JP2012077394A - Coated paper for printing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coated paper for printing that satisfies ink-jet printability without impairing off-set printability, and more specifically, to provide a coated paper for printing suitable for an inkjet printing machine adopting a pigment ink without impairing off-set printability.SOLUTION: The coated paper for printing is provided with a coated layer comprising a pigment and a binder as main components on at least one surface of a base paper. The coated layer contains a calcium compound other than calcium carbonate and the calcium compound is contained in the coated layer on at least one surface in an amount of 3 mmol or more and 60 mmol or less in terms of calcium ion per 1 mof the base paper. As the pigment in the coated layer, ground calcium carbonate is contained in an amount of 50 pts.mass or more based on 100 pts.mass of the total pigments in the coated layer. The base paper contains calcium carbonate.

Description

  The present invention relates to a coated paper for printing. More specifically, the present invention relates to a coated paper for printing having good suitability even in commercial printing using an inkjet recording method without impairing offset print suitability.

  Inkjet recording technology advances rapidly, and printers that use inkjet recording methods (hereinafter referred to as “inkjet printers”) form color and high-quality images on recording media such as paper and film. I can do it now. Among such inkjet printers, there are large format printers used by printers and the like from small home printers. Basically, these printers are used mainly in a small number of printing sites in order to perform printing in units of one sheet.

  In recent years, application of commercial printing (hereinafter referred to as “inkjet printing”) using an inkjet recording system has begun due to further technological advances. In the commercial printing field, the number of copies is large, and printing speed is emphasized from the viewpoint of productivity and printing cost. Printing speed suitable for inkjet printing is achieved by a printing machine (hereinafter referred to as “inkjet printing machine”) having a line head in which the head for ejecting ink is fixed in the entire width direction perpendicular to the paper conveyance direction. (See, for example, Patent Document 1). Recently, rotary ink jet printers have been developed that are equipped with pigment inks having a printing speed of 15 m / min or higher, higher speeds of 60 m / min or higher, and higher speeds of 120 m / min or higher.

  Ink jet printers are particularly applied to on-demand printing because they can handle variable information. In commercial printing, fixed information is printed by an offset printer and variable information is printed by an inkjet printer.

  However, when the conventional offset printing coated paper is employed in an ink jet printer, the ink fixing properties and ink absorbability of the ink jet ink are poor. Further, there is a problem that ink absorption is insufficient and printing unevenness, printing bleeding, and in severe cases, ink flow (a phenomenon in which ink that has not been absorbed flows on the coated paper surface) occurs.

  In order to improve ink fixability and ink absorbency in ink jet printing, if the binder of the coating layer is simply reduced or a porous pigment is used in the coating layer, the coating layer strength of the coating layer is lost. For example, blank piling occurs, and the offset printability of the coated paper for printing is impaired. Accordingly, the coated paper for printing is required to have sufficient ink fixability and ink-absorbing inkjet printability without impairing offset printability.

  From the viewpoint of weather resistance, there is an increasing tendency for inkjet printers that employ pigment inks as inkjet inks. As a problem of the pigment ink, there is a printing unevenness in a printing portion. Printing unevenness is a phenomenon in which the ink absorbability of the printing coated paper varies when the printing speed is high, and the density of the fixed ink in the final printed image after the ink is dried becomes uneven. . Ink used for ink-jet printing has a low density of color material, and printing unevenness is likely to be noticeable compared to offset printing. The commercial value of the printed matter is reduced by the printing unevenness, and therefore it is required to suppress the printing unevenness.

  A special paper of an ink jet recording system in which a porous pigment having a high BET specific surface area is coated on a base paper (see, for example, Patent Document 2 and Patent Document 3) is excellent in ink fixability and ink absorbability in ink jet printing. However, these exclusive ink jet recording papers are inferior in offset printing suitability due to insufficient coating layer strength.

  In addition, as a dedicated paper for an ink jet recording method that suppresses printing unevenness of a printed image, a paper containing a water-soluble metal salt is used as a support, and an ink receiving layer on the support contains an ink jet recording sheet (for example, a protein) Patent Document 4), an ink jet recording paper having an ink receiving layer and a gloss developing layer on a support, wherein the gloss developing layer contains 5% by weight or more and 30% by weight or less of Group 2A group element chloride (for example, Patent Document 5), and inkjet recording paper having an ink-receiving layer and a gloss layer on a base material, and further provided with an overcoat layer containing a polyvalent metal salt and a penetrant (for example, see Patent Document 6) . However, these exclusive papers for the ink jet recording system are for ink jet printers, and are inferior in offset printing suitability, and do not suppress printing unevenness to a sufficiently satisfactory level in an ink jet printer. On the other hand, there is an ink jet recording paper having a coating layer mainly composed of an inorganic pigment and a binder on a base paper containing a cationic polymer (see, for example, Patent Document 7). Although the offset printability is good, it is not necessarily excellent in terms of printing unevenness of an ink jet printer.

JP 2009-23292 A Japanese Patent Laid-Open No. 3-43290 JP-A-5-254239 JP 2004-276420 A Japanese Patent Laid-Open No. 2005-161601 JP 2008-114543 A JP 2010-100039 A

  A coated paper for printing that satisfies the inkjet printability without deteriorating the offset printability has not been obtained. In particular, a coated paper for printing suitable for an ink jet printer that employs pigment ink has not been obtained without impairing offset printability.

  That is, the object of the present invention is to satisfy the following problems in the coated paper for printing. (1) Good offset printability. (2) Sufficient ink fixability and ink absorbency in ink jet printing. (3) Ink-jet printing using pigment ink, printing unevenness in the printed portion is sufficiently suppressed.

In the coated paper for printing in which a coating layer mainly composed of a pigment and a binder is provided on at least one surface of the base paper, the coating layer contains a calcium compound other than calcium carbonate, and the calcium compound Is contained in the coating layer on at least one surface per 1 m ^{2 of} printing paper in a range of 3 mmol or more and 60 mmol or less in terms of calcium ion, and heavy calcium carbonate as a pigment in the coating layer is contained in the coating layer. This can be solved by a coated paper for printing characterized in that it contains 50 parts by mass or more with respect to 100 parts by mass of the total pigment, and the base paper contains calcium carbonate.

Preferably, the calcium ion-equivalent mmol ratio (A / B) of the calcium amount A of calcium carbonate and the calcium amount B of a calcium compound other than calcium carbonate contained in 1 m ² of the coated paper for printing is 1 or more and 50 or less. .

  Preferably, the calcium compound is calcium chloride.

  As another aspect of the present invention, there is provided a printing method using an inkjet printer, the step of obtaining the above-mentioned coated paper for printing, and inkjet printing using a pigment ink on the coating layer of the coated paper for printing. Provided is a method including a step of forming a printed image at a printing speed of 15 m / min or more. Further, the present invention is a method for forming an excellent printed image, wherein an offset printing machine and / or an inkjet printing machine is provided on the coating layer of the printing coated paper, and the step of obtaining the above coated paper for printing. A method is provided that includes using to form a printed image.

  According to the present invention, it is possible to obtain a coated paper for printing having good offset printability and good ink fixing properties and ink absorbability even in ink jet printing. In particular, even with an ink jet printer equipped with pigment ink, it is possible to obtain a coated paper for printing in which printing unevenness in a printed portion is suppressed.

  Hereinafter, the coated paper for printing of the present invention will be described in detail.

  The base paper used for the coated paper for printing of the present invention includes chemical pulps such as LBKP and NBKP, mechanical pulps such as GP, PGW, RMP, TMP, CTMP, CMP and CGP, and used paper pulp such as DIP, carbonic acid It has calcium as an essential filler, and it is acidic, neutral, alkaline, etc. from paper stocks containing various additives such as sizing agents, fixing agents, retention agents, cationizing compounds, paper strength agents, etc. Paper made can be used. By using calcium carbonate as a filler, good offset printability can be obtained, and printing unevenness can be improved. In the present invention, calcium carbonate can be classified into heavy calcium carbonate and light calcium carbonate, and calcium carbonate used as a filler may be either heavy calcium carbonate or light calcium carbonate, or may be used in combination. Various fillers such as talc, clay and kaolin can be used in combination.

  In the present invention, as other additives, pigment dispersants, thickeners, fluidity improvers, antifoaming agents, antifoaming agents, mold release agents, foaming agents, penetrating agents, colored dyes, colored pigments, fluorescent whitening agents , UV absorbers, antioxidants, preservatives, antibacterial agents, water resistance agents, wet paper strength enhancers, dry paper strength enhancers, and the like are appropriately contained in the paper to the extent that the desired effects of the present invention are not impaired. You can also.

  In the present invention, the sizing degree of the base paper may be any sizing degree as long as the desired effect of the present invention is not impaired, and can be adjusted by the amount of the internal sizing agent and the coating amount of the surface sizing agent applied to the base paper. The internal sizing agent is, for example, rosin sizing agent for acidic paper, alkenyl succinic anhydride, alkyl ketene dimer, neutral rosin sizing agent or cationic styrene-acrylic sizing agent for neutral paper. . The surface sizing agent is, for example, a styrene-acrylic sizing agent, an olefinic sizing agent, or a styrene-maleic sizing agent. In particular, when applied together with a cationic compound, a cationic or nonionic surface sizing agent is preferred.

  Further, from the viewpoint of ink absorbability of the inkjet ink, when the amount of ash in the base paper is preferably 8% by mass or more and 25% by mass or less, the resulting offset printability and ink absorption unevenness are improved. More preferably, it is 10 mass% or more and 20 mass% or less.

  The amount of ash here is the ratio (% by mass) between the mass of incombustible material after subjecting the base paper to a combustion treatment at 500 ° C. for 1 hour and the absolute dry weight of the base paper before the combustion treatment. The amount of ash can be adjusted by the content of the filler in the base paper.

  In the present invention, the thickness of the base paper is not particularly limited, but is preferably 50 μm or more and 300 μm or less, more preferably 80 μm or more and 250 μm or less.

  The printing coated paper of the present invention has a coating layer mainly composed of a pigment and a binder on a base paper. By providing a coating layer, it can be differentiated from high-quality paper in terms of printing quality and appearance.

  Porous pigments such as synthetic silica used for the coating layer of special paper for the ink jet recording system can absorb ink jet ink. However, kaolin and calcium carbonate used for the coating layer of general printing coated paper hardly absorb inkjet ink because the particles themselves are not porous.

  In the present invention, the coating layer contains heavy calcium carbonate as a pigment. Content of the heavy calcium carbonate in a coating layer occupies 50 mass parts or more with respect to 100 mass parts of total pigments in a coating layer, Preferably it is 60 mass parts or more. The heavy calcium carbonate particles themselves do not absorb ink jet ink. However, the ink-jet ink can be absorbed by voids formed between particles caused by heavy calcium carbonate particles having an irregular shape. And when a coating layer contains heavy calcium carbonate 50 mass parts or more in 100 mass parts of the total pigment in a coating layer, it can have inkjet printing aptitude, without impairing offset printing aptitude. When the content of heavy calcium carbonate in the coating layer is less than 50 parts by mass, the formation of voids in the coating layer becomes insufficient, and ink jet printing suitability cannot be obtained. The reason for this is not clear, but it is considered that a relatively large number of voids are formed as compared with the regular particles because the heavy calcium carbonate is irregular.

  A conventionally well-known pigment can be used for the coating layer of this invention as pigments other than the said heavy calcium carbonate. Examples of such pigments include kaolin, light calcium carbonate, clay, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc sulfide, zinc carbonate, satin white, aluminum silicate, diatomaceous earth, calcium silicate, and silicic acid. Inorganic pigments such as magnesium, synthetic amorphous silica, colloidal silica, aluminum hydroxide, alumina, lithopone, zeolite, magnesium carbonate, magnesium hydroxide, styrene plastic pigment, acrylic plastic pigment, styrene-acrylic plastic pigment, polyethylene And organic pigments such as microcapsules, urea resins, and melamine resins.

  However, when a porous pigment having a high oil absorption such as a synthetic amorphous silica is frequently used, the coating layer strength may decrease. If the coating layer strength is lowered, troubles such as occurrence of blanking in offset printing are caused. Therefore, the average oil absorption amount of the pigment used in the coating layer is preferably 100 ml / 100 g pigment or less.

  In the present invention, the coating layer contains a calcium compound other than calcium carbonate. A calcium compound other than calcium carbonate is a water-soluble calcium compound that can be dissolved in water at 20 ° C. in an amount of 1% by mass or more. Examples of water-soluble calcium compounds include salt compounds such as calcium lactate, calcium nitrate, calcium chloride, and calcium acetate, or complex compounds such as ethylenediaminetetraacetate calcium. These may be used alone or in combination of two or more. A preferred water-soluble calcium compound is calcium chloride. It is considered that the high hygroscopicity of calcium chloride has a particularly excellent effect in suppressing printing unevenness in ink jet printing.

  As described in JP-A-2007-268926, it is known that a water-soluble polyvalent metal salt is contained in a coating layer of special paper for an ink jet recording system. Ink of an ink jet printer has a low color material concentration, and the color material is easy to move before fixing. In general, ink for ink jet printers is anionic. By containing the polyvalent metal salt, the ink can be fixed by the polyvalent metal cation generated from the polyvalent metal salt. On the other hand, a water-soluble calcium compound generates calcium ions in an aqueous solution, and calcium ions easily form a poorly water-soluble salt of calcium hydroxide or calcium carbonate. However, it has been found that printing paper containing calcium carbonate in the base paper and the coating layer can further suppress printing unevenness in ink jet printing by having a calcium compound in the coating layer. The reason for this is not clear, but printing unevenness is caused by non-uniform ink fixation and non-uniform ink absorption speed. I think that it may produce a capillary phenomenon by forming a poorly water-soluble calcium salt on the surface of calcium carbonate in a slow region. For this reason, the base paper and the coating layer need to contain calcium carbonate, and such an effect cannot be obtained from metal ions of other polyvalent metal salts.

In the present invention, the amount of calcium contained in the coating layer per 1 m ² of printing paper as a calcium compound other than calcium carbonate is in the range of 3 mmol or more and 60 mmol or less in terms of calcium ion. If it is less than this range, sufficient ink fixing properties and the effect of suppressing printing unevenness in the printed portion cannot be obtained. If it exceeds this range, not only the ink fixing property and the effect of suppressing the printing unevenness of the printed part can be obtained, but also the ink absorbability of the coated paper for printing may be lowered, which is not preferable.

  The calcium content in terms of calcium ion of calcium compounds other than calcium carbonate contained in the base paper and coating layer is peeled and pulverized between the base paper and the coating layer (in the case of both sides, separate from the front and back). Each is immersed in ultrapure water, extracted with an ultrasonic cleaner, and the amount of extracted calcium ions is obtained. The calcium content in terms of calcium ions from calcium carbonate is determined from the amount of calcium ions eluted from the base paper and the coating layer of the coated paper for printing and then eluted into 0.1N nitric acid solution. Is obtained by subtracting the amount of calcium ions extracted. The quantitative analysis method of calcium ions can be measured by a known method.

In the present invention, the calcium ion-equivalent mmol ratio (A / B) of the calcium amount A of calcium carbonate and the calcium amount B of the calcium compound other than calcium carbonate contained in 1 m ² of the coated paper for printing is 1 to 50. A range is preferable. More preferably, it is 1 or more and 30 or less. By setting it within this range, it is possible to obtain more effects of ink fixability, suppression of printing unevenness in the printed portion, or ink absorbability.

In the present invention, the coating amount of the coating layer of the coated paper for printing is not particularly limited, but from the appearance of the coated paper for printing and the ink fixing property, 2.0 g / m ^{2 to} 25.0 g / m per side. ² or less is preferable. When used by this invention, the coating amount of a coating layer shows the coating amount of dry solid content.

  In the present invention, for the purpose of improving glossiness, glossiness can be adjusted by appropriately using a plastic pigment having high gloss expression ability. Moreover, a higher glossiness can be obtained by performing a calendar process. Examples of the calendar processing apparatus at that time include a machine calendar, a super calendar, and a soft nip calendar. Moreover, it can also give gloss using the well-known cast coat method.

  In the present invention, the coating layer contains a conventionally known water-dispersible binder and / or water-soluble binder as a binder. Examples of the water dispersible binder include conjugated diene copolymer latex such as styrene-butadiene copolymer or acrylonitrile-butadiene copolymer, acrylate ester or methacrylate ester polymer, or methyl methacrylate-butadiene copolymer. Acrylic copolymer latex such as ethylene-vinyl acetate copolymer, vinyl copolymer latex such as vinyl chloride-vinyl acetate copolymer, polyurethane resin latex, alkyd resin latex, unsaturated polyester resin latex, or these Examples include, but are not limited to, a functional group-modified copolymer latex with a functional group-containing monomer such as a carboxyl group of these various copolymers, or a thermosetting synthetic resin such as a melamine resin and a urea resin. Examples of the water-soluble binder include starch derivatives such as phosphate esterified starch, etherified starch and phosphate esterified starch, cellulose derivatives such as methyl cellulose, carboxymethyl cellulose, and hydroxyethyl cellulose, polyvinyl alcohol such as polyvinyl alcohol or silanol-modified polyvinyl alcohol. Alcohol derivatives, casein, gelatin or modified products thereof, soy protein, pullulan, gum arabic, karaya gum, albumin and other natural polymer resins or derivatives thereof, vinyl polymers such as sodium polyacrylate, polyacrylamide, polyvinylpyrrolidone, alginic acid Examples include soda, polyethyleneimine, polypropylene glycol, polyethylene glycol, maleic anhydride or a copolymer thereof. But it is not limited to.

  These water-dispersible binders and / or water-soluble binders can be used alone or in admixture of two or more. In particular, since a latex binder which is a water-dispersible binder is excellent in coating layer strength when used in a coating layer, it is preferable that the coating layer in the present invention mainly contains a latex binder as a binder. Here, containing mainly a latex binder as a binder means containing 50 mass% or more of the total content of the binder in the coating layer, preferably containing 60 mass% or more.

  The total content of the binder in the coating layer is 5 parts by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the total pigment in the coating layer, preferably 10 from the viewpoint of the strength of the coating layer and the ink absorbability. It is not less than 30 parts by mass.

  In the present invention, the method for coating the coating layer on the base paper can be any commonly used coating method, and is not particularly limited. For example, various coating apparatuses such as a blade coater, a roll coater, an air knife coater, a film transfer coater, a bar coater, a rod blade coater, a short dwell coater, and a curtain coater can be used.

  The coated coated paper for printing can be used as it is, but the surface can be smoothed by a machine calendar, a soft nip calendar, a super calendar, a multi-stage calendar, a multi-nip calendar, etc., if necessary.

  However, if an excessive calendar process is performed for smoothing, the gaps in the coated paper for printing are crushed and, as a result, the ink absorbability in inkjet printing is deteriorated.

  In the coated paper for printing of the present invention, the coating layer can be provided on both sides of the base paper. Providing on both sides is preferable because printing can be performed on both sides depending on the printing machine. In the case of both sides, the coating layer on the side to be printed with an offset printer and / or an inkjet printer may contain heavy calcium carbonate and a calcium compound other than calcium carbonate.

  In the present invention, the coating layer is formed by coating on the base paper, and an intermediate containing a pigment and an adhesive between the coating layer and the base paper as necessary for adjustment of smoothness and ink absorbability. A layer may be provided. The pigment and adhesive used for the intermediate layer can be appropriately selected from pigments and adhesives that can be used for the coating layer.

The finally obtained coated paper for printing is processed into a large or small sheet size or roll shape according to the application, and becomes a product. During storage, it is preferable to apply moisture-proof packaging to avoid moisture absorption. The basis weight of the product is not particularly limited, degree 40 g / ^{m 2} or more 300 g / ^{m 2} or less.

  The coated paper for printing of the present invention can be used for both offset printing and inkjet printing, and a printed image having excellent image quality and durability can be obtained. The coated paper for printing of the present invention can be preferably used in an ink jet printer that employs a pigment ink, and a printed image having excellent image quality and durability can be obtained. The coated paper for printing of the present invention can be preferably used for a rotary inkjet printer in which the printing speed is 15 m / min or more, 60 m / min or more at a higher speed, and 120 m / min at a higher speed. A printed image having high image quality and durability can be obtained.

  The coated paper for printing of the present invention can be used not only for offset printing but also for gravure printing, wet and dry electrophotography, and other printing methods, and is not limited at all. Furthermore, it can also be used for commercially available inkjet printers in addition to rotary inkjet printers.

  As another aspect of the present invention, there is provided a method for improving the image quality and durability of a printed image printed by an ink jet printer, the step of obtaining the printing coated paper, and the coating of the printing coated paper Provided is a method including a step of forming a printed image on a layer by performing inkjet printing using a pigment ink at a printing speed of 50 m / min or more. The present invention also relates to a method for forming a printed image with less rubbing, smudge, and printing unevenness of a printed portion by inkjet printing, the step of obtaining the above-mentioned printing coated paper, and the coating layer of the printing coated paper Furthermore, the present invention provides a method including a step of forming a printed image by performing inkjet printing using a pigment ink at a printing speed of 50 m / min or more. Further, the present invention is a method for forming an excellent printed image, wherein an offset printing machine and / or an inkjet printing machine is provided on the coating layer of the printing coated paper, and the step of obtaining the above coated paper for printing. A method is provided that includes using to form a printed image.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples as long as the gist thereof is not exceeded. Further, “parts” and “%” shown in the examples indicate parts by weight and mass% of the dry solid content or substantial component unless otherwise specified. The coating amount also indicates the coating amount of the dry solid content.

(Preparation of base paper)
<Preparation of base paper 1>
To a pulp slurry consisting of 100 parts of LBKP having a freeness of 400 mlcsf, 12 parts of light calcium carbonate, 0.8 parts of amphoteric starch, 0.8 parts of sulfuric acid band, 1.0 part of an alkyl ketene dimer type sizing agent are added as fillers. Papermaking was carried out with a long paper machine, and 3.0 g / m ^{2 of} phosphate esterified starch was adhered on both sides with a size press machine, followed by treatment with a machine calendar to prepare a base paper 1 having a basis weight of 100 g / m ² . The ash content of this base paper was 10%.

<Preparation of base paper 2>
Base paper 2 was prepared in the same manner as base paper 1 except that 4 parts of light calcium carbonate and 8 parts of kaolin were used as fillers. The ash content of this base paper was 10%.

<Preparation of base paper 3>
A base paper 3 was prepared in the same manner as the base paper 1 except that 12 parts of kaolin was used as a filler. The ash content of this base paper was 10%.

<Preparation of coating solution for coating layer>
The coating solution for the coating layer was adjusted according to the following contents.
Pigment blending number is listed in Table 1 Binder blending number is listed in Table 1 Calcium compound blending number is listed in Table 1 Cationic agent (however, excluding calcium compound) Blending number is listed in Table 1 Were mixed and dispersed to prepare a solid concentration of 30%.

  The pigments, adhesives, calcium compounds and cationic agents (excluding calcium compounds) shown in abbreviations in Table 1 are as follows.

(Pigment)
A: Heavy calcium carbonate (SETACARB, manufactured by Shiraishi Calcium Co.)
B: Light calcium carbonate (TP123, manufactured by Okutama Kogyo Co., Ltd.)
C: Kaolin (UW90, manufactured by Engelhard)
D: Synthetic amorphous silica (P705, manufactured by Tosoh Silica)
(binder)
E: Polyvinyl alcohol (PVA105, manufactured by Kuraray Co., Ltd.)
F: Ethylene-vinyl acetate resin (Rikabond BEF9857, manufactured by Chuo Rika Kogyo Co., Ltd.)
(Calcium compound)
G: Calcium chloride H: Calcium nitrate (cationic agent)
I: Magnesium chloride J: Cationic resin (Papiogen P105, manufactured by Senka)

  About Examples 1-22 and Comparative Examples 1-8, it produced with the following procedures.

<Preparation of coated paper for printing>
The coating liquid was coated on the base papers 1 to 3 with an air knife coater and dried, and then calendered to produce a coated paper for printing. The base paper used is shown in Table 1.

The coating amount of the coating solution is shown in Table 1 as the coating amount per side. “Ca2 + amount” in Table 1 represents the calcium compound content, and is the calcium ion equivalent content of calcium compounds other than calcium carbonate in the coating layer on one side of the 1 m ² printing paper. “A / B” in Table 1 represents the calcium content mmol ratio, and the calcium amount A of calcium carbonate contained in 1 m ² of printing paper and the calcium amount B of calcium compounds other than calcium carbonate. Ion conversion mmol ratio (A / B).

(Evaluation of coated paper for printing)
The following methods were used to evaluate the offset printability, ink absorbability, ink fixability, and printing unevenness of the printing papers of Examples 1-22 and Comparative Examples 1-8. The results are shown in Table 1.

  Except for the evaluation of the offset printing suitability, an ink jet printer was used, and a Kodak printer Versamark VL2000 was used as the ink jet printer. Further, pigment ink was used as the ink. Printing was performed at a printing conveyance speed of 75 m per minute.

<Evaluation of suitability for offset printing>
With an offset form rotary press manufactured by Miyakoshi, printing speed: 150 m / min, ink used: T & K TOKA UV best cure ink and gold red, UV irradiation amount: 6000 m under the condition of 8 kW, and generation of blank piling after printing The situation and the state of the printed sample were judged by visual evaluation. If the evaluation is 3 to 5, there is no practical problem.
5: Extremely good.
4: Good.
3: Range in which there is no practical problem.
2: Defect.
1: Extremely bad.

<Evaluation of ink absorbency>
A solid pattern of 7 colors in total (double color (red, green, blue) with black, cyan, magenta, yellow, and other three colors except black ink on the coated paper for printing. Was printed by a method of recording in a 2 cm × 2 cm square with no gaps in a horizontal row. Each color solid portion and boundary portion of the printed portion was determined by visual evaluation. If the evaluation is 3 to 5, there is no practical problem.
5: There is no blur at the color boundary.
4: There is almost no bleeding at the boundary of the color.
3: Although the color boundary is blurred, the boundary can be clearly identified.
2: The color boundary is not clear, and the adjacent colors have moved slightly beyond the boundary.
1: The boundary of each color is not known, and bleeding to adjacent colors is large.

<Evaluation of ink fixability>
The printed surface of the printing coated paper discharged to the paper discharge unit of the printing machine at a predetermined conveyance speed was observed, and the degree of ink rubbing was determined by visual evaluation. If the evaluation is 3 to 5, there is no practical problem.
5: No ink rubbing trace is observed.
4: Almost no rubbing trace of ink is observed.
3: A slight trace of ink rubbing is observed.
2: There is an ink rubbing trace, and the printed matter appears to be partially stained.
1: The rubbing trace of the ink has generate | occur | produced in the whole printed part.

<Print unevenness in the printed part>
A solid pattern of 7 colors in total (double color (red, green, blue) with black, cyan, magenta, yellow, and other three colors except black ink on the coated paper for printing. Was printed by a method of recording in a 3 cm × 3 cm square in a horizontal row. The print density unevenness of each solid color portion of the printed portion was determined by visual evaluation. If the evaluation is 3 to 5, there is no practical problem.
5: Print density unevenness is not recognized.
4: Very slight print density unevenness is observed depending on the color.
3: Print density unevenness is slightly observed.
2: Print density unevenness is partially recognized.
1: Print density unevenness is observed throughout the printed portion.

From Table 1, in the coated paper for printing which provided one or more coating layers on at least one side of the base paper shown in Examples 1 to 22, the coating layer contains a calcium compound other than calcium carbonate, and calcium. The compound is contained in the coating layer on at least one side per 1 m ^{2 of the} printing paper for printing in the range of 3 mmol or more and 60 mmol or less in terms of calcium ion, and heavy calcium carbonate is used as the pigment in the coating layer in the coating layer. The coated paper for printing, which contains 50 parts by mass or more with respect to 100 parts by mass of the total pigment, and the base paper contains calcium carbonate, is excellent in offset printing suitability, ink absorbability, and ink fixing property, and further, printing unevenness in the printed part. It can be seen that is suppressed.

  On the other hand, from Table 1, the effects of the present invention cannot be obtained in Comparative Examples 1 to 8 that do not satisfy the conditions of the present invention.

Claims (3)

In a printing coated paper in which a coating layer mainly composed of a pigment and a binder is provided on at least one surface of the base paper, the coating layer contains a calcium compound other than calcium carbonate, and the calcium compound is coated for printing. 100 parts by mass of total pigment in the coating layer containing heavy calcium carbonate as a pigment in the coating layer, contained in the range of 3 mmol to 60 mmol in terms of calcium ion in the coating layer on at least one side per 1 m ^{2 of} paper A coated paper for printing, which is contained in an amount of 50 parts by mass or more based on the amount of calcium carbonate. The calcium ion-equivalent mmol ratio (A / B) of the calcium amount A of calcium carbonate and the calcium amount B of a calcium compound other than calcium carbonate contained in 1 m ² of printing coated paper is 1 or more and 50 or less. The coated paper for printing described.   The coated paper for printing according to claim 1, wherein the calcium compound other than calcium carbonate in the coating layer is calcium chloride.