Recording paper

Abstract

The present invention relates to a recording sheet having a coating layer, a print receptive layer, and a liquid absorbing layer in this order, wherein: the coating layer includes an aqueous binder as a resin component; both the print receptive layer and the liquid absorbing layer are porous layers containing a thermoplastic resin; a surface adjacent to the print receptive layer has a liquid absorption rate of 5 to 25 cc / m2 · 0.5 s and a liquid absorption amount of 10 cc / m2 or more; and the coating layer contains an inorganic filler in the amount of 9 parts by mass or less relative to 100 parts by mass of the aqueous binder.

Description

[Technical Field]

[0001] The present invention relates to a recording paper. [Background technology]

[0002] In recent years, inkjet printers have become capable of producing images that are comparable to those produced by multicolor offset printing or color electrophotography. In addition, inkjet printers have become widely used due to their lower running costs for color printing compared to electrophotography printers. Among these, inkjet printers that use water-based inks, which are less susceptible to environmental and safety issues than oil-based inks, have become mainstream.

[0003] As a result, the use of inkjet recording paper has expanded to include posters and drafting applications, which has led to higher demands for recording paper and recording inks with higher print quality and abrasion resistance than ever before.

[0004] Furthermore, in fields such as commercial printing, so-called on-demand printing methods have been introduced, in which variable information is digitized and printed at high speed, and inkjet printers employing on-demand printing methods have also appeared. Such on-demand printing methods are suitable for printing small runs because they allow information to be printed directly onto media such as paper without plate-making. Recently, with the expansion of applications due to significant advances in the speed and resolution of devices, there has been a strong demand for improved drying properties for recording paper. For example, Patent Document 1 proposes a porous resin film for printing with an inkjet printer using water-based ink, in which the film uses calcium carbonate powder treated with a surface treatment agent having an HLB value of 5 to 100, and has a liquid absorption capacity of a specific value or more.

[0005] On the other hand, inkjet printers that use solvent-based inks are also popular due to their excellent water resistance and ink fixability, etc. Various studies have been conducted on printing with inkjet printers that use solvent-based inks, for example, in Patent Documents 2 and 3.

[0006] For example, Patent Document 2 describes an inkjet recording medium comprising an ink receiving layer provided on a support, the ink receiving layer containing at least one pigment having an average particle size of 2 to 17 μm and selected from amorphous silica, alumina, alumina hydrate, aluminosilicate, and hydrotalcite group minerals, and an adhesive, wherein the adhesive contains a vinyl chloride-vinyl acetate copolymer.

[0007] Patent Document 3 describes a semi-gloss oil-based inkjet recording sheet in which an oil-based ink-receptive glossy layer made primarily of a vinyl chloride-acrylic copolymer with a glass transition temperature of 20 to 55°C is formed on at least one surface of a support, and the surface of the oil-based ink-receptive glossy layer has a 75° specular gloss of 20 to 70% as specified in JIS P 8142:2005 "Test method for 75° specular gloss" and further the 75° specular gloss of the area where an image is printed with oil-based ink is equal to or greater than the 75° specular gloss of a blank area. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2001-164017 [Patent Document 2] Japanese Patent Publication No. 2001-270238 [Patent Document 3] Japanese Patent Publication No. 2010-234677 Summary of the Invention [Problem to be solved by the invention]

[0009] However, according to the investigations of the present inventors, it has been found that even if the liquid absorption volume is relatively large, if the liquid absorption speed (ink absorption speed) is relatively slow, sufficient drying properties may not be obtained. In addition, from the viewpoint of improving the drying properties of ink during printing, it is preferable that the surface on the print-receiving layer side has a high liquid absorption rate, but it has also been found that if the liquid absorption rate is too fast, the ink may become discolored or granular patterns may occur due to bubbles spraying from the openings on the surface on the print-receiving layer side.

[0010] Furthermore, the ink-receiving layer in Patent Document 2 is a coating layer containing a pigment, and although a pigment coating such as that in Patent Document 2 provides a certain level of ink drying property, it may be prone to adhesion of water and dirt, and the strength of the receiving layer may be relatively low, which may also result in a decrease in print quality such as abrasion resistance.

[0011] In a receiving layer containing a vinyl chloride copolymer as in Patent Document 3, printing is performed by the vinyl chloride copolymer being eroded by the solvent absorbed from the ink and fixing the pigment, which can cause waviness and blocking due to the solvent, and can also have an adverse effect on weather resistance.

[0012] Therefore, an object of the present invention is to provide a recording paper that has excellent print quality and drying properties, and also has excellent weather resistance, so that printed matter does not require water-resistant or stain-resistant treatment even when exposed outdoors for long periods of time. [Means for solving the problem]

[0013] That is, the present invention relates to the following 1 to 8. 1. A recording paper having a coating layer, a print-receiving layer, and a liquid-absorbing layer in this order, the coating layer contains an aqueous binder as a resin component, the print-receiving layer and the liquid-absorbing layer are both porous layers containing a thermoplastic resin, The liquid absorption rate on the surface on the print-receiving layer side is 5 to 25 cc / m 2 0.5s, Absorption capacity: 10cc / m 2 That's all, The recording paper has an inorganic filler content of 9 parts by mass or less per 100 parts by mass of the aqueous binder in the coating layer. 2. The recording paper according to 1 above, wherein the print-receiving layer has a porosity of 30 to 50%, and the liquid-absorbing layer has a porosity of 40 to 60%. 3. The recording paper according to 1 or 2 above, wherein the print-receiving layer and the liquid-absorbing layer are both stretched layers containing a filler. 4. The recording paper according to any one of 1 to 3 above, wherein the print-receiving layer has a filler content of 45 to 75% by mass. 5. The recording paper according to any one of 1 to 4 above, wherein the print-receiving layer contains a hydrophobized surface-treated filler as a filler. 6. The recording paper according to any one of 1 to 5 above, wherein the print-receiving layer has an average pore size of 0.5 to 20 μm. 7. The recording paper according to any one of 1 to 6 above, wherein the content of the resin component in the coating layer exceeds 80% by mass. 8. The coating amount of the coating layer after drying is 0.05 to 5 g / m 2 8. The recording sheet according to any one of 1 to 7 above, wherein [Effects of the Invention]

[0014] According to the present invention, it is possible to provide a recording paper that is excellent in print quality, drying property and weather resistance. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a cross-sectional view showing an example of a recording sheet according to this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, recording sheets according to embodiments of the present invention will be described in detail, but the present invention is not limited thereto. In the following description, the term "(meth)acrylic" refers to both acrylic and methacrylic. Similarly, the term "(meth)acrylate" refers to both acrylate and methacrylate.

[0017] [Recording paper] The recording paper according to this embodiment is a recording paper having a coating layer, a print-receiving layer, and a liquid-absorbing layer in this order, the coating layer containing an aqueous binder as a resin component, the print-receiving layer and the liquid-absorbing layer both being porous layers containing a thermoplastic resin, and the liquid absorption rate on the surface on the print-receiving layer side is 5 to 25 cc / m 2 0.5s, liquid absorption rate 10cc / m 2 The content of the inorganic filler in the coating layer is 9 parts by mass or less relative to 100 parts by mass of the aqueous binder.

[0018] FIG. 1 is a cross-sectional view showing an example of a recording paper according to the present embodiment. In FIG. 1, the recording paper 1 has a coating layer 13, a print-receiving layer 12, and a liquid-absorbent layer 11, in this order. The liquid-absorbent layer 11 is preferably provided in contact with the print-receiving layer 12. As will be described later, the recording paper according to the present embodiment preferably also has a support layer 10 on the side of the liquid-absorbent layer 11 opposite the print-receiving layer 12. Furthermore, a backing layer 9 is preferably further provided on the surface of the liquid-absorbent layer 11 opposite the print-receiving layer 12. FIG. 1 is a diagram illustrating an example of a recording paper 1 that has a coating layer 13, a print-receiving layer 12, a liquid-absorbent layer 11, a support layer 10, and a backing layer 9. In this specification, the "surface on the print-receiving layer side" of the recording paper refers to the surface on the print-receiving layer side of the recording paper relative to the liquid-absorbent layer. In other words, this corresponds to the surface on the coating layer side of the recording paper.

[0019] The recording paper according to this embodiment has a liquid absorption rate of 5 to 25 cc / m on the surface on the print receiving layer side. 2 0.5s. The absorption rate is 5cc / m 2 0.5s or more, 7cc / m 2 0.5s or more is preferable, 10cc / m 2 More than 0.5s is preferable, 12cc / m 2 0.5s or more is more preferable, 13cc / m 2A liquid absorption rate of 0.5 s or more is particularly preferred. By having a liquid absorption rate of this value or more, the ink drying property during printing can be improved, and furthermore, bleeding of the print can be suppressed. On the other hand, a liquid absorption rate of 25 cc / m or more is preferred. 2 0.5s or less, 20cc / m 2 A liquid absorption rate of 0.5 seconds or less is preferable. By keeping the liquid absorption rate at or below this value, it is possible to prevent ink color settling and the occurrence of granular patterns due to bubbles spraying from the openings on the surface of the print-receiving layer side, and to improve print quality such as print density. The liquid absorption rate on the surface of the print-receiving layer side is the amount of liquid transferred measured in accordance with the Bristow method for liquid absorbency testing described in Japan Tappi No. 51:2000, and means the amount of liquid absorbed per unit area 500 milliseconds after the test solution is dropped.

[0020] The liquid absorption capacity of the recording paper according to this embodiment is 10 cc / m 2 or more, 13cc / m 2 More than 15cc / m is preferable. 2 More than 16cc / m is more preferable. 2 More preferably, 18cc / m 2 The above-mentioned liquid absorption amount is particularly preferable. By having the liquid absorption amount of the above-mentioned value or more, the drying property can be improved. On the other hand, from the viewpoint of improving productivity and suppressing dry down, the liquid absorption amount is preferably 100 cc / m 2 Less than 90cc / m is preferable 2 The following is more preferred: The amount of liquid absorbed by the recording paper refers to the value measured for the amount of liquid absorbed from the surface on the print-receiving layer side, and is the Cobb water absorbency value measured in accordance with the provisions of JIS P8140: 1998. However, diethylene glycol ethyl methyl ether was used as the test solvent instead of water, and the contact time was 60 seconds.

[0021] In the recording paper according to this embodiment, the liquid absorption rate on the surface on the print receiving layer side is 5 to 25 cc / m 2 0.5s and liquid absorption of 10cc / m 2That's all. That is, in this embodiment, it is preferable that both the liquid absorption speed and the liquid absorption amount are within the above-mentioned ranges. As described above, the inventors have discovered that even if the liquid absorption volume is relatively large, sufficient drying may not be achieved if the liquid absorption speed is relatively slow. In addition, from the perspective of improving ink drying during printing, a high liquid absorption speed on the surface facing the print-receiving layer is preferable, but it has also been discovered that an excessively fast liquid absorption speed may cause ink discoloration or granular patterns due to bubbles spraying from the openings on the surface facing the print-receiving layer. In contrast, the present invention has discovered that recording paper with good print quality, drying properties, and weather resistance can be obtained by having a print-receiving layer, a liquid-absorbing layer, and a specified coating layer, and by having a liquid absorption speed on the surface facing the print-receiving layer of the recording paper within a specific range and a liquid absorption amount equal to or greater than a specific value.

[0022] Both the print-receiving layer and the liquid-absorbent layer are preferably stretched layers containing a filler. For example, by co-extruding the print-receiving layer and the liquid-absorbent layer and then co-stretching them, or by extrusion-laminating the print-receiving layer onto the liquid-absorbent layer and then co-stretching them, it is possible to simplify the production process and reduce production costs, which is preferable.

[0023] In addition, in general coated printing paper, a coating layer containing a pigment and a binder is provided on the surface of a substrate such as paper. To provide appropriate ink receptivity, calcium carbonate or kaolin is typically used as the pigment. However, such coating layers contain a large amount of pigment, making them brittle and prone to cracking when bent. Furthermore, the pigment components can easily cause a loss of surface gloss. In contrast, when the print-receiving layer is a layer made porous by stretching, it is easier to make it sufficiently porous with a smaller amount of filler than the aforementioned coating layer, making it easier to achieve the desired liquid absorption rate and amount. Furthermore, the porous layer obtained in this manner is resistant to bending. Furthermore, a higher gloss is more likely to be obtained. When the print-receiving layer is formed by stretching, it is preferable to use the materials described below, since this makes it easier to achieve the various physical properties described above. In addition, preferred embodiments of the liquid-absorbing layer will also be described below.

[0024] (coat layer) The coating layer contains an aqueous binder as a resin component. By including an aqueous binder as a resin component, the coating layer can improve printability, such as adhesion to ink. Here, the aqueous binder excludes the antistatic agent described below. Examples of aqueous binders include water-soluble resins and water-dispersible resins (aqueous resin emulsions). By including a water-dispersible resin in the coating layer, the cohesive strength of the coating layer can be increased, improving abrasion resistance. Furthermore, the pigment in the ink tends to adhere more easily to the recording paper surface, thereby improving ink fixability. Furthermore, by including a water-dispersible resin in the coating layer, the liquid absorption rate can be adjusted to be higher than that of other aqueous binders, such as water-soluble resins. From the viewpoint of improving adhesion to ink, the aqueous binder is preferably an ionic binder, and more preferably a cationic binder. When the aqueous binder is a cationic binder, the cation equivalent is preferably 5 meq / g or less, more preferably 4 meq / g or less, and even more preferably 3 meq / g or less. The coating layer can be formed by preparing a coating liquid for forming the coating layer containing an aqueous binder and applying the coating liquid to the surface of the laminated film.

[0025] From the viewpoint of improving smoothness, the content of the resin component in the coating layer is preferably more than 80% by mass, more preferably 85% by mass or more, even more preferably 90% by mass or more, and may be 100% by mass. Note that, when the coating layer contains resin components as antistatic agents in addition to the aqueous binder, the content of the resin component in the coating layer refers to the solid content ratio of the total of these resin components in the coating layer. From the viewpoint of suppressing bleeding of printing, the coating layer may consist of only an aqueous binder, or may consist of only an aqueous binder, an inorganic filler, and an auxiliary component described below, or may consist of only an aqueous binder and an auxiliary component.

[0026] The dry solid content (coating amount after drying) of the coating layer is preferably 0.05 g / m from the viewpoint of improving adhesion to ink. 2 More preferably, 0.08 g / m 2 More preferably, 0.1 g / m 2 From the viewpoint of promoting ink penetration into the porous layer and obtaining good drying properties and image clarity, the dry solid content (coating amount after drying) of the coating layer is preferably 10 g / m 2 Less than 5g / m, more preferably 2 More preferably, 2 g / m or less 2 or less, even more preferably 0.5 g / m 2 Below 0.25 g / m, particularly preferably 2 The following is the result.

[0027] Examples of the water-soluble resin include urethane-based resins, (meth)acrylic acid-based resins, and ethyleneimine-based polymers. Examples of aqueous resin emulsions include urethane-based resin emulsions, (meth)acrylic acid-based resin emulsions, and olefin-based resin emulsions. When the coating layer contains a water-soluble resin emulsion, the ink fixation property and abrasion resistance can be further improved. These may be used alone or in combination of two or more.

[0028] The (meth)acrylic acid-based resin more preferably has an amino group, a quaternary ammonium salt structure or a phosphonium salt structure, and even more preferably has an amino group or a quaternary ammonium salt structure.

[0029] When the coating layer contains a water-soluble resin, the content (solid content) of the water-soluble resin in the coating layer is preferably 10% by mass or more, more preferably 20% by mass or more, even more preferably 25% by mass or more, and particularly preferably 30% by mass or more, from the viewpoint of improving adhesion to ink. From the viewpoint of promoting penetration of ink into the porous layer (print-receiving layer and liquid-absorbing layer) and obtaining drying properties and image clarity, the content (solid content) of the water-soluble resin in the coating layer can be 100% by mass or less, 95% by mass or less, or 91% by mass or less.

[0030] Examples of ethyleneimine-based polymers include polyethyleneimine, poly(ethyleneimine-urea), ethyleneimine adducts of polyamine polyamides, and modified products or hydroxides thereof. Examples of modified products include alkyl-modified products, cycloalkyl-modified products, aryl-modified products, allyl-modified products, aralkyl-modified products, benzyl-modified products, cyclopentyl-modified products, alicyclic hydrocarbon-modified products, and glycidol-modified products. The coating layer may further contain an ethyleneimine-based polymer. When the coating layer contains an ethyleneimine-based polymer, it has strong affinity with various printing inks, particularly ultraviolet-curable inks, and therefore its printability is likely to be improved.

[0031] From the viewpoint of improving adhesion to ink, the content of the ethyleneimine polymer in the coating layer is preferably 10% by mass or more, more preferably 20% by mass or more, and even more preferably 25% by mass or more. The upper limit of the content is not particularly limited, but may be 100% by mass or less, 90% by mass or less, or 80% by mass or less.

[0032] When the coating layer contains a water-dispersible resin, the content (solid content) of the water-dispersible resin in the coating layer is preferably 20% by mass or more, more preferably 30% by mass or more, even more preferably 40% by mass or more, still more preferably 60% by mass or more, and particularly preferably 80% by mass or more, from the viewpoint of ink fixability. The upper limit of the content may be 100% by mass.

[0033] The average particle size of the water-dispersible resin in the coating layer is preferably 5 μm or less, more preferably 3 μm or less, even more preferably 1 μm or less, still more preferably 0.5 μm or less, and particularly preferably 0.2 μm or less, from the viewpoint of promoting penetration of the ink into the porous layers (print-receiving layer and liquid-absorbing layer) and obtaining good drying properties and image clarity.

[0034] The minimum film forming temperature (MFT) of the water-dispersible resin is preferably 100°C or lower. By setting the MFT to 100°C or lower, the film-forming properties of the coating layer, particularly at room temperature, are improved, making it easier to prevent particles from falling out of the porous material. The MFT is preferably 80°C or lower, more preferably 40°C or lower, and even more preferably 10°C or lower. There is no particular lower limit, but it is usually -20°C or higher.

[0035] The coating layer may contain an inorganic filler, but the inorganic filler content in the coating layer is 9 parts by mass or less per 100 parts by mass of the aqueous binder. That is, the coating layer does not contain an inorganic filler, or if it does contain an inorganic filler, the content is 9 parts by mass or less. If the inorganic filler content is 9 parts by mass or less per 100 parts by mass of the aqueous binder, the pores open on the surface of the print-receiving layer are less likely to be filled, allowing the printing ink to more easily penetrate into the porous layer, resulting in faster drying and clearer images. Furthermore, it is possible to effectively prevent staining of the recording paper and peeling of the printed image due to inorganic filler shedding, better reflect the texture (paper quality) of the porous layer, and improve ink adhesion, weather resistance, abrasion resistance, etc. From these perspectives, the inorganic filler content is preferably 5 parts by mass or less, more preferably 3 parts by mass or less, and even more preferably 0.1 parts by mass or less, and it is particularly preferable that the coating layer does not contain an inorganic filler. From the same viewpoint, the content of the inorganic filler in the coating layer is preferably 9 parts by mass or less, more preferably 5 parts by mass or less, even more preferably 3 parts by mass or less, and particularly preferably 0.1 parts by mass or less, per 100 parts by mass of the resin component. The content of inorganic filler in the coating layer is 9 parts by mass or less, preferably 5 parts by mass or less, more preferably 3 parts by mass or less, even more preferably 0.1 parts by mass or less, and particularly preferably 0 parts by mass (not included), per 100 parts by mass of aqueous binder.

[0036] On the other hand, from the viewpoint of preventing blocking, it is preferable to contain a small amount of inorganic filler in the coating layer. Specifically, the content of inorganic filler in the coating layer is preferably 0.1 parts by mass or more, more preferably 0.2 parts by mass or more, and even more preferably 0.3 parts by mass or more, per 100 parts by mass of the aqueous binder.

[0037] The inorganic filler that can be contained in the coating layer is not particularly limited, and can be the same as the inorganic particles described below as fillers that can be contained in the print-receiving layer and the like.

[0038] The coating layer may contain an antistatic agent from the viewpoint of preventing adhesion of dust due to static electricity and transport problems during printing, and improving the handling properties of the recording paper. Among the antistatic agents, polymer-type antistatic agents are preferred from the viewpoint of reducing surface contamination due to bleed-out. The polymer type antistatic agent is not particularly limited, and cationic, anionic, amphoteric or nonionic antistatic agents can be used, either alone or in combination of two or more.

[0039] Examples of cationic antistatic agents include antistatic agents having an ammonium salt structure, a phosphonium salt structure, etc. Examples of anionic antistatic agents include antistatic agents having an alkali metal salt structure (lithium salt, sodium salt, potassium salt, etc.) of sulfonic acid, phosphoric acid, carboxylic acid, etc. The anionic antistatic agent may be an antistatic agent having an alkali metal salt structure of acrylic acid, methacrylic acid, maleic acid (anhydride), etc. in its molecular structure.

[0040] Examples of amphoteric antistatic agents include antistatic agents containing both cationic and anionic antistatic agent structures in the same molecule. Examples of amphoteric antistatic agents include betaine antistatic agents. Examples of nonionic antistatic agents include ethylene oxide polymers having an alkylene oxide structure and polymers having an ethylene oxide polymerization component in the molecular chain. Other examples of antistatic agents include polymer antistatic agents having boron in the molecular structure.

[0041] Among these, as the polymer-type antistatic agent, a cationic antistatic agent is preferred, a nitrogen-containing polymer-type antistatic agent is more preferred, an antistatic agent having an ammonium salt structure is even more preferred, an acrylic resin having a tertiary or quaternary ammonium salt structure is particularly preferred, and an acrylic resin having a quaternary ammonium salt structure is most preferred.

[0042] From the viewpoint of antistatic properties, the content of the antistatic agent in the coating layer is preferably 0.01 parts by mass or more, more preferably 1 part by mass or more, and even more preferably 2 parts by mass or more, relative to 100 parts by mass of the aqueous binder. Also, from the viewpoint of the water resistance of the coating layer, the content of the antistatic agent in the coating layer is preferably 150 parts by mass or less, more preferably 140 parts by mass or less, and even more preferably 130 parts by mass or less, relative to 100 parts by mass of the aqueous binder.

[0043] The coating layer may contain other auxiliary components such as a crosslinking agent, a crosslinking accelerator, a pH adjuster, and an antifoaming agent, as required.

[0044] (print-receiving layer) The print-receiving layer is a porous layer containing a thermoplastic resin. As described above, the print-receiving layer is preferably a stretched layer containing a filler. That is, the print-receiving layer is preferably a stretched layer containing a thermoplastic resin and a filler. When printing is performed on the surface of the recording paper according to this embodiment on the side of the print-receiving layer, colorants such as pigments and dyes typically remain on the surface of the print-receiving layer and develop color. Meanwhile, the ink solvent passes through the print-receiving layer and moves to the lower layer (liquid-absorbing layer).

[0045] <Thermoplastic resin> Examples of thermoplastic resins used in the print-receiving layer include olefin polymers, polyamides, polyesters, polycarbonates, polystyrenes, poly(meth)acrylates, polyvinyl chloride, and mixed resins thereof. Among these, olefin polymers are preferred because of their excellent water resistance and solvent resistance.

[0046] As the olefin polymer, a propylene polymer, an ethylene polymer, etc. can be preferably used. Examples of propylene-based polymers include propylene homopolymers such as isotactic homopolypropylene and syndiotactic homopolypropylene, which are obtained by homopolymerizing propylene, and propylene copolymers in which propylene is the main component and an α-olefin such as ethylene, 1-butene, 1-hexene, 1-heptene, 1-octene, or 4-methyl-1-pentene is copolymerized. The propylene copolymer may be a binary system or a multi-component system of ternary or higher components. The propylene copolymer may also be a random copolymer or a block copolymer.

[0047] Examples of ethylene polymers include high-density polyethylene, medium-density polyethylene, linear low-density polyethylene, copolymers of ethylene with α-olefins such as propylene, butene, hexene, heptene, octene, and 4-methylpentene-1, maleic acid-modified ethylene-vinyl acetate copolymers, ethylene-vinyl acetate copolymers, ethylene-acrylic acid copolymers, ethylene-acrylic acid alkyl ester copolymers, ethylene-methacrylic acid alkyl ester copolymers, metal salts of ethylene-methacrylic acid copolymers (metals include zinc, aluminum, lithium, sodium, and potassium), ethylene-cyclic olefin copolymers, maleic acid (anhydride)-modified polyethylene, and maleic acid (anhydride)-modified polypropylene. The term "maleic anhydride" herein refers to both maleic anhydride and maleic acid.

[0048] Among the above olefin polymers, propylene homopolymers, i.e., polypropylene, or high-density polyethylene are preferred from the viewpoints of improving moldability, reducing costs, and suppressing deflection due to solvent ink. Furthermore, maleic anhydride-modified polyethylene or maleic anhydride-modified polypropylene are preferred from the viewpoints of achieving favorable pore-forming properties and filler binding properties. Among the above thermoplastic resins, one type may be used alone, or two or more types may be used in combination.

[0049] <Filler> Fillers include inorganic and organic particles. The inorganic particles and the organic particles can be used alone or in combination. When a resin composition containing a filler and a thermoplastic resin is stretched, a large number of fine pores with the particles as nuclei can be formed inside the stretched layer. This allows a porous layer to be obtained.

[0050] The filler content in the print-receiving layer is preferably 45% by mass or more, and more preferably 50% by mass or more, from the viewpoints of reducing the amount of resin used and reducing the environmental impact, and from the viewpoint of achieving favorable pore-forming properties. On the other hand, the filler content in the print-receiving layer is preferably 75% by mass or less, and more preferably 65% ​​by mass or less, from the viewpoint of suppressing the occurrence of surface defects. By having a filler content of 45% by mass or more in the print-receiving layer, it is possible to increase the porosity, which helps the ink penetrate into the liquid-absorbing layer, and increase the amount of liquid absorption. By having a filler content of 75% by mass or less, it is possible to suppress excessive porosity and liquid absorption speed.

[0051] The average particle size of the filler contained in the print-receiving layer is preferably 0.1 μm or more, more preferably 0.2 μm or more, from the viewpoint of obtaining favorable pore formation properties and controlling the liquid absorption rate. From the same viewpoint, the average particle size of the filler is preferably 5 μm or less, more preferably 3 μm or less, and even more preferably 0.9 μm or less. A filler average particle size of 0.1 μm or more makes the porous layer porous, making it easier to enhance ink permeability. A filler average particle size of 5 μm or less suppresses the formation of coarse pores, making it easier to improve the clarity of inkjet printed images and maintain surface strength. Here, the average particle size of the filler refers to the average primary particle size (D50). This is the volume-based median diameter measured by laser light diffraction / scattering.

[0052] <<Inorganic particles>> The inorganic particles are not particularly limited, but examples thereof include heavy calcium carbonate, light calcium carbonate, calcined clay, talc, titanium oxide, barium sulfate, alumina, silica, zinc oxide, zeolite, mica, glass fiber, hollow glass beads, etc. Among these, heavy calcium carbonate, calcined clay, diatomaceous earth, etc. are preferred because they are inexpensive, easily form many pores by stretching the resin composition that forms the porous layer, and allow for easy adjustment of the porosity. In particular, heavy calcium carbonate or light calcium carbonate is preferred because its average particle size or particle size distribution can be easily adjusted to a range that facilitates pore formation. Among the above inorganic particles, one type can be used alone, or two or more types can be used in combination.

[0053] <<Organic particles>> The organic particles are not particularly limited, but are preferably organic particles that are incompatible with the thermoplastic resin, have a melting point or glass transition temperature higher than that of the thermoplastic resin, and are finely dispersed under the melt-kneading conditions of the thermoplastic resin. For example, when an olefin-based resin is used as the thermoplastic resin contained in the print-receiving layer, it is preferable to use a resin selected from polyethylene terephthalate, polybutylene terephthalate, polycarbonate, nylon-6, nylon-6,6, homopolymers of cyclic olefins, copolymers of cyclic olefins and ethylene, etc., having a melting point of 120 to 300°C or a glass transition temperature of 120 to 280°C.

[0054] <<Hydrophobic surface treated filler>> The print-receiving layer preferably contains a hydrophobically surface-treated filler as the filler, or may contain only a hydrophobically surface-treated filler as the filler. The hydrophobically surface-treated filler is preferably inorganic or organic particles that have been hydrophobically surface-treated with paraffin or a fatty acid having 12 to 22 carbon atoms or a salt thereof, and more preferably inorganic or organic particles that have been hydrophobically surface-treated with a fatty acid having 12 to 22 carbon atoms or a salt thereof. By containing a hydrophobically surface-treated filler in the print-receiving layer, the formation of coarse pores or pores due to excessive porosity can be suppressed, and an excessive liquid absorption rate can be suppressed.

[0055] Examples of the fatty acid having 12 to 22 carbon atoms for the hydrophobic surface treatment include lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, oleic acid, linoleic acid, linolenic acid, and eleostearic acid. The surface treatment method is not particularly limited, and can be carried out, for example, by introducing an aqueous solution of a treatment agent into a slurry of inorganic or organic particles, thereby obtaining surface-treated inorganic or organic particles, i.e., inorganic or organic particles having, on their surfaces, a surface treatment layer containing paraffin or a fatty acid having 12 to 22 carbon atoms or a salt thereof.

[0056] The filler contained in the print-receiving layer may be a non-surface-treated filler or a hydrophilic surface-treated filler, provided that the effects of the present invention are not impaired. In this case, the content of the hydrophobic surface-treated filler in the filler contained in the print-receiving layer is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, even more preferably 80% by mass or more, and particularly preferably 90% by mass or more. All of the filler contained in the print-receiving layer may be a hydrophobic surface-treated filler.

[0057] <Other ingredients> The print-receiving layer may optionally contain known additives, such as antioxidants, light stabilizers, ultraviolet absorbers, dispersants for fillers, crystal nucleating agents, antiblocking agents, plasticizers, slip agents such as fatty acid amides, dyes, pigments, release agents, and flame retardants. From the viewpoint of improving outdoor durability, the substrate layer preferably contains an antioxidant, a light stabilizer, and the like. Examples of the antioxidant include sterically hindered phenol-based antioxidants, phosphorus-based antioxidants, and amine-based antioxidants. Examples of the light stabilizer include sterically hindered amine light stabilizers, benzotriazole light stabilizers, and benzophenone light stabilizers. The content of the antioxidant and the light stabilizer is preferably 0.001 to 1% by mass relative to the base layer.

[0058] The print-receiving layer is porous, and its porosity is preferably 32% or more, more preferably 34% or more, and even more preferably 35% or more. The porosity of the print-receiving layer is preferably 50% or less, more preferably 45% or less. A porosity within this range is preferable because it facilitates achieving both high liquid absorption speed and high surface strength. The porosity can be determined by observing the cross-section of the target layer using a scanning electron microscope, capturing the observed image in an image analyzer, and analyzing the image of the observed region to determine the area ratio of pores on the cross-section.

[0059] The basis weight of the print receiving layer is 1 g / m 2 It is preferable that the content is 1.5 g / m or more. 2 More preferably, it is 2 g / m or more. 2 The print-receiving layer preferably has a basis weight of 15 g / m or more. 2 Preferably, it is 12 g / m or less. 2 More preferably, it is 10 g / m or less. 2 It is more preferable that the basis weight is within this range, since it is easy to adjust the liquid absorption rate to the desired level.

[0060] The average pore size of the print-receiving layer is preferably 0.5 μm or more, more preferably 0.7 μm or more, and even more preferably 0.8 μm or more, from the viewpoint of preventing the liquid absorption rate from becoming too low. On the other hand, the average pore size of the print-receiving layer is preferably 20 μm or less, more preferably 14 μm or less, and even more preferably 7 μm or less, from the viewpoint of preventing a decrease in clarity due to sinking of the ink pigment. The average pore size of the print-receiving layer is determined by the same image analysis as used to determine the porosity.

[0061] (Liquid absorption layer) The liquid-absorbing layer is a layer that absorbs ink that has passed through the print-receiving layer, and is preferably provided in contact with the print-receiving layer. The liquid-absorbing layer is preferably a porous layer containing a thermoplastic resin and a stretched layer containing a filler. That is, the liquid-absorbing layer is preferably a stretched layer containing a thermoplastic resin and a filler.

[0062] <Thermoplastic resin> The thermoplastic resins used in the liquid-absorbing layer include the same thermoplastic resins as those listed in the section on the print-receiving layer, and the preferred ones among them are also the same as those mentioned above.

[0063] <Filler> The filler used in the liquid-absorbent layer may be the same as the filler listed in the section on the print-receiving layer. However, the filler used in the liquid-absorbent layer may or may not have been subjected to at least one of the above-mentioned hydrophilic surface treatment and hydrophobic surface treatment. From the viewpoint of obtaining the desired liquid absorption capacity, it is preferable that the filler used in the liquid-absorbent layer has not been subjected to a surface treatment.

[0064] The filler content in the liquid-absorbent layer is preferably 45 to 70% by mass, more preferably 50 to 65% by mass. When the filler content is equal to or greater than the lower limit, the liquid-absorbent layer tends to have a sufficient pore volume. On the other hand, from the viewpoints of achieving favorable extensibility of the layer and suppressing surface defects, the filler content is preferably equal to or less than the upper limit.

[0065] <Other ingredients> The liquid-absorbing layer may contain other optional components such as the various additives described above, as in the print-receiving layer.

[0066] The thickness and porosity of the liquid absorption layer are set so that the amount of liquid absorbed from the print receiving layer is 10 cc / m 2The porosity of the liquid-absorbent layer may be adjusted to be equal to or greater than 40%, and a layer with a high porosity may be provided in a thin layer, or a layer with a low porosity may be provided in a thick layer. From the viewpoint of improving interconnectivity and ensuring a sufficient liquid-absorbent capacity, the porosity of the liquid-absorbent layer is preferably 40% or more, more preferably 45% or more. On the other hand, from the viewpoint of improving productivity, the porosity is preferably 60% or less.

[0067] The basis weight of the liquid-absorbent layer is 5 g / m 2 It is preferable that the content is 10 g / m or more. 2 More preferably, it is 15 g / m or more. 2 More preferably, it is 19 g / m or more. 2 It is even more preferable that the content is 21 g / m or more. 2 It is particularly preferable that the basis weight of the liquid-absorbent layer is 50 g / m or more. 2 Preferably, it is 40 g / m or less. 2 More preferably, it is 37.5 g / m or less. 2 It is more preferable that the basis weight is within this range, since it is easy to adjust the amount of liquid absorption to the desired level.

[0068] (Support layer) In the recording paper according to this embodiment, a support layer may be laminated on the liquid-absorbent layer on the side opposite the print-receiving layer. Having such a support layer in the recording paper allows the recording paper to have an appropriate thickness and stiffness suitable for printing. That is, by adjusting the thickness of the support layer, the thickness of the recording paper can be adjusted, stiffness suitable for printing can be imparted, and opacity and paper feed / discharge properties can be adjusted. From the viewpoint of obtaining sufficient stiffness, the thickness of the support layer is preferably 15 μm or more, more preferably 20 μm or more, and even more preferably 30 μm or more. Furthermore, from the viewpoint of improving handling during printing, the thickness of the support layer is preferably 400 μm or less, more preferably 300 μm or less, and even more preferably 200 μm or less. The support layer may be a single layer or a laminate of two or more layers.

[0069] There are no particular limitations on the material constituting the support layer, but for example, the support layer is preferably a thermoplastic resin layer with excellent water resistance. As the thermoplastic resin, the same resins as those listed in the section on the print-receiving layer can be used. The support layer may contain a filler, as with the print-receiving layer and the liquid-absorbing layer, and may be a porous layer. The support layer may also contain other optional components, such as the additives described above.

[0070] (Back layer) The backing layer is preferably provided on the surface of the support layer opposite the print-receiving layer. The backing layer primarily functions to promote evaporation of the solvent from the receiving layer after printing when the recording paper is stored in a stack, and to suppress waviness of the paper surface due to the solvent.

[0071] The back surface layer can be made of the same material as the print-receiving layer, but the filler content in the back surface layer (the total amount when an inorganic filler and an organic filler are used in combination) is preferably 5 to 60% by mass, more preferably 10 to 50% by mass, from the viewpoint of achieving appropriate surface roughness and static friction coefficient.

[0072] The thickness of the back surface layer can be appropriately determined depending on the thickness of the support layer described above. From the viewpoint of achieving an appropriate surface roughness, the thickness of the back surface layer is preferably 1 to 50 μm, more preferably 1 to 20 μm, and even more preferably 2 to 10 μm.

[0073] The porosity of the back surface layer is preferably 5 to 60%, more preferably 5 to 50%, and even more preferably 10 to 40%. The presence of pores tends to make it possible to control the surface roughness of the back surface layer within a predetermined range.

[0074] A coating layer can also be provided on the surface of the back surface layer. The coating layer can contain an anchoring agent, a polymer-type antistatic agent, and the like. When an inkjet printing layer is provided on the coating layer, the coating layer containing the anchoring agent tends to improve adhesion between the coating layer and the inkjet printing layer. Furthermore, the coating layer containing the antistatic agent tends to improve antistatic performance on the back surface layer side. Examples of anchoring agents include polyimine polymers and ethyleneimine adducts of polyamine polyamides. Furthermore, examples of polymer-type antistatic agents include those having an ammonium salt structure or a phosphonium salt structure. When an anchoring agent and an antistatic agent are used in combination, in order to fully exhibit the performance of each individual component, the solid content ratio of the antistatic agent is preferably 0 to 200 parts by mass, more preferably 20 to 150 parts by mass, and even more preferably 30 to 100 parts by mass per 100 parts by mass of the anchoring agent.

[0075] [Characteristics of recording paper] (bending resistance) Recording paper is also suitable for use as notices such as posters, and when used as notices, it is preferable that the recording paper has a certain degree of rigidity from the viewpoint of ease of handling when applied. The bending resistance of the recording paper is preferably 0.3 mN or more, more preferably 0.4 mN or more, and even more preferably 0.5 mN or more. On the other hand, the bending resistance of the recording paper is preferably 10 mN or less, more preferably 5 mN or less, and even more preferably 3 mN or less. If the bending resistance of the recording paper is within the above range, the recording paper itself will have stiffness and be easy to handle. In addition, it tends to be less likely to wrinkle when applied to an object. Furthermore, it tends to be possible to suppress waviness after printing. The bending resistance in this embodiment is based on the bending resilience A method (Gurley method) according to JIS L1096:2010. The specific method for measuring the bending resistance of recording paper by the Gurley method will be explained in the examples below.

[0076] (glossiness) The glossiness of the surface of the print-receiving layer side of the recording paper is preferably 50% or more, more preferably 60% or more, and even more preferably 70% or more. If the glossiness of the surface of the print-receiving layer side is equal to or greater than the lower limit mentioned above, it can be said that a sufficiently high glossiness is obtained, at least compared with recording paper using a pigment coating or the like, and images tend to be clearer and have a better appearance. The glossiness in this embodiment is based on the glossiness according to JIS P 8142:1993. The specific method for measuring the glossiness of the surface of the print-receiving layer side of the recording paper will be explained in the examples below.

[0077] (Surface strength) The surface strength of the print-receiving layer side is preferably 0.7 kgf / cm or more, more preferably 0.9 kgf / cm or more, and even more preferably 1.0 kgf / cm or more. Meanwhile, the surface strength of the receiving layer may be 2.0 kgf / cm or less, 1.5 kgf / cm or less, or 1.2 kgf / cm or less. If the surface strength of the print-receiving layer side is within the above range, when the recording paper is displayed outdoors, the surface of the print-receiving layer side is less likely to be scraped by sand or the like, and the weather resistance is high, so the printed pattern tends to be able to be maintained for a long period of time. A specific method for measuring the surface strength on the print-receiving layer side will be explained in the examples below.

[0078] (Smoothness) The smoothness of the surface on the print-receiving layer side is preferably 1000 seconds or more, more preferably 1300 seconds or more, and even more preferably 1800 seconds or more, from the viewpoint of clearer images and better appearance, while the smoothness of the surface on the print-receiving layer side is preferably 10000 seconds or less, more preferably 9000 seconds or less, and even more preferably 8000 seconds or less, from the viewpoint of suppressing blocking after cutting. The specific method for measuring the smoothness of the surface on the print-receiving layer side will be explained in the examples below.

[0079] [Manufacturing method] The method for producing the recording paper of the present invention is not particularly limited, but examples include the following methods. For example, when the recording paper has a print-receiving layer, a liquid-absorbent layer, a support layer, and a back surface layer, a thermoplastic resin film constituting the support layer may be formed, and then a laminated resin film constituting the print-receiving layer and the liquid-absorbent layer may be laminated on one side of the support layer, and the back surface layer may be laminated on the other side. In this case, the print-receiving layer and the liquid-absorbent layer may be co-extruded onto one side of the support layer using a multi-layer die system using a feed block and a multi-manifold, and the back surface layer may be extruded onto the other side, and then co-stretched to form a laminated resin film in which these layers are made porous. Alternatively, multiple dies may be used to extrude and laminate one layer onto the surface of the other layer, and then stretched to form a laminated resin film in which both layers are made porous.

[0080] Alternatively, the support layer, liquid-absorbent layer, print-receiving layer, and backside layer may all be co-extruded and then co-stretched; the support layer, liquid-absorbent layer, and backside layer may be co-extruded, followed by extrusion lamination of the print-receiving layer onto the surface of the liquid-absorbent layer and subsequent co-stretching; the support layer, liquid-absorbent layer, and print-receiving layer may be co-extruded, followed by extrusion lamination of the backside layer onto the surface of the support layer and subsequent co-stretching; the support layer and liquid-absorbent layer may be co-extruded, followed by extrusion lamination of the print-receiving layer onto the surface of the liquid-absorbent layer and the backside layer onto the surface of the support layer, respectively, followed by co-stretching; or the liquid-absorbent layer and print-receiving layer may be extrusion laminated onto one side of the support layer and the backside layer onto the other side of the support layer, followed by co-stretching, thereby simultaneously rendering the liquid-absorbent layer and print-receiving layer porous and laminating them to the support. From the standpoint of process simplicity and reduced production costs, co-extrusion and / or extrusion lamination followed by co-stretching is preferred. Known stretching methods can be used.

[0081] Examples of film stretching methods include longitudinal stretching using the difference in peripheral speed between rolls, transverse stretching using a tenter oven, sequential biaxial stretching using a combination of these, rolling, simultaneous biaxial stretching using a tenter oven and a pantograph, or simultaneous biaxial stretching using a tenter oven and a linear motor. Also usable are simultaneous biaxial stretching (blowing) methods, in which molten resin is extruded into a tubular shape using a circular die connected to a screw extruder and then air is blown into the extruded tubular shape. When manufacturing a multilayer substrate containing multiple stretched films, each layer may be stretched individually before lamination, or may be stretched together after lamination. Furthermore, the stretched layers may be stretched again after lamination.

[0082] When the thermoplastic resin used in the layer to be stretched is an amorphous resin, the stretching temperature is preferably in a range equal to or higher than the glass transition temperature of the thermoplastic resin. Furthermore, when the thermoplastic resin is a crystalline resin, the stretching temperature is preferably equal to or higher than the glass transition temperature of the amorphous portion of the thermoplastic resin and equal to or lower than the melting point of the crystalline portion of the thermoplastic resin, specifically, a temperature 2 to 60°C lower than the melting point of the thermoplastic resin is preferred. A stretching temperature that is 2°C or higher, preferably 10°C or higher, and more preferably 20°C or higher than the melting point of the thermoplastic resin is preferred because it allows for greater control of the porosity or pore size, and further allows for greater control of the liquid absorption amount and liquid absorption speed.

[0083] In the case of uniaxial stretching, the stretching ratio is usually 1.2 times or more, preferably 2 times or more, and usually 10 times or less, preferably 5 times or less. In the case of biaxial stretching, the stretching ratio is usually 1.5 times or more, preferably 4 times or more, in terms of area stretching ratio, and usually 20 times or less, preferably 12 times or less. Within the above-mentioned range of stretching ratio, stable stretch molding tends to be possible. Furthermore, even when a resin composition containing a thermoplastic resin and a filler is used, within the above-mentioned range of stretching ratio, the target porosity is easily obtained, the opacity is easily improved, and the film is less likely to break.

[0084] Alternatively, the coating layer can be formed by applying the coating liquid for forming the coating layer to the stretched laminated resin film and drying it.

[0085] (printing) The recording paper according to this embodiment can be printed on the surface of the print-receiving layer side. The printing method used for the print-receiving layer is not particularly limited, and in addition to various known plate-based printing methods such as gravure printing, offset printing, flexographic printing, seal printing, and screen printing, digital printing using various printers such as inkjet printers, electrophotographic printers, and liquid toner printers, and thermal melt transfer printing can also be used.

[0086] For printing, various inks can be used depending on the printing method, such as ultraviolet-curable ink, oil-based ink, oxidative polymerization-curable ink, melt thermal transfer recording ink, water-based ink, solvent ink, powder toner, or liquid toner (electroink).

[0087] In particular, the recording paper according to this embodiment is suitable for inkjet printing, particularly inkjet printing using aqueous ink or solvent ink, and particularly inkjet printing using solvent ink. The recording paper according to this embodiment has a print-receiving layer, a liquid-absorbing layer, and a predetermined coating layer, and has a liquid absorption rate within a specific range and a liquid absorption amount equal to or greater than a specific value, thereby providing excellent print quality, drying properties, and weather resistance.

[0088] Solvent-based inks generally contain a solvent and a colorant specific to solvent-based inks. Examples of solvents used in solvent-based inks include glycol ether-based solvents such as polyoxyethylene glycol dialkyl ether, polyoxyethylene glycol monoalkyl ether, and polypropylene glycol monoalkyl ether. Examples of colorants used in solvent-based inks include oil-soluble dyes such as naphthol dyes, azo dyes, metal complex dyes, anthraquinone dyes, quinoimine dyes, indigo dyes, cyanine dyes, quinoline dyes, nitro dyes, nitroso dyes, benzoquinone dyes, carbonium dyes, naphthoquinone dyes, naphthalimide dyes, phthalocyanine dyes, and perinine dyes. Examples of pigments used include carbon black and various color pigments, and examples of organic pigments include insoluble azo pigments, condensed azo pigments, chelate azo pigments, perinone pigments, nitro pigments, nitroso pigments, perylene pigments, and aniline black. [Example]

[0089] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0090] (Production Example 1: Production of Hydrophilic Treated Calcium Carbonate) A reactor equipped with a reflux condenser, thermometer, dropping funnel, stirrer, and gas inlet tube was charged with 500 parts by weight of diallylamine hydrochloride (60% aqueous solution), 13 parts by weight of acrylamide (40% aqueous solution), and 40 parts by weight of water. The temperature inside the system was raised to 80°C while introducing nitrogen gas. With stirring, 30 parts by weight of ammonium persulfate (25% aqueous solution) as a polymerization initiator was added dropwise using the dropping funnel over a period of 4 hours. After the completion of the addition, the reaction was continued for 1 hour, yielding a viscous pale yellow liquid. 50 parts by weight of this was poured into 500 parts by weight of acetone, resulting in the formation of a white precipitate. The precipitate was filtered, thoroughly washed twice with 100 parts by weight of acetone, and then vacuum dried to obtain a white solid polymer (water-soluble cationic copolymer). The weight-average molecular weight of the resulting polymer was determined by GPC to be 55,000. Next, 40% by mass of heavy calcium carbonate (average particle size 8 μm, manufactured by Nippon Cement Co., Ltd., dry-ground product) and 60% by mass of water were thoroughly stirred and mixed to form a slurry, to which 0.06 parts by mass of the water-soluble cationic copolymer produced above was added per 100 parts by mass of heavy calcium carbonate, and the mixture was wet-ground using a table-type attritor-type media stirring mill (glass beads with a diameter of 1.5 mm, a filling rate of 170%, and a peripheral speed of 10 m / sec). Next, 50 parts by mass of a mixture (2% by mass aqueous solution) of sodium alkylsulfonate having 14 carbon atoms as the main component and sodium alkylsulfonate having 16 carbon atoms as the main component was added and stirred. The mixture was then classified through a 350-mesh screen, and the slurry that passed through the 350-mesh screen was dried in a fluidized bed dryer (MSD-200, manufactured by Nara Machinery Works, Ltd.). The average primary particle size of the obtained calcium carbonate was measured using a Microtrac (manufactured by Nikkiso Co., Ltd.) and found to be 1.5 μm.

[0091] (Production Example 2: Production of Hydrophobized Calcium Carbonate) BET specific surface area is 16m 2 Water was added to 500 parts by mass of synthetic calcium carbonate (precipitated calcium carbonate) with a molecular weight of 1 / g, and the mixture was stirred at 40°C to prepare a calcium carbonate slurry with a solids content of 10% by mass. Next, a 10% by mass aqueous solution of sodium laurate was prepared at 90°C, and the prepared solution was mixed with the calcium carbonate slurry and stirred to hydrophobize the calcium carbonate surface. This hydrophobized calcium carbonate slurry was dried until the solids content reached 60%. It was then dehydrated using a dryer to obtain calcium carbonate that had been subjected to a hydrophobized surface treatment. The average primary particle size of the obtained calcium carbonate was measured using an ultrasonic disperser Model US-300T (manufactured by Nippon Seiki Co., Ltd.) using ethanol as a solvent and ultrasonic dispersion at 300 μA for 60 seconds, and was found to be 0.23 μm.

[0092] (Resin composition) The materials were stirred and mixed in a mixer to obtain the compositions (parts by mass) shown in Table 1, and then extruded to obtain resin compositions a to h. In Table 1, "MFR" stands for melt flow rate. A blank cell in Table 1 indicates that the compounding ratio is 0 parts by mass.

[0093] [Table 1]

[0094] (Coating composition) Coating compositions (coating solutions) a to d were obtained by mixing the materials to obtain the formulations (solid content ratio, parts by mass) shown in Table 2. Blank cells in Table 2 indicate that the solid content ratio is 0 parts by mass.

[0095] [Table 2]

[0096] Example 1 Resin composition a listed in Table 1 was melt-kneaded in an extruder set at 230°C, then fed into an extrusion die set at 250°C and extruded into a sheet. This was then cooled to 60°C using a cooling device to obtain an unstretched sheet. This unstretched sheet was heated to 140°C and stretched 5 times in the machine direction using the difference in peripheral speed between rolls. Next, resin compositions c and e were melt-kneaded in an extruder set at 230°C, and resin composition c was extruded into a sheet so that it was in contact with the stretched sheet and laminated onto the first side of the stretched sheet. At the same time, resin composition a was melt-kneaded in a single extruder set at 230°C, extruded into a sheet, and laminated onto the second side of the stretched sheet to obtain a four-layer laminate sheet. Next, this four-layer laminate sheet was cooled to 60°C, heated to approximately 155°C using a tenter oven, stretched 9 times in the machine direction, and then further heated to 160°C for heat treatment. The film was then cooled to 60°C, and the edges were slit to obtain a laminated resin film having a thickness of 120 μm, resin compositions for each layer (print-receiving layer / liquid-absorbing layer / support layer / back surface layer=e / c / a / a), thicknesses of each layer (2 μm / 42 μm / 46 μm / 30 μm), and axial orientation numbers for each layer (uniaxial / uniaxial / biaxial / uniaxial). A coating amount of 0.15 g / m2 was applied to the surface of the laminated resin film after drying. 2 The coating composition was applied so that the coating film was dried in an oven at 60° C. to form a coating layer, thereby obtaining the recording paper of Example 1.

[0097] (Examples 2 to 11 and 13 to 14) Recording papers of Examples 2 to 11 and 13 to 14 were obtained in the same manner as in Example 1, except that the types of resin composition and coating composition used and the stretching conditions were changed as shown in Table 3. The thicknesses of the support layer and backside layer in Examples 2 to 11 and 13 to 14 were the same as in Example 1.

[0098] Example 12 Resin composition a listed in Table 1 was melt-kneaded in an extruder set at 230 ° C, then fed into an extrusion die set at 250 ° C, extruded into a sheet, and cooled to 60 ° C using a cooling device to obtain an unstretched sheet. Next, resin compositions c and e were melt-kneaded in an extruder set at 230 ° C, and resin composition c was extruded into a sheet so that it was in contact with the unstretched sheet and laminated onto the first side of the unstretched sheet. At the same time, resin composition a was melt-kneaded in a single extruder set at 230 ° C, extruded into a sheet, and laminated onto the second side of the stretched sheet to obtain a four-layer laminate sheet. Next, this four-layer laminate sheet was cooled to 60 ° C, heated to about 155 ° C using a tenter oven, stretched 9 times in the transverse direction, and then further heated to 160 ° C for heat treatment. The film was then cooled to 60°C, and the edges were slit to obtain a laminated resin film having a thickness of 120 μm, resin compositions for each layer (print-receiving layer / liquid-absorbing layer / support layer / back surface layer=e / c / a / a), thicknesses of each layer (2 μm / 42 μm / 46 μm / 30 μm), and axial orientation numbers for each layer (uniaxial / uniaxial / uniaxial / uniaxial). A coating amount of 0.15 g / m2 was applied to the surface of the laminated resin film after drying. 2 The coating composition was applied so that the coating film was dried in an oven at 60° C. to form a coating layer, and the recording paper of Example 12 was obtained.

[0099] (Comparative Example 1) Resin composition a listed in Table 1 was melt-kneaded in an extruder set at 230 ° C, then fed into an extrusion die set at 250 ° C, extruded into a sheet, and cooled to 60 ° C using a cooling device to obtain an unstretched sheet. This unstretched sheet was heated to 140 ° C and stretched 5 times in the machine direction using the difference in peripheral speed between the rolls to obtain a single-layer uniaxially stretched sheet. Next, resin composition a was melt-kneaded in a single extruder set at 230 ° C, extruded into a sheet, and laminated on the second side of the stretched sheet to obtain a two-layer laminate sheet. Next, this two-layer laminate sheet was cooled to 60 ° C, heated to approximately 155 ° C using a tenter oven, stretched 9 times in the transverse direction, and then further heated to 160 ° C for heat treatment. The film was then cooled to 60°C, and the edges were slit to obtain a laminated resin film having a thickness of 100 μm, resin compositions for each layer (support layer / back surface layer = a / a), thicknesses for each layer (70 μm / 30 μm), and number of stretching axes for each layer (biaxial / uniaxial). On the other hand, 55 parts by mass of water, 20 parts by mass of finely powdered silica ("Mizukasil P-78F" manufactured by Mizusawa Chemical Industry Co., Ltd., average particle size 12.5 μm), and 25 parts by mass of hydrophobic resin (acrylic resin emulsion) ("Acronal YJ-2870D" manufactured by BASF Japan Ltd., solids concentration 50% by mass) were mixed and dispersed to prepare coating layer composition c. A coating layer composition was applied to one side of the laminated resin film obtained above, and dried to form a coating layer with a thickness of 20 μm. After drying in an oven at 70° C. for 60 seconds, a recording paper of Comparative Example 1 with a thickness of 120 μm was obtained.

[0100] (Comparative Example 2) Resin composition h shown in Table 1 was kneaded and rolled for 5 minutes using two 9-inch test rolls (steam-heated type manufactured by Nishimura Koki Co., Ltd.) set at 160°C to produce a vinyl chloride resin sheet with a thickness of 140 μm (calendering). The obtained vinyl chloride resin sheet was subjected to a maximum pressure of 70 kg / cm at a temperature of 170°C in a 37-ton hydraulic molding machine (manufactured by Oji Machinery Co., Ltd.). 2 The surface was finished to a mirror finish, and a recording paper of Comparative Example 2 having a thickness of 140 μm was obtained.

[0101] (Comparative Example 3) Resin composition a listed in Table 1 was melt-kneaded in an extruder set at 230 ° C., then fed into an extrusion die set at 250 ° C. and extruded into a sheet, which was then cooled to 60 ° C. using a cooling device to obtain an unstretched sheet. Next, resin compositions c and e were melt-kneaded in an extruder set at 230 ° C., and resin composition c was extruded into a sheet so that it was in contact with the unstretched sheet and laminated onto the first side of the unstretched sheet. At the same time, resin composition a was melt-kneaded in a single extruder set at 230 ° C., then extruded into a sheet and laminated onto the second side of the stretched sheet to obtain a four-layer laminate sheet. Next, the sheet was cooled to 60 ° C., and the edge portions were slit to obtain a laminated resin film with a thickness of 71 μm, each layer having a resin composition (print-receiving layer / liquid-absorbing layer / support layer / backside layer = e / c / a / a), each layer thickness (1 μm / 20 μm / 25 μm / 25 μm), and each layer stretching axis number (unstretched / unstretched / unstretched / unstretched). On the surface of the laminated resin film, the coating amount after drying is 0.15 g / m 2 The coating composition was applied so that the coating film was dried in an oven at 60° C. to form a coating layer, thereby obtaining the recording paper of Comparative Example 3.

[0102] Comparative Example 4 A recording paper of Comparative Example 4 was obtained in the same manner as in Example 1, except that no coating layer was applied.

[0103] (Comparative Examples 5 to 7) Recording papers of Comparative Examples 5 to 7 were obtained in the same manner as in Example 1, except that the types of resin composition and coating composition used and the stretching conditions were changed as shown in Table 3. The thicknesses of the support layer and backside layer in Comparative Examples 5 to 7 were the same as in Example 1.

[0104] (evaluation) The recording paper obtained in each of the Examples and Comparative Examples was subjected to the following measurements, and the results are shown in Table 3.

[0105] (Liquid absorption amount) The amount of liquid absorbed by the recording paper was measured using a water absorption tester specified in JIS P 8140. First, a solvent (diethylene glycol ethyl methyl ether manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was brought into contact with the surface of the print-receiving layer side of the test piece for 60 seconds, and the mass of the test piece was measured after removing excess solvent. Next, the measured mass of the test piece was subtracted from the original mass of the test piece to obtain the mass of 1 m 2 The mass of solvent absorbed per unit area is called the solvent absorption (cc / m 2 ) was decided.

[0106] (Liquid absorption speed) The liquid absorption rate on the print-receiving layer side of the recording paper was measured using a water absorption tester specified in JIS P 8140. A solvent (diethylene glycol ethyl methyl ether, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was brought into contact with the surface of the print-receiving layer of the test piece for 5 seconds, the amount of solvent absorbed was calculated, and the value divided by the solvent contact time was used to determine the liquid absorption rate (cc / m 2 0.5s).

[0107] (Surface strength) The surface strength of the print-receiving layer side of the recording paper was measured as follows: Cellophane tape (manufactured by Nichiban Co., Ltd., product name: CT-18) was applied to the surface of the print-receiving layer side, and the ink peel strength was measured using an internal bond tester (manufactured by Kumagai Riki Kogyo Co., Ltd., product name) in accordance with JAPAN TAPPI No. 18-2 (internal bond strength test method), and the average value of two measurement results was taken as the surface strength.

[0108] (Thickness) The thickness (total thickness) of the recording paper was measured in accordance with JIS K7130:1999 using a constant pressure thickness measuring instrument (manufactured by Teclock Corporation, product name: PG-01J). The thickness of each layer in the recording paper was measured by cooling the sample to a temperature of -60°C or below with liquid nitrogen, placing the sample on a glass plate, and cutting it at a right angle with a razor blade (manufactured by Schick Japan Co., Ltd., product name: Proline Blade) to prepare a sample for cross-sectional observation. The resulting sample was then observed using a scanning electron microscope (manufactured by JEOL Ltd., product name: JSM-6490). The boundary lines between each resin composition were identified from the compositional appearance, and the thickness of each layer was multiplied by the observed thickness ratio of the total thickness of the recording paper. The thicknesses of the print-receiving layer and liquid-absorbing layer determined by this method are shown in Table 3. Since the recording paper in Comparative Examples 1 and 2 did not have a print-receiving layer or liquid-absorbing layer, the thickness of the coating layer for Comparative Example 1 and the thickness of the support layer for Comparative Example 2 are shown in Table 3.

[0109] (bending resistance) The Gurley stiffness of the recording paper was measured in the MD direction of the recording paper in accordance with JIS L1096:2010 under an environment of a temperature of 23°C and a humidity of 50% RH using a Gurley stiffness tester (manufactured by Daiei Scientific Instruments Co., Ltd., product name: GAS-100).

[0110] (Glossiness of the surface on the print-receiving layer side) The glossiness of the surface of the print-receiving layer side of the recording paper was measured in accordance with JIS P 8142:1993, and the 75-degree specular glossiness was measured.

[0111] (Smoothness of the surface on the print-receiving layer side) The Oken-type smoothness of the surface on the print-receiving layer side of the recording paper was measured using a digital Oken-type air permeability and smoothness tester ("EYO-55-1M" manufactured by Asahi Seiko Co., Ltd.) in accordance with JIS P 8155:2010 "Paper and paperboard - Smoothness test method - Oken method."

[0112] (Average pore diameter) The average pore diameter of the print-receiving layer was determined as follows: the surface of the target layer was observed using a scanning electron microscope, the observed image was imported into an image analyzer, and the observed area was subjected to image analysis to calculate the average pore diameter of the pores on the surface.

[0113] (porosity) The porosity of the print-receiving layer and the liquid-absorbing layer was determined as follows. The cross section of each layer was observed using a scanning electron microscope, and the thickness of each layer was measured. The theoretical thickness before pore formation was calculated from the basis weight and true density of the resin composition constituting each layer, and the porosity was calculated using the following formula. Porosity (%) = 100 × (1 - theoretical thickness / layer thickness)

[0114] [Table 3]

[0115] The recording papers obtained in the examples and comparative examples were evaluated for the following items. The results are shown in Table 4.

[0116] (solvent inkjet printing) A sample image was printed on the print-receiving layer side of the recording paper using a solvent inkjet printer "SureColor SC-S80650" (manufactured by Seiko Epson Corporation).

[0117] (concentration) After solvent inkjet printing, the print density of nine black areas on the printed surface was measured using a portable spectrodensitometer (manufactured by X-Rite Corporation, product name "508"), the average value was calculated, and the density was judged according to the following criteria. 5 (Good): The average print density was 1.6 or more and the ink color development was good. 4 (Good): The average print density was less than 1.6 and 1.4 or more, and the ink color development was good. 3 (Acceptable, practical lower limit): The average print density was less than 1.4, and a slight decrease in density was observed when the average print density was 1.2 or more, but it was not a problem. 2 (unacceptable, not suitable for practical use): The average print density was less than 1.2, and a decrease in density was observed when the average print density was 1.0 or more. 1 (unacceptable, not suitable for practical use): The average print density was less than 1.0.

[0118] (bleed) After solvent inkjet printing, the state of the printed image on the recording paper was magnified with a magnifying glass and visually observed. The bleeding on the recording paper was evaluated based on the observed state of the image according to the following criteria. 5 (Good): The image was clear. 4 (Good): The image was clear to the naked eye, but the dot area was somewhat large when observed with a magnifying glass. 3 (Fair): The ink bleeding was slightly unclear when visually inspected, and the dot area was found to be larger when observed with a magnifying glass. 2 (Acceptable, practical lower limit): Ink bleeding was unclear when visually observed, and the dot area was found to have expanded when observed with a magnifying glass. 1 (unacceptable, not suitable for practical use): The image was blurred.

[0119] (Dry) After solvent inkjet printing, one print sample was randomly taken out every 10 minutes and the state of drying of the ink in the solid image area was checked by rubbing it with a finger. The drying property was evaluated according to the following criteria. 5 (Good): Dries very quickly. (Dries within 5 minutes and does not stick to fingers.) 4 (Good): Dries very quickly. (Dries within 10 minutes and does not stick to fingers.) 3 (Acceptable, practical lower limit): Drying was fast and not problematic (drying in more than 10 to 20 minutes). 2 (Unacceptable, not suitable for practical use): Drying was somewhat slow, to the point of being problematic (drying took more than 20 minutes but less than 30 minutes). 1 (Unacceptable, not suitable for practical use): Drying was slow to the point of being problematic (it was not dry even after 30 minutes).

[0120] (Fixation) (Abrasion) After solvent inkjet printing, the image area was cut out to a size of 30 mm x 120 mm one day after printing and placed in a Gakushin Testing Machine (manufactured by Suga Testing Machines). For evaluation under dry conditions, a piece of gauze dried at room temperature was attached to a 215 g weight, and the surface of the printed image area was rubbed with this weight 100 times, and the degree of ink peeling was evaluated by visual observation. For evaluation under wet conditions, a piece of gauze soaked with 20 μL of pure water at room temperature was attached to a 215 g weight, and the surface of the printed image area was rubbed with this weight 100 times, and the degree of ink peeling was evaluated by visual observation. Scratching was evaluated according to the following criteria. 5 (good): 95% or more of the rubbed image remained. 4 (Good): 90% or more of the rubbed image remained. 3 (Acceptable, practical lower limit): 80% or more of the rubbed image remained. 2 (unacceptable, not suitable for practical use): 70% or more of the rubbed image remained. 1 (unacceptable, not suitable for practical use): Less than 70% of the rubbed image remained. (ink adhesion) After solvent inkjet printing, the adhesive side of cellophane tape (manufactured by Nichiban Co., Ltd., product name: Cellotape (registered trademark) CT-18) was applied to the printed surface and rubbed three times with a finger to ensure sufficient adhesion. The cellophane tape was then manually peeled off in a 180° direction at a speed of 300 m / min, and the ink remaining rate on the recording paper was calculated using a small, general-purpose image analyzer (manufactured by Nireco Corporation, model name: LUZEX-AP). Specifically, the printed surface was photographed, and the resulting image was binarized to calculate the ink remaining rate as the percentage of the area occupied by the ink. Ink adhesion was evaluated based on the calculated ink remaining rate using the following criteria. 5 (Good): The ink remaining rate was 80% or more. 3 (Acceptable, practical lower limit): Ink remaining rate was 50% or more but less than 80%. 1 (unacceptable, not suitable for practical use): Less than 50% of the ink remained.

[0121] (Wavy) A solid black print was printed on the print-receiving layer side of the recording paper using a solvent inkjet printer "SureColor SC-S80650" (manufactured by Seiko Epson Corporation), and the degree of waviness in the printed area was visually evaluated according to the following criteria. 5 (good): No waviness was observed, and the level was extremely good. 3 (Acceptable, practical lower limit): Slight waviness occurred. 1 (unacceptable, not suitable for practical use): Waving was observed.

[0122] (blocking) A solid black print was printed on the print-receiving layer side of the recording paper using a solvent inkjet printer "SureColor SC-S80650" (manufactured by Seiko Epson Corporation). The printed recording paper was wound into a roll and stored for one day in an atmosphere of 40°C and 50% relative humidity. After that, the paper was observed to see if it could be smoothly pulled out of the roll without causing blocking. Blocking was evaluated according to the following criteria. 5 (Good): It was pulled out smoothly without any peeling noise. 3 (Acceptable, practical lower limit): There was a peeling sound, but the appearance of the base layer after removal was not impaired. 1 (unacceptable, not suitable for practical use): There was a loud peeling noise, and the appearance of the base layer was marred after removal.

[0123] (weather resistance) In applications such as posters, peeling of ink can be problematic when used outdoors. However, when weather resistance is evaluated through an outdoor exposure test, the results are prone to fluctuation due to various variables such as climate and weather. In this embodiment, the printed matter was subjected to an accelerated weather resistance treatment (exposure test) under uniform conditions in accordance with JIS K-7350-4, followed by solvent inkjet printing, and then the ink adhesion was evaluated. More specifically, the accelerated treatment was performed under the following conditions. An ultra-accelerated weathering tester (Daipla Wintes Co., Ltd., trade name "Metal Weather KU-R5N-A", metal halide lamp type) and a glass filter "KF-2 Filter" (trade name) that transmits ultraviolet light from 295 to 450 nm were used. The recording paper printed using the above procedure was cut into a size of 90 mm x 150 mm to obtain a test specimen. The four sides were fixed to a stainless steel plate (100 mm x 200 mm) with aluminum foil tape "AL-T" (Takeuchi Kogyo Co., Ltd., trade name) so that the printed side was the exposed surface, and this was then placed in the tester. The irradiance on the surface of the test specimen was 90 W / m 2 The black panel temperature was set to 63°C. Two cycles of accelerated treatment were performed, each consisting of 5 hours of exposure at 63°C and 50% relative humidity and 3 hours of exposure at 30°C and 98% relative humidity. Therefore, the radiation exposure dose to the printed surface was 5.18 x 10 6 J / m 2 It was. Next, the test pieces that had been subjected to the weather resistance acceleration treatment were subjected to a friction test and evaluation in the same manner as in the case of abrasion resistance. 5 (good): 95% or more of the rubbed image remained. 3 (Acceptable, practical lower limit): 80% or more of the rubbed image remained. 1 (unacceptable, not suitable for practical use): Less than 80% of the rubbed image remained.

[0124] [Table 4]

[0125] As shown in Table 4, the recording papers of Examples 1 to 14 were provided with a print-receiving layer, a liquid-absorbing layer, and a predetermined coating layer, and had a liquid absorption rate within a specific range and a liquid absorption amount equal to or greater than a specific value, thereby achieving excellent print quality, drying properties, and weather resistance. On the other hand, the recording papers of Comparative Examples 1 to 7 were not suitable for practical use in one or more of the evaluation items, and were unable to achieve a balance between print quality, drying properties, and weather resistance.

[0126] Comparing Examples 1 to 3, there was a tendency for the liquid absorption rate to increase as the basis weight of the print-receiving layer decreased. Accordingly, the recording papers of Examples 1 to 3 tended to have better bleeding evaluations as the liquid absorption rate increased. Comparing Examples 3 and 4, the basis weight of the liquid-absorbent layer was greater in Example 3, resulting in a greater amount of liquid absorption. The recording paper of Example 3 was evaluated as having better drying properties than the recording paper of Example 4. Comparing Examples 1, 5, and 6, the difference in the type (average particle size and surface treatment) and formulation of the filler used in the print-receiving layer resulted in a difference in the average pore size of the print-receiving layer, which in turn changed the liquid absorption rate. For the recording papers of Examples 1, 5, and 6, the lower the liquid absorption rate, the better the evaluation of bleeding. Comparing Examples 1 and 7, Example 7 differs in that the resin composition used in the support layer does not contain a filler, but the evaluation results for the recording papers of Examples 1 and 7 were comparable. Comparing Examples 1, 8, and 9, it was found that the porosity decreased as the transverse stretching temperature increased, and both the liquid absorption amount and the liquid absorption speed tended to decrease. Accordingly, the recording papers of Examples 1, 8, and 9 showed differences in the evaluation results of drying property and bleeding. Comparing Examples 1 and 10, Example 10 has a larger coating weight after drying of the coating layer and a slower liquid absorption rate. The recording paper of Example 1 was evaluated as being superior to the recording paper of Example 10 in terms of bleeding. Comparing Examples 1 and 11, the coating composition used in the coating layer is different. The recording paper of Example 11 used a water-dispersible resin in the coating composition, and as a result, the abrasion evaluation was superior to that of the recording paper of Example 1. When Examples 1 and 12 are compared, the evaluation results for the recording papers of Examples 1 and 12 were the same, although the numbers of stretching axes of the support layers were different. Comparing Examples 11 and 13, the recording paper of Example 13 was evaluated as being superior in bleeding because the coating composition consisted of only an aqueous binder.

[0127] The recording paper of Comparative Example 1 has a coating layer containing a pigment, but the coating layer contains a large amount of inorganic filler. The recording paper of Comparative Example 1 was evaluated as being unsuitable for practical use in terms of abrasion resistance compared to the recording paper of Example 1, which does not contain inorganic filler in the coating layer. The recording paper of Comparative Example 2 has a layer containing a vinyl chloride copolymer, and does not have a porous layer such as a coating layer, a print-receiving layer, or a liquid-absorbing layer. The recording paper of Comparative Example 2 was evaluated as being unsuitable for practical use in terms of waviness, blocking, and weather resistance. The recording paper of Comparative Example 3 does not have a porous layer, and therefore the liquid absorption amount and liquid absorption speed are both too small. The recording paper of Comparative Example 2 was evaluated as not suitable for practical use in terms of bleeding and drying. The recording paper of Comparative Example 4 does not have a coating layer. The recording paper of Comparative Example 4 was evaluated as being unsuitable for practical use in terms of density, abrasion resistance, and ink fixation. The recording paper of Comparative Example 5 had too little liquid absorption, and the evaluation result of the recording paper of Comparative Example 5 was that it was not suitable for practical use in terms of drying. The recording paper of Comparative Example 6 had too little liquid absorption, and the evaluation results for the recording paper of Comparative Example 6 showed that it was not suitable for practical use in terms of bleeding and drying. The recording paper of Comparative Example 7 had an excessively high liquid absorption rate, and the evaluation results for the recording paper of Comparative Example 7 showed that it was not suitable for practical use in terms of density and abrasion resistance.

[0128] Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. This application is based on a Japanese patent application (Patent Application No. 2022-102227) filed on June 24, 2022, the contents of which are incorporated herein by reference. [Explanation of symbols]

[0129] 1 Recording sheet 9 Backing layer 10 Support layer 11 Liquid absorption layer 12 Print-receptive layer 13 Coating layer

Claims

1. A recording paper having a coating layer, a print-receiving layer, and a liquid-absorbing layer in this order, the coating layer contains an aqueous binder as a resin component, the print-receiving layer and the liquid-absorbing layer are both porous layers containing a thermoplastic resin, The liquid absorption rate on the surface on the print-receiving layer side is 5 to 25 cc / m ２ 0.5 s, Absorption capacity: 10cc / m ２ That's all, the liquid-absorbent layer has a basis weight of 21 g / m 2 or more; The recording paper, wherein the content of the inorganic filler in the coating layer is 9 parts by mass or less relative to 100 parts by mass of the aqueous binder.

2. 2. The recording paper according to claim 1, wherein the print-receiving layer has a porosity of 30 to 50%, and the liquid-absorbing layer has a porosity of 40 to 60%.

3. 3. The recording paper according to claim 1, wherein the print-receiving layer and the liquid-absorbing layer are both stretched layers containing a filler.

4. 4. The recording paper according to claim 3, wherein the print-receiving layer contains 45 to 75% by mass of filler.

5. The recording paper according to claim 3 , wherein the print-receiving layer contains a hydrophobic surface-treated filler as a filler.

6. 3. The recording paper according to claim 1, wherein the print-receiving layer has an average pore size of 0.5 to 20 μm.

7. The recording paper according to claim 1 or 2, wherein the content of the resin component in the coating layer exceeds 80% by mass.

8. The coating amount of the coating layer after drying is 0.05 to 5 g / m ２ 3. The recording paper according to claim 1 or 2, wherein:

9. The recording paper according to claim 1 or 2, wherein the coating layer contains a water-dispersible resin.

Images