JP7142153B2 - Printing paper and printed matter - Google Patents

Description

The present invention relates to printing paper and printed matter.

Conventionally, not only pulp paper but also synthetic paper using a resin film has been used as printing paper. The outermost surface of synthetic paper is sometimes coated with an antistatic agent for stable printing (see, for example, Patent Document 1).

JP-A-2000-131870

Among the inks used for offset printing of printing paper, there is an oxidative polymerization type ink that dries by reacting with oxygen in the air. The oxidative polymerization type ink dries as the solvent in the ink evaporates or permeates the pulp paper, and the oxidative polymerization of the remaining components progresses. Oxidation-polymerization type inks used for pulp paper generally contain a relatively large amount of solvent relative to the oxidatively-polymerized components so that the initiation of oxidative polymerization is hastened and the drying time is shortened. On the other hand, if the same ink as pulp paper is used on synthetic paper, which is less permeable to solvents than pulp paper, drying will not be sufficient in the same drying time as pulp paper. Ink may transfer to other synthetic paper.

For this reason, measures such as using ink for synthetic paper with a smaller amount of solvent than the ink used for pulp paper, or selecting an image that has a small amount of ink and is easy to dry as an image to be printed on synthetic paper. required, and the printing conditions were limited.

Also, print sheets are sometimes stacked and stored after printing. At this time, the ink on the printing surface may affect the printing paper superimposed thereon. For example, if printing is done on the front side of the printing paper and stacking them, and then printing is also done on the back side of each printing paper, the ink on the front side (derived component) will be the ink on the back side of the printing paper that is superimposed on it. A phenomenon that inhibits transcription may occur. This phenomenon is called a chemical ghost. When the chemical ghost occurs, the reproducibility of colors, densities, etc., will differ between the area printed on the back side and the area not overlapped on the printed part on the front side.

SUMMARY OF THE INVENTION An object of the present invention is to provide a printing paper and a printed matter which are excellent in ink versatility and drying property and which can suppress the occurrence of chemical ghosts.

As a result of intensive studies by the present inventors to solve the above problems, the ratio of the atomic concentration of nitrogen atoms on the surface of the antistatic layer, or the primary or secondary nitrogen compound in the antistatic layer The inventors have found that the above problems can be solved by printing paper having a low nitrogen content of a specific value or less and an oil absorption of a specific value or more, and completed the present invention.
That is, the present invention is as follows.

(1) A printing paper having a thermoplastic resin film including a porous layer and an antistatic layer provided on the porous layer of the thermoplastic resin film,
The oil absorption of the printing paper is 1.0 g/m ² or more,
When the surface of the printing paper on the antistatic layer side is measured by X-ray photoelectron spectroscopy, the ratio of the atomic concentration of nitrogen atoms to the total atomic concentration of nitrogen atoms and carbon atoms is 3.0% or less. ,
printing paper.

(2) the antistatic layer contains a nitrogen-containing compound,
the nitrogen-containing compound comprises a quaternary nitrogen-containing compound;
The content of the quaternary nitrogen-containing compound in the nitrogen-containing compound is 50% by mass or more,
The printing paper according to (1) above.

(3) the nitrogen-containing compound comprises a primary nitrogen-containing compound or a secondary nitrogen-containing compound;
The content of the primary nitrogen-containing compound and the secondary nitrogen-containing compound in the nitrogen-containing compound is 20% by mass or less,
The printing paper according to (1) above.

(4) the antistatic layer contains a nitrogen-containing compound and a cross-linking agent;
wherein the nitrogen-containing compound comprises a primary nitrogen-containing compound or a secondary nitrogen-containing compound;
The printing paper according to claim 1.

(5) A printing paper having a thermoplastic resin film including a porous layer and an antistatic layer provided on the porous layer of the thermoplastic resin film,
The oil absorption of the printing paper is 1.0 g/m ² or more,
The antistatic layer contains a nitrogen-containing compound, and the total content of primary or secondary nitrogen in the total nitrogen contained in the nitrogen-containing compound is 10% or less.
printing paper.

(6) the porous layer contains a thermoplastic resin and a filler;
The particle size distribution D10-D90 of the filler is 4 μm or less,
The printing paper according to any one of (1) to (5) above.

(7) The porous layer contains a soft polyolefin resin as the thermoplastic resin.
The printing paper according to any one of claims (1) to (6).

(8) having an intermediate layer between the substrate layer and the porous layer;
wherein the intermediate layer contains a filler having an average particle size larger than the thickness of the intermediate layer;
The printing paper according to any one of (1) to (7) above.

(9) The porous layer is a stretched film stretched in at least one axial direction.
The printing paper according to any one of (1) to (8) above.

(10) the printing paper according to any one of (1) to (9);
a printing layer provided on the printing paper;
printed matter.

(11) the printed layer is formed of an oxidative polymerization ink;
The printed matter according to (10) above.

According to the present invention, it is possible to provide a printing paper and a printed matter which are excellent in ink versatility and drying properties and which can suppress the occurrence of chemical ghosts.

1 is a cross-sectional view showing a structural example of printing paper according to an embodiment of the present invention; FIG. FIG. 2 is a top view showing each printed surface of printed matter A and printed matter B to be superimposed. FIG. 4 is a cross-sectional view showing fillers contained in an intermediate layer;

The printing paper and printed matter of the present invention will be described in detail below, but the description of the constituent elements described below is an example (representative example) as one embodiment of the present invention, and the contents thereof are specified. is not.
In the following description, the description of "(meth)acrylic" indicates both acrylic and methacrylic. Further, a numerical range represented using "to" means a range including the numerical values described before and after "to" as lower and upper limits.

(printing paper)
The printing paper of the present invention has a thermoplastic resin film including a porous layer, and an antistatic layer provided on the porous layer of the thermoplastic resin film.

<Oil absorption>
The oil absorption of the printing paper of the present invention is 1.0 g/m ² or more. When the oil absorption is 1.0 g/m ² or more, the solvent in the ink can be absorbed in a large amount in a short time when the ink is transferred to the printing paper. In the oxidative polymerization type ink, after the solvent evaporates from the ink or is absorbed by the printing paper, the oxidative polymerization of the remaining oxidative polymerization components progresses and the ink dries. Therefore, even if the ink for pulp paper contains a relatively larger amount of solvent than the ink for synthetic paper using a resin film, the printing paper of the present invention absorbs a large amount of the solvent in a short period of time, making it difficult to dry the ink. The time required can be shortened. That is, the printing paper of the present invention has excellent drying properties whether it is an ink for pulp paper or an ink for synthetic paper, and both inks can be used, so the ink is excellent in versatility. .

The oil absorption is preferably 1.5 g/m ² or more, more preferably 1.8 g/m ² or more, still more preferably 2.0 g/m ² or more, and 3.0 g/m 2 or more. ² or more is particularly preferable. The higher the oil absorption, the more solvent can be absorbed from the ink in a shorter period of time to speed up the drying speed. It is easy to prevent ink from showing through, and it is possible to quickly shift to the next process, which improves the work efficiency of printing.
Since it is sufficient to absorb the solvent in the ink, the oil absorption can be, for example, 10.0 g/m ² or less, and can be 5.0 g/m ² or less.

The above oil absorption is obtained by contacting mineral oil (manufactured by Wako Pure Chemical Industries, Ltd.; density: 0.84) on the printing surface of a printing paper cut into a certain size for 5 seconds, and calculating the mass and oil absorption of the printing paper before and after contact. The area of the surface is measured and calculated by the following formula.
Oil absorption (g/m ² ) =
{(mass after oil absorption (g))-(mass before oil absorption (g))}/(oil-absorbed area (m ² ))

<Atomic concentration ratio of nitrogen atoms>
When the surface of the antistatic layer side of the printing paper of the present invention is measured by X-ray photoelectron spectroscopy (XPS), nitrogen atoms with respect to the total atomic concentration (atom%) of nitrogen atoms and carbon atoms is 3.0% or less.
When the atomic concentration ratio of the nitrogen atoms is as small as 3.0% or less, the occurrence of chemical ghosts can be effectively suppressed. Although the mechanism by which chemical ghosts are generated is not necessarily clear, the present inventors discovered that nitrogen-containing compounds on the surface of printing paper come into contact with gas generated during oxidative polymerization of the ink and deteriorate, impeding ink transfer. It is speculated that it may cause The present inventors focused on reducing nitrogen-containing compounds, which are presumed to be causative agents of this chemical ghost, and controlled the ratio of nitrogen atoms on the surface of printing paper to a specific value of 3.0% or less. was found to be able to be suppressed. As described above, even if the oil absorption of the printing paper is greater than the specified value and the oxidative polymerization proceeds rapidly, if the atomic concentration ratio of the nitrogen atoms is less than the specified value, chemical ghosting can be effectively suppressed. , the transferability of the ink can be improved.

From the viewpoint of further suppressing chemical ghosts, the above ratio is preferably 2.8% or less, more preferably 2.6% or less, further preferably 2.4% or less. 0% or less is particularly preferable. The smaller the ratio, the higher the suppression effect, and it may be 0%, but when the antistatic layer contains a nitrogen-containing compound described later, it may be larger than 0%, for example, 0.01% or more.

The ratio (%) of the atomic concentration of the nitrogen atoms is the peak area of the N1s peak of the nitrogen atoms with respect to the sum of the peak area of the C1s peak of the carbon atoms measured by XPS and the peak area of the N1s peak of the nitrogen atoms. Calculated as a percentage.

The printing paper of the present invention may have a porous layer and an antistatic layer only on one side as long as it has a porous layer and an antistatic layer on at least one side, or may have a porous layer and an antistatic layer on both sides. It may have a quality layer and an antistatic layer. If only one side is provided with a porous layer and an antistatic layer, it is suitable to print first on the surface facing the antistatic layer and then on the back side. Further, the thermoplastic resin film may have a single-layer structure with only the porous layer, or may have a multilayer structure with layers other than the porous layer.

FIG. 1 is a cross-sectional view showing a configuration example of printing paper as one embodiment of the present invention.
As shown in FIG. 1, a printing paper 10 has a thermoplastic resin film 1 including a porous layer 2 provided on one side, and an antistatic layer 3 provided on the porous layer 2 . In this example of the printing paper 10, a porous layer 2a is also provided on the other side of the thermoplastic resin film 1, and an antistatic layer 3a is provided on the porous layer 2a. Further, in the example of the printing paper 10, the thermoplastic resin film 1 has a multi-layered structure and includes a base layer 4 and intermediate layers 5 and 5a provided on both sides of the base layer 4, respectively. The porous layers 2 and 2a are provided on the intermediate layers 5 and 5a, respectively, and constitute the outermost layer of the thermoplastic resin film 1. As shown in FIG. The porous layers 2 and 2a, the antistatic layers 3 and 3a, and the intermediate layers 5 and 5a, which are provided two by two, may have the same composition, thickness, or the like, or may be different.

Each layer constituting the printing paper of the present invention will be described below.

<Antistatic layer>
The antistatic layer can suppress adhesion of foreign matter to printing paper due to static electricity, deterioration of transportability due to blocking, and the like. From the viewpoint of reducing the effects of static electricity such as blocking, the antistatic layer is preferably provided as the outermost layer of the printing paper. The antistatic layer can be formed, for example, by applying a coating liquid containing an antistatic agent onto the porous layer.

<<Antistatic agent>>
The antistatic agent is not particularly limited, and known antistatic agents such as polymer type and metal oxide type antistatic agents can be used. Cationic antistatic agents, anionic antistatic agents, amphoteric antistatic agents, and nonionic antistatic agents are known, and any of them can be used. Cationic compounds include, for example, compounds having an ammonium salt structure or a phosphonium salt structure. Examples of the anionic type include alkali metal salts such as sulfonic acid, phosphoric acid and carboxylic acid, specifically alkali metal salts such as acrylic acid, methacrylic acid and (anhydrous) maleic acid (e.g. lithium salt, sodium salt, potassium salt). etc.) compounds having a structure in the molecular structure. The amphoteric type includes, for example, compounds containing both the aforementioned cationic and anionic structures in the same molecule, specifically betaine type. The nonionic type includes, for example, an ethylene oxide polymer having an alkylene oxide structure, a polymer having an ethylene oxide polymerization component in its molecular chain, and the like. Examples of metal oxide antistatic agents include fine particles containing metal oxides, such as colloidal silica sol having a metal oxide layer on the surface of colloidal silica. In addition, a polymer-type antistatic agent having boron in its molecular structure can also be mentioned as an example. You may use 1 type among these individually or in combination of 2 or more types.

Among them, a cationic polymer-type antistatic agent is preferable because of its good antistatic performance, and a nitrogen-containing polymer-type antistatic agent, such as a tertiary nitrogen or quaternary nitrogen (ammonium salt structure)-containing acrylic Polymers are more preferred.
A commercial product can also be used as an antistatic agent. Commercially available tertiary or quaternary nitrogen-containing acrylic polymers include, for example, Saftomer ST-1000, Saftomer ST-1100, Saftomer ST-1300, and Saftomer ST-3200 (each (manufactured by Mitsubishi Chemical Corporation) and the like.

<<Anchor Agent>>
The antistatic layer preferably contains an anchoring agent from the viewpoint of obtaining more stable adhesion to the ink. The anchoring agent is not particularly limited, and known anchoring agents can be used as appropriate. Usable anchoring agents include, for example, polyimine polymers, ethyleneimine adducts of polyamine polyamides, and mixtures thereof. Ethyleneimine adducts of polyimine polymers or polyamine polyamides include, for example, polyethyleneimine, poly(ethyleneimine-urea), and ethyleneimine adducts of polyamine polyamide; Allyl modified products, aralkyl modified products, alkyl modified products, benzyl modified products, cyclopentyl modified products, and aliphatic cyclic hydrocarbon modified products; hydroxides thereof; and complexes of the above. You may use 1 type among these individually or in combination of 2 or more types.

When an antistatic agent and an anchoring agent are used together, the content ratio of these can be appropriately set according to the required performance, and is not particularly limited. From the viewpoint of sufficiently exhibiting the performance of each component, the content of the anchoring agent is preferably 0 to 200 parts by weight, more preferably 0 to 150 parts by weight, based on 100 parts by weight of the antistatic agent, in terms of solid content. , more preferably 0 to 100 parts by mass, particularly preferably 0 to 50 parts by mass.

<<crosslinking agent>>
The antistatic layer can contain a cross-linking agent from the viewpoint of water resistance, stability over time, improvement of layer strength, and the like.
Examples of the cross-linking agent include epoxy compounds such as glycidyl ether and glycidyl ester, epoxy resins, isocyanate-based, oxazoline-based, formalin-based, hydrazide-based water-dispersible resins, and the like.
The content of the cross-linking agent in the antistatic layer is preferably 1 to 200 parts by mass, more preferably 100 parts by mass in total of the primary and secondary nitrogen-containing compounds, from the viewpoint of the stability of the solution over time. 10 to 170 parts by mass, more preferably 20 to 140 parts by mass.

A coating liquid used for forming the antistatic layer can be obtained by dissolving or dispersing various components such as an antistatic agent in a solvent. Water, methyl alcohol, ethyl alcohol, isopropyl alcohol, acetone, methyl ethyl ketone, ethyl acetate, toluene, xylene and the like are commonly used as solvents. The coating liquid is preferably an aqueous solution from the viewpoint of handleability during coating. The solid content concentration of the coating liquid is preferably about 0.1 to 20% by mass, more preferably 0.3 to 15% by mass, still more preferably 0.5 to 10% by mass.

As the coating device, various known coating devices can be used, and there is no particular limitation. For example, a coating device such as a die coater, bar coater, lip coater, roll coater, gravure coater, spray coater, blade coater, air knife coater, and size press coater can be used.

<<Nitrogen-containing compound>>
The antistatic layer may contain nitrogen-containing compounds.
Examples of nitrogen-containing compounds include amine compounds, imine compounds, amide compounds, imide compounds, isocyanate compounds, urethane compounds, and nitrile compounds. Among them, from the viewpoint of suppressing chemical ghosts, the nitrogen-containing compound is preferably an amide compound, an imide compound, an isocyanate compound, a urethane compound, or a nitrile compound. However, even an amine compound or imine compound can be used without problems by controlling the substitution of the amino group or imino group.
The nitrogen-containing compound can be blended as the above-described antistatic agent, anchoring agent, etc., but the antistatic layer can contain antistatic agents, anchoring agents, etc. other than the above nitrogen compounds.

The nitrogen-containing compound can contain any one of primary to quaternary nitrogen-containing compounds, but preferably contains a quaternary nitrogen-containing compound because of its high effect of suppressing chemical ghosts.
When the nitrogen compound contains a quaternary nitrogen-containing compound, the content of the quaternary nitrogen compound in the nitrogen compound is preferably 50% by mass or more, more preferably 70% by mass or more, and 90% by mass. It is more preferably 95% by mass or more, and particularly preferably 95% by mass or more. As the content of the quaternary nitrogen compound in the nitrogen compound increases, it is easier to suppress the chemical ghost.

When the nitrogen-containing compound contains a primary nitrogen-containing compound or a secondary nitrogen-containing compound, the total content of the primary nitrogen-containing compound and the secondary nitrogen-containing compound in the nitrogen compound is 20% by mass or less. It is preferably 15% by mass or less, more preferably 10% by mass or less, and particularly preferably 5% by mass or less. The lower the content of the primary and secondary nitrogen-containing compounds in the nitrogen compound, the easier it is to suppress chemical ghosts.

The total content (pieces) of primary to tertiary nitrogen in the total nitrogen (pieces) contained in the nitrogen-containing compound is preferably 35% or less, more preferably 30% or less, and 25 % or less. In addition, the total content of primary or secondary nitrogen in the total nitrogen contained in the nitrogen-containing compound is preferably 10% or less, more preferably 9% or less, and 7% or less. is more preferable, and 5% or less is particularly preferable. The lower the content of primary to tertiary nitrogen, particularly primary to secondary nitrogen, the easier it is to suppress chemical ghosts. The content of primary to quaternary nitrogen in the total nitrogen contained in the nitrogen-containing compound can be measured by, for example, a nuclear magnetic resonance apparatus or an X-ray optical spectrometer.

In the printing paper of the present invention, even if the ratio of the atomic concentration (atom%) of nitrogen atoms does not satisfy the condition of 3.0% or less, the primary or If the total content of secondary nitrogen is 10% or less, the occurrence of chemical ghosts can be effectively suppressed as in the case where the atomic concentration ratio of nitrogen atoms is 3.0% or less. According to the investigations of the present inventors, among the nitrogen-containing compounds presumed to be the causative agents of chemical ghosts, lower nitrogen-containing compounds containing primary or secondary nitrogen that are particularly susceptible to deterioration in contact with gas have been identified as specific values. It was found that the chemical ghost can be suppressed by the following control.

When the nitrogen-containing compound contains primary to tertiary nitrogen-containing compounds, the antistatic layer preferably further contains a cross-linking agent. By coordinating or covalently bonding the cross-linking agent to the nitrogen atoms of the primary to tertiary nitrogen-containing compounds, the primary to tertiary nitrogen-containing compounds, especially the highly reactive lower amine compounds, are reduced. It is presumed that even if the ink comes into contact with the gas generated when the ink oxidizes and polymerizes and dries, there is little deterioration, and it is easy to suppress the chemical ghost. If the antistatic agent contains a cross-linking agent and the total content of the primary to tertiary nitrogen-containing compounds in the nitrogen-containing compound is within the above-described range, chemical ghosts are more effectively suppressed. be able to. When the cross-linking agent is a nitrogen-containing compound (especially a primary nitrogen-containing compound or a secondary nitrogen-containing compound), self-crosslinking that also contains a group (such as an epoxy group) that can react with an amine or the like in the molecule Preferably possible.

The ratio (%) of the atomic concentration of nitrogen atoms on the surface of the antistatic layer side of the printing paper described above, or the total content of primary or secondary nitrogen in the total nitrogen contained in the nitrogen-containing compound, By adjusting the solid content of components containing a nitrogen-containing compound, such as antistatic agents and anchoring agents, in the coating solution for forming the antistatic layer, it is possible to control the solid content to a specific value or less.

<Thermoplastic resin film>
As long as the thermoplastic resin film includes a porous layer on the outermost surface, the thermoplastic resin film may be a single-layer film having only the porous layer as described above, or may include other layers such as a substrate layer and an intermediate layer. It may be a multilayer film.
Further, each layer of the thermoplastic resin film may be a non-stretched film, but if it is a stretched film stretched in at least one axial direction, it is easy to obtain thickness, stiffness, etc. that are excellent in printability as printing paper. In addition, it is preferable because the surface or interface between layers can be easily flattened.

<<Porous layer>>
The porous layer has a large number of pores, absorbs the solvent in the ink, and enhances the drying property of the ink. The greater the ratio of the pores of the porous layer communicating with each other, the greater the oil absorption of the printing paper, and the better the drying properties of the ink. On the other hand, if the proportion of independent pores in the porous layer is high, the oil absorption will be low and the drying property of the ink will be low. As described above, since the degree of communication of the pores is proportional to the oil absorption of the printing paper, it is possible to determine whether or not there are sufficient pores communicating with each other in the porous layer based on the oil absorption of the printing paper. can.

The porous layer preferably contains a thermoplastic resin and a filler from the viewpoint of formability of communicating pores.

<<<thermoplastic resin>>>
Examples of thermoplastic resins include polyolefin resins, polyester resins, polyamide resins, polystyrene resins, polyvinyl chloride resins, and polycarbonate resins. One of these thermoplastic resins can be used alone or in combination of two or more. From the viewpoint of improving layer strength, the thermoplastic resin is preferably a polyolefin-based resin or a polyester-based resin, and more preferably a polypropylene-based resin or a polyethylene-based resin.

The thermoplastic resin preferably comprises a hydrophobic or non-polar resin. Thereby, the oil absorption can be improved when the pores in the porous layer are in communication with each other. As used herein, a hydrophobic or non-polar resin refers to a resin having a solubility parameter (SP value) of, for example, 10 or less. The SP value is preferably 9.5 or less, more preferably 9.0 or less, and even more preferably 8.0 or less. Also, the SP value may be 6.5 or more, and may be 7.0 or more. The SP value is a value calculated by the method proposed by Small.

Hydrophobic or nonpolar thermoplastic resins include, for example, polyolefin resins and polystyrene resins. The content of the hydrophobic or nonpolar resin is preferably 80% by mass or more, more preferably 90% by mass or more, and still more preferably 95% by mass or more, based on the total mass of the thermoplastic resin. The content of the hydrophobic or non-polar resin may be, for example, 99% by mass or less, 98% by mass or less, or 97% by mass or less based on the total mass of the thermoplastic resin. All of the thermoplastic resin can be composed of hydrophobic or non-polar resins.

From the viewpoint of suppressing edge picking, the porous layer preferably contains a soft polyolefin resin as the thermoplastic resin. A soft polyolefin resin refers to a polyolefin resin having a melting energy of 75 J/g or less as measured by differential scanning calorimetry (DSC). The melting energy is calculated from the peak area of the endothermic peak observed in DSC. Edge picking is a phenomenon in which deformation such as fluffing of the paper surface or peeling such as peeling occurs during printing.

The content of the soft polyolefin resin in the porous layer is preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably 4% by mass or more. The content is preferably 15% by mass or less, more preferably 10% by mass or less, and even more preferably 8% by mass or less. When the content is 1% by mass or more, there is a tendency that voids are excessively generated during stretching, and the occurrence of edge picking due to such voids can be suppressed. On the other hand, when the content is 15% by mass or less, there is a tendency that a decrease in the proportion of independent pores is suppressed and high drying property is obtained.

From the viewpoint of suppressing edge picking, the tensile elastic modulus of the soft polyolefin resin is preferably 1.2 GPa or less. The tensile modulus is measured at a temperature of 23° C. in accordance with JIS K7161-1:2014 and JIS K7161-2:2014.

The porous layer may further contain an acid-modified resin as a thermoplastic resin from the viewpoint of preventing the filler from falling off. Examples of acid-modified resins include maleic acid-modified polyolefins. The content of the acid-modified resin is preferably 10% by mass or less, more preferably 5% by mass or less, and still more preferably 3% by mass or less, based on the total mass of the thermoplastic resin. The content of the acid-modified resin may be, for example, 0.1% by mass or more, 0.5% by mass or more, or 1% by mass or more based on the total mass of the thermoplastic resin.

<<<Filler>>>
Examples of fillers include inorganic fillers and organic fillers, either of which can be used alone or in combination. When a thermoplastic resin containing a filler is stretched, it becomes easy to form a large number of fine pores with the filler as the nucleus.

Examples of inorganic fillers include heavy calcium carbonate, light calcium carbonate, calcined clay, talc, diatomaceous earth, barium sulfate, magnesium oxide, zinc oxide, titanium dioxide, and silicon dioxide.
Examples of organic fillers include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polystyrene, polyamide, polycarbonate, polyethylene sulfide, polyphenylene sulfide, polyimide, polyetherketone, polyetheretherketone, polymethylmethacrylate, and poly-4-methyl-1. - pentene, homopolymers of cyclic olefins, copolymers of cyclic olefins and ethylene, and the like.
The inorganic filler or organic filler may be surface-treated with a fatty acid or the like from the viewpoint of dispersing the filler having a relatively small particle size in the resin.

One of the above inorganic fillers or organic fillers can be used alone or in combination of two or more. Among them, inorganic fillers are preferable from the viewpoint of ease of adjustment of the particle size distribution. Among the inorganic fillers, heavy calcium carbonate or light calcium carbonate is preferable from the viewpoints of pore formation and cost, and titanium dioxide is preferable from the viewpoint of weather resistance.

The median diameter (D50) of the filler particles is preferably 0.01 μm or more, more preferably 0.1 μm or more, from the viewpoint of uniform dispersion in the porous layer. In addition, the median diameter of the filler is preferably 10 μm or less, more preferably 3 μm, from the viewpoint of facilitating the separation of components such as pigments and binders in the ink from the solvent component, and preventing color settling or poor drying of the ink. or less, more preferably 1.5 μm or less, particularly preferably 1.3 μm or less.
The particle size of the filler can also be determined as the average dispersed particle size when dispersed in the thermoplastic resin by melt-kneading and dispersion. Specifically, the cut surface of the film is observed with an electron microscope, the maximum diameters of at least 10 particles of the filler are measured, and the average value is taken as the average dispersed particle diameter.

The particle size distribution D10-D90 of the filler is preferably 4 μm or less, more preferably 3.5 μm or less, still more preferably 3 μm or less. When the particle size distribution D10-D90 is within the above range, the pores generated in the porous layer during stretching are easily communicated, and the oil absorption is easily increased to a specific value of 1.0 g/m ² or more. . The particle size distribution D10-D90 of the filler is usually 0.01 μm or more, and may be 0.1 μm or more, preferably 0.3 μm or more, from the viewpoint of cost.

The particle size distribution D10-D90 of the filler can be obtained as follows.
The following D10, D50 and D90 are measured with a laser diffraction particle size distribution analyzer. The absolute value of the difference between the measured D90 and D10 is obtained as the particle size distribution D10-D90. Water, methanol, ethanol, ethylene glycol, etc. are used as appropriate for the solvent used in the measurement. Acoustic dispersion is performed.
D10: Cumulative 10% by volume particle diameter of filler particles (μm)
D50: Cumulative 50% by volume particle diameter of filler particles (μm)
D90: Cumulative 90% by volume particle diameter of filler particles (μm)

The content of the filler in the porous layer is preferably 45 parts by mass or more, more preferably 60 parts by mass or more, relative to 100 parts by mass of the thermoplastic resin, from the viewpoint of pore formation. It is preferably 75 parts by mass or more, and particularly preferably 100 parts by mass or more. On the other hand, the content of the filler in the porous layer is preferably 250 parts by mass or less, more preferably 200 parts by mass with respect to 100 parts by mass of the thermoplastic resin, from the viewpoint of maintaining the strength of the multilayer layer appropriately. parts or less, more preferably 150 parts by mass or less, and particularly preferably 125 parts by mass or less.

<<<Porosity>>>
From the viewpoint of increasing the number of continuous pores, the porosity, which indicates the ratio of pores in the porous layer, is preferably 10% or more, more preferably 15% or more, and further preferably 20% or more. It is preferably 25% or more, and particularly preferably 25% or more. From the viewpoint of increasing surface strength and reducing printing defects such as edge picking, the porosity is preferably 50% or less, more preferably 45% or less, and even more preferably 40% or less. .

The porosity is an index representing the number of pores, and is not necessarily linked to the oil absorption. For example, even when a large number of pores are formed and the porosity is high, if the degree of communication between the pores is small, the oil absorption is also small. Thus, the porosity and the oil absorption are independent index values, and even if the porosity of the porous layer of the printing paper is the same, the oil absorption is not necessarily the same.

The porosity can be obtained from the ratio of the area occupied by pores in a certain region of the cross section of the printing paper observed with an electron microscope. Specifically, an arbitrary part of the printing paper is cut, embedded in epoxy resin and solidified, then cut perpendicular to the surface direction of the printing paper using a microtome, and the cut surface becomes the observation surface. Attach it to the observation sample table as shown. Gold, gold-palladium, or the like is vapor-deposited on the observation surface, and the pores are observed with an electron microscope at an arbitrary magnification (for example, a magnification of 500 to 3000), and the observed area is captured as image data. The obtained image data is subjected to image processing by an image analysis device, and the area ratio of the pore portions is obtained to obtain the porosity. In this case, the porosity can be obtained by averaging the measured values obtained by observation at arbitrary 10 or more points.

<<Base material layer>>
The base layer functions as a support for the thermoplastic resin film and imparts strength, stiffness, and the like to the printing paper.
From the viewpoint of imparting opacity, the substrate layer preferably contains a thermoplastic resin and a filler. This makes it easier to prevent the pattern printed on one side from being seen through the other side.

As the thermoplastic resin for the substrate layer, the same thermoplastic resin as that for the porous layer can be used. Examples thereof include polyolefin resins, polyester resins, polyamide resins, polystyrene resins, polyvinyl chloride resins, and polycarbonate resins. mentioned. These resins may be used alone or in combination of two or more. The thermoplastic resin is preferably a polyolefin-based resin or a polyester-based resin, more preferably a polypropylene-based resin or a polyethylene-based resin.

As for the filler for the base material layer, the same filler as for the porous layer can be used. Examples of inorganic fillers include heavy calcium carbonate, light calcium carbonate, calcined clay, talc, diatomaceous earth, barium sulfate, magnesium oxide, zinc oxide, titanium dioxide, and silicon dioxide. Examples of organic fillers include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polystyrene, polyamide, polycarbonate, polyethylene sulfide, polyphenylene sulfide, polyimide, polyetherketone, polyetheretherketone, polymethylmethacrylate, poly-4-methyl- Examples include 1-pentene, homopolymers of cyclic olefins, and copolymers of cyclic olefins and ethylene. These inorganic fillers or organic fillers can be used alone or in combination of two or more.

The average particle size of the filler is preferably 0.01 μm or more, more preferably 0.1 μm or more, from the viewpoint of pore formation. In the case of improving opacity or printability by generating voids inside by stretching, the average particle diameter of the filler is preferably It is 30 μm or less, more preferably 20 μm or less, more preferably 10 μm or less.

In addition, the "average particle size" of the filler in this specification is calculated according to the following procedure. First, the printing paper is cut out and its cross section is exposed. The cross section is magnified to an appropriate magnification (for example, 1,000 times) using a scanning electron microscope, and a photographic image is taken. From the photographed image, the average value of 100 randomly selected particle diameters (major diameters) present in the sample is calculated. The average particle size is calculated from this.

The filler content in the substrate layer is preferably 1% by mass or more, more preferably 3% by mass or more, and particularly preferably 5% by mass or more. On the other hand, the filler content in the substrate layer is preferably 45% by mass or less, more preferably 40% by mass or less, and particularly preferably 35% by mass or less. If the content is within the above range, the printing paper will have appropriate strength and will be easy to handle.

From the viewpoint of improving film strength, the substrate layer is preferably stretched in at least one axial direction, and more preferably a stretched film that is stretched in two axial directions.

<< middle layer >>
The intermediate layer is provided between the substrate layer and the porous layer, and prevents the solvent component of the ink absorbed by the porous layer from reaching the substrate layer and thereby suppressing deformation such as waving of the printing paper. Such deformation is called solvent attack.

From the viewpoint of suppressing solvent attack, the intermediate layer preferably contains a thermoplastic resin, and more preferably contains an amorphous resin as the thermoplastic resin.
As the thermoplastic resin, the same thermoplastic resin as used in the porous layer can be used.

As the amorphous resin, an amorphous resin having a glass transition temperature of 140°C or less is preferable, and an amorphous resin having a glass transition temperature of 70 to 140°C is more preferable. If the glass transition temperature of the amorphous resin is 70° C. or higher, sticking to the roll is reduced and moldability is easily improved. It is easily absorbed and retained, preventing solvent penetration into the base material layer and suppressing solvent attack. When producing a printing paper having an intermediate layer, it is preferable to set the stretching temperature to a temperature 10° C. or more higher than the glass transition temperature of the amorphous resin.

Examples of amorphous resins include cyclic olefin resins, atactic polystyrene, petroleum resins, polycarbonates, and acrylic resins. The amorphous resin is preferably a cyclic olefin resin, more preferably an ethylene-cyclic olefin copolymer. In particular, the intermediate layer preferably contains a polypropylene-based resin as the thermoplastic resin and an ethylene-cyclic olefin copolymer as the amorphous resin.

The mixing ratio of the thermoplastic resin other than the amorphous resin in the intermediate layer and the amorphous resin is 0 to 80% by mass of the thermoplastic resin from the viewpoint of sufficiently suppressing solvent attack. is preferably 20 to 100% by mass, the thermoplastic resin is 20 to 70% by mass, the amorphous resin is more preferably 30 to 80% by mass, and the thermoplastic resin is 30 to 60% by mass. and more preferably 40 to 70% by mass of the amorphous resin.

The porosity of the intermediate layer is preferably 5% or less from the viewpoint of reducing the amount of solvent in the ink (especially high boiling point petroleum solvents such as mineral oil) that reaches the substrate layer through the pores. % or less is more preferable. The intermediate layer may contain a filler as long as the porosity is in the range of 5% or less.

When the intermediate layer contains a filler, the filler contained in the intermediate layer is a filler having an average particle size larger than the thickness of the intermediate layer (hereinafter also referred to as a coarse filler) from the viewpoint of suppressing chemical ghosts. is preferred. The coarse filler facilitates imparting roughness to the surface of the porous layer on the intermediate layer. If the surface is rough, voids will occur between the printed materials when the printed materials are stacked and stored. The gas generated by the oxidative polymerization of the ink is discharged to the outside through the voids and is suppressed from staying on the surface of the printed matter, so chemical ghosts are more likely to be suppressed.

The content of the coarse filler in the intermediate layer is preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably 5% by mass or more. The content is preferably 25% by mass or less, more preferably 20% by mass or less, and even more preferably 15% by mass or less. When the content is 1% by mass or more, the effect of suppressing the chemical ghost described above is likely to be obtained. Further, when the content is 25% by mass or less, the formation of pores in the intermediate layer is suppressed, and the arrival of the solvent to the substrate layer is easily suppressed.

The distance (K) from the surface of the coarse filler to the surface of the porous layer when the center of the coarse filler is positioned at the center in the thickness direction of the intermediate layer preferably exceeds 0 μm. When the distance (K) exceeds 0 μm, it is likely to prevent the coarse filler from exceeding the porous layer and being exposed on the surface of the printing paper. In addition, it is easy to prevent the generation of paper dust due to the detachment of the coarse filler from the printing paper and the detachment.

As shown in FIG. 3, the distance (K) is determined by the following formula, where M1 is the thickness of the porous layer, M2 is the thickness of the intermediate layer, and φ is the average particle size of the coarse filler. M1 and M2 refer to the thicknesses of the porous layer and the intermediate layer at positions where coarse particles do not exist.
K=M1-(φ-M2)/2

The distance (K) is preferably 10 μm or less, more preferably 9 μm or less, and even more preferably 6 μm or less. When the distance (K) is 10 μm or less, the surface of the porous layer described above is likely to be roughened, and chemical ghosts are more likely to be suppressed.

<<<Other Additives>>>
Each layer of the thermoplastic resin film may contain additives such as heat stabilizers (antioxidants), light stabilizers, dispersants, and lubricants, if necessary. When a heat stabilizer is used, each layer usually contains 0.001-1% by weight of heat stabilizer. Examples of heat stabilizers include sterically hindered phenol-based, phosphorus-based, and amine-based stabilizers. When light stabilizers are used, each layer usually contains 0.001 to 1% by weight of light stabilizer. Examples of light stabilizers include sterically hindered amine-based, benzotriazole-based, and benzophenone-based light stabilizers. Dispersants or lubricants can be used, for example, for the purpose of dispersing inorganic fillers. The amount of dispersant or lubricant used is usually within the range of 0.01 to 4% by mass. Examples of dispersants or lubricants include silane coupling agents, higher fatty acids such as oleic acid and stearic acid, metal soaps, polyacrylic acid, polymethacrylic acid, and salts thereof.

(Method for manufacturing printing paper)
The method for producing the printing paper of the present invention is not particularly limited. For example, the printing paper can be produced by coating a thermoplastic resin film with a coating liquid for forming an antistatic layer.

The thermoplastic resin film is formed by cast molding, calendar molding, rolling molding, inflation molding, etc., in which a molten resin is extruded into a sheet by a single-layer or multi-layer T die, I die, etc. connected to a screw extruder, for example. It can be molded into a film. A thermoplastic resin film may be formed by casting or calendering a mixture of a thermoplastic resin and an organic solvent or oil and then removing the solvent or oil. The materials for each layer of the thermoplastic film are selected and blended so that each layer has the composition described above.

Methods for laminating each layer of the thermoplastic resin film include, for example, a multi-layer die method using a feed block and a multi-manifold, an extrusion lamination method using a plurality of dies, and the like, and each method can be combined.

When the thermoplastic resin film includes a plurality of stretched layers, each layer may be stretched individually before lamination, or may be stretched collectively after lamination. Moreover, after lamination|stacking on the stretched layer, you may stretch|stretch again.

As the stretching method, for example, a longitudinal stretching method using a peripheral speed difference between roll groups, a transverse stretching method using a tenter oven, a sequential biaxial stretching method combining these, a rolling method, a simultaneous two-stretching method using a combination of a tenter oven and a pantograph. An axial stretching method or a simultaneous biaxial stretching method using a combination of a tenter oven and a linear motor can be used. A simultaneous biaxial stretching (inflation molding) method can also be used, in which a circular die connected to a screw type extruder is used to extrude a molten resin into a tubular shape, and then air is blown into the tubular shape.

The stretching temperature during stretching can be set in consideration of the composition of each layer, for example, the melting point of the thermoplastic resin. For example, the stretching temperature is preferably equal to or lower than the melting point of the thermoplastic resin, and more preferably within the range of 2 to 20° C. lower than the melting point. When the thermoplastic resin to be used is an amorphous resin, the stretching temperature is preferably in the range of the glass transition temperature of the thermoplastic resin or higher. Also, when the thermoplastic resin is a crystalline resin, the stretching temperature should be above the glass transition point of the non-crystalline portion of the thermoplastic resin and below the melting point of the crystalline portion of the thermoplastic resin. is preferred, and specifically, a temperature lower than the melting point of the thermoplastic resin by 2 to 60°C is preferred.

The stretching speed is not particularly limited, but from the viewpoint of stable stretching molding, it is preferably in the range of 20 to 350 m/min.
In addition, the draw ratio can also be appropriately determined in consideration of the properties of the thermoplastic resin to be used. For example, when a thermoplastic resin film containing a propylene homopolymer or a copolymer thereof is stretched in one direction, the draw ratio is usually about 1.2 times or more, preferably 2 times or more, more preferably 2 times or more. is 5 times or more, usually 12 times or less, preferably 10 times or less. On the other hand, the stretch ratio in biaxial stretching is usually 1.5 times or more, preferably 10 times or more, and usually 60 times or less, preferably 50 times or less, in terms of area stretch ratio. be.

When a thermoplastic resin film containing a polyester resin is stretched in one direction, the draw ratio is usually 1.2 times or more, preferably 2 times or more, and usually 10 times or less. , preferably 5 times or less. The draw ratio in biaxial stretching is usually 1.5 times or more, preferably 4 times or more, and usually 20 times or less, preferably 12 times or less, in terms of area draw ratio.
If the draw ratio is within the above range, the desired porosity can be obtained and the opacity tends to be improved. In addition, the thermoplastic resin film tends to be less likely to break and can be stably stretched.

<Surface treatment>
The thermoplastic resin film is preferably oxidized. Oxidation treatment can adjust the ratio of polar groups present on the film surface, and can adjust the atomic concentration of oxygen atoms. As a result, it is easy to obtain chemical bonding strength with the ink, and it is easy to improve the adhesion between the printing paper and the ink.
Examples of oxidation treatment include corona discharge treatment, flame treatment, plasma treatment, glow discharge treatment, ozone treatment, and the like, and these treatments can be combined. Among them, corona discharge treatment or flame treatment is preferable, and corona treatment is more preferable.

The amount of discharge when performing corona discharge treatment is preferably 600 J/m ² (10 W·min/m ² ) or more, more preferably 1,200 J/m ² (20 W·min/m ² ) or more. . Also, the discharge amount is preferably 12,000 J/m ² (200 W·min/m ² ) or less, more preferably 10,800 J/m ² (180 W·min/m ² ) or less. The amount of discharge when flame treatment is performed is preferably 8,000 J/m ² or more, more preferably 20,000 J/m ² or more. Also, the discharge amount is preferably 200,000 J/m ² or less, more preferably 100,000 J/m ² or less.

The antistatic layer is prepared by mixing an antistatic agent, an anchoring agent, a solvent, etc., to prepare a coating solution for forming the antistatic layer described above, and using a coating device to form a porous layer of a thermoplastic resin film. It can be formed by applying a coating liquid thereon.

(Characteristics of printing paper)
<Thickness>
The thickness (total thickness) of the printing paper may be appropriately set according to the application or required performance. The total thickness of the printing paper means the sum of the thicknesses of the layers forming the printing paper. The total thickness of the printing paper is preferably 51 µm or more, more preferably 63 µm or more, still more preferably 75 µm or more, and preferably 550 µm or less, more preferably 400 µm or less, still more preferably 300 µm or less. If the total thickness of the printing paper is within the above range, problems are less likely to occur in offset printing, and the utility value of the printing paper tends to be high.

The thickness of each layer constituting the printing paper is designed so that the total thickness is within the above range.
Moreover, when the intermediate layer, the porous layer and the antistatic layer are provided on both sides of the substrate layer, the thickness of each layer provided on both sides may be the same or different.

When the pores in the porous layer communicate with each other, the oil absorption can be controlled by changing the thickness of the porous layer. In this case, the thickness of the porous layer is preferably 3 µm or more, more preferably 5 µm or more, still more preferably 7 µm or more, and preferably 20 µm or less, more preferably 15 µm or less, still more preferably 10 µm or less. When the thickness of the porous layer is within the above range, picking is less likely to occur and a high oil absorption can be easily obtained.

The thickness of the intermediate layer is preferably 0.5 μm or more, more preferably 1 μm or more, still more preferably 2 μm or more, and preferably 20 μm or less, more preferably 10 μm or less, still more preferably 5 μm or less. When the thickness of the intermediate layer is within the above range, it becomes easy to prevent solvent attack and the like while obtaining good moldability.

The thickness of the antistatic layer can be controlled by the coating amount of the coating liquid for forming the antistatic layer. From the viewpoint of production cost, suppression of stickiness, or effect of stabilizing ink adhesion over time, etc., the coating amount is preferably 0.01 g/m ² or more in terms of solid content, and 0.02 g/m ² or more. It is more preferably 3 g/m ² or less, more preferably 1 g/m ² or less, and even more preferably 0.5 g/m ² or less.

<Surface resistivity>
The surface resistivity of the printing paper is preferably 14 (logΩ) or less. When the surface specific resistance is within the above range, it is possible to improve transportability in flat-sheet printing and reduce troubles caused by static electricity in post-processing such as folding and bookbinding.

(Usage of printing paper)
According to the printing paper of the present invention, it is possible to obtain printed matter with high gloss and excellent weather resistance by printing. Therefore, it is useful for commercial printed materials such as posters, pamphlets, catalogs, signboards and menus, publications such as books, maps, book covers and bookmarks, and wrapping paper. Among these uses, the printing paper of the present invention has high basic performance, so it is suitable for outdoor use such as election posters and billboard posters, which are affected by sunlight and rainwater, and for use in saunas, such as posters. It is useful in applications such as use in environments exposed to water such as public baths and bathrooms, and use in environments where there is a possibility of contact with water such as menus of restaurants and the like. Moreover, since it is compatible with both ink for pulp paper and ink for synthetic paper, there is no need to replace the ink, and the workability of printing can be improved.

(printed matter)
The printing paper of the present invention can be applied to various printing methods such as offset printing, letterpress printing, flexographic printing, and screen printing, but is particularly suitable for offset printing. Various inks such as offset printing ink, letterpress printing ink, flexographic printing ink, and screen printing ink can be used for the printing paper of the present invention. In particular, offset printing ink can be used. preferable. In addition, the viscosity of the ink varies depending on the type of ink, the printing method, etc., and is not particularly limited.

Although it was difficult to apply to synthetic paper, the printing paper of the present invention has excellent printability and ink even for oxidative polymerization ink containing a relatively large amount of solvent, which has been widely used for pulp paper. Has drying properties. Therefore, even when the printing paper of the present invention is used in place of pulp paper, there is no need to replace the ink. In addition, the printing paper of the present invention has excellent printability and ink drying properties even for inks for synthetic paper containing less evaporation-drying components, permeation-drying components, and the like, and UV-curing inks. That is, the printing paper of the present invention can be used with any of the inks of the various printing methods described above, and has high ink versatility. Therefore, according to the present invention, there is provided a printed material comprising the printing paper described above and a printing layer provided on the printing paper. The printed layer can be formed by printing using an ink such as the above-described oxidative polymerization type ink.

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to the following examples. Descriptions of "parts", "%", etc. in the examples are based on mass unless otherwise specified.

(Preparation of coating liquid)
Coating solutions 1 to 5 for forming an antistatic layer were prepared as follows.

<Coating liquid 1>
Pure water was added to dilute an antistatic agent (trade name: Saftomer ST-3200, manufactured by Mitsubishi Chemical Corporation, quaternary ammonium salt) to a solid content of 1.2% by mass, to obtain a coating liquid 1. .

<Coating liquid 2>
Antistatic agent (trade name: Saftomer ST-3200, manufactured by Mitsubishi Chemical Corporation, quaternary ammonium salt) has a solid content of 1.2% by mass, modified polyethyleneimine (trade name: Saftomer AC-2000, manufactured by Mitsubishi Chemical Corporation, Secondary and tertiary amine-containing compound) was diluted by adding pure water so that the solid content was 0.23% by mass, and a coating liquid 2 was obtained.

<Coating liquids 3 and 4>
In coating solution 2, the solid content of modified polyethyleneimine (trade name: Saftomer AC-2000, manufactured by Mitsubishi Chemical Corporation, secondary and tertiary amine-containing compounds) was 0.38% by mass and 0.5% by mass, respectively. Pure water was added to dilute them so that each coating liquid 3 and 4 was obtained.

<Coating liquid 5>
Antistatic agent (trade name: Saftomer ST-3200, manufactured by Mitsubishi Chemical Corporation, quaternary ammonium salt) has a solid content of 1.2% by mass, modified polyethyleneimine (trade name: Polymin SK, manufactured by BASF, tertiary Amine-containing compound) has a solid content of 0.25% by mass, and a self-crosslinkable cross-linking agent (trade name: WS4082, manufactured by Seiko PMC, secondary amine and epoxy group-containing compound) has a solid content of 0.3% by mass. Pure water was added to dilute the solution to obtain a coating solution 5.

Table 1 shows the compositions of Coating Liquids 1-5.

(Example 1)
(I) Polypropylene resin (trade name: Novatec PP MA3, manufactured by Japan Polypropylene Corporation, MFR (230°C, 2.16 kg load): 11 g/10 min, melting energy: 95 J/g) 80 parts by mass, heavy calcium carbonate particles (Trade name: Softon 1800, manufactured by Bihoku Funka Kogyo Co., Ltd., average particle size: 1.25 μm) 19.5 parts by mass, and titanium dioxide particles (trade name: Typaque CR-60, manufactured by Ishihara Sangyo Co., Ltd., average particle size: The resin composition (5) mixed with 0.5 parts by mass of 0.21 μm) was melt-kneaded by an extruder set at 270°C. This was extruded into a sheet and cooled with a cooling roll to obtain a non-stretched sheet. Next, the non-stretched sheet was reheated to 150° C. and then stretched 4.8 times in the sheet flow direction using the speed difference between the rolls to obtain a longitudinally stretched resin film.

(II) Polypropylene resin (trade name: Novatec PP MA3, manufactured by Nippon Polypro Co., Ltd.) 46 parts by mass, maleic anhydride-modified polypropylene resin (trade name: Modic P928, manufactured by Mitsubishi Chemical Corporation, melting point: 155 to 165 ° C., specific gravity: 0 .89 to 0.91 g/m ³ , melting energy: 89 J/g) 1 part by mass, light calcium carbonate particles surface-treated with fatty acid (particle size distribution D10-D90: 0.6 μm, D50: 0.5 μm)52. A resin composition (1) containing 5 parts by mass and 0.5 parts by mass of titanium dioxide particles (trade name: Typaque CR-60, manufactured by Ishihara Sangyo Co., Ltd.) was mixed with a high-speed mixer. Thereafter, using a twin-screw kneading extruder whose cylinder temperature was set to 210° C., the mixture was melt-kneaded at a rotational speed of 600 rpm while degassing through vent holes.

On the other hand, polypropylene resin (trade name: Novatec PP MA3, manufactured by Nippon Polypro Co., Ltd.) 48.5 parts by mass, ethylene-cyclic olefin copolymer (trade name: APEL 6011T, manufactured by Mitsui Chemicals, MFR (230 ° C., 2.16 kg load): 26 g/10 minutes, melting energy: 0 J/g) 48.5 parts by mass, and heavy calcium carbonate particles (trade name: Softon 1800, manufactured by Bihoku Funka Kogyo Co., Ltd.) 3 parts by mass. (4) was melt-kneaded with an extruder set at 270°C.
These resin compositions were then fed into one multi-layer die and laminated inside the die. This laminate is co-extruded into a sheet from a die, and laminated on one side of the longitudinally stretched resin film obtained in the step (I) so that the layer of the resin composition (1) is on the outside. , to obtain a laminated sheet having a three-layer structure.

(III) Using two extruders different from the above (II), the resin composition (1) and the resin composition (4) were melt-kneaded in the same procedure as in the above (II), and then the above ( It was supplied to a multilayer die different from II) and laminated inside the die. This laminate is co-extruded into a sheet form from a die, and on the surface of the longitudinally stretched resin film side (layer side of resin composition (5)) of the three-layer laminated sheet obtained in the step (II) , the layer of the resin composition (1) was placed on the outside. Thereby, porous layer (layer of resin composition (1))/intermediate layer (layer of resin composition (4))/base layer (layer of resin composition (5))/intermediate layer (layer of resin composition (4) layer)/porous layer (resin composition (1) layer) was laminated in this order to obtain a five-layer laminated sheet.

(IV) After cooling the obtained laminated sheet having a five-layer structure to 60°C, reheating it to 150°C again, stretching it 9 times in the sheet width direction using a tenter, and then annealing it at 165°C. did. After that, after cooling to 60 ° C. again, the ears were slit, and a thermoplastic resin film with a five-layer structure (the number of stretching axes of each layer: uniaxial stretching / uniaxial stretching / biaxial stretching / uniaxial stretching / 1 axial stretching), total thickness: 130 μm, thickness of each layer: (1)/(4)/(5)/(4)/(1)=8 μm/3 μm/108 μm/3 μm/8 μm).

(V) A high-frequency power source (equipment name: AGF-B10, manufactured by Kasuga Denki Co., Ltd.), an aluminum electrode with a length of 0.8 m, and a silicone-coated roll as a treater roll, with a gap between the electrode and the roll of 5 mm. While passing the thermoplastic resin film obtained in (IV) at a line processing speed of 25 m/min, corona discharge was applied to both surfaces of the film under the conditions of an applied energy density of 1800 J/m ² (30 W·min/m ² ). processed.

(VI) Coating liquid 1 is applied to both surfaces of the thermoplastic resin film after corona discharge treatment using a roll coater so that the solid content of the dried coating film is 0.02 g/m ² per side. did. The coating film was dried and solidified to obtain a printing paper of Example 1.

(Example 2)
In Example 1, the discharge amount of the resin composition for each layer was changed, and the total thickness was 130 µm (thickness of each layer: (1)/(4)/(5)/(4)/(1) = 5 µm/3 µm/ 114 μm/3 μm/5 μm), the printing paper of Example 2 was obtained in the same manner as in Example 1.

(Examples 3 and 4)
Printing papers of Examples 3 and 4 were obtained in the same manner as in Example 1, except that the coating liquid in (VI) of Example 1 was changed to Coating liquids 2 and 5, respectively.

(Example 5)
The resin composition (1) of Example 1 was composed of 39 parts by mass of a polypropylene resin (trade name: Novatec PP MA3, manufactured by Japan Polypropylene Corporation) and 1 part of a maleic anhydride-modified polypropylene resin (trade name: Modic P928, manufactured by Mitsubishi Chemical Corporation). Part by mass, fatty acid surface-treated light calcium carbonate particles (particle size distribution D10-D90: 0.6 μm, D50: 0.5 μm) 59.5 parts by mass, and titanium dioxide particles (trade name: Typaque CR-60, Ishihara Sangyo A printing paper of Example 5 was obtained in the same manner as in Example 1, except that the resin composition (2) was mixed with 0.5 parts by mass of the resin (manufactured by Co., Ltd.).

(Example 6)
The resin composition (1) of Example 1 was composed of 44 parts by mass of a polypropylene resin (trade name: Novatec PP MA3, manufactured by Japan Polypropylene Corporation) and 1 part of a maleic anhydride-modified polypropylene resin (trade name: Modic P928, manufactured by Mitsubishi Chemical Corporation). Parts by mass, heavy calcium carbonate particles (particle size distribution D10-D90: 2.4 μm, D50: 1.2 μm) 54.5 parts by mass, and titanium dioxide particles (trade name: Typaque CR-60, manufactured by Ishihara Sangyo Co., Ltd.) 0 A printing paper of Example 6 was obtained in the same manner as in Example 1, except that the resin composition (3) mixed with 5 parts by mass was used.

(Example 7)
A printing paper of Example 7 was obtained in the same manner as in Example 1, except that the resin composition (1) in Example 1 was replaced with the resin composition (8) to form a porous layer.
Resin composition (8) comprises 42.5 parts by mass of polypropylene resin (trade name: Novatec PP MA3, manufactured by Japan Polypropylene Corporation) and 1 part by mass of maleic anhydride-modified polypropylene resin (trade name: Modic P928, manufactured by Mitsubishi Chemical Corporation). , Soft polypropylene (trade name: Toughmer PN2060, manufactured by Mitsui Chemicals, melting energy 10 J / g) 3.5 parts by mass, light calcium carbonate particles surface-treated with fatty acid (particle size distribution D10-D90: 0.6 μm, D50: 0.5 μm) and 0.5 parts by mass of titanium dioxide particles (trade name: Typaque CR-60, manufactured by Ishihara Sangyo Co., Ltd.).

(Example 8)
A printing paper of Example 8 was obtained in the same manner as in Example 1, except that the resin composition (1) was replaced with the resin composition (9) to form a porous layer.
Resin composition (9) comprises 38 parts by mass of polypropylene resin (trade name: Novatec PP MA3, manufactured by Japan Polypropylene Corporation), 1 part by mass of maleic anhydride-modified polypropylene resin (trade name: Modic P928, manufactured by Mitsubishi Chemical Corporation), soft Polypropylene (trade name: Toughmer PN2060, manufactured by Mitsui Chemicals, Inc.) 8 parts by mass, light calcium carbonate particles surface-treated with fatty acid (particle size distribution D10-D90: 0.6 μm, D50: 0.5 μm) 52.5 parts by mass, And titanium dioxide particles (trade name: Typaque CR-60, manufactured by Ishihara Sangyo Co., Ltd.) 0.5 parts by mass.

(Example 9)
A printing paper of Example 9 was obtained in the same manner as in Example 1, except that the resin composition (1) in Example 1 was replaced with the resin composition (10) to form a porous layer.
Resin composition (10) comprises 36 parts by mass of polypropylene resin (trade name: Novatec PP MA3, manufactured by Japan Polypropylene Corporation), 1 part by mass of maleic anhydride-modified polypropylene resin (trade name: Modic P928, manufactured by Mitsubishi Chemical Corporation), soft 10 parts by mass of polypropylene (trade name: Toughmer PN2060, manufactured by Mitsui Chemicals, Inc.), 52.5 parts by mass of light calcium carbonate particles surface-treated with fatty acid (particle size distribution D10-D90: 0.6 μm, D50: 0.5 μm), And titanium dioxide particles (trade name: Typaque CR-60, manufactured by Ishihara Sangyo Co., Ltd.) 0.5 parts by mass.

(Example 10)
A printing paper of Example 10 was obtained in the same manner as in Example 1, except that the intermediate layer was formed by replacing the resin composition (4) with the resin composition (11).
Resin composition (11) comprises 48.5 parts by mass of polypropylene resin (trade name: Novatec PP MA3, manufactured by Nippon Polypropylene Corporation) and 48.5 parts by mass of ethylene-cyclic olefin copolymer (trade name: APEL 6011T, manufactured by Mitsui Chemicals, Inc.). 5 parts by mass, and 3 parts by mass of calcium carbonate particles (trade name: Cube80KAS, manufactured by Maruo Calcium Co., Ltd., average particle size 8 μm).

(Example 11)
A printing paper of Example 11 was obtained in the same manner as in Example 1, except that the intermediate layer was formed by replacing the resin composition (4) with the resin composition (12).
The resin composition (12) comprises 45 parts by mass of a polypropylene resin (trade name: Novatec PP MA3, manufactured by Nippon Polypropylene Corporation), 45 parts by mass of an ethylene-cyclic olefin copolymer (trade name: APEL 6011T, manufactured by Mitsui Chemicals, Inc.), and 10 parts by mass of calcium carbonate particles (trade name: Cube80KAS, manufactured by Maruo Calcium Co., Ltd.).

(Example 12)
A printing paper of Example 12 was obtained in the same manner as in Example 11, except that the thickness of the intermediate layer was changed to 6 μm.

(Example 13)
A printing paper of Example 13 was obtained in the same manner as in Example 1, except that the intermediate layer was formed by replacing the resin composition (4) with the resin composition (13).
The resin composition (13) comprises 40 parts by mass of a polypropylene resin (trade name: Novatec PP MA3, manufactured by Nippon Polypropylene Corporation), 40 parts by mass of an ethylene-cyclic olefin copolymer (trade name: APEL 6011T, manufactured by Mitsui Chemicals, Inc.), and 20 parts by mass of calcium carbonate particles (trade name: Cube80KAS, manufactured by Maruo Calcium Co., Ltd.).

(Example 14)
A printing paper of Example 14 was obtained in the same manner as in Example 1, except that the intermediate layer was formed by replacing the resin composition (4) with the resin composition (14).
The resin composition (14) comprises 45 parts by mass of a polypropylene resin (trade name: Novatec PP MA3, manufactured by Nippon Polypropylene Corporation), 45 parts by mass of an ethylene-cyclic olefin copolymer (trade name: APEL 6011T, manufactured by Mitsui Chemicals, Inc.), and 10 parts by mass of heavy calcium carbonate (trade name: Softon 1800, manufactured by Bihoku Funka Kogyo Co., Ltd.).

(Example 15)
A printing paper of Example 15 was obtained in the same manner as in Example 1, except that the intermediate layer was formed by replacing the resin composition (4) with the resin composition (15).
The resin composition (15) comprises 45 parts by mass of a polypropylene resin (trade name: Novatec PP MA3, manufactured by Nippon Polypropylene Corporation), 45 parts by mass of an ethylene-cyclic olefin copolymer (trade name: APEL 6011T, manufactured by Mitsui Chemicals, Inc.), and 10 parts by mass of heavy calcium carbonate (trade name: R50A, manufactured by Maruo Calcium Co., Ltd., average particle size: 15 μm).

(Comparative Examples 1 and 2)
Printing papers of Comparative Examples 1 and 2 were obtained in the same manner as in Example 1 except that Coating Liquids 3 and 4 were used as the coating liquids in step (VI) of Example 1. rice field.

(Comparative Example 3)
Instead of the resin composition (1) of Example 1, 51.5 parts by mass of propylene homopolymer (manufactured by Japan Polypropylene Corporation, trade name Novatec PP MA-3), high-density polyethylene (manufactured by Japan Polychem Co., Ltd., trade name HJ580 density 0.950 g/cm ³ ) 3.5 parts by mass, heavy calcium carbonate (particle size distribution D10-D90: 5.1 μm, D50: 1.5 μm) 42 parts by mass, titanium dioxide particles (trade name: Typaque CR- 60, manufactured by Ishihara Sangyo Co., Ltd.) was mixed with a resin composition (6) consisting of 3 parts by mass in a high-speed mixer, and then using a twin-screw kneading extruder with the cylinder temperature set to 240 ° C., while degassing through a vent hole. A printing paper of Comparative Example 3 was obtained in the same procedure as in Example 1 except that the melt-kneading was performed at a rotation speed of 600 rpm. The printing paper of Comparative Example 3 has a five-layer structure (number of stretching axes of each layer: uniaxial stretching/uniaxial stretching/biaxial stretching/uniaxial stretching/uniaxial stretching), total thickness: 130 μm (thickness of each layer: (6 )/(4)/(5)/(4)/(6)=8 μm/3 μm/108 μm/3 μm/8 μm)).

(Comparative Example 4)
Instead of the resin composition (1) of Example 1, 46 parts by mass of a polypropylene resin (trade name: Novatec PP MA3, manufactured by Nippon Polypro Co., Ltd.), maleic anhydride-modified polypropylene resin (trade name: Modic P928, manufactured by Mitsubishi Chemical Corporation) ) 1 part by mass, heavy calcium carbonate (particle size distribution D10-D90: 5.1 μm, D50: 1.5 μm) 52.5 parts by mass, and titanium dioxide particles (trade name: Typaque CR-60, manufactured by Ishihara Co.) 0 A printing paper of Comparative Example 4 was obtained in the same manner as in Example 1, except that resin composition (7) mixed with 5 parts by mass was melted and kneaded at a rotational speed of 600 rpm while degassing through a vent hole. rice field. The printing paper of Comparative Example 4 has a five-layer structure (the number of stretching axes of each layer: uniaxial stretching/uniaxial stretching/biaxial stretching/uniaxial stretching/uniaxial stretching, total thickness: 130 μm (thickness of each layer: (6) /(4)/(5)/(4)/(6)=8 μm/3 μm/108 μm/3 μm/8 μm)).

(Comparative Example 5)
In Example 1, the amount of resin discharged for each layer was changed, and the total thickness was 130 μm (thickness of each layer: (1)/(4)/(5)/(4)/(1)=3 μm/3 μm/118 μm/ A printing paper of Comparative Example 5 was obtained in the same procedure as in Example 1, except that the thickness was changed to 3 μm/3 μm.

Tables 2A and 2B show the composition of the resin composition.

Table 3 shows the composition of the printing paper of each example and each comparative example. Each printing paper has a layer structure of antistatic layer/porous layer/intermediate layer/base material layer/intermediate layer/porous layer/antistatic layer. Since the composition of the antistatic layer/porous layer/intermediate layer is the same on the surface side, Table 3 shows only the composition of the antistatic layer/porous layer/intermediate layer provided on one side of the base layer. .

Various measurements were performed on the printing paper of each example and comparative example under the following measurement conditions.
<Porosity>
The porosity of the porous layer was obtained from the ratio of the area occupied by the pores in a certain region of the cross section of the printing paper observed with an electron microscope. Specifically, an arbitrary part of the printed paper to be measured is cut, embedded in epoxy resin and solidified, then cut perpendicular to the surface direction of the printed paper to be measured using a microtome, and the cut It was pasted on the observation sample table so that the surface was the observation surface. Vapor-deposit gold or gold-palladium on the observation surface, observe the pores of the printing paper at any magnification that is easy to observe with an electron microscope (for example, magnification of 500 times to 3000 times), and image the observed area. imported as data. The obtained image data was subjected to image processing by an image analyzer, the porous layer was determined from the boundary between layers, and the area ratio (%) of the pore portion in a given region of the porous layer was obtained. The porosity (%) was determined by averaging the measured values obtained at arbitrary 10 or more observation points.

<Surface resistivity>
In accordance with JIS-K-6911:1995, after placing the printing paper in an atmosphere with a temperature of 23°C and a relative humidity of 50RH% for 2 hours or more to adjust the condition to a constant value, the surface resistivity value of the surface on the antistatic layer side (logΩ) was measured using an insulation resistance meter (model number: DSM-8103, manufactured by Toa Denpa Kogyo Co., Ltd.).

<Oil absorption>
A square of 100 mm in length and width was cut from the printing paper to prepare a sample, and the mass of the sample was measured. Mineral oil (manufactured by Wako Pure Chemical Industries, Ltd.; density 0.84) was placed in a container, the liquid temperature was adjusted to 20°C, and only one side of the cut sample was floated on the mineral oil to absorb the oil. After floating for 5 seconds, the excess mineral oil adhering to the oil-absorbed surface was sufficiently wiped off. After wiping off, the mass of the sample was measured again, and the oil absorption was determined from the oil-absorbed area, that is, the area of the entire cut sample, using the following formula.
Oil absorption (g/m ² ) =
{(mass after oil absorption (g))-(mass before oil absorption (g))}/(oil-absorbed area (m ² ))

<Atomic concentration ratio of nitrogen atoms on the surface>
The ratio (%) of the atomic concentration (atom%) of nitrogen atoms to the total atomic concentration (atom%) of carbon atoms and nitrogen atoms on the surface of the printing paper was measured by XPS under the following measurement conditions.
Device: K-Alpha
Excitation X-ray: AlKα
X-ray output: 72W
X-ray diameter: 400 μm
Photoelectron escape angle: 45°

Specifically, the measurement is performed by narrow scan, and the ratio of the peak area of the N1s peak of the nitrogen atom to the sum of the peak area of the C1s peak of the carbon atom and the peak area of the N1s peak of the nitrogen atom. It was obtained as a concentration ratio.

(evaluation)
Printing was performed on the printing paper of each example and comparative example by the following method, and the effect of suppressing chemical ghosts, ink drying property and edge picking were evaluated for the resulting prints.

<Effect of suppressing chemical ghost>
Two sheets of printing paper were prepared. On one side of one of the printing papers, printing was performed using the following printing machine and ink so that the ink transfer amount was 1.5 g/m ² . For printing, a printing roll that prints only on both ends in the width direction of the printing paper was used.
Printer: RI tester (manufactured by Kokubo Seimitsu Co., Ltd.)
Ink: Fusion-G MK black ink (manufactured by DIC, oxidation polymerization type oil-based ink for pulp paper (solvent 5-15%))

After placing the obtained printed matter A on the tray with the printed surface facing upward, another sheet of printing paper was immediately placed on the printed surface of the printed matter A, and from this printing paper, a sheet of the same size as the paper size and a mass was placed. A 1 kg weight was placed on it. After placing the vat in a room with a temperature of 35 ° C and a relative humidity of 80 RH% for 72 hours, remove the weight and print on the bottom surface of the topmost printing paper (the surface that was superimposed on the printed surface of printed matter A). dried. The second sheet was printed in the same manner as printed matter A, except that a printing roll that prints across the entire width was used.

FIG. 2 shows the printed surface A1 of the printed material A and the printed surface B2 of the printed material B. FIG.
As shown in FIG. 2, the print surface A1 of the printed matter A includes two print areas Ra located on both widthwise end sides with an interval of 2 cm therebetween. The size from one end to the other end in the width direction of each print area Ra is 24 cm. On the other hand, the print surface B1 of the printed matter B includes one print region Rb with a size of 24 cm in the width direction. The positions of both ends in the width direction of the print area Rb are the same as the positions of both ends in the width direction of each print area Ra.

Of the printed regions Rb of the printed matter B, the ink density D1 of the printed region Rb1 that was in contact with each printed region Ra of the printed matter A and the ink density D2 of the printed region Rb2 that was not in contact were measured. At the time of measurement, the ink densities D1 and D2 were measured at positions 5 to 10 mm away from the boundary between the printed area Rb1 that was in contact with the printed area Ra of the printed material A and the printed area Rb2 that was not in contact with the printed area Ra of the printed material B. did. The ink density was measured using X-Rite 530 (manufactured by X-Rite Co., Ltd.). A density difference Δ between the measured ink densities D1 and D2 was obtained by the following formula.
Density difference Δ=D2-D1

Based on the determined density difference Δ, the chemical ghost suppressing effect was evaluated according to the following criteria.
⊚: Δ≦0.05, and the ink is well transferred. No difference can be confirmed visually, and the chemical ghost is sufficiently suppressed.
◯: 0.05<Δ≦0.2, the ink is well transferred and the chemical ghost is suppressed ×: 0.2<Δ, the ink is not sufficiently transferred , chemical ghost suppression is not sufficient

<Drying property of ink>
Chrysanthemum 4-cut extension 4-color offset printing machine (equipment name: Ryobi 524GX, manufactured by Ryobi MHI Graphic Technology) and oxidation polymerization type oil-based offset ink (trade name: Fusion-G MK black, indigo, red, transparent yellow, DIC) (manufacturer), oil-based offset printing was performed on the printing paper of each example and comparative example. The used oil-based offset ink is commercially available as an ink for pulp paper. The amount of solvent in each oil-based offset ink is 5 to 15% for black, 15 to 25% for indigo, 15 to 25% for crimson, and 20 to 30% for transparent yellow.

The printing conditions were PS plate (trade name: XP-F, manufactured by Fujifilm), blanket (trade name: D-3000, manufactured by T&K TOKA), powder (trade name: Nikkalico AS-100S, manufactured by Nikka). ) and dampening water (containing 1.0% H solution (trade name: Astromark 3, manufactured by Nikken Kagaku Kenkyusho) and 5.0% IPA, water temperature 10°C).
In addition, as printing conditions, the temperature in the printing chamber is adjusted to 20 to 25° C., the relative humidity is adjusted to 40 to 60 RH%, the order of colors is black, indigo, red, and transparent yellow, and the printing speed is 8000 sheets / hour. and At this time, a pattern was printed in which a solid printed portion of each color of black, indigo, red, and transparent yellow and a 400% solid printed portion printed in all colors of black, indigo, red, and transparent yellow were arranged in the printing flow direction. .
The amount of ink transfer was adjusted so that the densities of black, indigo, crimson, and transparent yellow single-color solid areas were 1.85, 1.55, 1.45, and 1.00, respectively, and the dampening water did not cause scumming. More than 200 sheets were printed under the condition that the level was reduced as much as possible, and after printing, they were stacked one after another from the bottom and stored.

Every hour after printing, ink drying property was evaluated as follows for the printed matter extracted from the lower portion of about 50 sheets from the top of the piled printed matter.
○: The 400% solid print area was set and dried within 6 hours △: The 400% solid print area was set and dried within 12 hours over 6 hours ×: The 400% solid print area was set and dried within 12 hours didn't

<Edge picking>
Oil-based offset printing was performed on the printing paper of each example and comparative example under the same printing conditions as in <Drying property of ink>. Edge picking was evaluated as follows for the printed matter extracted from the portion about 50 sheets below the upper portion of the stacked printed matter.
A: There is no blank part at the end of the 400% solid printing part, and the pattern is the same as the printing plate. Blank parts are scattered at the edge of the printed part ×: Blank parts are continuously generated at the edge of the 400% solid printed part

Table 4 shows the evaluation results. Note that "-" in Table 4 indicates that the sheets stuck to each other and the effect of suppressing chemical ghost could not be evaluated.

As shown in Table 4, all of the printing papers of Examples 1 to 6 and 14 are excellent in ink drying properties, and chemical ghosts are effectively suppressed. Further, the printing papers of Examples 7 to 9 have less edge picking, and the printing papers of Examples 10 to 13 and 15 are more excellent in the effect of suppressing chemical ghosts.

On the other hand, in the printing papers of Comparative Examples 1 to 5, the ink was not sufficiently dried, chemical ghosts were generated, and density differences occurred. Further, according to Comparative Example 4, even if the porosity is high, the oil absorption is not sufficient, so that the drying of the ink is insufficient.

This application claims priority based on Japanese Patent Application No. 2019-70505, which is a Japanese patent application filed on April 2, 2019, and incorporates all descriptions of the Japanese patent application.

DESCRIPTION OF SYMBOLS 10... Printing paper 1... Thermoplastic resin film 2, 2a... Porous layer 3, 3a... Antistatic layer 4... Base material layer 5, 5a... middle layer

Claims (11)

A printing paper having a thermoplastic resin film including a porous layer and an antistatic layer provided on the porous layer of the thermoplastic resin film,
The oil absorption of the printing paper is 1.0 g/m ² or more,
When the surface of the printing paper on the antistatic layer side is measured by X-ray photoelectron spectroscopy, the ratio of the atomic concentration of nitrogen atoms to the total atomic concentration of nitrogen atoms and carbon atoms is 3.0% or less. ,
printing paper. The antistatic layer contains a nitrogen-containing compound,
the nitrogen-containing compound comprises a quaternary nitrogen-containing compound;
The content of the quaternary nitrogen-containing compound in the nitrogen-containing compound is 50% by mass or more,
The printing paper according to claim 1. the nitrogen-containing compound comprises a primary nitrogen-containing compound or a secondary nitrogen-containing compound;
The content of the primary nitrogen-containing compound and the secondary nitrogen-containing compound in the nitrogen-containing compound is 20% by mass or less,
The printing paper according to claim 1. The antistatic layer contains a nitrogen-containing compound and a cross-linking agent,
wherein the nitrogen-containing compound comprises a primary nitrogen-containing compound or a secondary nitrogen-containing compound;
The printing paper according to claim 1. A printing paper having a thermoplastic resin film including a porous layer and an antistatic layer provided on the porous layer of the thermoplastic resin film,
The oil absorption of the printing paper is 1.0 g/m ² or more,
The antistatic layer contains a nitrogen-containing compound, and the total content of primary or secondary nitrogen in the total nitrogen contained in the nitrogen-containing compound is 10% or less.
printing paper. The porous layer contains a thermoplastic resin and a filler,
The particle size distribution D10-D90 of the filler is 4 μm or less,
The printing paper according to any one of claims 1-5. The porous layer contains a soft polyolefin resin as the thermoplastic resin,
The printing paper according to any one of claims 1-6. having an intermediate layer between the substrate layer and the porous layer;
wherein the intermediate layer contains a filler having an average particle size larger than the thickness of the intermediate layer;
The printing paper according to any one of claims 1-7. The porous layer is a stretched film stretched in at least one direction,
The printing paper according to any one of claims 1-8. The printing paper according to any one of claims 1 to 9;
a printing layer provided on the printing paper;
printed matter. wherein the printed layer is formed of an oxidative polymerization ink;
The printed matter according to claim 10.

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