JP2006103122A - Inkjet recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording medium which makes the viscosity of a coating liquid lower in manufacture, which has cracking resistance improved, and which can obtain a high-quality image excellent in image uniformity. <P>SOLUTION: In this void type inkjet recording medium where an ink absorbing layer containing at least a hydrophilic resin and inorganic particulates with a mean particle diameter of 100 nm or less is provided on a non-water-absorbing substrate, the ink absorbing layer contains a copolymer with an average molecular weight of 500-1,000, which is composed of an ethylene oxide chain and an alkylene oxide chain. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an ink jet recording medium having a low coating solution viscosity at the time of production, improved crack resistance, and a high quality image.

  In recent years, the image quality of inkjet recording has been rapidly improved, and is approaching that of photographic quality. As a means for achieving such photographic image quality by ink jet recording, rapid improvement of technology has also been attempted in the ink jet recording medium to be used, and a layer having a minute void structure (hereinafter referred to as void) on a highly smooth support. An ink jet recording medium provided with a layer, also referred to as an ink absorbing layer or a porous layer) is becoming one of the closest to photographic image quality because of its excellent ink absorbability and drying property.

  Such a porous layer is mainly formed of a hydrophilic resin and fine particles. For example, silica fine particles synthesized by a gas phase method or an ink jet recording medium obtained by a combination of colloidal silica and a hydrophilic resin are known. ing.

  If a non-water-absorbing support is used as the support for holding the ink receiving layer, there is no cockling (wrinkle) after printing as seen in the water-absorbing support, and a highly smooth surface can be maintained. High-quality printed matter can be obtained. However, since the non-water-absorbing support does not have the ability to absorb water-based ink, when the non-water-absorbing support is used as a support for an inkjet recording medium, the ink receiving layer does not have a sufficient ink absorption capacity. A mottled printing unevenness due to poor ink absorbency occurs in a solid portion with a large amount of driving, and the print image quality is degraded.

  In contrast to the above problem, for example, this unevenness can be prevented by increasing the film thickness of the ink receiving layer. However, when the ink receiving layer is dried, cracks occur when the ink receiving layer is dried. I will have it. Furthermore, in an inkjet recording medium using a non-water-absorbing support, gloss cannot be added by pressing as in cast-coated paper, so that inorganic fine particles having a small average particle diameter must be used for the ink receiving layer. That also causes the cracks to deteriorate.

  In addition, cracks can be improved by increasing the proportion of the hydrophilic resin component, but in this case, the ink absorbability is deteriorated, and mottled printing unevenness is likely to occur.

  Thus, the improvement of cracks and the improvement of mottled printing unevenness are often in a trade-off relationship, and it is difficult and important to improve both at the same time.

On the other hand, an ink jet recording medium using a compound having an ethylene oxide chain or an alkylene oxide chain has been proposed from the viewpoint of improving the coating film performance, ink absorbability and glossiness of the ink receiving layer. For example, a pigment having an average particle size of 3 μm or less, a water-soluble binder, and a nonionic surfactant having an HLB value in the range of 7 to 9 are blended at a ratio of 0.05 to 0.5% by mass with respect to the pigment. An inkjet recording material in which the nonionic surfactant is a polymer containing an ethylene oxide unit (C ₂ H ₄ O) has been disclosed, and has excellent ink absorbability for high-speed printing and an inkjet system with a high discharge amount. In addition, it is said that a high-quality inkjet recording material having a printing surface with a uniform coating layer so as to prevent printing unevenness as well as color development and resolution can be obtained (for example, Patent Document 1). reference.). In addition, in the ink jet recording medium, a description using a polyethylene oxide-polypropylene oxide copolymer or the like is seen as a water-soluble resin, but no suggestion or proposal regarding molecular weight or the like is recognized (for example, see Patent Document 2). .

  However, in the above proposed or disclosed method, the average molecular weight of the disclosed compound having an ethylene oxide chain or an alkylene oxide chain is 1000 or more, or is not disclosed at all. In the copolymer consisting of ethylene oxide chain and alkylene oxide chain having a molecular weight of more than 1000, the effect of improving the image quality is recognized to some extent, but in the coating liquid containing them, there are problems such as excessive viscosity increase. appear. If such an increase in the viscosity of the coating liquid occurs, it causes problems such as liquid feeding properties in the coating liquid preparation process or the coating process, and if the viscosity rises significantly, it may cause a repellency failure or the like during coating. A uniform coating film cannot be obtained. In addition, for the increase in viscosity of the coating solution, it is possible to reduce the viscosity of the coating solution by diluting with water, but in this case, the load in the drying process (drying capacity, drying time) increases, This results in a decrease in productivity.

In addition, in an ink jet recording sheet in which at least one ink receiving layer and a gloss developing layer formed by casting are laminated on one side of a support, both oxyethylene units and oxypropylene units are contained in one molecule. An ink jet recording sheet containing a polyether-based compound is disclosed, and an ink jet recording sheet having both high glossiness, high ink absorption and printing density, and excellent coating layer strength can be realized. (For example, refer to Patent Document 3). In Patent Document 3, there is a description that a compound having a molecular weight of 500 to 1000 is preferable as a polyether compound containing both oxyethylene units and oxypropylene units in one molecule. There is no description or suggestion regarding the effect of an inkjet recording medium using a non-water-absorbing support, which is a support.
JP-A-9-99631 JP 2000-326625 A JP 2003-276212 A

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an ink jet recording medium having a low coating solution viscosity during production, improved crack resistance, and a high image with excellent image uniformity. There is.

  The above object of the present invention is achieved by the following configurations.

(Claim 1)
In a void-type inkjet recording medium having an ink receiving layer containing inorganic fine particles having an average particle size of 100 nm or less and a hydrophilic resin on a non-water-absorbing support, the ink receiving layer comprises an ethylene oxide chain and an alkylene. An inkjet recording medium comprising a copolymer having an average molecular weight of 500 to 1000 composed of an oxide chain.

(Claim 2)
2. The ink jet recording medium according to claim 1, wherein an ethylene oxide chain ratio in the copolymer is 40% by mass or less.

(Claim 3)
2. The ink jet recording medium according to claim 1, wherein an ethylene oxide chain ratio in the copolymer is 5 to 30% by mass.

(Claim 4)
The inkjet copolymer according to any one of claims 1 to 3, wherein the copolymer is a compound represented by the following general formula (1) or (2).

General formula (1)
_{HO (CH 2 CH 2 O)} n (CH 2 CH (CH 3) O) m (CH 2 CH 2 O) k H
General formula (2)
_{HO (CH 2 CH (CH 3} ) O) p (CH 2 CH 2 O) q (CH 2 CH (CH 3) O) r H
[In the formula, n, k, and q each represent a real number of 1 or more and less than 23, and m, p, or r represents a real number of 1 or more and less than 18, respectively. However, 500 ≦ 44 × (n + k) + 58 × m + 18 ≦ 1000 and 500 ≦ 44 × q + 58 × (p + r) + 18 ≦ 1000. ]
(Claim 5)
5. The inkjet recording medium according to claim 1, wherein the content of the copolymer is 0.5 to 10% by mass of the total mass of the inorganic fine particles.

(Claim 6)
The ink jet recording medium according to claim 1, wherein the inorganic fine particles are vapor phase method silica.

  According to the present invention, it is possible to provide an ink jet recording medium having a low coating solution viscosity during production, improved crack resistance, and a high image with excellent image uniformity.

  Hereinafter, the best mode for carrying out the present invention will be described in detail.

  As a result of intensive studies in view of the above problems, the present inventor has found that a void-type ink receiving layer containing an inorganic fine particle having an average particle diameter of 100 nm or less and a hydrophilic resin on a non-water-absorbing support. In the ink jet recording medium, the ink receiving layer contains a copolymer having an average molecular weight of 500 to 1000 composed of an ethylene oxide chain and an alkylene oxide chain. It is possible to obtain an appropriate viscosity of the coating liquid without excessively increasing the viscosity of the coating liquid containing the ink-receiving layer. As a result, a uniform ink-receiving layer coating film can be formed, there is no crack, and it is mottled. As a result, it has been found that a high-quality inkjet recording image having excellent image uniformity with no printing unevenness can be realized, and the present invention has been achieved.

  With regard to the factors that can provide a high-quality inkjet recording image without mottled printing unevenness by adopting the configuration defined in the present invention, the detailed mechanism is not completely clarified at present, but ethylene oxide It is presumed that the copolymer according to the present invention comprising a chain and an alkylene oxide chain increases the wettability between the surface of the inorganic fine particles and the ink, and as a result, the ink absorbency is increased.

  Details of the present invention will be described below.

  The ink jet recording medium of the present invention (hereinafter also simply referred to as a recording medium) has a void-type ink receiving layer containing inorganic fine particles having an average particle size of 100 nm or less and a hydrophilic resin, and the ink receiving layer comprises: It contains a copolymer having an average molecular weight of 500 to 1000 composed of an ethylene oxide chain and an alkylene oxide chain.

  First, the copolymer having an average molecular weight of 500 to 1000 composed of an ethylene oxide chain and an alkylene oxide chain according to the present invention will be described.

  The copolymer composed of the ethylene oxide chain and the alkylene oxide chain according to the present invention is characterized in that the average molecular weight is 500 to 1,000. If the average molecular weight is 1000 or less, the formed ink-receiving layer is excellent in crack resistance, and in addition, the viscosity of the ink-receiving layer coating solution can be adjusted to an appropriate range. If the average molecular weight is 500 or more, crack resistance is good, and a sufficient image quality improving effect can be exhibited without causing an increase in the viscosity of the ink receiving layer coating solution.

  In the copolymer having an average molecular weight of 500 to 1000 consisting of an ethylene oxide chain and an alkylene oxide chain according to the present invention, the alkylene oxide chain is a propylene oxide chain in view of simplicity in production and high solubility in water. In particular, a compound represented by the following general formula (1) or (2) is preferable.

General formula (1)
_{HO (CH 2 CH 2 O)} n (CH 2 CH (CH 3) O) m (CH 2 CH 2 O) k H
General formula (2)
_{HO (CH 2 CH (CH 3} ) O) p (CH 2 CH 2 O) q (CH 2 CH (CH 3) O) r H
In the general formulas (1) and (2), n, k, and q each represent a real number of 1 or more and less than 23, and m, p, or r represents a real number of 1 or more and less than 18, respectively. However, from the viewpoint that the average molecular weight is 500 to 1000, 500 ≦ 44 × (n + k) + 58 × m + 18 ≦ 1000 and 500 ≦ 44 × q + 58 × (p + r) + 18 ≦ 1000.

  Further, in the copolymer having an average molecular weight of 500 to 1000 consisting of an ethylene oxide chain and an alkylene oxide chain according to the present invention, the ratio of ethylene oxide in the copolymer is 40% by mass or less of the total mass of the copolymer. It is preferable from the viewpoint of image quality improvement which is the object effect of the present invention, and particularly preferably 5 to 30% by mass.

  Further, the content of the copolymer having an average molecular weight of 500 to 1000 consisting of an ethylene oxide chain and an alkylene oxide chain according to the present invention is preferably 0.5 to 10% by mass with respect to the total mass of the inorganic fine particles. . If the content is 0.5% by mass or more, the objective effect of the present invention can be sufficiently exerted, and if the content is 10% by mass or less, mottled printing unevenness can be suppressed.

  A copolymer having an average molecular weight of 500 to 1000 consisting of an ethylene oxide chain and an alkylene oxide chain according to the present invention can be obtained according to a synthesis method known in the art. For example, it is represented by the general formula (1). The copolymer can be synthesized by addition polymerization of polypropylene oxide with polypropylene under alkaline conditions. The copolymer represented by the general formula (2) can be synthesized by addition polymerization of propylene glycol to polyethylene glycol under alkaline conditions. The average molecular weight and the ratio of ethylene oxide in the molecule can be adjusted to desired conditions by the molecular weight of polypropylene glycol or polyethylene glycol and the added mass of ethylene oxide or propylene oxide.

  The copolymer consisting of an ethylene oxide chain and an alkylene oxide chain according to the present invention is characterized in that the average molecular weight is 500 to 1000, but the average molecular weight referred to in the present invention means a number average molecular weight, The molecular weight distribution can be measured by, for example, an ultracentrifugation rate method, an equilibrium method, thin layer chromatography, or gel permeation chromatography. In particular, gel permeation chromatography is preferable from the viewpoint of obtaining a highly reproducible chromatogram by a simple mechanical operation.

  Next, the inorganic fine particles according to the present invention will be described.

  Examples of inorganic fine particles that can be used in the present invention include light calcium carbonate, heavy calcium carbonate, magnesium carbonate, kaolin, clay, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc hydroxide, and zinc sulfide. , Zinc carbonate, hydrotalcite, aluminum silicate, diatomaceous earth, calcium silicate, magnesium silicate, synthetic amorphous silica, colloidal silica, alumina, colloidal alumina, pseudoboehmite, aluminum hydroxide, lithopone, zeolite, magnesium hydroxide, etc. Mention may be made of white inorganic pigments. The inorganic fine particles can be used as primary particles or in a state where secondary agglomerated particles are formed.

  In the present invention, from the viewpoint of obtaining a high-quality print with an inkjet recording medium, silica-based particles or alumina is used from the viewpoint that inorganic fine particles having a low refractive index and an average particle size of 100 nm or less can be obtained relatively inexpensively. Diameter particles are preferable, and alumina, pseudoboehmite, colloidal silica, fine particle silica synthesized by a gas phase method, and the like are preferable. Particularly, fine particle silica synthesized by a gas phase method with an average particle size of 100 nm or less is particularly preferable. .

  The silica synthesized by this vapor phase method may have a surface modified with aluminum. The aluminum content of vapor-phase process silica whose surface is modified with aluminum is preferably 0.05 to 5% by mass with respect to silica.

  One of the characteristics is that the average particle size of the inorganic fine particles is 100 nm or less from the viewpoint of glossiness and color density, but the average particle size of the inorganic fine particles is 50 nm or less from the viewpoint of gloss and print density. Preferably used. Although the minimum of a particle size is not specifically limited, 3 nm or more is preferable from a viewpoint on manufacture of inorganic fine particles.

  The average particle size of the inorganic fine particles is obtained as a simple average value (number average) by observing the cross section and surface of the ink receiving layer with an electron microscope and determining the particle size of 100 arbitrary particles. Here, each particle size is expressed by a diameter assuming a circle equal to the projected area.

  The inorganic fine particles may remain as primary particles or may be present in the porous film as secondary particles or higher-order aggregated particles, but the average particle diameter is determined by an ink receiving layer when observed with an electron microscope. Among them, the particle size of the particles forming independent particles.

The content of the inorganic fine particles in the water-soluble coating solution is 5 to 40% by mass, and particularly preferably 7 to 30% by mass. The inorganic fine particles need to form an ink receiving layer having sufficient ink absorbability and less cracking of the film, and the amount of 5 to 50 g / m ² is preferable in the ink receiving layer. . Furthermore, it is especially preferable that it is 10-30 g / m < ² >.

  Next, the hydrophilic resin constituting the ink receiving layer according to the present invention will be described.

  The hydrophilic resin contained in the ink receiving layer is not particularly limited, and conventionally known hydrophilic resins can be used. For example, gelatin, polyvinyl pyrrolidone, polyethylene oxide, polyacrylamide, polyvinyl alcohol, and the like can be used. However, polyvinyl alcohol is particularly preferable from the viewpoint of relatively small moisture absorption characteristics of the binder and less curling of the recording paper and from the viewpoint of high binder capacity of inorganic fine particles and excellent cracking and film-forming properties when used in a small amount.

  As polyvinyl alcohol preferably used in the present invention, in addition to ordinary polyvinyl alcohol obtained by hydrolyzing polyvinyl acetate, modified polyvinyl alcohol such as polyvinyl alcohol having a cation-modified terminal or anion-modified polyvinyl alcohol having an anionic group. Alcohol is also included.

  The polyvinyl alcohol obtained by hydrolyzing vinyl acetate preferably has an average degree of polymerization of 300 or more, particularly preferably an average degree of polymerization of 1,000 to 5,000, and a saponification degree of 70. ~ 100% is preferable, and 80 ~ 99.8% is particularly preferable.

  Examples of the cation-modified polyvinyl alcohol include polyvinyl having a primary to tertiary amino group or a quaternary amino group in the main chain or side chain of the polyvinyl alcohol as described in JP-A No. 61-10383. These are alcohols, which are obtained by saponifying a copolymer of an ethylenically unsaturated monomer having a cationic group and vinyl acetate.

  Examples of the ethylenically unsaturated monomer having a cationic group include trimethyl- (2-acrylamido-2,2-dimethylethyl) ammonium chloride and trimethyl- (3-acrylamido-3,3-dimethylpropyl) ammonium chloride. N-vinylimidazole, N-methylvinylimidazole, N- (3-dimethylaminopropyl) methacrylamide, hydroxyethyltrimethylammonium chloride, trimethyl- (3-methacrylamidopropyl) ammonium chloride, and the like.

  The ratio of the cation-modified group-containing monomer of the cation-modified polyvinyl alcohol is 0.1 to 10 mol%, preferably 0.2 to 5 mol%, relative to vinyl acetate.

  Examples of the anion-modified polyvinyl alcohol include polyvinyl alcohol having an anionic group described in JP-A-1-206088, vinyl alcohol described in JP-A-61-237681 and JP-A-63-330779, and water-soluble. And a copolymer with a vinyl compound having a functional group, and a modified polyvinyl alcohol having a water-soluble group described in JP-A-7-285265.

  Nonionic modified polyvinyl alcohol is, for example, a polyvinyl alcohol derivative obtained by adding a polyalkylene oxide group described in JP-A-7-9758 to a part of vinyl alcohol, and described in JP-A-8-25795. And a block copolymer of a vinyl compound having a hydrophobic group and vinyl alcohol.

  Polyvinyl alcohol can be used in combination of two or more, such as the degree of polymerization and the type of modification. In particular, when using polyvinyl alcohol having a degree of polymerization of 2,000 or more, the degree of polymerization is from 0.05 to 10% by weight, preferably 0.1 to 5% by weight, based on the inorganic fine particles. Addition of 2,000 or more polyvinyl alcohol is preferred because there is no significant thickening.

  Further, as the hydrophilic resin of the ink receiving layer according to the present invention, it is preferable to use a polymer compound that is crosslinked or polymerized by ionizing radiation. The high molecular compound that is crosslinked or polymerized by ionizing radiation is a water-soluble resin that undergoes a reaction to undergo crosslinking or polymerization by irradiation with ionizing radiation such as ultraviolet rays and electron beams, and is water-soluble before the reaction. However, it is a resin that becomes substantially water-insoluble after the reaction. The resin has hydrophilicity after the reaction and maintains sufficient affinity with ink.

  Such resins include saponified polyvinyl acetate, polyvinyl acetal, polyethylene oxide, polyalkylene oxide, polyvinyl pyrrolidone, polyacrylamide, hydroxyethyl cellulose, methyl cellulose, hydroxypropyl cellulose, or derivatives of the hydrophilic resins, and It is at least one selected from the group consisting of copolymers, or a hydrophilic resin modified with a modifying group such as a photodimerization type, a photodecomposition type, a photopolymerization type, a photomodification type, or a photodepolymerization type It is. Among them, a resin modified with a photodimerization type or a photopolymerization type modification group is preferable from the viewpoint of sensitivity or stability of the resin itself. As the photodimerization-type modifying group, those having a diazo group, a cinnamoyl group, a styrylpyridinium group, or a stilquinolium group introduced are preferable, and a resin that is dyed with a water-soluble dye such as an anionic dye after photodimerization is preferable. Examples of such resins include resins having a cationic period such as primary amino group or quaternary ammonium group, such as JP-A-62-283339, JP-A-1-198615, JP-A-60-252341. No., JP-A 56-67309, JP-A 60-129742, etc., photosensitive resins (compositions), and after curing, become cationic after curing such as an azide group that becomes an amino group Examples of the resin include photosensitive resins (compositions) described in JP-A-56-67309.

  Specific examples include the following compounds, but the present invention is not limited only to these compounds.

  The photosensitive resin described in JP-A-56-67309 contains the following formula (I) in a polyvinyl alcohol structure.

2-azido-5-nitrophenylcarbonyloxyethylene structure represented by the following formula (II)

It is a resin composition which has 4-azido-3-nitrophenyl carbonyloxyethylene structure represented by these.

  Specific examples of the photosensitive resin are described in Examples 1 and 2 in the official gazette, and the constituent components and usage ratio of the photosensitive resin are described on page 2 of the official gazette.

  JP-A-60-129742 discloses the following formulas (III) and (IV) in a polyvinyl alcohol structure as a photosensitive resin.

The resin composition which has the following structure is mentioned.

  In the present invention, among the hydrophilic resins that are cross-linked by ionizing radiation, examples of the photopolymerizable modifying group include a structural unit represented by the following general formula (A) disclosed in JP-A No. 2000-181062. Polyvinyl acetate saponified product having the above is preferable from the viewpoint of reactivity.

In the general formula (A), R ₁ represents a hydrogen atom or a methyl group, Y represents an aromatic ring or a simple bond, and X represents — (CH ₂ ) _m —COO—, —O—CH ₂ —. COO- or -O- is represented, m is an integer of 0-6, n represents 1 or 2.

  In the present invention, it is preferable to add a photoinitiator or a sensitizer together with a hydrophilic resin containing a polymer compound polymerized by ionizing radiation. These compounds may be chemically bonded to a hydrophilic resin containing the above polymer compound in a dissolved or dispersed state in a solvent.

  The photoinitiator and photosensitizer to be applied are not particularly limited, and conventionally known photoinitiators or photosensitizers can be used. For example, benzophenones (for example, benzophenone, hydroxybenzophenone, bis- N, N-dimethylaminobenzophenone, bis-N, N-diethylaminobenzophenone, 4-methoxy-4′-dimethylaminobenzophenone, etc.), thioxanthones (eg, thixatone, 2,4-diethylthioxanthone, isopropylthioxanthone, chlorothioxanthone, Isopropoxychlorothioxanthone), anthraquinones (eg, ethyl anthraquinone, benzanthraquinone, aminoanthraquinone, chloroanthraquinone, etc.), acetophenones, benzoin ethers (eg, benzoin) Tilether, etc.), 2,4,6-trihalomethyltriazines, 1-hydroxycyclohexyl phenyl ketone, 2- (o-chlorophenyl) -4,5-diphenylimidazole dimer, 2- (o-chlorophenyl) -4, 5-di (m-methoxyphenyl) imidazole dimer, 2- (o-fluorophenyl) -4,5-phenylimidazole dimer, 2- (o-methoxyphenyl) -4,5-phenylimidazole dimer , 2- (p-methoxyphenyl) -4,5-diphenylimidazole dimer, 2, -di (p-methoxyphenyl) -5-phenylimidazole dimer, 2- (2,4-dimethoxyphenyl) 2,4,5-diphenylimidazole dimer 2,4,5-triarylimidazole dimer, benzyldimethyl ketal, 2- N-di-2-dimethylamino-1- (4-morpholinophenyl) -butan-1-one, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholino-1-propanone, 2-hydroxy-2 -Methyl-1-phenyl-propan-1-one, 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propan-1-one, phenanthrenequinone, 9,10 -Benzoins such as phenanthrenequinone, methylbenzoin, ethylbenzoin, acridine derivatives (for example, 9-phenylacridine, 1,7-bis (9,9'-acridinyl) heptane, etc.), bisacylphosphine oxide and the like The above-mentioned compounds may be used alone or in combination of two or more.

  In particular, water-soluble 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propan-1-one, 4- (2-hydroxyethoxy) -phenyl- (2- Water-soluble initiators such as hydroxy-2-propyl) ketone, thioxanthone ammonium salt, and benzophenone ammonium salt are preferable from the viewpoint of crosslink efficiency because of excellent mixing properties.

  In addition to these initiators, accelerators and the like can also be added. Examples of these include ethyl p-dimethylaminobenzoate, isoamyl p-dimethylaminobenzoate, ethanolamine, diethanolamine, triethanolamine and the like.

  In such a resin, the polymerization degree of the mother polyvinyl alcohol resin is preferably 300 or more, and more preferably 1700 or more. The modification rate of the ionizing radiation reaction-modifying group with respect to the segment is preferably 4 mol% or less, more preferably 1 mol% or less. If the polymerization degree of the segment is 300 or less or the modification rate exceeds 4 mol%, the crosslinking density of the coating film is too high, and the breakability of the dried coating film is remarkably deteriorated. At the same time, if the crosslinking density is too high, the balance between hygroscopicity and dimensional stability with the substrate is poor, and curling resistance is deteriorated.

  In the method for producing an inkjet recording medium of the present invention, when a polymer compound is used as the hydrophilic resin by ionizing radiation, a coating solution containing the polymer compound is applied by ionizing radiation, and the total solid content of the coating layer is applied. The coating layer is gelled by irradiating ionizing radiation at a concentration of 5 to 90%, and then dried. Examples of the ionizing radiation in the present invention include electron beams, ultraviolet rays, α rays, β rays, γ rays, and X-rays. In view of the widespread use of electron beam, ultraviolet rays or ultraviolet rays are preferable.

  Examples of the electron beam irradiation method include a scanning method, a curtain beam method, and a broad beam method. The curtain beam method is preferable from the viewpoint of processing capability. The acceleration voltage of the electron beam can be changed as appropriate depending on the specific gravity and film pressure of the coating film, but 20 kV to 300 kV is appropriate. The irradiation amount of the electron beam is preferably in the range of 0.1 to 20 Mrad.

  As the ultraviolet light source, for example, low pressure, medium pressure, high pressure mercury lamp, metal halide lamp and the like having an operating pressure of 100 Pa to 1 MPa are used. From the viewpoint of wavelength distribution of the light source, a high pressure mercury lamp and a metal halide lamp are preferable, and a metal halide lamp is more preferable. preferable.

In particular, when the wavelength of the light source includes ultraviolet rays of 300 nm or less, or when the irradiation energy exceeds 100 J / cm ² , the core of the ionizing radiation crosslinkable resin or various coexisting additives are decomposed by ionizing radiation. In addition to not being able to obtain the effects of the present invention, there is a possibility that problems such as odor derived from the decomposition products may occur. On the contrary, when the irradiation energy is less than 0.1 mJ / cm ² , the crosslinking efficiency is insufficient and the effect of the present invention cannot be sufficiently obtained. Therefore, it is preferable to provide a filter that cuts light having a wavelength of 300 nm or less as the light source, and the output of the lamp is preferably 400 W to 30 kW and the illuminance is preferably 10 mW / cm ^{2 to} 10 kW / cm ² . Preferably as the radiation energy is 0.1mJ / cm ² ~100mJ / cm ² in the present invention, more preferably ^{1mJ / cm 2 ~50mJ / cm 2} .

When giving the same integrated light quantity (mJ / cm ² ), the preferable range of illuminance is due to the change in the light transmittance. When the concentration distribution of the generated cross-linking reactive species is different due to the transmittance of ultraviolet rays, and the ultraviolet illuminance is high, a high concentration of cross-linking reactive species is generated on the surface layer, and a hard and dense film is formed on the surface of the coating film. When the illuminance is in a preferable range, the degree of cross-linking of the surface layer is low and light permeability in the deep direction is high, so that gentle cross-linking is uniformly formed in the deep direction. If the illuminance is too low, it takes a long time to give the necessary integrated illuminance, which is not only disadvantageous in terms of equipment introduction, but also because the amount of absolute light due to scattering of ultraviolet rays by the coating film is insufficient. Absent.

  The ratio of the inorganic fine particles to the hydrophilic resin of the ink receiving layer is preferably 2 to 20 by mass ratio. If the mass ratio is 2 times or more, a porous film having a sufficient porosity can be obtained, and a sufficient void volume can be easily obtained without causing a situation where the voids are blocked by swelling during ink jet recording with a hydrophilic resin that can be maintained. As a result, a high ink absorption speed can be maintained. On the other hand, if this ratio is 20 times or less, cracks are less likely to occur when the ink receiving layer is applied as a thick film. The ratio of the inorganic fine particles to the particularly preferable hydrophilic resin is 2.5 to 12 times, most preferably 3 to 10 times.

  Various additives may be added to the water-soluble coating liquid for forming the ink receiving layer or other constituent layers according to the present invention. Examples of such additives include cationic mordants, polyvalent metal compounds, polystyrene, polyacrylates, polymethacrylates, polyacrylamides, polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, or these Copolymers, organic latex fine particles such as urea resin or melamine resin, anionic, cationic, nonionic and amphoteric surfactants, JP-A-57-74193, JP-A-57-87988, and JP-A-62-261476 Described in JP-A-57-74192, JP-A-57-87989, JP-A-60-72785, JP-A-61465991, JP-A-1-95091 and JP-A-3-13376. Anti-fading agents, JP-A-59-42993, 59-52689, 62-2 No. 0069, JP-A-61-228771 and JP-A-4-219266, etc., pH brighteners such as sulfuric acid, phosphoric acid, citric acid, sodium hydroxide, potassium hydroxide and potassium carbonate, Various known additives such as antifoaming agents, preservatives, thickeners, antistatic agents and matting agents can also be contained.

  As the cationic mordant, a polymer mordant having a primary to tertiary amino group and a quaternary ammonium base is used, but there is little discoloration or deterioration of light resistance during long-term storage, and the mordant ability of the dye is sufficiently high. Therefore, a polymer mordant having a quaternary ammonium base is preferable. A preferred polymer mordant is obtained as a homopolymer of a monomer having the quaternary ammonium base, a copolymer with another monomer, or a condensation polymer.

  In the ink jet recording medium of the present invention, it is particularly preferable that the ink receiving layer contains a polyvalent metal compound.

  Examples of the polyvalent metal compound according to the present invention include metal compounds such as aluminum, calcium, magnesium, zinc, iron, strontium, barium, nickel, copper, scandium, gallium, indium, titanium, zirconium, tin, and lead. The polyvalent metal compound may be a polyvalent metal salt. Among them, the compound composed of magnesium, aluminum, zirconium, calcium, and zinc is preferable because it is colorless, the polyvalent metal compound is more preferably a compound containing a zirconium atom, an aluminum atom, or a magnesium atom, and the polyvalent metal compound has a zirconium atom. It is especially preferable that it is a compound containing.

  The compound containing a zirconium atom, an aluminum atom or a magnesium atom that can be used in the present invention (excluding zirconium oxide and aluminum oxide) may be water-soluble or water-insoluble. It is preferable that the ink can be uniformly added to a desired position of the ink receiving layer.

  Further, the compound containing a zirconium atom, an aluminum atom or a magnesium atom that can be used in the present invention may be any of a single salt and a double salt of an inorganic acid or an organic acid, an organic metal compound, a metal complex, Those that can be uniformly added to desired positions of the ink receiving layer are preferred.

  Specific examples of the compound containing a zirconium atom that can be used in the present invention include zirconium difluoride, zirconium trifluoride, zirconium tetrafluoride, hexafluorozirconate (for example, potassium salt), heptafluorozirconate. (For example, sodium salt, potassium salt or ammonium salt), octafluorozirconium salt (for example, lithium salt), fluorinated zirconium oxide, zirconium dichloride, zirconium trichloride, zirconium tetrachloride, hexachlorozirconium salt (for example, sodium Salt or potassium salt), zirconium oxychloride (eg, zirconyl chloride), zirconium dibromide, zirconium tribromide, zirconium tetrabromide, zirconium bromide oxide, zirconium triiodide, zirconium tetraiodide, zirconium peroxide Zirconium hydroxide, zirconium sulfide, zirconium sulfate, zirconium p-toluenesulfonate, zirconyl sulfate, sodium zirconyl sulfate, acidic zirconyl sulfate trihydrate, potassium zirconium sulfate, zirconium selenate, zirconium nitrate, zirconyl nitrate, phosphoric acid Zirconium, zirconyl carbonate, zirconyl ammonium carbonate, zirconium acetate, zirconyl acetate, zirconyl ammonium acetate, zirconyl lactate, zirconyl citrate, zirconyl stearate, zirconium phosphate, zirconyl phosphate, zirconium oxalate, zirconium isopropylate, zirconium butyrate, Zirconium acetylacetonate, acetylacetone zirconium butyrate, zirconium stearate butyrate, zirco Um acetate, bis (acetylacetonato) dichloro zirconium and tris (acetylacetonato) such as chloro zirconium are exemplified.

  Among these compounds containing zirconium atoms, zirconyl carbonate, zirconyl ammonium carbonate, zirconyl acetate, zirconyl nitrate, zirconium oxychloride, zirconyl lactate and zirconyl citrate are preferable, and zirconium oxychloride, zirconyl ammonium carbonate and zirconyl acetate are particularly preferable.

  Specific examples of the compound containing an aluminum atom that can be used in the present invention include aluminum fluoride, hexafluoroaluminic acid (for example, potassium salt), aluminum chloride, basic aluminum chloride (polyaluminum chloride), and tetrachloroalumine. Acid salts (for example, sodium salt), aluminum bromide, tetrabromoaluminate (for example, potassium salt), aluminum iodide, aluminate (for example, sodium salt, potassium salt, calcium salt), chloric acid Aluminum, aluminum perchlorate, aluminum thiocyanate, aluminum sulfate, basic aluminum sulfate, potassium aluminum sulfate (alum), ammonium aluminum sulfate (ammonium alum), sodium aluminum sulfate, aluminum phosphate Aluminum nitrate, aluminum hydrogen phosphate, aluminum carbonate, aluminum polysulfate silicate, aluminum formate, aluminum acetate, aluminum lactate, aluminum oxalate, aluminum isopropylate, aluminum butyrate, ethyl acetate aluminum diisopropylate, aluminum tris (acetylacetonate) , Aluminum tris (ethyl acetoacetate), aluminum monoacetylacetonate bis (ethyl acetoacetonate), and the like. Among these, aluminum chloride, basic aluminum chloride, aluminum sulfate, basic aluminum sulfate, and basic aluminum sulfate silicate are preferable.

  Specific examples of the compound containing a magnesium atom that can be used in the present invention include magnesium fluoride, magnesium acetate, magnesium bromide, magnesium chloride, magnesium formate, magnesium nitrate, magnesium sulfate, magnesium thiocyanate, magnesium thiosulfate, and sulfide. Examples thereof include magnesium, magnesium carbide, and magnesium phosphate. Among these, magnesium chloride, magnesium sulfate, and magnesium nitrate are preferable.

  Among these polyvalent metal compounds, particularly preferable ones are those exemplified as preferred compounds containing zirconium atoms, those exemplified as preferred compounds containing aluminum atoms, and preferred compounds containing magnesium atoms. Among those exemplified are zirconyl carbonate, zirconyl ammonium carbonate, zirconyl acetate, zirconyl nitrate, zirconium oxychloride, zirconyl lactate, zirconyl citrate, basic aluminum chloride, magnesium chloride, magnesium sulfate and basic aluminum sulfate silicate. In particular, zirconium oxychloride, zirconyl ammonium carbonate and zirconyl acetate are preferable, and zirconium oxychloride is most preferable.

  The use amount of the cationic polymer or the water-soluble polyvalent metal compound is preferably 10% by mass or less, more preferably 8% by mass or less in terms of the mass ratio with respect to the inorganic fine particles, in order to suppress deterioration of ink absorbability. .

  As a method for adding a cationic polymer or a water-soluble polyvalent metal compound, in addition to a method in which it is directly added to a coating solution, a cationic resin or a water-soluble polyvalent metal compound is added after the recording paper is coated and dried. A method of overcoating with an aqueous solution and drying may also be used.

  It is preferable to add a hardener of a water-soluble binder that forms an ink receiving layer to the ink jet recording medium of the present invention.

  The curing agent that can be used in the present invention is not particularly limited as long as it causes a curing reaction with a water-soluble binder, but boric acid and its salts are preferable, but other known ones can be used. Specifically, it is a compound having a group capable of reacting with a water-soluble binder or a compound that promotes the reaction between different groups of the water-soluble binder, and is appropriately selected depending on the type of the water-soluble binder. Specific examples of the curing agent include, for example, epoxy curing agents (diglycidyl ethyl ether, ethylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,6-diglycidyl cyclohexane, N, N-diglycidyl- 4-glycidyloxyaniline, sorbitol polyglycidyl ether, glycerol polyglycidyl ether, etc.), aldehyde curing agents (formaldehyde, glioxal, etc.), active halogen curing agents (2,4-dichloro-4-hydroxy-1,3,5) -S-triazine, etc.), active vinyl compounds (1,3,5-trisacryloyl-hexahydro-s-triazine, bisvinylsulfonylmethyl ether, etc.), aluminum alum and the like.

  Boric acid or a salt thereof refers to an oxygen acid having a boron atom as a central atom and a salt thereof, specifically, orthoboric acid, diboric acid, metaboric acid, tetraboric acid, pentaboric acid, and octaboron. Examples include acids and their salts.

  Boric acid having a boron atom and a salt thereof as a curing agent may be used as a single aqueous solution or as a mixture of two or more. Particularly preferred is a mixed aqueous solution of boric acid and borax. The aqueous solutions of boric acid and borax can be added only in relatively dilute aqueous solutions, respectively, but by mixing both, a concentrated aqueous solution can be obtained and the coating solution can be concentrated. Further, there is an advantage that the pH of the aqueous solution to be added can be controlled relatively freely. The total amount of the curing agent used is preferably 1 to 600 mg per 1 g of the water-soluble binder.

  In the recording paper of the present invention, the viscosity of the ink receiving layer coating solution is preferably 0.010 to 0.300 Pa · s at 40 ° C., and a more preferable viscosity range is 0.025 to 0.100 Pa · s. If the viscosity of the coating liquid becomes too high, it cannot be supplied to the coating apparatus, resulting in poor liquid feeding.

  As the support that can be used in the present invention, a conventionally known non-water-absorbing support for inkjet recording media can be used as appropriate.

Non-water-absorbing supports that can be preferably used in the present invention include transparent supports and opaque supports. Examples of the transparent support include films having materials such as polyester resins, diacetate resins, triatesate resins, acrylic resins, polycarbonate resins, polyvinyl chloride resins, polyimide resins, cellophane, and celluloid. Among them, those having a property of resisting radiant heat when used for overhead projectors (OHP) are preferable, and polyethylene terephthalate is particularly preferable. The thickness of such a transparent support is preferably 50 to 200 μm. Further, as the opaque support, for example, resin-coated paper (so-called RC paper) having a polyolefin resin coating layer in which white pigment or the like is added to at least one of the base paper, white pigment such as barium sulfate is added to polyethylene terephthalate. A so-called white pet is preferable. For the purpose of increasing the adhesive strength between the various supports and the ink receiving layer, it is preferable to subject the support to a corona discharge treatment or a subbing treatment prior to the application of the ink receiving layer. Furthermore, the inkjet recording medium of the present invention is not necessarily colorless, and may be a colored recording sheet.
In the ink jet recording medium of the present invention, it is particularly preferable to use a paper support obtained by laminating both sides of a base paper support with polyethylene because the recorded image is close to photographic image quality and a high quality image can be obtained at low cost.

  Such a paper support laminated with polyethylene will be described below.

The base paper used for the paper support is made from wood pulp as a main raw material and, if necessary, paper making using synthetic pulp such as polypropylene or synthetic fibers such as nylon or polyester in addition to wood pulp. As wood pulp, any of LBKP, LBSP, NBKP, NBSP, LDP, NDP, LUKP, and NUKP can be used, but it is preferable to use more LBKP, NBSP, LBSP, NDP, and LDP with a large amount of short fibers. . However, the ratio of LBSP or LDP is preferably 10 to 70% by mass. The pulp is preferably a chemical pulp (sulfate pulp or sulfite pulp) with few impurities, and a pulp having a whiteness improved by bleaching is also useful. In the base paper, sizing agents such as higher fatty acids and alkyl ketene dimers, white pigments such as calcium carbonate, talc and titanium oxide, paper strength enhancing agents such as starch, polyacrylamide and polyvinyl alcohol, fluorescent whitening agents, polyethylene glycols A water retaining agent such as a dispersant, a softening agent such as a quaternary ammonium, and the like can be appropriately added. The freeness of the pulp used for papermaking is preferably 200 to 500 ml as defined by CSF, and the fiber length after beating is the mass% of the 24 mesh residue defined by JIS-P-8207 and the 42 mesh residue. The sum of the mass% of the minute is preferably 30 to 70%. In addition, it is preferable that the mass% of 4 mesh remainder is 20 mass% or less. The basis weight of the base paper is preferably 30 to 250 g, particularly preferably 50 to 200 g. The thickness of the base paper is preferably 40 to 250 μm. The base paper can be given a high smoothness by calendering at the paper making stage or after paper making. The density of the base paper is generally 0.7 to 1.2 g / cm ³ (JIS-P-8118). Furthermore, the base paper stiffness is preferably 20 to 200 g under the conditions specified in JIS-P-8143. A surface sizing agent may be applied to the surface of the base paper. The pH of the base paper is preferably 5 to 9 when measured by a hot water extraction method defined in JIS-P-8113. The polyethylene that covers the front and back surfaces of the base paper is mainly low-density polyethylene (LDPE) and / or high-density polyethylene (HDPE), but some other LLDPE, polypropylene, and the like can also be used. In particular, the polyethylene layer on the ink receiving layer side is preferably one in which rutile or anatase type titanium oxide is added to polyethylene to improve opacity and whiteness, as is widely done in photographic paper. The titanium oxide content is usually 3 to 20% by mass, preferably 4 to 13% by mass, based on polyethylene. Polyethylene-coated paper can be used as glossy paper, or when the polyethylene is melt-extruded onto the surface of the base paper and coated, a so-called molding process is performed to form a matte or silky surface that can be obtained with ordinary photographic paper These can also be used in the present invention. In the polyethylene-coated paper, the water content in the paper is particularly preferably maintained at 3 to 10% by mass.

  In the ink jet recording medium of the present invention, the method for applying the constituent layer such as the ink receiving layer according to the present invention on the support can be appropriately selected from known methods. A preferred method is obtained by coating a coating liquid constituting each layer on a support and drying. In this case, two or more layers can be applied simultaneously. As the coating method, for example, a roll coating method, a rod bar coating method, an air knife coating method, a spray coating method, a curtain coating method, or an extrusion coating method using a hopper described in US Pat. No. 2,681,294 is preferable. Used.

  Next, an ink-jet ink (hereinafter also simply referred to as ink) used for printing an image on the ink-jet recording medium of the present invention will be described.

  As the ink used in the inkjet recording medium of the present invention, a water-based ink composition, an oil-based ink composition, a solid (phase change) ink composition, or the like can be used. A water-based inkjet recording liquid containing 10% by mass or more of water can be particularly preferably used.

  As the colorant used in the ink, conventionally known water-soluble dyes such as acid dyes, direct dyes, reactive dyes, disperse dyes, pigments and the like can be used.

  The water-based ink composition is preferably used in combination with a water-soluble organic solvent. Examples of the water-soluble organic solvent that can be used in the present invention include alcohols (for example, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, secondary butanol, tertiary butanol, pentanol, hexanol, cyclohexanol, benzyl). Alcohol), polyhydric alcohols (for example, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, butylene glycol, hexanediol, pentanediol, glycerin, hexanetriol, thiodiglycol Etc.), polyhydric alcohol ethers (for example, ethylene glycol monomethyl ether, ethylene glycol) Ether monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether , Triethylene glycol monobutyl ether, ethylene glycol monophenyl ether, propylene glycol monophenyl ether, etc.), amines (for example, ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, mole) Phosphorus, N-ethylmorpholine, ethylenediamine, diethylenediamine, triethylenetetramine, tetraethylenepentamine, polyethyleneimine, pentamethyldiethylenetriamine, tetramethylpropylenediamine, etc.), amides (eg, formamide, N, N-dimethylformamide, N , N-dimethylacetamide, etc.), heterocyclic rings (for example, 2-pyrrolidone, N-methyl-2-pyrrolidone, cyclohexylpyrrolidone, 2-oxazolidone, 1,3-dimethyl-2-imidazolidinone, etc.), sulfoxides ( For example, dimethyl sulfoxide etc.), sulfones (for example, sulfolane etc.), urea, acetonitrile, acetone etc. are mentioned. Preferable water-soluble organic solvents include polyhydric alcohols. Furthermore, it is particularly preferable to use a polyhydric alcohol and a polyhydric alcohol ether in combination. The water-soluble organic solvent may be used alone or in combination. The total amount of the water-soluble organic solvent added to the ink is 5 to 60% by mass, preferably 10 to 35% by mass.

  The ink composition used in the present invention may contain various known additions depending on the purpose of improving ejection stability, print head and ink cartridge compatibility, storage stability, image storability, and other various performances as necessary. Agents, such as viscosity modifiers, surface tension modifiers, specific resistance modifiers, film forming agents, dispersants, surfactants, UV absorbers, antioxidants, anti-fading agents, antifouling agents, rust inhibitors, etc. For example, polystyrene, polyacrylates, polymethacrylates, polyacrylamides, polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, or a copolymer thereof, urea resin Or organic latex fine particles such as melamine resin, liquid paraffin, dioctyl phthalate, tricresyl phosphate, silicone oil Oil droplet fine particles, cationic or nonionic surfactants, ultraviolet absorbers described in JP-A-57-74193, JP-A-57-87988, and JP-A-62-261476, JP-A-57-74192 and 57 -878989, 60-72785, 61-146591, JP-A-1-95091 and 3-13376, etc., JP-A-59-42993, 59-52689 Fluorescent brighteners, sulfuric acid, phosphoric acid, citric acid, sodium hydroxide, potassium hydroxide, potassium carbonate, etc. described in Nos. 62-280069, 61-242871, and JP-A-4-219266 PH adjusters and the like.

  The ink composition has a viscosity at the time of flight of preferably 40 mPa · s or less, and more preferably 30 mPa · s or less. The ink composition has a surface tension during flight of preferably 20 mN / m or more, and more preferably 30 to 45 mN / m.

  The ink jet head used in the ink jet recording method using the ink jet recording medium of the present invention may be an on-demand system or a continuous system. In addition, as a discharge method, an electro-mechanical conversion method (for example, a single cavity type, a double cavity type, a bender type, a piston type, a shear mode type, a shared wall type, etc.), an electro-thermal conversion method (for example, a thermal type) Specific examples include an ink jet type, a bubble jet (registered trademark) type, and an electrostatic suction method (for example, an electrolysis control type, a slit jet type, etc.). I do not care.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In the examples, “%” represents mass% unless otherwise specified.

<< Production of non-water-absorbing support >>
Moisture content 6.5%, on the back side of the photographic base paper having a basis weight of 170 g / m ^2, density coated with low density polyethylene 0.92 at a thickness of 20μm by the extrusion coating method, subjected to corona discharge Then, the latex layer was applied so that the thickness was 0.2 g / m ² . Next, a low density polyethylene containing 5.5% anatase-type titanium oxide and having a density of 0.92 is applied to the front side (ink receiving layer coating surface side) by a melt extrusion coating method with a thickness of 14 μm, and then After performing corona discharge on this surface, a gelatin subbing layer containing a crosslinking agent was applied to a thickness of 0.03 g / m ² to prepare a non-water-absorbing support having both surfaces coated with polyethylene. did.

<< Preparation of silica dispersion >>
Using a jet stream inductor mixer manufactured by Mitamura Riken Kogyo Co., Ltd., 10 kg of vapor-phase method silica (trade name: Aerosil 300, manufactured by Nippon Aerosil Co., Ltd., average particle diameter of primary particles: 7 nm) After sucking and dispersing in an aqueous solution obtained by adding 435 ml of ethanol to water at room temperature, pure water was added to make the total volume to 43.5 L to obtain a finished dispersion. This dispersion has a pH of 2.8 and contains 1% by mass of ethanol.

  Next, to 420 g of this dispersion, 40 g of a 28% aqueous solution of the cationic polymer P-1, 2.1 ml of boric acid and 1.5 g of borax were dissolved, and pre-dispersed with a dissolver. Furthermore, it was dispersed for 30 minutes at a peripheral speed of 9 m / sec using a sand mill disperser. After finishing the total amount of this dispersion liquid to 630 g, it filtered using the TCP-10 type filter made from Advantex Toyo Co., Ltd., and prepared the substantially transparent silica dispersion liquid.

  The silica dispersion was diluted and coated on a transparent support, and the particle size of 100 arbitrary silica particles was determined with an electron microscope, and the simple average value (number average) was determined as the average particle size. , 50 nm. Here, each particle size is expressed by a diameter assuming a circle equal to the projected area.

<< Preparation of copolymer >>
[Preparation of copolymer A]
The system was purged with nitrogen while stirring 500 g of diol type polypropylene oxide (molecular weight 700, manufactured by Wako Pure Chemical Industries, Ltd.) and potassium hydroxide as a catalyst in an SUS316 autoclave. After completion of the nitrogen replacement, the temperature was raised to 120 ° C. in an oil bath, and 170 g of ethylene oxide was fed at a reaction temperature of 135 ° C. and a reaction pressure of 0.25 MPa or less. After completion of the feed, the mixture was aged at 135 ° C. for 8 hours. After aging, unreacted ethylene oxide in the system was removed under reduced pressure. After neutralizing potassium hydroxide with potassium hydroxide and an equimolar amount of acetic acid, the salt was removed by filtration to obtain copolymer A.

  As a result of measuring the average molecular weight of the copolymer A by gel permeation chromatography (manufactured by Nippon Analytical Industrial Co., Ltd.), the average molecular weight of the copolymer A was about 930.

  Moreover, as a result of calculating | requiring the polyethylene oxide chain ratio measured according to the following Formula (1), it was 25 mass%.

Formula 1
Ethylene oxide chain ratio = {(average molecular weight) − (molecular weight of polypropylene oxide)} / (average molecular weight) × 100 (mass%)
[Preparation of copolymers B to H]
In the preparation of the copolymer A, except that the molecular weight of the polypropylene oxide used and the feed amount of the ethylene oxide were appropriately changed, the copolymer B comprising the average molecular weight and the polyethylene oxide chain ratio shown in Table 1 were similarly used. H was prepared.

[Preparation of copolymer I]
The system was purged with nitrogen while stirring 170 g of polyethylene glycol (molecular weight: 200, manufactured by Wako Pure Chemical Industries, Ltd.) and potassium hydroxide as a catalyst in an SUS316 autoclave. After completion of nitrogen substitution, the temperature was raised to 120 ° C. in an oil bath, and 500 g of polypropylene oxide was fed at a reaction temperature of 135 ° C. and a reaction pressure of 0.25 MPa or less. After the feed, the mixture was aged at 135 ° C. for 25 hours. After aging, unreacted propylene oxide in the system was removed under reduced pressure. After neutralizing potassium hydroxide with potassium hydroxide and an equimolar amount of acetic acid, the salt was removed by filtration, and copolymer I was prepared. The average molecular weight of the copolymer I was about 750, and the ethylene oxide chain ratio determined according to the following formula (2) was 26%.

Formula 2
Ethylene oxide chain ratio = {(average molecular weight) − (molecular weight of polyethylene glycol)} / (average molecular weight) × 100 (mass%)
<Production of recording medium>
[Production of Recording Medium 1]
While stirring 600 g of the silica dispersion prepared above at 40 ° C., 200 g of a 10% aqueous solution of polyvinyl alcohol (trade name: PVA235, manufactured by Kuraray Co., Ltd.) was added, and 4 g of copolymer A prepared above was further added. Then, pure water was added so that the total amount became 1000 ml, and a translucent ink receiving layer coating solution 1 was obtained. The ink-receiving layer coating liquid 1 was applied to the ink-receiving layer-coated surface of the non-water-absorbing support prepared above with a bar coater at a wet film thickness of 150 μm, and then dried with hot air at 70 ° C. with a dryer. A recording medium 1 was obtained.

[Preparation of recording media 2 to 13]
In the production of the recording medium 1, the copolymer A (4 g) used for the preparation of the ink-receiving layer coating liquid 1 was changed to the copolymer types and addition amounts shown in Table 2 in the same manner. Recording media 2 to 13 were produced.

[Production of Recording Medium 14]
While stirring 630 g of the silica dispersion prepared above at 40 ° C., 200 g of a 10% aqueous solution of polyvinyl alcohol (trade name: PVA235, manufactured by Kuraray Co., Ltd.) is added, and pure water is added so that the total amount becomes 1000 ml. A translucent ink receiving layer coating solution was obtained. This ink-receiving layer coating solution was applied to the ink-receiving layer-coated side of the non-water-absorbing support prepared above with a bar coater at a wet film thickness of 150 μm, and then dried with hot air at 80 ° C. with a dryer. Medium 14 was obtained.

<Evaluation of recording medium>
Each of the produced recording media was evaluated according to the following methods.

[Evaluation of image quality characteristics]
Print solid image (output condition: 70%) in PM photo paper-super high definition mode with genuine black ink on the ink receiving layer side of each recording medium using PM-G800 manufactured by Seiko Epson as an inkjet printer. The mottled printing unevenness of the formed solid image was visually observed, and the image quality characteristics were evaluated according to the following criteria.

A: Mottled printing unevenness is not observed even at an observation distance of 10 cm. O: Weak mottled printing unevenness is observed at an observation distance of 10 cm, but no mottled printing unevenness is observed at an observation distance of 30 cm. Weak mottled printing unevenness is observed at an observation distance of 30 cm, but no mottled printing unevenness is observed at an observation distance of 60 cm. X: Obvious mottled printing unevenness is observed even at an observation distance of 60 cm. Evaluation of suitability: measurement of coating solution viscosity and film surface observation)
The viscosity at 40 ° C. of the ink receiving layer coating solution used for the production of each recording medium was measured with a drop viscometer (Ostwald viscometer), and further, the coating failure on the ink receiving layer surface side was visually observed. Application suitability was evaluated according to the standard.

A: The ink receiving layer coating solution viscosity is less than 100 mPa · s, and no occurrence of coating failure is observed at all. ○: The ink receiving layer coating solution viscosity is 100 mPa · s or more and less than 200 mPa · s, and an application failure occurs. Δ: The ink receiving layer coating solution viscosity is 200 mPa · s or more and less than 500 mPa · s, and minute coating failures (spraying failures) are sporadic. ×: The ink receiving layer coating solution viscosity is 500 mPa · s. More than s and application failure (repellency failure) has clearly occurred [Evaluation of crack resistance]
With respect to 100 cm ² of the ink receiving layer surface of each recording medium, the presence or absence of a crack failure was observed with a loupe, and the crack resistance was evaluated according to the following criteria.

◎: No crack failure is observed. ○: The number of crack failures of about 0.5 mm is 1 or more and less than 5. No crack failure of 1.0 mm or more is observed. There are 5 or more and less than 20 cracks of about 5 mm, and 1 or more crack failures of 1.0 mm or more have occurred. ×: Many crack failures of 1.0 mm or more have occurred on the entire surface. Thus, the smoothness of the print is clearly inferior. In each of the above evaluation ranks, it was judged that the quality was acceptable in practice if it was in the range of ◎ to Δ.

  The results obtained as described above are shown in Table 2.

  As is apparent from the results shown in Table 2, the recording medium of the present invention containing a copolymer having an average molecular weight of 500 to 1000 composed of an ethylene oxide chain and an alkylene oxide chain was prepared relative to the comparative example. It can be seen that the viscosity of the applied ink-receiving layer coating solution does not increase excessively and is excellent in coating suitability and cracking resistance and in the uniformity of the printed image.

Claims (6)

In a void-type inkjet recording medium having an ink receiving layer containing inorganic fine particles having an average particle size of 100 nm or less and a hydrophilic resin on a non-water-absorbing support, the ink receiving layer comprises an ethylene oxide chain and an alkylene. An inkjet recording medium comprising a copolymer having an average molecular weight of 500 to 1000 composed of an oxide chain. 2. The ink jet recording medium according to claim 1, wherein an ethylene oxide chain ratio in the copolymer is 40% by mass or less. 2. The ink jet recording medium according to claim 1, wherein an ethylene oxide chain ratio in the copolymer is 5 to 30% by mass. The inkjet copolymer according to any one of claims 1 to 3, wherein the copolymer is a compound represented by the following general formula (1) or (2).
General formula (1)
_{HO (CH 2 CH 2 O)} n (CH 2 CH (CH 3) O) m (CH 2 CH 2 O) k H
General formula (2)
_{HO (CH 2 CH (CH 3} ) O) p (CH 2 CH 2 O) q (CH 2 CH (CH 3) O) r H
[In the formula, n, k, and q each represent a real number of 1 or more and less than 23, and m, p, or r represents a real number of 1 or more and less than 18, respectively. However, 500 ≦ 44 × (n + k) + 58 × m + 18 ≦ 1000 and 500 ≦ 44 × q + 58 × (p + r) + 18 ≦ 1000. ] 5. The inkjet recording medium according to claim 1, wherein the content of the copolymer is 0.5 to 10% by mass of the total mass of the inorganic fine particles. The ink jet recording medium according to claim 1, wherein the inorganic fine particles are vapor phase method silica.