JP2017061760A - Coated paper for printing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coated paper for printing, which satisfies both high whiteness and high opacity and has a high specific volume.SOLUTION: The coated paper for printing has an undercoating layer and a top coating layer on at least one side of a base paper composed mainly of pulp. The coated paper for printing is characterized in that: the undercoating layer contains a binder and 0.2-0.8 g/mof titanium dioxide per side of the base paper; the top coating layer contains kaolin and heavy calcium carbonate as pigments, a binder, and a fluorescent brightener; 8-20 mass% of the pulp is mechanical pulp; a coating amount of the top coating layer is 4.5-7.0 g/mper side of the base paper; and the total coating amount of the undercoating layer and the top coating layer is 5.5-9.0 g/mper side of the base paper.SELECTED DRAWING: Figure 4

Description

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

  Coated paper for printing is used in commercial printing fields such as flyers, catalogs, brochures, book papers, and publishing papers, and the demand is still high. In particular, book paper and publishing paper require lightweight paper with high whiteness and good print finish. As a technique for improving the whiteness, a coated paper for printing provided with a coating layer containing a large amount of calcium carbonate, particularly wet heavy calcium carbonate as a pigment, or a fluorescent dye added is disclosed. (For example, see Patent Document 1 and Patent Document 2).

  On the other hand, when reducing the weight of paper, it is necessary to maintain a certain level of opacity while reducing the weight by reducing the thickness of the base paper or coating layer. Prevention is a challenge. As a technique for improving opacity, a printing paper provided with a coating layer containing titanium dioxide having a high refractive index is disclosed (for example, see Patent Document 3 and Patent Document 4). Moreover, in the coated paperboard which uses a waste paper for a base paper, since the concealability of a coating layer is needed more, titanium dioxide is mix | blended with the coating layer (for example, refer patent document 5 and patent document 6). ).

JP 2006-257590 A JP 2004-285552 A JP 2000-54288 A JP 2000-336593 A JP-A-6-166991 JP 2006-328574 A

  However, if fluorescent dye and titanium dioxide are used together in a single coating layer in order to improve whiteness and opacity at the same time, titanium dioxide will conceal the fluorescence emitted by the fluorescent dye, increasing the fluorescent dye. There is a problem that the white effect is hardly exhibited.

  The present invention has been made paying attention to the above-mentioned problems, and the object of the present invention is to provide a coated paper for printing that has both high whiteness and high opacity, and has a high specific volume. It is to provide.

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

The present invention adopts the following configuration as means for solving the problems. That is, the printing coated paper of the present invention is a printing coated paper having an undercoat coating layer and an overcoat coating layer on at least one surface of a base paper having pulp as a main component. The work 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 coat layer contains kaolin and heavy calcium carbonate as pigments, A binder and a fluorescent brightening agent are contained, 8 to 20% by mass of the pulp is mechanical pulp, and the coating amount of the top coat layer is 4.5 to 7 per side of the base paper. was 0 g / m ^2, the total coating amount of the undercoat coating layer and the topcoat coating layer, characterized in that it is a single-sided per 5.5~9.0g / m ² base paper.

  Due to its high concealability, titanium dioxide improves the opacity of the coated paper by blending it into the coating layer, whereas when blended in the same coating layer as the fluorescent brightener, the fluorescent brightener This impairs the fluorescent whitening effect. Therefore, in the present invention, the fluorescent whitening agent that enhances the whitening effect is blended in the top coat layer that is the outermost layer, and titanium dioxide that is excellent in hiding properties is blended only in the undercoat layer.

  In addition, the specific volume of the base paper is improved by using 8 to 20 mass% of the pulp of the base paper as a mechanical pulp, and the opacity of the base paper itself is improved as compared with the case where only chemical pulp is blended. Can do. By improving the opacity of the base paper itself, sufficient opacity can be obtained for the printing coated paper as a whole, without increasing the opacity of the coating layer so much.

  Further, by using kaolin and heavy calcium carbonate in the top coat layer, the opacity and whiteness can be improved at the same time. With the configuration of the base paper, the configuration of the undercoat coating layer, and the configuration of the topcoat coating layer, a coated paper for printing that satisfies both opacity and whiteness at the same time is obtained.

  In a preferred embodiment of the present invention, the top coat layer may contain 60 to 85% by weight of kaolin and 15 to 40% by weight of heavy calcium carbonate with respect to 100% by weight of the pigment.

  According to such a configuration, since the blending 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 whiteness are balanced. It can be improved well.

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

  According to such a configuration, since the base paper itself is relatively light, it is possible to obtain a coated paper for printing that is lightweight as a coated paper for printing and excellent in opacity and whiteness.

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

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

  In preferable embodiment of this invention, the range of 90-300 mass parts may be sufficient as the addition amount of the binder in the said undercoat coating layer with respect to 100 mass parts of pigments in an undercoat coating layer.

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

  In preferable embodiment of this invention, the range of 4-20 mass parts with respect to 100 mass parts of pigments in an overcoat coating layer may be sufficient as the addition amount of the binder in the said topcoat coating layer.

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

  In preferable embodiment of this invention, the said optical brightener may be contained 0.05 mass% or more with respect to the whole topcoat coating layer.

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

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

  The present invention can also be understood as an invention relating to a method for producing a coated paper for printing.

The method for producing a coated paper for printing according to the present invention includes a step of preparing a base paper containing 8 to 20% by mass of mechanical pulp with respect to the total amount of pulp, a binder on at least one surface of the base paper, A step of applying an undercoat coating layer coating solution containing 0.2 to 0.8 g / m ² of titanium dioxide per side of the base paper to provide an undercoat coating layer; and the undercoat coating layer Is coated with a coating liquid for a top coat layer containing kaolin and heavy calcium carbonate, a binder, and a fluorescent brightening agent as pigments, and 4.5 to 7 per side of the base paper. Providing a top coat layer of 0.0 g / m ² . Further, the total coating amount of the undercoat coating layer and the topcoat coating layer is 5.5 to 9.0 g / m ² per one side of the base paper.

  According to such a structure, the coated paper for printing excellent in the balance of opacity and whiteness can be manufactured easily.

  According to the coated paper for printing concerning this invention, high opacity and whiteness can be satisfied simultaneously, and also it can be set as the comparatively lightweight coated paper for printing with a high specific volume.

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

As described above, the printing coated paper according to the present invention has an undercoat coating layer and a topcoat coating layer on at least one surface of a base paper mainly composed of 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 topcoat coating layer contains kaolin and heavy pigments as pigments. Calcium carbonate, a binder, and a fluorescent brightening agent are contained, 8 to 20% by mass of the pulp is mechanical pulp, and the coating amount of the top coating layer is 4 per side of the base paper. a 5~7.0g / m ^2, the total coating amount of the undercoat coating layer and the top coat coating layers is a per side 5.5~9.0g / m ² base paper.

  Here, as the base paper used for the coated paper for printing of the present invention, a paper mainly composed of pulp can be used, and chemical pulp, mechanical pulp, waste paper recovered pulp, etc. can be used as the raw material pulp. On the other hand, 8-20 mass% of mechanical pulp is contained. By including mechanical pulp, the specific volume of the base paper can be increased. Furthermore, the opacity can be improved as the specific volume is increased as compared with the case of blending only chemical pulp. Mechanical pulp includes groundwood pulp (GP), refiner mechanical pulp (RGP), thermomechanical pulp (TMP), and chemithermomechanical pulp (CTMP), and CTMP that contributes to an increase in specific volume is particularly preferable. Furthermore, it is preferable to use bleached chemi-thermomechanical pulp (BCTMP) obtained by bleaching CTMP because the specific volume and whiteness can be improved at the same time. When the content of mechanical pulp is less than 8% by mass, the effect of improving the specific volume is poor. When the content exceeds 20% by mass, the specific volume is improved, but fading easily occurs, and the surface properties of the coated paper for printing are significantly reduced. Therefore, the suitability as printing paper is impaired.

  In the present invention, the base paper may contain known paper additives such as a sizing agent, a coloring dye, a paper strength enhancer, and a filler, if necessary. 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 at 4 to 10% by mass. The base paper can be produced using a known paper machine such as a long net 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 effect of the present invention is prominent when the base paper is light, and particularly remarkable when the base paper is 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 coating layers of the topcoat coating layer and the undercoat coating layer. Therefore, the coated paper for printing having sufficient opacity and whiteness can be obtained even if the basis weight of the base paper is relatively light as 35 to 65 g / m ² .

  The printing coated paper of the present invention is provided with an undercoat coating layer on at least one surface of a base paper, and an overcoat coating layer is provided on the surface of the undercoat coating layer. As described above, the undercoat coating layer contains titanium dioxide as a pigment. Titanium dioxide has been conventionally used as a pigment having excellent opacity for papermaking, and in particular, rutile or anatase type 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 that has few residues when made into a slurry and higher concealability.

For the undercoating layer, the coating amount of the titanium dioxide and the coating solution for the undercoating layer are applied so that the coating amount of titanium dioxide per side of the base paper is 0.2 to 0.8 g / m ^2. Adjust the work amount. 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 cannot be obtained sufficiently. Conversely, increasing the coating amount of titanium dioxide beyond 0.8 g / m ² has a negative effect of reducing the coating layer strength in addition to being less effective in improving opacity, and is excessive. There is also a problem that the cost increases due to the addition.

  In the coated paper for printing of the present invention, other pigments different from titanium dioxide can be contained in the undercoat coated layer as long as the intended effect is 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. In other words, titanium dioxide and one or more other pigments may be used in combination for the undercoat coating layer.

  The undercoat coating layer contains a binder in addition to a pigment such as titanium dioxide. The binder used here is not particularly limited, and starches such as thermochemically modified starch, oxidized starch, and phosphate esterified starch, polyvinyl alcohol resin, polyacrylamide resin, acrylic resin, and styrene-butadiene resin. A known binder used for the coating layer of the printing paper such as, can be appropriately selected and used.

Although content of the binder in an undercoat coating layer is not specifically limited, It is preferable to use a binder in the range of 90-300 mass parts with respect to 100 mass parts of pigments, and if it is the range of 100-250 mass parts Further preferred. In setting the coating amount of titanium dioxide 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 Can be less. 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 decreases, and the surface strength of the coated paper for printing may be lowered. On the other hand, when the blending amount of the binder in the undercoat coating layer exceeds 300 parts by mass, the opacity of the base paper part tends to decrease because the excess binder component fills the gaps in the base paper, and the entire coated paper for printing There is also a risk that the opacity of the material will also decrease. In addition, as a binder used at this time, phosphoric esterified starch is preferable because there is no concern about mechanical stability and the surface strength is easily improved.

The coating amount of the undercoat coating layer is preferably in the range of 0.5 to 3.0 g / m ² per side, 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 , coating stability with a film transfer coater such as a gate roll tends to be lacking, and the coating amount is uniform. The layer may not be obtained.

  In the present invention, the undercoating layer is further provided with a dispersant, an antifoaming agent, a thickening agent, a water retention agent, a water resistance agent, a colorant, a sizing agent, paper strength, and the like within a range not impairing the intended effect of the present invention. You may contain well-known paper additives, such as an agent. If necessary, a fluorescent brightening agent may be added, but as described above, the fluorescent whitening effect is inhibited by the high hiding property of titanium dioxide, so even if a fluorescent brightening agent is added to the undercoat coating layer, It is difficult to obtain the expected whitening effect. In the present invention, it is possible to obtain a high whiteness without containing a fluorescent brightening agent in the undercoat coating layer by adding a fluorescent brightening agent to the topcoat coating layer. It is preferable that the undercoat coating layer does not contain a fluorescent brightening agent.

  In the present invention, the undercoat coating layer can be formed by coating a base paper with a coating solution for the undercoat layer 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 metering size press, or an air knife coater, a blade coater, a bar coater or the like is used for coating the undercoat layer. It can employ | adopt suitably according to the property of a process liquid.

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

  In the present invention, the top coat layer contains kaolin and heavy calcium carbonate as pigments. By including these pigments in the coating layer, kaolin contributes to improving opacity, and heavy calcium carbonate is known to contribute to improving whiteness. By containing the calcium carbonate, the opacity and whiteness can be improved at the same time. 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 heavy calcium carbonate, the higher the whiteness.

  In the present invention, the proportion of kaolin and heavy calcium carbonate in the pigment contained in the top coat layer is not particularly limited, but 60 parts of kaolin out of 100 parts by mass of the pigment contained in the top coat layer. It is preferable to make -85 mass parts and heavy calcium carbonate into 15-40 mass parts. By mix | blending in such a range, the coating amount of a topcoat coating layer can improve comparatively at least opacity and whiteness comparatively at least.

  In the present invention, the top coat layer may contain other pigments different from kaolin and heavy calcium carbonate as long as the effects of the present invention are not impaired. 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 included 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 included in the topcoat coating layer is not particularly limited, and the coating layer of the coating paper for printing such as starch, polyvinyl alcohol resin, polyacrylamide resin, acrylic resin, styrene-butadiene resin, etc. The well-known binder used for can be used.

  The content of the binder in the top coat layer is preferably in the range of 4 to 20 parts by weight, more preferably in the range of 5 to 15 parts by weight with respect to 100 parts by weight of the pigment in the top coat layer. , More preferably in the range of 6 to 13 parts by mass. When the blending amount of the binder is less than 4 parts by mass, the strength of the top coat layer cannot 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 decreased, which may impair the printing suitability such as ink acceptability and drying property.

  In the present invention, a fluorescent whitening agent is contained in the top coat layer. The fluorescent whitening agent to be included in the top coat layer is not particularly limited, but is preferably a fluorescent dye, stilbene, coumarin, pyrazoline, naphthalimide, benzoxazole, imidazole, thiazole, Distyryl biphenyl-based ones conventionally used can be used. For example, a stilbene-based compound containing one or more sulfonic acid groups. Examples of stilbene-based compounds include diaminostilbene-disulfonic acid derivatives, and many fluorescent dyes that are highly dispersible and have been developed for coating applications are available on the market depending on the choice of solubilizer and the number of sulfonic acid groups. Examples of such products include the Leucophor (Leucophor (registered trademark)) series (manufactured by Clariant Japan) and the Keicol (KAYCOLL (registered trademark)) series (manufactured by Nisso Corporation).

  In the present invention, the content of the fluorescent brightening agent in the top coat layer is not particularly limited, but it is preferably 0.05% by mass or more, more preferably 0.8% by weight based on the total amount of the top coat layer. It is 1 mass% or more, More preferably, it is 0.3 mass% or more. The upper limit of the addition amount is not particularly limited, but even if it is added excessively, the fluorescence intensity does not reach its peak and there is a possibility that the discoloration may increase, so that it is 1.0% by mass or less with respect to the top coat layer. It is preferable that Inclusion of a fluorescent brightening agent in the topcoat layer can improve higher whiteness and visual whiteness.

  In the present invention, the topcoat coating layer further includes a dispersant, an antifoaming agent, a thickening agent, a water retention agent, a water resistance agent, a colorant, a pH adjuster, as long as the intended effect of the present invention is not impaired. You may contain well-known papermaking additives, such as.

  The top coat layer can be provided by applying a coating solution for the top coat layer on the surface of the undercoat layer provided on the base paper, and then drying it. The coating method of the coating liquid for the top coat layer is not particularly limited, and a known coating machine such as an air knife coater, a blade coater, or a bar coater can be employed, but 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 in such a range, the specific volume of the coated paper for printing can be increased while satisfying the printability of 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 (the surface of the base coat layer) cannot be sufficiently concealed, not only is the opacity and whiteness inferior, but the surface strength is insufficient. The printability cannot be satisfied. On the contrary, when the coating amount of the top coat layer exceeds 7.0 g / m ² , the ratio of the coat layer having a higher density than the base paper increases, so the specific volume decreases in inverse proportion to the density. It becomes difficult to increase the specific volume of the paper.

In the present invention, the total coating amount of the undercoat coating layer and the topcoat coating layer is set to 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 >. When 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 cannot be sufficiently concealed by the coating layer, and the surface strength is not only inferior in opacity and whiteness. Insufficient printability to satisfy printability. Conversely, when the total coating amount exceeds 9.0 g / m ² , the ratio of the coating layer having a higher density than that of the base paper increases, so that the specific volume decreases in inverse proportion to the density. The volume becomes low.

  In the present invention, when an undercoat coating layer and a topcoat coating layer are provided on both sides, the coating amount of each coating layer and the total coating amount of both layers may be varied within the above-mentioned range. . In particular, paper made with some paper machines tends to have different smoothness between the front and back sides. When using such a paper machine, the physical properties of both front and back sides can be changed by making a difference in the coating amount on the front and back sides. The difference can be reduced.

  The coated coated paper for printing according to the present invention may be subjected to a smoothing process using a calendar. The method for performing the smoothing process is not particularly limited, and can be performed with a known calendar such as a super calendar or a soft nip calendar.

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

  Next, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples. Further, “parts” and “%” in the examples represent “parts by mass” and “% by mass”, respectively, unless otherwise specified. In addition, the number of added parts is a value in terms of solid content.

Example 1
<Manufacture of base paper>
80 parts hardwood bleached kraft pulp (LBKP) with a freeness (CSF) of 400 mL, 10 parts softwood bleached kraft pulp (NBKP) with a freeness (CSF) of 550 mL, and a hardwood with 500 mL of freeness (CSF) 10 parts of bleached chemo-thermomechanical pulp (BCTMP) is dispersed in water to obtain a pulp slurry, 5 parts of light calcium carbonate (TP121S: manufactured by Okutama Kogyo Co., Ltd.) as a filler, 1 part of sulfuric acid band, paper strength A paper stock prepared by adding 0.6 parts of cationic starch (Kate 308: manufactured by NSC Japan) and 0.01 part of a yield improver (High Holder 220: manufactured by Kurita Kogyo Co., Ltd.) as an agent, Paper making was performed 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 solution for undercoat coating layer>
Disperse and mix in water 100 parts of titanium dioxide (PFC-503: manufactured by Ishihara Sangyo Co., Ltd.) as a pigment and 200 parts of gelatinized phosphate esterified starch (MS # 4600: manufactured by Nippon Food Processing Co., Ltd.). A coating solution for an undercoat coating layer having a solid content concentration of 18% was prepared.

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

<Creating coated paper for printing>
Apply the coating liquid for the undercoat coating layer on both sides of the base paper with a gate roll coater so that the coating amount per side is 1.5 g / m ^{2 in} terms of solid content, and dry and undercoat A construction layer was provided. Next, on both surfaces of the undercoat coating layer provided on both sides of the base paper, the coating solution for the top coat layer is 5.0 g / m ² on one surface (front surface) and 6 on the other surface (back surface). .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 give the desired smoothness. The above process is carried out with a so-called on-machine coater in which the process from the base paper making process to the coating / drying process of the undercoat coating layer and the topcoat coating layer is integrated, and the target coated paper for printing is prepared. Obtained.

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

(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 adjustment of the undercoat coating solution, the gelatinized phosphate esterified starch (MS # 4600: manufactured by Nippon Food Processing Co., Ltd.) ) Was added to 100 parts, and in the preparation of the coated paper for printing, the coating amount of the coating liquid for the top coat layer was 6.0 g / m ² on one side (surface), and the other side (Back side) Changed to 7.0 g / m ² , and coated paper for printing in the same manner as in Example 1 except that the coating amount on both sides was changed to 13.0 g / m ² in terms of solid content. Got.

Example 4
In the production of the base paper, the basis weight of the base paper was changed to 58 g / m ² , and in the production of the coated paper for printing, the coating amount of the coating liquid for the undercoat coating layer was calculated in terms of solid content per side. 1.0 g / m ² changed to, overcoat coating layer coating solution coating amount of 4.5 g / m ² on one surface (surface) of, 5.5 g / on the other surface (back surface) m ^The coated paper for printing was obtained in the same manner as in Example 1 except that the coating amount on both sides was changed to 10.0 g / m ² in terms of solid content.

(Comparative Example 1)
In the preparation of the coating solution for the undercoat coating layer, 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.

(Comparative Example 2)
In the production of the base paper, the blending of the pulp into the pulp slurry is 85 parts of hardwood bleached kraft pulp (LBKP) with a freeness (CSF) of 400 mL, and softwood bleached kraft pulp (NBKP) with a freeness (CSF) of 550 mL A coated paper for printing was obtained in the same manner as in Example 1, except that 10 parts and 5 parts of hardwood bleached chemithermomechanical pulp (BCTMP) having a freeness (CSF) of 500 mL were changed.

(Comparative Example 3)
The same method as in Example 1 except that the amount of gelatinized phosphate esterified starch (MS # 4600: manufactured by Nippon Food Processing Co., Ltd.) as the binder was changed to 50 parts in adjusting the coating solution for the undercoat. A coated paper for printing was obtained.

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

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

(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 production of the coated paper for printing, the coating amount of the coating liquid for the top coat layer is 8 on one side (surface). .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 above.

  The structure and evaluation result of the coating 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 by the following method.

<ISO whiteness>
In accordance with JIS P 8148, measurement was performed on both front and back sides of the coated paper for printing.

<ISO opacity>
The measurement was performed according to JIS P 8149.

<Fade degree>
The coating layer surface of the printing paper was irradiated with light for 60 minutes using an acme fading tester, and the decrease rate of the ISO whiteness before and after the light irradiation was calculated by the following formula 1.
Formula 1: Fading (%) = (ISO whiteness before irradiation−ISO whiteness after irradiation) / ISO whiteness before irradiation × 100

<Smoothness>
In accordance with JIS P 8155, measurement was made on both front and back sides of the coated paper for printing.

<Press life>
Using an RI printing machine (Meiji Seisakusho), 0.4 g of black ink (trade name: TV-15, manufactured by Toyo Ink) with a tack value of 15 is kneaded at a temperature of 30 ° C. and pressed onto the surface of the coated paper for printing. Printing was performed three times under the condition of a cylinder rotation speed of 60 rpm, and the degree of peeling of the coating layer surface was visually evaluated.
◯: Good with almost no peeling △: Slightly noticeable, inferior ×: Many noticeable, inconspicuous

<Printing finish>
The coated paper for printing is cut to a predetermined size, 1,000 sheets are collected, and printed on the reverse side of the coated paper for printing at a speed condition of 9,000 sheets / hour by the offset printing machine lithopier 4C manufactured by Mitsubishi Heavy Industries. The occurrence of ink crushing and white spots was visually evaluated. Print finish refers to the occurrence of ink blur and white spots.
○: Ink crushing is good and white spots are not generated. △: Ink crushing is slightly bad and white spots are slightly occurring. Impossible ×: Ink crushing is bad and white spots are also generated. Not possible

<Print surface>
The coated paper for printing is cut to a predetermined size, 1,000 sheets are collected, and printed on the reverse side of the coated paper for printing at a speed condition of 9,000 sheets / hour by the offset printing machine lithopier 4C manufactured by Mitsubishi Heavy Industries. The printing surface feeling was visually evaluated. The evaluation of the printing surface is evaluated for the presence of the surface that makes the fibers unique to mechanical pulp appear to rise.
◯: Good with no appearance that fibers appear to be lifted △: Feeling that fibers are slightly lifted, unacceptable ×: Feeling that many fibers are lifting, not possible

  As is clear from FIG. 1, the coated papers obtained in Examples 1 to 4 have high whiteness, opacity, and specific volume, and further, fading, printing durability, and printing finish. In addition, both the printing surface feeling and the printing surface feeling were excellent.

  On the other hand, the coated paper for printing obtained in Comparative Example 1 was inferior in opacity. This is considered to be caused by the fact that the undercoating layer does not contain titanium dioxide.

  Further, the coated paper for printing obtained in Comparative Example 2 was inferior in opacity because the specific volume was low. This is considered to be because the specific volume decreased because the ratio of BCTMP in the base paper was small, and the opacity decreased as the specific volume decreased.

  The coated paper for printing obtained in Comparative Example 3 had a lot of peeling on the surface of the coating layer and was inferior in printing durability. This is thought to be due to the fact that the amount of the titanium dioxide in the undercoat coating layer was too large, so that the amount of the binder was relatively reduced and the strength of the coating layer was lowered.

  The coated paper for printing obtained in Comparative Example 4 had a large fading value, and was inferior in printing finish and printing surface feeling. This is considered to be due to the fact that the ratio of BCTMP in the base paper is too large, fading easily occurs, and the surface property is also deteriorated.

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

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

Claims (9)

A coated paper for printing having an undercoat coating layer and an overcoat coating layer on at least one surface of a base paper mainly composed of 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 heavy calcium carbonate as a pigment, a binder, and a fluorescent brightening agent,
8-20% by mass of the pulp is mechanical pulp,
The coating amount of the top coating layer is 4.5 to 7.0 g / m ² per side of the base paper,
The coated paper for printing, wherein the total coating amount of the undercoat coating layer and the topcoat coating layer is 5.5 to 9.0 g / m ² per side of the base paper.   The coated paper for printing according to claim 1, comprising 60 to 85% by mass of kaolin and 15 to 40% by mass of heavy calcium carbonate with respect to 100% by mass of the pigment in the top coat layer. ^{2. The} coated paper for printing according to claim 1, wherein the basis weight of the base paper is 35 to 65 g / m ² .   The coated paper for printing according to claim 1, wherein the mechanical pulp includes a chemithermomechanical pulp or a bleached chemothermomechanical pulp.   2. The printing coating according to claim 1, wherein the addition amount of the binder in the undercoat coating layer is 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. paper.   2. The printing coating according to claim 1, wherein the amount of the binder added in the top coating layer is in the range of 4 to 20 parts by mass with respect to 100 parts by mass of the pigment in the top coating layer. paper.   2. The printing coated paper according to claim 1, wherein the fluorescent whitening agent is contained in an amount of 0.05% by mass or more based on the entire top coat layer. 2. The coated paper for printing according to claim 1, wherein the specific volume is 1.00 cm ³ / g or more. Providing a base paper containing 8 to 20% by weight of mechanical pulp with respect to the total amount of pulp;
Applying an undercoat coating layer coating solution containing a binder and 0.2 to 0.8 g / m ² of titanium dioxide per side of the base paper to at least one surface of the base paper Providing a coating layer;
The surface of the undercoat coating layer is coated with a coating liquid for a topcoat coating layer containing kaolin and heavy calcium carbonate as a pigment, a binder, and a fluorescent brightening agent. Providing a top coat layer of 4.5 to 7.0 g / m ² ,
The total coating amount of the said undercoat coating layer and topcoat coating layer is 5.5-9.0 g / m < ² > per single side | surface of a base paper, The manufacturing method of the coated paper for printing characterized by the above-mentioned.

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