JP2023121212A - Coated paper for printing - Google Patents

Abstract

To provide coated paper for printing which has glossy feeling in a printed part, good blister resistance, resistance against weak contrast, and golden red reproducibility.SOLUTION: Coated paper for printing has base paper containing wood pulp and a filler, a first coating layer containing a white pigment and a binder on at least one surface of the base paper, and a second coating layer containing a white pigment and a binder with respect to the outside of the first coating layer with the base paper as a reference, wherein the white pigment of the first coating layer contains heavy calcium carbonate and kaoline, the white pigment of the second coating layer contains light calcium carbonate, heavy calcium carbonate, kaoline and an organic pigment, L* shown by an L*a*b* color system defined by CIE is 92.0 or more, a* is 0.00 or more and 1.70 or less, and b* is -2.00 or more and 0.00 or less.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to a coated printing paper suitable for multicolor offset rotary printing.

While printing machine manufacturers are announcing digital printing machines, in the printing industry, offset printing machines are still used for magazines, books, art books, photo books, art books, art books, mock books, booklets, catalogs, flyers and pamphlets. of commercial print production. A web offset press is used for mass production of commercial prints. Paper used for commercial printing is not limited to glossy paper and matte paper. In recent years, paper has various qualities in terms of glossiness, matteness, degree of smoothness, color tone, feel to the touch, and the like. Conventionally, catalogs, art books, photo books, art books, art books and Mook books use coated paper for printing with good whiteness and glossiness. However, the visibility of characters is poor on coated printing paper with high glossiness. A recent trend, particularly in catalogs and Mook books, is to use coated printing paper that has a dull tone or semi-gloss tone and a good glossy feeling in the printed area. This is because such a coated printing paper has good print quality of photographs and patterns and good visibility of characters.

For example, an undercoat layer containing a pigment and an adhesive and a topcoat layer are provided on a base paper, the base paper contains an organic compound that inhibits the interfiber bonding of pulp, and the undercoat layer contains pigments such as Delaminated clay having a volume distribution average particle size of 3.5 to 20 μm is contained in 50 parts by weight or more per 100 parts by weight of the pigment, and the topcoat layer contains 100 parts by weight of kaolin having a volume distribution average particle size of 0.80 μm or less. A dull-tone coated paper characterized by containing 70 parts by weight or more per part and having a coated paper density of 1.00 g/cm ³ or less is known (see, for example, Patent Document 1). Such a dull-tone coated paper is bulky and has a rough feel to the touch, but also has a high glossiness in the printed area and little minute gloss unevenness in the image area.

JP-A-2005-133278

Offset printing presses include sheet-fed printing presses and rotary printing presses. A rotary printing press is characterized by high-speed, large-volume printing using roll-shaped printing paper. The offset rotary press is equipped with a dryer because it is necessary to dry the ink before winding the paper after printing or before cutting and folding after printing. As a problem unique to offset rotary printing, the moisture inside the printing paper and/or the solvent component in the ink component that has permeated inside the printing paper cannot escape, and the gas that vaporized in the dryer cannot escape, resulting in the phenomenon that the printing paper swells. have blisters. Blistering is likely to occur when the paper is coated printing paper and/or when printing multicolor images and images with high color density.

In the offset rotary printing press, once the web is mounted on the printing press and transport is started, it cannot be repeated. Coated printing paper having a coating layer has improved printability due to smoothness, ink receptivity, and the like, which are improved by the coating layer, compared to uncoated printing paper. On the other hand, in offset rotary presses, a soft rubber blanket is used to transfer ink to the printing paper so that it can be sufficiently inked in the thickness direction of the printing paper. It is not easily affected by smoothness. Rather, when printing on coated printing paper with an offset rotary press, excessive coloring may blur the difference in brightness or color in the printed portion, resulting in a weak contrast.

"Golden red" is a color often used for conspicuous parts in commercial printed matter. Special color ink is often used for gold red, and the hue is mainly expressed by a mixture of 90% to 100% magenta and 100% yellow. In special color printing of gold and red, the DIC color number DIC159 or DIC565 may be instructed to the printing company. In printing, the hue and color development are important so that the gold-red printed on the coated paper for printing becomes the required gold-red.

SUMMARY OF THE INVENTION In view of the above, an object of the present invention is to provide a coated printing paper that has a glossy feeling in printed areas, good blistering resistance, low contrast resistance and gold-red reproducibility.

The present inventors have made intensive studies to solve the above problems, and as a result, the object of the present invention is achieved by the following.
a base paper containing wood pulp and filler; a first coating layer containing a white pigment and a binder on at least one side of said base paper; a second coating layer containing a white pigment and a binder, the white pigment of the first coating layer containing heavy calcium carbonate and kaolin, the white pigment of the second coating layer containing light calcium carbonate, Contains heavy calcium carbonate, kaolin, and organic pigments, and has L ^* of 92.0 or more, a ^* of 0.00 or more and 1.70 or less, and b ^* defined by the CIE in L ^* a ^* b ^* color system. is -2.00 or more and 0.00 or less.

According to the present invention, the coated printing paper can have good printed area glossiness, blister resistance, weak contrast resistance, and gold-red reproducibility.

The present invention will be described in detail below.
The coated printing paper comprises a base paper containing wood pulp and a filler, a first coating layer on at least one side of the base paper, and a base paper on the outside of the first coating layer and a second coating layer. That is, the coated printing paper has a base paper, a first coating layer and a second coating layer in this order. The printing surface of the coated printing paper that exhibits the effects of the present invention is the surface having the first coating layer and the second coating layer. The coated printing paper can have the first coating layer and/or the second coating layer on the opposite side of the base paper. Since commercial printed matter is usually double-sided, in at least one embodiment, the coated paper for printing is the first coating layer on both sides of the base paper and the first coating on the basis of the base paper. Each of the outer layers has a second coating layer.
When the first coating layer and the second coating layer are provided only on one side of the base paper, the other side of the base paper without the first coating layer and the second coating layer is conventionally known can be provided with a backcoat layer of For example, the back coat layer is provided to prevent the coated printing paper from curling.

In some embodiments, the coated printing paper is optionally between the base paper and the first coating layer and/or the first coating layer for purposes such as improving printability and interlaminar strength. and the second coating layer, there is an intermediate layer containing a white pigment and a binder or containing a resin. In at least one embodiment, there is no intermediate layer. The reason for this is that the manufacturing cost is excellent.

The above wood pulp is a pulp conventionally known in the papermaking field. Wood pulp includes, for example, chemical pulps such as LBKP (Leaf Bleached Kraft Pulp) and NBKP (Needle Bleached Kraft Pulp), GP (Groundwood Pulp), PGW (Pressure GroundWood pulp), RMP (Refiner Mechanical Pulp), TMP (ThermoMechanical Pulp). ), mechanical pulp such as CTMP (ChemiThermoMechanical Pulp) and CMP (ChemiMechanical Pulp), semi-chemical pulp such as CGP (ChemiGroundwood Pulp), waste paper pulp such as DIP (DeInked Pulp), and generated in paper mills Pulp obtained by defibrating waste paper (Spoilage) can be mentioned.
In some embodiments, the base paper contains non-wood pulp conventionally known in the papermaking art in addition to the wood pulp described above. The reason for this is the effective use of plant resources. Raw materials for non-wood pulp include, for example, woody basts such as paper mulberry, mitsumata and gampi, herbaceous basts such as flax, hemp and kenaf, leaf fibers such as Manila hemp, abaca and sisal hemp, rice straw, wheat straw, and sugarcane. Mention may be made of monocotyledonous plants such as bacchus, bamboo and esparto, and seed hairs such as cotton and linters.
In some embodiments, the base paper is 90% or more by weight wood pulp to pulp of the base paper. In at least one embodiment, the base paper does not contain non-wood pulp. These reasons are excellent in manufacturing cost.

The freeness of the wood pulp is not particularly limited. The freeness is the CSF freeness obtained according to ISO5627-2:2001 "Pulps-Determination of drainage-Part 2 Canadian Standard freeness method". In some embodiments, the wood pulp has a freeness of no less than 380 ml and no more than 530 ml. The reason for this is that the strength and smoothness of the resulting base paper are well balanced with dimensional stability.

The above fillers are white pigments conventionally known in the paper industry. Examples of fillers include light calcium carbonate, ground calcium carbonate, kaolin, clay, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc sulfide, zinc carbonate, satin white, aluminum silicate, activated clay, diatomaceous earth, Inorganic pigments such as silica, alumina, aluminum hydroxide, lithopone, zeolite, magnesium carbonate, and magnesium hydroxide are added to styrene resin, acrylic resin, vinyl acetate resin, olefin resin, vinyl chloride resin, urea resin and Organic pigments of various shapes such as medium-filled, hollow, bowl-shaped and confetti-shaped can be mentioned, which are made of various resins such as melamine-based resins. Moreover, a microcapsule etc. can be mentioned as an organic pigment. The filler is one or more selected from the group consisting of these.

In some embodiments, the base paper contains talc and precipitated calcium carbonate as fillers. In at least one embodiment, the base paper contains talc and light calcium carbonate as fillers, and the total content of talc and light calcium carbonate is 80% by mass or more relative to the filler in the base paper. The reason for these is that the blister resistance of the coated printing paper tends to be improved.

Talc is conventionally known in the papermaking art.
Talc includes naturally derived substances and synthetic substances, and its basic structure is a sandwich of a tetrahedral sheet in which Si—O tetrahedrons are two-dimensionally continuous and an octahedral sheet in which Mg—(OH) octahedrons are two-dimensionally continuous. It is a layered clay mineral represented by the chemical formula Mg ₃ Si ₄ O ₁₀ (OH) ₂ , which is layered at a ratio of 2:1. In addition, talc has characteristics of cleavability due to the weak bond between the 2:1 sandwich-like layer units, softness (Mohs hardness 1) and slipperiness. Clay minerals including talc are generally charged by substituting Mg2+ of the octahedral sheet with another metal ion having a different partial valence. In talc, Si ⁴⁺ can replace Al ³⁺ in tetrahedral sheets or Mg ²⁺ can replace Fe ³⁺ , Fe ²⁺ or Al ³⁺ in octahedral sheets. However, in talc, the very small amount of substitution is close to neutrality, resulting in hydrophobic behavior.

Light calcium carbonate is conventionally known in the papermaking field.
Light calcium carbonate is a synthetic calcium carbonate chemically produced from limestone as a raw material, and has a relatively uniform shape and a relatively narrow particle size distribution. In addition, light calcium carbonate has a crystal structure and a specific refractive index. In addition, light calcium carbonate has a larger apparent specific gravity and specific surface area than heavy calcium carbonate described below.

In some embodiments, the base paper contains 100 parts by weight or more and 200 parts by weight or less of filler with respect to 1000 parts by weight of pulp in the base paper. In some embodiments, the base paper contains talc and light calcium carbonate in a mass ratio of talc:light calcium carbonate=6:4 to 4:6. The reason for these is that the blister resistance of the coated printing paper tends to be improved.

In addition to the pulp and filler, the base paper may further contain a sizing agent, a fixing agent, a retention agent, a cationizing agent, a binder, a paper strength agent, a bulking agent, a pigment dispersant, a thickener, a fluidity improver, Defoamers, foam inhibitors, release agents, foaming agents, penetrants, colorants, fluorescent brighteners, UV absorbers, antioxidants, preservatives, anti-fouling agents, water-resistant agents, wet paper strength agents , and various additives such as dry paper strength agents.

The base paper can be obtained by using a conventionally known paper machine to make a paper stock containing pulp, fillers and, if necessary, various additives. Examples of paper machines include Fourdrinier paper machines, twin wire paper machines, combination paper machines, cylinder paper machines, Yankee paper machines, and the like.

The base paper can be subjected to a size press treatment with a sizing fluid containing a surface sizing agent.
Surface sizing agents are conventionally known in the papermaking art. Examples of surface sizing agents include various starches and polyvinyl alcohol.
Size press processing can be accomplished by any size press conventionally known in the papermaking art. The size press includes, for example, an incline size press, a horizontal size press, and a film transfer system including a rod metering size press, a roll metering size press, and a blade metering size press. Mention may be made of sizers and film presses, and of roll metering size presses gate roll coaters. Other examples include bill blade coaters, twin blade coaters, velvapa coaters, tab size presses, calendar size presses, and the like.

The base paper can undergo calendering.
Calendering is a process for smoothing and averaging the thickness of paper by passing it between rolls. The apparatus used for calendering is conventionally known in the field of papermaking, and examples thereof include machine calenders, soft nip calenders, super calenders, multistage calenders and multinip calenders.

The method of providing the coating layers such as the first coating layer, the second coating layer, and the back coat layer on the base paper is not particularly limited. Examples of the method include a method of coating and drying each coating layer coating liquid using a conventionally known coating apparatus and drying apparatus in the field of coated paper. Examples of coating equipment include comma coater (registered trademark), film press coater, rod coater, air knife coater, rod blade coater, bar coater, blade coater, gravure coater, curtain coater, E bar coater, and size press. be able to. Examples of the drying device include hot air dryers such as straight tunnel dryers, arch dryers, air loop dryers, sine curve air float dryers, infrared heating dryers, and microwave dryers.

At each stage of applying the first coating layer to the base paper and/or the second coating layer to the first coating layer, the coated printing paper can be subjected to calendering. The equipment used for calendering is the same as above.

In some embodiments, the coating weight of the first coating layer of the coated printing paper is 5 g/m ² or more and 10 g/m ² or less in dry solid content. In some embodiments, the coating amount of the second coating layer of the coated printing paper is 4 g/m ² or more and 9 g/m ² or less in dry solid content. In at least one embodiment, the coated printing paper has a dry solid content of 5 g/m 2 or more and 10 g/m ² or less for the first coating layer and a coating amount for the second coating layer of 5 g/m 2 or more and 10 g/m ² or less. The solid content is 4 g/m ² or more and 9 g/m ² or less, and the coating amount of the second coating layer is less than that of the first coating layer.
These reasons are that the blister resistance, low contrast resistance and/or gold-red reproduction of the coated printing paper are improved.

The first coating layer and the second coating layer contain a white pigment and a binder.
White pigments are conventionally known in the coated paper art. Examples of white pigments include light calcium carbonate, heavy calcium carbonate, kaolin, clay, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc sulfide, zinc carbonate, satin white, aluminum silicate, activated clay, and diatomaceous earth. , inorganic pigments such as silica, alumina, aluminum hydroxide, lithopone, zeolite, magnesium carbonate and magnesium hydroxide, styrene resins, acrylic resins, vinyl acetate resins, olefin resins, vinyl chloride resins, urea resins and Organic pigments of various shapes such as medium-filled, hollow, bowl-shaped and confetti-shaped can be mentioned, which are made of various resins such as melamine-based resins. Moreover, a microcapsule etc. can be mentioned as an organic pigment.

White pigments in the first coating layer include ground calcium carbonate and kaolin. Also, the white pigment in the second coating layer includes light calcium carbonate, heavy calcium carbonate, kaolin and organic pigments. The coated printing paper has a first coating layer containing heavy calcium carbonate and kaolin as white pigments, and a second coating layer containing light calcium carbonate, heavy calcium carbonate, kaolin and an organic pigment as white pigments. With this configuration, blister resistance, weak contrast resistance, and gold-red reproducibility can be obtained. Moreover, the coated paper for printing can have a glossy feeling in the printed part by making the white pigments of the first coating layer and the second coating layer have the above composition. Although the reason for this is unknown, the present inventors speculate that it is a synergistic effect due to the attributes of light calcium carbonate, heavy calcium carbonate, kaolin and organic pigments.
In some embodiments, the first coating layer has a total content of ground calcium carbonate and kaolin of 90% by mass or more with respect to the white pigment in the first coating layer, and the second coating layer is , the total content of light calcium carbonate, heavy calcium carbonate, kaolin and organic pigment is 90% by mass or more with respect to the white pigment in the second coating layer. These reasons are that the blister resistance, low contrast resistance and/or gold-red reproduction of the coated printing paper are improved.

The precipitated calcium carbonate is the same as that explained in the above filler, and the explanation is omitted here.
Ground calcium carbonate is conventionally known in the papermaking arts. Heavy calcium carbonate is naturally derived calcium carbonate obtained by directly pulverizing limestone, which is the main component, and has a non-uniform shape, and normally has a relatively wide range of particle size distribution. In addition, heavy calcium carbonate has a smaller apparent specific gravity and specific surface area than light calcium carbonate.

Kaolin is conventionally known in the papermaking art.
Kaolin is a clay mineral, generally based on Al ₂ O ₃ .2SiO ₂ .2H ₂ O, having a structure of alternating layers of silicon-oxygen and aluminum-hydroxyl. Kaolin is industrially refined and processed from naturally occurring kaolin raw ore such as kaolinite, nacrite, dickite, halloysite, hydrated halloysite, and the like, for example, pulverization, washing, iron removal and classification. It is manufactured through the process of In addition, kaolin includes delaminated kaolin that is made into a thin plate by applying shear force to improve the aspect ratio, engineered kaolin adjusted to have a sharp particle size distribution, and calcined kaolin with enhanced cohesion. Those with high workability are also included. Also, kaolin is a tabular particle, and normally the planar portion of the particle is negatively charged and the edge portion is positively charged.

Organic pigments are conventionally known in the coated paper art.
Organic pigments are white pigments composed of resins of organic compounds and come in various shapes. In some embodiments, the organic pigment is a hollow organic pigment. The reason for this is that the weak contrast resistance and/or gold-red reproduction of the coated printing paper are improved. Hollow organic pigments are organic pigments having one or more void (hollow) portions inside the particles.

In some embodiments, the first coating layer contains ground calcium carbonate and kaolin in a mass ratio of ground calcium carbonate:kaolin=65:35 to 85:15. . In some embodiments, the second coating layer is such that the content of light calcium carbonate, heavy calcium carbonate, kaolin and organic pigment in the second coating layer is 100 mass of white pigment in the second coating layer 35 parts by mass to 55 parts by mass of light calcium carbonate, 18 parts by mass to 38 parts by mass of heavy calcium carbonate, 10 parts by mass to 30 parts by mass of kaolin, and 4 parts by mass to 16 parts by mass of organic pigment is. These reasons are that the blister resistance, low contrast resistance and/or gold-red reproduction of the coated printing paper are improved.
In at least one embodiment, the first coating layer contains ground calcium carbonate and kaolin in a mass ratio of ground calcium carbonate:kaolin = 65:35 to 85:15, In addition, the second coating layer contains light calcium carbonate, heavy calcium carbonate, kaolin, and an organic pigment in a mass ratio of 35 parts by mass or more and 55 parts by mass or less of light calcium carbonate, and 18 parts by mass of light calcium carbonate. 10 parts by mass to 30 parts by mass of kaolin, and 4 parts by mass to 16 parts by mass of the organic pigment.

The binder is a water-dispersible or water-soluble binder conventionally known in the coated paper art. Examples of water-dispersible binders include styrene-based resins such as styrene-butadiene-based copolymer resins, conjugated diene-based copolymer resins such as (meth)acrylonitrile-butadiene-based copolymer resins, and (meth)acrylate butadiene-based copolymer resins. , acrylic resins such as (meth)acrylic acid ester styrene copolymer resins and (meth)acrylate ester polymer resins, vinyl copolymers such as ethylene vinyl acetate copolymer resins and vinyl chloride vinyl acetate copolymer resins Examples include resins, polyurethane resins, alkyd resins, unsaturated polyester resins, modified resins using these various monomers, and thermosetting synthetic resins such as urea resins and melamine resins. Examples of water-soluble binders include starches, cellulose derivatives such as methyl cellulose, carboxymethyl cellulose, and hydroxyethyl cellulose, polyvinyl alcohol (generic name including unmodified polyvinyl alcohol and denatured polyvinyl alcohol such as silanol-denatured polyvinyl alcohol), and casein. and gelatin or modified products thereof, natural polymer resins such as soybean protein, pullulan, gum arabic, gum karaya, albumin or derivatives thereof, sodium alginate, maleic acid resins and the like.

In some embodiments, the binder of the first coating layer is a combination of starches and a styrene-butadiene-based copolymer resin. In some embodiments, the binder for the second coating layer is a combination of polyvinyl alcohol and styrene-butadiene-based copolymer resin. The reason for these is that the synergistic effect of the binder properties tends to improve the blister resistance of the coated printing paper. The attributes are, for example, that a styrene-butadiene-based copolymer resin has excellent binding properties for white pigments, starches have excellent gelling properties and stiffness-imparting properties, and polyvinyl alcohol has excellent crystallizing properties and coating properties.
In at least one embodiment, the binder in the first coating layer is one or more selected from the group consisting of starches and a styrene-butadiene-based copolymer resin, and the binder in the second coating layer is polyvinyl alcohol. One or two or more selected from the group consisting of and a styrene-butadiene-based copolymer resin.

In some embodiments, the content of the binder in the first coating layer is 5 parts by mass or more and 15 parts by mass or less with respect to 100 parts by mass of the white pigment in the first coating layer. In some embodiments, the content of the binder in the second coating layer is 8 parts by mass or more and 28 parts by mass or less with respect to 100 parts by mass of the white pigment in the second coating layer. The reason for these is that the blister resistance tends to be improved.
In at least one embodiment, the content of the binder in the first coating layer is 5 parts by mass or more and 15 parts by mass or less with respect to 100 parts by mass of the white pigment in the first coating layer, and the second coating The content of the binder in the layer is 8 parts by mass or more and 28 parts by mass or less with respect to 100 parts by mass of the white pigment in the second coating layer.

In addition to the white pigment and the binder, the first coating layer and the second coating layer may optionally contain various additives conventionally known in the field of coated paper, in addition to the white pigment and the binder. Examples of additives include thickeners, fluidity improvers, antifoaming agents, foaming agents, lubricants, penetrants, colorants, fluorescent brighteners, ultraviolet absorbers, antioxidants, preservatives, and antibacterial agents. , printability improvers, and the like.

In some embodiments, the second coating layer contains an optical brightener. The reason for this is that the weak contrast resistance is improved. Optical brighteners are conventionally known in the coated paper art. Examples of fluorescent brighteners include fluorescein-based compounds, thioflavin-based compounds, eosin-based compounds, rhodamine-based compounds, coumarin-based compounds, imidazole-based compounds, oxazole-based compounds, triazole-based compounds, carbazole-based compounds, pyridine-based compounds, and imidazolone-based compounds. compounds, naphthalic acid compounds, and stilbene compounds such as stilbene disulfonic acid derivatives, stilbene tetrasulfonic acid derivatives, and stilbene hexasulfonic acid derivatives. In some embodiments, the optical brightener is a stilbene-based compound conventionally known in the papermaking arts.
Fluorescent whitening agents are compounds that absorb invisible ultraviolet rays and convert them into visible bluish-white light (fluorescence), and are additives that increase the apparent whiteness of paper. A coating layer containing an optical brightener increases the apparent whiteness of the paper due to the fluorescence caused by the optical brightener. As a result of trial and error, the present inventors have found that the inclusion of a fluorescent brightening agent in the second coating layer provides the coated printing paper with low contrast resistance. That is, coated printing paper containing a fluorescent brightening agent in the second coating layer not only increases apparent whiteness, but also provides weak contrast resistance.

In some embodiments, the base paper, the first coating layer and/or the second coating layer contain colorants selected from the group consisting of colored pigments and colored dyes. The colorant is not particularly limited, and is selected to provide the hues described below. Wood pulp and white pigments such as kaolin are not strictly white and are slightly colored, so adjust for wood pulp and white pigments. Then, the coated printing paper is a base paper, the first coating layer and / or the second coating layer contains a colorant, so that the wood pulp of the base paper, the white pigment of the first coating layer and / or Combined with the white pigment of the second coating layer, L ^* indicated by the CIE-defined L * a ^* b ^* color system is 92.0 or more, ^{a * is} 0.00 or more and 1.70 or less, and b ^* is −2.00 or more and 0.00 or less.
In the L ^* a ^* b ^* color system defined by the CIE, L ^* indicates luminance, plus a ^* indicates chromaticity on the red side, minus a ^* indicates chromaticity on the green side, and plus b ^* indicates chromaticity on the yellow side, and negative b ^* indicates chromaticity on the blue side. A coated printing paper having L ^* a ^* b ^* within the above range has a high brightness and a pale gray color. A coated printing paper having L ^* a ^* b ^* within the above range can provide weak contrast resistance and gold-red reproducibility.

In some embodiments, the coated printing paper has a 75 degree specular gloss based on ISO 8254-1:1999 "Paper and board-Measurement of specular gloss-Part 1:75 degree gloss with a converging beam, TAPPI method" is 35% or more and 75% or less. When the 75-degree specular glossiness is within the above range, the coated printing paper has a semi-gloss tone.
The glossiness of the coated printing paper can be adjusted by a method conventionally known in the coated paper field. The glossiness of the coated printing paper depends on, for example, the calendering conditions of the base paper, the type and content of the white pigment in the first coating layer and the second coating layer, and the calendering conditions of each coating layer. Adjustable. In general, treatments for increasing the smoothness of coated printing paper tend to increase glossiness. In addition, with white pigments, the glossiness usually increases as the kaolin content increases, and the glossiness decreases as the heavy calcium carbonate content increases.

In some embodiments, the coated printing paper comprises a base paper containing wood pulp and filler, a first coating layer containing a white pigment and a binder on at least one side of said base paper, and A second coating layer containing a white pigment and a binder on the outside of the first coating layer, wherein the white pigment of the first coating layer contains heavy calcium carbonate and kaolin, The white pigment of the second coating layer contains light calcium carbonate, heavy calcium carbonate, kaolin and an organic pigment, and L ^* indicated by L ^* a ^* b ^* color system defined by CIE is 92.0 or more, a ^* is 0.00 or more and 1.70 or less and b ^* is -2.00 or more and 0.00 or less, and the second coating layer further contains a fluorescent brightening agent.

Also, in some embodiments, the coated printing paper comprises a base paper containing wood pulp and a filler; a first coating layer containing a white pigment and a binder on at least one side of the base paper; Based on the base paper, a second coating layer containing a white pigment and a binder is provided on the outside of the first coating layer, and the white pigment of the first coating layer contains heavy calcium carbonate and kaolin The content mass ratio of heavy calcium carbonate and kaolin in the first coating layer is heavy calcium carbonate:kaolin = 65:35 to 85:15, and the white pigment in the second coating layer is light carbonate Contains calcium, heavy calcium carbonate, kaolin and organic pigment, and the content of light calcium carbonate, heavy calcium carbonate, kaolin and organic pigment in the second coating layer is 100 mass of white pigment in the second coating layer 35 parts by mass to 55 parts by mass of light calcium carbonate, 18 parts by mass to 38 parts by mass of heavy calcium carbonate, 10 parts by mass to 30 parts by mass of kaolin, and 4 parts by mass to 16 parts by mass of organic pigment and L ^* indicated by the L ^* a ^* b ^* color system defined by the CIE is 92.0 or more, a ^* is 0.00 or more and 1.70 or less, and b ^* is -2.00 or more and 0.00 It is below.

In at least one embodiment, the coated printing paper comprises a base paper containing wood pulp and filler, a first coating layer containing a white pigment and a binder on at least one side of said base paper, a base paper A second coating layer containing a white pigment and a binder on the outside of the first coating layer, wherein the white pigment of the first coating layer contains heavy calcium carbonate and kaolin, The content mass ratio of heavy calcium carbonate and kaolin in the first coating layer is heavy calcium carbonate:kaolin = 65:35 to 85:15, and the white pigment in the second coating layer is light calcium carbonate, Contains heavy calcium carbonate, kaolin and organic pigment, and the content of light calcium carbonate, heavy calcium carbonate, kaolin and organic pigment in the second coating layer is less than 100 parts by mass of white pigment in the second coating layer 35 parts by mass to 55 parts by mass of light calcium carbonate, 18 parts by mass to 38 parts by mass of heavy calcium carbonate, 10 parts by mass to 30 parts by mass of kaolin, and 4 parts by mass to 16 parts by mass of an organic pigment. , L ^* indicated by the L ^* a ^* b ^* color system defined by the CIE is 92.0 or more, a ^* is 0.00 or more and 1.70 or less, and b ^* is -2.00 or more and 0.00 or less and the second coating layer further contains a fluorescent whitening agent.

The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to these examples. Here, "parts by mass" and "% by mass" respectively represent "parts by mass" and "% by mass" of the amount of dry solids and the amount of substantial components. The amount of coating indicates the amount of dry solids.

Coated printing papers of Examples and Comparative Examples were prepared by the following procedure.

<Base paper>
A paper stock was prepared according to the following contents.
LBKP (freeness 430 mlcsf) 750 parts by mass NBKP (freeness 480 mlcsf) 250 parts by mass Talc 70 parts by mass Light calcium carbonate 70 parts by mass Aluminum sulfate 10 parts by mass Alkylketene dimer sizing agent 0.7 parts by mass Cationic starch 9 parts by mass Part Polyacrylamide-based retention agent 0.1 part by mass Colorant As appropriate

The above stock was made into paper by a Fourdrinier paper machine, and coated on both sides by a size press using starch as a surface sizing agent. The coating amount was adjusted to 1 g/m ² . The size press was followed by calendering to obtain a base paper with a basis weight of 55 g/m ² .

<Coating liquid for first coating layer>
A coating liquid for the coating layer was prepared as follows.
Starch 3 parts by mass SBR 7 parts by mass Lubricant (calcium stearate) 0.4 parts by mass Polyamide-based printability improver 0.5 parts by mass Coloring agent As appropriate Blended according to the above contents , and water to adjust the concentration to 60% by mass.

<Coating layer coating solution for second coating layer>
A coating liquid for the coating layer was prepared as follows.
White pigment type and number of parts are shown in Tables 1 to 3 PVA 2 parts by mass SBR 18 parts by mass Fluorescent whitening agent 0 parts by mass / 0.3 parts by mass Lubricant (calcium stearate) 0.4 parts by mass Polyamide-based printability improver 0 .5 parts by mass Colorant Appropriately blended according to the above contents, mixed and dispersed with water to adjust the concentration to 46% by mass.

The materials used are as follows.
Talc from Hyogo Clay Co., Ltd. was used as the talc. Tamapearl (registered trademark) TP-123 manufactured by Okutama Kogyo Co., Ltd. was used as light calcium carbonate. WH90 manufactured by Hyogo Clay Co., Ltd. was used as heavy calcium carbonate. Hydrafine 90 manufactured by Nissei Kyoei Co., Ltd. was used as kaolin. Mizusawa Kagaku Kogyo Co., Ltd. Mizukasil (registered trademark) P-73 was used as silica. As organic pigment 1, JSR AE850, which is a hollow white organic pigment, was used. As the organic pigment 2, medium density organic pigment L8801 manufactured by Asahi Kasei Co., Ltd. was used. As PVA (polyvinyl alcohol), JF-04 manufactured by Nippon Vinyl Acetate and Poval Co., Ltd. was used. P140 from Oji Corn Starch Co., Ltd. was used as the starch. Asahi Kasei E1585 was used as SBR (styrene-butadiene-based copolymer resin). Leucophor (registered trademark) U liq, which is a stilbene compound manufactured by Clariant Co., Ltd., was used as the fluorescent brightener.

<Coated paper for printing>
The coating liquid for the first coating layer was applied to both sides of the base paper using a blade coater as a coating device, and dried using a hot air dryer. Subsequently, on both sides of the first coating layer, the coating layer coating solution for the second coating layer is coated using an air knife coater and dried using a hot air dryer to form a coating for printing. I got the craft paper. The coating conditions were adjusted so that the coating weight of the first coating layer was 8 g/m ² and the coating weight of the second coating layer was 7 g/m ² .

The following items were evaluated for the obtained coated printing paper.

<Blister resistance>
Using an offset rotary press (Mitsubishi Heavy Industries, Lithopia (registered trademark) BT-2-600 type), four colors (CMYK ) Printing was done on one side of the coated printing paper. Printing was carried out at a printing speed of 300 m/min and a paper surface temperature of 120° C. at the outlet of the dryer. CMYK, red, blue, and green solid images, gold and red solid images, portrait images, landscape photos, and evaluation images in which character images are randomly arranged were used for printing. The blister resistance was evaluated sensorily according to the following criteria by visually observing the occurrence of blisters in the printed matter obtained. In the present invention, a coated printing paper rated as A or B is considered to have good blister resistance.
A: Blisters are generally not observed.
B: Although no blister, a slight bulging feeling is observed.
C: Inferior to B above, the presence of blisters is slightly observed.
D: Inferior to C above, presence of blisters is observed.

<Weak contrast resistance>
Using an offset rotary press (Mitsubishi Heavy Industries, Lithopia BT-2-600 type), 4-color (CMYK) printing is performed using offset rotary printing inks (Dainippon Ink and Chemicals, Web World Terrace N). for one side of the coated paper. Printing was carried out at a printing speed of 300 m/min and a paper surface temperature of 120° C. at the outlet of the dryer. CMYK, red, blue, and green solid images, gold and red solid images, portrait images, landscape photos, and evaluation images in which character images are randomly arranged were used for printing. Weak contrast resistance was evaluated sensorily according to the following criteria by visually observing the difference in brightness and vividness of the image in the obtained printed matter. In the present invention, a coated printing paper having an evaluation of A or B is considered to have good weak contrast resistance.
A: The difference in brightness and vividness of the image is very clear and good.
B: Although inferior to the above A,
The difference in brightness and vividness of the image is clear and generally good.
C: Although inferior to B above,
The difference in brightness and vividness of the image is generally clear and has a practical quality.
D: Inferior to the above C, and the difference in brightness and vividness of the image is insufficient or somewhat insufficient.

<Gold red reproducibility>
Using an offset rotary press (Mitsubishi Heavy Industries, Lithopia BT-2-600 type), 4-color (CMYK) printing is performed using offset rotary printing inks (Dainippon Ink and Chemicals, Web World Terrace N). for one side of the coated paper. Printing was carried out at a printing speed of 300 m/min and a paper surface temperature of 120° C. at the outlet of the dryer. CMYK, red, blue, and green solid images, gold and red solid images, portrait images, landscape photos, and evaluation images in which character images are randomly arranged were used for printing.
The printed matter was handed over to 10 test subjects, and the test subjects evaluated the color of the gold-red solid image in comparison with DIC color number DIC159 or DIC565 from the viewpoint of hue and color development according to the following criteria. The final score was obtained by averaging the evaluation results of 10 people and rounding off to the nearest whole number. In the present invention, a coated printing paper rated 3 or 4 is considered to have good gold-red reproduction.
4: No problem in hue and color development.
3: Although inferior to 4 above, there is generally no problem with hue and color development.
2: Although inferior to 3 above, it has practical quality in terms of hue and color development.
1: Inferior to 2 above, not reaching practical quality in terms of hue and color development.

The evaluation results are shown in Tables 1-3.

Each example and each comparative example had a semi-gloss tone. In addition, as a result of visually observing the glossiness of the printed part, Examples 1 to 30 and Comparative Examples 1 to 5 and 10 corresponding to the present invention are coated printing papers having sufficient glossiness of the printed part. In Examples 6 to 9 and Comparative Examples 11 to 14, the coated papers for printing did not have sufficient gloss in the printed area.

From Tables 1 to 3, Examples 1 to 30, which correspond to the present invention, are coated printing papers having a glossy feeling in printed areas, good blister resistance, weak contrast resistance, and gold-red reproducibility. I understand. On the other hand, Comparative Examples 1 to 14, which do not satisfy the configuration of the present invention, are coated printing papers that fail to satisfactorily satisfy any one of printed area glossiness, blister resistance, weak contrast resistance, and gold-red reproducibility.

Claims (1)

a base paper containing wood pulp and filler; a first coating layer containing a white pigment and a binder on at least one side of said base paper; a second coating layer containing a white pigment and a binder, the white pigment of the first coating layer containing heavy calcium carbonate and kaolin, the white pigment of the second coating layer containing light calcium carbonate, Contains heavy calcium carbonate, kaolin, and organic pigments, and has L ^* of 92.0 or more, a ^* of 0.00 or more and 1.70 or less, and b ^* defined by the CIE in L ^* a ^* b ^* color system. is -2.00 or more and 0.00 or less.