JP7000093B2 - Newspaper - Google Patents

Description

The present invention relates to newspaper paper.

In recent years, newspapers for offset printing are rapidly becoming color printing, high speed printing, digital variable printing, tower printing, and the like. Therefore, newspaper paper is required to have better color print quality and print workability. However, in flat plate offset printing consisting of four colors (CMYK) of yellow, red, indigo, and ink, which are currently the mainstream, the hue is produced by subtractive color mixing, so the color reproduction area is larger than the RGB color reproduction area in digital data. Also narrows. Therefore, in the conventional low whiteness newspaper, the difference in color reproducibility between the digital data and the printed matter is likely to occur.

The subtractive color mixing is a phenomenon in which a new color is perceived as a result of color light passing through two or more objects. This is a phenomenon that occurs because colored light decreases as each object absorbs light in a different wavelength range. Additive color mixing is mixing by adding light, whereas subtractive color mixing is mixing by absorbing light. When the three primary colors Y (yellow), M (magenta) and C (cyan) of the subtractive color mixture are mixed, it becomes K (black). In printing, each color is made by this.

In order to ensure color reproducibility during printing, Patent Document 1 proposes a penetration drying type offset printing ink. However, improvement of printing ink alone is still insufficient to ensure color reproducibility when applied to newspaper paper with low whiteness, and further, for variable information printing by digital printing machines, which are being developed in recent years. There is a demand for the development of newspaper paper that is compatible with color printing and high speed.

Further, as a technique for high-white newspaper paper, in Patent Document 2, ash content in newspaper paper and a predetermined raw material pulp are used, and oil absorption, air permeability and whiteness are set in desired ranges to obtain high whiteness. High-white newspapers have been proposed, in which color printing is brilliant with whiteness, re-dislocation of undried ink is unlikely to occur, and printing defects are unlikely to occur even during high-speed printing. According to this technology, color printing can be expected to shine by designing the whiteness of the newspaper itself to be high, but since the oil absorption is high and the air permeability is kept low, undried ink paper is used. The amount of penetration into the layer increases, making it difficult to secure a sufficient ink density, and further studies are required on the opacity, which is a problem in whitening newspaper paper. Further, in Patent Document 2, it is described that the opacity required for newspaper paper can be maintained by using bleached mechanical pulp, but the problem that the opacity decreases as the whiteness increases tends to occur. The heavy use of mechanical pulp improves the oil absorption due to the fine fibers that are characteristic of mechanical pulp, and the problem of strike-through is likely to become apparent. Combined with the low air permeability, sufficient opacity in high-speed rotary printing. There is concern that it will be difficult to secure.

On the other hand, as a technique for increasing opacity, a newspaper paper having a pigment coating layer and having an ash content of 7 to 25% by weight derived from the base paper and the pigment coating layer (Patent Document 3), polyhydric alcohols and fatty acids By adding a bulking agent such as the ester compound (A) of the above and an ester compound selected from the ester compound (B) which is an ester compound of a polyhydric alcohol and a fatty acid and has an oxyalkylene group, the paper is bulky and highly unpleasant. A method of providing transparent newspaper paper (Patent Document 4) has also been proposed. Although such a means using a pigment or a bulking agent is a method for improving opacity, further improvement is required to provide newspaper paper having excellent color reproducibility with high saturation corresponding to color printing and high speed. Be done.

2009-12292 2008-196090 2009-84734 Gazette 2000-314091 Gazette

The present invention has been made based on the above circumstances, and an object of the present invention is to reproduce high-saturation colors when printed using an offset printing ink consisting of four process colors of yellow, red, indigo, and black. The purpose is to provide newspapers that are highly opaque and have good characteristics.

The invention made to solve the above problems is a newspaper paper in which a filler is embedded in pulp, the whiteness is 70% or more and 80% or less, the brightness is 85 or more and 95 or less, and the a value is −0. The color tone is 0.7 or more and −0.5 or less, the b value is 0.2 or more and 1.8 or less, and the basis weight is 45 g / m ² or more and 60 g / m ² or less.

The newspaper has high saturation color reproducibility and high opacity when printed using offset printing inks consisting of four colors of yellow, red, indigo and black processes. The reason why the newspaper has high saturation color reproducibility is not clear, but by providing the above configuration, the color tone of the newspaper is less likely to affect the appearance of the color printed by offset printing. It is presumed that the reproducibility is increasing.

The content of coniferous bleached kraft pulp in the above pulp is 16% by mass or more and 24% by mass or less, the content of broadleaf tree bleached kraft pulp is 18% by mass or more and 26% by mass or less, and the content of used paper pulp is 24% by mass or more and 32% by mass. % Or less, the content of mechanical pulp is 26% by mass or more and 34% by mass or less, and it is preferable to contain calcium carbonate having a volume average particle diameter of 1.0 μm or more and 2.0 μm or less as the filler. By doing so, it is possible to secure higher opacity and high printability in high-speed offset rotary printing even though it is a high-white newspaper paper.

It is preferable that the mechanical pulp is chemithermomechanical pulp (CTMP), the ash content is 7% by mass or more and 20% by mass or less, and the drip water absorption is 15 seconds or more and 40 seconds or less. By doing so, even if high-speed offset rotary printing is performed, high-definition printing corresponding to visualization and without color shift can be performed. In addition, color reproducibility and opacity in high-speed offset rotary printing can be further improved. It is presumed that this is because the permeability, drying property, etc. of the offset printing ink are optimized by doing so.

According to the present invention, it is possible to provide a newspaper paper having high saturation color reproducibility and high opacity when printed using an offset printing ink consisting of four colors of yellow, red, indigo and black processes. can.

Hereinafter, the newspaper paper according to the embodiment of the present invention will be described in detail.

The newspaper is a newspaper in which a filler is embedded in pulp. The newspaper can be obtained by making a papermaking slurry containing pulp and a filler, preferably by applying a surface treatment agent, calendering, or the like.

<Pulp>
The pulp (raw material pulp) used for the newspaper paper preferably contains coniferous tree bleached kraft pulp (NBKP), broadleaf tree bleached kraft pulp (LBKP), used paper pulp and mechanical pulp. The content of coniferous bleached kraft pulp in the above pulp is 16% by mass or more and 24% by mass or less, the content of broadleaf tree bleached kraft pulp is 18% by mass or more and 26% by mass or less, and the content of used paper pulp is 24% by mass or more and 32% by mass. % Or less, the content of mechanical pulp is preferably 26% by mass or more and 34% by mass or less.

(Coniferous bleached kraft pulp)
Pine typified by radiata pine is preferably used as the tree species in the newspaper, which improves the color reproducibility of high saturation, which is a problem, and has the same tensile and tear strength in high-speed rotary printing as that of conventional newspaper. It is necessary to ensure that the paper is bleached kraft pulp with a long fiber length. It can be planned.

Although the above effect can be obtained by blending 16% by mass or more of softwood bleached kraft pulp, if the blending amount exceeds 24% by mass, the long fiber length may reduce the printability, which is a problem. As the lower limit of the content of the softwood bleached kraft pulp, 18% by mass is more preferable, and 20% by mass is further preferable. On the other hand, as the upper limit of this content, 23% by mass is more preferable.

The Canadian standard freshness (CSF) of the softwood bleached kraft pulp to be blended is preferably adjusted to 300 ml or more and 650 ml or less. Here, the freeness is a value indicated by the Canadian standard freeness (CSF) specified in JIS P8121, and the pulp is beaten (mechanically beat and grind the pulp in the presence of water). It is a value indicating the degree of processing). Generally, the smaller the freeness value, the stronger the degree of beating, the greater the damage to the fibers due to beating, and the more fibrillation is progressing. NBKP, whose freeness is within the above range, is easily entangled with fibers due to the progress of fibrilization. Therefore, from the viewpoint of improving liquid permeability, it is constructed by reducing the basis weight (weight reduction) of newspaper paper in recent years. Even if the number of interfiber bond points of the fibers is reduced, the strength of each interfiber bond is higher than that of NBKP having a freeness of more than 650 ml and relatively unfibrilization. Therefore, if the freeness is 650 ml or less, the newspaper paper mainly composed of NBKP may have good strength characteristics. The freeness of the softwood bleached kraft pulp is more preferably 300 to 650 ml, particularly preferably 450 to 550 ml, and even more preferably 480 to 530 ml. When the freeness is less than 300 ml, the strength improving effect due to the entanglement of the fibers is saturated, the cutting of the fibers is promoted, and the permeation time may be delayed.

(Hardwood bleached kraft pulp)
In the newspaper, hardwood bleached kraft pulp produced from eucalyptus or acacia wood is preferably used, and when hardwood bleached kraft pulp is blended in an amount of 18% by mass or more and 26% by mass or less, the texture becomes good and the paper quality is stable. However, the printability is improved. If the hardwood bleached kraft pulp is less than 18% by mass, the texture for obtaining high-saturation color reproducibility may not be secured, and if it is as high as 26% by mass or more, there arises a problem that the strength is insufficient in recent high-speed rotary printing. In some cases. As the lower limit of the content of the hardwood bleached kraft pulp, 20% by mass is more preferable, and 21% by mass is further preferable. On the other hand, as the upper limit of this content, 24% by mass is more preferable, and 23% by mass is further preferable.

Acacia wood is a material that does not shrink due to drying, is strong against impact, is strong and hard, and the pulp obtained from acacia wood also inherits the original properties, has less short fiber content, and has dimensions in the production of newspaper paper. It is a useful raw material pulp with high stability and ink absorption and drying properties in high-speed rotary printing. Eucalyptus belongs to the genus Eucalyptus, and in particular, Eucalyptus globulus, Eucalyptus grandis, Eucalyptus europhila, Eucalyptus nighttens, Eucalyptus regnance, etc. have been widely used as raw material pulp materials for paper production for a long time. The fiber lumen is hard to be crushed and is rigid, and by blending this pulp fiber, bulky and low-density newspaper can be obtained.

The Canadian standard freshness (CSF) of the hardwood bleached kraft pulp to be blended is preferably adjusted to 300 ml or more and 450 ml or less. If the Canadian standard freeness of hardwood bleached kraft pulp is lower than 300 ml, the drainage is poor, which leads to deterioration of productivity in recent high-speed papermaking using a gap former at 1000 m / m or more. On the other hand, if the Canadian standard freeness is higher than 450 ml, the tensile strength becomes low, and paper breakage is likely to occur during papermaking or high-speed rotary printing.

(Recycled paper pulp)
When the used paper pulp is blended in an amount of 24% by mass or more and 32% by mass or less in the newspaper, it contributes to effective use of resources and can reduce the cost. The lower limit of the content of the recycled paper pulp is more preferably 25% by mass. On the other hand, the upper limit of this content is more preferably 30% by mass, further preferably 28% by mass. As the used paper pulp, deinked pulp is preferably used. The deinked recycled paper pulp is roughly divided into high-quality and medium-quality, and it is preferable to use high-quality recycled paper pulp in order to obtain newspaper paper having high saturation and excellent color reproducibility. Examples of high-quality used paper pulp include pulp prepared from used paper such as fine white, ruled white, card, imitation, color, Kent, white art, and milk carton. Typical examples of medium-quality waste paper pulp include pulp prepared from newspapers, magazines, cuttings, medium-quality anti-old paper, tea imitation, corrugated cardboard, mounts / land certificates, cardboard, and the like. In addition, newspaper paper has a high recovery rate as used paper and is said to be an excellent student for recycling. By using it for the newspaper paper of the present invention, it becomes possible to further promote the recycling of newspaper paper. .. In addition, used newspaper deinked pulp is a pulp that is mainly made of used newspaper, mixed with used magazine paper, etc., and deinked. These have fiber compositions such as chemical pulp such as NBKP and LBKP, and mechanical pulp. Although it is mixed, it can be used as a stable raw material pulp with a Canadian standard freeness of about 150 ml for used newspaper pulp because the fiber composition of the pulp is almost constant.

In particular, high-quality recycled paper pulp made from high-quality recycled paper has a coating layer containing a large amount of inorganic fine particles, and by removing the printing ink printed on the school attendance layer and the coating layer in the deinking process. Since the raw material pulp having a relatively high whiteness constituting the base paper can be effectively recovered and reused, it is most suitable for the reason for the present invention, and is an inorganic filler derived from used paper (raw material pulp even after undergoing a deinking treatment step). Since the content of the filler contained in the waste paper is high and the inorganic filler derived from the used paper is adhered to the raw material pulp, it does not fall off and cause paper dust even when high-speed offset rotary printing is performed. The opacity can be guaranteed.

(Mechanical pulp)
In the newspaper, when the mechanical pulp is blended in an amount of 26% by mass or more and 34% by mass or less, even if high-speed offset rotary printing is performed using an offset printing ink consisting of four colors of yellow, red, indigo and black processes. , It is possible to exhibit printability such as better ink drying property, color reproducibility and high opacity. This mechanical pulp does not include used paper pulp. The lower limit of the content of mechanical pulp in the total pulp is more preferably 27% by mass, further preferably 28% by mass. If the content is less than the above lower limit, the suitability for high-speed full-color offset rotary printing on the newspaper may be reduced. On the other hand, the upper limit of the content of mechanical pulp is more preferably 32% by mass, further preferably 31% by mass. If the content exceeds the upper limit, there may be a concern that paper dust due to fine fibers may be generated and printability may be deteriorated in high-speed offset rotary printing of the newspaper. Further, by setting the content of the mechanical pulp in the above range, it is possible to achieve both printability, opacity, and appropriate stiffness (rigidity) required by readers of newspaper paper.

Examples of the mechanical pulp include ground pulp (GP), pressurized crushed wood pulp (PGW), refiner crushed wood pulp (RGP), thermomechanical pulp (TMP), chemithermomechanical pulp (CTMP), and the like. TMP) Further, chemithermomechanical pulp (CTMP) is preferably used.

Thermomechanical pulp (TMP) is a pulp obtained by preheating the raw wood chips at a temperature below the glass transition temperature of lignin (a little over 100 degrees Celsius) for several minutes and then refining them with a pressure-type refiner. It has been used for paper since the latter half of the 1960s and has become the main means of production of mechanical pulp. CTMP is a mechanical pulp obtained by the same means as the thermomechanical pulp after subjecting the raw wood chips to a low concentration chemical treatment for a predetermined time. In the first place, the characteristics of thermomechanical pulp are that it has excellent strength by undergoing heat treatment, and although its optical characteristics such as opacity are slightly inferior to those of ground pulp, it is possible to secure high opacity, which is required for high-speed offset rotary printing newspapers. It is a suitable manufacturing means for obtaining high opacity. Further, although the chemithermomechanical pulp is slightly inferior in optical characteristics to the thermomechanical pulp by being subjected to chemical treatment in advance, it has a high whiteness, printability, and a digital printing machine typified by an inkjet printing machine, which are required for the newspaper paper of the present invention. It is possible to secure the correspondence to the variable printing by the above, and further, it is possible to suppress the production cost of the raw material pulp.

The pulp of the newspaper may contain pulp other than coniferous sala kraft pulp, broad-leaved bleached kraft pulp, used paper pulp, and mechanical pulp. Examples of other pulp include non-wood pulp. However, the total content of softwood bleached kraft pulp, broadleaf bleached kraft pulp, recycled paper pulp and mechanical pulp in the pulp used in the newspaper is preferably 80% by mass or more, more preferably 90% by mass or more, and 99% by mass. The above is more preferable. As described above, the effect of the present invention can be more sufficiently achieved by using only four kinds of pulp, which are substantially coniferous bleached kraft pulp, hardwood bleached kraft pulp, used paper pulp and mechanical pulp, in an appropriate combination.

For the post-separation freeness (degree of drainage) of all pulp used in the newspaper, prepare a sample of high white newspaper based on the present invention cut into a size of 10 cm × 10 cm, and immerse this sample in water at a water temperature of 20 ° C. 3 It is a value of freeness measured according to JIS P 8121 (1995) after being soaked for a minute and disintegrated according to JIS P 8220 (1998).

The post-separation freeness (degree of drainage) of the newspaper is preferably in the range of 280 ml or more and 350 ml or less. If it is less than 280 ml, it becomes difficult to make it bulky, which may affect the opacity and the like. The lower limit of this freeness is more preferably 300 ml, further preferably 320 ml, and even more preferably 330 ml. On the other hand, if it exceeds 450 ml, the amount of liquid absorbed by the size liquid in the size press increases, the papermaking speed decreases, and the print finish of newspaper paper may deteriorate. The lower limit of this freeness is more preferably 340 ml and even more preferably 335 ml.

<Filling fee>
(Calcium carbonate)
The newspaper paper preferably contains calcium carbonate having a volume average particle size of 1.0 μm or more and 2.0 μm or less as an internal filler. The lower limit of the volume average particle size of calcium carbonate is preferably 1.2 μm. On the other hand, this upper limit is preferably 1.8 μm. By adding calcium carbonate particles with such a particle size, even if a high amount of filler is added in combination with calcium carbonate, which originally has high whiteness, and an inorganic filler derived from recycled paper pulp, which is blended as raw material pulp. Paper dust is less likely to be generated or dropped during printing, the ash content in the paper can be increased, high whiteness can be obtained while using recycled paper pulp, and strike-through during printing can be improved.

In addition, by filling the outer fibrils of the raw material pulp with the filler by blending the mechanical pulp, it is possible to obtain high opacity in combination with the characteristics of the mechanical pulp which can originally obtain high opacity. Further, since the ink absorption and drying property can be improved, good printability and color reproducibility can be exhibited.

Examples of the calcium carbonate include light calcium carbonate and heavy calcium carbonate, but it is preferable to use amorphous heavy calcium carbonate. Amorphous heavy calcium carbonate is more likely to be physically contained in raw material pulp than light calcium carbonate or silica, and has a relatively broad particle size distribution, so it fills various gaps in raw material pulp. Therefore, it is possible to improve the filling rate. When heavy calcium carbonate having a relatively small particle size of 1.0 μm or more and 2.0 μm or less is used as the volume average particle size, offset printing ink consisting of four colors of yellow, red, indigo and black processes is used. Even if the high-speed offset rotary printing is performed, it has a good effect on printability such as good ink drying property, color reproducibility, and blank paper surface feeling.

As the lower limit of the blending amount of calcium carbonate, for example, 50 kg / pulp t is preferable, and 80 kg / pulp t is more preferable as the amount with respect to pulp. On the other hand, as the upper limit of this blending amount, for example, 200 kg / pulp t is preferable, and 150 kg / pulp t is more preferable. In addition, "kg / pulp t" means the amount with respect to 1 ton of absolute dry pulp.

(Regeneration fee)
As the filler, it is preferable to use a recycled filler, more preferably a silica-coated recycled filler, in addition to calcium carbonate. The reclaimed filler is, for example, particles obtained by using deinking floss as a main raw material and undergoing a dehydration step, a drying step, a firing step and a crushing step. The silica-coated reclaimed filler is particles whose surface is coated with silica. The silica coating can be performed by depositing silica on the surface of the reclaimed filler.

Since such recycled fillers and silica-coated recycled fillers can be recycled and used obtained by firing deink floss, there is no need to dispose of them as waste such as landfill, which reduces the environmental load and reduces the environmental load. It greatly contributes to resource saving. Further, when the raw material is deinking floss produced in the waste paper processing process, there are advantages that the cost is low, the amount of new inorganic particles used can be suppressed, and the manufacturing cost is sufficiently reduced. Furthermore, by using such a recycled filler, the ash yield during papermaking is high, and unlike calcium carbonate, for example, it does not cause wear deterioration of papermaking equipment such as wire wear, and it can be used as a recycled filler under a fine state of the resin component. By adsorbing, pitch troubles due to agglomeration of resin content are prevented, printing equipment is hardly soiled, paper can be manufactured at low cost and with high operability, and the opacity is as good as or better than before. Paper power is applied to the paper, and strike-through and paper breakage are reduced.

In addition, when a silica-coated reclaimed filler is added, the whiteness, opacity, surface strength, ink drying property, ink absorption unevenness, and bulkiness of the paper are further higher than when the reclaimed filler not coated with silica is used. Each effect such as can be improved. It should be noted that the content of calcium carbonate in deinked floss tends to increase with the recent shift to neutral papermaking, and the proportion of calcium in the obtained reclaimed filler also tends to increase. When a recycled filler having a high proportion of calcium is added to pulp in this way, the opacity of the paper may be slightly reduced, but the silica-coated recycled filler in which silica is precipitated on the surface is used as a recycled filler for papermaking. The function is very high, and the opacity of the newspaper obtained by adding the silica-coated reclaimed filler to the pulp is significantly improved.

Further, the recycled filler used in the present embodiment has a flexible and porous property in which fine particles are secondarily aggregated, so that it contributes to the formation of a bulky paper layer and can be obtained by adding the recycled filler to pulp as a filler. Newspaper has a low density and good rigidity.

The particle size of the regenerated filler used in the present embodiment has an average particle size of 0. It is preferably 05 μm or more, more preferably 0.1 μm or more, and the average particle size is preferably 16 μm or less, more preferably 15 μm or less, from the viewpoint of maintaining printability and preventing clogging of the sword tip. The average particle size of the reclaimed filler can be determined by measuring the methanol dispersion solution with a Coulter counter particle size distribution measuring device (TA-II type, manufactured by COULTERELECTRONICS).

Further, as the lower limit of the blending amount of the reclaimed filler, 1 part by mass is preferable with respect to 100 parts by mass of calcium carbonate, and 5 parts by mass is more preferable. On the other hand, as the upper limit of the blending amount, 50 parts by mass is preferable with respect to 100 parts by mass of calcium carbonate, and 30 parts by mass is more preferable.

(Other fillers)
In the newspaper, calcium carbonate and other fillers other than the recycled filler can be further used. Other fillers include at least one filler selected from, for example, inorganic fillers such as white carbon, talc, clay, titanium dioxide, synthetic silica, and aluminum hydroxide, and synthetic polymer fine particles such as polystyrene resin and urea formaldehyde resin. Can also be used together. Among these, white carbon is preferable from the viewpoint of increasing whiteness, opacity and the like.

However, as the upper limit of the total blending amount of other fillers, 50 parts by mass is preferable with respect to 100 parts by mass of calcium carbonate, and 30 parts by mass is more preferable. By setting the blending amount of other fillers to the above upper limit or less, the effect of filling calcium carbonate can be further enhanced. On the other hand, as the lower limit of the blending amount of other fillers, particularly preferably white carbon, 1 part by mass is preferable and 5 parts by mass is preferable with respect to 100 parts by mass of calcium carbonate in order to sufficiently exert the effect of filling. Is more preferable.

<Other internal additives>
The paper slurry is a slurry containing pulp, a filler and water, but other internal additives (auxiliaries) may be added. As the additive to be added to the slurry, one that is blended (internally added) to ordinary paper can be used, and for example, a paper strength enhancer such as starch, vegetable gum, aqueous cellulose derivative, sodium silicate; rosin. , Starch, CMC (carboxymethyl cellulose), polyvinyl alcohol, alkyl ketene dimer, ASA (alkenyl anhydride succinic acid), neutral rosin and other internal sizing agents; polyacrylamide and its copolymers, yield improving agents such as sodium silicate and the like. ; Colorants such as dyes and pigments can be mentioned.

<Surface treatment>
In the newspaper, after preparing a paper slurry from pulp and making paper, a polymer material such as starch, PVA (polyvinyl alcohol), or polyacrylamide, or a surface treatment agent such as a surface sizing agent is applied to the surface. You may.

(Starch)
Among the above-mentioned polymer materials, it is preferable to use starches from the viewpoint of further enhancing the effect of the present invention and improving printing suitability and the like. Examples of the starches include starch, modified starch and the like, and modified starch is preferable. The modified starch is not particularly limited, and examples thereof include oxidized starch obtained by subjecting corn, potato, tapioca, wheat, rice and the like to oxidation treatment, enzyme treatment and the like, using ordinary starch raw materials. Further, etherified starch, esterified starch, cationized starch, hydroxyethylated starch (HES) and the like can also be used.

In particular, it is preferable to use oxidized starch and HES in combination. In the newspaper, when a surface treatment agent containing oxidized starch and hydroxyethylated starch is used as the surface treatment agent to be applied to both sides of the base paper, the above two types of starch are used as the base paper when the surface treatment agent is applied. It does not penetrate to the inside and forms a strong film on the surface. Therefore, since the surface strength is high and the generation of paper dust can be suppressed, newspaper paper having excellent printing workability can be obtained. In addition, the occurrence of Nepari trouble during printing is suppressed. By using the above two types of starch, the starch does not penetrate into the inside of the base paper and the cause of forming a strong film on the surface is not clear, but the carboxyl groups of the oxidized starch and the hydroxyl groups of the hydroxyethylated starch It is conceivable that the bonds (esterification reaction, etc.) and cross-linking result in polymerization and make it difficult to penetrate into the inside. It is also considered that the mixing of these two types of starch results in an appropriate viscosity, and the esterification reduces the affinity between the starch and the cellulose constituting the pulp fiber, making it difficult to penetrate. Be done. It is also considered that the decrease in viscosity is caused by the reaction of the two types of starch. Further, it is considered that the suppression of the occurrence of Nepperi trouble is also caused by the decrease in hydrophilicity of starch due to the above-mentioned esterification and the like. The content ratio of the oxidized starch and the hydroxyethylated starch is preferably 1: 9 or more and 9: 1 or less, and more preferably 4: 6 or more and 6: 4 or less on a mass basis.

When these starches are used, the amount in the surface treatment agent should be adjusted so that the content of the starch is 40% by mass or more and 95% by mass or less in the total solid content in order to obtain the desired effect. Is preferable.

(Surface size agent)
As the surface treatment agent, a styrene-based sizing agent, an olefin-based sizing agent, an alkyl ketene dimer, alkenyl succinic anhydride, rosin and the like can be used, but they have high size, compatibility with ink, and prevention of filler from falling off. A styrene-based sizing agent is preferable from the viewpoint of effect and the like.

Examples of the styrene-based sizing agent include styrene-acrylic acid copolymers, styrene (meth) acrylic acid copolymers (note that (meth) acrylic acid means "acrylic acid and / or methacrylic acid"), and styrene. Examples thereof include (meth) acrylic acid (meth) acrylic acid ester copolymer, styrene maleic acid copolymer, styrene maleic acid semi-ester copolymer, and styrene maleic acid ester copolymer.

By using the above two types of starch (oxidized starch and HES) together with the surface sizing agent, the surface sizing agent can easily stay on the surface and the amount of the surface sizing agent added can be reduced. In addition, it is possible to suppress paper surface stains in an offset printing machine caused by excessive addition of a surface sizing agent.

The mixing ratio of the surface sizing agent to the starch is preferably 5 parts by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the starch in terms of solid content. By setting the blending ratio of the surface sizing agent to 5 parts by mass or more, the effect of improving the sizing property and the surface strength of the paper can be sufficiently obtained. On the other hand, by setting the compounding ratio of the surface sizing agent to 30 parts by mass or less, it is possible to suppress an increase in manufacturing cost and to make the opacity and ink drying property more sufficient.

(Other surface treatment agents, etc.)
Other adhesives such as pigments such as kaolin and calcium carbonate, defoaming agents, water resistant agents, surface sizing agents, and various auxiliary agents such as preservatives can be added to the surface treatment agent as appropriate. The solid content concentration of the surface treatment agent is not particularly limited, and is preferably adjusted to, for example, about 2 to 25% by mass depending on the coating device and the coating amount.

If the surface treatment agent is used in an excessively large amount, not only the cost becomes high, but also the stickiness of the paper surface, which is called sticking property, tends to be developed when the paper surface is moist. If this nepari property becomes large, the blanket piring may be increased, especially in the non-image area, and the paper surface may stick to the blanket during printing, resulting in running troubles such as wrinkles and paper breaks. It is not preferable because it exists. Further, when the amount of the surface treatment agent used increases, the transparency of the target paper may increase, that is, the opacity may decrease, or the dryness of the ink may deteriorate. Of these surface treatment agents, starch and polyacrylamide are widely used because they have relatively low nepari properties, but since they are highly soluble in water, they are easily eluted in moist water during printing and are used as fillers. At the same time, it accumulates on the blanket, and blanket pyring is likely to occur. In addition, the eluted surface treatment agent is transferred to and accumulated on the printing plate via the blanket, so that the non-image area of the printing plate becomes oil-sensitive, and ink stains on the non-image area, that is, stains on the paper surface called ground stains are removed. It is not preferable to use a large amount because it is easy to induce.

As the surface treatment agent, a coating device generally used in the papermaking field, for example, a size press, a blade metering size press, a rod metering size press, a gate roll coater, a blade coater, a bar coater, a rod coater, an air knife coater, etc. is used. Can be applied.

The amount of the surface treatment agent applied is preferably adjusted to 0.4 g / m ² or more per side in terms of dry mass in order to sufficiently improve the surface strength of the paper. Further, in order not to increase the cost or cause deterioration of opacity and ink dryness, it is preferable to adjust the dry mass to 3.0 g / m ² or less per side. More preferably, it is preferably adjusted to 0.5 g / m ² or more and 1.0 g / m ² or less per side.

By increasing the amount of the surface treatment agent applied to the front and back surfaces on the back surface side, which is the rough surface side, on the front surface side, better flatness and bulkiness can be obtained, and a chewy newspaper can be obtained. can.

<Colorants: dyes and pigments>
In the newspaper, a colorant such as a dye or a pigment may be applied to the surface as a surface treatment agent. Moreover, you may add such a colorant internally. By using a colorant, the color tone, whiteness, etc. of the obtained newspaper can be adjusted. The present invention is intended for high whiteness newspaper paper having a basis weight of 45 g / m ² or more and 60 g / m ² or less and having a whiteness of 70% or more and 80% or less, and preferably contains broad-leaved bleached kraft pulp. Therefore, opacity becomes a problem in high-speed offset rotary printing using an offset printing ink consisting of four process colors of yellow, red, indigo, and black, which have low opacity and particularly absorb-drying property. In the present invention, machine pulp and used paper pulp are preferably used as a measure for ensuring opacity, but machine pulp is prone to discoloration when read outdoors by a reader such as newspaper paper, and in the use of used paper pulp. Has found that it has a problem of lower whiteness than bleached kraft pulp, and it is preferable to adjust it to a predetermined color tone with a dye or dye in order to improve opacity, discoloration, and whiteness of appearance.

According to the findings of the present inventors, a basic dye having high lightness and vivid color can be preferably used as a measure for improving the dyeing property on used paper pulp and mechanical pulp having a relatively strong anionic property, which is further desired. It has been found that it is preferable to use two or more kinds of dyes and dyes and pigments in order to secure the color tone of the above. According to the findings of the present inventors, in order to obtain high-saturation color reproducibility when printing with offset printing ink consisting of four colors of yellow, red, indigo and ink processes and interpretation of detailed information on newspaper paper. The color tone is adjusted so that the whiteness is 70% or more and 80% or less, the brightness is 85 or more and 95 or less, the a value is -0.7 or more and -0.5 or less, and the b value is 0.2 or more and 1.8 or less. It is necessary, and it is preferable to adjust by combining a purple dye with a green dye and / or a yellow dye, and the content of the coniferous bleached kraft pulp preferably used in the present invention is 16% by mass or more and 24% by mass or less. The opacity of broad-leaved bleached kraft pulp is 18% by mass or more and 26% by mass or less, waste paper pulp is 24% by mass or more and 32% by mass or less, and mechanical pulp content is 26% by mass or more and 34% by mass or less. In the formulation of raw pulp to ensure tensile strength in high-speed rotary offset printing, for example, purple dye is 0.02 to 0.05 g / m ² , green dye is 0.02 to 0.05 g / m ² , and / or yellow. It is preferable to adjust the dye to a content of 0.01 to 0.03 g / m ² .

When the colorant is applied to the surface instead of the internal coating, uneven coloring can be suppressed with a small amount of dye. Generally, colored dyes and pigments are used alone or in combination to adjust the color tone, but these are yellowish because the pulp and white pigments used usually show a slight yellowish tinge. Only a very small amount of blue or bluish-purple colorant (blueing agent) is used to hide the color and make it feel white as much as possible.

Dyes for paper use have higher dyeability to reclaimed fillers than conventionally commonly used clays and calcium carbonates that exhibit anionic properties, and cationic direct dyes or basic dyes have higher dyeability depending on the specifications of the reclaimed fillers. Is different. Therefore, when these dyes with different dyeing properties are used together in the coating agent, the felt surface having a high dye fine fiber ratio and the filler ratio is colored with a cationic direct dye or a basic dye, and the wire surface having a high pulp ratio is mainly used. Is colored with anionic direct dye. Therefore, the difference between the front and back of the hue can be reduced by adjusting the ratio of the anionic direct dye of the same color to the cationic direct dye or the basic dye, and the difference between the front and back of the hue can be reduced to zero depending on the degree of adjustment. It is also possible to do.

As the type of the above dye, a basic dye is preferably used, but one or two or more kinds are appropriately selected from acid dyes other than basic dyes, anionic direct dyes, cationic direct dyes, nonionic dyes and the like. However, it can be used in an appropriate combination that contributes to solving the problem of the present invention.

When a dye is blended with a surface sizing agent or a paper strength enhancing agent in a coating agent, the paper strength enhancing agent is less likely to aggregate with the surface sizing agent and is easy to handle. In many cases, anionic starch is used as a dye. In this case, the addition of a cationic dye may result in the formation of aggregates with anionic starch. Therefore, in this case, it is more preferable to use an anionic direct dye as the dye.

Specific examples of the dye include the following.
(Basic dye)
・ M1: Purple basic dye manufactured by Hodogaya Chemical Industry Co., Ltd., trade name: Methyl Violet ・ G1: Green basic dye manufactured by Nihonkayaku Co., Ltd., trade name: Kayafect Green ・ Y1: Yellow basic dye Japan Made by Yaku Co., Ltd., Product name: Yellow SP

(Anionic direct dye)
・ M2: Purple direct dye manufactured by Nippon Kayaku Co., Ltd., trade name: Violet BC
・ G2: Green direct dye manufactured by Nippon Kayaku Co., Ltd., trade name: Green G
・ Y2: Yellow direct dye manufactured by Nippon Kayaku Co., Ltd., trade name: Kayafect Yellow KHC
・ B2: Blue direct dye Nippon Kayaku Co., Ltd., Product name: Kayafect Blue F
・ R2: Red direct dye Nippon Kayaku Co., Ltd., Product name: Kayafect Red P

(Cationic direct dye)
・ Y3: Yellow direct dye manufactured by Nippon Kayaku Co., Ltd., trade name: Yellow CG

In the newspaper, if it is a hydrophilic and water-soluble aqueous dye, the color tone of the present invention is 85 or more and 95 or less, and a value is -0.7 or more and -0.5 or less. In addition to the above, any dye can be used in combination to adjust the b value to 0.2 or more and 1.8 or less. For example, acid dyes, direct dyes, basic dyes, etc. are used along the color index. Be done.

As particularly preferably used basic dyes, for example, two or more kinds of methyl violet, basazole green, crystal violet, methylene blue, chrysoizone, Victoriya green, rhodamine and the like are added.

<Calendar>
The paper that has been made can be passed through a calender device as needed and subjected to pressurization and smoothing to finish it as newspaper paper. As a calendar device, it is better to use a soft calendar with a combination of a metal roll and a resin roll than a machine calendar with a combination of a normal metal roll and a metal roll to smooth the paper layer without strong pressure. This is more preferable because it can sufficiently suppress a decrease in paper layer strength.

When using a soft calendar, the flatness and bulkiness can be further improved by passing the paper so that the back side, which is the rough side of the newspaper, comes into contact with the metal roll surface of the soft calendar first. It is possible to obtain newspaper paper with high flatness and little difference between the front and back sides in high-speed papermaking of 1000 m / min or more.

<Ash>
The lower limit of the ash content in the newspaper is preferably 7% by mass, more preferably 10% by mass. By setting the ash content to the above lower limit or higher, the whiteness and opacity can be increased and good color reproducibility can be exhibited. On the other hand, the upper limit of this ash content is preferably 20% by mass, more preferably 17% by mass. By setting the ash content to the above upper limit or less, it is possible to suppress a decrease in paper power, improve printing suitability, and improve the feeling of hand in the newspaper reader. The ash content can be measured by the ash content measuring method specified in JIS P-8251 (2003).

<Whiteness>
The lower limit of the whiteness of the newspaper is 70%, preferably 74%, and more preferably 76%. By setting the whiteness to the above lower limit or higher, the newspaper has a high whiteness and excellent color reproducibility with high saturation. On the other hand, the upper limit of this whiteness is 80%. The whiteness is a value measured in accordance with "Hunter whiteness test method for paper and pulp" described in JIS P8123. The whiteness can be adjusted by the type and amount of pulp, filler, and colorant.

<Blank opacity>
The lower limit of the blank opacity (opacity) of the newspaper is preferably 90%, more preferably 92%. On the other hand, as the upper limit of the blank opacity, 95% is preferable, and 94% is more preferable. By setting the blank opacity within the above range, it is possible to further enhance the effect of excellent color reproducibility with high saturation while suppressing the occurrence of strike-through during printing. The blank paper opacity is a value measured in accordance with the "paper opacity test method" described in JIS P8138. The blank opacity can be adjusted according to the type and amount of filler, color tone, and the like.

<Color tone>
As a method for measuring and displaying the color tone of paper or the like, there are methods specified in JISZ-8722 and JISZ-8730. In this method, the color tone is represented by L * (Elster), a * (Aster) and b * (Beaster). L * represents the brightness, and the larger the value, the higher the brightness. a * (a value) represents redness, and the larger the value, the stronger the redness, and the negative number indicates that the greenness becomes stronger. b * (b value) indicates yellowness, the larger the value, the stronger the yellowness, and the negative number indicates the bluishness. Generally, the color tone is represented by the position of the graph with a * on the horizontal axis and b * on the vertical axis. When both a * and b * are 0, the color is expressed as colorless, and in this case, the L * value indicates the degree of whiteness (blackness). Generally, the color tone of the paper to which the filler is added is about -2 to + 1 for a * and about +5 to +8 for b *, showing a slight yellowish color.

In the newspaper, the brightness (L *) is 85 or more and 95 or less. Further, the a value (a *) is −0.7 or more and −0.5 or less, and the b value (b *) is 0.2 or more and 1.8 or less. Within this range, it is possible to adjust the color reproducibility of high saturation without significantly changing the color tone, that is, while making the color feel white. If the a value is larger than -0.5, the paper becomes reddish, and if it is smaller than -0.7, the greenishness becomes too strong. If the b value is greater than 1.8, the yellowness is too strong, and if it is less than 0.2, the bluishness is too strong. It can be adjusted according to the type and amount. By adjusting to the above color tone, even when exposed outdoors, the color tone change of high-speed offset rotary printing using offset printing ink consisting of four colors of yellow, red, indigo, and black process is suppressed and good color reproducibility is achieved. Can be maintained and so on. The lower limit of the a value is preferably −0.65, and the upper limit is preferably −0.55. The lower limit of the b value is preferably 0.6, more preferably 1.0, and even more preferably 1.2. On the other hand, this upper limit is preferably 1.6, more preferably 1.3.

<Drip water absorption>
The lower limit of the drip water absorption in the newspaper is preferably 15 seconds, more preferably 20 seconds. The upper limit is preferably 40 seconds, more preferably 35 seconds, still more preferably 30 seconds, and even more preferably 25 seconds. By setting the drip water absorption of the newspaper in the above range, the color reproducibility can be improved. In addition, the drip water absorption degree was determined by Japan TAPPI No. It refers to a value measured with a dripping water volume of 1 μl according to the method described in 33 (Water absorption rate test method for absorbent paper). In addition, the drip water absorption degree can be adjusted by the type and amount of pulp, filler, sizing agent, other surface treatment agent, and internal additive used.

<Basis weight>
The lower limit of the basis weight of the newspaper is 45 g / m ² , preferably 50 g / m ² . By setting the basis weight to the above lower limit or higher, sufficient opacity can be ensured, and paper quality strength in high-speed rotary printing can be ensured. On the other hand, the upper limit of this basis weight is 60 g / m ² , preferably 55 g / m ² . By setting the basis weight to the above upper limit or less, weight reduction and resource saving can be achieved. The basis weight is a value measured in accordance with the "basis weight measuring method" described in JIS P8124.

<Density>
As the lower limit of the density of the newspaper, 0.70 g / cm ³ is preferable, and 0.72 g / cm ³ is more preferable. On the other hand, as the upper limit of this density, 0.80 g / cm ³ is preferable, and 0.78 g / cm ³ is more preferable. By setting the density within the above range, it is possible to obtain newspaper paper whose strength can be maintained along with the weight reduction and weight reduction. The density refers to a value measured in accordance with "Paper and Paperboard-Thickness and Density Test Method" described in JIS P8118.

<Rigidity (stiffness, hand flesh)>
As the lower limit of the rigidity of the newspaper in the MD direction, 30 cm ^3/100 is preferable, and 32 cm ^3/100 is more preferable. On the other hand, as the upper limit of this rigidity, 55 cm ^3/100 is preferable, and 50 cm ^3/100 is more preferable. By setting the rigidity within the above range, it is possible to impart a waist suitable for, for example, high-speed rotary printing. The rigidity is a value measured in accordance with the "paper stiffness test method using a Clark stiffness tester" described in JIS P8143.

<Cobb size and oil absorption>
The present inventors transfer dampening water and printing ink on newspaper having a basis weight of 45 g / m ² or more and 60 g / m ² or less in accordance with JIS P8124 for 10 seconds based on JIS P8140 of the newspaper. It has been found that it is preferable to have a relationship in which the degree of hump size is 30 g / m ² or more and 80 g / m ² or less, and the oil absorption degree based on JIS P3001 is 50 seconds or more and 150 seconds or less. By suppressing the relationship between so-called hydrophilicity and lipophilicity within a predetermined range, it is possible to further improve the offset rotary printing suitability in combination with the flattening process.

<RI evaluation>
The surface strength of the newspaper is preferably at least grade 3 or higher as measured by an RI tester (manufactured by Ming Seisakusho Co., Ltd.). In such a case, the paper quality strength in high-speed rotary printing of the newspaper paper is increased.

The newspaper has high saturation color reproducibility and high opacity when printed using offset printing inks consisting of four colors of yellow, red, indigo and black processes. In addition, the printing paper has a good whiteness. Further, the newspaper has less fluffing during printing, uneven ink absorption, accumulation of paper dust on the blanket and strike-through, and is excellent in ink drying property. The newspaper paper is excellent in various characteristics at the time of printing, particularly at the time of color printing, and can be suitably used for high-speed offset rotary color printing such as about 120,000 to 170,000 copies / hour.

The newspaper of the present invention will be described in more detail based on the following examples, but the present invention is not limited to these examples.
Various measurements and evaluations were performed by the following methods.

(A) Percentage of each pulp in pulp Measured according to the "fiber composition test method" described in JIS P8120.

(B) Freeness (CSF) (freeness after dissociation)
A sample of newspaper paper cut to a size of 10 cm × 10 cm is prepared, and this sample is immersed in water at a water temperature of 20 ° C. for 3 minutes, and after being dissociated according to JIS P 8220 (1998), JIS P 8121 (1995) “Pulp of The Canadian Standard Curability (CSF) was measured according to the Curvature Test Method.

(C) Basis weight The measurement was performed in accordance with the "basis weight measuring method" described in JIS P8124.

(D) Ash content The measurement was performed in accordance with "Paper, Paperboard and Pulp-Ash Content Test Method" described in JIS P8251.

(E) Whiteness Measured in accordance with "Hunter whiteness test method for paper and pulp" described in JIS P8123.

(F) Tone Use a color difference meter (ZE2000, manufactured by Nippon Denshoku Industries Co., Ltd.) to measure the brightness (L *), hue (a *, a value) and hue (b *, b value) in accordance with JIS Z8722. Measured using.

(G) Blank paper opacity Measured according to the "paper opacity test method" described in JIS P8138.

(H) Rigidity (MD direction)
The measurement was performed in accordance with the "paper stiffness test method using a Clark stiffness tester" described in JIS P8143.

(I) Cobb water absorption (size)
The measurement was performed at a measurement time of 10 seconds in accordance with "Paper and Paperboard-Water Absorption Test Method-Cobb Method" described in JIS P8140.

(J) Intravenous water absorption Japanese TAPPI No. Based on 33 (water absorption rate test method for absorbent paper), the measurement was carried out with a dropping water volume of 1 μl.

(K) Oil absorption degree The measurement was performed with light oil No. 1 in accordance with the "oil absorption degree test method" described in JIS P3001 (1976).

(L) Fluffing With an RI printing suitability tester (manufactured by Akira Seisakusho Co., Ltd.), the surface of the newspaper was repeatedly printed 5 times with the rubber rolls to which the test ink was not applied. Using a loupe, the surface of the paper web was visually observed in a range of 100 mm × 100 mm, and evaluation was performed based on the following evaluation criteria.
(Evaluation criteria)
◎: Very little fluffing.
○: There is little fluffing.
Δ: There is a little fluffing.
×: There is a lot of fluffing.

(M) Ink absorption unevenness Using an offset color printing machine (model number: SYSTEM C-20, manufactured by Komori Corporation), at a printing speed of 160,000 copies / hour, four colors in the order of indigo, red, yellow, and ink. Color printing was performed. Ink density unevenness in the indigo / red heavy color portion was visually observed and evaluated based on the following evaluation criteria.
(Evaluation criteria)
⊚: No unevenness in ink density was observed, the image was uniform and clear, and the saturation was very high.
◯: Ink density unevenness is hardly observed, the image is uniform, and the saturation is high.
Δ: Ink density unevenness is observed, the image is slightly uneven, and the saturation is slightly inferior.
X: Ink density unevenness is obvious, the image is non-uniform, and the saturation is poor.

(N) Accumulation of paper dust on the blanket Using the same offset color printing machine as in the evaluation of ink absorption unevenness, four-color printing was performed in the order of indigo, red, yellow, and black at the same printing speed. After printing 10000 copies, the degree of accumulation of paper dust on the blanket non-image area was visually observed and evaluated based on the following evaluation criteria.
(Evaluation criteria)
⊚: No paper dust is observed.
◯: A small amount of paper dust is observed, but there is no problem in practical use.
Δ: The generation of paper dust is clearly recognized.
X: A large amount of paper dust is accumulated on the blanket, and the blanket is white.

(O) Ink dryness Using the same offset color printing machine as the evaluation of ink absorption unevenness above, indigo, red, yellow, and black in the order of indigo, red, yellow, and black with ink for newspaper printing with a vegetable oil content of 45% at the same printing speed. Color color printing was performed. After stacking 500 parts of printed matter so that the printed surface and the blank sheet overlap each other and leaving the printed matter under a load of 5 kgf (about 49 N) for 1 day, visually observe the degree of stain on the blank sheet and based on the following evaluation criteria. Evaluated.
(Evaluation criteria)
⊚: Almost no stain is observed, and the saturation is very high.
◯: Only a small amount of dirt is observed, and the saturation is high.
Δ: Dirt is observed, and the saturation is slightly inferior.
X: The stain is remarkable and the saturation is poor.

(P) Color reproducibility Using an RI-I type printing machine (manufactured by Ming Seisakusho Co., Ltd.), four-color multicolor printing of offset inks of yellow, crimson, indigo, and ink is performed, and the printed surface is visually inspected. The evaluation was performed as follows. ○ The above was accepted.
⊚: There is no influence of the color tone of the paper, and it has excellent color reproducibility with extremely high saturation.
◯: Although the influence of paper can be seen, the color reproducibility is good with high saturation.
Δ: The color tone of the paper is affected, and the color reproducibility is slightly poor.
X: The color reproducibility is very poor due to the influence of the color tone of the paper.

(Q) A strike-through offset rotary press (Toshiba offset rotary press, manufactured by Toshiba Corporation) was used to perform black monochrome printing at a printing speed of 900 rpm. After printing 60,000 copies, the solid black surface was visually observed from the back surface and evaluated based on the following evaluation criteria.
(Evaluation criteria)
⊚: Almost no strike-through is observed.
○: Only a few strike-throughs are observed.
Δ: strike-through is observed.
×: Significant strike-through.

[Example 1]
Broad-leaved bleached kraft pulp (NBKP) 24% by mass, broad-leaved bleached kraft pulp (LBKP) 18% by mass, desorption / deinking used paper pulp (DIP) 28% by mass as used paper pulp, and chemithermomechanical pulp (CTMP) as mechanical pulp. ) 30% by mass was blended, and a pulp slurry whose freeness was adjusted with a refiner was obtained. In addition, as a dye, a purple basic dye manufactured by Hodogaya Chemical Industry Co., Ltd., trade name: Methyl Violet 0.01 kg / t, a blue direct dye manufactured by Nippon Kayaku Co., Ltd., trade name: Kayafect Blue F was contained in 0.2 kg / t, manufactured by Nippon Kayaku Co., Ltd., which is a red direct dye, and trade name: Kayafect Red P 0.50 kg / t. Heavy calcium carbonate having a volume average particle diameter of 1.5 μm was added to this pulp slurry so that the ash content was 8%, and the fabrication pH was adjusted to 7.5 with a sulfuric acid band. Using this pulp slurry, a base paper for newspapers was made by a twin wire paper machine.

Next, a starch solution obtained by mixing 50 parts by mass of oxidized starch (mass average molecular weight 700,000 manufactured by Nippon Food Processing Co., Ltd.) and 50 parts by mass of hydroxyethylated starch (HES, Penford Co., Ltd. mass average molecular weight 1.55 million) as a surface treatment agent. A styrene-based sizing agent (SS2712, manufactured by Seikou PMC Co., Ltd.) was blended in an amount of 20 parts by mass with respect to 100 parts by mass of starch. This surface treatment agent was applied to both sides of the base paper having a surface temperature of 50 ° C. at a dry mass of 0.6 g / m ² per side. As a result, the newspaper paper of Example 1 was obtained.

[Examples 2 to 13, Comparative Examples 1 to 13]
The types and compounding ratios of pulp, and the types and particle sizes of fillers are as shown in Table 1, and the basis weight and ash content are adjusted to be as shown in Table 2, and Examples 2 to 13 and Comparative Examples 1 to 13 are adjusted. I got each of the newspapers. The ash content was adjusted by the amount of filler. Further, in order to adjust the color tone, the type and amount of the dye were appropriately changed. When the ratio of each pulp of the mixed pulp used was measured by the above method, it was the same as the compounding ratio in Table 1.

[evaluation]
Freeness, basis weight, ash content, whiteness, color tone (L *, a *, b *), blank paper opacity, rigidity, Cobb water absorption, and drip water absorption of each newspaper obtained by the above method. And the degree of oil absorption was measured. These results are shown in Table 2.

In addition, each newspaper obtained by the above method was evaluated for fluffing, uneven ink absorption, accumulation of paper dust on a blanket, ink drying property, color reproducibility, and strike-through. The results of these evaluations are shown in Table 3.

As shown in Tables 1 to 3, in particular, each newspaper paper of Examples 1 to 13 has a high evaluation of color reproducibility, and is an offset printing ink consisting of four colors of yellow, red, indigo and ink processes. It can be seen that it has high-saturation color reproducibility when printed using. Further, each of the newspapers of Examples 1 to 13 has high opacity and sufficient whiteness. Further, it can be seen that each of the newspapers of Examples 1 to 13 has less paper dust accumulation on the blanket and can sufficiently withstand high-speed printing by a rotary press. Further, each of the newspapers of Examples 1 to 13 has less uneven ink absorption and excellent ink drying property. In addition, it can be seen that each of the newspapers of Examples 1 to 13 has less fluffing and less strike-through. That is, it can be seen that each of the newspapers of Examples 1 to 13 has excellent printability.

The newspaper paper of the present invention is suitably used as a newspaper paper having high saturation color reproducibility and high opacity when printed using an offset printing ink consisting of four colors of yellow, red, indigo and black processes. be able to.

Claims (3)

Newspaper with a filling material added to the pulp.
The whiteness is 70% or more and 80% or less,
The color tone has a brightness of 85 or more and 95 or less, an a value of -0.7 or more and -0.5 or less, and a b value of 0.2 or more and 1.8 or less.
The basis weight is 45 g / m ² or more and 60 g / m ² or less .
Newspaper paper characterized by a drip water absorption degree of 15 seconds or more and 40 seconds or less . The content of coniferous bleached kraft pulp in the above pulp is 16% by mass or more and 24% by mass or less, the content of broadleaf tree bleached kraft pulp is 18% by mass or more and 26% by mass or less, and the content of used paper pulp is 24% by mass or more and 32% by mass. % Or less, the content of mechanical pulp is 26% by mass or more and 34% by mass or less,
The newspaper according to claim 1, which contains calcium carbonate having a volume average particle diameter of 1.0 μm or more and 2.0 μm or less as the filler. The above mechanical pulp is chemithermomechanical pulp,
The newspaper according to claim 1 or 2, wherein the ash content is 7% by mass or more and 20% by mass or less.