based on the total pigment, and the density of the coated paper is 0.60 to 1.00 g / It is in the range of cm ³ , and the value of the formula: D × 100-G defined by the blank paper glossiness G and density D of the coated paper is 50 or less.

In this specification, the total pigment means all the pigments contained in the coating layer. Therefore, including 50% by mass or more of delaminated kaolin is synonymous with 50% by mass or more of the total amount of pigment contained in the coating layer occupied by delaminated kaolin. Similarly, when the water-soluble adhesive is contained in an amount of 1 to 6% by mass based on the total pigment, an amount of the water-soluble adhesive corresponding to 1 to 6% by mass of the total amount of pigment contained in the coating layer is applied. It is synonymous with being present.
Further, the blank paper glossiness referred to in this specification refers to a 75-degree specular glossiness defined by ISO 8254-1 Part 1 (1999), and is normally displayed in%.

The blank glossiness of the coated paper for printing (refers to the glossiness of the unprinted coated paper) and the density of the coated paper for printing (also referred to as tension) are the density of the base paper used for preparing the coated paper, It varies depending on the composition and coating amount of the coating liquid to be applied to the base paper, and the finishing conditions of the coating layer. However, for each of several ordinary types of coated paper currently on the market, the glossiness (%) and density (g / cm ³ ) of each blank paper are measured. By plotting each measured value on the orthogonal coordinates with the x-axis, it is possible to know the relationship between the white paper glossiness of the coated paper and the density. According to it, although there are some exceptions, it is common for coated papers with high blank glossiness to have high density and for coated papers with low blank glossiness to have low density. It can be seen that the relationship is a directly proportional relationship.

However, as long as the coating paper for printing according to the present invention contains a specific amount or more of the delaminated kaolin specified below, and the coating layer provided on the base paper contains a specific amount of water-soluble adhesive. The blank paper glossiness and density in the above-mentioned orthogonal coordinates,
0.60 ≦ x ≦ 1.00
100x-30 ≧ y ≧ 100x-50
Can be accommodated within the restricted area.

In coated paper for printing of the present invention, delaminated kaolin contained in the coating layer has an average particle size d50 ₁ as measured by light scattering method is in the range of 2.0～3.5Myuemu, precipitation method the average particle diameter d50 ₂ measured by, in the range of 0.35～0.55Myuemu, average particle size d50 ₁ and an average particle diameter d50 _{2 ratio,} characterized by d50 1 / d50 ₂ is 4 or more be able to.

  The coated paper for printing according to the present invention is an aqueous coating solution containing a delaminated kaolin in a predetermined amount or more on both sides of a base paper and limiting the amount of a water-soluble adhesive used in combination with a water-dispersible adhesive. It is obtained by coating and drying, followed by a smoothing treatment.

  The aqueous coating liquid that is the predecessor of the coating layer provided on the base paper contains a water-dispersible adhesive and a water-soluble adhesive. Examples of the water-soluble adhesive include oxidized starch, cationized starch, 1 type or 2 types or more selected from various starches such as esterified starch, synthetic resin adhesives such as polyvinyl alcohol, proteins such as casein, soy protein, synthetic proteins, cellulose derivatives such as carboxymethylcellulose and methylcellulose, etc. it can. The blending amount of the water-soluble adhesive in the aqueous coating solution is selected in the range of 1 to 6% by mass, preferably 2 to 5% by mass, based on the total amount of pigment blended in the aqueous coating solution. If the blending amount is less than 1% by mass, it is difficult to form a coating layer with high smoothness because the penetration of the coating solution into the base paper cannot be suppressed. On the other hand, if the blending amount exceeds 6% by mass, the arrangement of the pigments, particularly the orientation of the delaminated kaolin, is disturbed in the process of drying the coating solution, and the smoothness of the dried coating layer may be impaired.

  Examples of the water-dispersible adhesive blended in the aqueous coating liquid include conjugated diene copolymer latex such as styrene-butadiene copolymer and methyl methacrylate-butadiene copolymer, acrylic polymer latex, ethylene- Examples thereof include vinyl copolymer latex such as vinyl acetate copolymer, and one or more of these water-dispersible adhesives are used in combination with the water-soluble adhesive. . The amount of the adhesive compounded in the aqueous coating solution is the total amount of the water-dispersible adhesive and the water-soluble adhesive, and is 8 to 25% by mass of the total amount of the pigment contained in the aqueous coating solution, preferably 10 to 10%. It can be selected in the range of 20% by mass.

Delaminated kaolin that occupies at least 50% by mass of the total amount of pigment contained in the coating layer of the coated paper for printing according to the present invention will be described.
Delaminated kaolin is a clay mineral obtained by peeling a layered bulk kaolin into a single layer, and has a large aspect ratio. For this reason, when blended with the coating layer, the base paper can be effectively coated and the smoothness of the coating layer can be improved, so delaminated kaolin is used as a pigment component of the coating solution. Has been.
In general, the individual shape characteristics of tabular grains such as delaminated kaolin can be defined by the ratio of the major axis d to the thickness t (aspect ratio d / t). In the present invention, the delaminated kaolin is used. particulate characteristics of a specified average particle diameter d50 ₂ by an average particle size d50 ₁ and sedimentation method using a light scattering method.
In the light scattering method average particle size d50 ₁ measurement by the contrast its diameter is considered all individual particles to spherical particles are measured, the average particle size d50 ₂ measured by sedimentation method, particle shape In order to affect the sedimentation property, particles having a flat shape and slower sedimentation are measured as particles having a smaller apparent diameter. Thus, as the particle aspect ratio as described above is large, the average particle diameter d50 ₂ ratio by an average particle size d50 ₁ and sedimentation method using a light scattering _method, d50 1 / d50 ₂ is considered to increase.
In the present invention, a laser diffraction particle size distribution analyzer SALD-2000 (manufactured by Shimadzu Corporation) is used as a method for measuring the average particle size by the light scattering method, and Cedigraph 5100 (as a method for measuring the average particle size by the sedimentation method). Shimadzu Corporation) was used.

In the present invention, at least 50 wt% of the pigment total amount to be blended to the coating layer is composed of a delaminated kaolin, as a delaminated kaolin, the average particle size d50 ₁ as measured by light scattering method from 2.0 to 3 in the range of .5Myuemu, preferably in the range of 2.2～2.8Myuemu, average particle diameter d50 ₂ is 0.35~0.55μm measured by sedimentation method, scope preferably of 0.40~0.50μm There, the average particle size d50 ₁ and an average particle diameter d50 _{2 ratio,} d50 1 / d50 ₂ is 4 or more, preferably used delaminated kaolin is 5 or more.
Incidentally, the average particle size d50 ₁ and an average particle diameter d50 ₂ is, when it is less than each less than 2.0μm and 0.35μm is delaminated kaolin in coated liquid is excessively penetrate to order in the sheet It becomes difficult to form a coating layer with high smoothness. The average particle size d50 ₁ and an average particle diameter d50 ₂ is, when each exceeds 3.5μm and 0.55μm, it is difficult to obtain a coated paper having 40% or more sheet gloss. Then, in the case of d50 1 _/ d50 ₂ is less than 4, it is difficult to obtain a coated paper for printing the present invention is contemplated.

  In the coated paper for printing of the present invention, the delaminated kaolin whose coating layer is specified above is an amount of 50% by mass or more, preferably 70 to 95% by mass of the total amount of the pigment contained in the coating layer. Contain in a range of amounts. When the blending amount of the delaminated kaolin is less than 50% by mass of the total pigment, the coated paper for printing intended by the present invention cannot be obtained.

  In the coating layer of the coated paper for printing according to the present invention, a pigment other than the delaminated kaolin is blended. Examples of the pigment include delaminated kaolin, kaolin, talc, Clay, calcined kaolin, heavy calcium carbonate, light calcium carbonate, titanium dioxide, calcium sulfite, gypsum, barium sulfate, white carbon, amorphous silica, diatomaceous earth, magnesium carbonate, titanium dioxide, aluminum hydroxide, calcium hydroxide, In addition to inorganic pigments such as magnesium hydroxide, zinc hydroxide, zinc oxide, magnesium oxide, bentonite, and sericite, organic pigments such as urea formalin fine particles and fine hollow particles can be exemplified, and these can be used in combination. is there. However, the average particle size of these other pigments is preferably 1 μm or less in terms of the particle size measured by the sedimentation method, and beyond this, even if the amount used is small, the printing intended by the present invention There is a possibility that the coated paper cannot be obtained.

  In the printing coated paper of the present invention, in the range that does not interfere with the effect of the present invention, blue or purple dyes and colored pigments, fluorescent dyes, thickeners, water retention agents, antioxidants, anti-aging agents, Various auxiliary agents such as 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 agent can be appropriately blended.

  Next, the base paper used for the coated paper for printing of 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 commonly used bleached chemical pulps such as LBKP and NBKP, ground 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 suitably mixed and used, and it is preferable to blend mechanical pulp that is effective in reducing the density. Moreover, although it is also preferable to mix | blend DIP containing mechanical pulp, such as DIP derived from used newspaper, it is preferable that the quantity of mechanical pulp does not exceed 70 mass% of the total pulp mix | blended with a base paper. If it exceeds 70% by mass, the printability of the finally obtained coated paper, such as print smoothness and surface strength, may be impaired. 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 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 pulp and fillers, various types of papermaking exemplified by an internal sizing agent, anionic, nonionic, cationic or amphoteric yield improver, drainage improver, paper strength enhancer, etc. The internal additive aid 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.

  Furthermore, when preparing the base paper, the use of a bulking agent, a softening agent or the like having a function of inhibiting the binding between pulp fibers further assists the reduction in the density of the coated paper aimed at by the present invention. Specific examples of bulking agents and softening agents include, for example, polyhydric alcohol and fatty acid ester compounds, polyhydric alcohol and fatty acid ester compound polyoxyalkylene compounds, fatty acid polyamidoamines, polyhydric alcohol surfactants, fats and oils Nonionic surfactant etc. can be illustrated. Generally the addition amount of this bulking agent and a softening agent is about 0.5-1.0 mass% with respect to a pulp component.

The basis weight of the base paper used in coated paper for printing of the present invention is generally in the range of about 30 to 80 g / m ^2. The density of base paper is preferably less than 0.70 g / cm ^3, more preferably less than 0.60 g / cm ^3. In order to keep the density of the base paper within the above range, as described above, pulp blending, filler blending, and internal chemicals may be selected as appropriate, and wet paper press conditions, machine calendar conditions, and the like may be appropriately adjusted.
There are no particular limitations on the papermaking conditions of the base paper. 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. Of course, a starch solution or the like can be size-pressed.

  There is no particular limitation on the coating apparatus for the aqueous coating solution used when the coating layer is provided on the base paper. Trailing, 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, gates commonly used in the industry Coating apparatuses such as a roll coater, a gravure coater, a curtain coater, a die coater, and a spray coater can be used as appropriate. Of course, these devices may be on-machine or off-machine.

There is no particular limitation on the coating amount of the aqueous coating liquid, but considering the white paper quality, printing quality and printability of the resulting coated paper for printing, and also the drying capacity when producing coated paper, etc. It is desirable that the range is about 1 to 15 g / m ² , preferably 4 to 8 g / m ² , and such a dry coating amount forms a single coating layer on both sides of the base paper. In addition, as a method of drying a wet coating layer, various systems, such as vapor | steam drying, gas heater drying, electric heater drying, infrared heater drying, etc. are employable, for example.

In the production of the coated paper for printing of the present invention, in consideration of the blank paper quality, print quality and printability of the resulting coated paper for coating, smoothing treatment is performed with various calendar devices after the coating layer is formed. Apply. The conditions for the smoothing process vary depending on the target quality, but it is desired by the present invention by adjusting the coated paper density to be in the range of 0.60 to 1.00 g / cm ^3. A coated paper for printing can be obtained. When the density of the coated paper is less than 0.60 g / cm ³ , good white paper quality and good print quality cannot be obtained as the coated paper for printing. Further, when the density of the coated paper exceeds 1.00 g / cm ³ , the desired relationship between the glossiness of the blank paper and the density cannot be obtained. In addition, it is more preferable that finishing with the smoothing process so that the glossiness of the blank paper is 40% or more can provide more excellent print quality such as print gloss and print smoothness.
Examples of the calendar device that can be used include a calendar device that performs gloss finish such as a super calendar, a soft calendar, and a gloss calendar. 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: the off type, which is separate from the coater, and the on type, which 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, or polyacrylate resin, cotton, nylon, asbestos, aramid fiber, or the like is appropriately used. It should be noted that it is of course possible to use a suitable combination of a water coating device, an electrostatic humidifying device, a steam humidifying device, etc., for humidity control and humidification of the coated paper after finishing with a calendar.

EXAMPLES The present invention will be described more specifically with reference to the following examples. However, the present invention is not limited to these examples. In the following examples and comparative examples, “parts” and “%” indicate solid parts by mass and solids mass%, respectively.
The printing coated paper obtained in each Example and Comparative Example was evaluated by the following method, and the results are shown in Table 1.

・ Measurement of average particle size of pigment by light scattering method The particle size distribution of pigment is measured using a laser diffraction particle size distribution analyzer SALD-2000 manufactured by Shimadzu Corporation, and the average particle size corresponding to 50 cumulative mass%. The diameter (d50 ₁ ) was measured. The pigment dispersion used for the measurement was obtained by diluting a pigment slurry prepared by adding 0.05% of a dispersant (sodium polyacrylate) to the pigment to an area measurable with the measuring device. .

-Average particle diameter measurement of pigment by precipitation method The particle size distribution of the pigment was measured using Sedigraph 5100 manufactured by Shimadzu Corporation, and the average particle diameter (d50 ₂ ) corresponding to 50 cumulative mass% was obtained. . 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 obtained by diluting to about 1%.

-Density of coated paper and base paper The density of the coated paper and base paper was measured in accordance with JIS P 8118 (1998).

-Blank paper glossiness of coated paper 75 degree glossiness was measured using the gloss meter (GM-25 / made by Murakami Color Research Laboratory) based on ISO 8254-1 Part 1 (1999).

・ Glossiness of coated paper Printed twice (overprinting) using 0.3 cc of printing ink (Varius G ink S type / Dainippon Ink Co., Ltd.) at the RI printing tester. The ink was dried for 2 days in an atmosphere of 50% RH, and the 60 ° gloss was measured using a gloss meter (GM-26D / Murakami Color Research Laboratory).

・ Print smoothness of coated paper Performed printing (overprinting) twice using 0.3cc of printing ink (Varius G ink S type / Dainippon Ink Co., Ltd.) at RI printing tester, The ink was dried for 2 days in an atmosphere of 50% RH, and the smoothness of the printed surface was visually evaluated according to the following criteria.
A: The ink density is uniform, there is no unevenness, and the printing smoothness is very good.
○: Slight unevenness is observed in the ink density, but it is a good level as coated paper.
Δ: Unevenness in ink density is conspicuous and printing smoothness is inferior.
X: Unevenness in ink density is very conspicuous and printing smoothness is considerably inferior.

-Surface strength of coated paper Using an RI printing tester, printing was performed using 0.6 cc of printing ink (SD50 for paper testing / manufactured by Toyo Ink Co., Ltd.), and the degree of picking on the printed surface was visually evaluated.
A: Picking does not occur at all, and the surface strength is extremely good.
○: Picking is slightly occurring, but it is a good level as coated paper.
Δ: Picking occurs and the surface strength is poor.
X: A lot of picking occurs and the surface strength is considerably inferior.

Example 1
(A) Preparation of base paper 50% of LBKP (CSF 430 ml) bleached in multiple steps in a process consisting of oxygen-ozone-sodium hydroxide-hydrogen peroxide-chlorine dioxide, oxygen-ozone-sodium hydroxide-hydrogen peroxide-chlorine dioxide In a pulp slurry consisting of 20% NBKP (CSF 450 ml) and 30% GP (CSF 80 ml), which are multistage bleached in the process consisting of %, Aluminum sulfate 0.5%, pulp starch (Ace K-100 / manufactured by Oji Cornstarch) 0.5%, alkyl ketene dimer sizing agent (size pine K-) 287 / Arakawa Chemical Co., Ltd.) 0.1%, polyacrylamide (Polystron 851 / Arakawa Chemical) Ltd.) were successively added 0.02%, to prepare a paper stock. Papermaking obtained stock with on-top twin wire paper machine, further a gate roll size press apparatus oxidized starch (Ace A / Oji Cornstarch Co., Ltd.) in both 1.5 g / m 2 ^(solid content) coated and dried Then, a smoothing process was performed using a machine calendar to obtain a base paper having an actual amount of 50 g / m ² , a paper thickness of 73 μm, and a density of 0.68 g / cm ³ .

(B) Preparation of aqueous coating liquid Delaminated kaolin A (Contour 1160 / Imeris) was added to an aqueous solution in which 0.1 part of sodium polyacrylate was added as a dispersant to the delaminated kaolin to be dispersed. 90 parts and 10 parts of heavy calcium carbonate (Hydrocurve 90 / manufactured by Bihoku Powder Chemical Co., Ltd.) were sequentially added and dispersed with a Coreless disperser to prepare a pigment slurry. In this slurry, 4.0 parts of starch (Ace A / Oji Cornstarch) as an adhesive, 12 parts of styrene-butadiene copolymer latex (T-2561C / JSR), calcium stearate (Nopcoat C-104HS) as a lubricant (Manufactured by San Nopco) 0.2 parts, and auxiliary agents such as an antifoaming agent and a dye were sequentially added, and water was further added to obtain an aqueous coating solution having a solid content concentration of 53%. Incidentally, the delaminated kaolin A has an average particle size an average particle size d50 ₁ as measured by light scattering method 2.7 .mu.m, the average particle diameter d50 ₂ as measured by sedimentation method was measured 0.38 .mu.m, by light scattering method d50 ₁ and an average particle diameter d50 ₂ ratio was determined by sedimentation _method, d50 1 / d50 ₂ was 7.1.

(C) Manufacture of coated paper The base paper on which the aqueous coating solution is made under the above conditions is coated on both sides with a blade coater so that the dry weight is 7 g / m ² per side, dried, and then super calendered. Then, a coated paper for printing having an actual amount of 64 g / m ² , a paper thickness of 66 μm, and a density of 0.97 g / cm ³ was obtained.

Example 2
Of the pigments of the aqueous coating liquid of Example 1, heavy calcium carbonate (Hydrocurve 90 / Bihoku Powdered Industries Co., Ltd.) is changed to coarse heavy calcium carbonate (Hydro Curve 60 / Bihoku Powdered Industries Co., Ltd.). A coated paper for printing was obtained in the same manner as in Example 1 except that the aqueous coating liquid was prepared by changing. The resulting coated paper for printing had an actual amount of 64 g / m ² , a paper thickness of 66 μm, and a density of 0.97 g / cm ³ .

Example 3
(A) Preparation of base paper 35% NBKP (CSF 450 ml) bleached in a multi-step bleaching process consisting of oxygen-ozone-sodium hydroxide-hydrogen peroxide-chlorine dioxide, 50% GP (CSF 80 ml), and DIP manufactured from used newspaper After adding light calcium carbonate (Tama Pearl TP-121 / Okutama Kogyo Co., Ltd.) as a filler to a pulp slurry comprising 15% (CSF 180 ml) so that the base paper ash content is 15%, aluminum sulfate is added to the pulp solid content. 0.5%, cationic starch (Ace K-100 / Oji Cornstarch) 0.5%, alkyl ketene dimer sizing agent (Size Pine K-287 / Arakawa Chemical) 0.1%, polyacrylamide (Polystron) 851 / manufactured by Arakawa Chemical Co.) was sequentially added to prepare a paper stock. Papermaking obtained stock with on-top twin wire paper machine, further a gate roll size press apparatus oxidized starch (Ace A / Oji Cornstarch Co., Ltd.) in both 1.5 g / m 2 ^(solid content) coated and dried Then, smoothing was performed with a machine calendar to obtain a base paper having an actual amount of 50 g / m ² , a paper thickness of 86 μm, and a density of 0.58 g / cm ³ .

(B) Preparation of aqueous coating solution Delaminated kaolin B (Contour 1500 / Imeris) was added to an aqueous solution in which 0.1 part of sodium polyacrylate was added as a dispersant to the delaminated kaolin to be dispersed. 80 parts and 20 parts of heavy calcium carbonate (Hydrocurve 90 / manufactured by Bihoku Powder Chemical Co., Ltd.) were sequentially added and dispersed with a Coreless disperser to prepare a pigment slurry. To this slurry, 4.0 parts of starch (Ace B / Oji Cornstarch) as an adhesive, 12 parts of styrene-butadiene copolymer latex (T-2561C / JSR), calcium stearate (Nopcoat C-104HS) as a lubricant (Manufactured by San Nopco) 0.2 parts, and auxiliary agents such as an antifoaming agent and a dye were sequentially added, and water was further added to obtain an aqueous coating solution having a solid content concentration of 52%. Incidentally, the delaminated kaolin B has an average particle size an average particle size d50 ₁ as measured by light scattering method 2.7 .mu.m, the average particle diameter d50 ₂ as measured by sedimentation method was measured 0.46 .mu.m, by light scattering method d50 ₁ and an average particle diameter d50 ₂ ratio was determined by sedimentation _method, d50 1 / d50 ₂ was 5.9.

(C) Manufacture of coated paper The base paper on which the above aqueous coating solution is made under the above conditions is coated on both sides with a blade coater so that the dry weight is 5 g / m ² per side, and then dried by super calendering. Then, a coated paper for printing having an actual amount of 60 g / m ² , a paper thickness of 67 μm, and a density of 0.90 g / cm ³ was obtained.

Example 4
(A) Preparation of base paper 70% of LBKP (CSF 430 ml) bleached in a multi-step bleaching process with oxygen-ozone-sodium hydroxide-hydrogen peroxide-chlorine dioxide and oxygen-ozone-sodium hydroxide-hydrogen peroxide-chlorine dioxide After adding light calcium carbonate (Tama Pearl TP-121 / Okutama Kogyo Co., Ltd.) as a filler to a pulp slurry consisting of 30% NBKP (CSF 450 ml) bleached in multiple stages in the process consisting of , 0.5% aluminum sulfate, 0.5% cationic starch (Ace K-100 / Oji Cornstarch Co., Ltd.), alkyl ketene dimer sizing agent (Size Pine K-287 / Arakawa Chemical Co., Ltd.) 0 .1%, Polyacrylamide (Polystron 851 / Arakawa Chemical Co., Ltd.) 0.02% was added in order, and paper was added. It was prepared. Papermaking obtained stock with on-top twin wire paper machine, further a gate roll size press apparatus oxidized starch (Ace A / Oji Cornstarch Co., Ltd.) in both 1.5 g / m 2 ^(solid content) coated and dried Then, a smoothing process was performed using a machine calendar to obtain a base paper having an actual amount of 50 g / m ² , a paper thickness of 65 μm, and a density of 0.77 g / cm ³ .

(B) Preparation of aqueous coating solution Delaminated kaolin B (Contour 1500 / Imeris) was added to an aqueous solution in which 0.1 part of sodium polyacrylate was added as a dispersant to the delaminated kaolin to be dispersed. 90 parts and 10 parts of heavy calcium carbonate (Hydrocurve 90 / manufactured by Bihoku Powder Chemical Co., Ltd.) were sequentially added and dispersed with a Coreless disperser to prepare a pigment slurry. To this slurry, 4.0 parts of starch (Ace B / Oji Cornstarch) as an adhesive, 12 parts of styrene-butadiene copolymer latex (T-2561C / JSR), calcium stearate (Nopcoat C-104HS) as a lubricant (Manufactured by San Nopco) 0.2 parts, and auxiliary agents such as an antifoaming agent and a dye were sequentially added, and water was further added to obtain an aqueous coating solution having a solid content concentration of 52%.

(C) Manufacture of coated paper The base paper on which the above aqueous coating solution is made under the above conditions is coated on both sides with a blade coater so that the dry weight is 5 g / m ² per side, and then dried by super calendering. Then, a coated paper for printing having an actual amount of 60 g / m ² , a paper thickness of 62 μm, and a density of 0.97 g / cm ³ was obtained.

Example 5
(A) Preparation of base paper 80% of LBKP (CSF 430 ml) bleached in multiple steps in the process of oxygen-ozone-sodium hydroxide-hydrogen peroxide-chlorine dioxide and oxygen-ozone-sodium hydroxide-hydrogen peroxide-chlorine dioxide After adding light calcium carbonate (Tama Pearl TP-121 / Okutama Kogyo Co., Ltd.) as a filler to a pulp slurry consisting of 20% NBKP (CSF 450 ml) bleached in multiple stages in the process consisting of , 0.5% aluminum sulfate, 0.5% cationic starch (Ace K-100 / Oji Cornstarch Co., Ltd.), alkyl ketene dimer sizing agent (Size Pine K-287 / Arakawa Chemical Co., Ltd.) 0 0.1%, bulking agent (KB-115 / Kao Corporation) 0.8%, polyacrylamide (Polystron 851 / Manufactured River Chemical Co., Ltd.) were successively added 0.02%, to prepare a paper stock. Papermaking obtained stock with on-top twin wire paper machine, further a gate roll size press apparatus oxidized starch (Ace A / Oji Cornstarch Co., Ltd.) in both 1.5 g / m 2 ^(solid content) coated and dried Then, smoothing was performed with a machine calendar to obtain a base paper having an actual amount of 70 g / m ² , a paper thickness of 106 μm, and a density of 0.66 g / cm ³ .

(B) Preparation of aqueous coating liquid Delaminated kaolin C (Contour 2070 / Imeris) was added to an aqueous solution in which 0.1 part of sodium polyacrylate was added as a dispersant to the delaminated kaolin to be dispersed. 60 parts and 40 parts of heavy calcium carbonate (Hydrocurve 90 / manufactured by Bihoku Powder Chemical Co., Ltd.) were sequentially added and dispersed with a Coreless disperser to prepare a pigment slurry. To this slurry, 4.0 parts of starch (Ace B / Oji Cornstarch) as an adhesive, 12 parts of styrene-butadiene copolymer latex (T-2561C / JSR), calcium stearate (Nopcoat C-104HS) as a lubricant (Manufactured by San Nopco) 0.2 parts, and auxiliary agents such as an antifoaming agent and a dye were sequentially added, and water was further added to obtain an aqueous coating solution having a solid content concentration of 53%. Incidentally, the delaminated kaolin C has an average particle size an average particle size d50 ₁ as measured by light scattering method 2.1 .mu.m, the average particle diameter d50 ₂ as measured by sedimentation method was measured 0.47 .mu.m, by light scattering method d50 ₁ and an average particle diameter d50 ₂ ratio was determined by sedimentation _method, d50 1 / d50 ₂ was 4.5.

(C) Manufacture of coated paper The base paper on which the aqueous coating solution is made under the above conditions is coated on both sides with a blade coater so that the dry weight is 6 g / m ² per side, and then dried by super calendering. Thus, a coated paper for printing having an actual amount of 82 g / m ² , a paper thickness of 90 μm, and a density of 0.91 g / cm ³ was obtained.

Comparative Example 1
In the aqueous coating solution of Example 1, 4 parts of starch (Ace A / manufactured by Oji Cornstarch) were changed to 0 parts, and 0.1 part of a water retention agent (Somalex 270E / manufactured by Somar) was added to the aqueous coating liquid. A coated paper for printing was obtained in the same manner as in Example 1 except that the liquid was prepared. The resulting coated paper for printing had an actual amount of 64 g / m ² , a paper thickness of 66 μm, and a density of 0.97 g / cm ³ .

Comparative Example 2
Coating for printing in the same manner as in Example 1 except that in the aqueous coating solution of Example 1, 4 parts of starch (Ace A / Oji Cornstarch) was changed to 8 parts to prepare an aqueous coating solution. I got paper. The obtained coated paper for printing had an actual amount of 64 g / m ² , a paper thickness of 60 μm, and a density of 1.07 g / cm ³ .

Comparative Example 3
Of the pigments in the aqueous coating solution of Example 3, delaminated kaolin B (Contour 1500 / Imeris) was changed to fine kaolin (Miragros / Engelhard) to prepare an aqueous coating solution. Obtained a coated paper for printing in the same manner as in Example 3. The present fine kaolin has an average particle size d50 ₁ as measured by light scattering method 1.8 .mu.m, the average particle diameter d50 ₂ as measured by sedimentation method 0.24 .mu.m, and the mean particle diameter d50 ₁ as measured by light scattering method the average particle size d50 ₂ ratio was determined by sedimentation _method, d50 1 / d50 ₂ was 7.5. The obtained coated paper for printing had an actual amount of 60 g / m ² , a paper thickness of 66 μm, and a density of 0.91 g / cm ³ .

Comparative Example 4
Of the pigments of the aqueous coating solution of Example 3, delaminated kaolin B (Contour 1500 / Imeris) was changed to delaminated kaolin D (Kapim NP / RCC) to prepare an aqueous coating solution. A coated paper for printing was obtained in the same manner as in Example 3 except that it was prepared. Incidentally, delaminated kaolin D has an average particle size d50 ₁ is 3.7μm as measured by light scattering method, average particle diameter d50 ₂ is 0.95μm as measured by sedimentation method, the average particle size was measured by light scattering method d50 ₁ and an average particle diameter d50 ₂ ratio was determined by sedimentation _method, d50 1 / d50 ₂ was 3.9. The obtained coated paper for printing had an actual amount of 60 g / m ² , a paper thickness of 66 μm, and a density of 0.91 g / cm ³ .

Comparative Example 5
Of the pigments in the aqueous coating solution of Example 3, delaminated kaolin B (Contour 1500 / Imeris) was changed to delaminated kaolin E (Capim DG / RCC) to prepare an aqueous coating solution. A coated paper for printing was obtained in the same manner as in Example 3 except that it was prepared. Incidentally, delaminated kaolin E has an average particle size d50 ₁ is 2.3μm as measured by light scattering method, average particle diameter d50 ₂ is 0.61μm as measured by sedimentation method, the average particle size was measured by light scattering method d50 ₁ and an average particle diameter d50 ₂ ratio was determined by sedimentation _method, d50 1 / d50 ₂ was 3.8. The obtained coated paper for printing had an actual amount of 60 g / m ² , a paper thickness of 66 μm, and a density of 0.91 g / cm ³ .

Comparative Example 6
Among the pigments of the aqueous coating liquid of Example 5, delaminated kaolin C (Contour 2070 / Imeris) was changed to engineered kaolin (Exsilon / Engelhard) to prepare an aqueous coating liquid. Except for the above, a coated paper for printing was obtained in the same manner as in Example 5. The present engineered kaolin has an average particle size an average particle size d50 ₁ as measured by light scattering method 2.4 [mu] m, an average particle diameter d50 ₂ as measured by sedimentation method was measured 0.61 .mu.m, by a light scattering method d50 ₁ the average particle size d50 ₂ ratio was determined by sedimentation method _and, d50 1 / d50 ₂ was 3.9. The obtained coated paper for printing had an actual amount of 82 g / m ² , a paper thickness of 90 μm, and a density of 0.91 g / cm ³ .

Comparative Example 7
Of the pigments in the aqueous coating solution of Example 5, delaminated kaolin C (Contour 2070 / Imeris) was changed to delaminated kaolin F (New Surf / Engelhard), and the aqueous coating solution was used. A coated paper for printing was obtained in the same manner as in Example 5 except that was prepared. Incidentally, delaminated kaolin F has an average particle size d50 ₁ is 5.6μm as measured by light scattering method, average particle size d50 ₂ as measured by sedimentation method 2.1 .mu.m, the mean particle size was measured by light scattering method d50 ₁ and an average particle diameter d50 ₂ ratio was determined by sedimentation _method, d50 1 / d50 ₂ was 2.7. The obtained coated paper for printing had an actual amount of 82 g / m ² , a paper thickness of 90 μm, and a density of 0.91 g / cm ³ .

Comparative Example 8
Of the pigment of the aqueous coating liquid of Example 5, 30 parts of 60 parts of delaminated kaolin C (Contour 2070 / Imeris) were changed to fine kaolin (Miragros / Engelhard) and water based. A coated paper for printing was obtained in the same manner as in Example 5 except that the coating liquid was prepared. The obtained coated paper for printing had an actual amount of 82 g / m ² , a paper thickness of 90 μm, and a density of 0.91 g / cm ³ .

Claims (8)

In a printing coated paper in which a coating layer mainly composed of a pigment and an adhesive is provided on both sides of the base paper, and then smoothed, the coating layer in contact with the base paper contains delaminated kaolin in an amount of 50% of the total pigment. % Or more, 1 to 6% by mass of the water-soluble adhesive, and the density of the coated paper is in the range of 0.60 to 1.00 g / cm ^3. And a density D. A coated paper for printing, wherein the value of D × 100-G is 50 or less.   The coated paper for printing according to claim 1, wherein the glossiness of the blank paper is 40% or more. Delaminated kaolin, there average particle size d50 ₁ as measured by light scattering method in the range of 2.0～3.5Myuemu, average particle diameter d50 ₂ of 0.35~0.55μm measured by sedimentation method in the range, moreover, average particle size d50 ₁ and an average particle diameter d50 _{2 ratio,} d50 1 / d50 ₂ is coated paper for printing according to claim 1 or 2 is 4 or more. In a coated paper for printing, which is provided with a coating layer mainly composed of a pigment and an adhesive on both sides of the base paper and then smoothed, 50% by mass or more of the total amount of pigment contained in the coating layer is delaminated. a kaolin, the delaminated kaolin has an average particle size d50 ₁ as measured by light scattering method is in the range of 2.0～3.5Myuemu, the average particle diameter d50 ₂ as measured by sedimentation method 0. in the range of 35～0.55Myuemu, moreover, average particle size d50 ₁ and an average particle diameter d50 _{2 ratio,} d50 1 / d50 coated paper for printing, characterized in that ₂ is 4 or more.   The coated paper for printing according to claim 4, wherein the adhesive contained in the coating layer comprises a water-dispersible adhesive and a water-soluble adhesive, and the water-soluble adhesive is in the range of 1 to 6% by mass of the total pigment. . The coated paper for printing according to claim 4 or 5, wherein the density of the coated paper for printing is in the range of 0.60 to 1.00 g / cm ³ .   The coated paper for printing according to any one of claims 4 to 6, wherein the glossiness of the white paper of the coated paper for printing is 40% or more. The coated paper for printing according to any one of claims 4 to 7, wherein the density of the base paper on which the coating layer is provided is 0.60 g / cm ³ or less.