JP2006274496A - Coated printing paper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide offset coated printing paper having extremely high whiteness of 100.0% or higher in ISO whiteness specified in JIS P-8148 and excellent in printing color developability. <P>SOLUTION: The coated printing paper is such that at least one side thereof is borne with a coating layer comprising a white pigment, adhesives and a fluorescent brightening agent. In the printing paper, a polyvinyl alcohol ≤800 in degree of polymerization and/or a derivative thereof as an adhesive is contained at 4-15 mass% based on the white pigment, and the total compounding amount of the adhesives is 10-30 mass% based on the white pigment. The coated printing paper is 100.0% or higher in ISO whiteness specified in JIS P-8148. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an offset-coated printing paper. More specifically, the present invention relates to offset coated printing paper having extremely high whiteness.

  In recent years, in many fields such as catalogs, posters, photo books, books, flyers, etc., it has been required to further increase the color contrast between the image portion and the non-image portion. In order to increase the color contrast between the image portion and the non-image portion, it has been found that the higher the whiteness of the non-image portion, the higher the effect. Furthermore, since the effect becomes clearer as the printing color forming property for forming the image portion becomes higher, it is desired that the printing paper used in these fields has high whiteness and high printing color forming property.

  Conventionally, as a method for increasing whiteness, as disclosed in Patent Document 1, the use of a fluorescent whitening agent such as a diaminostilbene-disulfonic acid derivative is generally used. The reason why whiteness can be increased by using fluorescent whitening agents is thought to be because the fluorescent whitening agent absorbs ultraviolet light and, as a result, has the property of increasing the reflectance in the blue region of visible light. Yes. In addition, fluorescent whitening agents are widely used especially in the manufacture of paper because of their high adsorptivity to cellulose fibers.

  In addition, as a method for improving the printing colorability, a coating liquid comprising a white pigment such as kaolin, calcium carbonate, plastic pigment and an adhesive such as oxidized starch or styrene-butadiene latex is applied to the surface of the base paper, A method of coating fibers is commonly used.

  As a method for effectively expressing the performance of the optical brightener, a method using polyvinyl alcohol and / or a derivative thereof together with the optical brightener is known. Furthermore, Patent Document 2 proposes a method for obtaining a coated paper excellent in whiteness by specifying the amount of polyvinyl alcohol or its derivative used and the drying conditions of the coating composition.

  Polyvinyl alcohol and its derivatives have a high affinity with fluorescent brightening agents, a dispersing agent that prevents aggregation of fluorescent brightening agent particles, a water retention agent to keep the fluorescent brightening agent on the surface of the coating layer, and It is known that a high effect can be obtained when used together with a fluorescent whitening agent as a fixing agent for preventing fading due to a structural change of the fluorescent whitening agent. In addition, it has high performance as an adhesive, and has long been compared with water-soluble adhesives such as oxidized starch and casein as paint adhesives on coated printing paper. However, when polyvinyl alcohol and / or its derivatives are blended in high amounts, the viscosity of the paint increases and the solid content of the paint cannot be increased, and the agglomerates are generated due to the high adsorption capacity for white pigments and adhesives. Problems such as being easy to do are pointed out. For this reason, when using polyvinyl alcohol and / or its derivatives in coated printing paper, it is limited to use at 2.5 mass% or less with respect to the white pigment, and generally used at 1 mass% or less. It had been.

  In addition, emulsion latexes such as styrene-butadiene latex, acrylic latex, and vinyl acetate latex, which are widely used as adhesives for coating, have a problem in transparency to transmit ultraviolet rays. There was a problem that the effect of the agent could not be sufficiently expressed and it acted as an interfering substance for the optical brightener.

  For this reason, an extremely high white coated printing paper having an ISO whiteness of 100.0% or more as defined in JIS P-8148 has not been obtained so far.

JP-A-3-294598 JP-A-62-28493

An object of the present invention is to provide an offset coated printing paper having an extremely high whiteness with an ISO whiteness of 100.0% or more as defined in JIS P-8148 and a high printing color development property.

  The present inventors have focused on the fact that the above-mentioned problems can be solved by blending a specific amount of specific polyvinyl alcohol and / or a derivative thereof as a coating liquid containing a fluorescent brightening agent, and the present invention has been completed. It was. That is, by using polyvinyl alcohol with a low polymerization degree and / or its derivative in an extremely large amount as compared with a conventional method, the coating suitability and the performance of the optical brightener which cannot be obtained in the past can be sufficiently expressed. Preferably, by specifying the blending ratio of polyvinyl alcohol and / or its derivative and other adhesives, an extremely high whiteness can be expressed, and the desired high whiteness and high printing color development offset coating It became possible to provide printing paper.

  That is, the invention according to claim 1 of the present invention is a coated printing paper having a coating layer containing a white pigment, an adhesive and a fluorescent brightening agent on at least one surface, and the adhesive has a polymerization degree of 800 or less. 4 to 15% by mass of polyvinyl alcohol and / or its derivative with respect to the white pigment, and the total amount of the adhesive is 10 to 30% by mass with respect to the white pigment, and is defined in JIS P-8148. The ISO whiteness is 100.0% or more.

  The invention according to claim 2 is characterized in that the blending ratio of the polyvinyl alcohol and / or derivative thereof is 20% or more with respect to the total blending amount of the adhesive. It is.

  According to the present invention, the ISO whiteness specified in JIS P-8148 is extremely high whiteness of 100.0% or more, and the printing color developability is excellent. It is possible to provide a coated printing paper having a clear color contrast.

  Hereinafter, embodiments of the coated printing paper according to the present invention will be described in detail. The polyvinyl alcohol and / or derivative thereof used in the present invention has a polymerization degree of 800 or less and is blended in an amount of 4 to 15% by mass with respect to the white pigment. When the degree of polymerization exceeds 800, the viscosity of the coating solution increases remarkably, so that the concentration of the coating solution cannot be increased, and the binding property to the white pigment and the adhesive increases, so that the coating solution is solidified. Since it becomes easy, it is not preferable. However, polyvinyl alcohol having a degree of polymerization exceeding 800 and / or a derivative thereof can be used in a smaller amount than polyvinyl alcohol having a degree of polymerization of 800 or less and / or a derivative thereof within the scope of the present invention.

  Moreover, in the compounding quantity of polyvinyl alcohol and / or its derivative (s), if less than 4 mass% with respect to a white pigment, since the dispersibility of a fluorescent whitening agent will become inadequate, it is unpreferable. For this reason, if a large amount of fluorescent whitening agent is blended, the color originally possessed by the fluorescent whitening agent is colored (a greening phenomenon), and a fluorescent whitening agent for obtaining sufficient whiteness can be blended. It will disappear. On the other hand, when the content is more than 15% by mass, the viscosity of the coating becomes too high, and the solubility in water of polyvinyl alcohol and / or its derivatives is not high. The coating conditions are deteriorated, and it is not preferable because it becomes difficult to obtain a coated printing paper having an extremely high whiteness as an object of the present invention.

  The polyvinyl alcohol and / or derivative thereof having a saponification degree of 80% or more can be used. The lower the saponification degree, the more the saponification reaction proceeds in a higher pH range, generating free acetic acid and generating a unique acetic acid odor, which is not preferable because the commercial value as a coated printing paper is lowered. The saponification degree of polyvinyl alcohol and / or its derivative is preferably 90% or more, more preferably 95% or more.

  The types of polyvinyl alcohol and / or its derivatives are not limited to those obtained by saponifying a vinyl acetate polymer, but esterification, etherification, acetalization, copolymerization, silanol modification, carboalkyl modification, carbonyl modification. Etc. can be used.

  The present inventors infer that the reason why polyvinyl alcohol having a polymerization degree of 800 or less and / or a derivative thereof is effective in the present invention is as follows. That is, there is a correlation between the degree of polymerization in polyvinyl alcohol and / or its derivative and the viscosity of the aqueous solution, and when blended as a coating solution, the viscosity of the aqueous solution affects the viscosity of the coating solution, and the lower the degree of polymerization, Since the influence on the viscosity of the coating liquid is reduced, the range of the viscosity of the coating liquid that can be adjusted with various thickeners is preferably increased.

  More importantly, the polyvinyl alcohol and / or its derivative is a composition having a hydrophilic group such as a hydroxyl group having a long hydrocarbon chain as a skeleton, and as a result, the adhesive has a high binding force with a white pigment. However, there is a problem that the hydrocarbon chain surrounds the white pigment and hydrophobizes the white pigment to solidify the coating liquid (usually called PVA shock). This tendency becomes more prominent as the degree of polymerization of polyvinyl alcohol and / or its derivatives increases. In addition, polyvinyl alcohol and / or its derivatives have a high binding force with the water-retaining adhesive in the coating liquid, and the higher the degree of polymerization of polyvinyl alcohol and / or its derivatives, the more it binds to the water-retaining adhesive and There is a problem that the protective effect is lowered. For this reason, polyvinyl alcohol having a low polymerization degree and / or a derivative thereof has a short molecular chain, and a stable coating liquid can be prepared as a water retention adhesive for white pigments. When a large amount of the derivative is blended in the paint, it becomes impossible to prepare a stable coating solution having coating suitability. Furthermore, when this coating solution is applied, the coating surface becomes streaked or the coating solution is solidified, resulting in a problem that the smoothness of the coating surface cannot be obtained. As printing paper, the performance is significantly reduced.

  The white pigment used in the present invention includes light calcium carbonate, heavy calcium carbonate, kaolin, delaminated kaolin, calcined kaolin, clay, talc, magnesium carbonate, magnesium oxide, satin white, aluminum hydroxide, calcium hydroxide, Inorganic white pigments such as zinc hydroxide, zinc oxide, barium sulfate, titanium oxide, clay, synthetic amorphous silica, bentonite, polystyrene resin particles, urea formalin resin particles, hollow organic pigments, organic pigments such as porous particles, Among various pigments conventionally used for coating, at least one pigment can be appropriately blended within the range of ISO whiteness in the present invention.

  Note that white pigments that absorb ultraviolet rays, such as titanium oxide and zinc oxide, may impair the performance of the fluorescent brightening agent, so special care is required when used within the scope of the invention. In addition, white pigments having a high pH dispersion of calcium carbonate, calcium hydroxide and the like are particularly preferred because they have the effect of enhancing the whitening effect of the fluorescent whitening agent and reducing the fading.

  In addition to polyvinyl alcohol and / or its derivatives, the adhesive used in the present invention is oxidized starch, esterified starch, etherified starch, casein, soy protein, styrene-butadiene latex, acrylic latex, styrene acrylic latex. One or more types of emulsion latex resins, polyurethane resins, melamine resins, urea resins, and the like made of various copolymers such as vinyl acetate latex and the like can be appropriately used within the range of ISO whiteness in the present invention.

  The compounding quantity of the adhesive with respect to a white pigment can be used in the range of 10-30 mass%. If the amount is less than 10% by mass, the surface strength in offset printing is insufficient, and the coating layer is peeled off and printing troubles such as frequent printing blanket contamination occur, which is not preferable. On the other hand, when the amount is more than 30% by mass, the ratio of the adhesive in the coating layer is increased, and as a result, printing trouble such as impairing the drying property of the offset printing ink occurs.

  In addition, adhesives other than polyvinyl alcohol and / or its derivatives contained in the coating liquid cannot necessarily improve the performance of the optical brightener, but rather reduce it, so that the adverse effects of these adhesives are minimized. Therefore, the blending ratio of polyvinyl alcohol and / or its derivative with respect to the total blending amount of the adhesive is preferably 20% by mass or more.

  As the optical brightener used in the present invention, those conventionally used such as stilbene, coumarin, pyrazoline, naphthalimide, benzoxazole, imidazole, thiazole, and distyrylbiphenyl are used. be able to. For example, among diaminostilbene-disulfonic acid derivatives, many fluorescent whitening agents having high dispersibility and developed for coating use are commercially available depending on the selection of the solubilizing agent and the number of sulfonic acid groups.

  The fluorescent whitening agent is used in an amount of 1 to 7% by mass with respect to the white pigment. If the amount is less than 1% by mass, the whitening effect of the fluorescent whitening agent is not sufficient. If the amount exceeds 7% by mass, the dispersibility of the fluorescent whitening agent cannot be ensured sufficiently. This is not preferable because it exhibits the color inherent in the fluorescent brightening agent.

  Coating liquids include polyvinyl alcohol and / or its derivatives, white pigments, adhesives, fluorescent brighteners, cellulose derivatives, water retention agents, crosslinking agents, curing agents, antifoaming agents, thickeners, water resistance Agents, mold release agents, lubricants, preservatives, antifungal agents, dyes, colored pigments, and the like can be used as long as they are within the ISO whiteness range in the present invention.

  The base paper used in the present invention is not particularly limited, such as the type of raw materials, the papermaking method such as acidic papermaking or neutral papermaking, the type of papermaking machine, surface properties, basis weight, etc., and a coating layer is provided. In this case, those within the ISO whiteness range in the present invention can be appropriately selected and used. For example, wood pulp such as kraft pulp, sulfite pulp, soda pulp, dissolving pulp, semi-chemical pulp, mechanical pulp, thermomechanical pulp, and groundwood pulp, cotton, linter, bamboo, bamboo, kenaf, cocoon, three bases, husk, hemp One or more kinds of fibers such as non-wood pulp such as SEP, rayon, polyester, etc., waste paper, etc. If necessary, light calcium carbonate, heavy calcium carbonate, kaolin, clay, talc, synthetic non Fillers such as crystalline silica and titanium oxide, sizing agents such as rosin sizing agent, reinforced rosin sizing agent, emulsion sizing agent, alkyl ketene dimer, alkenyl succinic anhydride, and cation used in ordinary acidic papermaking or neutral papermaking Starch, pregelatinized starch, amphoteric starch, polyacrylamide, polyvinyl alcohol Paper strength enhancers such as polyamine polyamide epichlorohydrin, sulfuric acid bands, freeness improvers, yield improvers, pitch control agents, slime control agents, polymer fixing agents, antifoaming agents, dyes, colored pigments, fluorescent whitening agents, etc. The raw materials and chemicals generally used for papermaking can be used.

As the paper machine, a long net paper machine, a circular net paper machine, a combination of a long net and a circular net, a twin wire paper machine, an on-top twin wire paper machine or the like can be used as necessary. The surface properties of the base paper include the embossing treatment with patterns such as blankets, rolls, canvas, etc., calender treatment with smoothness such as chilled, cotton, resin, etc. Etc. Basis weight monolayer, multilayer, by ^lamination, those 20g / ^{m 2} ~400g / m 2 are generally used.

  In addition, synthetic paper mainly composed of a synthetic material such as polyolefin, films, and sheets such as wet or dry nonwoven fabric can be used as the base paper. In addition, clear paper such as starch, polyvinyl alcohols, polyacrylamides, or coated paper made of pigment and adhesive can be used as the base paper.

As an apparatus for coating a base paper with a coating liquid composed mainly of polyvinyl alcohol and / or a derivative thereof, a white pigment and an adhesive, known coating equipment such as a size press coater, a gate roll coater, a building A blade coater, an air knife coater, a blade coater, a rod coater, a curtain coater, a die coater, a gravure coater, or the like can be used. The concentration of the coating solution at this time is not particularly limited, but can be adjusted in the range of 15 to 65% by mass, more preferably 20 to 60% by mass. The coating amount in particular but not limited to, per side 1 to 30 g / ^{m 2,} preferably can be adjusted in the range of 3 to 20 g / ^{m 2.}

  Examples of the present invention will be described below. The ISO whiteness (%), printing uniformity, surface strength, ink set drying property, and coating liquid aggregates in Examples and Comparative Examples were evaluated by the following methods. Moreover, the mass% in an Example and a comparative example shows solid content conversion value except the case where it specifies.

[ISO whiteness]
ISO whiteness was measured according to JIS P-8148 using a spectral whiteness meter (trade name “PF-10”, manufactured by Nippon Denshoku Industries Co., Ltd.).

[Print uniformity]
The printing uniformity is evaluated as coating surface uniformity such as streaks and unevenness of the coating surface. 0.6 g of indigo ink (trade name “HIYUNITY AIN MZ”, manufactured by Toyo Ink Mfg. Co., Ltd.) was printed on paper with an RI tester, and the printed surface after one day was visually (5; excellent) (4; Good), (3; Possible), (2; Impossible), (1; Impossible).

[Surface strength]
The surface strength is visually determined as the degree of paper peeling when 0.6 g of black ink with a tack value of 20 (trade name “SMX Tuck Grade 20XF”, manufactured by Toyo Ink Manufacturing Co., Ltd.) is printed on paper using an RI tester. (5; Excellent), (4; Good), (3; Acceptable), (2; Impossible), (1; Impossible). Three or more were used as the coated printing paper of the present invention.

[Ink set drying]
Ink set drying property was determined by printing 0.6 g of black ink (trade name “HIUNITY SHIKI MZ”, manufactured by Toyo Ink Mfg. Co., Ltd.) on paper using an RI tester, 1 minute, 5 minutes, 10 minutes later. , 20 minutes later, 30 minutes later when the printed surface is transferred to a blank A2 coated paper, the ink show-through is visually (5; excellent), (4; good), (3; acceptable), ( (2; Impossible) and (1; Impossible).

[Coating liquid aggregation state]
The coating solution aggregation state was visually (5; none), (4;) in the residue obtained by filtering 1000 g of the coating solution having a solid content of 35% by mass through a filter having an opening of 150 μm after preparation of the coating solution. A small amount), (3; small amount), (2; large amount), and (1; very large amount) were evaluated in 5 stages, and 3 or more were used as the coated printing paper of the present invention. When a large amount of agglomerates is generated, problems such as a decrease in uniformity of the coated surface or a pickling and soiling of the blanket occur in printing with an offset printing press.

[Example 1]
To a light calcium carbonate (trade name “Tama Pearl TP-123”, manufactured by Okutama Kogyo Co., Ltd.), 0.5% by mass of a dispersant (trade name “Poise 520”, manufactured by Kao Co., Ltd.) is added. Using a disperser, the mixture was dispersed at a solid content concentration of 60% by mass for 1 hour to obtain a white pigment dispersion. 60% by mass of this dispersion and heavy calcium carbonate (trade name “FMT-90”, manufactured by Pimatech) were mixed together with 40% by mass to obtain a pigment slurry. Based on 100% by mass of this pigment slurry, 10% by mass of polyvinyl alcohol having a polymerization degree of 500 and a saponification degree of 94% (trade name “JM-05”, manufactured by Nippon Acetate / Poval Co., Ltd.) 10% by weight of polymerized latex (trade name “Smartex SN-307”, manufactured by Nippon A & L Co., Ltd.), 1% by weight of calcium stearate (trade name “DEF-922”, manufactured by Nissin Chemical Laboratory Co., Ltd.) , 0.5 mass% of ammonium zirconium carbonate (trade name “AZ Coat 5800MT”, manufactured by San Nopco Co., Ltd.), 5 mass of fluorescent brightener (trade name “Brancofar UW-L”, manufactured by LANXESS Co., Ltd.) % Was added to obtain a coating solution.

Kraft pulp (LBKP 90% by mass and NBKP 10% by mass) was added as a main component, a fluorescent brightener was added, and an acid paper having a basis weight of 105 g / m ² was obtained as a base paper by a conventional method. The ISO whiteness of this base paper was 95.5%. The base paper obtained here was coated on both sides so that the coating amount was 10 g / m ² per side to obtain a coated printing paper.

[Example 2]
A coated printing paper was obtained in the same manner as in Example 1, except that the saponification degree of polyvinyl alcohol was changed to 88% (trade name “JP-05”, manufactured by Nippon Vinegar Poval Co., Ltd.).

[Example 3]
A coated printing paper was obtained in the same manner as in Example 1 except that the saponification degree of polyvinyl alcohol was changed to 98% (trade name “JF-05”, manufactured by Nippon Vinegar Poval Co., Ltd.).

[Example 4]
The same procedure as in Example 1 was followed, except that the polyvinyl alcohol was changed to a carbonyl-modified polyvinyl alcohol derivative (trade name “DF-05”, manufactured by Nihon Ventures & Poval Co., Ltd.) having a polymerization degree of 500 and a saponification degree of 98%. Thus, a coated printing paper was obtained.

[Comparative Example 1]
A coated printing paper was obtained in the same manner as in Example 1, except that the polymerization degree of polyvinyl alcohol was changed to 1000 (trade name “JM-10”, manufactured by Nippon Vinegar Poval Co., Ltd.).

[Comparative Example 2]
A coated printing paper was obtained in the same manner as in Example 1 except that the polymerization degree of polyvinyl alcohol was changed to 1700 (trade name “JM-17”, manufactured by Nippon Vinegar Poval Co., Ltd.).

[Comparative Example 3]
A coated printing paper was obtained in the same manner as in Comparative Example 1, except that the blending amounts of polyvinyl alcohol and styrene-butadiene copolymer latex were changed to 5% by mass and 15% by mass, respectively, with respect to the white pigment.

  The ISO whiteness (%), printing uniformity, and coating liquid aggregation state of Examples 1 to 4 and Comparative Examples 1 to 3 were evaluated, and the results are shown in Table 1.

Table 1

  As can be seen from Table 1, in Examples 1 to 4, the saponification degree and functional group of polyvinyl alcohol and / or its derivatives satisfy the ISO whiteness even when the functional group changes, and the printing uniformity and coating liquid aggregation state Both were good. In Comparative Examples 1 and 2, the ISO whiteness satisfies the regulation, but because the polymerization degree of polyvinyl alcohol and / or its derivative is high, the printing uniformity and the coating liquid aggregation state are poor, and the coated printing paper As the performance was insufficient. In Comparative Example 3, since the blending ratio of polyvinyl alcohol was 5% by mass, the leveling of the coating liquid was good, but the coating liquid aggregation state was poor, and the performance as a coated printing paper was insufficient. there were.

[Example 5]
A coated printing paper was obtained in the same manner as in Example 1 except that the blending amount of polyvinyl alcohol was changed to 5% by mass with respect to the white pigment.

[Example 6]
A coated printing paper was obtained in the same manner as in Example 1 except that the blending amount of polyvinyl alcohol was changed to 13% by mass with respect to the white pigment.

[Comparative Example 4]
A coated printing paper was obtained in the same manner as in Example 1 except that the blending amount of polyvinyl alcohol was changed to 2% by mass with respect to the white pigment.

[Comparative Example 5]
A coated printing paper was obtained in the same manner as in Example 1 except that the blending amount of polyvinyl alcohol was changed to 20% by mass with respect to the white pigment.

  The ISO whiteness (%), printing uniformity, and coating liquid aggregation state of Examples 5 to 6 and Comparative Examples 4 to 5 were evaluated and are shown in Table 2 together with the results of Example 1.

Table 2

  As can be seen from Table 2, Example 1, Example 5 and Example 6 satisfy the regulations, although there is a difference in ISO whiteness depending on the blending ratio of polyvinyl alcohol, and the printing uniformity, coating liquid aggregation The condition was also good. In Comparative Example 4, the blending amount of the polyvinyl alcohol in the white pigment was as small as 2% by mass, so the ISO whiteness was 98.7% which was not specified. In Comparative Example 5, the blending amount of the polyvinyl alcohol in the white pigment was Since the whiteness was 20% by mass, the ISO whiteness satisfied the regulation, but the printing uniformity was inferior, and the performance as a coated printing paper was insufficient.

[Example 7]
A coated printing paper was obtained in the same manner as in Example 1 except that the blending ratios of polyvinyl alcohol and styrene-butadiene copolymer latex were changed to 5% by mass and 15% by mass, respectively, with respect to the white pigment.

[Example 8]
A coated printing paper was obtained in the same manner as in Example 1 except that the blending amounts of polyvinyl alcohol and styrene-butadiene copolymer latex were changed to 5% by mass and 23% by mass, respectively, with respect to the white pigment.

[Comparative Example 6]
A coated printing paper was obtained in the same manner as in Example 1 except that the blending amounts of polyvinyl alcohol and styrene-butadiene copolymer latex were changed to 5% by mass and 3% by mass, respectively, with respect to the white pigment.

[Comparative Example 7]
A coated printing paper was obtained in the same manner as in Example 1 except that the blending amounts of polyvinyl alcohol and styrene-butadiene copolymer latex were changed to 5% by mass and 30% by mass, respectively, with respect to the white pigment.

  Examples 7 to 8 and Comparative Examples 6 to 7 were evaluated for ISO whiteness (%), printing uniformity, surface strength, ink set drying property, and coating liquid aggregation state, and shown in Table 3 together with the results of Example 1. It was.

Table 3

  As can be seen from Table 3, in Example 1, Example 7 and Example 8, the higher the blending amount of polyvinyl alcohol with respect to the white pigment, the higher the blending ratio in the total adhesive of the polyvinyl alcohol blending amount. The ISO whiteness was high, and a good coated printing paper was obtained, and the printing uniformity and the coating liquid aggregation state were both good. In contrast, Comparative Example 6 had a poor surface strength because the blending amount of the total adhesive in the white pigment was as small as 8% by mass. In Comparative Example 7, the amount of all adhesive in the white pigment was as large as 35% by mass, so that the ink set drying property was inferior, and the performance as a coated printing paper was insufficient.

[Example 9]
A coated printing paper was obtained in the same manner as in Example 1 except that the fluorescent whitening agent for the base paper in Example 1 was not added.

[Example 10]
Neutral paper containing calcium carbonate with kraft pulp (LBKP 90% by mass, NBKP 10% by mass) as the main component, with no addition of fluorescent whitening agent with a basis weight of 105 g / m ² , is a base paper (ISO whiteness is 92.2%). Other than this, a coated printing paper was obtained in the same manner as in Example 1.

  The ISO whiteness (%) of Examples 9 to 10 was evaluated and shown in Table 4 together with the results of Example 1.

Table 4

  As can be seen from Table 4, although Example 1 and Example 9 have a difference in ISO whiteness of the base paper, the ISO whiteness after coating is almost the same, and the ISO whiteness after coating is approximately the same. It was shown that it was not affected by the optical brightener of the base paper. In addition, Example 10 satisfied the ISO whiteness rule and showed that the papermaking method on the base paper was not affected by either acid papermaking or neutral papermaking.

The coated printing paper according to the present invention exhibits extremely high whiteness and good printing colorability, and can be preferably used as an offset coated printing paper.

Claims (2)

A coated printing paper having a coating layer containing a white pigment, an adhesive and a fluorescent brightening agent on at least one side, and polyvinyl alcohol having a polymerization degree of 800 or less and / or a derivative thereof for the white pigment. 4 to 15% by mass, the total amount of the adhesive is 10 to 30% by mass with respect to the white pigment, and the ISO whiteness specified in JIS P-8148 is 100.0% or more. Coated printing paper characterized by that. The coated printing paper according to claim 1, wherein the blending ratio of the polyvinyl alcohol and / or derivative thereof is 20% or more based on the total blending amount of the adhesive.