JP6526535B2 - Book paper - Google Patents

Description

  The present invention relates to a coated printing paper, and more particularly to a coated printing paper having a high specific volume, excellent opacity, and high whiteness.

  Coated papers for printing are used in commercial printing fields such as flyers, catalogs, brochures, book papers, publishing papers, etc., and their demand is still high. In particular, it is necessary to use lightweight paper which has high whiteness and good printing finish on book paper and publishing paper. As a technique for improving the whiteness, there is disclosed a coated paper for printing provided with a coating layer to which calcium carbonate, especially wet heavy calcium carbonate, is incorporated as a large amount as a pigment, or a fluorescent dye is added. (See, for example, Patent Document 1 and Patent Document 2).

  On the other hand, in order to reduce the weight of the paper, it is necessary to maintain a certain degree of opacity while reducing the weight by thinning the base paper and the coating layer, etc. It is an issue to prevent. As a technique for improving the opacity, a printing paper provided with a coating layer containing titanium dioxide having a high refractive index is disclosed (see, for example, Patent Document 3 and Patent Document 4). In addition, in coated paperboard using waste paper as the base paper, titanium dioxide is blended in the coated layer because the concealability of the coated layer is more required (see, for example, Patent Document 5 and Patent Document 6) ).

Unexamined-Japanese-Patent No. 2006-257590 JP, 2004-285552, A JP 2000-54288 A Unexamined-Japanese-Patent No. 2000-336593 Unexamined-Japanese-Patent No. 6-166991 gazette JP, 2006-328574, A

  However, if fluorescent dye and titanium dioxide are used together in a single coating layer to simultaneously improve the whiteness and opacity, the titanium dioxide increases the fluorescent dye because the titanium dioxide hides the fluorescence emitted from the fluorescent dye. There is a problem that the white effect is hard to appear.

  The present invention has been made focusing on the above-mentioned problems, and the object of the present invention is to provide a coated paper for printing which has both a high whiteness and a high opacity, and a further high specific volume. It is to offer.

  Other objects and effects of the present invention will be easily understood by those skilled in the art with reference to the following description.

The present invention adopts the following configuration as means for solving the problems. That is, the coated paper for printing of the present invention is a coated paper for printing having an undercoat coating layer and a top coat coating layer on at least one surface of a base paper mainly comprising pulp, The working layer contains a binder and 0.2 to 0.8 g / m ² of titanium dioxide per side of the base paper, and the top coating layer contains kaolin as a pigment and heavy calcium carbonate, A binder and a fluorescent whitening agent are contained, and 8 to 20% by mass of the pulp is mechanical pulp, and the coating amount of the top coat is 4.5 to 7 per side of the base paper. It is 0 g / m ² , and the total coating amount of the undercoating layer and the topcoating layer is 5.5 to 9.0 g / m ² per one side of the base paper.

  Titanium dioxide improves the opacity of coated paper by blending it in the coated layer due to its high hiding power, but when it is blended in the same coating layer as the fluorescent brightener, the fluorescent brightener The fluorescent whitening effect of Therefore, in the present invention, the fluorescent whitening agent for enhancing the whitening effect is added to the top coat layer as the outermost layer, and the titanium dioxide having excellent hiding power is added only to the undercoat layer.

  In addition, by making 8 to 20% by mass of the base paper pulp mechanical pulp, the specific volume of the base paper is improved, and the opacity of the base paper itself is improved as compared with the case where only chemical pulp is blended. Can. By improving the opacity of the base paper itself, sufficient opacity can be obtained for the coated coated paper as a whole, even if the opacity of the coated layer is not so high.

  In addition, by simultaneously using kaolin and ground calcium carbonate in the top coat, the opacity and the whiteness can be simultaneously improved. The composition of the base paper, the composition of the undercoat coating layer, and the composition of the top coat layer provide a coated coated paper that simultaneously satisfies the opacity and the whiteness.

  In a preferred embodiment of the present invention, the top coat may contain 60 to 85% by mass of kaolin and 15 to 40% by mass of ground calcium carbonate based on 100% by mass of the pigment.

  According to such a configuration, since the blend ratio of kaolin and heavy calcium carbonate is preferable, even when the coating amount of the top coat layer is relatively small, the opacity and the whiteness are balanced. It can be improved well.

In a preferred embodiment of the present invention, the basis weight of the base paper may be 35 to 65 g / m ² .

  According to such a configuration, since the base paper itself is relatively light, it is also light as coated paper for printing, and a coated paper for printing excellent in opacity and whiteness can be obtained.

  In a preferred embodiment of the present invention, the mechanical pulp may include chemithermomechanical pulp or bleached chemithermomechanical pulp.

  According to such a configuration, the specific volume of the base paper can be easily improved by using the chemithermomechanical pulp as the mechanical pulp, and the whiteness can be improved in addition to the specific volume by using the bleached chemithermomechanical pulp. Therefore, the opacity and whiteness of the base paper itself are further improved, and the opacity and whiteness of the coated paper for printing itself are also improved.

  In a preferred embodiment of the present invention, the addition amount of the binder in the undercoat coating layer may be in the range of 90 to 300 parts by mass with respect to 100 parts by mass of the pigment in the undercoat coating layer.

  According to such a configuration, since the blending ratio of the pigment and the binder in the undercoat coating layer is an appropriate ratio, an undercoat coating layer in which the balance between the surface strength and the opacity is achieved can be obtained.

  In a preferred embodiment of the present invention, the addition amount of the binder in the top coat may be in the range of 4 to 20 parts by mass with respect to 100 parts by mass of the pigment in the top coat.

  According to such a configuration, since the blending ratio of the pigment and the binder in the top coat is in an appropriate range, a top coat with a balance between strength and printability can be obtained.

  In a preferred embodiment of the present invention, the fluorescent whitening agent may be contained in an amount of 0.05% by mass or more based on the entire topcoat coated layer.

  According to such a configuration, a coated coated paper having higher whiteness and visual whiteness can be obtained.

In a preferred embodiment of the present invention, the specific volume of the coated printing paper may be 1 cm ³ / g or more. According to such a configuration, a coated paper for printing more excellent in opacity can be obtained.

  Moreover, this invention can be grasped also as invention regarding the manufacturing method of the coated paper for printing.

In the method for producing a coated paper for printing according to the present invention, a step of preparing a base paper containing 8 to 20% by mass of mechanical pulp based on the total amount of pulp, a binder on at least one surface of the base paper, Applying a coating solution for undercoat coating layer containing 0.2 to 0.8 g / m ² of titanium dioxide per one side of the base paper to provide an undercoat coating layer, the undercoat coating layer Coating a coating liquid for top coat coating layer containing kaolin and ground calcium carbonate as a pigment, a binder and a fluorescent whitening agent on the surface of Providing a top coat of 0 g / m ² . Moreover, the total coating amount of the said undercoat coating layer and top-coat coating layer is 5.5-9.0 g / m < ² > per single side | surface of base paper.

  According to such a configuration, coated printing paper having an excellent balance of opacity and whiteness can be easily manufactured.

  According to the coated paper for printing of the present invention, high opacity and whiteness can be simultaneously satisfied, and further, a relatively lightweight coated paper for printing having a high specific volume can be obtained.

It is a graph (the 1) which shows the composition of the coated paper for printing in an Example and a comparative example. It is a graph (the 2) which shows the composition of the coated paper for printing in an Example and a comparative example. It is a graph (the 1) which shows the physical property of the coated paper for printing by an Example and a comparative example. It is a graph (the 2) which shows the physical property of the coated paper for printing by an Example and a comparative example.

As described above, the coated paper for printing according to the present invention has the undercoat coating layer and the top coat coating layer on at least one surface of the base paper composed mainly of pulp, The undercoat coating layer contains a binder and 0.2 to 0.8 g / m ² of titanium dioxide per one side of the base paper, and the top coat coating layer contains kaolin and heavy pigment as a pigment. Calcium carbonate, a binder, and a fluorescent whitening agent are contained, and 8 to 20% by mass of the pulp is mechanical pulp, and the coating amount of the top coating layer is 4. per one side of the base paper. It is 5-7.0 g / m < ² >, and the total coating amount of the said undercoat coating layer and the said top-coat coating layer is 5.5-9.0 g / m < ² > per single side | surface of base paper.

  Here, as the base paper used for the coated paper for printing of the present invention, one mainly containing pulp is used, and chemical pulp, mechanical pulp, waste paper recovery pulp, etc. can be used as the raw material pulp. On the other hand, 8 to 20% by mass of mechanical pulp is contained. By containing mechanical pulp, the specific volume of the base paper can be increased. Furthermore, as the specific volume is improved, the opacity can be improved as compared to the case where only chemical pulp is blended. Examples of mechanical pulp include groundwood pulp (GP), refiner mechanical pulp (RGP), thermomechanical pulp (TMP), and chemithermomechanical pulp (CTMP), and in particular, CTMP that contributes to improvement of specific volume is preferable. Furthermore, it is preferable to use bleached chemithermomechanical pulp (BCTMP) in which CTMP is bleached, since the specific volume and the whiteness can be simultaneously improved. When the content of mechanical pulp is less than 8% by mass, the improvement effect of the specific volume is poor, and when it exceeds 20% by mass, the specific volume is further improved but it becomes easy to fade and the surface property of coated paper for printing is significantly reduced. Impairing the suitability as printing paper.

  In the present invention, the base paper may optionally contain known papermaking additives such as sizing agents, coloring dyes, paper strengthening agents, fillers and the like. In order to increase the specific volume of the base paper, it is desirable to keep the blending amount of the filler in the base paper to 4 to 10% by mass. The base paper can be made using a known paper machine such as a Fourdrinier paper machine, an on-top former, a hybrid former, or a gap former.

In the present invention, the basis weight of the base paper is not particularly limited, but the effects of the present invention become remarkable when the base paper is lightweight, and become particularly remarkable when 35 to 65 g / m ² . That is, according to the configuration of the present invention, high opacity and whiteness are imparted by the base paper containing 8 to 20% by mass of mechanical pulp, and the two coated layers of the top coat coated layer and the undercoat coat layer. Therefore, even if the basis weight of the base paper is relatively light weight of about 35 to 65 g / m ² , the coated paper for printing having sufficient opacity and whiteness can be obtained.

  In the coated paper for printing of the present invention, an undercoat coating layer is provided on at least one surface of a base paper, and an overcoating layer is provided on the surface of the undercoat coating layer. As mentioned above, the undercoat coating layer contains titanium dioxide as a pigment. Titanium dioxide is conventionally used as a pigment with excellent opacity for papermaking, and particularly rutile or anatase titanium dioxide has been widely used. The titanium dioxide used in the present invention is not particularly limited, but it is preferable to use rutile type titanium dioxide having a small residue when made into a slurry and having higher hiding power.

With regard to the undercoat coating layer, the coating amount of the coating liquid for the undercoat coating layer and the blending amount of titanium dioxide so that the coating amount of titanium dioxide per one side of the base paper is 0.2 to 0.8 g / m ² Adjust the amount of work. When the coating amount of titanium dioxide is less than 0.2 g / m ² , the effect of improving the opacity of the coated paper for printing can not be sufficiently obtained. Conversely, even if the coating amount of titanium dioxide is increased to more than 0.8 g / m ² , in addition to the effect of improving the opacity being small, there is also a negative effect that the strength of the coated layer is reduced. There is also a problem that the cost increases due to the addition.

  In the coated paper for printing of the present invention, the undercoat coating layer can contain other pigments different from titanium dioxide as long as the intended effects are not impaired. As other pigments, inorganic pigments such as kaolin, calcined kaolin, light calcium carbonate, heavy calcium carbonate and talc, and organic pigments such as plastic pigments can be used. That is, in the undercoat coating layer, titanium dioxide and one or more other pigments may be used in combination.

  In addition to the pigment such as titanium dioxide, a binder is added to the undercoat coating layer. The binder used here is not particularly limited, and starches such as thermochemically modified starch, starch oxide, phosphate esterified starch, polyvinyl alcohol resins, polyacrylamide resins, acrylic resins, styrene-butadiene resins And the like can be appropriately selected and used as the known binder used for the coating layer of the printing coated paper.

Although the content of the binder in the undercoat coating layer is not particularly limited, it is preferable to use the binder in a range of 90 to 300 parts by mass with respect to 100 parts by mass of the pigment, and in the range of 100 to 250 parts by mass. More preferable. When the coating amount of titanium dioxide is in the range of 0.2 to 0.8 g / m ² , by using a relatively large amount of binder in the undercoat coating layer, the coating amount of the undercoat coating layer is relatively It can be reduced. Here, when the blending amount of the binder in the undercoat coating layer is less than 90 parts by mass, the coating amount of the binder itself is reduced, and the surface strength of the coated paper for printing may be reduced. On the other hand, if the blending amount of the binder in the undercoat coating layer exceeds 300 parts by mass, the excess binder component fills the voids of the base paper, and the opacity of the base paper portion tends to decrease, and the entire coated paper for printing There is also a possibility that the opacity of the In addition, as a binder used at this time, since there is no concern about mechanical stability and surface strength is likely to be improved, phosphated starch is preferable.

The coating amount of the undercoat coating layer is preferably in the range of 0.5 to 3.0 g / m < ² > per one side, and more preferably in the range of 1.0 to 2.0 g / m < ² >. When the coating amount of the undercoat coating layer is less than 0.5 g / m ² , the surface strength of the coated paper for printing may not be sufficiently obtained. In addition, when the coating amount of the undercoat coating layer exceeds 3.0 g / m ² , the coating stability particularly in a film transfer type coater such as a gate roll is easily lost, and uniform coating amount coating is performed. There is a possibility that a layer can not be obtained.

  In the present invention, the undercoat coating layer further contains a dispersant, an antifoamer, a thickener, a water retention agent, a water resistant agent, a coloring agent, a sizing agent, and a paper strength, as long as the effects of the present invention are not impaired. You may contain well-known papermaking additives, such as an agent. If necessary, a fluorescent whitening agent may be contained, but as described above, the high whitening properties of titanium dioxide inhibit the fluorescent whitening effect, so even if a fluorescent whitening agent is added to the undercoat coating layer It is difficult to obtain the expected whitening effect. In the present invention, by containing the fluorescent whitening agent in the top coat, it is possible to obtain high whiteness without containing the fluorescent whitening agent in the undercoat, so from the viewpoint of cost control. It is preferable that the undercoat coating layer does not contain a fluorescent whitening agent.

  In the present invention, the formation of the undercoating coating layer can be provided by applying a coating liquid for the undercoating coating layer on a base paper and drying it. The coating method is not particularly limited, and a known transfer machine such as a film transfer type coating method such as a gate roll coater or a metalling size press, an air knife coater, a blade coater, a bar coater etc. It can be suitably adopted according to the property of the working fluid.

  Next, the top coat layer will be described. The coated paper for printing of the present invention is provided on the undercoat coating layer with an overcoat coating layer containing a pigment, a binder and a fluorescent brightening agent.

  In the present invention, the overcoat layer contains kaolin and ground calcium carbonate as pigments. By including these pigments in the coating layer, kaolin contributes to the improvement of the opacity, and it is known that the heavy calcium carbonate contributes to the improvement of the whiteness, and the kaolin and the heavy weight are added to the overcoat coating layer. By containing calcium carbonate, opacity and whiteness can be simultaneously improved. The higher the proportion of kaolin in the pigment contained in the top coat layer, the higher the opacity, and the higher the proportion of one of the calcium carbonates, the higher the whiteness.

  In the present invention, the ratio of kaolin to calcium carbonate in the pigment contained in the top coat is not particularly limited, but 60 parts of kaolin is contained in 100 parts by mass of the pigment contained in the top coat. It is preferable to adjust the amount of heavy calcium carbonate to 15 to 40 parts by mass. By blending in such a range, the coated amount of the top coat can relatively improve at least the opacity and the whiteness in a well-balanced manner.

  In the present invention, the overcoating layer may contain other pigments different from kaolin and ground calcium carbonate, as long as the effects aimed by the present invention are not impaired. Here, examples of other pigments include inorganic pigments such as calcined kaolin, light calcium carbonate and talc, and organic pigments such as plastic pigments. As described above, titanium dioxide is not contained in the top coat layer because it interferes with the whitening effect of the fluorescent whitening agent.

  In the present invention, the top coat layer contains a binder. The binder to be contained in the top coat layer is not particularly limited, and the coating layer of a printing coated paper such as starch, polyvinyl alcohol resin, polyacrylamide resin, acrylic resin, styrene-butadiene resin, etc. The known binder used for can be used.

  The content of the binder in the top coat is preferably in the range of 4 to 20 parts by mass, and more preferably in the range of 5 to 15 parts by mass with respect to 100 parts by mass of the pigment in the top coat. The range of 6 to 13 parts by mass is more preferable. If the blending amount of the binder is less than 4 parts by mass, the strength of the top coat may not be sufficiently obtained, and the printing strength may be insufficient. On the other hand, when the blending amount of the binder exceeds 20 parts by mass, the blending ratio of the pigment may be relatively lowered, which may impair the printing suitability such as the ink receptivity and the drying property.

  In the present invention, the top coat layer contains a fluorescent whitening agent. The fluorescent whitening agent to be contained in the top coat layer is not particularly limited, but a fluorescent dye is preferable, and stilbene type, coumarin type, pyrazoline type, naphthalimide type, benzoxazole type, imidal type, thiazole type, It is possible to use the conventionally used ones of the distyrylbiphenyl type. For example, stilbene-based compounds containing one or more sulfonic acid groups. Examples of stilbene-based compounds include diaminostilbene-disulfonic acid derivatives, and due to the selection of a solubilizing agent, the number of sulfonic acid groups, etc., many fluorescent dyes developed for coating applications with high dispersibility are commercially available. Such products include, for example, Leukophor (Leucophor (registered trademark)) series (manufactured by Clariant Japan), and Keikol (KAYCOLL (registered trademark)) series (manufactured by Nisshin Shoji Co., Ltd.).

  In the present invention, the content of the fluorescent whitening agent in the overcoating layer is not particularly limited, but is preferably 0.05% by mass or more based on the total amount of the overcoating layer, more preferably 0. It is 1% by mass or more, more preferably 0.3% by mass or more. Although the upper limit of the addition amount is not particularly limited, it is not less than 1.0% by mass with respect to the top coat layer, since excessive addition may not only cause the fluorescence intensity to plateau but also to increase fading. It is preferable to By incorporating a fluorescent whitening agent in the top coat, higher whiteness and visual whiteness can be improved.

  In the present invention, the top coat layer further contains a dispersant, an antifoamer, a thickener, a water retention agent, a water resistant agent, a coloring agent, a pH adjuster, to the extent that the effects of the present invention are not impaired. And the like may be contained.

  The top coat layer can be provided by applying a coating solution for the top coat layer on the surface of the undercoat coat layer provided on the base paper and drying it. It does not specifically limit as a coating method of the coating liquid for top-coat coating layers, Although well-known coating machines, such as an air knife coater, a blade coater, a bar coater, are employable, a blade coater is preferable.

In the present invention, the coating amount of the top coat layer is 4.5 to 7.0 g / m ^{2 in} terms of solid content per one side of the base paper. By setting the coating amount to such a range, the specific volume of the coated paper for printing can be increased while satisfying the printability as the coated paper for printing such as surface strength. If the coating amount of the top coat layer is less than 4.5 g / m ² , the base paper (surface of the undercoat layer) can not be sufficiently concealed, and the opacity and the whiteness are not only inferior but also the surface strength is insufficient. I can not satisfy the print aptitude. Conversely, if the coating amount of the top coat exceeds 7.0 g / m ² , the proportion of the coat having a higher density than the base paper increases, so the specific volume decreases in inverse proportion to the density, and the coating for printing It becomes difficult to increase the specific volume of paper.

In the present invention, the total coating amount of the undercoat coating layer and the top coat layer is 5.5 to 9.0 g / m ^{2 in} terms of solid content per one side of the base paper. Preferably it is 7.0-8.0 g / m < ² >. If the total coating amount of the undercoat coating layer and the topcoat coating layer is less than 5.5 g / m ² , the base paper can not be sufficiently concealed by the coating layer, and not only inferior in opacity and whiteness, but also surface strength Insufficient to meet printability. Conversely, if the total coating amount exceeds 9.0 g / m ² , the proportion of the coated layer having a higher density than the base paper increases, so the specific volume decreases in inverse proportion to the density, and the ratio of coated paper for printing The volume will be low.

  In the present invention, when the undercoating coating layer and the topcoating layer are provided on both sides, the coating amount of each coating layer and the total coating amount of both layers may be made different in the above-mentioned range. . In particular, since the smoothness of the paper made by a part of the papermaking machines tends to differ between the front and back, when using such a papermaking machine, the physical properties of the front and back sides are different by making the coating amount of the front and back different. Difference can be reduced.

  The coated paper for printing according to the present invention may be smoothed by a calendar. Here, the method of smoothing treatment is not particularly limited, and the smoothing treatment can be performed using a known calendar such as a super calender or a soft nip calendar.

The coated paper for printing according to the present invention is a coated paper for printing, which has high whiteness, opacity and specific volume. The whiteness is preferably 81.5% or more as ISO whiteness, and 91% or more according to JIS P 8149 as an index of opacity. Although the specific volume varies depending on the basis weight of the base paper, the specific volume is preferably 1.00 cm ³ / g or more if the basis weight of the base paper is in the range of 35 to 65 g / m ² . In addition, if the fluorescence intensity is 0.6 or more, it is considered that the whiteness of the appearance is sufficient.

  EXAMPLES The present invention will next be described in more detail by way of examples, which should not be construed as limiting the invention thereto. Moreover, unless otherwise indicated, "part" and "%" in an example show a "mass part" and "mass%", respectively. In addition, the addition part number is a value of solid content conversion.

Example 1
<Production of base paper>
80 parts of hardwood bleached kraft pulp (LBKP) with 400 mL of freeness (CSF), 10 parts of softwood bleached kraft pulp (NBKP) with 550 mL of freeness (CSF), and 500 mL of hardwood with CSF freeness (CSF) 10 parts of bleached chemithermomechanical pulp (BCTMP) is dispersed in water to make a pulp slurry, and 5 parts of light calcium carbonate (TP121S: manufactured by Okutama Industrial Co., Ltd.) as a filler in the pulp slurry, 1 part of sulfuric acid band, and paper strength A stock prepared by adding 0.6 parts of cationic starch (Kate 308: manufactured by Nippon NSC Co., Ltd.) and 0.01 part of a retention aid (High Holder 220: manufactured by Kurita Kogyo Co., Ltd.) as an Papermaking was carried out with a paper machine having a hybrid former to obtain a base paper having a basis weight of 56 g / m ² .

Preparation of Coating Liquid for Undercoat Coating Layer
100 parts of titanium dioxide (PFC-503: manufactured by Ishihara Sangyo Co., Ltd.) as a pigment and 200 parts of phosphated starch esterified starch (MS # 4600: manufactured by Japan Food Processing Co., Ltd.) gelatinized as a binder are dispersed in water and mixed A coating solution for undercoat layer having a solid content concentration of 18% was prepared.

<Preparation of Coating Liquid for Top Coating Layer>
70 parts of kaolin (DB Glaze: made by Imeris) and 30 parts of wet heavy calcium carbonate (Carbital 90: made by Imerys) as a pigment, 0.1 part of sodium polyacrylate as a dispersant, styrene-butadiene copolymer latex as a binder (2788 K: manufactured by JSR Corporation) 10 parts and gelatinized phosphate esterified starch (MS # 4600: manufactured by Japan Food Processing Co., Ltd.) 1 part, fluorescent whitening agent (Sun White BUL-TC-H: manufactured by Sunrise Chemical Co., Ltd.) 0.3 parts was disperse | distributed and mixed in water, and solid content concentration prepared the coating liquid for top coat coating layers of 60 mass%.

<Creation of coated paper for printing>
The coating solution for the undercoating layer is coated on both sides of the base paper with a gate roll coater so that the coating amount per one side is 1.5 g / m ^{2 in} terms of solid content, dried and coated with the undercoating layer. Construction layer was provided. Then, on both surfaces of the undercoat coating layer provided on both sides of the base paper, the coating liquid for top coat coating layer is 5.0 g / m ² on one side (front side) and 6 on the other side (back side) .0g / m ² respectively applied, it was coated with a blade coater so as coating amount of double-sided is 11.0 g / m ² in terms of solid content, provided dried overcoat coating layer. It was then processed with a soft nip calender to achieve the desired smoothness. The above steps are carried out with a so-called on-machine coater in which the steps from the papermaking process of the base paper to the coating and drying processes of the undercoating layer and the topcoating layer are integrated to form a target coated paper for printing. Obtained.

(Example 2)
In the production of base paper, the blending of pulp into pulp slurry is as follows: 72 parts of hardwood bleached kraft pulp (LBKP) with 400 mL freeness (CSF), softwood bleached kraft pulp (NBKP) with freeness (CSF) 550 mL A coated paper for printing was obtained in the same manner as in Example 1 except that 10 parts and the freeness (CSF) was changed to 500 parts of a broadleaf tree bleached chemithermomechanical pulp (BCTMP) 18 parts.

(Example 3)
In the production of the base paper, the basis weight of the base paper was changed to 54 g / m ² , and in the preparation of the coating liquid for undercoating, gelatinized phosphated starch which was a binder (MS # 4600: manufactured by Nippon Food Processing Co., Ltd.) The amount of the coating is changed to 100 parts, and in the preparation of the coated paper for printing, the coating amount of the coating liquid for top coating layer is 6.0 g / m ² on one side (surface), the other side Coated paper for printing in the same manner as in Example 1 except that the back surface was changed to 7.0 g / m ² and the coating amount on both sides was changed to 13.0 g / m ² in terms of solid content. I got

(Example 4)
In the production of the base paper, the basis weight of the base paper is changed to 58 g / m ² , and in the preparation of the coated paper for printing, the coating amount of the coating liquid for the undercoat coating layer is converted in terms of solid content per one side. Change the coating amount to 1.0 g / m ² and apply 4.5 g / m ² to one side (front side) of the coating liquid for top coat layer and 5.5 g / m ^{2 to} the other side (back side) ^A coated paper for printing was obtained in the same manner as in Example 1 except that the coating amount was changed to ² and the coating amount on both sides was changed to 10.0 g / m ² in terms of solid content.

(Comparative example 1)
A coated paper for printing was obtained in the same manner as in Example 1 except that titanium dioxide (PFC-503: manufactured by Ishihara Sangyo Co., Ltd.) was not blended in the preparation of the coating solution for the undercoat coating layer.

(Comparative example 2)
In the production of base paper, the blending of pulp into pulp slurry was carried out using 85 mL of hardwood bleached kraft pulp (LBKP) with 400 mL freeness (CSF) and softwood bleached kraft pulp (NBKP) with 550 mL freeness (CSF) A coated paper for printing was obtained in the same manner as in Example 1 except that 10 parts and the freeness (CSF) was changed to 500 parts of a hardwood bleached chemithermomechanical pulp (BCTMP) of 500 mL.

(Comparative example 3)
The same method as in Example 1 except that the addition amount of gelatinized phosphated starch (MS # 4600: manufactured by Japan Food Processing Co., Ltd.), which is a binder, was changed to 50 parts in the preparation of the coating liquid for undercoating. Coated paper for printing.

(Comparative example 4)
In the production of base paper, the blending of pulp into pulp slurry was 78 parts of hardwood bleached kraft pulp (LBKP) with 400 mL freeness (CSF) and softwood bleached kraft pulp (NBKP) with 550 mL freeness (CSF) A coated paper for printing was obtained in the same manner as in Example 1 except that 10 parts and the freeness (CSF) was changed to 500 parts of a broadleaf tree bleached chemithermomechanical pulp (BCTMP) 22 parts.

(Comparative example 5)
In the production of the base paper, the basis weight of the base paper is changed to 60 g / m ² , and in the preparation of the coated paper for printing, the coating amount of the coating liquid for top coat layer is 3 on one side (surface) Example 1 except that 0. 0 g / m ² and the other side (rear surface) were changed to 4.0 g / m ² , and the coating amount on both sides was changed to 7.0 g / m ² in terms of solid content A coated paper for printing was obtained in the same manner as in.

(Comparative example 6)
In the production of the base paper, the basis weight of the base paper is changed to 50 g / m ² , and in the preparation of the coated paper for printing, the coating amount of the coating liquid for top coat layer is on one side (surface) 8 .0g / m ^2, except that changed on the other surface (back surface) to 9.0 g / m ^2, was changed coating amount of double-sided in terms of solid content to 17.0 g / m ^2, example 1 A coated paper for printing was obtained in the same manner as in.

  The structure and evaluation result of the coated paper for printing in each Example and a comparative example are shown in FIGS. In addition, about the evaluation in a table | surface, it performed with the following method.

<ISO Whiteness>
According to JIS P 8148, it measured about the front and back both sides of the coated paper for printing.

<ISO opacity>
It measured according to JISP 8149.

<Decoloration>
The surface of the coated layer of the coated printing paper was irradiated with light for 60 minutes using an Acme fading tester, and the reduction in ISO whiteness before and after the light irradiation was calculated by the following formula 1.
Formula 1: Decolorization (%) = (pre-illumination ISO whiteness−post-illumination ISO whiteness) / pre-illumination ISO whiteness × 100

<Smoothness>
According to JIS P 8155, it measured about the front and back both sides of the coated paper for printing.

<Pressure resistance>
Using an RI printer (manufactured by Akira MFG. Co., Ltd.), 0.4 g of black ink with a tack value of 15 (trade name: TV-15, manufactured by Toyo Ink) is kneaded at a temperature of 30 ° C., and pressed onto the surface of coated paper for printing Printing was carried out three times under the condition of a cylinder rotational speed of 60 rpm, and the degree of peeling of the surface of the coated layer was visually evaluated.
○: almost no peeling, good △: peeling slightly noticeable, not possible ×: noticeable with a lot of peeling, not possible

<Up printing>
The coated paper for printing is cut to a predetermined size, and 1,000 sheets are collected, and printed on the back side of the coated paper for printing by the Mitsubishi Heavy Industries offset printing machine Lithopia 4C at a speed condition of 9,000 sheets / hour. The occurrence of ink collapse and white spots was visually evaluated. After printing refers to the occurrence of ink flutter and white spots.
○: Good ink collapse and no white spots occurred. Good Δ: Poor ink collapse a little, white spots occurred a little, not possible ×: Poor ink collapse and a white spots occurred Yes, no

<Printing feeling>
The coated paper for printing is cut to a predetermined size, and 1,000 sheets are collected, and printed on the back side of the coated paper for printing by the Mitsubishi Heavy Industries offset printing machine Lithopia 4C at a speed condition of 9,000 sheets / hour. The print feeling was visually evaluated. The evaluation of the printing feeling is made on the basis of the presence or absence of the feeling that the fibers unique to mechanical pulp appear to be lifted.
○: There is no feeling that the fibers appear to be lifted and good. :: A feeling that the fibers are slightly lifted and not good ×: A feeling that the many fibers are lifted and not good

  As is clear from FIG. 1, the coated papers for printing obtained in Examples 1 to 4 have high whiteness, opacity and specific volume, and furthermore, the decolorization, the printing durability and the printing up And it was excellent also about any of a printing feeling.

  On the other hand, the coated printing paper obtained by Comparative Example 1 was inferior in opacity. It is considered that this is because the undercoat coating layer does not contain titanium dioxide.

  Moreover, the coated paper for printing obtained by the comparative example 2 was inferior to the opacity probably because the specific volume was low. It is considered that this is because the specific volume is reduced because the proportion of BCTMP in the base paper is small, and the opacity is also reduced as the specific volume is reduced.

  The coated printing paper obtained in Comparative Example 3 had many peelings on the surface of the coated layer and was inferior in press life. It is considered that this is because the blending amount of the binder is relatively small because the blending amount of titanium dioxide in the undercoat coating layer is too large, and the strength of the coating layer is reduced.

  The coated printing paper obtained in Comparative Example 4 had a large value of decolorization, and furthermore, was inferior in print rise and print appearance. It is considered that this is because discoloration occurs easily because the proportion of BCTMP in the base paper is too high, and the surface property is also deteriorated.

  The coated paper for printing obtained by Comparative Example 5 was inferior in the opacity and further inferior in the print appearance. It is considered that this is because the coating amount of the top coat layer is small, the opacity is reduced, and the surface strength is also reduced, so that the printability is deteriorated.

  The coated paper for printing obtained by Comparative Example 6 was a coated paper for printing having a low specific volume. This is considered to be caused by the fact that the coating amount of the top coat layer is too large.

Claims (8)

A coated printing paper having an undercoat coating layer and a top coat coating layer on at least one surface of a base paper mainly comprising pulp,
The undercoat coating layer contains a binder and 0.2 to 0.8 g / m ² of titanium dioxide per side of the base paper,
The top coat layer contains kaolin and ground calcium carbonate as a pigment, a binder, and a brightening agent,
8 to 20% by mass of the pulp is mechanical pulp,
The coating amount of the top coat layer is 4.5 to 7.0 g / m ² per one side of the base paper,
The total coating amount of the undercoat coating layer and the topcoat coating layer, Ri per side 5.5~9.0g / m ² der the base paper,
Books paper said fluorescent whitening agent is characterized that you have included 0.05 mass% or more relative to the entire top coat coating layer. The book paper according to claim 1, wherein 60 to 85% by mass of kaolin and 15 to 40% by mass of ground calcium carbonate are contained with respect to 100% by mass of the pigment in the top coat layer. The paper weight of the said base paper is 35-65 g / m < ² >, The book paper of Claim 1 characterized by the above-mentioned. The book paper according to claim 1, wherein the mechanical pulp comprises chemithermomechanical pulp or bleached chemithermomechanical pulp. The undercoat coating layer amount of binder in the books sheet according to claim 1, characterized in that in the range of 90 to 300 parts by weight per 100 parts by weight pigment in the undercoat coating layer. Books sheet according to claim 1, the addition amount of the binder of the topcoat coating layer, characterized in that it is in the range of 4 to 20 parts by weight per 100 parts by weight pigment in the topcoat coating layer. A specific volume is 1.00 cm < ³ > / g or more, The book paper of Claim 1 characterized by the above-mentioned. Providing a base paper containing 8 to 20% by mass of mechanical pulp relative to the total amount of pulp;
A coating solution for an undercoat coating layer containing a binder and 0.2 to 0.8 g / m ² of titanium dioxide per side of the base paper is applied to at least one surface of the base paper to perform undercoating Providing a coating layer,
A coating solution for top coating layer containing kaolin as pigment, heavy calcium carbonate, a binder, and a fluorescent whitening agent is coated on the surface of the undercoat layer, and the surface of the base paper is coated. Providing a top coat layer of 4.5 to 7.0 g / m ² ;
The total coating amount of the undercoat coating layer and the topcoat coating layer, Ri per side 5.5~9.0g / m ² der the base paper,
The fluorescent whitening agent, the method of manufacturing book paper characterized that you have included 0.05 mass% or more relative to the entire top coat coating layer.

Images