JP2005313490A - Particulate dispersion, and medium to be recorded, using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a particulate dispersion, the particle diameter and viscosity of which can be controlled in a desired range under relatively easy agitating conditions and which can form a stable high-quality ink receiving layer; and to provide a medium to be recorded, which suppresses an irritating odor (or an unpleasant odor) generated in the recording of an image and where a high-quality image can be recorded. <P>SOLUTION: In the preparation of a particulate dispersion wherein inorganic particulates are dispersed in an aqueous solvent, a diallylamine-based polymer and a hydroxy acid are used. Additionally, the ink receiving layer is formed by using the dispersion, and the medium to be recording is manufactured. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fine particle dispersion suitable for producing an ink jet recording medium, and a recording medium using the same, and particularly has excellent dispersibility and stability over time, and transparency of an ink receiving layer to be formed. And a fine particle dispersion excellent in smoothness and film properties, and a recording medium capable of recording high-quality images by suppressing an irritating odor (or unpleasant odor) generated from an ink receiving layer when recording an image .

  In the inkjet recording method, ink droplets adhere to a recording medium such as paper by various operating principles, and at the same time, the solvent component of the ink penetrates into the recording medium or evaporates, so that the color material component is covered. This is a recording method that deposits on a recording medium and records images, characters, and the like (hereinafter simply referred to as “images”). In addition, the ink jet recording system is characterized in that it has excellent high-speed printability, low noise, and flexibility in recording patterns, can easily perform multi-coloring, and does not require development and image fixing. In particular, an image formed by a multi-color ink jet method can obtain a recording that is comparable to that of a multi-color printing by a plate making method or a printing by a color photographic method. In recent years, it has rapidly spread as an image recording apparatus for various information devices because it has an advantage that the printing cost is lower than that of the printing technique and the photographic technique.

In such an ink jet recording system, in order to improve recording characteristics such as high-speed recording, high definition, or full color, the recording apparatus and the recording method have been improved. Advanced characteristics have been required. In other words, in order to obtain high-quality recorded images with high resolution comparable to silver halide photographs,
(1) The print dot density is high and vivid and bright colors can be produced;
(2) High contrast,
(3) having high ink absorptivity so that the ink does not flow out or bleed even when the print dots overlap;
(4) The ink does not increase more than necessary in the lateral direction and has a printed dot shape close to a perfect circle,
(5) It has been demanded that the periphery of the dot is smooth and unblurred.

  Several proposals have been made for these requirements. For example, Patent Document 1 discloses a general paper type ink jet recording paper in which a low-size base paper is thinly coated with a surface processing paint to improve ink absorbability, and Patent Documents 2 and 3 include the general paper type ink jet recording paper. In order to improve the reproducibility of the dot shape, density or color tone, which has been a drawback, an example in which amorphous silica is used as a pigment in the coating layer is disclosed. Recently, a recording medium in which fine alumina hydrate is coated on a support together with a water-soluble binder has been proposed as an ink-absorbing layer having improved ink absorbability, image glossiness and transparency. For example, it is indicated by patent documents 4-6.

  Alumina hydrate is positive because it has a positive charge and good fixability of the dye in the ink, but it is considered an ideal pigment. It is necessary to form an ink receiving layer using a coating liquid kept in a well dispersed state, and an acid is generally added as a peptizer in an aqueous sol of alumina hydrate. For example, Patent Documents 7 and 8 disclose a method for obtaining a well-dispersed transparent sol by adding an organic acid such as acetic acid, formic acid or oxalic acid, or an inorganic acid such as nitric acid, hydrochloric acid or sulfuric acid.

  However, among such peptizers, inorganic acids are particularly unfavorable in terms of equipment safety due to their strong metal corrosivity. In addition, although organic acids have relatively few problems such as chemical safety and corrosiveness, their boiling points are higher than those of inorganic acids, and substrates with low heat resistance such as paper or film coated with resin are used as a support. In this case, since the ink cannot be dried at a high temperature, an acid remains in the ink receiving layer, which may cause an irritating odor (or an unpleasant odor). Furthermore, when the acid concentration remaining in the ink receiving layer increases, the pH of the ink receiving layer itself decreases, and beading (a phenomenon in which coloring material aggregates in granular form on the surface of the ink receiving layer and causes density unevenness) occurs. As a result, the image quality may deteriorate significantly.

  Instead of using acid as a peptizer, the above problems can be avoided by making dispersions using various surfactants or polymer dispersants. Bubbles are generated in the liquid, which may cause coating defects. In addition, when a polymeric dispersant is used, a relatively strong shearing force and a long period of stirring are required to peptize the alumina hydrate to primary particles, and a uniform dispersion without aggregates. Therefore, it was difficult to stably form a high-quality ink-receiving layer.

JP 52-53012 A JP-A-55-51583 Japanese Patent Laid-Open No. 64-11877 JP-A-2-276670 JP-A-7-76161 JP 11-34484 A Japanese Patent Laid-Open No. 4-67985 Japanese Patent Laid-Open No. 9-24666

  The present invention has been made in view of the above circumstances, and can stably control the particle diameter and viscosity within a desired range under relatively gentle stirring conditions, and can stably provide a high-quality ink receiving layer. By providing the fine particle dispersion that can be formed, and forming an ink receiving layer using the dispersion, the irritating odor (or unpleasant odor) that occurs when recording an image is suppressed, and high quality is achieved. It is an object to provide a recording medium capable of forming an image.

  The inventors of the present invention have a fine particle dispersion that can form an ink receiving layer that is excellent in dispersibility and stability over time, and that is excellent in transparency, smoothness, and film property, and is generated from the ink receiving layer when recording an image. As a result of intensive investigations to obtain a recording medium having high quality image characteristics with no irritating odor (or unpleasant odor), when preparing a fine particle dispersion, a specific cationic polymer and a small amount of hydroxy It has been found that the above-mentioned problems can be solved by using an acid, and the present invention has been completed.

  That is, the present invention provides a fine particle dispersion characterized in that, in a fine particle dispersion in which inorganic fine particles are dispersed in an aqueous solvent, the dispersion contains a diallylamine-based polymer and a hydroxy acid.

（式中、Ｒ¹、Ｒ²は水素原子またはアルキル基を表し、Ｒ¹とＲ²は同一でも異なっていてもよい。また、Ａは−ＣＨ₂−または−ＣＨ₂−ＳＯ₂−を、Ｂはアリルアミン塩単位、アクリルアミド単位またはメタクリルアミド単位を表し、Ｘ^-はハロゲンイオン、硫酸アニオン、スルホン酸アニオン、アルキルスルホン酸アニオン、酢酸アニオン、アルキルカルボン酸アニオンまたは燐酸アニオンを表す。ｍおよびｎは重合度を示す整数である。） In the present invention, the inorganic fine particles are alumina and / or alumina hydrate; the diallylamine polymer is at least one cationic polymer selected from the following general formula (1) or general formula (2) And the hydroxy acid is preferably a monocarboxylic acid.

(Wherein R ¹ and R ² represent a hydrogen atom or an alkyl group, R ¹ and R ² may be the same or different. A represents —CH ₂ — or —CH ₂ —SO ₂ —, B represents an allylamine salt unit, an acrylamide unit or a methacrylamide unit, and X ⁻ represents a halogen ion, a sulfate anion, a sulfonate anion, an alkyl sulfonate anion, an acetate anion, an alkyl carboxylate anion, or a phosphate anion. (It is an integer indicating the degree of polymerization.)

  Further, the present invention provides a recording medium having an ink receiving layer provided on at least one surface of a support, wherein the ink receiving layer is formed using a fine particle dispersion containing a diallylamine polymer and a hydroxy acid. A recording medium is provided. The fine particle dispersion used here is preferably the fine particle dispersion of the present invention.

With the above configuration, a fine particle dispersion excellent in dispersibility and stability over time can be obtained, and further, an ink-receiving layer is formed using the dispersion, thereby generating a stimulus generated when an image is recorded. It is possible to produce a recording medium having an ink receiving layer that is suppressed in odor (or unpleasant odor) and beading and has excellent ink absorbability.
That is, when preparing the fine particle dispersion, a fine particle dispersion in which the particle size and viscosity are controlled within a desired range under relatively gentle stirring conditions by using a diallylamine polymer and a hydroxy acid is provided. I was able to. In addition, by forming an ink receiving layer using the dispersion liquid, an unpleasant odor generated when an image is recorded can be suppressed, and a recording medium capable of forming a high-quality image can be provided.

Next, the present invention will be described in more detail with reference to the best mode for carrying out the invention.
The inorganic fine particles used in the present invention are preferably fine particles having high ink absorbability, excellent color developability and capable of forming a high-quality image. Examples of such inorganic fine particles include calcium carbonate, magnesium carbonate, kaolin, clay, talc, hydrotalcite, aluminum silicate, calcium silicate, magnesium silicate, diatomaceous earth, alumina, colloidal alumina, aluminum hydroxide, and alumina hydrate. Products, synthetic amorphous silica, colloidal silica, lithopone, zeolite, and the like, and these can be used alone or in combination.

  As the form of the inorganic fine particles, in order to obtain a highly glossy and highly transparent ink-receiving layer, the average particle size is preferably in the range of 100 nm to 500 nm, more preferably in the range of 100 nm to 300 nm. When the average particle size of the inorganic fine particles is smaller than 100 nm, the ink absorbability is remarkably lowered, and ink bleeding or beading occurs when printing is performed with a printer having a large discharge amount. On the other hand, when the average particle size is larger than 500 nm, the transparency of the ink receiving layer is lowered, and the print density and gloss of the image may be lowered. In addition, the average particle diameter as used in the field of this invention is measured by the dynamic light-scattering method, "A structure of a polymer (2) Scattering experiment and morphology observation Chapter 1 light scattering" (Kyoritsu Publishing Society of Polymer Sciences), Chem. Phys., 70 (B), 15 Apl., 3965 (1979).

The inorganic fine particles preferably have a BET specific surface area of 50 to 500 m ² / g. When the BET specific surface area is less than 50 m ² / g, since the particles are large, the transparency of the ink receiving layer is impaired, the image density is lowered, and the printed matter tends to be white and dull. In addition, when the BET specific surface area exceeds 500 m ² / g, for example, a large amount of acid is required as a peptizer to stably disperse inorganic fine particles, which is not preferable. More preferred is a range of 50 to 250 m ² / g, which is excellent in ink absorbability, beading, smoothness and the like.

  In the present invention, among the above-described inorganic fine particles, alumina fine particles such as alumina and alumina hydrate can be preferably used, and the ink receiving layer to be formed is excellent in transparency and smoothness, and has finer voids. Can be formed in the ink-receiving layer, and an alumina hydrate having a boehmite structure or a pseudoboehmite structure is more preferably used.

The alumina hydrate used in the present invention is defined by the following general formula (3).
Al ₂ O _3-n (OH) _2n · mH ₂ O (3)
In the formula, n represents any one of integers of 0, 1, 2, or 3, and m represents a value of 0 to 10, preferably 0 to 5. 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 can take a non-integer value. Also, when this type of alumina hydrate is calcined, m can reach a value of zero.

  In general, an alumina hydrate crystal having a boehmite structure is a layered compound having a (020) plane forming a giant plane, and exhibits a diffraction peak peculiar to an X-ray diffraction pattern. As the boehmite structure, a structure containing excess water between layers of the (020) plane, which is called pseudo boehmite in addition to perfect boehmite, can also be adopted. Although the X-ray diffraction pattern of this pseudoboehmite shows a broader diffraction peak than that of perfect boehmite, perfect boehmite and pseudoboehmite are not clearly distinguishable. Including alumina hydrate showing a boehmite structure.

  Although it does not specifically limit as a manufacturing method of an alumina hydrate, For example, any methods, such as a buyer method and a light van pyrolysis method, are employable. A particularly preferable method is a method in which an acid is added to a long-chain aluminum alkoxide for hydrolysis. Here, the long-chain aluminum alkoxide is, for example, an alkoxide having 5 or more carbon atoms, and when an alkoxide having 12 to 22 carbon atoms is used, the removal of alcohol as described later, and the alumina hydrate Since shape control becomes easy, it is preferable. The method based on the hydrolysis of the aluminum alkoxide has an advantage that impurities such as various ions are less likely to be mixed as compared with a method for producing alumina hydrogel or cationic alumina. Furthermore, since long-chain aluminum alkoxide is easy to remove long-chain alcohol after hydrolysis, for example, compared with the case of using short-chain alkoxide such as aluminum isoproxide, the alcohol hydrate is completely dealcoholized. There is also the advantage that it can be done.

  The alumina hydrate obtained by the above method can control the particle shape of the alumina hydrate to a specific range by adjusting the conditions of the aging process for growing the particles through the hydrothermal synthesis process. When the aging time is appropriately set, primary particles of alumina hydrate having a relatively uniform particle diameter grow. The sol obtained here can be used as a dispersion as it is by adding an acid as a peptizer, but in order to further improve the dispersibility of alumina hydrate in water, the sol is spray-dried, etc. After pulverizing by this method, it is preferable to add an acid to obtain a dispersion.

  The inorganic fine particles used in the present invention can be easily peptized by using a large amount of acid to form a uniform dispersion. However, when a known inorganic acid or organic acid is used as the peptizer, the safety on the equipment due to the metal corrosion as described above, the unpleasant odor due to the acid remaining in the ink receiving layer, the occurrence of beading, etc. Is a problem. Therefore, in the present invention, a fine particle dispersion is produced by using a diallylamine polymer and a hydroxy acid in combination and dispersing and peptizing inorganic fine particles. As a result, even if the amount of acid used is reduced, a finely divided fine particle dispersion with low viscosity can be prepared. Further, by using a hydroxy acid having a relatively high boiling point and having no unpleasant odor, the odor from the ink receiving layer is suppressed, and furthermore, the acid concentration in the ink receiving layer is suppressed to a low level, thereby reducing beading. It is possible to form an ink-receiving layer that does not generate mist.

  The concentration of the inorganic fine particles in the fine particle dispersion is preferably 5 to 40% by mass and more preferably 10 to 30% by mass with respect to the total mass of the dispersion. When the concentration of the inorganic fine particles is low, the solid content concentration of the coating solution to be finally prepared is lowered, and a lot of time and energy are required for drying after coating, so that the production efficiency is lowered. Moreover, when the density | concentration of an inorganic fine particle is too high, since the viscosity of a dispersion liquid will become high and handling will be applied to a post process, it is unpreferable.

  The hydroxy acid used in the present invention is a compound having a carboxyl group (—COOH) and an alcoholic hydroxyl group (—OH) in one molecule, and is also called an oxyacid. Examples of such compounds include monocarboxylic acids such as glycolic acid, lactic acid, 2-hydroxyisobutyric acid, and 2-ethyl-2-hydroxybutyric acid, and polyvalent carboxylic acids such as malic acid, tartaric acid, and citric acid. These can be used alone or in combination. In addition, when polyvalent carboxylic acid is used in the said hydroxy acid, since the viscosity at the time of fine particle dispersion | distribution may become high, it is preferable to use the hydroxy acid which consists of monocarboxylic acid in this invention.

  The amount of hydroxy acid used varies depending on the amount of inorganic fine particles used, the particle diameter, and the specific surface area, but may be the minimum amount necessary for peptizing the fine particles in a water-soluble solvent, and is preferable for inorganic fine particles. Is preferably in the range of 0.1 to 10 mass%, more preferably 0.5 to 5 mass%. When the amount used is less than 0.1% by mass, the viscosity of the dispersion may increase with time, which is not preferable. On the other hand, when the amount used exceeds 10% by mass, the dispersion effect does not increase any more, causing problems such as a decrease in ink absorbability and occurrence of beading. In the present invention, a known peptizer (organic acid or inorganic acid) may be used in combination with the hydroxy acid.

式中、Ｒ¹、Ｒ²は水素原子またはアルキル基を表し、Ｒ¹とＲ²は同一でも異なっていてもよい。また、Ａは−ＣＨ₂−または−ＣＨ₂−ＳＯ₂−を、Ｂはアリルアミン塩単位、アクリルアミド単位またはメタクリルアミド単位を表し、Ｘ^-はハロゲンイオン、硫酸アニオン、スルホン酸アニオン、アルキルスルホン酸アニオン、酢酸アニオン、アルキルカルボン酸アニオンまたは燐酸アニオンを表す。ｍおよびｎは重合度を示す整数である。 The diallylamine-based polymer used in the present invention is a cationic polymer represented by the following general formula (1) or general formula (2), and each can be used alone or in combination.

In the formula, R ¹ and R ² represent a hydrogen atom or an alkyl group, and R ¹ and R ² may be the same or different. A represents —CH ₂ — or —CH ₂ —SO ₂ —, B represents an allylamine salt unit, an acrylamide unit or a methacrylamide unit, and X ⁻ represents a halogen ion, a sulfate anion, a sulfonate anion, or an alkyl sulfonate anion. Represents an acetate anion, an alkylcarboxylate anion, or a phosphate anion. m and n are integers indicating the degree of polymerization.

式中、Ｒ¹、Ｒ²、Ａ、Ｂ、ｍ、ｎおよびＸ^-は、前記一般式（１）および一般式（２）と同様である。 Moreover, the heterocyclic ring of the cationic polymer of the said General formula (1) and General formula (2) is obtained by radical-polymerizing divinyl monomers, such as dialkyl diallyl ammonium chloride, and carrying out cyclopolymerization within a molecule | numerator. In general, there are two types of such cycloadditions: 6-membered ring-forming addition (head-to-tail addition) and 5-membered ring-forming addition (head-to-head addition) ("chemistry of polymer synthesis" (Takayuki Otsu) In this invention, diallylamine-based polymers having such a 6-membered ring (piperidinium ring) may be used. Specifically, it is a cationic polymer represented by the following general formula (4) and general formula (5).

In the formula, R ¹ , R ² , A, B, m, n and X ⁻ are the same as those in the general formula (1) and the general formula (2).

  Specific examples of the diallylamine-based polymer used in the present invention include the following. Examples of the compounds represented by the general formulas (1) and (4) include polydiallylammonium chloride, polydimethyldiallylammonium chloride, diallylammonium chloride-sulfur dioxide copolymer, and dimethyldiallylammonium chloride-sulfur dioxide copolymer. Are represented by the above general formulas (2) and (5), for example, allylamine hydrochloride-diallylamine hydrochloride copolymer, acrylamide-diallylamine hydrochloride copolymer, acrylamide-dimethyldiallylamine hydrochloride copolymer. A polymer is mentioned, but it is not limited to these.

  The weight average molecular weight of the diallylamine-based polymer is not particularly limited, but is preferably in the range of 1,000 to 200,000, more preferably in the range of 1,000 to 100,000, still more preferably 2,000 to 50, A range of 000 is desirable. When the weight average molecular weight is low, bubbles are likely to be generated, which may cause coating defects. Also, a high weight average molecular weight is not preferable because the viscosity of the fine particle dispersion increases and the dispersibility deteriorates.

  The amount of diallylamine-based polymer used depends on the amount of hydroxy acid used in combination, but when used in a large amount, the viscosity of the fine particle dispersion and the coating liquid obtained by adding a binder to the dispersion increases, Since storage stability and coating suitability are lowered, it is preferable to add as little as possible. Therefore, the amount of diallylamine-based polymer used in the fine particle dispersion of the present invention is preferably 0.01 to 5% by mass, more preferably 0.01 to 3% by mass with respect to the inorganic fine particles.

  The water-soluble solvent in the fine particle dispersion of the present invention is not particularly limited as long as it is a mixed solution with water or an organic solvent that can be mixed with water. Examples of organic solvents that can be mixed with water include alcohols such as methanol, ethanol, and propanol: lower alkyl ethers of polyhydric alcohols such as ethylene glycol monomethyl ether and ethylene glycol dimethyl ether: ketones such as acetone and methyl ethyl ketone: tetrahydrofuran And ethers.

  The fine particle dispersion of the present invention can be obtained by dissolving a diallylamine-based polymer and a hydroxy acid in the water-soluble solvent and adding and dispersing the inorganic fine particles therein, but the method for preparing the dispersion is limited to this. For example, a method of simultaneously adding and dispersing diallylamine polymer, hydroxy acid and inorganic fine particles in a water-soluble solvent: dissolving diallylamine polymer in a water-soluble solvent and then adding inorganic fine particles And then adding the hydroxy acid after the dispersion: Dissolving the hydroxy acid in a water-soluble solvent, then adding and dispersing the inorganic fine particles, and then adding the diallylamine polymer: Dispersing the inorganic fine particles in the water-soluble solvent A method of dispersing and then adding a diallylamine polymer and a hydroxy acid can be selected. In addition, an appropriate amount of at least one of diallylamine-based polymer and hydroxy acid is added to a water-soluble solvent, and after dispersing inorganic fine particles therein, diallylamine-based polymer and hydroxy acid are further added to obtain a desired particle size and viscosity. It can also be controlled.

  As a means for dispersing the inorganic fine particles in a water-soluble solvent or a water-soluble solvent containing a diallylamine-based polymer or a hydroxy acid, either a continuous method or a batch method can be used. In addition, as the disperser, various conventionally known dispersers such as a high-pressure homogenizer, an ultrasonic homogenizer, a wet media type pulverizer (sand mill, ball mill), a continuous high-speed agitation disperser, and an ultrasonic disperser are used. be able to.

  The viscosity of the fine particle dispersion of the present invention is not particularly limited as long as the dispersion itself has good storage stability and does not impose a burden on handling in the subsequent process, and preferably 300 mPa · s or less. Preferably it is 100 mPa · s or less.

In preparing the fine particle dispersion of the present invention, it is ideal to cause a substantial turbulent flow in the dispersion in order to perform more uniform mixing. In general, the mechanical similarity of the flow around the fluid is defined by the stirring Reynolds number (Re),
Re = ρnd ² / μ
It is represented by a dimensionless number. Here, n is the rotation speed of the stirring blade, d is the diameter of the stirring blade, ρ is the density of the liquid, μ is the viscosity of the liquid, and is a laminar flow region when Re is low, and conversely when it is high Indicates. In the present invention, by using a dispersion solvent containing a diallylamine polymer and a hydroxy acid, even if the amount of hydroxy acid used is reduced, the dispersion itself has a low viscosity, and Re increases to cause turbulence. Since it tends to be easy, inorganic fine particles can be sufficiently dispersed and peptized without applying a strong stirring force.

  In the present invention, a recording medium can be obtained by forming an ink receiving layer on the support using the fine particle dispersion. Examples of the support used include, for example, appropriately sized paper, non-size paper, coated paper, cast-coated paper, and resin-coated paper (hereinafter, resin-coated paper) in which one or both sides of the paper are coated with a resin such as polyolefin. Transparent papers such as polyethylene, polypropylene, polyester, polylactic acid, polystyrene, polyacetate, polyvinyl chloride, cellulose acetate, polyethylene terephthalate, polymethyl methacrylate, and polycarbonate: Sheet-like substance (such as synthetic paper) made of a film made opaque by filling with an inorganic substance or fine foaming: a sheet made of glass or metal. In order to improve the adhesive strength between the support and the ink receiving layer, the support surface can be subjected to corona discharge treatment or various undercoat treatments.

  In the present invention, from the viewpoint of enhancing the glossiness of the ink receiving layer formed on the support, it is preferable to use a non-water-absorbing and highly smooth film and resin-coated paper, and at least the ink receiving layer is used. As the surface to be formed, a support having a 10-point average roughness according to JIS-B0601 of 0.5 μm or less and a 60-degree specular gloss according to JIS-Z-8741 of 25 to 75% can be more preferably used.

Although there is no restriction | limiting in particular in the thickness of a support body, the range of 25 micrometers-500 micrometers is preferable, More preferably, it is the range of 50 micrometers-300 micrometers. If the thickness of the support is less than 25 μm, the rigidity is low, and the touch, texture or opacity when it is held in hand is insufficient, causing inconvenience. On the other hand, when the thickness is larger than 500 μm, the obtained recording medium becomes rigid, which may hinder the paper feeding traveling of the printer. There is not any special restriction on the weight of the support is preferably within a range approximate ^{25g / m 2 ~500g / m 2} .

  In the production of the recording medium of the present invention, the coating liquid prepared for forming the ink receiving layer contains a binder such as a water-soluble resin and / or a water-dispersible resin together with the fine particle dispersion of the present invention. used. Examples of the water-soluble resin and / or water-dispersible resin used in the present invention include starch, gelatin, casein and modified products thereof, cellulose derivatives such as methylcellulose, carboxymethylcellulose, hydroxyethylcellulose, and completely or partially saponified polyvinyl. Alcohol or modified products thereof (cation modification, anion modification, silanol modification, etc.), urea resin, melamine resin, epoxy resin, epichlorohydrin resin, polyurethane resin, polyethyleneimine resin, polyamide resin, polyvinylpyrrolidone resin , Polyvinyl butyral resin, poly (meth) acrylic acid or copolymers thereof, acrylamide resin, maleic anhydride copolymer, polyester resin, SBR latex, NBR latex, methyl Acrylic polymer latex such as acrylate-butadiene copolymer latex and acrylate copolymer, vinyl polymer latex such as ethylene-vinyl acetate copolymer, and cationic groups or anions on these various polymer latexes And functional group-modified polymer latexes having a functional group. Preferably, it is polyvinyl alcohol obtained by hydrolyzing polyvinyl acetate, and an average degree of polymerization is 300-5,000. The saponification degree is preferably 70 to less than 100%, particularly preferably 80 to 99.5%. In addition, these water-soluble resins and / or water-dispersible resins can be used alone or in combination.

  The amount of the binder (B) used is preferably B / A = 1/30 to 1 and more preferably B / A = 1/20 to 1/3 as a mixing mass ratio with respect to the inorganic fine particles (A). . If the amount of the binder is within these ranges, the formed ink-receiving layer will not easily crack or fall off, and ink absorbency will be good. Further, the method for mixing the fine particle dispersion and the binder of the present invention is not particularly limited. However, it is preferable to dissolve the water-soluble resin and / or the water-dispersible resin in an aqueous medium in an amount as necessary. Is mixed with the fine particle dispersion, and can be mixed by either a batch method or a continuous method.

  The aqueous medium is not particularly limited as long as it is a mixed solution with water or an organic solvent that can be mixed with water. Examples of the organic solvent that can be mixed with water include alcohols such as methanol, ethanol, and propanol: ethylene Lower alkyl ethers of polyhydric alcohols such as glycol monomethyl ether and ethylene glycol dimethyl ether: Ketones such as acetone and methyl ethyl ketone: Ethers such as tetrahydrofuran.

  In addition, in the recording medium of the present invention, in order to improve the film forming property, water resistance and film strength of the inorganic fine particle dispersion and the film formed of the water-soluble resin and / or the water-dispersible resin, the ink receiving layer A hardener may be added inside. Generally, various hardeners are selected depending on the type of reactive group possessed by the polymer used. For example, in the case of a polyvinyl alcohol resin, an epoxy hardener, boric acid or a water-soluble aluminum salt, etc. Examples of the hardener used in the present invention include boron compounds such as oxygen acids centered on boron atoms or salts thereof, such as orthoboric acid, metaboric acid, Hypoboric acid, tetraboric acid, pentaboric acid and salts thereof can be preferably used.

  The amount of the boron compound used varies depending on the amount of the water-soluble resin and / or water-dispersible resin used as the binder, but is generally 0.1 to 30% by mass relative to the water-soluble resin and / or water-dispersible resin. Should be added. If the content of the boron compound is less than 0.1% by mass with respect to the water-soluble resin and / or water-dispersible resin, the film-forming property is lowered and sufficient water resistance cannot be obtained. On the contrary, when it exceeds 30% by mass, for example, when coating is performed by a batch method described later, a change with time in the viscosity of the coating solution becomes large, and the coating stability may be lowered.

  As for the method of adding a crosslinking agent to the ink receiving layer, a method in which a crosslinking agent is directly added to a coating liquid containing a fine particle dispersion and a binder and coating is performed in a batch mode, and a crosslinking agent is previously added to the fine particle dispersion. A method of coating while mixing with a binder immediately before coating, a method in which a crosslinking agent is dissolved in another aqueous medium and added in-line to a coating liquid containing a fine particle dispersion and a binder immediately before coating, Furthermore, there is a method of applying a solution containing a crosslinking agent before and after the application of the coating solution containing the fine particle dispersion and the binder, and any method can be used.

  The solid content concentration in the coating liquid for forming the ink receiving layer is not particularly limited as long as the viscosity is such that the ink receiving layer can be formed on the support. 50 mass% is preferable. When the solid content concentration is less than 5% by mass, it is necessary to increase the coating amount in order to increase the thickness of the ink receiving layer, which requires a lot of time and energy for drying, which is uneconomical. There is a case. On the other hand, if it exceeds 50% by mass, the viscosity of the coating solution may increase and the coating property may deteriorate.

  Moreover, various additives can be mix | blended with the said coating liquid in the range which does not prevent the effect of this invention. Such additives include antifoaming agents, ink fixing agents, dot adjusting agents, colorants, fluorescent brighteners, preservatives, pH adjusting agents, penetrating agents, antistatic agents, conductive agents, ultraviolet absorbers, oxidation agents Examples thereof include an inhibitor (anti-fading agent).

  As a method of applying the prepared coating liquid on the support, spin coating method, roll coating method, blade coating method, air knife coating method, gate roll coating method, bar coating method, size press method, spray coating method, Conventionally known coating methods such as a gravure coating method, a curtain coating method, a rod blade coating method, a lip coating method, and a slit die coating method can be used. Thereafter, the ink receiving layer can be formed by drying using a drying apparatus such as a hot air dryer, a thermal drum, or a far infrared dryer. The ink receiving layer in the recording medium of the present invention may be formed in multiple layers by changing the composition ratio of the inorganic fine particle dispersion, the binder and other additives, and may be formed on one side or both sides of the support. Is possible. If necessary, it is also possible to improve the smoothness of the surface of the ink receiving layer using a calender roll after coating.

A preferable range for the coating amount of the coating liquid on the support is 0.5 to 60 g / m ² in terms of solid content, and a more preferable range is 5 to 55 g / m ² . When the coating amount is less than 0.5 g / m ² , the formed ink receiving layer may not sufficiently absorb the moisture of the ink, and the ink may flow or the image may bleed. 60 g / m ² If it exceeds 1, curling may occur at the time of drying, or a remarkable effect may not appear as expected for printing performance.

  Since the recording medium of the present invention thus obtained has a low acid concentration in the ink receiving layer, it is possible to effectively suppress a decrease in ink absorbency and beading. Further, even if the hydroxy acid remains in the ink receiving layer, it is unlikely to cause an unpleasant odor.

  In order to suppress the concentration of the acid remaining in the ink receiving layer, the set temperature is increased in the drying step, or when the heat resistant temperature of the support is low, it can be controlled by the drying time. In the case of continuous drying after coating, it is more advantageous to produce a recording medium using the fine particle dispersion of the present invention, particularly when the space for placing the dryer is limited and drying cannot be performed sufficiently. is there.

  The ink used for recording an image on the recording medium of the present invention is not particularly limited, but a mixture of water and a water-soluble organic solvent is used as a medium, and a dye or pigment is dissolved or dispersed as a coloring material. The common water-based ink for ink jet recording can be preferably used.

  As a method for forming an image by applying the ink to the recording medium, an ink jet recording method is particularly preferable. As the ink jet recording method, the ink is effectively separated from the nozzle and the ink is applied to the recording medium. Any method may be used as long as it can provide the above. In particular, an ink jet system in which ink subjected to the action of thermal energy undergoes a rapid volume change by a method described in Japanese Patent Application Laid-Open No. 54-59936 and the like, and ink is ejected from a nozzle by the action force due to this state change. Can be used effectively.

  Hereinafter, the present invention will be specifically described by way of examples. In the following examples, “part” and “%” are based on mass unless otherwise specified.

<Production of alumina hydrate>
Aluminum dodexide was produced by the method described in US Pat. No. 4,242,271. Next, the aluminum alkoxide was hydrolyzed by the method described in US Pat. No. 4,202,870 to produce an alumina slurry. Water was added to the alumina slurry until the solid content of alumina hydrate was 7.7%, and the mixture was aged in an autoclave at an aging temperature of 150 ° C. and an aging time of 6 hours to obtain a colloidal sol. This colloidal sol was spray-dried at an inlet temperature of 87 ° C. to obtain an alumina hydrate powder. The obtained powder had a flat plate shape and was measured by X-ray diffraction to measure alumina water having a boehmite crystal structure. Showed Japanese. Further, the BET specific surface area of the obtained powder was measured using a specific surface area / pore distribution measuring apparatus (Micromeritics ASAP2400, manufactured by Shimadzu Corporation), and it was 140.5 m ² / g. .

<Example 1>
Charol DC-902P (trade name, 51% aqueous solution, weight average molecular weight: about 9,000, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) as diallylamine-based polymer in 100 parts of ion-exchanged water (alumina water) 0.18% for Japanese product) and 0.38 part of glycolic acid (1.5% for alumina hydrate) were added. Three-one motor (BL600, rated torque: 5 kgf · cm, stirring blade: The dispersion solvent was prepared by stirring for 10 minutes at 150 rpm using a turbine type, manufactured by Shinto Kagaku Co., Ltd.). Thereafter, 25.1 parts of the alumina hydrate was added while adjusting the temperature of the dispersion solvent to 25 ° C. in a low-temperature constant temperature water bath, and the number of revolutions of the three-one motor was adjusted to 350 rpm and stirred for 10 minutes. As a result, a fine particle dispersion of the present invention having a solid content concentration of alumina hydrate of 20% with respect to the total dispersion was obtained. Tests of the following evaluations 1 to 3 were performed on the fine particle dispersions thus obtained. The results are shown in Table 1.

Next, 10.0 parts of a 3% boric acid aqueous solution (15% with respect to polyvinyl alcohol) was mixed with 100 parts of the fine particle dispersion prepared above, and polyvinyl alcohol (PVA-224) was added to 45 parts of ion-exchanged water. 20.0 parts (10% with respect to alumina hydrate) obtained by dissolving 5 parts of Kuraray Co., Ltd. were added to prepare a coating solution. Furthermore, polyethylene-coated paper (thickness: 224 μm, basis weight: 234 g / m ² , 60 ° specular gloss according to JIS-Z-8741: 64%, Oji Paper Co., Ltd., custom-made product) is used as a support. On top of that, the previously prepared coating solution was applied with a Mayer bar so that the dry coating amount was 35 g / m ^2, and 110 ° C. with a blast constant temperature dryer (manufactured by Toyo Manufacturing Co., Ltd., FC-610). The recording medium of the present invention was produced by drying for 20 minutes. The obtained recording medium was subjected to the following evaluation 4. The results are shown in Table 1.

Various properties of the obtained fine particle dispersion and the recording medium were evaluated in the following manner.
<Evaluation 1: Viscosity of fine particle dispersion>
The fine particle dispersion was allowed to stand for 15 minutes in a low-temperature constant temperature water bath set at 25 ° C., and then the viscosity was measured using a B-type viscometer (BM type, manufactured by Tokyo Keiki Co., Ltd.).
<Evaluation 2: Reynolds number at the time of preparing the fine particle dispersion>
The specific gravity of the fine particle dispersion was measured using a hydrometer (manufactured by Nippon Keiki Kogyo Co., Ltd.), the viscosity measured in Evaluation 1 and the stirring conditions at the time of preparing the dispersion (stirring blade diameter: 86 mm, rotation speed: 350 rpm), the stirring Reynolds number Re was calculated.
<Evaluation 3: Particle size of inorganic fine particles>
Using a laser particle size analyzer PARIII (manufactured by Otsuka Electronics Co., Ltd.), the average particle size of alumina hydrate in the fine particle dispersion was measured.
<Evaluation 4: Beading>
Using an inkjet printer (BJ F900, manufactured by Canon Inc.), solid printing of green (mixed color of yellow 100% and cyan 100%, ink ejection amount: 200%) is performed, and beading (cannot absorb ink) The degree of occurrence of granular density irregularity) was visually evaluated. “◯” indicates that the ink absorbs well, “Δ” indicates that the beading slightly occurs, and “x” indicates that the degree of beading is large.

<Example 2>
In Example 1, the amount of diallylamine-based polymer was 0.492 parts (1% based on alumina hydrate), the amount of glycolic acid was 0.50 parts (2% based on alumina hydrate), A fine particle dispersion and a recording medium of the present invention were prepared in the same manner as in Example 1 except that the amount of ion-exchanged water was adjusted so that the solid content concentration of alumina hydrate with respect to the total dispersion was 20%. The tests of evaluations 1 to 4 were performed. The results are shown in Table 1.

<Example 3>
In Example 1, 0.061 part of diallylamine-based polymer (Charol DC-303P (trade name, 41.4% aqueous solution, weight average molecular weight: about 30,000, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.)) Example 1 except that the amount of ion-exchanged water was adjusted so that the solid content concentration of alumina hydrate with respect to the total dispersion was 20%. Then, a fine particle dispersion and a recording medium of the present invention were prepared, and tests 1 to 4 were performed. The results are shown in Table 1.

<Example 4>
In Example 1, 0.37 part of diallylamine polymer (trade name, 20% aqueous solution, weight average molecular weight: about 5,000, manufactured by Nitto Boseki Co., Ltd.) 0.377 parts (based on alumina hydrate) 0.3%) and the fine particles of the present invention were the same as in Example 1 except that the amount of ion-exchanged water was adjusted so that the solid content concentration of alumina hydrate with respect to the total dispersion was 20%. A dispersion and a recording medium were prepared, and tests 1 to 4 were performed. The results are shown in Table 1.

<Example 5>
In Example 1, 0.063 part of diallylamine polymer was added to PAA-D41-HCl (trade name, 40% aqueous solution, weight average molecular weight: about 20,000, manufactured by Nitto Boseki Co., Ltd.) The present invention was changed in the same manner as in Example 1 except that the amount of ion-exchanged water was adjusted so that the solid content concentration of alumina hydrate with respect to the total dispersion was 20%. A fine particle dispersion and a recording medium were prepared, and tests 1 to 4 were performed. The results are shown in Table 1.

<Example 6>
In Example 1, 0.08 part of diallylamine polymer PAS-A-120L (trade name, 30% aqueous solution, weight average molecular weight: about 100,000, manufactured by Nitto Boseki Co., Ltd.) The present invention was changed in the same manner as in Example 1 except that the amount of ion-exchanged water was adjusted so that the solid content concentration of alumina hydrate with respect to the total dispersion was 20%. A fine particle dispersion and a recording medium were prepared, and tests 1 to 4 were performed. The results are shown in Table 1.

<Example 7>
In Example 1, the amount of diallylamine polymer was 0.148 parts (0.3% based on alumina hydrate), and glycolic acid was 0.71 parts (concentration: 88.5%, alumina water). The amount of ion-exchanged water was adjusted so that the solid content concentration of alumina hydrate with respect to the total dispersion was 20%. Then, a fine particle dispersion and a recording medium of the present invention were prepared, and tests 1 to 4 were performed. The results are shown in Table 1.

<Example 8>
In Example 4, glycolic acid was changed to 0.71 part of lactic acid (concentration: 88.5%, 2.5% with respect to alumina hydrate), and the solid content concentration of alumina hydrate with respect to the total dispersion was Except that the amount of ion-exchanged water was adjusted to 20%, the fine particle dispersion and the recording medium of the present invention were prepared in the same manner as in Example 4, and the tests of Evaluations 1 to 4 were performed. The results are shown in Table 1.

<Example 9>
In Example 1, the amount of diallylamine-based polymer was 0.148 parts (0.3% with respect to alumina hydrate), and glycolic acid was 0.51 parts of 2-hydroxyisobutyric acid (concentration: 99%, Example 2 except that the amount of ion-exchanged water was adjusted so that the solid content concentration of alumina hydrate with respect to the total dispersion was 20%. Then, a fine particle dispersion and a recording medium of the present invention were prepared, and tests 1 to 4 were performed. The results are shown in Table 1.

<Example 10>
In Example 4, glycolic acid was changed to 0.51 part of 2-hydroxyisobutyric acid (concentration: 99%, 2% with respect to alumina hydrate), and the solid content concentration of alumina hydrate with respect to the total dispersion was Except that the amount of ion-exchanged water was adjusted to 20%, the fine particle dispersion and the recording medium of the present invention were prepared in the same manner as in Example 4, and the tests of Evaluations 1 to 4 were performed. The results are shown in Table 1.

<Comparative Examples 1-3>
In Example 1, no diallylamine-based polymer was used, and the amount of glycolic acid alone was 0.38 parts, 0.50 parts, 0.75 parts (1.5%, 2%, 3% based on alumina hydrate). In the same manner as in Example 1, except that the amount of ion-exchanged water was adjusted so that the solid content concentration of alumina hydrate with respect to the total dispersion was 20%, the fine particle dispersion and the recording medium of Comparative Example The test of evaluation 1-4 was performed. The results are shown in Table 1. However, the fine particle dispersion with 1.5% and 2% glycolic acid added to the alumina hydrate has a high viscosity. When the coating liquid is prepared by adding boric acid and polyvinyl alcohol to this dispersion, it is stirred uniformly. Since it was judged that this was not possible, the test of evaluation 4 was not carried out for Comparative Examples 1 and 2.

<Comparative Examples 4 and 5>
In Example 7, diallylamine-based polymer was not used, and the amount of lactic acid was 0.71 part and 0.99 part (2.5% and 3.5% with respect to alumina hydrate), and the total dispersion was used. Except that the amount of ion-exchanged water was adjusted so that the solid content concentration of alumina hydrate was 20%, a fine particle dispersion and a recording medium of Comparative Example were prepared in the same manner as in Example 7, and evaluations 1 to 4 tests were performed. The results are shown in Table 1. However, because the fine particle dispersion with 2.5% lactic acid added to the alumina hydrate has high viscosity, it was judged that uniform stirring was not possible when boric acid and polyvinyl alcohol were added thereto to prepare a coating solution. In Comparative Example 4, the test of Evaluation 4 was not performed.

<Comparative Examples 6 and 7>
In Example 9, diallylamine-based polymer was not used, and the amount of 2-hydroxyisobutyric acid was 0.51 part and 0.76 part (2% and 3% with respect to alumina hydrate), and the total dispersion was used. Except that the amount of ion-exchanged water was adjusted so that the solid content concentration of alumina hydrate was 20%, a fine particle dispersion and a recording medium of Comparative Example were prepared in the same manner as in Example 9, and evaluations 1 to 4 tests were performed. The results are shown in Table 1. However, a fine particle dispersion in which 2% of 2-hydroxyisobutyric acid is added to alumina hydrate has a high viscosity, and when boric acid and polyvinyl alcohol are added thereto to prepare a coating liquid, it cannot be uniformly stirred. Therefore, in Comparative Example 6, the test of Evaluation 4 was not performed.

<Comparative Example 8>
Comparative Example as in Example 1, except that glycolic acid was not used and the amount of ion-exchanged water was adjusted so that the solid content concentration of alumina hydrate with respect to the total dispersion was 20%. A fine particle dispersion was prepared, and tests 1 to 3 were performed. However, there were many aggregates, and the test of evaluation 3 could not be performed.

<Comparative Example 9>
In Example 2, glycolic acid was not used, and the amount of ion-exchanged water was adjusted so that the solid content concentration of alumina hydrate with respect to the total dispersion was 20%. A fine particle dispersion was prepared. However, since the dispersion started to separate into two layers about 10 minutes after preparation, the tests of Evaluations 1 and 2 were not performed. Moreover, there were many aggregates and the test of evaluation 3 was not able to be implemented.

<Comparative Example 10>
Comparative Example as in Example 4 except that glycolic acid was not used and the amount of ion-exchanged water was adjusted so that the solid content concentration of alumina hydrate with respect to the total dispersion was 20%. A fine particle dispersion was prepared, and tests 1 to 3 were performed. However, there were many aggregates, and the test of evaluation 3 could not be performed.

<Comparative Example 11>
Comparative Example as in Example 5, except that glycolic acid was not used and the amount of ion-exchanged water was adjusted so that the solid content concentration of alumina hydrate with respect to the total dispersion was 20%. A fine particle dispersion was prepared, and tests 1 to 3 were performed. However, there were many aggregates, and the test of evaluation 3 could not be performed.

<Comparative Example 12>
In Example 1, no diallylamine-based polymer was used, and the glycolic acid was changed to 12.55 parts of a 6% -acetic acid aqueous solution (3.0% with respect to the alumina hydrate). Except that the amount of ion-exchanged water was adjusted so that the solid content concentration of the hydrate was 20%, a fine particle dispersion and a recording medium of Comparative Example were prepared in the same manner as in Example 1, and evaluations 1 to 4 were made. Was tested. The results are shown in Table 1.

  As is clear from Table 1, the fine particle dispersion of the present invention prepared using diallylamine polymer and hydroxy acid had a lower viscosity than the dispersion prepared using the same amount of hydroxy acid (Example 1). 3, 4, 5, 6 and Comparative Example 1 comparison, Example 2 and Comparative Example 2 comparison, Examples 7 and 8 and Comparative Example 4 comparison, Examples 9, 10 and Comparative Example 6 comparison) . In addition, the fine particle dispersion of the present invention has a higher stirring Reynolds number than the fine particle dispersion prepared using the same amount of hydroxy acid, and tends to cause turbulence. Furthermore, it can be seen that the fine particle dispersion of the present invention has a smaller average particle size than the dispersion prepared using the same amount of hydroxy acid, and the inorganic fine particles are efficiently peptized. In addition, the fine particle dispersions (Comparative Examples 8 to 11) prepared only with the diallylamine-based polymer had many aggregates and could not be peptized under the same stirring conditions.

  Further, the recording medium of the present invention in which the ink receiving layer was formed using the fine particle dispersion of the present invention showed good ink absorbability and a high quality image without beading was obtained. In addition, the recording medium (Comparative Example 12) in which the ink receiving layer was formed with a fine particle dispersion prepared using acetic acid generated an acetic acid odor when an image was recorded. However, the recording medium of the present invention was particularly uncomfortable. No odor was produced.

  When preparing a fine particle dispersion, it is possible to provide a fine particle dispersion in which the particle diameter and viscosity are controlled within a desired range under relatively gentle stirring conditions by using a diallylamine polymer and a hydroxy acid. did it. In addition, by forming an ink receiving layer using the dispersion liquid, an unpleasant odor generated when an image is recorded can be suppressed, and a recording medium capable of forming a high-quality image can be provided.

Claims (6)

  A fine particle dispersion in which inorganic fine particles are dispersed in an aqueous solvent, wherein the dispersion contains a diallylamine polymer and a hydroxy acid.   The fine particle dispersion according to claim 1, wherein the inorganic fine particles are alumina and / or alumina hydrate. The fine particle dispersion according to claim 1, wherein the diallylamine-based polymer is at least one cationic polymer selected from the following general formula (1) or general formula (2).

(Wherein R ¹ and R ² represent a hydrogen atom or an alkyl group, R ¹ and R ² may be the same or different. A represents —CH ₂ — or —CH ₂ —SO ₂ —, B represents an allylamine salt unit, an acrylamide unit or a methacrylamide unit, and X ⁻ represents a halogen ion, a sulfate anion, a sulfonate anion, an alkyl sulfonate anion, an acetate anion, an alkyl carboxylate anion, or a phosphate anion. (It is an integer indicating the degree of polymerization.)   The fine particle dispersion according to claim 1, wherein the hydroxy acid is a monocarboxylic acid.   In a recording medium having an ink receiving layer provided on at least one surface of a support, the ink receiving layer is formed using a fine particle dispersion containing a diallylamine-based polymer and a hydroxy acid. Recording medium.   The recording medium according to claim 5, wherein the fine particle dispersion is the fine particle dispersion according to claim 1.