JP2016141107A - Recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a recording medium which is high in color developability of the resulting image, sufficiently prevents breakage of an ink-receiving layer and is excellent in image clarity.SOLUTION: There is provided a recording medium which has a substrate and an ink-receiving layer containing inorganic particles and a binder, wherein the inorganic particles has two modification groups containing a silicon atom.SELECTED DRAWING: None

Description

  The present invention relates to a recording medium.

  A recording medium having an ink receiving layer containing inorganic particles is used because of its high ink absorbability and high color developability of the resulting image. Such a recording medium can be obtained by coating an ink receiving layer coating liquid in which inorganic particles are dispersed on a substrate. However, the dispersion stability of the inorganic particles in the ink receiving layer coating liquid is sufficient. Otherwise, when the ink receiving layer is formed, the surface is cracked or the inorganic particles are not uniformly dispersed in the ink receiving layer, resulting in low color developability of the image, The image clarity of the recording medium may be lowered.

  Therefore, studies have been made on dispersants that can stably disperse inorganic particles in a coating solution (Patent Documents 1 to 3). As a dispersant, Patent Document 1 discloses a cationic polymer having a structural unit of a polydiallylamine derivative, Patent Document 2 includes a composition containing a quaternary amino-functional organosilicon compound, and Patent Document 3 includes Each of the compositions containing a quaternary amino alcohol functional organosilicon compound is described.

JP 2000-2111235 A Special table 2012-524163 gazette Special table 2013-535431 gazette

  According to the study by the present inventors, the dispersion agents described in Patent Documents 1 to 3 are not sufficient, although the dispersion stability of the inorganic particles is improved, and the color developability of the obtained image is at the level required by the present invention. In some cases, the ink receiving layer was cracked. Furthermore, the image clarity of the recording medium was not sufficient.

  Therefore, the object of the present invention is to improve the dispersion stability of the inorganic particles in the ink receiving layer coating liquid, the color developability of the obtained image is high, and the crack of the ink receiving layer is sufficiently suppressed, The object is to provide a recording medium excellent in image clarity.

  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 containing inorganic particles and a binder, and the inorganic particles are represented by the following general formula (1), and the following general formula: And a group represented by (2).

(The group represented by the general formula (1) is bonded to the surface of the inorganic particle at *. In the above formula, X is an alkoxy group having 1 to 8 carbon atoms, aryloxy group, acetoxy group, halogen atom, hydrogen atom. , A hydrocarbon group having 1 to 8 carbon atoms, or —O— *, where Y is a group having two or more hydroxyl groups including at least one primary hydroxyl group, and n is 1. 2 or 3.)

(The group represented by the general formula (2) is bonded to the surface of the inorganic particle at *. In the above formula, X ′ is an alkoxy group having 1 to 8 carbon atoms, aryloxy group, acetoxy group, halogen atom, hydrogen atom. An atom, a hydrocarbon group having 1 to 8 carbon atoms, or -O- *. Y 'is a group having a hydroxyl group and a cationic group. M is 1, 2 or 3.)

  According to the present invention, it is possible to provide a recording medium having high color developability of an image obtained and sufficiently suppressing cracking of the ink receiving layer and having excellent image clarity.

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

  As a result of studies by the present inventors, in order to raise the color developability of the obtained image and the image transferability of the recording medium to a higher level and sufficiently suppress the cracking of the ink receiving layer, the coating for the ink receiving layer is required. In addition to improving the dispersion stability of the inorganic particles in the liquid, the interaction with the colorant in the ink and the interaction with the binder as a binder for the inorganic particles contained in the ink receiving layer are also considered. Found that there is a need to do.

And it has been found that the above effect can be obtained by including a material having a specific structure as a coupling agent between the inorganic particles and the binder in the ink receiving layer.
Specifically, the inorganic particles are groups represented by the following general formula (1).

(The group represented by the general formula (1) is bonded to the surface of the inorganic particle at *. In the above formula, X is an alkoxy group having 1 to 8 carbon atoms, aryloxy group, acetoxy group, halogen atom, hydrogen atom. , A hydrocarbon group having 1 to 8 carbon atoms, or —O— *, where Y is a group having two or more hydroxyl groups including at least one primary hydroxyl group, and n is 1. 2 or 3.)
And a group represented by the following general formula (2)

(The group represented by the general formula (2) is bonded to the surface of the inorganic particle at *. In the above formula, X ′ is an alkoxy group having 1 to 8 carbon atoms, aryloxy group, acetoxy group, halogen atom, hydrogen atom. An atom, a hydrocarbon group having 1 to 8 carbon atoms, or -O- *. Y 'is a group having a hydroxyl group and a cationic group. M is 1, 2 or 3.)
It is necessary to have The presumed mechanism by which the effect is acquired by such a configuration is as follows.

  First, like the group represented by the general formula (1), it has two or more hydroxyl groups, and at least one of them is a primary hydroxyl group. Therefore, the ink receiving layer can be sufficiently prevented from cracking. Furthermore, since it has an organosilicon structure having a hydroxyl group and a cationic group like the group represented by the general formula (2), the dispersion stability of the inorganic particles in the ink-receiving layer coating liquid is increased. An ink receiving layer in which inorganic particles are uniformly dispersed is obtained, and the color developability of the obtained image and the image transferability of the recording medium are enhanced.

[recoding media]
The recording medium of the present invention has a base material 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, it is preferable to use a base material having a base paper and a resin layer. In that case, the resin layer may be provided only on one side of the base paper, but is preferably provided on both sides.

(Base paper)
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.

  In the present invention, the thickness of the base paper is preferably 50 μm or more and 250 μm or less, and more preferably 90 μm or more and 210 μm or less. In the present invention, the thickness of the base paper 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 or more points of the base paper is measured, and the average value is defined as the film thickness of the base paper. The film thicknesses of the other layers in the present invention are calculated by the same method.

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

(Resin layer)
In the present invention, when the base paper is coated with a resin, the resin layer may be provided so as to cover a part of the surface of the base paper. The area of the surface of the base paper / the total area of the surface of the base paper) is preferably 70% or more, more preferably 90% or more, and further 100%, that is, It is particularly preferable that the entire surface is covered with a resin layer.

  In the present invention, the thickness of the resin layer is preferably 20 μm or more and 60 μm or less, and the thickness of the resin layer is more preferably 35 μm or more and 50 μm or less. When the resin layers are provided on both sides of the base paper, it is preferable that the film thicknesses of the resin layers on both sides satisfy the above ranges.

  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).

In the present invention, the resin layer may contain a white pigment, a fluorescent whitening 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. In the present invention, the content of the white pigment in the resin layer is preferably 3 g / m ² or more and 30 g / m ² or less. In addition, when providing a resin layer on both surfaces of a base paper, it is preferable that content of the sum total of the white pigment in two resin layers satisfies the said range. Moreover, it is preferable that content of the white pigment in a resin layer is 25 mass% or less with respect to content of resin. If it is larger than 25% by mass, the dispersion stability of the white pigment may not be sufficiently obtained.

<Ink receiving layer>
In the present invention, the ink receiving layer may be a single layer or a multilayer of two or more layers. Further, the ink receiving layer may be provided only on one side of the base material or on both sides. The film thickness of the ink receiving layer is preferably 15 μm or more and 60 μm or less, and more preferably 30 μm or more and 45 μm or less. Hereinafter, materials that can be contained in the ink receiving layer will be described.

(Inorganic particles having a group represented by the general formula (1) and a group represented by the general formula (2))
In the present invention, the inorganic particles have a group represented by the general formula (1) and a group represented by the general formula (2). The group represented by the general formula (1) and the group represented by the general formula (2) can be introduced into the inorganic particles by treating the surface of the inorganic particles with a specific silane coupling agent. Hereinafter, each group and inorganic particles will be described.

(1) Group Represented by General Formula (1) In the present invention, the inorganic particles have a group represented by the following general formula (1).

The group represented by the general formula (1) is bonded to the surface of the inorganic particle at *. In the general formula (1), X is an alkoxy group having 1 to 8 carbon atoms, an aryloxy group, an acetoxy group, a halogen atom, a hydrogen atom, a hydrocarbon group having 1 to 8 carbon atoms, or -O- *. is there. Note that “X is —O— *” means that a silicon atom (Si) is bonded to the surface of an inorganic particle through an oxygen atom (O). At this time, the inorganic particles to which “*” is bonded may be the same or different. However, since the inorganic particles are very large compared to the group represented by the general formula (1), in general, , Are considered to bind to the same inorganic particles. Y is a group having two or more hydroxy groups including at least one or more primary hydroxyl groups. n is 1, 2 or 3, and n is preferably 1.

  In this invention, it is preferable that Y in General formula (1) has a structure represented by following General formula (3).

In the general formula (3), R ₁ is a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms. p + q is an integer of 1 or more. Further, the order of the P structure and the Q structure is arbitrary. That is, not only when it is -PPPPP-QQ-, but also when it is -QQQQPP-PP-, or -PQQPPQP The general formula (3) includes a case where they are alternated like -Q- and a case where they are arranged randomly like -PPPQPQQ-.

  In this invention, the inorganic particle which has group represented by General formula (1) is obtained by modifying the surface of an inorganic particle with the compound represented by following General formula (5), for example.

In General formula (5), X is a C1-C8 alkoxy group, an aryloxy group, or an acetoxy group. Y is a group having two or more hydroxyl groups, including at least one or more primary hydroxyl groups. n is 1, 2 or 3.

  Inorganic particles have hydroxyl groups on their surfaces. And the inorganic particle which has group represented by General formula (1) is obtained because the compound represented by General formula (5) reacts with the hydroxyl group of the inorganic particle surface.

  In the present invention, the compound represented by the general formula (5) is preferably at least one selected from the following compound 1, the following compound 2, and the following compound 3. In the following formula, R is a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms.

(2) Group Represented by General Formula (2) In the present invention, the inorganic particles have a group represented by the following general formula (2).

The group represented by the general formula (2) is bonded to the surface of the inorganic particle at *. In General Formula (2), X ′ represents an alkoxy group having 1 to 8 carbon atoms, an aryloxy group, an acetoxy group, a halogen atom, a hydrogen atom, a hydrocarbon group having 1 to 8 carbon atoms, or —O— *. It is. Note that “X ′ is —O— *” means that the silicon atom (Si) is bonded to the surface of the inorganic particle through the oxygen atom (O). At this time, the inorganic particles to which “*” binds may be the same or different. However, since the inorganic particles are very large compared to the group represented by the general formula (2), Are considered to bind to the same inorganic particles. m is 1, 2 or 3, and m is preferably 1.

  In the general formula (2), Y ′ is a group having both a hydroxyl group and a cationic group. The cationic group is preferably a quaternary ammonium group. The group represented by the general formula (2) has a monovalent anion as a counter ion of the cationic group. Examples of monovalent anions include halogen ions.

  Moreover, it is preferable that group represented by General formula (2) is a structure represented by following General formula (4). The structure represented by the general formula (4) has a monovalent anion as a counter ion. Examples of monovalent anions include halogen ions.

(The group represented by the general formula (4) is bonded to the surface of the inorganic particle at *. In the above formula, R ¹ is an alkyl group or aryl group having 1 to 8 carbon atoms, and X is the following general formula X) A is 1, 2 or 3.)

(In General Formula X, R ^X1 and R ^X2 are each independently an alkylene group or arylene group having 2 to 8 carbon atoms. At least one selected from R ^X3 , R ^X4, and R ^X5 is the following General Formula Q: The other structure is a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or an aryl group, and b is an integer of 0 to 5. The left end of the general formula X is the general formula (1). Introduced into X in

(In the general formula Q, R ^Q1 , R ^Q2 and R ^Q3 are each independently an alkyl group or aryl group having 1 to 10 carbon atoms. The left end of the general formula Q is R ^X3 , R ^X4 and Introduced into at least one selected from R ^X5 .)

   In order to obtain inorganic particles having a structure represented by the general formula (4), a silane coupling agent represented by the following general formula (4) ′ may be used. The silane coupling agent represented by the general formula (4) ′ has a monovalent anion as a counter ion. Examples of monovalent anions include halogen ions.

(In the general formula (4) ′, R ¹ is an alkyl group or aryl group having 1 to 8 carbon atoms, and X is a structure represented by the general formula X. Y is a hydroxyl group, a halogen group, or an alkoxy group. And a hydrolyzable group such as an acetoxy group, a is 1, 2 or 3.)

  In this invention, it is preferable that the usage-amount of the silane coupling agent represented by General formula (4) 'is 3 to 30 mass% with respect to content of an inorganic particle, and 5 to 20 mass%. It is more preferable that the amount is not more than mass%.

  The silane coupling agent represented by the general formula (4) ′ includes a compound represented by the following general formula (6) (aminosilane coupling agent) and a compound represented by the following general formula (7) (quaternary amino). It can be obtained by reacting a glycidyl compound having a group).

(In General Formula (6), R ¹ is an alkyl group or an aryl group having 1 to 8 carbon atoms. Y is a hydrolyzable group such as a hydroxyl group, a halogen group, an alkoxy group, or an acetoxy group. R ^X1 and R ^X2 is independently an alkylene group or an arylene group having 2 to 8 carbon atoms, at least one selected from R ^X3 , R ^X4 and R ^X5 is a hydrogen atom, and the rest are hydrogen atoms or carbon atoms of 1 An alkyl group or an aryl group of 1 to 8, a is 1, 2 or 3, and b is an integer of 0 to 5.)

  Specific examples of the compound represented by the general formula (6) include 3-aminopropyltriethoxysilane, 4-aminobutyltriethoxysilane, and N- (2-aminoethyl) -3-aminopropyltrimethoxysilane. N- (2-aminoethyl) -3-aminopropylsilanetriol, N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane, (3-trimethoxysilylpropyl) diethylenetriamine, n-butylaminopropyltri Examples include methoxysilane, N-ethylaminoisobutyltrimethoxysilane, N-methylaminopropyltrimethoxysilane, and N-phenylaminopropyltrimethoxysilane.

(In the general formula (7), R ^Q1 , R ^Q2 and R ^Q3 are each independently an alkyl group or an aryl group having 1 to 10 carbon atoms. The compound represented by the general formula (7) is 1 as a counter ion. (The monovalent anion includes a halogen ion.)
Specific examples of the compound represented by the general formula (7) include glycidyltrimethylammonium chloride, glycidylbutyldimethylammonium chloride, and the like, which can be obtained by an addition reaction between epichlorohydrin and a tertiary amine. .

  In the present invention, the number of amino groups in the structures represented by the general formulas (4) and (4) ′ is 0.5 to 5.0 times the number of quaternary ammonium groups. Is more preferable, and it is more preferably 1.0 times or more and 3.0 times or less.

  Furthermore, X in the general formulas (4) and (4) ′ is represented by the structure represented by the following general formula X-1, the structure represented by the following general formula X-2, or the following general formula X-3. It is preferable that it is a structure. The left end of the following general formulas X-1 to X-3 is introduced into X in the general formulas (4) and (4) ′.

(In General Formula X-1, at least one selected from R ^A1 and R ^A2 is a structure represented by General Formula Q, and the rest are hydrogen atoms, alkyl groups having 1 to 8 carbon atoms, or aryl groups. .)

(In General Formula X-2, at least one selected from R ^A1 , R ^A2 and R ^A3 is a structure represented by General Formula Q, and the others are hydrogen atoms or alkyl groups having 1 to 8 carbon atoms. Or an aryl group.)

(In General Formula X-3, at least one selected from R ^A1 , R ^A2 , R ^A3 and R ^A4 is a structure represented by General Formula Q, and the others are hydrogen atoms or carbon atoms having 1 to 8 carbon atoms. An alkyl group or an aryl group.)

(3) Inorganic particles Examples of the inorganic particles used in the present invention include gas phase method silica, alumina hydrate, gas phase method alumina, 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 can be used alone or in combination of two or more as required. Among the inorganic particles, gas phase method silica, alumina hydrate, and gas phase method alumina are preferably used, and gas phase method silica is used, that is, represented by general formula (1) and general formula (2). It is particularly preferred to use gas phase method silica having a group.

  Examples of the vapor phase method silica include Aerosil (manufactured by Nippon Aerosil), Leorosil QS type (manufactured by Tokuyama), Cab-O-Sil 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.

Alumina hydrate
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 alumina hydrate, amorphous, gibbsite type, and boehmite type are known depending on the heat treatment temperature. The crystal structure of alumina hydrate can be analyzed by an X-ray diffraction method. Of these, boehmite type alumina hydrate or amorphous alumina hydrate is preferable in the present invention. 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, and commercially available products. Includes Dispersal HP14 and HP18 (above, 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 the vapor phase method alumina 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 of vapor-phase process alumina include AEROXIDE; Alu C, Alu 130, Alu 65 (above, EVONIK).

In the present invention, the specific surface area determined by the BET method of vapor phase alumina is preferably 50 m ² / g or more, more preferably 80 m ² / g or more. Moreover, 150 m < ² > / g or less is preferable and 120 m < ² > / g or less is more preferable.

  In the present invention, the content of the silane coupling structure represented by the general formula (1) and the general formula (2) is 3% by mass or more with respect to the amount of the inorganic particles. Is preferable from the viewpoint of a small amount, and more preferably 5% by mass or more. It is preferably 30% by mass or less from the viewpoint of ink absorbability, and more preferably 20% by mass or less.

  In the present invention, the content ratio of the silane coupling structure represented by the general formula (1) and the general formula (2) is preferably 90:10 to 10:90, but high color development, defect-free, and high image clarity. Is more preferably 50:50 to 10:90.

  In the present invention, the content (mass%) of the inorganic particles having groups represented by the general formula (1) and the general formula (2) in the ink receiving layer is 50% by mass or more and 98% by mass or less. More preferably, the content is 70% by mass or more and 96% by mass or less.

In the present invention, the coating amount (g / m ² ) of the inorganic particles having a group represented by the general formula (1) and the general formula (2) applied when forming the ink receiving layer is 8 g / m ² or more and 45 g. / M ² or less is preferable. By setting it within the above range, it is easy to obtain a preferable ink receiving layer thickness.

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

  In the present invention, from the viewpoint of ink absorptivity, the content of the binder in the ink receiving layer is preferably 50% by mass or less and more preferably 30% by mass or less with respect to the content of the inorganic particles. Further, from the viewpoint of the binding property of the ink receiving layer, the ratio is preferably 5.0% by mass or more, and more preferably 8.0% by mass or more.

  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, and derivatives thereof; polyvinyl Conjugated polymer latex such as pyrrolidone, maleic anhydride resin, styrene-butadiene copolymer, methyl methacrylate-butadiene copolymer; acrylic polymer latex such as acrylate ester and methacrylate ester polymer; ethylene-vinyl acetate A vinyl polymer latex such as a copolymer; a functional group-modified polymer latex with a functional group-containing monomer such as a carboxyl group of the polymer; a polymer obtained by cationizing the polymer using a cationic group; A cationized surface of the polymer using a thionic surfactant; a monomer that forms the polymer under cationic polyvinyl alcohol, and a polyvinyl alcohol distributed on the surface of the polymer; a cation Polymers in which the monomer constituting the polymer is polymerized in a suspension dispersion of the conductive colloidal particles and the cationic colloidal particles are distributed on the surface of the polymer; aqueous such as thermosetting synthetic resins such as melamine resin and urea resin Binders; Polymers and copolymers of acrylic acid esters and methacrylic acid esters such as polymethyl methacrylate; polyurethane resins, unsaturated polyester resins, vinyl chloride-vinyl acetate copolymers, polyvinyl butyral, alkyd resins and the like It is done. 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. Examples of the cation-modified polyvinyl alcohol include a polyvinyl alcohol having a primary to tertiary amino group or a quaternary ammonium group in the main chain or side chain of polyvinyl alcohol, as described in, for example, JP-A-61-110483. Alcohol is preferred.

  Polyvinyl alcohol can be synthesized, for example, by saponifying polyvinyl acetate. The saponification degree of polyvinyl alcohol is preferably 80 mol% or more and 100 mol% or less, and more preferably 85 mol% or more and 98 mol% or less. 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. Value shall be used. The average degree of polymerization of polyvinyl alcohol is preferably 2,000 or more, and more preferably 2,000 or more and 5,000 or less. 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.

(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 polyvinyl alcohol or a polyvinyl alcohol derivative is used as a binder, it is preferable to use boric acid or a borate 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, it is preferable to use orthoboric acid from the viewpoint of the temporal stability of the coating liquid and the effect of suppressing the occurrence of cracks.

  The amount of the crosslinking agent used can be appropriately adjusted according to the production conditions. In the present invention, the content of the crosslinking agent in the ink receiving layer is preferably 1.0% by mass or more and 50% by mass or less, and more preferably 5% by mass or more and 40% by mass or less with respect to the content of the binder. .

  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 is preferably 5% by mass or more and 30% by mass or less.

(Other additives)
In the present invention, the ink receiving layer may contain other additives other than those described above. Specifically, pH adjusters, thickeners, fluidity improvers, antifoaming agents, antifoaming agents, surfactants, mold release agents, penetrating agents, coloring pigments, colored dyes, fluorescent whitening agents, UV absorption Agents, antioxidants, antiseptics, antifungal agents, water resistance agents, dye fixing agents, curing agents, weathering materials and the like.

  In particular, in the present invention, from the viewpoint of storage of the obtained recording medium, the ink receiving layer preferably further contains a water-soluble polyvalent metal compound or cationic resin particles in order to improve moisture resistance.

(1) Water-soluble polyvalent metal compound Examples of the water-soluble polyvalent metal compound include calcium, barium, manganese, copper, cobalt, nickel, aluminum, iron, zinc, zirconium, titanium, chromium, magnesium, tungsten, and molybdenum. These can be used as water-soluble salts of these metals. Specifically, for example, calcium acetate, calcium chloride, calcium formate, calcium sulfate, calcium lactate, barium acetate, barium sulfate, barium phosphate, manganese chloride, manganese acetate, manganese formate dihydrate, manganese ammonium sulfate hexahydrate , Cupric chloride, ammonium copper (II) chloride dihydrate, copper sulfate, cobalt chloride, cobalt thiocyanate, cobalt sulfate, nickel sulfate hexahydrate, nickel chloride hexahydrate, nickel acetate tetrahydrate , Nickel ammonium sulfate hexahydrate, nickel amidosulfate tetrahydrate, aluminum sulfate, aluminum sulfite, aluminum thiosulfate, polyaluminum chloride, aluminum nitrate nonahydrate, aluminum chloride hexahydrate, aluminum lactate, bromide Ferrous, ferrous chloride, ferric chloride, ferrous sulfate, sulfuric acid Iron, zinc bromide, zinc chloride, zinc nitrate hexahydrate, zinc sulfate, zirconium acetate, zirconium nitrate, basic zirconium carbonate, zirconium hydroxide, zirconium carbonate / ammonium, zirconium carbonate / potassium, zirconium sulfate, zirconium fluoride , Zirconium chloride, zirconium chloride octahydrate, zirconium oxychloride, hydroxy zirconium chloride, titanium chloride, titanium sulfate, chromium acetate, chromium sulfate, magnesium sulfate, magnesium chloride hexahydrate, magnesium citrate nonahydrate, lactic acid Examples include magnesium, sodium phosphotungstate, sodium tungsten citrate, 12 tungstophosphoric acid n hydrate, 12 tungstophosphoric acid 26 hydrate, molybdenum chloride, 12 molybdophosphoric acid n hydrate, and the like. Among these, an aluminum compound or a zirconium compound is preferable, and polyaluminum chloride and zirconium acetate are particularly preferable.

  In the present invention, the content of the water-soluble polyvalent metal compound in the ink receiving layer is preferably 1% by mass or more and 10% by mass or less, and preferably 1% by mass or more and 5% by mass with respect to the content of the inorganic particles. The following is more preferable.

(2) Cationic resin particles Cationic resin particles include conjugated diene resin particles such as styrene-butadiene copolymer and methyl methacrylate-butadiene copolymer; polymers or copolymers of acrylic acid esters and methacrylic acid esters. Acrylic resin particles such as acrylic acid or methacrylic acid polymer or copolymer; vinyl resin particles such as ethylene vinyl acetate copolymer cationized, and the surface of the resin particles using a cationic surfactant. Examples include cationized ones. Among these, resin particles using a styrene-acrylic copolymer are preferable.

  In the present invention, the content of the cationic resin in the ink receiving layer is preferably 1% by mass or more and 10% by mass or less, and preferably 1% by mass or more and 5% by mass or less with respect to the content of the inorganic particles. It is more preferable.

<Undercoat layer>
In the present invention, an undercoat layer may be provided between the substrate and the ink receiving layer for the purpose of improving the adhesion between the substrate and the ink receiving layer. The undercoat layer preferably contains a water-soluble polyester resin, gelatin, polyvinyl alcohol and the like. The thickness of the undercoat layer is preferably from 0.01 μm to 5 μm.

<Back coat layer>
In the present invention, the backcoat layer is provided on the surface of the substrate opposite to the surface on which the ink receiving layer is provided in order to improve handling properties, transportability, and transport scratch resistance during continuous printing with a large number of sheets stacked. May be provided. The back coat layer preferably contains a white pigment or a binder. The back coat layer preferably has a dry coating amount of 1 g / m ² or more and 25 g / m ² or less.

[Method of manufacturing recording medium]
In the present invention, the method for producing a recording medium is not particularly limited, but the recording medium includes a step of preparing a coating liquid for the ink receiving layer and a step of coating the base material with the coating liquid for the ink receiving layer. A method for producing the medium is preferred. Hereinafter, a method for manufacturing the recording medium will be described.

<Method for producing substrate>
In the present invention, a generally used paper making method can be applied as a method for producing the base paper. Examples of the paper machine include a long net paper machine, a round net paper machine, a cylinder, and a twin wire. In order to improve the surface smoothness of the base paper, surface treatment may be performed by applying heat and pressure during the paper making process or after the paper making process. Specific surface treatment methods include calendar processing such as machine calendar and super calendar.

  Examples of a method of providing a resin layer on the base paper, that is, a method of coating the base paper with a resin include a melt extrusion method, wet lamination, dry lamination, and the like. Among these, a melt extrusion method in which a molten resin is applied to one side or both sides of a base paper by extrusion coating is preferable. For example, a method of laminating a resin layer on a base paper by bringing the conveyed base paper into contact with the resin extruded from an extrusion die at a nip point between a nip roller and a cooling roller and press-bonding at the nip (extrusion) (Also called coating method) is widely adopted. When the resin layer is provided by melt extrusion, pretreatment may be performed so that the adhesion between the base paper and the resin layer becomes stronger. Examples of the pretreatment include an acid etching treatment using a mixed solution of chromic sulfate, a flame treatment using a gas flame, an ultraviolet irradiation treatment, a corona discharge treatment, a glow discharge treatment, and an anchor coat treatment such as an alkyl titanate. Among these, corona discharge treatment is preferable. Further, when the resin layer contains a white pigment, the base paper may be covered with a mixture of resin and white pigment.

<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 the recording medium of this invention can be obtained 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. The present invention is preferable because cracking of the ink receiving layer is suppressed even when high-speed drying is performed using hot air of 90 ° C. or higher.

  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 base material>
Canada Standard Freeness 450 mLCSF LBKP 80 parts, Canada Standard Freeness 480 mLCSF NBKP 20 parts, Cationic Starch 0.60 parts, Heavy Calcium Carbonate 10 parts, Light Calcium Carbonate 15 parts, Alkylketene Dimer 0.10 parts Then, 0.030 parts of cationic polyacrylamide was mixed, and water was added so that the solid content was 3.0% by mass to obtain a paper stock. Next, the stock was made with a long paper machine, subjected to a three-stage wet press, and then dried with a multi-cylinder dryer. Thereafter, the starch starch aqueous solution was impregnated and dried so that the solid content after drying with a size press machine was 1.0 g / m ^2, and further machine calendered to a basis weight of 170 g / m ² . A base paper having a sizing 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 film thickness of 100 μm was prepared. Next, a resin composition consisting of 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 was 25 g / m ² . . This surface is the surface of the substrate. Furthermore, the base material was obtained by coating low-density polyethylene on the other surface of the base paper.

<Synthesis of silane coupling agent>
(Synthesis of silane coupling agent A)
In 161 parts of ion-exchanged water, 22.2 parts of N- (2-aminoethyl) -3-aminopropyltrimethoxysilane is dissolved, and an aqueous solution of glycidyltrimethylammonium chloride (SY-GTA80 manufactured by Sakamoto Pharmaceutical Co., Ltd.) is stirred. ) 19.0 parts were added. The mixture was further stirred at 60 ° C. for 1 hour, and then the heating was stopped and the mixture was allowed to stand until it reached room temperature to obtain an aqueous solution of a silane coupling agent A having a solid content concentration of 17.8%.

(Synthesis of silane coupling agent B)
Dissolve 22.2 parts of 3-aminopropyltriethoxysilane in 160.9 parts of ion-exchanged water, and add 19.0 parts of an aqueous solution of glycidyltrimethylammonium chloride (SY-GTA80 manufactured by Sakamoto Pharmaceutical Co., Ltd.) while stirring. did. Furthermore, stirring was performed at 60 ° C. for 1 hour, and then the heating was stopped and the mixture was allowed to stand until it reached room temperature to obtain an aqueous solution of a silane coupling agent B having a solid content concentration of 15.5%.

(Synthesis of silane coupling agent C)
In 178.2 parts of ion-exchanged water, 26.5 parts of (3-trimethoxysilylpropyl) diethylenetriamine are dissolved, and an aqueous solution of glycidyltrimethylammonium chloride (SY-GTA80 manufactured by Sakamoto Pharmaceutical Co., Ltd.) 18.9 is stirred. Parts were added. Furthermore, stirring was performed at 60 ° C. for 1 hour, and then heating was stopped and the mixture was allowed to stand until it reached room temperature to obtain an aqueous solution of a silane coupling agent C having a solid content concentration of 18%.

(Synthesis of silane coupling agent D)
13.3 parts of N- (2-aminoethyl) -3-aminopropyltrimethoxysilane are dissolved in 139.8 parts of ion-exchanged water, and an aqueous solution of glycidyltrimethylammonium chloride (SY, manufactured by Sakamoto Pharmaceutical Co., Ltd.) is stirred. -GTA80) 22.7 parts were added. Furthermore, stirring was performed at 60 ° C. for 1 hour, and then the heating was stopped and the mixture was allowed to stand until it reached room temperature to obtain an aqueous solution of a silane coupling agent D having a solid content concentration of 18.4%.

(Synthesis of silane coupling agent E)
11.2 parts of N- (2-aminoethyl) -3-aminopropyltrimethoxysilane are dissolved in 152.5 parts of ion-exchanged water, and an aqueous solution of glycidyltrimethylammonium chloride (SY, manufactured by Sakamoto Pharmaceutical Co., Ltd.) is stirred. -GTA80) 28.4 parts were added. The mixture was further stirred at 60 ° C. for 1 hour, and then the heating was stopped and the mixture was allowed to stand until it reached room temperature to obtain an aqueous solution of silane coupling agent E having a solid content concentration of 18.8%.

(Synthesis of silane coupling agent F)
To 154.7 parts of ion-exchanged water, 23.6 parts of 3-glycidoxypropyltrimethoxysilane was dissolved, and 7.3 parts of diethylamine was added with stirring. Furthermore, stirring was performed at 60 ° C. for 1 hour, and then heating was stopped and the mixture was allowed to stand until it reached room temperature to obtain an aqueous solution of a silane coupling agent F having a solid concentration of 18%.

(Synthesis of silane coupling agent G)
To 135.0 parts of ion-exchanged water, (3-glycidoxypropyltrimethoxysilane, 23.6 parts were dissolved, and 10.1 parts of triethylamine was added with stirring. The mixture was further stirred at 60 ° C. for 1 hour. After that, the heating was stopped and the mixture was allowed to stand until it reached room temperature to obtain an aqueous solution of a silane coupling agent G having a solid content concentration of 18%.

(Preparation of silane coupling agents a, b, c)
The following silane coupling agents a, b and c were prepared.

<Examples 1 to 15 and Comparative Examples 1 to 4>
(Preparation of inorganic particle dispersion)
With respect to ion-exchanged water, the first silane coupling agent described in Table 1 is M parts (amount used in terms of solid content with respect to 100 parts by mass of vapor-phase process silica), and the second silane cup described in Table 1 N part of ring agent (amount used in terms of solid content with respect to 100 parts by mass of gas-phase process silica), 0.72 part of 10% aqueous methanesulfonic acid solution (amount of use in terms of solid content with respect to 100 parts by mass of gas-phase method silica) ) Added. This aqueous solution was treated with T.W. K. Gas phase method silica AEROSIL300 (manufactured by EVONIK) was added little by little while stirring with a homomixer MARKII type 2.5 (manufactured by Tokushu Kika Kogyo Co., Ltd.) at a rotational speed of 5,000 rpm. Furthermore, it processed with CLEARMIX (made by M technique) for 30 minutes on the rotation conditions of 10000 rpm, and prepared the inorganic particle dispersion liquid whose content of solid content is 21 mass%.

(Preparation of binder solution)
Polyvinyl alcohol PVA235 (manufactured by Kuraray Co., Ltd., viscosity average polymerization degree: 3,500, saponification degree: 88 mol%) was dissolved in ion exchange water to obtain a binder solution having a solid content of 8.0% by mass.

(Preparation of ink receiving layer coating solution)
With respect to 100 parts of vapor phase method silica solid content contained in an inorganic particle dispersion liquid, it mixed so that solid content in a binder solution might be 23.0 parts, and the mixed solution was obtained. Next, an orthoboric acid aqueous solution (solid content is 5% by mass) that is a cross-linking agent so as to be 3 parts in terms of solid content with respect to 100 parts of vapor phase method silica solid content in the obtained mixed solution, 1 part of zirconium acetate (Chemical point, solid content 22%) and 3 parts of cationic styrene-acryl emulsion B270D (BASF, solid content 31.6%) are mixed, and ion-exchanged water is added appropriately. In addition, an ink receiving layer coating solution having a total solid content of 15% was obtained.

(Preparation of recording medium)
On the base material obtained above, the coating liquid for ink-receiving layer prepared above was applied. At this time, the dry coating amount was set to 26 g / m ² . Furthermore, after coating, the recording medium was obtained by drying with hot air at 90 ° C.

<Example 16>
In the preparation of the inorganic particle dispersion liquid of Example 1, the inorganic particle dispersion liquid P prepared in the same manner as in Example 1 except that the second silane coupling agent (that is, silane coupling agent a) was not used. A recording medium was obtained in the same manner as in Example 1 except that the inorganic particle dispersion was mixed at a mass ratio of 50:50.

<Example 17>
A recording medium was obtained in the same manner as in Example 11 except that the inorganic particle dispersion Q in Example 16 and the inorganic particle dispersion in Example 11 were mixed at a mass ratio of 30:70.

[Evaluation]
(Evaluation of color development of the resulting image)
Using the inkjet recording apparatus PIXUS MG7130 (manufactured by Canon) equipped with an ink cartridge BCI-351 (manufactured by Canon) for each recording medium obtained above, in the “photo paper glossy gold no color correction” mode, A black solid image of 2.5 cm × 2.5 cm (an image having a recording duty of 100%) was recorded. The recording conditions were temperature: 23 ° C. and relative humidity: 50%. The optical density of the obtained image was measured using an optical reflection densitometer 530 spectral densitometer (manufactured by X-Rite). The color developability of the image was evaluated from the obtained optical density value. The larger the optical density value, the higher the color developability of the image. The evaluation criteria are as follows. The evaluation results are shown in Table 2.
A: Optical density was 2.25 or more B: Optical density was 2.25 or more and less than 2.05 C: Optical density was 2.05 or more and less than 1.95 D: Optical density was 1 .95 or less.

(Evaluation of ink receiving layer cracks)
Each recording medium obtained above was visually observed to evaluate cracking of the ink receiving layer. The evaluation criteria are as follows. The evaluation results are shown in Table 2.
A: No cracking occurred in the ink receiving layer. B: A slight cracking occurred in the ink receiving layer, but the level was not noticeable. C: A crack occurred in the ink receiving layer.

(Evaluation of image clarity)
Each of the recording media obtained above was measured with an image clarity measuring device ICM-1T (manufactured by Suga Test Instruments Co., Ltd.) under the conditions of an incident angle of 60 °, a light receiving angle of 60 °, and an optical comb width of 2.0 mm. Asked. The evaluation results are shown in Table 2.
A: C value was 75% or more B: C value was 70% or more and less than 75% C: C value was 60% or more and less than 70% D: C value was less than 60% .

Claims (3)

A recording medium having a substrate and an ink receiving layer containing inorganic particles and a binder,
The inorganic particle has a group represented by the following general formula (1) and a group represented by the following general formula (2).

(The group represented by the general formula (1) is bonded to the surface of the inorganic particle at *. In the above formula, X is an alkoxy group having 1 to 8 carbon atoms, aryloxy group, acetoxy group, halogen atom, hydrogen atom. , A hydrocarbon group having 1 to 8 carbon atoms, or —O— *, where Y is a group having two or more hydroxyl groups including at least one primary hydroxyl group, and n is 1. 2 or 3.)

(The group represented by the general formula (2) is bonded to the surface of the inorganic particle at *. In the above formula, X ′ is an alkoxy group having 1 to 8 carbon atoms, aryloxy group, acetoxy group, halogen atom, hydrogen atom. An atom, a hydrocarbon group having 1 to 8 carbon atoms, or -O- *. Y 'is a group having a hydroxyl group and a cationic group. M is 1, 2 or 3.) The recording medium according to claim 1, wherein Y in the general formula (1) has a structure represented by the following general formula (3).

(In General Formula (3), R is a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms. P + q is an integer of 1 or more.) The recording medium according to claim 1 or 2, wherein the group represented by the general formula (2) is a group represented by the following general formula (4).

(The group represented by the general formula (4) is bonded to the surface of the inorganic particle at *. In the above formula, R ¹ is an alkyl group or aryl group having 1 to 8 carbon atoms, and X is the following general formula X) A is 1, 2 or 3.)

(In General Formula X, R ^X1 and R ^X2 are each independently an alkylene group or arylene group having 2 to 8 carbon atoms. At least one selected from R ^X3 , R ^X4, and R ^X5 is the following General Formula Q: (Other than that, a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or an aryl group. B is an integer of 0 to 5.)

(In General Formula Q, R ^Q1 , R ^Q2 and R ^Q3 are each independently an alkyl group or aryl group having 1 to 10 carbon atoms.)