JP2013046985A - Coated paper for both offset printing and inkjet printing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coated paper for both offset printing and inkjet printing, which has superior balance in offset printing aptitude and inkjet printing aptitude, and by which, after an image is printed by the offset printing, another image may be printed by inkjet printing without impairing clearness or without generating defects such as a wrinkle.SOLUTION: This coated paper for both offset printing and inkjet printing includes: a base paper; and a pigment coating layer laminated on the base paper and having the main components of a pigment and an adhesive. The base paper includes an internal-additive sizing agent and/or an external-additive sizing agent. The pigment coating layer includes a printing aptitude improving agent. Wet expansion is 0.01% or more and 0.5% or less. The dynamic liquid penetration is 85% or more and 98% or less.

Description

  The present invention relates to coated paper for both offset printing and inkjet printing.

  In various methods for printing an image on paper, offset printing is generally used when printing a large amount of images at high speed. Offset printing is widely used in commercial printing because it has excellent image clarity, is suitable for a large amount of printing, and provides a low-cost and high-quality printed matter. On the other hand, when printing variable information, inkjet printing is generally used. Inkjet printing is characterized by low running costs when printing in small quantities and easy handling of variable information. As such offset printing and inkjet printing combined paper, a coated paper having both offset printing suitability and ink jet printing suitability has been proposed (see JP 2004-230777 A).

  This offset printing and inkjet printing combined coated paper can be printed by selecting either offset printing or inkjet printing, or by performing inkjet printing on a non-image portion (white paper portion where printing is not performed) of offset printing. It is intended for use. For example, the advertisement information of the inserted flyer is offset printed, and the map of the nearest store is ink-jet printed on the marginal white paper portion, thereby changing the flyer information according to the customer's residence.

  However, in recent years, for example, in direct mail, advertisements, calendars, etc., images (fixed information) are uniformly printed on the coated paper by offset printing, and then individual images, characters, etc. are further printed on the coated paper for each customer. Printed materials in which the variable information is printed by inkjet printing are becoming popular. In such an application, the above-described offset printing and inkjet printing combined use paper are not suitable for both printing. In other words, no consideration is given to the case where the inkjet ink obtained by inkjet printing is deposited on the offset ink transferred by offset printing, and when two prints are superimposed in this manner, a clear image is obtained. There is a disadvantage that it cannot be obtained and wavy wrinkles are likely to occur.

JP 2004-230777 A

  The present invention has been made in view of these circumstances, and is excellent in offset printability and inkjet printability in a well-balanced manner. After printing an image by offset printing, it is separated by inkjet printing without causing defects such as wrinkles. It is an object of the present invention to provide a coated paper for both offset printing and inkjet printing, which can be printed in an overlapping manner without impairing the sharpness of the image.

  As a result of earnestly examining the cause of the above-described problems when inkjet printing is performed on an image printed by offset printing, the present inventor has obtained the following knowledge and led to the present invention.

  In other words, when inkjet ink adheres across the offset ink printed by offset printing and the blank paper portion where this offset ink is not printed, the inkjet ink adhered to the offset ink that is oleophilic is applied to the pigment coating layer. While not penetrating, the pigment coating layer of the blank paper portion absorbs the ink-jet ink. For this reason, the ink-jet ink attached on the offset ink flows to the blank paper portion, and the ink-jet ink is removed from the offset ink, so that the image is blurred and a clear image cannot be obtained. Furthermore, when the inkjet ink passes through the pigment coating layer and penetrates into the base paper, the pulp fiber swells and wrinkles are generated in the white paper portion. In particular, in offset printing, since the color density is adjusted with a halftone (halftone dot), the offset ink and the blank paper portion are alternately present in the halftone portion (halftone dot portion) by the offset printing. For this reason, when ink jet printing is performed on the halftone portion, image blurring and defects such as wrinkles are particularly noticeable, and the quality of the printed matter is deteriorated.

Therefore, the invention made to solve the above problems is
The base paper,
A coated paper having a pigment coating layer comprising a pigment and an adhesive as a main component, laminated on the base paper,
The base paper contains an internal sizing agent and / or an external sizing agent;
A printability improver is contained in the pigment coating layer,
The wet elongation is 0.01% or more and 0.5% or less,
It is a coated paper for both offset printing and inkjet printing characterized by having a dynamic liquid permeability of 85% or more and 98% or less.

  This wet elongation means that a measurement sample obtained by cutting a coated paper in a papermaking flow direction of 60 mm and a width direction of 300 mm is dipped in water and subjected to WET STRETCH DYNAMICS ANALYZER (WSD [MUTEC] When a 2N tensile load was applied in the paper flow direction, the difference between the paper flow direction length of the measurement sample 5 seconds after the start of tension and the length in the paper flow direction before the test was measured. It is divided by the length in the papermaking flow direction.

  The dynamic liquid permeability means that a measurement sample obtained by cutting a coated paper in a papermaking flow direction of 50 mm and a width direction of 75 mm is subjected to SURFACE AND SIZING TESTER (EST12 [EST12 [ It is a measured value of ultrasonic transmission intensity 1 second after the start of immersion when immersed in water using MUTEC Co.].

  According to the offset printing and ink jet printing combined paper, the base paper contains an internal sizing agent and / or an external sizing agent, and the pigment coating layer contains a printability improving agent. While reducing the water absorption, the pigment coating layer can have an appropriate water absorption and can impart wettability. Therefore, not only does the pigment coating layer have ink jet printing suitability, but in the offset printing and ink jet printing combined paper, dampening water adhering to the non-printing part during offset printing is absorbed by the pigment coating layer. However, since it is not absorbed by the base paper, it is possible to prevent generation of wrinkles caused by a difference in shrinkage rate in the drying stage between the printed portion and the non-printed portion. In addition, since the liquid absorption amount of the inkjet ink to the pigment coating layer can be adjusted moderately, the inkjet ink can be adjusted so as not to reach the base paper. In addition, the improvement in wetting resistance delays the initial absorption speed of the inkjet ink and allows time for the inkjet ink to dry on the offset ink, so that the inkjet attached to the offset printed image by the inkjet It is possible to suppress the ink from flowing to the white paper portion. As a result, it is possible to prevent waviness of the coated paper and to clearly perform ink jet printing on the offset printed image, thereby producing a high-quality printed matter.

  The wet elongation of the coated paper for offset printing and inkjet printing is preferably 0.01% or more and 0.5% or less. By setting the wet elongation in the above range, the elongation due to water absorption becomes small. Therefore, even when the ink-jet ink is absorbed by the base paper, it is possible to prevent undulation and produce a high-quality printed matter. it can.

  The dynamic liquid permeability of the offset printing and ink jet printing combined paper is preferably 85% or more and 98% or less. By setting the dynamic liquid permeability in the above range as described above, the absorbability (absorption amount and initial absorption speed) of the dampening solution and the inkjet ink can be adjusted as appropriate, so that the coated paper is prevented from wavy and offset. Inkjet printing can be performed clearly on the printed image, and a high-quality printed matter can be produced.

  The content ratio of the printability improver to the pigment is preferably 0.1% by mass or more and 1.0% by mass or less. Thus, the pigment coating layer can be made porous by setting the content ratio of the printability improver to the pigment within the above range, and the inkjet printability of the offset printing and inkjet printing combined use paper can be improved. . In addition, the amount of dampening water adhering to the non-printed area during offset printing is adjusted moderately, and the initial absorption speed of the ink-jet ink is delayed by improving wet resistance, so that dampening water penetrates into the base paper. This can be suppressed. As a result, the offset printing and inkjet printing combined coated paper is easy to prevent undulation in the non-printing portion of the offset printing, and the inkjet printing is likely to be clear, and it is easy to produce a high-quality printed matter.

  The moisture content of the offset printing and inkjet printing combined paper is preferably 3% by mass or more and 6% by mass or less. Thus, by setting the moisture content within the above range, the shrinkage rate at the stage of changing from the wet state at the time of printing to the dry state can be reduced, which is caused by shrinkage of the coated paper for both offset printing and inkjet printing. Occurrence of elbows can be prevented. As a result, it is possible to produce a high-quality printed material by using the offset printing and inkjet printing combined paper.

  The offset printing and ink jet printing combined coated paper is suitably used for printing an image by offset printing and further printing another image on the image by inkjet printing. By using the offset printing and ink jet printing combined coated paper, a clear image can be obtained without causing wrinkles even when ink jet printing is performed on top of offset printing, so that high quality printed matter is manufactured. be able to.

  The “printability improver” is a coating applied to improve the water absorption and wetting resistance of the pigment coating layer by reacting with a pigment or the like to form a crosslinked structure or ionically bond. It means an additive added to paper.

  As described above, the offset printing and inkjet printing combined paper of the present invention is excellent in offset printing suitability and inkjet printing suitability, and generates defects such as wrinkles after printing an image by offset printing. In addition, another image can be superimposed and printed without loss of sharpness by inkjet printing.

  Hereinafter, embodiments of the present invention will be described in detail.

  The offset printing and inkjet printing coated paper of the present invention has a base paper and a pigment coating layer laminated on the base paper, and the base paper contains an internal sizing agent and / or an external sizing agent. The pigment coating layer contains a printability improver, has a wet elongation of 0.01% to 0.5% and a dynamic liquid permeability of 85% to 98%. It is.

  In the offset printing and inkjet printing combined use paper, since the base paper contains an internal additive sizing agent and / or an external additive sizing agent, the water absorption of the base paper is low. Moreover, since the pigment coating layer contains a printability improving agent, the pigment coating layer has appropriate water absorption and wet resistance. For this reason, the dampening water adhering to the non-printing part when the offset printing is applied to the offset printing and inkjet printing combined paper is absorbed by the pigment coating layer but does not penetrate into the base paper and is dried. It is possible to prevent the occurrence of wrinkles at the stage. In addition, it is possible to suppress the ink-jet ink attached during ink-jet printing from being absorbed by the base paper. As a result, it is possible to prevent the coated paper from wavy and to prevent printing defects due to the flow of the ink-jet ink attached to the offset ink transferred by the offset printing to the white paper portion, and a clear image. Can be obtained.

  Further, the wet elongation of the coated paper for offset printing and inkjet printing is 0.01% or more and 0.5% or less, preferably 0.1% or more and 0.4% or less. When the wet elongation is within the above range, even when dampening water or inkjet ink is absorbed by the base paper, the stretch of the coated paper is small and undulation can be prevented. If the wet elongation of the offset printing and inkjet printing combined coated paper is less than the above range, an excessive amount of a sizing agent or paper strength improver must be added in order to reduce the liquid absorbency of the base paper, There is a possibility that the operability is deteriorated and manufacturing becomes difficult. On the other hand, when the wet elongation exceeds the above range, when dampening water or inkjet ink is absorbed by the base paper, the pulp fibers may swell and the coated paper may become wavy. In addition, this wet elongation can be adjusted with content, such as a below-mentioned sizing agent and a printability improvement agent.

  Further, the coated paper for both offset printing and inkjet printing has a dynamic liquid permeability of 85% or more and 98% or less, and preferably 90% or more and 98% or less. When the dynamic liquid permeability is in the above range, the absorbability (absorption amount and initial absorption speed) of dampening water and inkjet ink can be adjusted as appropriate, preventing the wavyness of the coated paper and offset printing. In addition, the ink jet printing can be performed clearly on the printed image, and a high-quality printed matter can be manufactured. If the dynamic liquid permeability is less than the above range, the water absorption becomes too high, and it becomes easy to absorb dampening water in offset printing, generating wrinkles and blisters, and worsening the printability of inkjet printing. . Conversely, if the dynamic liquid permeability exceeds the above range, dampening water is difficult to absorb in offset printing, plate stains occur, offset printing suitability deteriorates, and ink jet ink becomes difficult to absorb. The sharpness of the image is reduced.

  The dynamic liquid permeability is for evaluating paper characteristics such as surface size, porosity, and wettability from a time curve of ultrasonic transmission intensity. The measurement is performed as follows. The coated paper is immersed in a measurement cell filled with water, and an ultrasonic signal is immediately emitted in the thickness direction, and a change in the signal transmitted through the coated paper is measured. Ultrasound permeability changes as follows. Immediately after the measurement, as the paper surface gets wet with water, the reflection of ultrasonic waves at the interface between the coated paper and water decreases, and the received signal increases. Thereafter, as water penetrates into the coated paper, ultrasonic waves are scattered by bubbles left locally in the coated paper, and the received signal decreases. When water completely penetrates the coated paper, the absorption of ultrasonic waves decreases and the received signal increases. This dynamic liquid permeability can be adjusted by the content of a sizing agent, a printability improver and the like.

  Hereinafter, essential and suitable specific components (raw pulp, sizing agent, pigment, adhesive, etc.) constituting the base paper and pigment coating layer of the offset printing and inkjet printing combined use paper, and the offset printing and inkjet printing. A method for producing the combined coated paper will be described.

<Raw material pulp>
The raw material pulp used for the base paper of the offset printing and inkjet printing combined use paper is not particularly limited. For example, hardwood bleached kraft pulp (LBKP), softwood bleached kraft pulp (NBKP), hardwood unbleached Chemical pulp such as kraft pulp (LUKP), softwood unbleached kraft pulp (NUKP), hardwood semi-bleached kraft pulp (LSBKP), softwood half-bleached kraft pulp (NSBKP), hardwood sulfite pulp, softwood sulfite pulp; Stone Grand Pulp (SGP) ), Pressurized Stone Grand Pulp (PGW), Refiner Grand Pulp (RGP), Thermo Grand Pulp (TGP), Chemi Grand Pulp (CGP), Ground Pulp (GP), Thermomechanical Pulp (TMP), etc .; Tea Waste paper, craft seal Waste paper, magazine waste paper, newspaper waste paper, flyer waste paper, office waste paper, cardboard waste paper, Kami white waste paper, Kent waste paper, imitation waste paper, waste paper waste paper, etc. -Bleached waste paper pulp: Various well-known pulps such as pulps chemically or mechanically produced from non-wood fibers such as kenaf, hemp, and straw can be used.

  Among these raw material pulps, hardwood bleached kraft pulp (LBKP), softwood bleached kraft pulp (NBKP), hardwood unbleached kraft pulp (LUKP) to achieve various quality characteristics as a base paper in a balanced and efficient manner Of these, non-bleached kraft pulp (NUKP) or waste paper pulp made from Koji White Waste Paper, Kent Waste Paper, Tea Waste Paper, Kraft Envelope Waste Paper is preferred. In addition, when selecting raw material pulp, it is preferable to mix | blend as much waste paper pulp as possible from the reduction of the energy unit and the load given to an environment.

<Internal sizing agent>
The base paper for the offset printing and inkjet printing combined paper preferably contains an internal sizing agent in order to improve the size. The internal sizing agent is not particularly limited, and known rosin sizing agents, alkenyl succinic anhydride, alkyl ketene dimers, neutral rosin sizing agents, styrene acrylic sizing agents, various emulsion sizing agents, and the like. Various internal sizing agents can be used. Among these, an alkyl ketene dimer having a high effect of preventing the waviness of the coated paper during printing is particularly preferable.

  The lower limit of the content of the internal sizing agent relative to the base paper is preferably 0.01% by mass, more preferably 0.02% by mass, and particularly preferably 0.04% by mass. On the other hand, the upper limit of the amount of the internally added sizing agent is preferably 1.0% by mass, more preferably 0.5% by mass, and particularly preferably 0.3% by mass. If the addition amount of the internal sizing agent is less than the above lower limit, the base paper can easily absorb the dampening water and the inkjet ink, and there is a possibility that undulation, wrinkles, and blisters may occur during printing. On the contrary, when the amount of the internal sizing agent added exceeds the above upper limit, in the paper making process, the oil and fat component in the sizing agent adheres to the dryer surface and coats, thereby reducing the glossiness and smoothness of the base paper surface. There is a risk. Moreover, it may cause scale generation in the paper making process, which may cause foreign matter defects.

<External sizing agent>
An external additive sizing agent is preferably applied to the surface of the base paper of the offset printing and inkjet printing combined use paper in order to improve the size. The external sizing agent is not particularly limited. For example, polyacrylamide, polyvinyl alcohol, cellulose derivative, acrylic ester, olefin polymer, styrene polymer, acrylate polymer, styrene-maleic acid. Copolymer, vinyl acetate-maleic acid copolymer, alkyl ketene dimer, styrene-acrylic copolymer, composite material of anionic copolymer and cationic copolymer, olefin-maleic acid copolymer, starch, etc. Various known external additive sizing agents can be used. Among these, an olefin polymer having a high effect of preventing the waviness of the coated paper during printing is particularly preferable.

  The lower limit of the coating amount of the external additive sizing agent is preferably 0.10% by mass, more preferably 0.20% by mass with respect to the absolutely dry pulp. On the other hand, the upper limit of the coating amount of the external sizing agent is preferably 1.0% by mass, and more preferably 0.50% by mass. If the coating amount of the external sizing agent is less than the above lower limit, the base paper tends to absorb dampening water or inkjet ink, and there is a possibility that undulations, wrinkles or blisters may occur during printing. On the contrary, when the coating amount of the external additive sizing agent exceeds the above upper limit, the adhesiveness of the pigment coating layer is lowered, and the pigment coating layer is not uniformly formed, and the sharpness of the image may be lowered.

<Filler>
In the base paper of the offset printing and inkjet printing combined paper, a filler conventionally used for papermaking can be added to the raw material pulp as an internal additive. Examples of the filler include inorganic fillers such as light calcium carbonate, talc, titanium dioxide, clay, calcined clay, synthetic zeolite, and silica, polystyrene latex, urea formalin resin, and the like.

  Although the content rate of the said filler with respect to a base paper is not specifically limited, 2 mass% or more and 30 mass% or less are preferable, and 5 mass% or more and 20 mass% or less are more preferable. When the content of the filler is less than the lower limit, fuzzing or roughening may occur, or the water absorption may increase and breakage may occur during printing, or defects such as wrinkles may occur. Conversely, if the filler content exceeds the above upper limit, the binding between pulp fibers may be hindered and the stiffness, tensile strength, tear strength, etc. may be reduced, and when dampening water during offset printing is absorbed. May break. The filler content is a value calculated from the ash content measured according to JIS-P8251 “Paper, paperboard and pulp-ash content test method—525 ° C. combustion method”.

  In addition, the above-mentioned raw material pulp has various anionic, nonionic, cationic or amphoteric yield improvers conventionally used for papermaking, other than the sizing agent and filler, as long as the effects of the present invention are not impaired. Internal additives for papermaking, such as drainage improvers, paper strength enhancers, dyes, fluorescent brighteners, pH adjusters, antifoaming agents, pitch control agents, slime control agents, etc. Can be added as appropriate.

<Pigment coating layer>
In the coated paper for both offset printing and inkjet printing, a pigment coating layer is laminated by applying a coating liquid containing a pigment and an adhesive on one or both sides of the base paper.

<Pigment>
As the pigment used in the pigment coating layer, inorganic pigments and organic pigments conventionally used for papermaking can be used. Specifically, for example, clay (kaolin, wax), calcium carbonate, talc, satin white, calcium sulfite, gypsum, barium sulfate, white carbon, calcined kaolin, structured kaolin, diatomaceous earth, magnesium carbonate, titanium dioxide, water Aluminum oxide, calcium hydroxide, magnesium hydroxide, zinc hydroxide, zinc oxide, magnesium oxide, bentonite, sericite, polystyrene resin fine particles, urea formalin resin fine particles, fine hollow particles, porous fine particles, silica composite inorganic particles, etc. 1 type or 2 types or more can be selected suitably from these, and can be mix | blended. Among these, it is particularly preferable to include clay and silica composite inorganic particles in the pigment coating layer.

  As the clay, it is preferable to use a plate-like clay that can easily cover the base paper and improve the offset printing suitability even at a low coating amount. On the other hand, when platy clay is added to the pigment coating layer, pores on the surface of the pigment coating layer are reduced and water absorption is reduced, but a printability improver described later should be added to the pigment coating layer. As a result, the pigment coating layer is made porous, ensuring printability for inkjet printing, and achieving both surface strength and inkjet printability.

  As such a plate-like clay, one having a maximum value in a particle size distribution range of 0.2 μm or more and 7.0 μm or less is preferable because of its high coverage and high surface strength. When the particle diameter is less than 0.2 μm, the covering property is lowered, and the particles are liable to sink into the base paper and the sharpness of the image is lowered. On the other hand, when the particle diameter exceeds 7.0 μm, the surface roughness of the pigment coating layer increases and the sharpness of the image decreases. Furthermore, the aspect ratio of the plate-like clay (ratio of the plate diameter to the particle thickness) is preferably 5 or more from the viewpoint of coverage. In addition, said particle diameter refers to the particle diameter obtained by photographing the pigment particle of the pigment coating layer surface with an electron microscope, and measuring the particle diameter.

  The silica composite inorganic particles are not particularly limited as long as they are a composite of silica and inorganic particles other than silica. For example, silica-calcium carbonate composite particles, silica-titanium dioxide composite particles, silica and Silica composite regenerated particles combined with regenerated particles can be used. As the silica composite regenerated particles, those obtained by combining silica with regenerated particles mainly composed of calcium, silica, alumina and the like obtained by dehydrating, drying, firing, and pulverizing paper sludge and deinking floss are used. be able to. When this silica composite inorganic particle is added as a pigment to the pigment coating layer, the surface strength of the coated paper is reduced, but by using it together with the clay, the surface strength is maintained and printing suitability for offset printing is ensured. be able to.

  The average particle size of the silica composite inorganic particles is preferably 1.7 μm to 35 μm, more preferably 3 μm to 10 μm, and particularly preferably 5 μm to 8 μm. If the average particle size of the silica composite inorganic particles is less than the lower limit, a sufficient opacity improving effect may not be obtained. Conversely, if the average particle size of the silica composite inorganic particles exceeds the above upper limit, the tensile strength, tear strength, etc. may be reduced.

<Adhesive>
As an adhesive used for the pigment coating layer, an adhesive conventionally used for papermaking can be used. Specifically, for example, proteins (casein, soybean protein, etc.), latexes (conjugated diene latexes such as methyl methacrylate-butadiene copolymer latex, styrene-methyl methacrylate-butadiene copolymer latex, acrylic acid esters, and the like) / Acrylic latex such as polymer latex or copolymer latex of methacrylic acid ester, vinyl latex such as ethylene-vinyl acetate polymer latex, and these various copolymer latexes containing functional groups such as carboxyl groups Body-modified alkali partially soluble or insoluble latex, etc.), synthetic resin adhesives (polyvinyl alcohol, olefin-maleic anhydride resin, melamine resin, urea resin, urethane resin, etc.), starches (oxidized starch, Positive starch, esterified starch , Dextrin), cellulose derivatives (carboxymethyl cellulose, hydroxyethyl cellulose), etc. can be mentioned, can be used by selecting one or more from among these as appropriate.

<Printability improver>
In the pigment coating layer of the offset printing and inkjet printing combined paper, the pigment coating layer is made porous to improve the ink-jet ink absorption amount, and also improve the wetting resistance and delay the initial ink absorption rate of the ink-jet ink. In addition, a printability improver is added. Specific examples of the printability improver include, for example, melamine resins, melamine-formaldehyde resins, urea resins, urea-formaldehyde resins, polyamine resins, polyamide polyuric acid resins, polyamide polyurea-formaldehydes. Resin, polyamide-formaldehyde resin, polyamide-epoxy resin, polyamide epichlorohydrin resin, gliogizar resin, zirconium carbonate, glycerin diglycidyl ether, polyglycidyl ether, ketone aldehyde resin, dialdehyde starch, etc. it can. Among these, a polyamine-based resin that can easily agglomerate the pigment coating layer, improve the ink-jet ink absorption amount and wet resistance, and can improve the printability of the offset printing and ink-jet printing combined paper is particularly preferable. . However, the content of the printability improver in the pigment coating layer is preferably in the range described below. The component of the printability improver used in the present invention is used as a water-proofing agent, and when the content is increased, water resistance is developed and the absorbability of the ink-jet ink is likely to deteriorate and bleeding occurs. Ink jet printing suitability may be reduced.

  By adding this printing suitability improver to the pigment coating layer, the pigment coating layer is softly aggregated to improve ink jet printing suitability, but the surface strength tends to be lowered. For this reason, it is preferable to use the above-mentioned flat clay and adhesive as the pigment because it is easy to minimize a decrease in surface strength. In addition, when clay is contained as a pigment, it is difficult to obtain ink jet printing suitability because it is flat and has poor ink jet ink absorbability. However, by including a print suitability improver as in the present invention, appropriate ink jet ink absorbability is obtained. Can be obtained. That is, by combining the printability improver and the flat clay and adding them to the pigment coating layer, offset printability and inkjet printability are simultaneously imparted to the coated paper while maintaining the surface strength of the coated paper. be able to. In particular, when a polyamine-based resin is used as a printability improver and a flat clay is used as a pigment, a coated paper having particularly excellent surface strength, offset printability, and inkjet printability can be obtained.

  Moreover, since the space | gap of a pigment coating layer becomes large by addition of the said printability improvement agent, generation | occurrence | production of a blister can be prevented. Furthermore, moisture absorption / release of the coated paper is facilitated, and the seasoning period (a period until the offset ink is sufficiently fixed and can withstand inkjet printing) can be shortened. Therefore, the offset printing and inkjet printing combined use paper can achieve a short delivery time.

  As a minimum of the content rate of the above-mentioned printability improvement agent to 100 parts by mass of the pigment contained in the pigment coating layer, 0.1 part by mass is preferable, and 0.2 part by mass is more preferable. On the other hand, as an upper limit of the content rate of a printability improvement agent, 1.0 mass part is preferable and 0.5 mass part is more preferable. When the content of the printability improver is less than the above lower limit, sufficient ink-jet ink absorbability cannot be imparted to the pigment coating layer, and not only there may be bleeding of the ink-jet ink, but also moistening. There is a possibility that the water absorbability is lowered and the plate is smudged, and the offset printability is lowered. On the contrary, if the content of the printability improver exceeds the above upper limit, the viscosity of the coating agent forming the pigment coating layer increases, and the image may not be uniformly applied and the sharpness of the image may be reduced, or aggregation may occur. May occur and the coating surface may deteriorate. Moreover, there exists a possibility of contaminating the inside of a coating process.

  Moreover, as a ratio of the coating amount per one side with respect to a base paper, 5 to 60 mass% is preferable in conversion of solid content, and 10 to 40 mass% is further more preferable. If the ratio of the coating amount of the pigment coating layer is less than the lower limit, the printability of the offset printing and ink-jet printing combined paper may be lowered. On the contrary, when the ratio of the coating amount of the pigment coating layer exceeds the above upper limit, the opacity, stiffness, tensile strength, tear strength and the like of the coated paper for offset printing and inkjet printing may be lowered.

<Moisture content>
The moisture content of the offset printing and inkjet printing combined coated paper is preferably 3% by mass or more and 6% by mass or less, and more preferably 3% by mass or more and 4.5% by mass or less. If the moisture content of the offset printing and ink jet printing combined coated paper is less than the above range, it may be overdried and sufficient smoothness may not be obtained. Conversely, if the moisture content of the offset printing and inkjet printing combined paper exceeds the above range, blisters are likely to occur during drying after offset printing, and wrinkles are generated due to shrinkage of the coated paper due to moisture release. There is a risk. The moisture content mentioned here is JIS P 8127: 1998 “Paper and paperboard—moisture test method” within 10 minutes after packing the coated paper with moisture-proof paper and leaving it at room temperature for 1 week or longer. It means the moisture content measured according to “Method with a dryer”.

<Method for producing coated paper for both offset printing and inkjet printing>
The offset printing and inkjet printing combined coated paper can be produced by a papermaking method used for ordinary papermaking. The papermaking method is not particularly limited, and a papermaking process having a known wire part, press part, dryer part, coater part, and calendar part can be used.

  As the former used in the wire part, for example, a long net former, a combination of a long net former and an on-top former, a twin wire former or the like can be used. Among these, a gap former is particularly preferable in which the paper material ejected from the head box is sandwiched between two wires and dehydrated from both sides. By using this gap former, it is possible to prevent the front and back of the wet paper from being generated.

  Examples of the press used in the press part include a straight-through type, an invar type, and a reverse type, and one or a combination of two or more of these can be used. Among these, a straight-through type that does not have an open draw portion that is easy to hold paper and does not easily break is particularly preferable. Moreover, as a dehydration system used for the said press part, a suction roll system, a grooved press system, a shoe press system etc. can be used, for example. Among these, a shoe press system that can improve dehydration and smoothness is particularly preferable.

  As the dryer used in the dryer part, for example, a single deck dryer, a double deck dryer, or the like can be used. Among these, a single deck dryer that does not have a paper draw and does not have an open draw portion with high drying efficiency is particularly preferable.

  In the above coater part, examples of the method of applying the surface sizing agent to the base paper include a method using a film transfer type roll coater, a bill blade coater, a short dwell coater, an air knife coater, a blade coater, a spray coater and the like. be able to.

  Among these, it is preferable to use a film transfer type roll coater capable of uniform coating. Examples of the film transfer type roll coater include a 2-roll size press coater, a gate roll coater, a blade metering size press coater, and a rod metering size press coater.

  As the calendar used for the calendar part, for example, a machine calendar, a soft calendar, a multi-nip calendar, or the like can be used. Among these, a multi-nip calender that can adjust the pressure for each nip is particularly preferable. The calendar is preferably an on-machine type integrated with a paper machine and a coating machine. Since the on-machine type calendar can be flattened in a state where the paper surface temperature after coating is high, it is easy to improve smoothness. Therefore, it is possible to improve the white paper glossiness and the print glossiness while minimizing the decrease in paper thickness.

  The offset printing and inkjet printing combined coated paper is suitably used as a printing paper on which an image is printed by offset printing, and another image is printed on the image by inkjet printing. By using the offset printing and ink jet printing combined coated paper, a clear image can be obtained without causing wrinkles even when ink jet printing is performed on top of offset printing, so that high quality printed matter is manufactured. be able to.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples.

[Example 1]
As the raw material pulp, a mixture of NBKP at 20% by mass and LBKP at 80% by mass was used. To this raw pulp slurry, 0.05 mass% of an alkyl ketene dimer (AKD, “FK34 Kai” manufactured by Toho Chemical Industry Co., Ltd.) was added as an internal sizing agent. The freeness of NBKP was adjusted to 500 ml, and the freeness of LBKP was adjusted to 400 ml.

Using this raw pulp slurry, through a wire part using a gap former, a press part using a straight-through press without an open draw, and a dryer part using a single deck dryer, the basis weight is 50 g / m. ^Two base papers were produced.

  Next, an olefin-based polymer (“SS2550” manufactured by Seiko PMC Co., Ltd.) as an external sizing agent is applied to both sides of the base paper, using a film transfer type roll coater on both sides of the base paper. The coating was applied in an amount of 0.3% by mass in terms of solid content.

  After application of the external sizing agent, HC clay (“HYDRASPERSE” manufactured by HUBER) and aggregated calcium carbonate (“Hydro Curve 90” manufactured by Bihoku Powder Chemical Co., Ltd.) are used as pigments, respectively, 100 parts by mass of the entire pigment. 50 parts by mass with respect to 100 parts by mass of the pigment, 7 parts by mass of styrene-butadiene latex (“XY4” manufactured by Nippon A & L Co., Ltd.) as an adhesive, and starch (“Coating” manufactured by Sanki Co., Ltd.). Master K96F ")" is mixed with 5 parts by mass, and a coating solution is prepared by adding 0.3% by mass of solid content to the pigment of polyamine resin ("RA6634" manufactured by Seiko PMC Co., Ltd.) as a printability improver. did. Using a blade coater on both sides of the base paper, this coating solution was applied to the base paper so that the total of both sides was 20% by mass in terms of solid content, thereby forming a pigment coating layer.

  After application of the coating solution, a flattening process was performed using a multi-nip calender to obtain coated paper for both offset printing and inkjet printing of Example 1.

  As a result of measuring the wet elongation and dynamic liquid permeability of the coated paper of Example 1 obtained through the above papermaking process using the above-mentioned WSD and EST, the wet elongation was 0.1% and the dynamic liquid permeability was Was 98%. Moreover, the moisture content measured based on JIS-P8127 was 4%.

[Examples 2 to 24]
The types and contents of raw material pulp, pigment, and adhesive were the same as in Example 1. For the internally added sizing agent, Example 2 uses a rosin system (“E-3600” manufactured by Toho Chemical Industry Co., Ltd.), and Example 3 uses a styrene-acrylic system (“NS-555” manufactured by Toho Chemical Industry Co., Ltd.). In the other examples, the addition amount shown in Table 1 was added to the raw pulp slurry using the same internal sizing agent as in Example 1 above. As for the external sizing agent, Example 8 uses a styrene polymer (“SS2700” manufactured by Seiko PMC Co., Ltd.), and Example 9 uses an acrylate polymer (“SE2066” manufactured by Seiko PMC Co., Ltd.). In the other examples, the same external additive sizing agent as in Example 1 was used, and the base paper was coated in the same manner as in Example 1. Further, regarding the printability improver, Example 14 uses a polyamide polyuric acid system (“Smiles Resin 633” manufactured by Taoka Chemical Co., Ltd.), and Example 15 uses a zirconium carbonate system (“Cartabbond MZI manufactured by Clariant Japan Co., Ltd.). In other examples, the same printability improver as in Example 1 was used and added to the coating solution. The amount of sizing agent and printability improver added in each example, and measured wet elongation, dynamic liquid permeability, and moisture content are shown in Table 1 below.

[Comparative Examples 1 and 2]
The types and contents of raw material pulp, pigment, and adhesive were the same as in Examples 1-24. Comparative Example 1 was the same as Example 1 except that the internal additive sizing agent was not contained in the raw pulp slurry and the external additive sizing agent was not applied to the base paper. Comparative Example 2 was the same as Example 1 except that no printability improver was added to the coating solution.

[quality evaluation]
About each coated paper obtained in Examples 1-24 and Comparative Examples 1 and 2, each following quality evaluation was performed. The quality evaluation is shown in Table 1 below.

(1) Corrugation After an image by offset printing was printed on a coated paper, an image by ink jet printing was superimposed and printed, and the degree of corrugation (generation of wrinkles) of the coated paper was evaluated as follows.
(Evaluation criteria)
A: No wrinkle is generated on the surface of the coated paper.
○: Although it cannot be visually confirmed on the surface of the coated paper, a fine wrinkle can be confirmed by enlarging with a magnifying glass.
Δ: There is a small wrinkle that can be visually confirmed on the surface of the coated paper.
X: The surface of the coated paper has large wrinkles that can be visually confirmed, the entire coated paper is wavy, and cannot be used in practice.

(2) Hijiwa An image by offset printing was printed on the coated paper, and the degree of occurrence of wrinkles on the coated paper was visually evaluated according to the following criteria.
(Evaluation criteria)
A: No wrinkles are generated on the surface of the coated paper.
○: Some wrinkles are generated on the surface of the coated paper, and the appearance is slightly inferior.
Δ: Some wrinkles are generated on the surface of the coated paper, and the appearance is somewhat inferior.
X: A wrinkle is generated on the surface of the coated paper, the appearance is inferior, and practical use is impossible.

(3) Blister An image by offset printing was printed on the coated paper, and the degree of blistering of the coated paper was visually evaluated according to the following criteria.
(Evaluation criteria)
A: No blister is generated on the surface of the coated paper.
○: Some blisters are generated on the surface of the coated paper, and the appearance is slightly inferior.
Δ: Some blisters are generated on the surface of the coated paper, and the appearance is somewhat inferior.
X: Blister is generated on the surface of the coated paper, the appearance is inferior, and practical use is impossible.

(4) Image sharpness An image by offset printing was printed on a coated paper, and an image by ink jet printing was printed on top of the coated paper and evaluated as follows.
(Evaluation criteria)
(Double-circle): There is no unevenness in printing and it is clear printing.
○: Overprinted portions are slightly blurred and image sharpness is slightly inferior.
(Triangle | delta): The overlapping part of printing is blurred and image clarity is inferior.
X: The overlapping part of printing is considerably blurred and the image sharpness is remarkably inferior.

(5) Foreign object defect The degree of contamination of coated paper was visually evaluated according to the following criteria.
(Evaluation criteria)
A: There is no foreign matter on the surface of the coated paper.
○: Foreign matter is slightly mixed on the surface of the coated paper, and the appearance is slightly inferior.
Δ: Some foreign matter is mixed on the surface of the coated paper, and the appearance is somewhat inferior.
X: Foreign matter is mixed on the surface of the coated paper, the appearance is inferior, and practical use is impossible.

  As shown from the results in Table 1, the coated papers of Examples 1 to 24 can prevent the occurrence of undulations, wrinkles, and blisters, and the image sharpness and the degree of foreign matter defects are also in the actual use range. . On the other hand, in Comparative Example 1 in which no internal sizing agent was added and no external sizing agent was applied, waviness, wrinkles and blisters were remarkably generated, and no printability improver was added. In Comparative Example 2, creases and blisters are remarkably generated, and the image sharpness is remarkably inferior.

  As described above, the offset printing and inkjet printing combined coated paper of the present invention is excellent in balance in offset printing suitability and ink jet printing suitability, and without generating defects such as wrinkles after printing an image by offset printing. Another image can be printed by inkjet printing without losing the sharpness.

Claims (4)

The base paper,
A coated paper having a pigment coating layer comprising a pigment and an adhesive as a main component, laminated on the base paper,
The base paper contains an internal sizing agent and / or an external sizing agent;
A printability improver is contained in the pigment coating layer,
The wet elongation is 0.01% or more and 0.5% or less,
A coated paper for both offset printing and inkjet printing, wherein the dynamic liquid permeability is 85% or more and 98% or less.   2. The offset printing and inkjet printing combined paper according to claim 1, wherein the content ratio of the printability improving agent to the pigment is 0.1% by mass or more and 1.0% by mass or less.   The offset printing and ink jet printing combined paper according to claim 1 or 2, wherein the moisture content is 3% by mass or more and 6% by mass or less.   The offset printing and the inkjet printing combined coating according to claim 1, 2 or 3, which is used for printing an image by offset printing and further printing another image on the image by inkjet printing. paper.