JP2019081325A - Recording medium - Google Patents

Abstract

To provide a recording medium that has a matte feel and is excellent in touch feel.SOLUTION: The recording medium is a recording medium having a substrate and a first ink receiving layer in which a root-mean-square slope RΔq of a roughness curve element of the surface of the recording medium is 0.30 or more as well as an arithmetic mean roughness Ra is 0.90 μm or less.SELECTED DRAWING: None

Description

  The present invention relates to a recording medium.

  Among recording media used in the inkjet image recording method, there are recording media with high surface quality (also called matte paper) having a so-called "mat feeling", in which the surface glossiness is suppressed. In general, matte paper is developed by providing an ink receiving layer containing inorganic particles having a particle size of micron order. Patent Document 1 discloses a recording medium mainly containing inorganic fine particles having an average secondary particle diameter of 1 to 10 μm in the uppermost layer.

JP 2005-231295 A

  In recent years, the demand for a photo album using an ink jet recording medium is increasing, and in the photo album application, development of a recording medium excellent in touch feeling (smooth feeling) on the surface of the recording medium is also desired. However, according to the study of the present inventors, in the recording medium described in Patent Document 1, the matte feeling could be expressed by providing the uppermost layer containing the inorganic fine particles having an average secondary particle diameter of 1 to 10 μm. However, the feel was not enough. Therefore, an object of the present invention is to provide a recording medium having a matte feeling and having an excellent surface touch feeling.

  The above object is achieved by the present invention described below.

  That is, the recording medium according to the present invention is a recording medium having a substrate and a first ink receiving layer, and the root mean square slope RΔq of the roughness curvilinear element on the surface of the recording medium is 0. 30 or more and arithmetic mean roughness Ra of 0.90 μm or less.

  According to the present invention, it is possible to provide a recording medium having a matte feeling and having an excellent surface touch feeling.

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

  First, the "mat feeling" in the present invention will be described. The recording medium having a matte feeling means a recording medium having a small surface reflection and a small glossiness from any angle. More specifically, it means a recording medium having a surface 20 ° glossiness, 60 ° glossiness and 75 ° glossiness of 6.0% or less.

  In matte paper, it is necessary to increase light scattering on the surface of the recording medium to suppress surface reflection, and therefore, it is general to use inorganic particles having a large particle diameter as described in Patent Document 1. On the other hand, by using inorganic particles having a large particle diameter, the touch feeling of the recording medium sometimes decreases. Here, the sense of touch in the present invention means the degree of finger catching when sliding the finger on the recording medium surface. When the present inventors examined the reduction in the feeling of touch, it was found that the feeling of touch was highly correlated with the arithmetic mean roughness Ra of the recording medium surface. That is, it is considered that the arithmetic mean roughness Ra of the surface of the recording medium is increased due to the inorganic particles having a large particle diameter and the rough surface of the substrate used to obtain the matte feeling, and the touch feeling is lowered.

  Therefore, the present inventors first studied to reduce the arithmetic mean roughness of the surface of the recording medium in order to improve the touch feeling. Then, the present inventors have found that the arithmetic average roughness Ra defined by JIS B 0601: 2001 on the surface of the recording medium needs to be 0.90 μm or less in order to improve the touch feeling. Further, in order to further improve the touch feeling of the recording medium, the arithmetic average roughness Ra of the surface of the recording medium is preferably 0.85 μm or less. The lower limit value of the arithmetic average roughness Ra of the surface of the recording medium is not particularly limited, but for example, 0.35 μm or more is preferable.

  Furthermore, the present inventors further examined the relationship between the surface roughness of the recording medium and the matte feeling in order to obtain the matte feeling while reducing the Ra of the surface of the recording medium.

  As a result, it was found that the root mean square slope RΔq of the roughness curvilinear element defined in JIS B 0601: 2001 needs to be 0.30 or more in order to obtain a matte feeling. The RΔq represents the degree of inclination of the asperities, and a large value means that the asperities are steep. A matte feeling can be obtained by such surface shape, because the steeper the unevenness, the easier it is for the incident light to be scattered, and the light quantity in the regular reflection direction is reduced. The upper limit of RΔq on the surface of the recording medium is not particularly limited, but is preferably 0.80 or less, for example.

  As described above, in order to obtain a recording medium having a matte feeling and an excellent surface touch feeling, the inventors of the present invention can calculate the root mean square slope RΔq of the surface roughness curve element of the recording medium; It has been found that it is important to adjust the arithmetic mean roughness Ra to a specific range, leading to the present invention.

  There is no particular limitation on the method of adjusting the root mean square slope RΔq of the surface roughness curve element of the surface of the recording medium and the arithmetic average roughness Ra to a specific range as in the present invention. According to the study of the present inventors, it is preferable to adjust RΔq and Ra to a specific range by controlling the shape of the substrate surface, for example, in addition to controlling the size of particles used in the ink receiving layer . In particular, the substrate has an arithmetic mean roughness Ra of 0.20 μm or less, and the first ink receiving layer contains amorphous silica having an average particle diameter of 2.0 μm or more and 14.0 μm or less. Is preferred. Further, the product of the arithmetic mean roughness Ra of the base material and the mean particle size of the amorphous silica contained in the first ink receiving layer at this time is 0.12 or more and 1.80 or less. Is preferable and it is more preferable to set it as 0.20 or more and 1.50 or less.

[recoding media]
The recording medium of the present invention has a substrate and a first ink receiving layer. In addition, a second ink receiving layer may be provided between the first ink receiving layer and the substrate, or a surface protective layer may be provided on the first ink receiving layer. Also, another layer may be provided between the second ink receiving layer and the substrate. In the present invention, the recording medium used in the ink jet recording method, that is, the recording medium for ink jet recording is preferable. Hereinafter, each component which comprises the recording medium of this invention is each demonstrated.

<Base material>
Examples of the substrate include those composed of only base paper, and those having base paper and a resin layer, that is, those in which base paper is coated with a resin. In the present invention, it is preferable to use a substrate having a base paper and a resin layer, that is, a resin-coated substrate. In that case, the resin layer may be provided only on one side of the base paper, but is preferably provided on both sides.

  The base paper is mainly made of wood pulp, and is optionally made by adding synthetic pulp such as polypropylene and synthetic fibers such as nylon and polyester. As wood pulp, hardwood bleached kraft pulp (LBKP), hardwood bleached sulfite pulp (LBSP), softwood bleached kraft pulp (NBKP), softwood bleached sulfite pulp (NBSP), hardwood dissolving pulp (LDP), softwood dissolving pulp (NDP) ), Hardwood unbleached kraft pulp (LUKP), softwood unbleached kraft pulp (NUKP) and the like. These may be used alone or in combination of two or more. Among wood pulps, it is preferable to use LBKP, NBSP, LBSP, NDP, and LDP, which have many short fiber components. As the pulp, chemical pulp (sulfate pulp and sulfite pulp) with few impurities is preferable. Also preferred is a pulp which has been bleached to improve its whiteness. In the paper substrate, a sizing agent, a white pigment, a paper strengthening agent, a fluorescent whitening agent, a water retention agent, a dispersing agent, a softening agent and the like may be appropriately added.

In the present invention, the paper density of the base paper defined by JIS P 8118 is preferably 0.6 g / cm ³ or more and 1.2 g / cm ³ or less. More preferably, it is 0.7 g / cm ³ or more and 1.2 g / cm ³ or less.

  In the present invention, when the substrate has a resin layer, the thickness of the resin layer is preferably 10 μm or more and 60 μm 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 thickness of 100 arbitrary points or more of a resin layer is measured, and let the average value be the thickness of a resin layer. The thicknesses of other layers in the present invention are also calculated by the same method.

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

  In the present invention, the arithmetic average roughness Ra defined by JIS B 0601: 2001 on the surface of the base on the ink receiving layer side is preferably 0.20 μm or less. By setting the arithmetic average roughness Ra of the surface of the substrate on the ink receiving layer side to 0.20 μm or less, a recording medium having a surface RΔq of 0.30 or more and an Ra of 0.90 μm or less is obtained. It will be easier.

<Ink receiving layer>
In the present invention, the ink receiving layer may be provided on only one side of the above substrate, or may be provided on both sides. The thickness of the ink receiving layer is preferably 18 μm or more and 55 μm or less. In the present invention, the ink receiving layer may be two layers or a multilayer of three or more layers.

In the present invention, dry coating amount of the ink receiving layer, it is preferably, 8.0 g / ^{m 2} or more 40.0 g / ^{m 2} or less is 7.0 g / ^{m 2} or more 45.0 g / ^{m 2} or less Is more preferred. The dry coating amount of the ink receiving layer as referred to herein means the total dried coating amount of all the layers when the ink receiving layer is a multilayer. Hereinafter, materials which can be contained in the ink receiving layer will be respectively described.

(First ink receiving layer)
In the present invention, the thickness of the first ink receiving layer is preferably 1 μm or more and 40 μm or less, and more preferably 5 μm or more and 35 μm or less.

(1) Amorphous Silica In the present invention, the first ink receiving layer preferably contains amorphous silica in order to improve the matte feeling of the recording medium. Amorphous silica is particles containing 93% or more of SiO _2, about 5% or less of Al ₂ O _{3, and} about 5% or less of Na ₂ O by dry weight, so-called white carbon, silica gel or porous synthetic amorphous There is silica etc. Methods for producing porous synthetic amorphous silica are roughly classified into dry methods and wet methods, and there are combustion methods and heating methods in dry methods. In addition, there are manufacturing methods called precipitation method and gel method in the wet method. The dry combustion method is generally called a gas phase method in which a mixture of vaporized silicon tetrachloride and hydrogen is burned in air at 1,600 to 2,000 ° C. The wet precipitation method is usually a method in which sodium silicate and sulfuric acid are reacted in an aqueous solution to precipitate SiO ₂ , and the specific surface area or primary particle diameter of silica is adjusted according to the conditions such as the reaction temperature and the addition rate of acid. can do. In addition, the secondary particle diameter and the physical properties of silica slightly change under drying and pulverizing conditions. The wet gel method is generally produced by reacting by simultaneous addition of sodium silicate and sulfuric acid, etc. In the case of silica particles, for example, dehydration condensation of silanol groups proceeds to form a three-dimensional hydrogel structure. is there. The feature is that the primary particles have a relatively small hydrogel structure, so that secondary particles having a large specific surface area can be produced, and the size of the primary particle diameter is adjusted by changing the reaction conditions etc. Secondary particle size can be produced. In the present invention, one type of amorphous silica may be contained, or two or more types of amorphous silica may be contained. In the present invention, the amorphous silica is preferably a wet process silica. Moreover, you may further contain inorganic particles other than amorphous silica.

  In the present invention, the average particle diameter of the amorphous silica contained in the ink receiving layer is preferably 2.0 μm or more and 14.0 μm or less, and more preferably 2.0 μm or more and 9.0 μm or less. The average particle diameter in the present invention means the average value of the diameter of the largest unit of particles recognized as particles when the cross section of the recording medium is observed with a scanning electron microscope (SEM). More specifically, it can be obtained by observing the cross section of the recording medium with a scanning electron microscope (SEM), measuring the diameter of 100 arbitrary particles, and calculating the number average. In the case of amorphous silica, secondary particles formed by association of primary particles are observed, so the above “average particle diameter of amorphous silica” means “average secondary particle diameter of amorphous silica. Means ". By the average particle diameter of the amorphous silica being in the above-mentioned range, it is possible to achieve both the matte feeling and the feel at a high level.

  The content of amorphous silica in the first ink receiving layer is preferably 50% by mass or more and 100% by mass or less based on the total mass in the first ink receiving layer, and is 60% by mass or more It is more preferable that it is 100 mass% or less.

(2) Inorganic particles having an average particle diameter of 50 nm or less In the present invention, the first ink receiving layer may contain inorganic particles having an average particle diameter of 50 nm or less (hereinafter, also simply referred to as “inorganic particles A”). The average particle diameter of the inorganic particles A is preferably 1 nm or more and 50 nm or less, more preferably 3 nm or more and 30 nm or less, and particularly preferably 5 nm or more and 20 nm or less. In the present invention, the "average particle size of the inorganic particles A" means "average primary particle size of the inorganic particles A".

  In the present invention, the inorganic particles A are preferably used in a coating liquid for an ink receiving layer in a state of being dispersed by a dispersing agent. The average secondary particle diameter of the inorganic particles A in the dispersed state is preferably 1 nm or more and 1000 nm or less, more preferably 10 nm or more and 800 nm or less, and particularly preferably 50 nm or more and 500 nm or less. The average secondary particle diameter of the inorganic particles A in the dispersed state can be measured by a dynamic light scattering method.

  In the present invention, the content (% by mass) of the inorganic particles A in the first ink receiving layer is 2% by mass or more and 40% by mass or less based on the total mass of the inorganic particles in the first ink receiving layer. Is preferred.

  As the inorganic particles A used in the present invention, for example, alumina hydrate, alumina, silica, colloidal silica, titanium dioxide, zeolite, kaolin, talc, hydrotalcite, zinc oxide, zinc hydroxide, aluminum silicate, calcium silicate, Magnesium silicate, zirconium oxide, zirconium hydroxide and the like can be mentioned. These inorganic particles A can be used alone or in combination of two or more. Among the inorganic particles A, it is preferable to use alumina hydrate, alumina or silica capable of forming a porous structure having high ink absorbability, and alumina hydrate is more preferable.

The alumina hydrate used in the first ink receiving layer is
General formula (X): Al ₂ O _3-n (OH) _{2 n} · mH ₂ O
(In the general formula (X), n is 0, 1, 2, or 3 and m is 0 or more and 10 or less, preferably 0 or more and 5 or less. However, m and n do not simultaneously become 0.)
What is represented by can be used suitably. Note that m does not have to be an integer, as mH ₂ O often represents a removable aqueous phase that does not contribute to the formation of a crystal lattice. In addition, m can be 0 when the alumina hydrate is heated.

  In the present invention, 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 and aluminum chloride to an aqueous solution of sodium aluminate, and the like can be mentioned.

  As the crystal structure of alumina hydrate, an amorphous, a gibbsite type, and a boehmite type are known according to the temperature to be heat-treated. The crystal structure of alumina hydrate can be analyzed by X-ray diffraction. In the present invention, among these, boehmite-type alumina hydrate or amorphous alumina hydrate is preferable. As specific examples, alumina hydrates described in JP-A-7-232473, JP-A-8-132731, JP-A-9-66664, JP-A-9-76628, etc., or as a commercial product Examples include Disperal HP14, HP18 (all manufactured by Sasol), and the like. These alumina hydrates can be used alone or in combination of two or more as needed.

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, and more preferably 125 m ² / g or more and 175 m ² / g or less. preferable. Here, the BET method is a method of adsorbing molecules or ions whose size is known on the surface of a sample and measuring the specific surface area of the sample from the amount of adsorption. In the present invention, nitrogen gas is used as a gas to be adsorbed to the sample.

The alumina hydrate and alumina used in the present invention are preferably mixed in the coating liquid for the ink receiving layer as a water dispersion, and it is preferable to use an acid as the dispersant. As an acid,
General formula (Y): R-SO ₃ H
(In general formula (Y), R represents a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or an alkenyl group having 1 to 3 carbon atoms. R represents an oxo group, a halogen atom, an alkoxy group, And may be substituted by an acyl group)
It is preferable to use a sulfonic acid represented by the following formula, because the effect of suppressing image blurring can be obtained.

  The silica as the inorganic particles A used in the first ink receiving layer is preferably a dry method (gas phase method). As a dry method (gas phase method), a method by high temperature vapor phase hydrolysis of silicon halide (flame hydrolysis method), silica sand and coke are heated, reduced and vaporized by an arc in an electric furnace, and this is air There is known a method of obtaining anhydrous silica by a method of oxidizing with (arc method). In the present invention, it is preferable to use silica (hereinafter, also referred to as "gas phase silica") obtained by a dry method (gas phase method). This is because fumed silica has a particularly large specific surface area, so the ink absorbability is particularly high, and since the refractive index is low, transparency can be imparted to the ink receiving layer, and good color development can be obtained. It is. Specifically, examples of the gas phase silica include Aerosil (manufactured by Nippon Aerosil), Leorosil QS type (manufactured by Tokuyama), and the like.

In the present invention, the specific surface area of the fumed silica by 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, alumina hydrate, fumed silica and the like may be used as a mixture. Specifically, there is a method of mixing and dispersing two kinds in a powder state to make a dispersion.

(3) Binder In the present invention, the ink receiving layer preferably further contains a binder. In the present invention, a binder means a material capable of binding inorganic particles.

  In the present invention, the content of the binder in the ink receiving layer is preferably 5.0% by mass or more and 50.0% by mass or less, based on the content of the amorphous silica, and 8.0% by mass. It is more preferable that it is% or more and 45.0 mass% or less. When the content of the binder is in the above-mentioned range, it is possible to achieve both suppression of the occurrence of so-called powder dropping phenomenon in which the inorganic particles are detached from the ink receiving layer, and high ink absorptivity.

  As the binder, for example, starch derivatives such as oxidized starch, etherified starch, phosphated starch and the like; cellulose derivatives such as carboxymethyl cellulose and hydroxyethyl cellulose; casein, gelatin, soybean protein, and polyvinyl alcohol, and derivatives thereof Conjugated polymer latexes such as pyrrolidone, maleic anhydride resin, styrene-butadiene copolymer, methyl methacrylate-butadiene copolymer; acrylic polymer latexes such as polymers of acrylic acid ester and methacrylic acid ester; ethylene-vinyl acetate Vinyl polymer latex such as copolymer; functional modified polymer latex by functional group-containing monomer such as carboxyl group of the above polymer; latex obtained by cationizing the polymer using cationic group; Those obtained by cationizing the surface of the above polymer using a thionic surfactant; those obtained by polymerizing the monomers constituting the above polymer under cationic polyvinyl alcohol and distributing polyvinyl alcohol on the surface of the polymer; cationic Obtained by polymerizing the monomers constituting the above-mentioned polymer in the suspension dispersion liquid of anionic colloid particles and distributing the cationic colloid particles on the surface of the polymer; aqueous materials such as thermosetting synthetic resins such as melamine resin and urea resin Binders; polymers and copolymers of acrylic acid esters such as polymethyl methacrylate and methacrylic acid esters; and synthetic resins such as polyurethane resins, unsaturated polyester resins, vinyl chloride-vinyl acetate copolymers, polyvinyl butyral, alkyd resins etc. Be These binders may be used alone or in combination of two or more as needed.

  Among the above-mentioned binders, polyvinyl alcohol and polyvinyl alcohol derivatives are preferably used. As polyvinyl alcohol derivatives, cation modified polyvinyl alcohol, anion modified polyvinyl alcohol, silanol modified polyvinyl alcohol, polyvinyl acetal etc. are mentioned. Among the above, polyvinyl alcohol is particularly preferable from the viewpoint of the binding property to amorphous silica. As a specific example of polyvinyl alcohol, PVA235 (made by Kuraray) etc. can be mentioned.

  Polyvinyl alcohol can be synthesized, for example, by saponifying polyvinyl acetate. As a saponification degree of polyvinyl alcohol, 80 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 saponifying polyvinyl acetate to obtain polyvinyl alcohol, and in the present invention, the value measured by the method of JIS-K6726 Shall be used. In addition, the average degree of polymerization of polyvinyl alcohol is preferably 1,500 or more and 5,000 or less, and more preferably 2,000 or more and 5,000 or less. In the present invention, as the average degree of polymerization, the viscosity average degree of polymerization determined by the method of JIS-K 6726 is used.

  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. In that case, as for content of solid content of polyvinyl alcohol in aqueous solution, and a polyvinyl alcohol derivative, 3 mass% or more and 20 mass% or less are preferable.

(4) Other Additives In the present invention, the first ink receiving layer may contain other additives other than those described above. Specifically, pH adjusters, thickeners, flow improvers, antifoamers, foam inhibitors, surfactants, mold release agents, penetrants, color pigments, color dyes, fluorescent brighteners, ultraviolet light absorption Agents, antioxidants, preservatives, mildew proofing agents, water proofing agents, dye fixing agents, curing agents, weathering materials and the like.

(Second ink receiving layer)
In the present invention, the recording medium preferably has a second ink receiving layer between the substrate and the first ink receiving layer. The thickness of the second ink receiving layer is preferably 3 μm or more and 55 μm or less. By providing the second ink receiving layer having higher transparency, the light transmittance of the entire receiving layer is improved, so that the color development of the printed matter can be improved.

(1) Inorganic Particles In the present invention, the second ink receiving layer preferably contains inorganic particles having an average particle diameter of 50 nm or less similar to the above first ink receiving layer. Among the above-mentioned inorganic particles, it is preferable to use alumina hydrate, alumina or silica capable of forming a porous structure having high ink absorbability, and alumina hydrate is more preferable.

  The content of the inorganic particles in the second ink receiving layer is preferably 60% by mass or more and 95% by mass or less based on the total mass of the second ink receiving layer.

(2) Binder In the present invention, the second ink receiving layer preferably further contains a binder.

  In the present invention, from the viewpoint of ink absorbability, the content of the binder in the first ink receiving layer is 3.0% by mass or more and 30.0% by mass or less with respect to the content of the inorganic particles. Is preferable, and it is more preferable that it is 5.0 mass% or more and 25.0 mass% or less.

  As the binder, the same ones as exemplified in the above-mentioned first ink receiving layer can be used. Among them, polyvinyl alcohol is preferable as a binder used for the second ink receiving layer.

(3) Crosslinking Agent In the present invention, the second ink receiving layer preferably further contains a crosslinking agent. By containing a crosslinking agent, it is possible to prevent cracking of the receptive layer in the manufacturing process, and to improve the absorbency of the printing ink.

  The content of the crosslinking agent in the second ink receiving layer is preferably 1% by mass to 60% by mass, and more preferably 5% by mass to 50% by mass, based on the content of the binder.

  Examples of the crosslinking agent include aldehyde compounds, melamine compounds, isocyanate compounds, zirconium compounds, amide compounds, aluminum compounds, boric acid, and boric acid salts. These crosslinking agents can be used alone or in combination of two or more. When using a polyvinyl alcohol or a polyvinyl alcohol derivative as a binder especially, it is preferable to use a boric acid and a borate among the above-mentioned crosslinking agents.

Examples of boric acid include orthoboric acid (H ₃ BO ₃ ), metaboric acid and diboric acid. As the borate, a water-soluble salt of the above-mentioned boric acid is preferable. Examples thereof include alkali metal salts of boric acid such as sodium salts and potassium salts of boric acid; alkaline earth metal salts of boric acid such as magnesium salts and calcium salts of boric acid; ammonium salts of boric acid and the like. Among these, it is preferable to use orthoboric acid from the viewpoint of the temporal stability of the coating liquid and the effect of suppressing the generation of a crack.

(4) Other Additives In the present invention, the second ink receiving layer may contain the same additives as those exemplified for the first ink receiving layer described above.

(Surface protective layer containing colloidal silica)
In the present invention, from the viewpoint of scratch resistance, the recording medium preferably has a surface protective layer (also referred to as the outermost layer) containing colloidal silica on the first ink receiving layer. Among the colloidal silica, spherical colloidal silica is particularly preferable because it has high scratch resistance and high transparency, thereby enhancing the color development of an image obtained. Furthermore, the spherical shape can reduce the sticking of the finger when sliding the finger on the surface of the recording medium, and can further improve the feel of touch. The term "spherical" as used herein means that the ratio b / a of the average major axis a to the average minor axis b of colloidal silica particles (50 to 100) when observed by a scanning electron microscope is 0.80 or more. It means to be in the range of 00 or less. As for b / a, 0.90 or more and 1.00 or less are more preferable, and 0.95 or more and 1.00 or less are especially preferable. Furthermore, spherical cationic colloidal silica is preferred. Specifically, examples of spherical cationic colloidal silica include Snowtex AK, Snowtex AK-L (manufactured by Nissan Chemical Industries, Ltd.), and the like.

  Moreover, it is preferable that the average primary particle diameter of colloidal silica is 30 nm or more and 100 nm or less. When the average particle size is less than 30 nm, the ink absorptivity improvement effect may not be sufficiently obtained, and when it is more than 100 nm, the transparency is reduced and the color development improvement effect of the obtained image is not sufficiently obtained. There is.

  As the binder and the crosslinking agent in the surface protective layer, the same binders and additives as those exemplified in the above-mentioned ink receiving layer can be used. The same kind of binder as that contained in the ink receiving layer may be used, or a different kind of binder may be used.

  The surface protective layer may also contain amorphous silica having an average secondary particle diameter of 1 μm or more. The content thereof is preferably 50.0% by mass or less, and more preferably 40.0% by mass or less, based on the content of the inorganic particles in the surface protective layer.

The coating amount of the surface protective layer is preferably 0.2 g / m ² or more and 3.0 g / m ² or less.

[Method of manufacturing recording medium]
In the present invention, the method for producing the recording medium is not particularly limited, but recording comprising a step of preparing a coating liquid for the ink receiving layer, and a step of coating the coating liquid for the ink receiving layer on a substrate Preferred is a method of producing the medium. Hereinafter, a method of manufacturing the recording medium will be described.

<Method of producing base material>
In the present invention, a generally used paper making method can be applied as a method for producing a base paper. As the paper making apparatus, for example, a Fourdrinier paper machine, a fourdrinier paper machine, a cylinder, a twin wire, etc. may be mentioned. In order to enhance the surface smoothness of the base paper, heat and pressure may be applied to the surface treatment during or after the paper making process. Specific surface treatment methods include calendar processing such as machine calendar and super calendar.

  As a method of providing a resin layer on a base paper, that is, a method of coating the base paper with a resin, a melt extrusion method, wet lamination, dry lamination and the like can be mentioned. Among them, a melt extrusion method in which a molten resin is extrusion coated on one side or both sides of a base paper is preferable. For example, a method of laminating a resin layer on a base paper by bringing a base paper transported and a resin extruded from an extrusion die into contact at a nip point between a nip roller and a cooling roller and pressing the nip at the nip Coating method is also widely adopted. When the resin layer is provided by a melt extrusion method, pretreatment may be performed so that the adhesion between the base paper and the resin layer becomes stronger. Examples of pretreatment include acid etching with a mixed solution of sulfuric acid and chromic acid, flame treatment with gas flame, ultraviolet irradiation treatment, corona discharge treatment, glow discharge treatment, anchor coating treatment with alkyl titanate and the like. Among them, corona discharge treatment is preferred.

  Moreover, the shape of the surface of the resin-coated paper can be controlled by pressing the surface of the resin-coated substrate against a roll having specific asperities.

<Method of 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, a coating liquid for the ink receiving layer is prepared. And the recording medium of this invention can be obtained by 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 hot-air dryer such as a linear tunnel dryer, arch dryer, air loop dryer, sine curve air float dryer, or a dryer using infrared rays, a heating dryer, microwave or the like is used. Methods are included.

  Hereinafter, the present invention will be described in more detail using examples and comparative examples. The present invention is not limited at all by the following examples unless the gist is exceeded. In the following description of the examples, "part" is on a mass basis unless otherwise noted.

Example 1
[Preparation of recording medium]
<Preparation of base material>
80 parts of LBKP with Canadian standard freeness of 450 mL CSF, 20 parts of NBKP with Canadian standard freeness of 480 mL CSF, 0.60 parts of cationized starch, 10 parts of heavy calcium carbonate, 15 parts of light calcium carbonate, 0.10 parts of alkyl ketene dimer Then, 0.030 parts of cationic polyacrylamide was mixed, and water was added so that the solid content is 3.0% by mass, to obtain a stock. Next, the paper stock was made with a Fourdrinier paper machine, subjected to three stages of wet pressing, and then dried with a multi-cylinder dryer. Thereafter, an aqueous solution of oxidized starch was impregnated and dried so that the solid content after drying with a size press was 1.0 g / m ^2, and further, machine calendering was performed to produce a base paper. This base paper had a basis weight of 110 g / m ² , a Stekhito size degree of 100 seconds, an air permeability of 50 seconds, a Beck smoothness of 30 seconds, a Gurley stiffness of 11.0 mN, and a thickness of 120 μm. Next, a resin composition comprising 70 parts of low density polyethylene, 20 parts of high density polyethylene and 10 parts of titanium oxide was applied to one side of the base paper so that the dry coating amount would be 25 g / m ² . . In addition, let this surface be the surface of a base material. By pressing the surface against a metal cooling roll, the surface of the resin-coated paper was processed to have an arithmetic mean roughness Ra of 0.10 μm. Further, a resin composition comprising 50 parts of low density polyethylene and 50 parts of high density polyethylene was coated on the other surface of the base paper at 25 g / m ² to obtain a substrate.

Preparation of First Coating Liquid A for Ink Receptive Layer (Examples 1 to 7, Comparative Examples 1 to 10)>
Amorphous silica (wet silica) was added to ion exchange water to a solid content of 25% by mass. Next, 5.0 parts of polydiallyldimethyl ammonium chloride polymer is added to 100 parts of solid content of amorphous silica and stirred, and the content of solid content of amorphous silica is 21% by mass. Ion-exchanged water was added to obtain an amorphous silica dispersion.

  The prepared amorphous silica dispersion and a binder aqueous solution are mixed so that the mass ratio of solid content (amorphous silica: polyvinyl alcohol) is 100: 15, and the first coating liquid for the ink receiving layer I got an A. In addition, the kind of binder aqueous solution is an aqueous solution which adjusted content of solid content of polyvinyl alcohol (product name: PVA235 (made by Kuraray)) to 8 mass%. Moreover, the average particle diameter of the amorphous silica was measured by the above-mentioned method, and the results are shown in Table 1.

Preparation of First Coating Liquid B for Ink Receiving Layer (Examples 8 to 10)
An amorphous silica dispersion was obtained in the same manner as in the preparation of the coating liquid A for ink receiving layer.

  Furthermore, alumina hydrate DISPERAL HP14 (made by Sasol, average particle diameter 14 nm) was added to ion exchange water so that the content of solid content would be 25% by mass. Next, 1.4 parts of methanesulfonic acid is added to 100 parts of solid content of alumina hydrate and stirred, and the content of solid content of alumina hydrate is 21% by mass. Ion-exchanged water was added to obtain an alumina hydrate dispersion.

  And the mass ratio (amorphous silica: alumina hydrate) of the solid content of amorphous silica to alumina hydrate is 80: 20. The resulting mixture was mixed to obtain a mixed dispersion of silica and alumina.

  The mixed dispersion of prepared silica and alumina and an aqueous binder solution are mixed so that the mass ratio of solid content (amorphous silica + alumina hydrate: polyvinyl alcohol) is 100: 10, A coating solution B for ink receiving layer was obtained. In addition, the said binder aqueous solution is an aqueous solution which adjusted content of solid content of PVA235 (made by Kuraray) to 8 mass%. Moreover, the average particle diameter of the amorphous silica was measured by the above-mentioned method, and the results are shown in Table 1.

Preparation of Second Coating Composition for Ink Receiving Layer
(Preparation of alumina hydrate dispersion)
Alumina hydrate DISPERAL HP 14 (made by Sasol, average particle diameter 14 nm) was added to ion exchange water so that the solid content would be 25% by mass. Next, 1.4 parts of methanesulfonic acid is added to 100 parts of solid content of alumina hydrate and stirred, and the content of solid content of alumina hydrate is 21% by mass. Ion-exchanged water was added to obtain an alumina hydrate dispersion.

(Preparation of Second Coating Liquid for Ink Receiving Layer)
The alumina hydrate dispersion prepared above, the solid content of polyvinyl alcohol aqueous solution (PVA 235 (made by Kuraray) adjusted to 8% by mass), and aqueous boric acid solution (solid content is 3% by mass were mixed so that the mass ratio of solid content (alumina hydrate: polyvinyl alcohol: boric acid) was 100: 10: 2, to obtain a second coating liquid for the ink receiving layer .

<Preparation of Coating Liquid for Surface Protective Layer>
Colloidal silica dispersion (Snowtex AK-L, manufactured by Nissan Chemical Industries, Ltd.), silanol-modified polyvinyl alcohol aqueous solution (R-1130 (made by Kuraray) solid content of 8% by mass), boric acid aqueous solution (solid) (3 parts by mass), and mixing so that the mass ratio of solid content (amorphous silica: polyvinyl alcohol: boric acid) becomes 100: 11: 1.2, coating for surface protection layer I got a liquid.

<Preparation of recording medium>
The first coating liquid for the ink receiving layer, the second coating liquid for the ink receiving layer, and the coating liquid for the surface protective layer (each of the temperature of the coating liquid: 40 ° C.) obtained above are added onto the substrate At the same time, a slide die was used to simultaneously coat the dried coating amount (g / m ² ) to a value described in Table 1. And the coating medium of Examples 1-10 and Comparative Examples 1-10 was produced by drying with a 150 degreeC hot air after application. With regard to the first ink receiving layer coating liquid, the first ink receiving layer coating liquid A is used in Examples 1 to 7 and Comparative Examples 1 to 10, and the first embodiment is used in Examples 8 to 10. Coating solution B for ink receiving layer was used.

  In Table 1, “A × B” means the product of the arithmetic mean roughness Ra (A) of the substrate and the mean particle size (B) of amorphous silica contained in the first ink receiving layer. . Also, the arithmetic mean roughness Ra of the surface of the base material, and the root mean square slope RΔq and the arithmetic mean roughness Ra of the surface roughness curve elements of the surface of the recording medium are all measured based on JIS B 0601: 2001. Value.

[Evaluation]
Matte on the surface of the recording medium
With respect to the obtained recording medium, using a gloss meter VG2000 (manufactured by Nippon Denshoku Kogyo Co., Ltd.), the specular glossiness at 20 degrees, 60 degrees and 75 degrees specified in JIS Z 8741 was measured. The measurement was performed by selecting any five points on the surface of the recording medium, and the average value was calculated. The matte feeling of the surface of the recording medium was evaluated from the obtained specular gloss. Evaluation criteria are as follows. The evaluation results are shown in Table 2.
The maximum value of specular glossiness at 3: 20 °, 60 °, 75 ° was less than 3.5%.
2: The maximum value of specular glossiness at 20 °, 60 ° and 75 ° was 3.5% or more and less than 6.0%.
The maximum value of specular glossiness at 1: 20 °, 60 °, and 75 ° was 6.0% or more.

<Touch of the surface of the recording medium>
With respect to the obtained recording medium, a sensory evaluation of the degree of finger sticking when sliding the finger on the recording medium surface was performed. Evaluation criteria are as follows.
4: I do not feel stuck or uneven.
3: I feel a weak hook, almost no unevenness.
2: I feel a weak hook, feel more uneven.
1: I feel a strong catch.

<Coloring of the obtained image>
On each recording surface of the obtained recording medium, solid printing of black was performed using an inkjet printer (trade name: MG 8230, manufactured by Canon Inc.) in a mode of no gloss correction and a mode with no gloss correction for photographic paper. These optical densities were each measured using an optical reflection densitometer (trade name: 530 spectrodensitometer, manufactured by X-Rite). From the obtained optical density, the color developability of the obtained image was evaluated. Evaluation criteria are as follows. The evaluation results are shown in Table 2.
3: 1.70 or more.
It was 2.1.60 or more and less than 1.70.
It was less than 1: 1.60.

Claims (12)

A recording medium comprising a substrate and a first ink receiving layer,
On the surface of the recording medium
The root mean square slope RΔq of the roughness curve element is 0.30 or more, and
A recording medium having an arithmetic mean roughness Ra of 0.90 μm or less.   The recording medium according to claim 1, wherein the arithmetic mean roughness Ra of the substrate is 0.20 μm or less.   The recording medium according to claim 1, wherein the base material is a resin-coated paper.   The recording medium according to any one of claims 1 to 3, wherein the first ink receiving layer contains amorphous silica.   5. The recording medium according to claim 4, wherein the average particle diameter of the amorphous silica is 2.0 μm or more and 14.0 μm or less. The base material has an arithmetic average roughness Ra of 0.20 μm or less, and the first ink receiving layer contains amorphous silica having an average particle diameter of 2.0 μm or more and 14.0 μm or less.
The product of the arithmetic average roughness Ra of the substrate and the average particle diameter of the amorphous silica contained in the first ink receiving layer is 0.12 or more and 1.80 or less. The recording medium of any one of the items.   The recording medium according to any one of claims 1 to 6, wherein an arithmetic mean roughness Ra of the recording medium is 0.85 μm or less.   The recording medium according to any one of claims 1 to 7, wherein the first ink receiving layer contains inorganic particles having an average particle diameter of 50 nm or less.   The content of the inorganic particles having an average particle diameter of 50 nm or less in the first ink receiving layer is 2% by mass or more and 40% by mass or less based on the total mass of the inorganic particles in the first ink receiving layer. A recording medium according to claim 8.   The recording medium according to any one of claims 1 to 9, further comprising a second ink receiving layer between the substrate and the first ink receiving layer.   The recording medium according to any one of claims 1 to 10, further comprising a surface protective layer containing colloidal silica on the first ink receiving layer. The recording medium according to claim 11, wherein a dry coating amount of the surface protective layer is 0.2 g / m ² or more and 3.0 g / m ² or less.