JP2014159110A - Recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a recording medium that can provide an image which has high glossiness and in which occurrence of white mist is suppressed.SOLUTION: The recording medium has a substrate and an ink-receiving layer in this order. An arithmetic mean roughness of a surface of the recording medium at an ink-receiving layer side is 1.3 μm or more, which is specified by JIS B 0601:2001, and the 60-degree specular gloss thereof which is specified by JIS Z 8741 is 30% or more.

Description

  The present invention relates to a recording medium.

  In recent years, there has been an increasing need to create a photo book using a recording medium that records an image with ink. Along with this, there is an increasing demand for a recording medium that can provide a glossy image with a high-class feeling when converted into a photobook.

As a method for improving the glossiness of a recording medium, a method of providing a layer mainly composed of a resin on an ink receiving layer is conventionally known (Patent Document 1). Patent Document 1 discloses a recording in which a dispersion containing a resin such as polyvinyl alcohol or polyester is coated on an ink receiving layer so that the coating amount of a dry solid is 0.1 to 2.0 g / m ^2. It describes that glossiness and ink absorptivity can be compatible with each other.

JP 2000-108503 A

  However, according to the study by the present inventors, when a photo book is created using the recording medium described in Patent Document 1 and stored for 24 hours, a phenomenon in which white fog appears on the image may occur. there were. When this white haze is stored in a state in which the ink receiving layers having recorded images are in contact with each other as in a photo book, the movement of liquid components such as water and water-soluble organic solvents between the ink receiving layers in contact with each other. It occurs when it occurs. If this white haze occurs, it will not be visible in a high-quality glossy image.

  Accordingly, an object of the present invention is to provide a recording medium that can obtain an image having high gloss and suppressed white haze.

  The above object is achieved by the present invention described below. That is, the recording medium according to the present invention has a base material and an ink receiving layer in this order, and the arithmetic average roughness defined by JIS B 0601: 2001 is 1 on the surface of the recording medium having the ink receiving layer. The 60 degree specular gloss specified by JIS Z 8741 is 30% or more.

  According to the present invention, it is possible to provide a recording medium capable of obtaining an image with high glossiness and suppressed white haze.

It is a figure for demonstrating the major axis of the film | membrane in this invention.

  Hereinafter, the present invention will be described in detail with reference to preferred embodiments.

  As a result of studies by the present inventors, it has been found that in order to suppress white haze, it is necessary to reduce the contact area between the ink receiving layers of the recording medium. Therefore, when investigations were made using recording media having various surface roughnesses, the arithmetic average roughness (hereinafter referred to as “Ra”) defined by JIS B 0601: 2001 on the surface of the recording media was determined as follows. It was found that by setting the thickness to 3 μm or more, the contact area between the ink receiving layers of the recording medium can be reduced and white haze can be suppressed. However, when the surface of the recording medium becomes rough, the glossiness becomes low. Therefore, in order to obtain high image gloss as well as white haze suppression effect, in addition to satisfying the above condition of Ra, the 60-degree specular gloss of the surface of the recording medium defined by JIS Z 8741 It was found that it was necessary to set the content to 30% or more. Here, as an example of a method for setting the 60 ° specular glossiness of the surface of the recording medium to 30% or more, a method of setting Ra to 4.0 μm or less can be given. That is, Ra is preferably 1.3 μm or more and 4.0 μm or less. In order to adjust Ra to a desired value, a base material coated with resin (resin-coated base material) is used as a base material, and the surface is molded using rolls having various surface shapes. Is mentioned. Specifically, in order to make Ra within the above preferred range (1.3 μm or more and 4.0 μm or less), a resin-coated substrate is used, and Ra on the surface thereof is set to 1.5 μm or more and 5.0 μm or less. Was found to be preferable.

  Further investigation by the present inventors revealed that in order to obtain a higher level of glossiness and white haze suppression effect, the surface of the ink receiving layer is covered with a partial film formed of a plurality of films containing a resin. It was found that it was preferable. In addition to the effect of reducing the contact area between the ink receiving layers when the surface of the recording medium has a surface roughness Ra of 1.3 μm or more, the resin partial film is a liquid component between the ink receiving layers. Therefore, a higher white haze suppression effect is obtained. In addition, since the resin is present on the surface of the recording medium, it is easy to achieve the condition that the 60 ° specular glossiness of the surface of the recording medium is 30% or more, so that the glossiness of the image can be obtained at a high level. . In the present invention, the “partial film” is not a film continuously formed on the entire surface of the ink receiving layer, but is formed on the surface of the ink receiving layer and completely blocks the pores on the surface of the ink receiving layer. It means a film without any problems.

  In the present invention, the coverage of the ink receiving layer surface with the partial coating is preferably 30% or more and 70% or less, and more preferably 45% or more and 65% or less. If the coverage is greater than 70%, ink absorbability may not be sufficiently obtained. The coverage is a film on the entire surface of the ink receiving layer by image processing 10 observation images (size: 5.00 mm × 5.00 mm) using a scanning electron microscope (SEM). Calculated as the area ratio of the part. In the present invention, the surface of the ink receiving layer is preferably uniformly coated with a partial film. That is, when 10 places are observed using SEM, the coverage at 70% or more of them is more preferably 30% or more and 70% or less. Furthermore, it is particularly preferable that the coverage at all 10 locations observed using the SEM is 30% or more and 70% or less.

  As described above, the surface of the recording medium of the present invention has a Ra of 1.3 μm or more. Accordingly, there may be a concave portion and a convex portion on the surface of the recording medium. As will be described later, the partial film can be obtained by applying a coating liquid containing a resin to the ink receiving layer. However, since the coating liquid easily collects in the concave portion, the partial film is formed in the concave portion more than the convex portion. Easy to be. However, as described above, since the surface of the ink receiving layer is preferably uniformly coated with the partial film, it is preferable that the partial film is uniformly formed on the concave and convex portions of the ink receiving layer. Therefore, it is more preferable that the coverage of the concave portion of the ink receiving layer and the coverage of the convex portion are 30% or more and 70% or less. In addition, in this invention, when drawing the average line of a roughness curve, a recessed part and a convex part make a part above an average line a convex part, and let a part below an average line be a recessed part. And the coverage in a recessed part (convex part) is the recessed part covered with the film | membrane with respect to the whole area of the recessed part (convex part) of the surface of an ink receiving layer which performs image processing similarly to the calculation method of the above-mentioned coverage. It can be calculated as an area ratio of (convex part).

  As described above, the static surface tension of the coating liquid containing the resin is set to 20 mN / m or more and 30 mN / m or less in order to form a partial coating uniformly on the concave and convex portions of the ink receiving layer. It is preferable. By setting the amount within the above range, even when applied to the ink receiving layer, the film is appropriately expanded and is not excessively repelled, and a partial film is easily formed uniformly on the concave and convex portions of the ink receiving layer.

  In addition, in order to form a partial film uniformly on the concave portion and the convex portion of the ink receiving layer, the skewness (hereinafter referred to as “Rsk”) of the roughness curve defined by JIS B 0601: 2001 on the surface of the ink receiving layer. Is preferably 0.1 or less. The larger the Rsk is, the larger the volume of the concave portion with respect to the convex portion, so that the coating liquid easily flows into the concave portion, but the phenomenon that the coating liquid flows into the concave portion is suppressed by setting Rsk to 0.1 or less. Can do. Furthermore, Rsk on the surface of the ink receiving layer is more preferably 0 or less.

  Moreover, in this invention, it is preferable that the average major axis of the some membrane | film | coat which comprises a partial membrane | film | coat is 0.3 micrometer or more and 1.0 micrometer or less. In the present invention, the average major axis of the film means the maximum value of the length of a straight line connecting any two points of the outline of the film (L in FIGS. 1 (1) to (3)). The average major axis of the plurality of coatings constituting the partial coating is observed by SEM on the surface of the recording medium (the surface having the ink receiving layer), and the major axis of any of the ten coatings is measured. Calculated as the number average value.

[recoding media]
The recording medium of the present invention has a substrate and an ink receiving layer. In the present invention, an inkjet recording medium used in the inkjet recording method is preferable. Hereinafter, each component constituting the recording medium of the present invention will be described.

<Base material>
As a base material, what is comprised only from a base paper, and the thing which has a base paper and a resin layer, ie, the thing by which the base paper is coat | covered with resin, are mentioned. In the present invention, as described above, since it is easy to adjust the Ra of the surface of the recording medium to a desired value, it is preferable to use a base material (resin-coated base material) having a base paper and a resin layer. The resin layer may be provided only on the surface of the base paper on the ink receiving layer side, but is preferably provided on both surfaces.

  The base paper is made by using wood pulp as a main raw material and adding synthetic pulp such as polypropylene or synthetic fiber such as nylon or polyester as necessary. Wood pulp includes hardwood bleached kraft pulp (LBKP), hardwood bleached sulfite pulp (LBSP), softwood bleached kraft pulp (NBKP), softwood bleached sulfite pulp (NBSP), hardwood bleached pulp (LDP), coniferous melted pulp (NDP) ), Hardwood unbleached kraft pulp (LUKP), softwood unbleached kraft pulp (NUKP), and the like. These can use 1 type (s) or 2 or more types as needed. Among wood pulp, it is preferable to use LBKP, NBSP, LBSP, NDP, and LDP having a large amount of short fiber components. The pulp is preferably a chemical pulp (sulfate pulp or sulfite pulp) with few impurities. Moreover, the pulp which performed the bleaching process and improved the whiteness is also preferable. In the paper base material, a sizing agent, a white pigment, a paper strength enhancer, a fluorescent brightening agent, a moisture retention agent, a dispersing agent, a softening agent, and the like may be appropriately added.

The basis weight of the paper substrate is preferably 50 g / ^{m 2} or more 250 g / ^{m 2} or less, more, and more preferably 70 g / ^{m 2} or more 200 g / ^{m 2} or less. The thickness of the paper substrate is preferably 50 μm or more and 350 μm or less. The paper substrate may be calendered at the paper making stage or after paper making to improve smoothness. The paper density specified by JIS P 8118 is preferably 0.6 g / cm ³ or more and 1.2 g / cm ³ or less. The base paper stiffness specified by JIS P 8143 is preferably 20 g or more and 200 g or less. The pH of the paper substrate defined by JIS P 8113 is preferably 5 or more and 9 or less.

  In this invention, when a base material has a resin layer, it is preferable that the film thickness of a resin layer is 5 micrometers or more and 40 micrometers or less. Furthermore, it is more preferable that they are 8 micrometers or more and 35 micrometers or less. In the present invention, the thickness of the resin layer is calculated by the following method. First, a cross section of the recording medium is cut out with a microtome, and the cross section is observed with a scanning electron microscope. And the film thickness of arbitrary 100 points | pieces or more of a resin layer is measured, and let the average value be the film thickness of a resin layer. The film thicknesses of the other layers in the present invention are calculated by the same method.

  The resin used for the resin layer is preferably a thermoplastic resin. Examples of the thermoplastic resin include an acrylic resin, an acrylic silicone resin, a polyolefin resin, and a styrene-butadiene copolymer. Among these, it is preferable to use a polyolefin resin. In the present invention, the polyolefin resin means a polymer using olefin as a monomer. Specifically, homopolymers and copolymers such as ethylene, propylene, and isobutylene are exemplified. The polyolefin resin can use 1 type (s) or 2 or more types as needed. Among these, it is preferable to use polyethylene. As the polyethylene, it is preferable to use low density polyethylene (LDPE) or high density polyethylene (HDPE). The resin layer may contain a white pigment, a fluorescent brightening agent, ultramarine blue, and the like in order to adjust opacity, whiteness, and hue. Among them, it is preferable to contain a white pigment because opacity can be improved. Examples of the white pigment include rutile type or anatase type titanium oxide.

<Ink receiving layer>
In the present invention, the ink receiving layer is formed on at least one surface of the substrate. The ink receiving layer may be formed on both sides of the substrate. Although details will be described later, in the present invention, the ink receiving layer can be formed by coating an ink receiving layer coating solution on a substrate. The coating amount at that time is preferably 5 g / m ² or more and 50 g / m ² or less as a dry coating amount. When the coating amount is 5 g / m ² or more, the ink absorbency is high. When the coating amount is 50 g / m ² or less, drying at the time of forming the ink receiving layer is quick and productivity is high. Hereinafter, materials that can be contained in the ink receiving layer will be described.

(Inorganic particles)
In the present invention, the ink receiving layer preferably contains inorganic particles. As an inorganic particle, it is preferable that an average primary particle diameter is 1 nm or more. Moreover, it is preferable that an average primary particle diameter is less than 1 micrometer, and it is more preferable that it is 30 nm or less. In the present invention, the average primary particle diameter of the inorganic particles is the number average particle diameter of the diameter of a circle having an area equal to the projected area of the primary particles of the inorganic particles when observed with an electron microscope. At this time, at least 100 points are measured.

  In the present invention, the content (% by mass) of the inorganic particles in the ink receiving layer is preferably 50% by mass to 98% by mass, and more preferably 70% by mass to 96% by mass. Is more preferable.

In the present invention, the coating amount (g / m ² ) of the inorganic particles applied when forming the ink receiving layer is preferably 8 g / m ² or more and 45 g / m ² or less. By setting it within the above range, it is easy to obtain a preferable ink receiving layer thickness.

  Examples of the inorganic particles used in the present invention include alumina hydrate, alumina, silica, colloidal silica, titanium dioxide, zeolite, kaolin, talc, hydrotalcite, zinc oxide, zinc hydroxide, aluminum silicate, calcium silicate, and silicic acid. Examples thereof include magnesium, zirconium oxide, and zirconium hydroxide. These inorganic particles can be used alone or in combination of two or more as required. Among the inorganic particles, it is preferable to use alumina hydrate, alumina, or silica that can form a porous structure with high ink absorbability.

  In the present invention, it is particularly preferable to use alumina hydrate as the inorganic particles. The reason is as follows. White haze, which is one of the technical problems of the present invention, is more likely to occur as the amount of the binder in the ink receiving layer increases. This is because the binder easily retains liquid components such as water and water-soluble organic solvents, and the liquid components move between the binders. On the other hand, when alumina hydrate is used as the inorganic particles, the inorganic particles can be sufficiently bound and the ink receiving layer can be formed even if the amount of the binder is small. Therefore, when compared with the content of the same inorganic particles, the use of alumina hydrate as the inorganic particles makes it possible to reduce the amount of the necessary binder, thereby further suppressing the occurrence of white haze.

The alumina hydrate used in the ink receiving layer is
Formula _{(X): Al 2 O 3} -n (OH) 2n · mH 2 O
(In general formula (X), n is 0, 1, 2, or 3, m is 0 or more and 10 or less, preferably 0 or more and 5 or less. However, m and n are not 0 at the same time.)
What is represented by these can be used suitably. In many cases, mH ₂ O represents a detachable aqueous phase that does not participate in the formation of a crystal lattice, and therefore m may not be an integer. Also, m can be zero when the alumina hydrate is heated.

  In the present invention, the alumina hydrate can be produced by a known method. Specifically, a method of hydrolyzing aluminum alkoxide, a method of hydrolyzing sodium aluminate, a method of adding an aqueous solution of aluminum sulfate or aluminum chloride to an aqueous solution of sodium aluminate and neutralizing, and the like can be mentioned.

  As the crystal structure of the alumina hydrate, amorphous, kibsite type, and boehmite type are known depending on the heat treatment temperature, and any of these crystal structures can be used. In the present invention, among these, those showing boehmite type or amorphous by analysis by X-ray diffraction method are preferable. Specific examples include alumina hydrates described in JP-A-7-232473, JP-A-8-132731, JP-A-9-66664, JP-A-9-76628, and the like, as commercially available products. Examples include Dispersal HP14 (manufactured by Sasol) and Dispersal HP18 (manufactured by Sasol). These alumina hydrates can be used alone or in combination of two or more as required.

In the present invention, the specific surface area of the alumina hydrate determined by the BET method is preferably 100 m ² / g or more and 200 m ² / g or less, more preferably 125 m ² / g or more and 175 m ² / g or less. preferable. Here, the BET method is a method in which a specific surface area of a sample is measured from an adsorbed amount by adsorbing molecules and ions of a known size on the sample surface. In the present invention, nitrogen gas is used as the gas adsorbed on the sample.

  Examples of alumina used for the ink receiving layer include γ-alumina, α-alumina, δ-alumina, θ-alumina, and χ-alumina. Among these, it is preferable to use γ-alumina from the viewpoint of the optical density of the image and the ink absorbability. Specific examples include AEROXIDE Alu C (manufactured by EVONIK).

The alumina hydrate and alumina used in the present invention are preferably mixed in the ink receiving layer coating solution as an aqueous dispersion, and an acid is preferably used as the dispersant. As an acid,
Formula _{(Y): R-SO 3} H
(In the general formula (Y), R represents any of a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, and an alkenyl group having 1 to 3 carbon atoms. R represents an oxo group, a halogen atom, an alkoxy group, And may be substituted with an acyl group.)
It is preferable to use a sulfonic acid represented by the formula because an effect of suppressing image bleeding is obtained.

  The silica used for the ink receiving layer is generally roughly classified into a wet method and a dry method (gas phase method) depending on the production method. As a wet method, there is known a method in which active silica is produced by acid decomposition of silicate, and this is appropriately polymerized and coagulated and precipitated to obtain hydrous silica. On the other hand, as a dry method (gas phase method), a method using high-temperature gas phase hydrolysis of silicon halide (flame hydrolysis method) or silica sand and coke are heated and reduced and vaporized by an arc in an electric furnace. A method is known in which anhydrous silica is obtained by a method of oxidizing carbon with air (arc method). In the present invention, it is preferable to use silica obtained by a dry method (gas phase method) (hereinafter also referred to as “gas phase method silica”). This is because vapor-phase process silica has a particularly large specific surface area, so the ink absorbency is particularly high, and the refractive index is low, so that the receiving layer can be given transparency and good color development can be obtained. is there. Specifically, examples of the vapor phase method silica include Aerosil (manufactured by Nippon Aerosil), Leolosil QS type (manufactured by Tokuyama), and the like.

In the present invention, the specific surface area of the vapor phase silica by the BET method is preferably 50 m ² / g or more and 400 m ² / g or less, and more preferably 200 m ² / g or more and 350 m ² / g or less.

  In the present invention, the vapor phase silica is preferably used in the coating liquid for the ink receiving layer in a state where it is dispersed by a dispersant. The particle diameter of the vapor phase method silica in the dispersed state is more preferably from 50 nm to 300 nm. The particle diameter of the vapor phase silica in the dispersed state can be measured by a dynamic light scattering method.

  In the present invention, alumina hydrate, alumina and silica may be mixed and used. Specifically, a method of mixing and dispersing at least two kinds selected from alumina hydrate, alumina, and silica in a powder state to obtain a dispersion liquid can be mentioned.

(binder)
In the present invention, the ink receiving layer preferably contains a binder. In the present invention, the binder means a material that can bind inorganic particles to form an ink receiving layer.

  Examples of the binder include starch derivatives such as oxidized starch, etherified starch, and phosphate esterified starch; cellulose derivatives such as carboxymethyl cellulose and hydroxyethyl cellulose; casein, gelatin, soybean protein, polyvinyl alcohol (PVA), and derivatives thereof; Conjugated polymer latex such as polyvinylpyrrolidone, maleic anhydride resin, styrene-butadiene copolymer, methyl methacrylate-butadiene copolymer; acrylic polymer latex such as acrylic acid ester and methacrylic acid ester polymer; Vinyl polymer latex such as ethylene-vinyl acetate copolymer; functional group-modified polymer latex with a functional group-containing monomer such as carboxyl group of the above various polymers; Cationized body; Cationized surface of various polymers with cationic surfactant; Polymerized various polymers under cationic polyvinyl alcohol, and distributed polyvinyl alcohol on the surface of the polymer Polymers obtained by polymerizing the above-mentioned various polymers in a suspension dispersion of cationic colloidal particles and distributing the cationic colloidal particles on the surface of the polymer; Thermosetting synthetic resins such as melamine resin and urea resin Aqueous binders such as; Polymers and copolymer resins of methacrylic acid esters and acrylic acid esters such as polymethyl methacrylate; Synthetic resins such as polyurethane resins, unsaturated polyester resins, vinyl chloride-vinyl acetate copolymers, polyvinyl butyral, alkyd resins System binders and the like. These binders can use 1 type (s) or 2 or more types as needed.

  Among the binders described above, it is preferable to use polyvinyl alcohol or polyvinyl alcohol derivatives. Examples of the polyvinyl alcohol derivative include cation-modified polyvinyl alcohol, anion-modified polyvinyl alcohol, silanol-modified polyvinyl alcohol, and polyvinyl acetal.

  Polyvinyl alcohol can be synthesized, for example, by saponifying polyvinyl acetate. As a saponification degree of polyvinyl alcohol, 70 mol% or more and 100 mol% or less are preferable, and 85 mol% or more and 100 mol% or less are more preferable. The degree of saponification is the ratio of the number of moles of hydroxyl groups produced by the saponification reaction when polyvinyl alcohol is obtained by saponifying polyvinyl acetate. In the present invention, the value measured by the method of JIS-K6726. Shall be used. Moreover, 1,500 or more and 5,000 or less are preferable and, as for the average degree of polymerization of polyvinyl alcohol, 2,000 or more and 5,000 or less are more preferable. In the present invention, the average degree of polymerization is the viscosity average degree of polymerization determined by the method of JIS-K6726.

  When preparing a coating liquid for an ink receiving layer, it is preferable to use polyvinyl alcohol or a polyvinyl alcohol derivative as an aqueous solution. At that time, the content of the solid content of the polyvinyl alcohol and the polyvinyl alcohol derivative in the aqueous solution is preferably 3% by mass or more and 20% by mass or less.

  Further, the content of the binder with respect to the content of the inorganic particles in the ink receiving layer is preferably 5% by mass or more and 20% by mass or less. When the amount is less than 5% by mass, the binding force of the inorganic particles is weak and the ink receiving layer may become brittle. On the other hand, if it is more than 20% by mass, the effect of suppressing white haze may not be sufficiently obtained.

(Crosslinking agent)
In the present invention, the ink receiving layer preferably further contains a crosslinking agent. Examples of the crosslinking agent include aldehyde compounds, melamine compounds, isocyanate compounds, zirconium compounds, amide compounds, aluminum compounds, boric acid, and borate. These crosslinking agents can be used alone or in combination of two or more as required. In particular, when PVA is used as the binder, it is preferable to use boric acid and borates among the above-described crosslinking agents.

Examples of boric acid include orthoboric acid (H ₃ BO ₃ ), metaboric acid, and diboric acid. As the borate, the water-soluble salt of boric acid is preferable. Examples thereof include alkali metal salts of boric acid such as sodium salt and potassium salt of boric acid; alkaline earth metal salts of boric acid such as magnesium salt and calcium salt of boric acid; ammonium salt of boric acid and the like. Among these, orthoboric acid is preferably used from the viewpoint of the temporal stability of the coating solution.

  The amount of the crosslinking agent used can be appropriately selected according to production conditions and the like. It is preferably used in the range of 0.2 equivalents or more and 1.2 equivalents or less with respect to the binder content in the ink receiving layer. In addition, about said "equivalent", the quantity of the crosslinking agent which reacts completely with the quantity of the crosslinking group (in the case of PVA, a hydroxyl group) which a binder has theoretically shall be 1.0 equivalent.

  Furthermore, when the binder is polyvinyl alcohol and the crosslinking agent is at least one selected from boric acid and borate, boric acid and borate with respect to the content of polyvinyl alcohol in the ink receiving layer The total content of is preferably 2% by mass or more and 7% by mass or less.

(Other additives)
In the present invention, the ink receiving layer may contain other materials other than the materials described so far. Other additives include pH adjusters, thickeners, fluidity improvers, antifoaming agents, antifoaming agents, surfactants, mold release agents, penetrating agents, coloring pigments, coloring dyes, fluorescent whitening agents, Examples include ultraviolet absorbers, antioxidants, antiseptics, antifungal agents, water resistance agents, dye fixing agents, curing agents, and weather resistant materials.

<Partial film>
In the present invention, the surface of the ink receiving layer is preferably coated with a partial film formed of a plurality of films containing a resin. In addition to the resin, the partial film may further contain inorganic particles and other additives exemplified in the above <ink receiving layer>.

  Examples of the resin contained in the partial coating include polyvinyl alcohol, polyvinyl pyrrolidone, polyurethane, polyester, polystyrene, polyvinyl acetate, polyacrylamide, cellulose, acrylic resin, melamine resin, and urea resin. These can use 1 type (s) or 2 or more types as needed. Among these resins, it is preferable to use polyurethane.

  The resin is preferably used in the form of resin particles. In this case, the average particle diameter of the resin particles is preferably 0.01 μm or more and 0.10 μm or less. The weight average molecular weight of the resin is preferably 1,000 or more and 200,000 or less, and more preferably 2,000 or more and 50,000 or less.

[Method of manufacturing recording medium]
<Method for producing substrate>
In the recording medium of the present invention, a commonly used paper preparation method can be applied as a base material preparation method. Examples of the paper machine include a long net paper machine, a round net paper machine, a cylinder, and a twin wire. Examples of the method of coating the substrate with a resin include a method of extruding and coating a molten resin on one or both sides of the substrate. Furthermore, the uneven | corrugated pattern of desired surface roughness can be given by pressing the roll etc. which have an unevenness | corrugation to the base material coat | covered with resin. Examples of the method for forming the concavo-convex pattern include a method of embossing calendering after coating a resin, and a method of cooling while pressing a cooling roll having irregularities on the surface during coating of the resin. The latter method is preferable because a more accurate and uniform uneven pattern can be applied with a weak pressure.

<Method for forming ink receiving layer>
In the recording medium of the present invention, examples of the method for forming the ink receiving layer on the substrate include the following methods. First, an ink receiving layer coating solution is prepared. And an ink receiving layer can be formed by apply | coating and drying the said coating liquid on a base material. As a coating method of the coating liquid, a curtain coater, a coater using an extrusion method, a coater using a slide hopper method, or the like can be used. In addition, you may heat a coating liquid at the time of coating. In addition, as a drying method after coating, a method using a hot air dryer such as a straight tunnel dryer, an arch dryer, an air loop dryer, a sine curve air float dryer, an infrared ray, a heated dryer, a microwave, or the like was used. Examples include a method using a dryer.

<Formation method of partial film>
In the recording medium of the present invention, examples of the method for coating the surface of the ink receiving layer with a partial film include the following methods. First, a coating liquid (resin coating liquid) containing a resin for partial coating is prepared. Then, at the same time as applying the ink receiving layer coating liquid, a method of applying the resin coating liquid and drying both simultaneously, or applying and drying the ink receiving layer coating liquid In addition, a method of applying a resin coating solution is also included. The latter method is more preferable because the ink receiving layer and the partial film can be prevented from mixing.

In addition, in order for the coverage of the ink receiving layer surface by the partial coating to be 30% or more and 70% or less, the coating amount of the resin coating solution is 0.01 g / m ² or more of the dry solid content of resin. 10 g / m ² or less is preferable.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. The present invention is not limited in any way by the following examples as long as the gist thereof is not exceeded. In the description of the following examples, “part” is based on mass unless otherwise specified.

[Production of recording medium]
<Preparation of base material>
100 parts of hardwood bleached kraft pulp, 2 parts of cationized starch, 20 parts of light calcium carbonate, and 0.3 parts of an alkenyl succinic anhydride neutral sizing agent are mixed to make a papermaking raw material. Moisture was dried to 10% by weight, and a 7% by weight solution of oxidized starch was applied at 4 g / m ² on both sides with a size press, dried, and the moisture was dried to 7% by weight to prepare a base paper having a basis weight of 110 g / m ^2. Produced.

Next, on both sides of the base paper, a resin composition comprising 70 parts of low density polyethylene and 20 parts of high density polyethylene is cooled immediately after being melt-extruded and applied so that the dry coating amount is 30 g / m ^2. Then, the molding process was performed using cooling rolls having various surface shapes. Then, base materials A to H having a basis weight of 170 g / m ² were prepared. Ra and Rsk of each obtained base material were measured according to JIS B0601: 2001, using a surface roughness meter Surfcorder SE3500 (manufactured by Kosaka Laboratory). The results are shown in Table 1.

<Preparation of coating solution for ink receiving layer>
(Ink-receiving layer coating solution 1)
In ion-exchanged water, alumina hydrate DISPERAL HP14 (manufactured by Sasol) was added so that the solid content was 30% by mass. Next, 1.5 parts of methanesulfonic acid is added to 100 parts of the solid content of alumina hydrate and stirred, and the solid content of the alumina hydrate is 27% by mass. Ion exchange water was added to obtain an alumina particle dispersion. Next, this alumina particle dispersion, an aqueous polyvinyl alcohol solution (an aqueous solution having a solid content of 8% by mass of PVA235 (manufactured by Kuraray) having a polymerization degree of 3,500 and a saponification degree of 88 mol%), and boric acid An aqueous solution (solid content is 3% by mass) is mixed so that the solid content ratio (alumina particles: polyvinyl alcohol: boric acid) is 100: 10: 2, and the ink receiving layer coating solution 1 Got.

(Ink-receiving layer coating solution 2)
Gas phase method silica A300 (manufactured by Nippon Aerosil Co., Ltd.) was added to ion-exchanged water so that the solid content was 22% by mass. Next, 4 parts of the cationic polymer Charol DC902P (Daiichi Kogyo Seiyaku Co., Ltd.) is added to 100 parts of the solid content of the vapor phase method silica and stirred, and the solid content of the vapor phase method silica is 18 masses. % Ion-exchanged water was added to obtain a silica particle dispersion. Then, this silica particle dispersion, polyvinyl alcohol aqueous solution (aqueous solution in which the solid content of PVA235 (manufactured by Kuraray) having a polymerization degree of 3,500 and a saponification degree of 88 mol% is 8% by mass), and boric acid An aqueous solution (solid content is 3% by mass) is mixed so that the solid content ratio (silica particles: polyvinyl alcohol: boric acid) is 100: 20: 3.5, and coating for the ink receiving layer is performed. Liquid 2 was obtained.

<Preparation of resin coating solution>
The resin dispersion and the surfactant were mixed so as to have a solid content ratio shown in Table 2 below, and stirred to prepare each resin coating solution. About each obtained resin coating liquid, static surface tension was measured with automatic surface tension meter CBVP-Z (made by Kyowa Interface Chemical). The results are shown in Table 2.

In addition, the kind of resin dispersion liquid and surfactant in Table 2 is described by trade names. Details of each are as follows.
(Resin dispersion)
Superflex 620 (Daiichi Kogyo Seiyaku): dispersion of cationic polyurethane resin particles Smarttex PA-3232: dispersion of styrene-butadiene rubber latex particles (surfactant)
Neugen TDS-70 (Daiichi Kogyo Seiyaku): Polyoxyethylene tridecyl ether Surfynol 440 (Nisshin Chemical Industries): Acetylene glycol polyoxyethylene adduct Surflon S-241 (AGC Seimi Chemical): Fluorosurfactant

<Preparation of recording medium>
With the combinations shown in Table 3, the ink receiving layer coating solution was applied to the substrate so that the film thickness after drying was 35 μm, and then dried at 60 ° C. to form an ink receiving layer on the substrate. Next, a resin coating liquid is overcoated on the formed ink receiving layer using a Mayer bar so that the dry coating amount of the resin becomes a value shown in Table 3, and then dried at 60 ° C. for 20 minutes to obtain a recording medium. Got. Ra and Rsk of the obtained recording medium were measured according to JIS B0601: 2001 using a surface roughness meter Surfcorder SE3500 (manufactured by Kosaka Laboratory). Further, the 60-degree specular gloss of the obtained recording medium was measured according to JIS Z 8741 using a gloss meter VG-2000 (manufactured by Nippon Denshoku Industries Co., Ltd.). Moreover, the average major axis and coverage of the partial coating were calculated by the above-described method. The results are shown in Table 3.

<Evaluation>
In the present invention, A and B of the following evaluation items were set as preferable levels, and C was set as an unacceptable level. In the following evaluations, when an image was recorded on a recording medium, the ink jet recording apparatus was recorded by mounting an ink cartridge BCI-321 (made by Canon) on PIXUS MP990 (made by Canon). The recording conditions at that time were temperature: 23 ° C. and relative humidity: 50%. In the ink jet recording apparatus, an image recorded under the condition of applying a drop of about 11 ng of ink to a unit area of 1/600 inch × 1/600 inch with a resolution of 600 dpi × 600 dpi has a recording duty of 100%. Is defined as

(Glossy)
An arbitrary photographic image was recorded on the recording medium in the glossy proplatinum grade mode (standard setting, color / density: no matching) using the above-described inkjet recording apparatus, and visually evaluated. The evaluation criteria are as follows. The evaluation results are shown in Table 4.
A: It had a gloss with a high-class feeling B: It had a gloss with a certain level of luxury C: It did not have a gloss with a high-class feeling.

(White haze suppression effect)
Using the inkjet recording apparatus described above, a 15 cm × 15 cm area in the glossy proplatinum grade mode (standard setting, color / density: no matching) in the RGB mode of PhotoShop 7.0 (R, G , B) = Image 0 filled with (0,0,0) and a 5 cm × 5 cm region are filled with (R, G, B) = (255,255,0) in the RGB mode of PhotoShop 7.0. Two images, Y image Y, were recorded. After recording, the film was dried for 10 minutes in an environment of a temperature of 23 ° C. and a relative humidity of 50%, superimposed so that the image X and the image Y overlapped, and stored for 24 hours. Then, the area | region which overlapped with the image Y of the image X was compared visually, and the area | region which did not overlap was evaluated, and the white haze suppression effect was evaluated. The evaluation criteria are as follows. The evaluation results are shown in Table 4.
A: No significant difference was observed B: A white haze was slightly confirmed in the area of the image X that overlapped the image Y. C: A white haze in the area of the image X that overlapped the image Y Was clearly confirmed.

(Ink absorption)
Two solid green images with a recording duty of 200% and 300% were recorded on the recording medium using the inkjet recording apparatus. The ink absorptivity was evaluated by visually confirming whether or not the beading phenomenon occurred in the obtained image. The beading phenomenon is a phenomenon in which ink droplets before being absorbed by the recording medium are combined, and is known to have a high correlation with ink absorbability. If a beading phenomenon does not occur even in an image with a high recording duty, it can be determined that the ink absorbency is high. The evaluation criteria are as follows. The evaluation results are shown in Table 4.
A: A beading phenomenon did not occur even in an image with a recording duty of 300%. B: A beading phenomenon occurred in an image with a recording duty of 300%, but it did not occur in a 200% image. : The beading phenomenon occurred even in an image with a recording duty of 200%.

Claims (5)

A recording medium having a base material and an ink receiving layer in this order,
The arithmetic average roughness specified by JIS B 0601: 2001 on the ink receiving layer side surface of the recording medium is 1.3 μm or more, and the 60 ° specular gloss specified by JIS Z 8741 is 30%. A recording medium characterized by the above. The surface of the ink receiving layer is coated with a plurality of films containing a resin,
The average major axis of the plurality of films is 0.3 μm or more and 1.0 μm or less,
The recording medium according to claim 1, wherein a coverage of the surface of the ink receiving layer by the plurality of films is 30% or more and 70% or less.   The recording medium according to claim 2, wherein the resin contains polyurethane.   4. The recording medium according to claim 1, wherein an arithmetic average roughness defined by JIS B 0601: 2001 on the surface of the recording medium on the ink receiving layer side is 4.0 μm or less. 5. A resin layer is further provided between the base material and the ink receiving layer,
5. The recording according to claim 1, wherein an arithmetic average roughness defined by JIS B 0601: 2001 on a surface of the resin layer on the ink receiving layer side is 1.5 μm or more and 5.0 μm or less. Medium.