EP3578378A1

EP3578378A1 - Recording medium and method for producing recording medium

Info

Publication number: EP3578378A1
Application number: EP19174563.7A
Authority: EP
Inventors: Shinya Yumoto
Original assignee: Canon Inc
Current assignee: Canon Inc
Priority date: 2018-05-31
Filing date: 2019-05-15
Publication date: 2019-12-11
Also published as: CN110549761A; JP2019209686A; CN110549761B; JP7327996B2

Abstract

A recording medium includes an ink-receiving layer that contains a resin (A) having at least one functional group selected from the group consisting of a hydroxy group, a carboxy group, a hydroxyalkyl group, and -C(=O)NR'R", and a compound (B) having a structure represented by a formula (1) or a formula (2). A ratio compound (B)/resin (A) of a content of the compound (B) to a content of the resin (A) in the ink-receiving layer is 0.01 or more and 0.30 or less.

Description

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a recording medium and a method for producing a recording medium.

Description of the Related Art

An ink jet recording method is a recording method used in various fields such as office printing and home printing. The ink jet recording method has been widely used, in particular, because of the ease of colorization and the low cost. With the widespread use of the ink jet recording method, the levels of requirements for the method have also become high, and the realization of a high-quality image, a high speed, and a reduction in the size have been desired for the ink jet recording method. The importance of an ink jet recording medium has also been increasing accordingly.
As an ink jet recording medium that realizes a high-image quality, a recording medium that includes an ink-receiving layer containing inorganic particles as a main component and a hydrophilic polymer as a binder is suitably used because the ink-receiving layer is required to have high transparency and high ink absorbency. In this recording medium, the receiving layer is formed by the inorganic particles, and an ink is absorbed in fine pores formed by the inorganic particles to thereby realize both high transparency and ink absorbency. In general, such an ink jet recording medium is produced by applying a coating liquid that contains the above materials to a substrate and drying the coating liquid. In some cases, cracks are generated during the drying. To address this problem, the generation of cracks can be reduced by increasing the content of the hydrophilic polymer. However, when printing is performed at a high speed, the following phenomenon occurs. When an ink droplet lands on a recording medium, the hydrophilic polymer absorbs water contained in the ink and swells, and consequently inhibits absorption of an ink droplet that subsequently lands. Ink droplets land on the recording medium one after another before the ink is absorbed. Consequently, the ink droplets are combined together on the recording medium, resulting in a problem of generation of streak-like unevenness (also referred to as "beading") on the resulting image.
To address this problem, Japanese Patent Laid-Open No. 2003-191607 proposes a method for suppressing generation of cracks even at a low binder content and suppressing swelling of a water-soluble resin by crosslinking a hydrophilic polymer in an ink-receiving layer with a crosslinking agent.

SUMMARY OF THE INVENTION

The present invention provides a recording medium in which both generation of cracks and generation of beading are suppressed, and coating unevenness is also suppressed. The present invention also provides a method for producing the recording medium.
The present invention in its first aspect provides an ink jet recording medium as specified in claims 1 to 8.
The present invention in its second aspect provides a method for producing the ink jet recording medium as specified in claim 9.
Further features of the present invention will become apparent from the following description of exemplary embodiments.

DESCRIPTION OF THE EMBODIMENTS

According to studies conducted by the inventors of the present invention, it has been found that the use of the crosslinking agent as described in Japanese Patent Laid-Open No. 2003-191607 extremely shortens a period (hereinafter, also referred to as a "pot life") during which viscosity stability of a coating liquid for forming an ink-receiving layer in a process of producing a recording medium can be maintained, which may result in coating unevenness of the coating liquid for forming an ink-receiving layer. Regarding cracks, it has also been found that when alumina, alumina hydrate, or silica is used as inorganic particles, cracks are obviously generated in some cases.
The inventors of the present invention conducted extensive studies in order to suppress both generation of cracks and generation of beading and to suppress coating unevenness and made the present invention.
The present invention will now be described in detail based on embodiments.
In the related art, when a water-soluble resin and a crosslinking agent are used in combination in order to suppress the generation of cracks during drying and beading during printing, it is necessary to dry a coating liquid for forming an ink-receiving layer (hereinafter, also simply referred to as a "coating liquid") in which the water-soluble resin and the crosslinking agent coexist. On the other hand, there is a problem in that when the water-soluble resin and the crosslinking agent coexist before coating, the viscosity increases with time and the pot life is shortened because the water-soluble resin and the crosslinking agent react with each other in an aqueous solution. In contrast, in a crosslinking agent that exhibits a small viscosity increase in an aqueous solution and has a long pot life, the generation of cracks during drying is not sufficiently suppressed. According to a finding based on studies conducted by the inventors of the present invention, it is important that an ink-receiving layer contain a resin (A) having a hydrogen bonding functional group and a compound (B) having a hydrogen bonding functional group, and a ratio of a content of the compound (B) to a content of the resin (A) be adjusted to a particular range (specifically, the ratio compound (B)/resin (A) is 0.01 or more and 0.30 or less). In this case, the pot life of the coating liquid can be extended and cracks during drying can be reduced. The reason for this is considered as follows. When the coating liquid has an appropriate concentration during coating, the resin (A) and the compound (B) are hydrated with water. Thus, a force acting between the resin (A) and the compound (B) is weak, and the viscosity of the coating liquid hardy changes. However, when the concentration is increased by drying, the compound (B) becomes difficult to hydrate and instead interacts with the resin (A) through a hydrogen bond to thereby obtain the effect of crosslinking, and thus cracks can be reduced. Furthermore, some of unsaturated compounds and aromatic compounds have a conjugated system, and molecules of the compound (B) also interact with each other by a π-π interaction. Consequently, a high crosslinking efficiency is achieved.
According to the studies conducted by the inventors of the present invention, it was also found that cracks during drying are generated before the coating liquid is completely dried, that is, in a state where water remains to a certain extent. When the compound (B) has high solubility in water, the timing at which the crosslinking effect during drying generates delays, and the effect described above is obtained after generation of cracks. Therefore, it is considered that the effect of preventing cracks is not obtained in this case. According to the studies conducted by the inventors of the present invention, by using the compound (B) that has the structure represented by the formula (1) or the formula (2) and that is unlikely to dissolve in water in a particular ratio relative to the resin (A) (specifically, in a ratio compound (B)/resin (A) of 0.01 or more and 0.30 or less), the crosslinking effect of the present invention is obtained before generation of cracks during drying, and cracks during drying can be efficiently prevented.

Recording Medium

A recording medium according to an embodiment of the present invention is an ink jet recording medium that includes a substrate and an ink-receiving layer on the substrate.
Components included in the recording medium according to an embodiment of the present invention will now be described.

Substrate

Examples of the substrate include a substrate including base paper alone and a substrate including base paper and a resin layer, that is, base paper coated with a resin. In the present invention, a substrate including base paper and a resin layer is preferably used. In such a case, the resin layer may be disposed only on one surface of the base paper. However, the resin layer is preferably disposed on each of surfaces of the base paper.

Base Paper

The base paper is made by using wood pulp as a main material and optionally adding synthetic pulp, such as polypropylene pulp, or synthetic fibers, such as nylon or polyester fibers. Examples of the wood pulp include leaf bleached kraft pulp (LBKP), leaf bleached sulfite pulp (LBSP), needle bleached kraft pulp (NBKP), needle bleached sulfite pulp (NBSP), leaf dissolving pulp (LDP), needle dissolving pulp (NDP), leaf unbleached kraft pulp (LUKP), and needle unbleached kraft pulp (NUKP). These may be used alone or in combination of two or more thereof, as required. Among various types of wood pulp, LBKP, NBSP, LBSP, NDP, and LDP, which have a high content of a short fiber component, are suitably used. The pulp may be chemical pulp (such as sulfate pulp or sulfite pulp), which has a low impurity content. Pulp subjected to bleaching treatment to improve the degree of whiteness may also be used. A sizing agent, a white pigment, a paper-strengthening agent, a fluorescent brightening agent, a water-retaining agent, a dispersant, a softening agent, and the like may be appropriately added to the base paper.
In the present invention, the base paper preferably has a thickness of 50 µm or more and 130 µm or less, and more preferably 90 µm or more and 120 µm or less. In the present invention, the thickness of the base paper is calculated using the following method. First, a recording medium is cut with a microtome, and the resulting cross section is observed with a scanning electron microscope. Next, the thicknesses at arbitrary 100 points or more of the base paper are measured, and the average thereof is determined as the thickness of the base paper. The thicknesses of other layers in an embodiment of the present invention are also calculated by the same method.
In the present invention, a paper density of the base paper specified in JIS P 8118 is preferably 0.6 g/cm³ or more and 1.2 g/cm³ or less. Furthermore, the paper density is more preferably 0.7 g/cm³ or more and 1.2 g/cm³ or less.

Resin Layer

In the present invention, when base paper is coated with a resin, the resin layer may be provided so as to coat a part of a surface of the base paper. The coverage with a resin layer (area of surface of base paper coated with resin layer/total area of surface of base paper) is preferably 70% or more, more preferably 90% or more, and still more preferably 100%, that is, the entire surface of the base paper is particularly preferably coated with the resin layer.
In the present invention, the resin layer preferably has a thickness of 20 µm or more and 60 µm or less. Furthermore, the the resin layer more preferably has a thickness of 35 µm or more and 50 µm or less. When the resin layer is disposed on both surfaces of the base paper, the thickness of the resin layer on each of the surfaces preferably satisfies the range described above.
The resin used in the resin layer may be a thermoplastic resin. Examples of the thermoplastic resin include acrylic resins, acrylic silicone resins, polyolefin resins, and styrene-butadiene copolymers. Among these resins, polyolefin resins are suitably used. In the present invention, the term "polyolefin resin" refers to a polymer obtained by using an olefin as a monomer. Specific examples thereof include homopolymers of ethylene, propylene, isobutylene, or the like and copolymers thereof. These polyolefin resins may be used alone or in combination of two or more resins, as required. Among these polyolefin resins, polyethylene is suitably used. A low-density polyethylene (LDPE) or a high-density polyethylene (HDPE) is suitably used as polyethylene.
In the present invention, the resin layer may contain, for example, a white pigment, a fluorescent brightening agent, or an ultramarine blue pigment in order to control opacity, the degree of whiteness, or hue thereof. Among these, a white pigment is suitably contained because opacity can be improved. Examples of the white pigment include rutile titanium dioxide and anatase titanium dioxide. In the present invention, the white pigment content of the resin layer is preferably 3 g/m² or more and 30 g/m² or less. When the resin layer is disposed on both surfaces of the base paper, the total white pigment content of the two resin layers preferably satisfies the range described above. The white pigment content of the resin layer is preferably 25% by mass or less based on the resin content. A white pigment content of more than 25% by mass may cause insufficient dispersion stability of the white pigment.
In the present invention, an arithmetic mean roughness Rai of the resin layer specified in JIS B 0601:2001 is preferably 0.12 µm or more and 0.18 µm or less, and more preferably 0.13 µm or more and 0.15 µm or less.
In the present invention, the arithmetic mean roughness Rai of the resin layer is preferably larger than an arithmetic mean roughness Ra₂ of a surface of the recording medium (Ra₁ > Ra₂). A difference ΔRa (= Ra₁ - Ra₂) between the arithmetic mean roughness Rai of the resin layer and the arithmetic mean roughness Ra₂ of a surface of the recording medium is preferably 0.03 µm or more and 0.05 µm or less.
In the present invention, the mean width RSm of roughness profile elements of the resin layer specified in JIS B 0601:2001 is preferably 0.01 mm or more and 0.20 mm or less, and more preferably 0.04 mm or more and 0.15 mm or less.

Ink-Receiving Layer

In the present invention, the ink-receiving layer may be formed of a single layer or two or more layers. The ink-receiving layer may be disposed on only one surface or both surfaces of the substrate. The thickness of the ink-receiving layer on one surface of the substrate is preferably 15 µm or more and 60 µm or less, and more preferably 25 µm or more and 40 µm or less.
Hereafter, materials that can be contained in the ink-receiving layer will be described.

Inorganic Particle

In the present invention, the ink-receiving layer contains at least one inorganic particle selected from the group consisting of alumina, alumina hydrate, and silica. Such an inorganic particle contained in the ink-receiving layer enables ink absorbency of the recording medium to be enhanced. The average particle size of inorganic particles in the ink-receiving layer is preferably 50 nm or less, more preferably 1 nm or more and 30 nm or less, and particularly preferably 3 nm or more and 10 nm or less. In the present invention, the average particle size of inorganic particles in an ink-receiving layer is measured by using an image of a cross section observed with a scanning electron microscope (SEM), the cross section being obtained by cutting an ink-receiving layer of a recording medium in the thickness direction. More specifically, a projected area of a particle observed on the cross section of the ink-receiving layer is measured, and the diameter of a circle having an area equal to the projected area is calculated. The measurement and the calculation are conducted for at least 100 particles, and the average of the obtained results is defined as the average particle size of the inorganic particles in the ink-receiving layer.
In the present invention, the inorganic particles may be used in a coating liquid for forming an ink-receiving layer in a state of being dispersed by a dispersant. The average particle size of the inorganic particles in the dispersed state is preferably 0.1 nm or more and 500 nm or less, more preferably 1.0 nm or more and 300 nm or less, and particularly preferably 10 nm or more and 250 nm or less. The average particle size of the inorganic particles 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 in the ink-receiving layer is preferably 50% by mass or more and 98% by mass or less, and more preferably 70% by mass or more and 96% by mass or less based on the total mass of the ink-receiving layer.
In the present invention, the amount (g/m²) of the inorganic particles applied in the formation of the ink-receiving layer is preferably 8 g/m² or more and 45 g/m² or less. A suitable thickness of the ink-receiving layer is easily obtained within the above range.
Examples of the inorganic particles used in an embodiment of the present invention include, besides alumina, alumina hydrate, and silica mentioned above, titanium dioxide, zeolite, kaoline, talc, hydrotalcite, zinc oxide, zinc hydroxide, aluminum silicate, calcium silicate, magnesium silicate, zirconium oxide, and zirconium hydroxide. These inorganic particles may be used alone or in combination of two or more thereof, as required.
The alumina hydrate suitable for use in the ink-receiving layer is represented by a general formula (X):

Al₂O_3-n(OH)_2n·mH₂O General formula (X)

where 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 are not zero at the same time. Note that m may not be an integer because mH₂O often represents an aqueous phase that can be eliminated and that does not relate to the formation of a crystal lattice. In addition, m can reach zero when the alumina hydrate is heated.
In the present invention, the alumina hydrate can be produced by a known method. Specifically, the alumina hydrate can be produced by, for example, hydrolyzing an aluminum alkoxide, hydrolyzing sodium aluminate, or neutralizing an aqueous sodium aluminate solution by adding an aqueous solution of aluminum sulfate or aluminum chloride.
Known crystal structures of alumina hydrate include amorphous, gibbsite, and boehmite, depending on a heat-treatment temperature. The crystal structures of alumina hydrate can be analyzed by X-ray diffractometry. In the present invention, among these, alumina hydrate having a boehmite structure or amorphous alumina hydrate is suitable. Specific examples thereof include alumina hydrates disclosed in, for example, Japanese Patent Laid-Open Nos. 7-232473 , 8-132731 , 9-66664 , and 9-76628 . Examples of commercially available alumina hydrate include DISPERAL HP14 and HP18 (manufactured by Sasol). These alumina hydrates may be used alone or in combination of two or more thereof, as required.
In the present invention, the specific surface area of alumina hydrate is preferably 100 m²/g or more and 200 m²/g or less, and more preferably 125 m²/g or more and 175 m²/g or less as determined by a BET method. Herein, the BET method is a method in which a molecule or an ion having a known size is allowed to be adsorbed on a surface of a sample, and the specific surface area of the sample is measured on the basis of the amount of adsorption. In the present invention, nitrogen gas is used as a gas that is allowed to be adsorbed on a sample.
The alumina used in the ink-receiving layer may be fumed alumina. Examples of the fumed alumina include γ-alumina, α-alumina, δ-alumina, θ-alumina, and χ-alumina. Among these, γ-alumina is suitably used from the viewpoint of the optical density of an image and the ink absorbency. Specific examples of fumed alumina include AEROXIDE Alu C, Alu 130, and Alu 65 (all of which are manufactured by Evonik Industries AG).
In the present invention, the specific surface area of fumed alumina is preferably 50 m²/g or more, and more preferably 80 m²/g or more as determined by the BET method. The specific surface area is preferably 150 m²/g or less, and more preferably 120 m²/g or less.
The average particle size of fumed alumina is preferably 5 nm or more, and more preferably 11 nm or more. The average primary particle size is preferably 30 nm or less, and more preferably 15 nm or less.
The alumina hydrate and alumina used in an embodiment of the present invention may be blended in the form of an aqueous dispersion liquid in the coating liquid for forming an ink-receiving layer, and an acid may be used as a dispersant thereof. As for the acid, a sulfonic acid represented by a general formula (Y) below is suitably used because an effect of suppressing bleeding of an image is obtained:

R-SO₃H General formula (Y)

where R represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or an alkenyl group having 1 to 4 carbon atoms, and R may be substituted with an oxo group, a halogen atom, an alkoxy group, or an acyl group. In the present invention, the content of the acid is preferably 1.0% by mass or more and 2.0% by mass or less, and more preferably 1.3% by mass or more and 1.6% by mass or less relative to the total content of alumina hydrate and alumina.
The silica used in the ink-receiving layer is broadly classified into two types of silica, namely, wet process silica and dry process (gas-phase process) silica in terms of the production process. In a known wet process, hydrous silica is produced by decomposing a silicate into activated silica with an acid and polymerizing the activated silica to an appropriate extent, followed by sedimentation and aggregation. In another known wet process, colloidal silica is produced by growing spherical particles in water, and the dispersion state of the particles is stabilized in the form of a colloid by, for example, adjusting the pH of the dispersion liquid. In a known dry process (gas-phase process), anhydrous silica is produced by high-temperature gas-phase hydrolysis (flame hydrolysis) of a silicon halide or a process (arc process) in which silica sand and coke are heated, reduced, and gasified by arc in an electric furnace and the resulting gas is oxidized with air. In the present invention, silica obtained by the dry process (gas-phase process) (hereinafter also referred to as "fumed silica") is preferably used. The reason for this is as follows. Fumed silica has a particularly large specific surface area and thus has a particularly high ink absorbency. In addition, since fumed silica has a low refractive index, transparency can be imparted to the ink-receiving layer, thus obtaining good color developability. Specific examples of fumed silica include AEROSIL (manufactured by Nippon Aerosil Co., Ltd.) and REOLOSIL QS series (manufactured by TOKUYAMA Corporation).
In the present invention, the specific surface area of fumed silica is preferably 50 m²/g or more and 400 m²/g or less, and more preferably 200 m²/g or more and 350 m²/g or less as determined by the BET method.
In the present invention, fumed silica may be used in a coating liquid for forming an ink-receiving layer in a state of being dispersed by a dispersant. The particle size of fumed silica in the dispersed state is more preferably 50 nm or more and 300 nm or less. The particle size of fumed silica in the dispersed state can be measured by a dynamic light scattering method.
Examples of the dispersant include cationic resins and polyvalent metal salts.
Examples of the cationic resins include polyethyleneimine resins, polyamine resins, polyamide resins, polyamide-epichlorohydrin resins, polyamine-epichlorohydrin resins, polyamide-polyamine-epichlorohydrin resins, polydiallylamine resins, and dicyandiamide condensates. Examples of the polyvalent metal salts include aluminum compounds such as polyaluminum chloride, polyaluminum acetate, and polyaluminum lactate. These dispersants may be used alone or in combination of two or more thereof. The dispersant can also function as a mordant in the ink-receiving layer.

Resin (A)

In the present invention, the ink-receiving layer contains a resin (A) having at least one functional group selected from the group consisting of a hydroxy group, a carboxy group, a hydroxyalkyl group, and -C(=O)NR'R" where R' and R" are each independently a hydrogen atom, an alkyl group, or an aryl group, and at least one of R' and R" is a hydrogen atom. Herein, -C(=O)NR'R" represents the structure below.
Among the functional groups included in the resin (A), a hydroxy group is preferred. The resin (A) may function as a binder. In the present invention, the term "binder" refers to a material capable of bonding inorganic particles and forming a coating film.
In the present invention, in view of ink absorbency, the content of the resin (A) in the ink-receiving layer is preferably 50% by mass or less, and more preferably 30% by mass or less based on the content of the inorganic particles. In view of a binding property of the ink-receiving layer, the content of the resin (A) is preferably 5% by mass or more, and more preferably 8% by mass or more based on the content of the inorganic particles.
Examples of the resin (A) include starch derivatives such as oxidized starch, etherified starch, and phosphorylated starch; cellulose derivatives such as carboxymethyl cellulose and hydroxyethyl cellulose; proteins such as casein, gelatin, and soy protein; and synthetic resins, i.e., polyvinyl alcohol and derivatives thereof; polycarboxylic acids obtained by using maleic acid, acrylic acid, or methacrylic acid as a monomer and copolymers thereof; resins obtained by cationizing any of the above polymers using a cationic group; resins obtained by cationizing a surface of any of the above polymers using a cationic surfactant; resins obtained by polymerizing a monomer that forms any of the above polymers in the presence of cationic polyvinyl alcohol to distribute polyvinyl alcohol on a surface of the resulting polymer; and resins obtained by polymerizing a monomer that forms any of the above polymers in a dispersion liquid containing cationic colloidal particles suspended therein to distribute the cationic colloidal particles on a surface of the resulting polymer. These resins (A) may be used alone or in combination of two or more thereof, as required.
Among the above resins, polyvinyl alcohol and polyvinyl alcohol derivatives are preferably used as the resin (A). Examples of the polyvinyl alcohol derivatives include cation-modified polyvinyl alcohols, anion-modified polyvinyl alcohols, silanol-modified polyvinyl alcohols, and polyvinyl acetals. The cation-modified polyvinyl alcohols are preferably, for example, polyvinyl alcohol derivatives having any of primary to tertiary amino groups or a quaternary ammonium group in a main chain or a side chain of polyvinyl alcohol, as disclosed in Japanese Patent Laid-Open No. 61-10483 .
Polyvinyl alcohol or a polyvinyl alcohol derivative can be synthesized by, for example, saponifying polyvinyl acetate. The degree of saponification of polyvinyl alcohol or a polyvinyl alcohol derivative is preferably 85% by mole or more and 100% by mole or less, and more preferably 87% by mole or more and 98% by mole or less. The term "degree of saponification" refers to a ratio of the number of moles of hydroxy groups generated by saponification reaction when polyvinyl acetate is saponified to produce polyvinyl alcohol or a polyvinyl alcohol derivative. In the present invention, a value measured by the method described in JIS-K6726 is used as the degree of saponification. The average polymerization degree of the resin (A) is preferably 2,000 or more, and more preferably 2,500 or more and 5,000 or less. In the present invention, a viscosity-average polymerization degree determined by the method described in JIS-K6726 is used as the average polymerization degree.
In preparation of the coating liquid for forming an ink-receiving layer, polyvinyl alcohol or a polyvinyl alcohol derivative may be used in the form of an aqueous solution. In such a case, the polyvinyl alcohol content or the polyvinyl alcohol derivative content of the aqueous solution is preferably 3% by mass or more and 20% by mass or less.

Compound (B)

In the present invention, the ink-receiving layer contains a compound (B) having a structure represented by a formula (1) or a formula (2) below.
In the formula (1), R₁ to R₆ are each independently a hydrogen atom, an alkyl group, an amino group, a hydroxy group, a carboxy group, a hydroxyalkyl group, or - C(=O)NR₁₁R₁₂ (where R₁₁ and R₁₂ are each independently a hydrogen atom, an alkyl group, or an aryl group), and at least two of R₁ to R₆ are each a hydroxy group, a carboxy group, a hydroxyalkyl group, or -C(=O)NR₁₁R₁₂ (where R₁₁ and R₁₂ are each independently a hydrogen atom, an alkyl group, or an aryl group, and at least one of R₁₁ and R₁₂ is a hydrogen atom).
In the formula (2), R₇ to R₁₀ are each independently a hydrogen atom, an alkyl group, an amino group, a carboxy group, a hydroxyalkyl group, or -C(=O)NR₁₃R₁₄ (where R₁₃ and R₁₄ are each independently a hydrogen atom, an alkyl group, or an aryl group), and at least two of R₇ to R₁₀ are each a carboxy group, a hydroxyalkyl group, or -C(=O)NR₁₃R₁₄ (where R₁₃ and R₁₄ are each independently a hydrogen atom, an alkyl group, or an aryl group, and at least one of R₁₃ and R₁₄ is a hydrogen atom).
In the formula (1), the at least two of R₁ to R₆ are each preferably a carboxy group or -C(=O)NR₁₁R₁₂ (where R₁₁ and R₁₂ are each independently a hydrogen atom, an alkyl group, or an aryl group, and at least one of R₁₁ and R₁₂ is a hydrogen atom) and more preferably -C(=O)NR₁₁R₁₂ (where R₁₁ and R₁₂ are each a hydrogen atom). In the formula (2), the at least two of R₇ to R₁₀ are each preferably a carboxy group or - C(=O)NR₁₃R₁₄ (where R₁₃ and R₁₄ are each independently a hydrogen atom, an alkyl group, or an aryl group, and at least one of R₁₃ and R₁₄ is a hydrogen atom) and more preferably -C(=O)NR₁₃R₁₄ (where R₁₃ and R₁₄ are each a hydrogen atom).
The compound (B) preferably has the structure represented by the formula (1) from the viewpoint of further suppressing generation of cracks in the ink-receiving layer.
In the present invention, a ratio (compound (B)/resin (A)) of the content of the compound (B) to the content of the resin (A) in the ink-receiving layer is 0.01 or more and 0.30 or less. The ratio (compound (B)/resin (A)) of the content of the compound (B) to the content of the resin (A) is preferably 0.05 or more and 0.25 or less, and more preferably 0.10 or more and 0.20 or less.
In the present invention, the solubility of the compound (B) in water at 20°C is preferably 0.1 g/100 mL or more and 10.0 g/100 mL or less. The solubility of the compound (B) in water at 20°C is more preferably 5.0 g/100 mL or less from the viewpoint of further suppressing generation of cracks in the ink-receiving layer. Furthermore, in order to more efficiently form the ink-receiving layer without decreasing the concentration of the components in the coating liquid, the solubility of the compound (B) in water at 20°C is more preferably 0.2 g/100 mL or more. Herein, the solubility of the compound (B) in water refers to the maximum weight of the compound (B) soluble in 100 mL of ion-exchange water at 20°C. The method for measuring this solubility is as follows.
First, 10.0 g of a sample to be measured is added to 100 mL of ion-exchange water, and the resulting mixture is stirred at 80°C for one hour to dissolve the sample. Next, the resulting solution in which the sample is dissolved is cooled to 20°C. The sample that remains without being dissolved or is recrystallized is collected, and the weight thereof is determined. The weight of the collected sample is subtracted from 10.0 g, which is the addition amount of the sample, to determine the solubility in water at 20°C. When the solution is cooled to 20°C, the sample is completely dissolved, and the sample that remains without being dissolved or is recrystallized cannot be collected, the solubility of the sample is determined to be more than 10.0 g/100 mL. Crosslinking Agent
In the present invention, the ink-receiving layer may further contain a crosslinking agent within a range that does not affect the pot life of the coating liquid for forming an ink-receiving layer. Examples of the crosslinking agent include aldehyde compounds, melamine compounds, isocyanate compounds, zirconium compounds, amide compounds, aluminum compounds, boric acid, and borates. These crosslinking agents may be used alone or in combination of two or more thereof, as required. The amount of crosslinking agent used can be appropriately adjusted depending on, for example, manufacturing conditions.

Other Additives

In the present invention, the ink-receiving layer may contain additives other than the components described above. Specific examples of the additives include a pH adjustor, a thickener, a fluidity improver, an antifoaming agent, a foam inhibitor, a surfactant, a release agent, a penetrant, a color pigment, a color dye, a fluorescent brightening agent, an ultraviolet absorber, an antioxidant, a preservative, an antifungal agent, a waterproofing agent, a dye fixing agent, a curing agent, and a weather resistant material.

Undercoat Layer

In the present invention, an undercoat layer may be disposed between the substrate and the ink-receiving layer in order to improve adhesion between the substrate and the ink-receiving layer. The undercoat layer may contain a water-soluble polyester resin, gelatin, polyvinyl alcohol, or the like. The undercoat layer preferably has a thickness of 0.01 µm or more and 5 µm or less.

Back Coat Layer

In the present invention, a back coat layer may be disposed on a surface of the substrate, the surface opposite to a surface having an ink-receiving layer thereon, in order to improve handleability, transportability, and scratch resistance during transport in continuous printing when a plurality of recording media are loaded. The back coat layer may contain a white pigment, a binder, and the like. The back coat layer preferably has a thickness of 1 µm or more and 25 µm or less.

Method for Producing Recording Medium

A method for producing the above recording medium according to an embodiment of the present invention includes a step of applying, to a substrate, a coating liquid for forming an ink-receiving layer, and a step of drying the coating liquid for forming an ink-receiving layer, the coating liquid being applied to the substrate. The method for producing the recording medium may further include a step of preparing a coating liquid for forming an ink-receiving layer. The method for producing the recording medium will now be described.

Method for Producing Substrate

In the present invention, a substrate is not particularly limited, and a known substrate capable of being used as an ink jet recording medium can be used.
A commonly used method for making paper can be used as a method for producing base paper. Examples of a paper machine include a Fourdrinier paper machine, a cylinder paper machine, a drum paper machine, and a twin-wire machine. In order to increase the surface flatness and smoothness of the base paper, a surface treatment may be performed by applying heat and pressure during or after a papermaking process. Specific examples of the surface treatment method include a calender treatment such as machine calendering and super calendering.
Examples of a method for providing a resin layer on base paper, that is, a method for coating base paper with a resin include a melt extrusion method, a wet lamination method, and a dry lamination method. Among these methods, a melt extrusion method in which a molten resin is extruded on one surface or both surfaces of base paper to coat the base paper with the resin is suitable. An example of a widely used method is a method (also referred to as an "extrusion coating method") including bringing a resin extruded from an extrusion die into contact with base paper that has been conveyed at a nip point between a nip roller and a cooling roller, and press-bonding the resin and the base paper with a nip to laminate the base paper with a resin layer. In the formation of a resin layer by the melt extrusion method, a pretreatment may be conducted to improve adhesion between base paper and a resin layer. Examples of the pretreatment include an acid etching treatment with a mixture of sulfuric acid and chromic acid, a flame treatment with a gas flame, an ultraviolet irradiation treatment, a corona discharge treatment, a glow discharge treatment, and an anchor coating treatment with an alkyl titanate or the like. Among these pretreatments, a corona discharge treatment is suitable. When the resin layer contains a white pigment, the base paper may be coated with a mixture of a resin and the white pigment.
The method may include a step of winding the substrate prepared as described above around a core in the form of a roll before the formation of the ink-receiving layer. A core having a diameter of 50 mm or more and 300 mm or less is suitably used. The tension during winding is preferably 50 N/m or more and 800 N/m or less. The tension during winding may be constant from the beginning to the end of winding. In order to reduce pressure concentration in the beginning of winding, the tension may be gradually reduced from the beginning to the end of winding.

Method for Forming Ink-Receiving Layer

In the recording medium according to an embodiment of the present invention, the ink-receiving layer can be formed on a substrate by, for example, the following method. First, a coating liquid for forming an ink-receiving layer is prepared. Next, the coating liquid is applied to the substrate and dried to prepare a recording medium according to an embodiment of the present invention. In the method for applying the coating liquid, for example, a curtain coater, a coater with an extrusion system, or a coater with a slide hopper system may be used. The coating liquid may be heated during coating. Examples of the drying method after coating include methods using a hot-air dryer such as a linear tunnel dryer, an arch dryer, an air-loop dryer, or a sine-curve air float dryer; and methods using a dryer that uses infrared rays, heating, microwaves, or the like.
According to an embodiment of the present invention, it is possible to provide a recording medium in which both generation of cracks and generation of beading are suppressed, and coating unevenness is also suppressed. According to an embodiment of the present invention, a method for producing the recording medium can be provided.

EXAMPLES

The present invention will be described in more detail by way of Examples and Comparative Examples. The present invention is not limited to the Examples below without departing from the gist of the present invention. Note that the term "part" in the description of Examples below is on a mass basis unless otherwise stated.

Preparation of Recording Medium

Preparation of Substrate

Eighty parts of LBKP having a Canadian standard freeness (CSF) of 450 mL, 20 parts of NBKP having a Canadian standard freeness (CSF) of 480 mL, 0.60 parts of cationized starch, 10 parts of heavy calcium carbonate, 15 parts of light calcium carbonate, 0.10 parts of an alkyl ketene dimer, and 0.030 parts of cationic polyacrylamide were mixed. Water was added to the resulting mixture such that the mixture had a solid content of 3.0% by mass, thereby preparing a paper raw material. Subsequently, the paper raw material was subjected to paper making with a Fourdrinier paper machine, in which three-stage wet pressing was performed, followed by drying with a multi-cylinder dryer. The resulting paper was then impregnated with an aqueous solution of oxidized starch using a size press machine so as to have a solid content of 1.0 g/m² after drying, and then dried. Furthermore, the paper was subjected to machine calendering to prepare base paper having a basis weight of 170 g/m², a Stockigt sizing degree of 100 seconds, an air permeability of 50 seconds, a Bekk smoothness of 30 seconds, a Gurley stiffness of 11.0 mN, and a thickness of 100 µm. Next, a resin composition containing 70 parts of a low-density polyethylene, 20 parts of a high-density polyethylene, and 10 parts of titanium oxide was applied to one surface of the base paper such that the dry coating amount was 25 g/m². This surface is referred to as a front surface of a substrate. Furthermore, a low-density polyethylene was applied to the other surface of the base paper, thus preparing a substrate.

Preparation of Coating Liquid for Forming Ink-Receiving Layer

Preparation of Alumina Hydrate Dispersion Liquid

To 150.0 g of pure water, 50.0 g of alumina hydrate DISPERAL HP14 (manufactured by Sasol) and 0.75 g of methanesulfonic acid were added. Subsequently, the resulting mixture was stirred with a mixer for 30 minutes to prepare an alumina hydrate dispersion liquid (solid content: 25.0% by mass) containing alumina hydrate as inorganic particles. The alumina hydrate in the alumina hydrate dispersion liquid had an average particle size of 130 nm.

Preparation of Aqueous Polyvinyl Alcohol Solutions 1 to 4

One hundred parts of a polyvinyl alcohol 1 (PVA-235, manufactured by Kuraray Co., Ltd., degree of saponification: 88%, average polymerization degree: 3,500) was added to 1,150 parts of ion-exchange water while stirring. After the completion of the addition, the polyvinyl alcohol 1 was dissolved by heating at 90°C to prepare an aqueous polyvinyl alcohol solution 1 having a solid content of 8.0% by mass.
An aqueous polyvinyl alcohol solution 2 was prepared as in the aqueous polyvinyl alcohol solution 1 except that a polyvinyl alcohol 2 (PVA-224, manufactured by Kuraray Co., Ltd., degree of saponification: 88%, average polymerization degree: 2,400) was used instead of the polyvinyl alcohol 1.
An aqueous polyvinyl alcohol solution 3 was prepared as in the aqueous polyvinyl alcohol solution 1 except that a polyvinyl alcohol 3 (PVA-424, manufactured by Kuraray Co., Ltd., degree of saponification: 80%, average polymerization degree: 2,400) was used instead of the polyvinyl alcohol 1.
An aqueous polyvinyl alcohol solution 4 was prepared as in the aqueous polyvinyl alcohol solution 1 except that a polyvinyl alcohol 4 (PVA-217, manufactured by Kuraray Co., Ltd., degree of saponification: 88%, average polymerization degree: 1,700) was used instead of the polyvinyl alcohol 1.

Preparation of Aqueous Polyvinylacetamide Solution

An aqueous polyvinylacetamide solution (GE191-103, manufactured by Showa Denko K.K., average polymerization degree: 10,000, solid content: 10% by mass) was used without further treatment.

Preparation of Aqueous Polyvinylpyrrolidone Solution

One hundred parts of polyvinylpyrrolidone (K-90, manufactured by Tokyo Chemical Industry Co., Ltd., average polymerization degree: 3,200) was added to 1,150 parts of ion-exchange water while stirring to prepare an aqueous polyvinylpyrrolidone solution having a solid content of 8.0% by mass.

Example 1

A coating liquid 1 for forming an ink-receiving layer was prepared by mixing 31 parts of the aqueous polyvinyl alcohol solution 1 and 0.25 parts of trimesic acid (manufactured by Tokyo Chemical Industry Co., Ltd.) relative to 100 parts of the alumina hydrate dispersion liquid prepared as described above, and stirring the resulting mixture. The coating liquid 1 for forming an ink-receiving layer prepared as described above was applied to the substrate prepared as described above such that the ink-receiving layer had a thickness of 30 µm. After the application, the resulting substrate was further dried with hot air in an oven at 100°C to produce a recording medium 1.

Example 2

A recording medium 2 was produced in the same manner except that the compound contained in the coating liquid 1 for forming an ink-receiving layer was changed from trimesic acid to fumaramide.

Example 3

A recording medium 3 was produced in the same manner except that the compound contained in the coating liquid 1 for forming an ink-receiving layer was changed from trimesic acid to trimesamide.

Example 4

A recording medium 4 was produced in the same manner except that the aqueous polyvinyl alcohol solution 1 used in the coating liquid 1 for forming an ink-receiving layer was changed to the aqueous polyvinyl alcohol solution 2.

Example 5

A recording medium 5 was produced in the same manner except that the compound contained in the coating liquid 1 for forming an ink-receiving layer was changed from trimesic acid to trimellitic acid.

Example 6

A recording medium 6 was produced in the same manner except that the compound contained in the coating liquid 1 for forming an ink-receiving layer was changed from trimesic acid to hemimellitic acid.

Example 7

A recording medium 7 was produced in the same manner except that the compound contained in the coating liquid 1 for forming an ink-receiving layer was changed from trimesic acid to pyromellitic acid.

Example 8

A recording medium 8 was produced in the same manner except that the compound contained in the coating liquid 1 for forming an ink-receiving layer was changed from trimesic acid to fumaric acid.

Example 9

A recording medium 9 was produced in the same manner except that the aqueous polyvinyl alcohol solution 1 used in the coating liquid 1 for forming an ink-receiving layer was changed to the aqueous polyvinyl alcohol solution 3.

Example 10

A recording medium 10 was produced in the same manner except that the aqueous polyvinyl alcohol solution 1 used in the coating liquid 1 for forming an ink-receiving layer was changed to the aqueous polyvinylacetamide solution.

Example 11

A recording medium 11 was produced in the same manner except that the aqueous polyvinyl alcohol solution 1 used in the coating liquid 1 for forming an ink-receiving layer was changed to the aqueous polyvinyl alcohol solution 4.

Example 12

A recording medium 12 was produced in the same manner except that the compound contained in the coating liquid 1 for forming an ink-receiving layer was changed from trimesic acid to gallic acid.

Example 13

A recording medium 13 was produced in the same manner except that the compound contained in the coating liquid 1 for forming an ink-receiving layer was changed from trimesic acid to phloroglucinol.

Example 14

A recording medium 14 was produced in the same manner except that the amount of trimesic acid contained in the coating liquid 1 for forming an ink-receiving layer was changed to 0.125 parts.

Example 15

A recording medium 15 was produced in the same manner except that the amount of trimesic acid contained in the coating liquid 1 for forming an ink-receiving layer was changed to 0.025 parts.

Example 16

A recording medium 16 was produced in the same manner except that the inorganic particles contained in the coating liquid 1 for forming an ink-receiving layer were changed to fumed silica (AEROSIL 300, manufactured by Evonik Industries AG).

Example 17

A recording medium 17 was produced in the same manner except that the inorganic particles contained in the coating liquid 1 for forming an ink-receiving layer were changed to fumed alumina (AEROXIDE Alu C, manufactured by Evonik Industries AG).

Comparative Example 1

A recording medium 18 was produced in the same manner except that the compound contained in the coating liquid 1 for forming an ink-receiving layer was changed from trimesic acid to 1,2,4-trihydroxybenzene.

Comparative Example 2

A recording medium 19 was produced in the same manner except that the compound contained in the coating liquid 1 for forming an ink-receiving layer was changed from trimesic acid to maleic acid.

Comparative Example 3

A recording medium 20 was produced in the same manner except that the compound contained in the coating liquid 1 for forming an ink-receiving layer was changed from trimesic acid to benzoic acid.

Comparative Example 4

A recording medium 21 was produced in the same manner except that the aqueous polyvinyl alcohol solution 1 used in the coating liquid 1 for forming an ink-receiving layer was changed to the aqueous polyvinylpyrrolidone solution. Comparative Example 5
A recording medium 22 was produced in the same manner except that the compound contained in the coating liquid 1 for forming an ink-receiving layer was changed from trimesic acid to adipic acid.

Comparative Example 6

A recording medium 23 was produced in the same manner except that trimesic acid was not contained in the coating liquid 1 for forming an ink-receiving layer.

Comparative Example 7

A recording medium 24 was produced in the same manner except that the compound contained in the coating liquid 1 for forming an ink-receiving layer was changed from trimesic acid to ZrOCl₂ (product name: Zircozol ZC-20, manufactured by Daiichi Kigenso Kagaku Kogyo Co., Ltd).

Comparative Example 8

A recording medium 25 was produced in the same manner except that the compound contained in the coating liquid 1 for forming an ink-receiving layer was changed from trimesic acid to ZrO(C₂H₃O₂)₂ (product name: Zircozol ZA-20, manufactured by Daiichi Kigenso Kagaku Kogyo Co., Ltd).

Comparative Example 9

A recording medium 26 was produced in the same manner except that the compound contained in the coating liquid 1 for forming an ink-receiving layer was changed from trimesic acid to boric acid (manufactured by FUJIFILM Wako Pure Chemical Corporation).

Tables 1 and 2 below show structures of the ink-receiving layers of the recording media 1 to 26 prepared by using coating liquids 1 to 26 for forming ink-receiving layers.

Table 1

Recording medium	Coating liquid for forming ink-receiving layer	Ink-receiving layer
		Inorganic particle	Resin (A)
		Type	Type	Average polymerization degree	Content (parts by mass)	Degree of saponification (mol%)
Recording medium 1	Coating liquid 1	HP14	PVA235	3500	10	88%
Recording medium 2	Coating liquid 2	HP14	PVA235	3500	10	88%
Recording medium 3	Coating liquid 3	HP14	PVA235	3500	10	88%
Recording medium 4	Coating liquid 4	HP14	PVA224	2400	10	88%
Recording medium 5	Coating liquid 5	HP14	PVA235	3500	10	88%
Recording medium 6	Coating liquid 6	HP14	PVA235	3500	10	88%
Recording medium 7	Coating liquid 7	HP14	PVA235	3500	10	88%
Recording medium 8	Coating liquid 8	HP14	PVA235	3500	10	88%
Recording medium 9	Coating liquid 9	HP14	PVA424	2400	10	80%
Recording medium 10	Coating liquid 10	HP14	PNVA	10000	10	100%
Recording medium 11	Coating liquid 11	HP14	PVA217	1700	10	88%
Recording medium 12	Coating liquid 12	HP14	PVA235	3500	10	88%
Recording medium 13	Coating liquid 13	HP14	PVA235	3500	10	88%
Recording medium 14	Coating liquid 14	HP14	PVA235	3500	10	88%
Recording medium 15	Coating liquid 15	HP14	PVA235	3500	10	88%
Recording medium 16	Coating liquid 16	AEROSIL300	PVA235	3500	10	88%
Recording medium 17	Coating liquid 17	AEROXIDE Alu C	PVA235	3500	10	88%
Recording medium 18	Coating liquid 18	HP14	PVA235	3500	10	88%
Recording medium 19	Coating liquid 19	HP14	PVA235	3500	10	88%
Recording medium 20	Coating liquid 20	HP14	PVA235	3500	10	88%
Recording medium 21	Coating liquid 21	HP14	PVP	3200	10	-
Recording medium 22	Coating liquid 22	HP14	PVA235	3500	10	88%
Recording medium 23	Coating liquid 23	HP14	PVA235	3500	10	88%
Recording medium 24	Coating liquid 24	HP14	PVA235	3500	10	88%
Recording medium 25	Coating liquid 25	HP14	PVA235	3500	10	88%
Recording medium 26	Coating liquid 26	HP14	PVA235	3500	10	88%

Table 2

Recording medium	Coating liquid for forming ink-receiving layer	Ink-receiving layer
		Compound (B)						Thickness (µm)
		Type	Structural formula	Type of functional group	Number of functional groups in left column	Solubility in water at 20°C (g/100 mL)	Compound (B)/Resin (A)	Thickness (µm)
Recording medium 1	Coating liquid 1	Trimesic acid	Formula (1)	Carboxy group	3	0.5	0.10	30
Recording medium 2	Coating liquid 2	Fumaramide	Formula (2)	-C(=O)NH₂	2	0.2	0.10	30
Recording medium 3	Coating liquid 3	Trimesamide	Formula (1)	-C(=O)NH₂	3	0.2	0.10	30
Recording medium 4	Coating liquid 4	Trimesic acid	Formula (1)	Carboxy group	3	0.5	0.10	30
Recording medium 5	Coating liquid 5	Trimellitic acid	Formula (1)	Carboxy group	3	2.0	0.10	30
Recording medium 6	Coating liquid 6	Hemimellitic acid	Formula (1)	Carboxy group	3	2.0	0.10	30
Recording medium 7	Coating liquid 7	Pyromellitic acid	Formula (1)	Carboxy group	4	1.5	0.10	30
Recording medium 8	Coating liquid 8	Fumaric acid	Formula (2)	Carboxy group	2	0.5	0.10	30
Recording medium 9	Coating liquid 9	Trimesic acid	Formula (1)	Carboxy group	3	0.5	0.10	30
Recording medium 10	Coating liquid 10	Trimesic acid	Formula (1)	Carboxy group	3	0.5	0.10	30
Recording medium 11	Coating liquid 11	Trimesic acid	Formula (1)	Carboxy group	3	0.5	0.10	30
Recording medium 12	Coating liquid 12	Gallic acid	Formula (1)	Carboxy group	1	1.0	0.10	30
Recording medium 12	Coating liquid 12	Gallic acid	Formula (1)	Hydroxy group	3	1.0	0.10	30
Recording medium 13	Coating liquid 13	Phloroglucinol	Formula (1)	Hydroxy group	3	1.0	0.10	30
Recording medium 14	Coating liquid 14	Trimesic acid	Formula (1)	Carboxy group	3	0.5	0.05	30
Recording medium 15	Coating liquid 15	Trimesic acid	Formula (1)	Carboxy group	3	0.5	0.01	30
Recording medium 16	Coating liquid 16	Trimesic acid	Formula (1)	Carboxy group	3	0.5	0.10	30
Recording medium 17	Coating liquid 17	Trimesic acid	Formula (1)	Carboxy group	3	0.5	0.10	30
Recording medium 18	Coating liquid 18	1,2,4-Trihydroxybenzene	Formula (1)	Hydroxy group	3	>10.0	0.10	30
Recording medium 19	Coating liquid 19	Maleic acid	Formula (2)	Carboxy group	2	>10.0	0.10	30
Recording medium 20	Coating liquid 20	Benzoic acid	Formula (1)	Carboxy group	1	0.2	0.10	30
Recording medium 21	Coating liquid 21	Trimesic acid	Formula (1)	Carboxy group	3	0.5	0.10	30
Recording medium 22	Coating liquid 22	Adipic acid	Formula (2)	Carboxy group	2	1.5	0.10	30
Recording medium 23	Coating liquid 23	None	-	-	-	-	-	30
Recording medium 24	Coating liquid 24	ZrOCl₂	-	-	-	>10	-	30
Recording medium 25	Coating liquid 25	ZrO(C₂H₃O₂)₂	-	-	-	>10	-	30
Recording medium 26	Coating liquid 26	Boric acid	-	Hydroxy group	3	6.0	-	30

Evaluation

In the present invention, 5 and 4 of the evaluation criteria of each of the evaluation items below are determined as preferred levels, 3 and 2 of the evaluation criteria are determined as acceptable levels, and 1 of the evaluation criteria is determined as an unacceptable level. In each of the evaluations described below, when an image was recorded on a recording medium, the recording was conducted by using an ink jet recording device PIXUS MP990 (manufactured by CANON KABUSHIKI KAISHA) on which an ink cartridge BCI-321 (manufactured by CANON KABUSHIKI KAISHA) was mounted. The recording was conducted under the conditions of a temperature of 23°C and a relative humidity of 50%. In the above ink jet recording device, an image that is recorded under the condition that one ink droplet having a weight of about 11 ng is provided in a unit area of 1/600 inch × 1/600 inch at a resolution of 600 dpi × 600 dpi is defined as a recording duty of 100%. Table 3 shows the evaluation results.

Evaluation of Crack Resistance

A coating liquid for forming an ink-receiving layer was applied to a substrate and then dried. Cracks on a surface of the ink-receiving layer were observed visually and with an optical microscope at a magnification of 100 and evaluated in accordance with the criteria described below.

5: No crack is observed on the surface of the ink-receiving layer in observation with an optical microscope at a magnification of 100.
4: Cracks are slightly observed on the surface of the ink-receiving layer in observation with an optical microscope at a magnification of 100.
3: A large number of cracks are observed on the surface of the ink-receiving layer in observation with an optical microscope at a magnification of 100 but are not identified by visual observation.
2: Cracks are slightly observed on the surface of the ink-receiving layer by visual observation.
1: A large number of cracks are observed on the surface of the ink-receiving layer by visual observation.

Evaluation of Beading Resistance

Four green solid images having a recording duty of 150%, 200%, 250%, and 300% were recorded on a recording medium by using the above ink jet recording device. The occurrence or non-occurrence of the beading phenomenon in the obtained image was examined by visual observation to evaluate beading resistance. When the beading phenomenon does not occur even in an image having a high recording duty, the ink absorbency is determined to be high. The evaluation criteria are as follows.

5: No beading phenomenon occurred even in the image having a recording duty of 300%.
4: Although the beading phenomenon occurred in the image having a recording duty of 300%, no beading phenomenon occurred in the image having a recording duty of 250%.
3: Although the beading phenomenon occurred in the image having a recording duty of 250%, no beading phenomenon occurred in the image having a recording duty of 200%.
2: Although the beading phenomenon occurred in the image having a recording duty of 200%, no beading phenomenon occurred in the image having a recording duty of 150%.
1: The beading phenomenon occurred even in the image having a recording duty of 150%.

Evaluation of Coating Unevenness

After preparation of a coating liquid for forming an ink-receiving layer, the coating liquid for forming an ink-receiving layer was stored at 25°C for 15 minutes, 1 hour, 6 hours, or 24 hours. Subsequently, the coating liquid stored for each time was applied to a recording medium, and whether coating unevenness was generated or not was examined. The evaluation criteria are as follows.

5: No coating unevenness was generated even when the coating liquid for forming an ink-receiving layer was stored for 24 hours and then applied.
4: Although no coating unevenness was generated when the coating liquid for forming an ink-receiving layer was stored for 6 hours and then applied, coating unevenness was generated in application after storage for 24 hours.
3: Although no coating unevenness was generated when the coating liquid for forming an ink-receiving layer was stored for 1 hour and then applied, coating unevenness was generated in application after storage for 6 hours.
2: Although no coating unevenness was generated when the coating liquid for forming an ink-receiving layer was stored for 15 minutes and then applied, coating unevenness was generated in application after storage for 1 hour.
1: Coating unevenness was generated in application after the coating liquid for forming an ink-receiving layer was stored for 15 minutes.

Table 3

Example, Comparative Example	Recording medium	Evaluation results
Example, Comparative Example	Recording medium	Crack resistance	Beading resistance	Coating unevenness
Example 1	Recording medium 1	4	4	5
Example 2	Recording medium 2	4	5	5
Example 3	Recording medium 3	4	5	5
Example 4	Recording medium 4	3	4	5
Example 5	Recording medium 5	3	3	5
Example 6	Recording medium 6	3	3	5
Example 7	Recording medium 7	3	3	5
Example 8	Recording medium 8	4	3	5
Example 9	Recording medium 9	3	4	5
Example 10	Recording medium 10	3	4	5
Example 11	Recording medium 11	3	4	5
Example 12	Recording medium 12	2	2	5
Example 13	Recording medium 13	2	2	5
Example 14	Recording medium 14	4	4	5
Example 15	Recording medium 15	3	4	5
Example 16	Recording medium 16	3	4	5
Example 17	Recording medium 17	3	4	5
Comparative Example 1	Recording medium 18	1	2	5
Comparative Example 2	Recording medium 19	1	1	5
Comparative Example 3	Recording medium 20	1	1	5
Comparative Example 4	Recording medium 21	1	1	5
Comparative Example 5	Recording medium 22	1	1	5
Comparative Example 6	Recording medium 23	1	1	5
Comparative Example 7	Recording medium 24	4	1	1
Comparative Example 8	Recording medium 25	1	4	5
Comparative Example 9	Recording medium 26	5	4	1

While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
A recording medium includes an ink-receiving layer that contains a resin (A) having at least one functional group selected from the group consisting of a hydroxy group, a carboxy group, a hydroxyalkyl group, and -C(=O)NR'R", and a compound (B) having a structure represented by a formula (1) or a formula (2). A ratio compound (B)/resin (A) of a content of the compound (B) to a content of the resin (A) in the ink-receiving layer is 0.01 or more and 0.30 or less.

Claims

An ink jet recording medium comprising:
a substrate; and

an ink-receiving layer on the substrate,

wherein the ink-receiving layer contains
at least one inorganic particle selected from the group consisting of alumina, alumina hydrate, and silica,

a resin (A) having at least one functional group selected from the group consisting of a hydroxy group, a carboxy group, a hydroxyalkyl group, and - C(=O)NR'R" where R' and R" are each independently a hydrogen atom, an alkyl group, or an aryl group, and at least one of R' and R" is a hydrogen atom, and

a compound (B) having a structure represented by a formula (1) or a formula (2), and

a ratio compound (B)/resin (A) of a content of the compound (B) to a content of the resin (A) in the ink-receiving layer is 0.01 or more and 0.30 or less:
wherein R₁ to R₆ are each independently a hydrogen atom, an alkyl group, an amino group, a hydroxy group, a carboxy group, a hydroxyalkyl group, or - C(=O)NR₁₁R₁₂ where R₁₁ and R₁₂ are each independently a hydrogen atom, an alkyl group, or an aryl group, and at least two of R₁ to R₆ are each a hydroxy group, a carboxy group, a hydroxyalkyl group, or -C(=O)NR₁₁R₁₂ where R₁₁ and R₁₂ are each independently a hydrogen atom, an alkyl group, or an aryl group, and at least one of R₁₁ and R₁₂ is a hydrogen atom;
wherein R₇ to Rio are each independently a hydrogen atom, an alkyl group, an amino group, a carboxy group, a hydroxyalkyl group, or -C(=O)NR₁₃R₁₄ where R₁₃ and R₁₄ are each independently a hydrogen atom, an alkyl group, or an aryl group, and at least two of R₇ to Rio are each a carboxy group, a hydroxyalkyl group, or - C(=O)NR₁₃R₁₄ where R₁₃ and R₁₄ are each independently a hydrogen atom, an alkyl group, or an aryl group, and at least one of R₁₃ and R₁₄ is a hydrogen atom.
The ink jet recording medium according to Claim 1, wherein the resin (A) has an average polymerization degree of 2,000 or more.
The ink jet recording medium according to Claim 1 or 2, wherein the resin (A) is polyvinyl alcohol or a derivative of polyvinyl alcohol.
The ink jet recording medium according to Claim 3, wherein the polyvinyl alcohol or the derivative of polyvinyl alcohol has a degree of saponification of 85% by mole or more and 100% by mole or less.
The ink jet recording medium according to any one of Claims 1 to 4, wherein the compound (B) has a solubility of 0.1 g/100 mL or more and 10.0 g/100 mL or less in water at 20°C.
The ink jet recording medium according to any one of Claims 1 to 5, wherein in the formula (1), the at least two of R₁ to R₆ are each a carboxy group or - C(=O)NR₁₁R₁₂ where R₁₁ and R₁₂ are each independently a hydrogen atom, an alkyl group, or an aryl group, and at least one of R₁₁ and R₁₂ is a hydrogen atom.
The ink jet recording medium according to any one of Claims 1 to 5, wherein in the formula (2), the at least two of R₇ to Rio are each a carboxy group or - C(=O)NR₁₃R₁₄ where R₁₃ and R₁₄ are each independently a hydrogen atom, an alkyl group, or an aryl group, and at least one of R₁₃ and R₁₄ is a hydrogen atom.
The ink jet recording medium according to any one of Claims 1 to 7, wherein the compound (B) is fumaramide, trimesic acid, or trimesamide.
A method for producing the ink jet recording medium according to any one of Claims 1 to 8, the method comprising:
a step of applying, to a substrate, a coating liquid for forming an ink-receiving layer; and

a step of drying the coating liquid for forming an ink-receiving layer, the coating liquid being applied to the substrate,

wherein the coating liquid for forming an ink-receiving layer contains the resin (A), the compound (B), and water.