JP2011068105A - Inkjet recording medium and method for producing the same - Google Patents

Abstract

An ink jet recording medium capable of improving scratch resistance and gloss without reducing color density and ink absorbency, and a method for producing the same.
An ink jet recording medium having a support, one or more ink receiving layers provided on the support, and a protective layer provided on the ink receiving layer and containing hollow inorganic particles. The hollow inorganic particles preferably have a particle diameter of 20 nm to 150 nm, and are preferably hollow silica particles.
[Selection figure] None

Description

  The present invention relates to an inkjet recording medium and a manufacturing method thereof.

In recent years, with the rapid development of the information industry, various information processing systems have been developed, and recording methods and apparatuses suitable for the information systems have been developed and put into practical use.
Among the above recording methods, the inkjet recording method is capable of recording on a variety of recording materials, the hardware (device) is relatively inexpensive, compact, and excellent in quietness. Of course, it has been widely used in so-called home use.

In addition, with the recent increase in resolution of inkjet printers, it has become possible to obtain so-called photographic-like high-quality recorded matter. Furthermore, with the development of hardware (device), various ink jet recording media have been developed.
The characteristics required for the ink jet recording medium generally include (1) fast drying (high ink absorption speed) and (2) proper and uniform ink dot diameter (similarity). (3) Good graininess, (4) High roundness of dots, (5) High color density, (6) High saturation (no dullness) ), (7) The light resistance, gas resistance and water resistance of the print area are good, (8) the whiteness of the recording sheet is high, and (9) the storage stability of the recording sheet is good (for long-term storage) (No yellow discoloration, image does not bleed after long-term storage), (10) hard to deform, good dimensional stability (curl is sufficiently small), (11) good hard running There are some things.

In addition to the above properties, glossy, surface smoothness, photographic paper-like texture similar to silver salt photography, etc. can be used for photo glossy paper used for the purpose of obtaining so-called photo-like high-quality recorded matter. Required.
Conventionally, for the purpose of improving scratch resistance and glossiness, various ink jet recording media having a surface layer containing colloidal silica or the like as a protective layer provided on the upper layer of the ink receiving layer have been proposed (for example, Patent Document 1). reference).
The ink receiving layer is a spherical fine powder formed of an inorganic powder containing a hollow inside and an outer shell layer containing silica, and the outer shell layer is a fine porous material having a pore diameter of 5 to 60 nm. An ink jet recording medium containing a hollow filler having a structure has also been proposed (see, for example, Patent Document 2).

JP 2006-263951 A Japanese Patent No. 4165969

However, as in Patent Document 1, although the protective layer mainly composed of colloidal silica improves the glossiness and scratch resistance when the thickness is increased, the ink absorption and color density may be lowered. Further, as in Patent Document 2, even if a hollow filler is contained in the ink receiving layer itself, the glossiness and scratch resistance are difficult to improve, and the ink further includes a hollow filler that is an agglomerated powder in which inorganic powder is aggregated. Regarding the receiving layer, the color density was insufficient for a photo print application.
As described above, in the conventional protective layer, the color density and ink absorbability are likely to be lowered, and it has been impossible to achieve both glossiness and scratch resistance and improvement in color density and ink absorbability.

  An object of the present invention is to provide an ink jet recording medium capable of improving the scratch resistance and glossiness without lowering the color density and ink absorbability.

Specific means for achieving the above object are as follows.
<1> An inkjet recording medium having a support, one or more ink receiving layers provided on the support, and a protective layer provided on the ink receiving layer and including hollow inorganic particles.

  <2> The inkjet recording medium according to <1>, wherein the hollow inorganic particles have a particle size of 20 nm to 150 nm.

  <3> The inkjet recording medium according to <1> or <2>, wherein the protective layer further contains a water-soluble resin.

<4> The inkjet recording medium according to any one of <1> to <3>, wherein a solid content coating amount of the hollow inorganic particles in the protective layer is 0.05 g / m ² to ⁵ g / m ^2. It is.

  <5> The inkjet recording medium according to any one of <1> to <4>, wherein the hollow inorganic particles are hollow silica particles.

  <6> (1) Simultaneously applying an ink receiving layer coating liquid and a protective layer coating liquid containing hollow inorganic particles to form an ink receiving layer and a protective layer, or (2) an ink receiving layer coating liquid At any time during the drying of the ink receiving layer and the protective layer formed by applying the protective layer coating liquid containing hollow inorganic particles, and before the ink receiving layer and the protective layer exhibit a reduced rate drying And a method for producing an ink jet recording medium, wherein a basic solution containing a boron compound is applied to the ink receiving layer and the protective layer.

  According to the present invention, it is possible to provide an ink jet recording medium capable of improving the scratch resistance and the glossiness without reducing the color density and the ink absorbability.

The ink jet recording medium of the present invention has a support, one or more ink receiving layers provided on the support, and a protective layer provided on the ink receiving layer and containing hollow inorganic particles. By setting it as the said structure, scratch resistance and glossiness can further be improved, having the coloring density and ink absorptivity which can be used for a photo use.
The ink jet recording medium of the present invention may further have other layers such as an intermediate layer.
Hereinafter, each component such as a protective layer, an ink receiving layer, and a support constituting the inkjet recording medium of the present invention will be described in detail.

<Protective layer>
The ink jet recording medium of the present invention has a protective layer provided on the ink receiving layer and containing hollow inorganic particles.
In addition to the hollow inorganic particles, the protective layer may contain other components as necessary within a range not impairing the effects of the present invention. First, the hollow inorganic particles will be described.

-Hollow inorganic particles-
The hollow inorganic particle refers to an inorganic material having a space (cavity) inside the particle and the space being closed by a shell. Therefore, inorganic materials having a cave-like space with pores on the particle surface, such as so-called porous pigments, are not included in the hollow inorganic particles in the present invention. The “particle” in the hollow inorganic particle means a primary particle. Therefore, aggregated particles that are aggregates of primary particles and in which a space is formed inside the primary particle group serving as a shell are not included in the hollow inorganic particles in the present invention.

  The shape of the hollow inorganic particles is not particularly limited, and is not necessarily spherical, and may be spherical, disc-shaped, flat, cubic, or indefinite.

  When the protective layer contains hollow inorganic particles, scratch resistance and gloss can be improved. Furthermore, since the amount of voids obtained by aggregation of the hollow inorganic particles is large, and it is considered that the ink solvent is also absorbed inside the hollow inorganic fine particles, the ink absorbability of the ink jet recording medium is reduced. Hateful. In addition, since the hollow inorganic particles have a low refractive index, the transparency of the protective layer is not impaired even if the protective layer is increased in thickness, so that the color density developed by the ink receiving layer is not impaired.

  The inorganic material constituting the hollow inorganic particle is not particularly limited as long as it has a space inside the particle and the space is closed with a shell. However, from the viewpoint of improving scratch resistance, the inorganic material is preferably an inorganic pigment. , Alumina particles, and pseudoboehmite type aluminum hydroxide particles are more preferable, and silica particles are particularly preferable.

The particle diameter of the hollow inorganic particles is preferably 20 nm to 150 nm, and more preferably 80 nm to 130 nm. The particle diameter of the hollow inorganic particles refers to the maximum diameter of the primary particles of the hollow inorganic particles and refers to the average value of the maximum diameters of 100 hollow inorganic particles observed by photographic observation with an electron microscope (TEM).
The shell thickness (shell thickness) of the hollow inorganic particles is preferably 5 nm to 15 nm. The shell thickness of the hollow inorganic particles can also be measured by observing photographs with an electron microscope (TEM).

Further, hollow inorganic particles, stability and ink absorbency of the protective layer coating solution for protective layer formation, from the viewpoint of satisfying all of glossiness, the specific surface area measured by the BET method, 100 m ^2/500 m ² / G is preferred.

  Commercially available products may be used as the hollow inorganic particles. For example, hollow silica particles can be obtained as a hollow nanosilica “SILINAX” manufactured by Nippon Steel Mining Co., Ltd.

In the protective layer, the solid content coating amount of the hollow inorganic particles is preferably ^{0.05g / m 2 ~5g / m 2} , more preferably ^{2g / m 2 ~5g / m 2} . By setting the solid content coating amount of the hollow inorganic particles to 0.05 g / m ² or more, the scratch resistance and glossiness of the ink jet recording medium can be improved, and by setting the coating amount to 5 g / m ² or less, the color density can be reduced. A drop can be suppressed, and an ink jet recording medium suitable for photo applications can be obtained.

(Other particles)
The protective layer may further contain particles other than hollow inorganic particles (hereinafter also referred to as “other particles”). For example, hollow organic particles, organic particles that are not hollow, silica particles that are not hollow, Non-alumina particles, and non-hollow pseudoboehmite type aluminum hydroxide particles.
From the viewpoint of not impairing the effects of the present invention, the content of other particles in the protective layer is preferably 20% by mass or less with respect to the total solid mass of the hollow inorganic particles.

-Other ingredients-
The protective layer preferably further contains a water-soluble resin and a surfactant. Moreover, in the limit which does not impair the effect of this invention, additives, such as a ultraviolet absorber and antioxidant, may be included.

(Water-soluble resin)
From the viewpoint of fixing the hollow inorganic particles contained in the protective layer and facilitating the formation of the protective layer, the protective layer preferably contains a water-soluble resin (hydrophilic binder).
Examples of the water-soluble resin used in the present invention include a polyvinyl alcohol resin (polyvinyl alcohol (PVA), acetoacetyl-modified polyvinyl alcohol, cation-modified polyvinyl alcohol, and anion-modified polyvinyl) that is a resin having a hydroxy group as a hydrophilic structural unit. Alcohol, silanol-modified polyvinyl alcohol, polyvinyl acetal, etc.], cellulosic resins [methyl cellulose (MC), ethyl cellulose (EC), hydroxyethyl cellulose (HEC), carboxymethyl cellulose (CMC), hydroxypropyl cellulose (HPC), hydroxyethyl methyl cellulose, hydroxy Propylmethylcellulose, etc.], chitins, chitosans, starch, resins having an ether bond (polyethylene oxide) PEO), polypropylene oxide (PPO), polyethylene glycol (PEG), polyvinyl ether (PVE), etc.], resins having a carbamoyl group [polyacrylamide (PAAM), polyvinylpyrrolidone (PVP), polyacrylic acid hydrazide, etc.), etc. It is done.
Moreover, the polyacrylic acid salt which has a carboxyl group as a dissociable group, maleic acid resin, alginate, gelatins, etc. can be mentioned.

  Among the above water-soluble resins, the protective layer includes a polyvinyl alcohol resin, a cellulose resin, a resin having an ether bond, a resin having a carbamoyl group, a resin having a carboxy group, and gelatins. It is more preferable to contain at least one selected from

  Among the above, the water-soluble resin is particularly preferably polyvinyl alcohol (PVA). In addition to unmodified polyvinyl alcohol (PVA), the polyvinyl alcohol includes cation-modified PVA, anion-modified PVA, silanol-modified PVA, and other polyvinyl alcohol derivatives. Polyvinyl alcohol may be used alone or in combination of two or more.

As described above, by containing hollow inorganic particles in the protective layer, a protective layer with a large void amount can be obtained, but when the hollow inorganic particles are hollow silica particles, the protective layer contains PVA, Furthermore, the porosity can be increased.
The PVA has a hydroxyl group in its structural unit, but the hydroxyl group of PVA and the silanol group on the surface of the silica particle form a hydrogen bond to form a three-dimensional network structure in which the secondary particle of the silica particle is a chain unit. Make it easy to do. It is considered that a protective layer having a porous structure with a higher porosity can be formed by forming such a three-dimensional network structure.
In the ink jet recording medium obtained according to the present invention, the porous protective layer obtained as described above absorbs ink rapidly by capillary action, and forms dots with good roundness without ink bleeding. Can do.

  The saponification degree of polyvinyl alcohol (PVA) used in the present invention is preferably 75 to 95 mol%, more preferably 77 to 90 mol%, from the viewpoint of the color density of the image formed on the ink receiving layer, and 80 -90 mol% is particularly preferred. Moreover, as a polymerization degree of polyvinyl alcohol (PVA), from a viewpoint of obtaining sufficient film | membrane intensity | strength, 1,400-5,000 are preferable and 2,300-4,000 are more preferable. Polyvinyl alcohol having a polymerization degree of less than 1400 and a polymerization degree of 1400 or more may be used in combination.

As content in the protective layer of water-soluble resin, 30 mass% or less is preferable with respect to the total solid content mass of a protective layer, and 2-20 mass% is more preferable. By setting the amount within the above range, it becomes easy to prevent a decrease in film strength and cracking during drying due to an excessive content of the water-soluble resin in the protective layer, and an excessive content of the water-soluble resin in the protective layer. By this, the voids in the protective layer can be easily blocked by the resin, and the ink absorption can be prevented from being lowered due to the decrease in the void ratio. It may be a mixed system of a plurality of materials.

-Content ratio of hollow inorganic particles and water-soluble resin-
In the protective layer, the content ratio of the hollow inorganic particles and the water-soluble resin [PB ratio; hollow inorganic particle mass (x) in the protective layer / water-soluble resin mass (y) in the protective layer] is the film structure of the protective layer. It also has a big impact. That is, as the PB ratio increases, the porosity, pore volume, and surface area (per unit mass) increase. Specifically, as the PB ratio (x / y), a decrease in film strength and cracking during drying caused by the PB ratio being too large are prevented, and the PB ratio is too small. From the viewpoint of preventing the ink from being reduced due to the void being easily blocked by the resin and the void ratio being decreased, 3/1 to 1000/1 is preferable.

  Since stress may be applied to the recording medium when passing through the conveyance system of the ink jet printer, the protective layer needs to have sufficient scratch resistance for the purpose of protecting the ink receiving layer. Also, from the viewpoint of promptly reaching the ink solvent received by the protective layer to the ink receiving layer, the PB ratio (x / y) of the protective layer is preferably 3/1 or more, and high-speed ink absorbability is ensured by the ink jet printer. From the viewpoint of doing, it is preferably 5/1 or more.

For example, a coating solution in which hollow inorganic particles having an average primary particle size of 150 nm or less and a water-soluble resin are completely dispersed in an aqueous solution with a PB ratio (x / y) of 3/1 to 6/1 is applied onto a support. When the coating layer is applied and the coating layer is dried, a three-dimensional network structure in which the secondary particles of the hollow inorganic particles are chain units is formed, the average pore diameter is 30 nm or less, the porosity is 50% to 80%, the pore ratio A translucent porous film having a volume of 0.5 ml / g or more and a specific surface area of 100 m ² / g or more can be easily formed.

(Surfactant)
The protective layer preferably contains a surfactant, and various known surfactants can be used as the surfactant.
From the viewpoint of improving the liquid viscosity stability of the coating liquid for the protective layer and obtaining a good coated surface, a polyoxyalkylene decyl ether or polyoxyalkylene tridecyl ether surfactant (hereinafter also referred to as “POE surfactant”). Can be used. The decyl group or tridecyl group in the POE surfactant is preferably branched, and from the viewpoint of improving the stability of the coating solution and not causing deterioration of wet heat bleeding, the POE surfactant is nonionic. It is particularly preferred that

The POE surfactant preferably satisfies the following condition (1) or (2). That is,
(1) When the solubility rate with respect to water is 1 mass% or more, the cloud point of 1 mass% aqueous solution is 30 degreeC or more, and HLB value is 10.5 or more.
(2) When the water solubility is less than 1% by mass, the cloud point of a 10% by mass solution in water / diethylene glycol monobutyl ether = 75/25 mixed solvent is 30 ° C. or higher and 80 ° C. or lower, and the HLB value is 10.5 or more and less than 15.

Here, the solubility in water of 1% by mass or more means so-called water solubility, whereas the solubility in water of less than 1% by mass means insoluble in water. It means to show.
In addition, the measurement of the water solubility of the POE surfactant (that is, whether or not it is water-soluble) was carried out by adding 1 g of POE surfactant to 99 g of ion-exchanged water at 23 ° C. The mixture was stirred for 30 minutes, and when it became transparent (determined visually), it was judged to be water-soluble.

(1) When the water solubility is 1% by mass or more (that is, water-soluble) The cloud point is preferably 30 ° C. or higher, more preferably 40 ° C. or higher, and 40 to 70 ° C. It is particularly preferred that When the cloud point is 30 ° C. or higher, the liquid viscosity of the coating solution is unlikely to be high, and a good coated surface shape can be obtained.
Further, the HLB value is preferably 10.5 or more, more preferably 12 to 16, and particularly preferably 13 to 14. When the HLB value is 10.5 or more, repelling hardly occurs and a good coated surface shape is obtained.

(2) When the solubility in water is less than 1% by mass (that is, water-insoluble) The cloud point is preferably 30 ° C. or higher and 80 ° C. or lower, more preferably 60 to 80 ° C., A temperature of 70 to 80 ° C. is particularly preferable. When the cloud point is 30 ° C. or higher, repellency failure is less likely to occur in the coating and drying process, and a good coated surface shape is easily obtained. On the other hand, if the cloud point is within 80 ° C., sufficient viscosity stability of the coating solution can be obtained, and the occurrence of streak failure can be suppressed.
Moreover, it is preferable that HLB value is 10.5 or more and less than 15, Furthermore, it is preferable that it is 11-14, and it is especially preferable that it is 12-13. When the HLB value is 10.5 or more, the occurrence of repellency is suppressed and a good coated surface is obtained. On the other hand, when the HLB value is less than 15, the viscosity of the coating solution is unlikely to increase, and streaks are unlikely to occur during coating.

-Measurement of cloud point-
A POE surfactant has two types of functional groups, a hydrophilic group having a large affinity for water and a hydrophobic group opposite to the hydrophilic group in one molecule. This occurs by hydration of water molecules to the ether oxygen of the oxide chain. The hydration power due to the hydrogen bond becomes weaker as the temperature rises, and when the temperature rises above a certain temperature, the solubility rapidly decreases and precipitation starts, resulting in cloudiness. This inherent temperature of clouding is called the cloud point.
The cloud point in the present invention is measured by visually confirming the temperature at which the aqueous surfactant solution becomes cloudy. In addition, since it is necessary to perform measurement in a state in which the POE surfactant is dissolved, the solvent is changed according to the solubility in water. Specifically, for those having a solubility of 1% by mass or more in water (water-soluble), the measurement is performed with a 1% by mass aqueous solution, while the solubility in water is less than 1% by mass ( For water-insoluble ones, a mixed solvent of diethylene glycol monobutyl ether / water = 25/75 is used and a 10% by mass solution of each POE surfactant is prepared and measured.
Here, specific examples of the water-soluble POE surfactant include Neugen XL-100, Neugen SD-60, Neugen SD-70, Neugen SD-110, Neugen XL-100, Emulgen 109P, Neugen ET106A, and the like. be able to. On the other hand, examples of the water-insoluble surfactant include Neugen TDS-70, Neugen SD-30, Neugen XL-60, Neugen SD-30 and the like.

-Calculation of HLB value-
The HLB value is 20 for a hypothetical compound having an infinitely long hydrophilic group added to the lipophilic group of the POE surfactant and having the largest hydrophilic property, and 0 for a lipophilic compound having no hydrophilic group. It is a value that is calculated for each POE surfactant as a relative value, and can be generally calculated by the Griffin equation.
The Griffin equation used for calculating the HLB value is shown below.
When the molecular weight of the nonionic surfactant is M and the molecular weight of the hydrophilic portion is Mw,
HLB value = 20 × Mw / M

The alkylene group in the POE surfactant of the polyoxyalkylene decyl ether or polyoxyalkylene tridecyl ether is particularly preferably an ethylene group.
Preferable specific examples of the POE surfactant in the present invention include polyoxyethylene isodecyl ether and polyoxyethylene tridecyl ether, and polyoxyethylene isodecyl ether is more preferable.

The content (solid content) of the surfactant in the protective layer is 0 with respect to the coating liquid mass for the protective layer from the viewpoint of application failure during the application of the coating liquid for the protective layer, and suppression of coating failure such as streaks and blisters. 0.005 to 0.3% by mass is preferable, and 0.01 to 0.1% by mass is more preferable.
In addition, when a polyoxyalkylene decyl ether surfactant or a polyoxyalkylene tridecyl ether surfactant is used as the surfactant, the content (solid content) is a viewpoint that makes the liquid viscosity a desired low viscosity. Therefore, the content is preferably 1 to 50% by mass, and more preferably 2 to 30% by mass with respect to the fine particles.

<Ink receiving layer>
The ink jet recording medium of the present invention has one or more ink receiving layers provided on a support.
The constituent components of the ink receiving layer are not particularly limited, but preferably contain fine particles and a water-soluble resin from the viewpoint of forming an image having high ink absorptivity and excellent color density. Further, if necessary, it may contain a water-soluble polyvalent metal salt, a crosslinking agent, a surfactant and the like.

(Fine particles)
The ink receiving layer in the invention preferably contains fine particles.
Examples of the fine particles contained in the ink receiving layer include at least one kind of fine particles selected from organic fine particles, silica fine particles, alumina fine particles, and pseudoboehmite type aluminum hydroxide fine particles. Among these, silica fine particles, alumina fine particles, and pseudo boehmite type aluminum hydroxide fine particles are preferable.

  The fine particles in the present invention preferably have an average primary particle diameter of 50 nm or less, more preferably 30 nm or less, and particularly preferably 15 nm or less. When the average primary particle diameter of the fine particles is 50 nm or less, the ink absorption characteristics can be effectively improved, and at the same time, the glossiness of the ink receiving layer surface can be improved. The lower limit of the average primary particle diameter of the fine particles is not particularly limited, but is preferably 1 nm or more.

  Among the above-mentioned fine particles, vapor-phase method silica or vapor-phase method alumina produced by the vapor phase method has a particularly large specific surface area, and therefore has high ink absorption and retention efficiency, and has a low refractive index. If the dispersion is performed up to a small particle size, transparency can be imparted to the ink receiving layer, and there is an advantage that high color density and good color developability can be obtained. Thus, the fact that the receiving layer is transparent means that not only for applications that require transparency, such as OHP, but also when applied to recording sheets such as photo glossy paper, a high color density and good color developability and This is important from the viewpoint of obtaining glossiness.

  In particular, the silica fine particle has a silanol group on the surface thereof, and the particles are likely to adhere to each other by hydrogen bonding of the silanol group, and because of the adhesion effect between the particles via the silanol group and the water-soluble resin, As described above, when the average primary particle diameter is 15 nm or less, the ink receiving layer has a high porosity and a highly transparent structure can be formed, and the ink absorption characteristics can be effectively improved.

  In general, silica fine particles are generally roughly classified into wet method (precipitation method) particles and dry method (gas phase method) particles according to the production method. In the above wet method, a method is mainly used in which activated silica is produced by acid decomposition of a silicate, and this is appropriately polymerized and agglomerated and precipitated to obtain hydrous silica. On the other hand, the gas phase method is a method by high-temperature gas phase hydrolysis of silicon halide (flame hydrolysis method), a method in which silica sand and coke are heated and reduced by an arc in an electric furnace and oxidized with air. The method of obtaining anhydrous silica by the (arc method) is the mainstream, and the “gas phase method silica” refers to anhydrous silica fine particles obtained by the gas phase method.

Vapor phase method silica is different from the above hydrous silica in the density of silanol groups on the surface, the presence or absence of vacancies, etc., and shows different properties, but is suitable for forming a three-dimensional structure with high porosity. The reason for this is not clear, but in the case of hydrous silica, the density of silanol groups on the surface of the fine particles is as high as 5 to 8 / nm ^2, and the silica fine particles tend to aggregate (aggregate) easily, In the case of the method silica, the density of silanol groups on the surface of the fine particles is as small as ² to 3 / nm ² , so that it becomes sparse soft agglomeration (flocculate), and as a result, it is estimated that the structure has a high porosity. The

The fine particles in the present invention are preferably amorphous silica or alumina synthesized by a sedimentation method or a gas phase method. In particular, it is preferable to use gas phase method silica or gas phase method alumina having an average primary particle size of 30 nm or less, and the gas phase method silica or gas phase method alumina is 50% by mass or more (preferably 70% by mass or more) of all fine particles. , More preferably 90% by mass or more), a remarkable effect is obtained. In the case of vapor phase method silica, silica fine particles having a density of silanol groups on the fine particle surface of 2 to 3 / nm ² are preferred.

  In the present invention, vapor-phase process alumina has a feature that it has a higher color density and higher gloss than gas-phase process silica. This is presumably because the refractive index of vapor-phase method alumina is higher than that of vapor-phase method silica and the reflection of light on the surface is strong. Vapor phase alumina has the characteristics of spherical particles and excellent ink absorbency compared to alumina hydrate such as pseudoboehmite, and further improves ink absorbency when combined with the present invention. It becomes possible to make it. Although the reason is not clear, vapor-phase method alumina has a feature that microcracks of the ink receiving layer are less likely to occur compared to vapor-phase method silica. Such micro cracks are caused by various factors in the manufacturing process, but when combined with vapor phase alumina, for example, the micro cracks caused by shrinkage of the coating during the drying process are greatly improved. It becomes possible to do.

  In addition, when vapor-phase process alumina is used, the strength of the coating film tends to be higher than when vapor-phase process silica is used, and failure such as scratches is less likely to occur. Furthermore, it is possible to increase the solid content of the pigment dispersion compared to gas phase method silica, so it is possible to increase the solid content of the final coating liquid, and the production with low drying load and high productivity. It also has the advantage that it can be manufactured by the method. When preparing an aqueous dispersion of vapor-phase process alumina, the use of a small amount of an acidic component can further increase the dispersed solid content. As such an acidic component, it is particularly preferable to add a small amount of boric acid when dispersing the pigment.

  In order to increase the inorganic fine particle dispersion concentration, it is preferable to use a known dispersant. As these dispersants, for example, a cationic polymer having a secondary, tertiary amino group, or quaternary ammonium base, a nonionic or cationic surfactant, and a low molecular weight polyvinyl alcohol are preferably used in combination. .

When vapor phase alumina is used as the fine particles, the preferred amount is 4 to 12 parts by weight, more preferably 5 to 10 parts by weight, and particularly preferably 6 parts by weight with respect to 1 part by weight of the water-soluble resin. It is -9 mass parts, and it becomes possible to obtain sufficient film | membrane intensity | strength with a small quantity of water-soluble resin than the case where vapor-phase-method silica is used.
In the case of an ink-receiving layer having a multilayer structure, it is preferable to include vapor-phase alumina in the outermost layer in order to bring out the characteristics of the vapor-phase alumina.

It is also preferable to use colloidal silica as the fine particles.
Colloidal silica has a large number of hydroxyl groups on the surface, and ultrafine silica particles with a particle diameter of 1 to 500 nm, which constitutes a siloxane bond (-Si-O-Si-) inside, are dispersed in water or a polar solvent. Is. Specifically, it is described in Chapter 4 and Chapter 5 of “Applied Technology of High-Purity Silica” supervised by Toshiro Kaga and Hayashi Hayashi, Chapter 3 of CMC Co., Ltd. (1991). Further, for example, it is commercially available from Nissan Chemical Industries, Ltd. as Snowtex, and from Catalytic Chemical Industries, Ltd. as cataloid.

  However, when colloidal silica is used, it is difficult to form an ink receiving layer having a porous structure with a high porosity due to the small void forming ability of the colloidal silica itself. By simultaneously using silica and colloidal silica in the same layer, or by providing a colloidal silica-containing layer as a multilayer, a high void forming effect can be obtained.

When using fumed silica correlates with the measured specific surface area in the primary particle diameter is almost the BET method, BET specific surface area ^is preferably a 100m ² / g~400m 2 / g, the coating solution From the viewpoint of satisfying all of stability, ink absorbability, and glossiness, a BET specific surface area of 300 to 350 m ² / g is particularly preferable.

The colloidal silica used in the ink receiving layer may be a commercially available product as described above, and the content of the colloidal silica in the ink receiving layer is preferably 0.1 to 3 g / m ^2. More preferably, it is ² to 1 g / m ² .

  If organic fine particles are used as the fine particles in the present invention, they must be present in the form of particles when the ink receiving layer is formed. Examples of the organic fine particles include polymer fine particles obtained by emulsion polymerization, microemulsion polymerization, soap-free polymerization, seed polymerization, dispersion polymerization, suspension polymerization, and the like. Specifically, polyethylene, polypropylene, polystyrene, Examples include polyacrylate, polyamide, silicon resin, phenol resin, natural polymer powder, latex or emulsion polymer fine particles, and the like. The organic fine particles preferably have a cationized surface. The Tg of the organic fine particles is not particularly limited, but when used alone, it is preferably 40 ° C. or higher, more preferably 80 ° C. or higher.

  In the present invention, the fine particles may be used alone or in combination of two or more. When two or more kinds of fine particles are used in combination, a mode in which precipitation method silica, gas phase method silica, and gas phase method alumina are optionally used in combination is preferable.

(Water-soluble resin)
In order to make the ink receiving layer have a porous structure, the ink receiving layer preferably contains a water-soluble resin (hydrophilic binder).
As the water-soluble resin, the water-soluble resin described as a component that can be included in the protective layer can be used. The preferable range of the water-soluble resin is the same as that of the water-soluble resin described as a component that can be included in the protective layer, and it is preferable to use polyvinyl alcohol (PVA).

  The saponification degree and polymerization degree of polyvinyl alcohol (PVA) used in the present invention are the same as the saponification degree and polymerization degree of polyvinyl alcohol (PVA) described as components that can be included in the protective layer, and the preferred ranges are also the same. is there.

As the content of the water-soluble resin in the ink receiving layer, the film strength is prevented from being lowered and cracking at the time of drying due to the insufficient content, and the void is blocked by the resin due to the excessive content. From the viewpoint of preventing the ink absorbency from being lowered by decreasing the porosity, the content is preferably 5 to 40% by mass with respect to the total solid content contained in the ink receiving layer, and 10 to 30%. The mass% is more preferable.
Note that the fine particles and the water-soluble resin mainly constituting the ink receiving layer may be a single material or a mixed system of a plurality of materials.

-Content ratio of fine particles and water-soluble resin-
Content ratio of fine particles (preferably silica fine particles) and water-soluble resin (y) in the ink-receiving layer [PB ratio; fine particle mass in ink-receiving layer (x) / water-soluble resin mass in ink-receiving layer (y) ] Greatly affects the film structure of the ink receiving layer. That is, as the PB ratio increases, the porosity, pore volume, and surface area (per unit mass) increase. Specifically, as the PB ratio (x / y), a decrease in film strength and cracking during drying caused by the PB ratio being too large are prevented, and the PB ratio is too small. From the viewpoint of preventing the gap from being easily blocked by the resin and preventing the ink absorbability from being lowered due to a decrease in the void ratio, 1.5 / 1 to 10/1 is preferable.

  As described above, stress may be applied to the recording medium when passing through the conveyance system of the ink jet printer. The ink jet recording medium of the present invention has a protective layer for protecting the ink receiving layer on the ink receiving layer, but the ink receiving layer preferably has sufficient film strength. Furthermore, when the ink jet recording medium is cut into a sheet, it is preferable that the ink receiving layer has sufficient film strength to prevent cracking and peeling of the ink receiving layer. From such a viewpoint, the PB ratio (x / y) is preferably 6/1 or less, and preferably 3/1 or more from the viewpoint of securing high-speed ink absorbability with an inkjet printer.

For example, a coating solution in which anhydrous silica fine particles having an average primary particle size of 20 nm or less and a water-soluble resin are completely dispersed in an aqueous solution with a PB ratio (x / y) of 3/1 to 6/1 is coated on a support. When the coating layer is dried, a three-dimensional network structure in which the secondary particles of silica fine particles are chain units is formed, the average pore diameter is 30 nm or less, the porosity is 50% to 80%, and the pore specific volume is 0. A translucent porous film having a surface area of 5 ml / g or more and a specific surface area of 100 m ² / g or more can be easily formed.

(Other ingredients)
In addition to the above components, the ink receiving layer in the invention may contain other components such as a surfactant, latex, cationic substance, water-soluble polyvalent metal salt, and crosslinking agent.

-Surfactant-
The ink receiving layer may contain a surfactant.
As the surfactant, a surfactant that can be contained in the protective layer can be used, and the preferable ranges (kind, cloud point, HLB value) of the surfactant are also the same.

The content (solid content) of the surfactant in the ink receiving layer is determined by the mass of the coating liquid for the ink receiving layer from the standpoint of application failure during application of the coating liquid for the ink receiving layer, and the suppression of coating failures such as streaks and irregularities. It is preferable that it is 0.005-0.3 mass% with respect to it, and it is more preferable that it is 0.01-0.1 mass%.
In addition, when a polyoxyalkylene decyl ether surfactant or a polyoxyalkylene tridecyl ether surfactant is used as the surfactant, the content (solid content) is a viewpoint that makes the liquid viscosity a desired low viscosity. Therefore, the content is preferably 1 to 50% by mass, and more preferably 2 to 30% by mass with respect to the fine particles.

-Latex-
A surfactant of polyoxyalkylene decyl ether or polyoxyalkylene tridecyl ether that can be used in the ink-receiving layer may reduce the strength of the film or worsen the wet heat blur after printing. When these surfactants are used, it is preferable to use latex in combination. By using latex together, the occurrence of bleeding can be improved more favorably.

The particle diameter of the latex in water is preferably 1 μm or less, more preferably 1 to 100 nm.
Latex includes polystyrene, styrene-butadiene copolymer, acrylonitrile-butadiene, acrylic acid, styrene-acrylic, urethane, methacrylic acid, vinyl chloride, vinyl acetate, ethylene-vinyl acetate latex, etc. Preferably used. Among these, styrene, acrylic acid, methacrylic acid, and urethane latex are preferable, and urethane latex and aqueous dispersion are particularly preferable. These latexes or aqueous dispersions were synthesized by a known polymerization method as described in “Latest Emulsion Application Technology (edited by Motoharu Okikura, Chunichisha, 1991, pp. 88-90)”. Can be used.
The latex is preferably a polyurethane latex having a dispersed particle size of 1 μm or less, preferably 100 nm or less, polymerized and synthesized in a soap-free manner, and most preferably cation-modified.

  The Tg of the latex is not particularly limited, but is preferably 40 ° C. or higher from the viewpoint of improving the strength of the film, and conversely, it is preferably 40 ° C. or lower from the viewpoint of the brittleness improving effect. The cationized polyurethane dispersion is preferably present in the form of a film rather than particles after coating and drying. By forming a film, the haze of the image receiving layer is lowered, and a high color density can be obtained.

The latex resin in the present invention is a colloidal dispersion containing a cationic urethane resin having a volume average particle size of 30 nm or less, and the glass transition temperature of the cationic urethane resin is from the viewpoint of obtaining such a gloss for photographic use. Those having a temperature of less than 50 ° C are particularly preferred.
When such a colloidal dispersion-like latex resin is used, the viscosity of the coating liquid tends to be promoted by the surfactant, and in particular, the polyoxyalkylene decyl ether or polyoxyalkylene tridecyl ether interface in the present invention. The effect of using the activator is remarkably exhibited.

-Cationic substance-
The ink receiving layer may further contain a cationic substance.
As the cationic substance, the above-described cation-modified latex is preferably used, and other cationic polymers can also be used. As the other cationic polymer, a polymer mordant having a primary to tertiary amino group or a quaternary ammonium base as a cationic group is preferably used, but a cationic non-polymer mordant should also be used. Can do.

Examples of the cationic polymer include a homopolymer of a monomer having a primary to tertiary amino group and a salt thereof, or a quaternary ammonium base (mordanting monomer), and the mordanting monomer and other monomers (hereinafter referred to as “mordant monomer”). , "Non-mordant monomer") and a copolymer obtained by condensation or condensation.
As the cationic polymer, a cationic polymer having a weight average molecular weight of 200,000 or less and an I / O value of 3.0 or less is particularly preferable from the viewpoint of preventing bleeding with time.

The other cationic polymer mentioned above may be used individually by 1 type, and may use 2 or more types together. Moreover, you may use together another cationic polymer, another organic mordant, and / or an inorganic mordant.
The content of the cationic substance in the ink receiving layer is preferably 1 to 30% by mass, more preferably 2 to 15% by mass, and further preferably 3 to 10% by mass with respect to the total solid content mass of the ink receiving layer. .

-Water-soluble polyvalent metal salt-
The ink receiving layer may contain a water-soluble polyvalent metal salt.
Examples of the water-soluble polyvalent metal salt include water-soluble salts of metals selected from calcium, barium, manganese, copper, cobalt, nickel, aluminum, iron, zinc, zirconium, chromium, magnesium, tungsten, and molybdenum.
Specifically, calcium acetate, calcium chloride, calcium formate, calcium sulfate, barium acetate, barium sulfate, barium phosphate, manganese chloride, manganese acetate, manganese formate dihydrate, manganese ammonium sulfate hexahydrate, chloride chloride Dicopper, ammonium copper (II) chloride dihydrate, copper sulfate, cobalt chloride, cobalt thiocyanate, cobalt sulfate, nickel sulfate hexahydrate, nickel chloride hexahydrate, nickel acetate tetrahydrate, nickel sulfate Ammonium hexahydrate, nickel amidosulfate tetrahydrate, aluminum sulfate, aluminum sulfite, aluminum thiosulfate, polyaluminum chloride, aluminum nitrate nonahydrate, aluminum chloride hexahydrate, ferrous bromide, ferric chloride Ferrous, ferric chloride, ferrous sulfate, ferric sulfate, zinc bromide, zinc chloride, zinc nitrate hexahydrate , Zinc sulfate, zirconium acetate, zirconium chloride, zirconium chloride octahydrate, hydroxy zirconium chloride, chromium acetate, chromium sulfate, magnesium sulfate, magnesium chloride hexahydrate, magnesium citrate nonahydrate, sodium phosphotungstate Sodium tungsten citrate, 12 tungstophosphoric acid n hydrate, 12 tungstosilicic acid 26 hydrate, molybdenum chloride, 12 molybdophosphoric acid n hydrate, and the like.

  The water-soluble polyvalent metal salt is preferably at least one selected from water-soluble aluminum compounds, zirconium compounds and titanium compounds.

  As an aluminum compound, for example, as an inorganic salt, aluminum chloride or a hydrate thereof, aluminum sulfate or a hydrate thereof, ammonium alum and the like are known. Furthermore, there is a basic polyaluminum hydroxide compound which is an inorganic aluminum-containing cationic polymer. In particular, a basic polyaluminum hydroxide compound is preferable.

The basic polyaluminum hydroxide compound is represented by the following formula 1, 2 or 3, and for example, [Al ₆ (OH) ₁₅ ] ³⁺ , [Al ₈ (OH) ₂₀ ] ⁴⁺ , [Al ₁₃ ( OH) ₃₄ ] ⁵⁺ , [Al ₂₁ (OH) ₆₀ ] ³⁺ , and the like, which are water-soluble polyaluminum hydroxides that stably contain basic and high-molecular polynuclear condensed ions.

[Al ₂ (OH) _n Cl _6-n ] _m Formula 1
[Al (OH) ₃ ] _n AlCl ₃ Formula 2
Al _n (OH) _m Cl _(3n-m) (0 <m <3n) Formula 3

  These are water treatment agents under the name of polyaluminum chloride (PAC) from Taki Chemical Co., Ltd., and polyaluminum hydroxide (Paho) from Asada Chemical Co., Ltd. It is also marketed for the same purpose from other manufacturers, and various grades are readily available. In the present invention, these commercially available products can be used as they are, but there are also products having an inappropriately low pH, and in that case, the pH can be appropriately adjusted and used.

  The zirconium compound is not particularly limited and various compounds can be used. For example, zirconyl acetate, zirconium chloride, zirconium oxychloride, hydroxy zirconium chloride, zirconium nitrate, basic zirconium carbonate, zirconium hydroxide, zirconium carbonate / ammonium, Zirconium carbonate / potassium, zirconium sulfate, zirconium fluoride compounds and the like can be mentioned. Zirconyl acetate is particularly preferable.

  Although it does not specifically limit as a titanium compound and various compounds can be used, For example, titanium chloride and titanium sulfate are mentioned.

  Some of these compounds have an inappropriately low pH. In that case, the pH can be appropriately adjusted and used. In the present invention, the term “water-soluble” means that 1% by mass or more dissolves in water at room temperature and normal pressure.

In the present invention, when a water-soluble polyvalent metal salt is used, it is particularly preferable that at least one of them is zirconyl acetate from the viewpoint of imparting a bleeding suppression effect to a wider range of dyes. The content of zirconyl acetate in the ink receiving layer, is preferably 0.3 g / ^{m 2} or less, 0.01~0.02g / ^{m 2} is more preferable.

  When zirconyl acetate is used, it is preferable from the viewpoint of viscosity stability of the coating solution that zirconyl acetate is previously contained in the fine particle dispersion, and then the dispersion and binder are mixed. More preferably, the dispersion treatment is performed in the presence of zirconyl acetate in advance in the liquid containing the fine particles before the dispersion treatment.

In the present invention, the content of the water-soluble polyvalent metal salt in the ink receiving layer is preferably 0.1 to 20% by mass, more preferably 1 to 10% by mass, based on the total mass of the fine particles in the ink receiving layer. It is.
Although the water-soluble polyvalent metal salt can be used alone, it is preferable to use two or more kinds in combination.

-Crosslinking agent-
The ink receiving layer may further contain a crosslinking agent capable of crosslinking the water-soluble resin.
In particular, an embodiment having a porous structure in which the water-soluble resin is cured by a crosslinking reaction with a crosslinking agent capable of crosslinking the fine particles and the water-soluble resin is preferable.

As the cross-linking agent, a suitable one may be selected as appropriate in relation to the water-soluble resin contained in the ink receiving layer, and among them, a boron compound is preferable in that the cross-linking reaction is rapid. Examples of the boron compound include borax, boric acid, borate (for example, orthoborate, InBO ₃ , ScBO ₃ , YBO ₃ , LaBO ₃ , Mg ₃ (BO ₃ ) ₂ , Co ₃ (BO ₃ ) ₂ , diboric acid. Salt (eg, Mg ₂ B ₂ O ₅ , Co ₂ B ₂ O ₅ ), metaborate (eg, LiBO ₂ , Ca (BO ₂ ) ₂ , NaBO ₂ , KBO ₂ ), tetraborate (eg, Na ₂ B ₄ O ₇ · 10H ₂ O), pentaborate (for example, KB ₅ O ₈ · 4H ₂ O, Ca ₂ B ₆ O ₁₁ · 7H ₂ O, CsB ₅ O ₅ ), etc. Borax, boric acid and borates are preferred in that a crosslinking reaction can be rapidly caused, and boric acid is particularly preferred, and it is most preferred to use this in combination with polyvinyl alcohol which is a water-soluble resin.

  The crosslinking agent is preferably contained in an amount of 0.05 to 0.50 parts by mass, and 0.08 to 0.30 parts by mass with respect to 1.0 part by mass of the water-soluble resin contained in the ink receiving layer. It is more preferable. When the content of the crosslinking agent is within the above range, the water-soluble resin can be effectively crosslinked to prevent cracks and the like.

When gelatin is used as the water-soluble resin, the following compounds other than boron compounds can also be used as a crosslinking agent.
For example, aldehyde compounds such as formaldehyde, glyoxal and glutaraldehyde; ketone compounds such as diacetyl and cyclopentanedione; bis (2-chloroethylurea) -2-hydroxy-4,6-dichloro-1,3,5- Active halogen compounds such as triazine and 2,4-dichloro-6-S-triazine sodium salt; divinylsulfonic acid, 1,3-vinylsulfonyl-2-propanol, N, N′-ethylenebis (vinylsulfonylacetamide) ), Active vinyl compounds such as 1,3,5-triacryloyl-hexahydro-S-triazine; N-methylol compounds such as dimethylolurea and methyloldimethylhydantoin; melamine resins (for example, methylolmelamine, alkylated methylolmelamine) ;Epoxy resin;

  Isocyanate compounds such as 1,6-hexamethylene diisocyanate; aziridine compounds described in US Pat. Nos. 3,017,280 and 2,983611; carboximide compounds described in US Pat. No. 3,100,704; glycerol triglycidyl Epoxy compounds such as ether; Ethyleneimino compounds such as 1,6-hexamethylene-N, N′-bisethyleneurea; Halogenated carboxaldehyde compounds such as mucochloric acid and mucophenoxycyclolic acid; 2,3-dihydroxy Dioxane compounds such as dioxane; Titanium lactate, aluminum sulfate, chromium alum, potassium alum, metal-containing compounds such as zirconyl acetate and chromium acetate, polyamine compounds such as tetraethylenepentamine, hydrazide compounds such as adipic acid dihydrazide It is a small molecule or polymer or the like containing an oxazoline group two or more. The above crosslinking agents may be used alone or in combination of two or more.

  In the present invention, the cross-linking agent may be added to the ink-receiving layer coating solution and / or the coating solution for forming the adjacent layer of the ink-receiving layer when forming the ink-receiving layer, or the cross-linking agent in advance. The ink receiving layer coating liquid is coated on the support coated with the coating liquid or the ink receiving layer coating liquid containing no cross-linking agent is coated and dried, and then the cross-linking agent solution is overcoated. A crosslinking agent can be supplied to the layer. From the viewpoint of production efficiency, it is preferable to add a cross-linking agent to the ink receiving layer coating solution or the coating solution for forming the adjacent layer, and to supply the cross-linking agent simultaneously with the formation of the ink receiving layer. In particular, it is preferably contained in the ink-receiving layer coating solution from the viewpoint of improving the image printing density and glossiness. Further, the concentration of the crosslinking agent in the ink receiving layer coating solution is preferably 0.05 to 10% by mass, and more preferably 0.1 to 7% by mass.

-Other ingredients-
The ink receiving layer in the invention is constituted by containing the following components as required.
That is, for the purpose of suppressing the deterioration of the ink coloring material, various ultraviolet absorbers, antioxidants, anti-fading agents such as singlet oxygen quenchers may be included.
Examples of the ultraviolet absorber include cinnamic acid derivatives, benzophenone derivatives, benzotriazolylphenol derivatives, and the like. For example, α-cyano-phenyl cinnamate butyl, o-benzotriazole phenol, o-benzotriazole-p-chlorophenol, o-benzotriazole-2,4-di-t-butylphenol, o-benzotriazole-2,4 -Di-t-octylphenol etc. are mentioned. A hindered phenol compound can also be used as an ultraviolet absorber, and specifically, a phenol derivative in which one or more of at least 2-position or 6-position is substituted with a branched alkyl group is preferable.

  Moreover, a benzotriazole type ultraviolet absorber, a salicylic acid type ultraviolet absorber, a cyanoacrylate type ultraviolet absorber, an oxalic acid anilide type ultraviolet absorber, etc. can be used. For example, JP-A-47-10537, 58-111942, 58-21284, 59-19945, 59-46646, 59-109055, 63-53544. No. 36, Japanese Patent Publication No. 36-10466, No. 42-26187, No. 48-30492, No. 48-31255, No. 48-41572, No. 48-54965, No. 50-10726. No. 2,719,086, US Pat. No. 3,707,375, US Pat. No. 3,754,919, US Pat. No. 4,220,711, and the like. .

  A fluorescent brightening agent can also be used as an ultraviolet absorber, and examples thereof include a coumarin fluorescent brightening agent. Specifically, it is described in Japanese Patent Publication Nos. 45-4699 and 54-5324.

  Examples of the antioxidant (fading preventing agent) include European Patent Nos. 223739, 309401, 309402, 310551, 310552, 457416, and German Patent No. 3435443. JP-A-54-48535, JP-A-60-107384, JP-A-60-107383, JP-A-60-125470, JP-A-60-125471, JP-A-60-125472, JP-A-60-. No. 287485, No. 60-287486, No. 60-287487, No. 60-287488, No. 61-160287, No. 61-185483, No. 61-2111079, No. 62-146678. Gazette, 62-146680 gazette, 62-146679 gazette. Gazette, 62-282858 gazette, 62-262417 gazette, 63-051174 gazette, 63-898877 gazette, 63-88380 gazette, 66-88381 gazette, 63-113536 gazette. ;

  JP-A-63-163351, JP-A-63-203372, JP-A-63-224989, JP-A-63-251282, JP-A-63-267594, JP-A-63-182484, JP-A-1-239282, JP-A-2-262654, JP-A-2-71262, JP-A-3-121449, JP-A-4-291865, JP-A-4-291684, JP-A-5-61166, JP-A-5-119449, 5-188687, 5-188686, 5-110490, 5-110437, 5-170361, JP-A 48-43295, 48-33212, US Those described in Japanese Patent Nos. 4814262 and 4980275 are exemplified.

  Specifically, 6-ethoxy-1-phenyl-2,2,4-trimethyl-1,2-dihydroquinoline, 6-ethoxy-1-octyl-2,2,4-trimethyl-1,2-dihydroquinoline 6-ethoxy-1-phenyl-2,2,4-trimethyl-1,2,3,4-tetrahydroquinoline, 6-ethoxy-1-octyl-2,2,4-trimethyl-1,2,3 4, -tetrahydroquinoline, nickel cyclohexane acid, 2,2-bis (4-hydroxyphenyl) propane, 1,1-bis (4-hydroxyphenyl) -2-ethylhexane, 2-methyl-4-methoxy-diphenylamine, Examples include 1-methyl-2-phenylindole.

  These antioxidants (fading preventing agents) may be used alone or in combination of two or more. Antioxidants (antifading agents) may be water-solubilized, dispersed, emulsified, or included in microcapsules. The amount of the antioxidant (fading inhibitor) is preferably 0.01 to 10% by mass with respect to the total mass of the ink receiving layer coating solution.

  The ink receiving layer may contain a high-boiling organic solvent for preventing curling. The high-boiling organic solvent is preferably water-soluble, and examples of the water-soluble high-boiling organic solvent include ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, glycerin, diethylene glycol monobutyl ether (DEGMBE), and triethylene. Glycol monobutyl ether, glycerin monomethyl ether, 1,2,3-butanetriol, 1,2,4-butanetriol, 1,2,4-pentanetriol, 1,2,6-hexanetriol, thiodiglycol, triethanol Examples include alcohols such as amines and polyethylene glycol (weight average molecular weight of 400 or less). Diethylene glycol monobutyl ether (DEGMBE) is preferred.

The content of the high-boiling organic solvent in the ink-receiving layer coating solution is preferably 0.05 to 1% by mass, particularly preferably 0.1 to 0.6% by mass.
In addition, for the purpose of improving the dispersibility of the inorganic pigment fine particles, various inorganic salts, pH adjusting agents, and the like may contain acids and alkalis.

  Further, for the purpose of suppressing surface frictional charge and peeling charge, the metal oxide fine particles having electronic conductivity may contain various matting agents for the purpose of reducing the surface frictional characteristics.

<Support>
As the support applied to the present invention, either a transparent support made of a transparent material such as plastic or an opaque support made of an opaque material such as paper can be used. In order to make use of the transparency of the ink receiving layer, it is preferable to use a transparent support or a highly glossy opaque support. In addition, a read-only optical disk such as a CD-ROM or DVD-ROM, a write-once optical disk such as a CD-R or DVD-R, or a rewritable optical disk is used as a support, and an ink receiving layer is provided on the label surface side. You can also.

As a material that can be used for the transparent support, a material that is transparent and can withstand radiant heat when used in an OHP or a backlight display is preferable. Examples of such materials include polyesters such as polyethylene terephthalate (PET); polysulfone, polyphenylene oxide, polyimide, polycarbonate, polyamide, and the like. Of these, polyesters are preferable, and polyethylene terephthalate is particularly preferable.
Although there is no restriction | limiting in particular as thickness of the said transparent support body, 50-200 micrometers is preferable at the point of the ease of handling.

  As the highly glossy opaque support, one having a glossiness of 40% or more on the surface on which the ink receiving layer is provided is preferable. The glossiness is a value determined according to the method described in JIS P-8142 (75-degree specular gloss test method for paper and paperboard). Specifically, the following supports are mentioned.

For example, high gloss paper support such as art paper, coated paper, cast coated paper, baryta paper used for silver salt photographic support, etc .; polyesters such as polyethylene terephthalate (PET), nitrocellulose, cellulose acetate , Cellulose esters such as cellulose acetate butyrate, and plastic films such as polysulfone, polyphenylene oxide, polyimide, polycarbonate, and polyamide are made opaque by adding a white pigment or the like (surface calendering may be applied). Glossy film; or a support in which a polyolefin coating layer containing or not containing a white pigment is provided on the surface of a highly glossy film containing the various paper supports, the transparent support or the white pigment. Etc.
A white pigment-containing foamed polyester film (for example, foamed PET containing polyolefin fine particles and forming voids by stretching) can also be suitably exemplified. Furthermore, resin-coated paper used for silver salt photographic printing paper is also suitable.

Although there is no restriction | limiting in particular also about the thickness of an opaque support body, 50-300 micrometers is preferable at the point of the ease of handling.
In addition, it is preferable to use a surface of the support that has been subjected to corona discharge treatment, glow discharge treatment, flame treatment, ultraviolet irradiation treatment or the like in order to improve wettability and adhesion.

Next, a base paper used for a paper support such as resin-coated paper will be described.
The base paper is made from wood pulp as a main raw material and, if necessary, paper using synthetic pulp such as polypropylene or synthetic fibers such as nylon or polyester in addition to wood pulp. As the 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. preferable. However, the ratio of LBSP and / or LDP is preferably 10% by mass to 70% by mass.

As the above-mentioned pulp, chemical pulp (sulfate pulp or sulfite pulp) with few impurities is suitably used, and a pulp whose whiteness is improved by performing a bleaching treatment 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 a 24 mesh residual mass% and a 42 mesh residual as defined in JIS P-8207. 30 to 70% of the sum with the mass% of is preferable. The 4 mesh residue is preferably 20% by mass or less.

The basis weight of the base paper is preferably 30 to 250 g, and 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 / m 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. As the surface sizing agent, a sizing agent similar to the size that can be added to the base paper can be used.
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 covering 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, etc. can also be used. In addition, the aspect which used the hydrotalcite compound as a catalyst deactivator of the catalyst of a high density polyethylene is preferable, As content in a high density polyethylene, 100-2,000 ppm with respect to the quantity of a high density polyethylene Is preferable, and 200 to 1,000 ppm is more preferable. As the antioxidant, it is preferable to use only a secondary antioxidant (particularly a phosphorus-based antioxidant), and the content in the high-density polyethylene to be formed is 100 ppm or more 2 with respect to high-density polyethylene (HDPE). 1,000 ppm or less is preferable, and 200 ppm or more and 1,000 ppm or less is more preferable.

  In particular, the polyethylene layer on the side on which the ink receiving layer is formed is obtained by adding rutile or anatase type titanium oxide, fluorescent whitening agent, ultramarine blue to polyethylene, as is widely done in photographic paper, Those having improved whiteness and hue are preferred. Here, as a titanium oxide content, about 3-40 mass% is preferable with respect to polyethylene, and 4-30 mass% is more preferable. Although the thickness of a polyethylene layer does not have limitation in particular, 10-50 micrometers is suitable for both front and back layers. Further, an undercoat layer can be provided on the polyethylene layer in order to provide adhesion to the ink receiving layer. As the undercoat layer, aqueous polyester, gelatin and PVA are preferable. Moreover, as thickness of this undercoat layer, 0.01-5 micrometers is preferable.

  Polyethylene-coated paper can be used as glossy paper, or matte or silky surface that can be obtained with ordinary photographic printing paper by applying a so-called molding process when polyethylene is melt-extruded and coated on the base paper surface. Can also be used.

A back coat layer can be provided on the support, and examples of components that can be added to the back coat layer include a white pigment, an aqueous binder, and other components.
Examples of white pigments contained in the backcoat layer include light calcium carbonate, heavy calcium carbonate, kaolin, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc sulfide, zinc carbonate, satin white, and aluminum silicate. , Diatomaceous earth, calcium silicate, magnesium silicate, synthetic amorphous silica, colloidal silica, colloidal alumina, pseudoboehmite, aluminum hydroxide, alumina, lithopone, zeolite, hydrous halloysite, magnesium carbonate, magnesium hydroxide, white inorganic pigment, styrene And organic pigments such as polyethylene plastic pigments, acrylic plastic pigments, polyethylene, microcapsules, urea resins, and melamine resins.

Examples of the aqueous binder used in the back coat layer include styrene / maleate copolymer, styrene / acrylate copolymer, polyvinyl alcohol, silanol-modified polyvinyl alcohol, starch, cationized starch, casein, gelatin, carboxy Examples thereof include water-soluble polymers such as methyl cellulose, hydroxyethyl cellulose, and polyvinyl pyrrolidone, and water-dispersible polymers such as styrene butadiene latex and acrylic emulsion.
Examples of other components contained in the backcoat layer include an antifoaming agent, an antifoaming agent, a dye, a fluorescent brightening agent, a preservative, and a water-proofing agent.

<Inkjet recording medium manufacturing method>
The ink jet recording medium of the present invention comprises an ink-receiving layer coating liquid A containing the ink-receiving layer constituents described above as a coating liquid, and a protective composition containing the protective layer constituents described above as a coating liquid. The layer coating liquid B can be produced by coating and drying on a support.
The inkjet recording medium of the present invention is, for example, (1) simultaneously applied with the ink receiving layer coating liquid A and the protective layer coating liquid B containing hollow inorganic particles to form the ink receiving layer and the protective layer, or (2) The ink receiving layer formed by applying the ink receiving layer coating liquid A and the protective layer coating liquid B containing hollow inorganic particles and the protective layer are being dried, and the ink receiving layer and the protective layer are reduced. It can be prepared by applying a basic solution having a boron compound to the ink receiving layer and the protective layer at any time before showing rate drying.
Each of the coating solutions can be applied using, for example, a slide bead coater.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist thereof. Unless otherwise specified, “%” and “part” are based on mass.

Example 1
<Production of support>
50 parts of LBKP made of acacia and 50 parts of LBKP made of aspen were each beaten to 300 ml of Canadian freeness by a disc refiner to prepare a pulp slurry.
Subsequently, to the pulp slurry obtained above, per starch, cationic starch (Japan NSC, CATO 304L) 1.3%, anionic polyacrylamide (Hoshiko Chemical Co., Ltd., Polyaclon ST-13) 0.15% , 0.29% alkyl ketene dimer (Arakawa Chemical, size pine K), 0.29% epoxidized behenamide, 0.32% polyamide polyamine epichlorohydrin (Arakawa Chemical Co., Ltd., Arafix 100) was added. Later, 0.12% of antifoam was added.

In the process of making the pulp slurry prepared as described above with a long paper machine and pressing the felt surface of the web against the drum dryer cylinder through the dryer canvas for drying, the tensile force of the dryer canvas is 1.6 kg / After drying at a setting of cm, 1 g / m ² of polyvinyl alcohol (manufactured by Kuraray Co., Ltd., KL-118) was applied to both sides of the base paper with a size press and dried, and a calendar treatment was performed. The base paper was made with a basis weight of 166 g / m ² to obtain a base paper (base paper) having a thickness of 160 μm.

After the corona discharge treatment was performed on the wire surface (back surface) side of the obtained base paper, high-density polyethylene was coated to a thickness of 25 μm using a melt extruder, and a thermoplastic resin layer comprising a mat surface was formed. (Hereinafter, this thermoplastic resin layer surface is referred to as “back surface”). The thermoplastic resin layer on the back side is further subjected to corona discharge treatment, and then, as an antistatic agent, aluminum oxide (Nissan Chemical Industry Co., Ltd., Alumina Sol 100) and silicon dioxide (Nissan Chemical Industry Co., Ltd., Snow A dispersion in which Tex O) was dispersed in water at a mass ratio of 1: 2 was applied so that the dry mass was 0.2 g / m ² and dried to obtain a support.

<Preparation of inkjet recording sheet>
-Preparation of coating liquid A for ink receiving layer-
(1) Gas phase method silica fine particles having the following composition, (2) ion-exchanged water, (3) “Charol DC-902P”, and (4) “ZA-30” are mixed, and a non-media disperser ( For example, after being dispersed using an ultrasonic disperser (manufactured by SMT Co., Ltd.), the dispersion was heated to 45 ° C. and held for 20 hours, after which (5) boric acid and (6) polyvinyl were added. Alcohol solution B was added at 30 ° C. to prepare ink-receiving layer coating solution A.

[Composition of coating liquid A1 for ink receiving layer]
(1) Gas phase method silica fine particles (inorganic fine particles) 10.0 parts [AEROSIL300SV, manufactured by Nippon Aerosil Co., Ltd.]
(2) Ion-exchanged water 62.8 parts (3) “Charol DC-902P” (51.5% aqueous solution) 0.87 parts (dispersant, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.)
(4) "ZA-30" [Zirconyl acetate, manufactured by Daiichi Rare Element Chemical Co., Ltd.] 0.54 parts (5) Boric acid (crosslinking agent) 0.44 parts (6) Polyvinyl alcohol (water-soluble resin) Solution B 34.9 parts

(Composition of polyvinyl alcohol solution B)
Polyvinyl alcohol 2.43 parts [manufactured by Kuraray Co., Ltd., “PVA235”, saponification degree 88%, polymerization degree 3500]
Polyoxyethylene lauryl ether (surfactant) 0.03 part ["Emulgen 109P" (10% aqueous solution), HLB value 13.6, manufactured by Kao Corporation]
・ Diethylene glycol monobutyl ether 0.74 parts [Butisenol 20P, manufactured by Kyowa Hakko Chemical Co., Ltd.]
・ Ion exchange water 31.0 parts

-Preparation of protective layer coating liquid C1-
(1) Hollow silica particles having the following composition, (2) ion-exchanged water, (3) surfactant, and (4) polyvinyl alcohol (7% solution) solution were added at 30 ° C., and the hollow silica fine particle concentration was A protective layer coating solution C1 was prepared so as to be 2 mass%.

[Composition of coating liquid C1 for protective layer]
(1) Hollow silica particles [Sirinax, manufactured by Nippon Steel & Mining Co., Ltd .: particle diameter 130 nm] 2 parts (2) 94.7 parts of ion-exchanged water (3) Polyoxyethylene lauryl ether (surfactant) 0.5 Part ["Emulgen 109P" (10% aqueous solution), HLB value 13.6, manufactured by Kao Corporation]
(4) Polyvinyl alcohol (7% solution) solution 2.8 parts [Kuraray Co., Ltd., PVA235]

-Preparation of inkjet recording sheet-
Was subjected to corona discharge treatment on the front surface of the support, in order from a side closer to the support, the ink receiving layer coating solution A coating amount of 184 ml / m ^2, the protective layer coating liquid C1 in 20 ml / m ² Simultaneous multi-layer coating was performed with a slide bead coater so as to obtain a coating amount. At that time, 5 times diluted polyaluminum chloride aqueous solution [Alphain 83 (manufactured by Daimei Chemical Co., Ltd.)] was mixed and applied in the ink-receiving layer coating solution at a coating amount of 10.8 ml / m ² immediately before coating. did. It dried with the hot air dryer at 80 degreeC (wind speed 3-8 m / sec) until the solid content density | concentration of the application layer became 20%. This coating layer showed constant rate drying during this period. And before showing the rate-decreasing drying, it was immersed in the basic solution D of the following composition for 3 seconds, the 13 g / m < ² > was made to adhere on the said coating layer, and also it dried at 80 degreeC for 10 minutes. Thus, the ink jet recording sheet of Example 1 provided with the ink receiving layer and the protective layer (the ink receiving layer having a dry film thickness of 34 μm, the protective layer having a dry film thickness of about 0.4 μm, the hollow inorganic particles in the protective layer) The solid content coating amount of 0.4 g / m ² ) was prepared.

[Set of basic solution D]
(1) Boric acid 0.65 parts (2) Ammonium carbonate [primary; manufactured by Kanto Chemical Co., Ltd.] 4 parts (3) Ion-exchanged water 89.4 parts (4 polyoxyethylene lauryl ether (surfactant) 6 parts ["Emulgen 109P" (10% aqueous solution), HLB value 13.6, manufactured by Kao Corporation]

(Example 2)
In preparation of the inkjet recording sheet of Example 1, the protective layer coating solution C1 was changed to the protective layer coating solution C2 having the following composition, and the coating amount of the protective layer coating solution C2 was changed to 40 ml / m ^2. In the same manner as in Example 1, an ink jet recording sheet of Example 2 was produced. The solid content coating amount of the hollow inorganic particles in the protective layer of the ink jet recording sheet of Example 2 is 4 g / m ² .

[Composition of coating liquid C2 for protective layer]
(1) Hollow silica particles [Sirinax, manufactured by Nippon Steel & Mining Co., Ltd .: particle diameter 130 nm] 1 part (2) 8.81 parts of ion-exchanged water (3) polyoxyethylene lauryl ether (surfactant) 0.05 Part ["Emulgen 109P" (10% aqueous solution), HLB value 13.6, manufactured by Kao Corporation]
(4) Polyvinyl alcohol (7% solution) solution 0.28 part [manufactured by Kuraray Co., Ltd., PVA235]

(Example 3)
In the production of the inkjet recording sheet of Example 2, Example 2 was used except that hollow silica contained in the protective layer coating solution having a particle size of 80 nm [Silinax, manufactured by Nittetsu Mining Co., Ltd.] was used. Similarly, an inkjet recording sheet of Example 3 was produced. The solid content coating amount of the hollow inorganic particles in the protective layer of the ink jet recording sheet of Example 3 is 4 g / m ² .

Example 4
In the production of the ink jet recording sheet of Example 2, the hollow silica contained in the protective layer coating solution was replaced with hollow silica having a particle size of 3 μm (Washin microcapsules, manufactured by Washin Chemical Co., Ltd.), In the same manner as in Example 2, an inkjet recording sheet of Example 4 was produced. The solid content coating amount of the hollow inorganic particles in the protective layer of the ink jet recording sheet of Example 4 is 4 g / m ² .

(Example 5)
In the production of the ink jet recording sheet of Example 1, the ink jet recording sheet of Example 5 was prepared in the same manner as in Example 1 except that the coating amount of the protective layer coating liquid C1 was changed to 2.5 ml / m ^2. Produced. The solid content application amount of the hollow inorganic particles in the protective layer of the inkjet recording sheet of Example 5 is 0.05 g / m ² .

(Example 6)
In the production of the inkjet recording sheet of Example 2, the inkjet recording sheet of Example 2 was prepared in the same manner as in Example 2 except that the coating amount of the protective layer coating liquid C2 was changed to 2.5 ml / m ^2. Produced. The solid content coating amount of the hollow inorganic particles in the protective layer of the inkjet recording sheet of Example 6 is 2 g / m ² .

(Comparative Example 1)
In the production of the ink jet recording sheet of Example 2, colloidal silica (Quarton PL7, manufactured by Fuso Chemical Industry Co., Ltd.) having a primary particle diameter of 75 nm was used in place of the hollow silica contained in the protective layer coating solution. In the same manner as in Example 1, an inkjet recording sheet of Comparative Example 1 was produced. The solid content coating amount of the hollow inorganic particles in the protective layer of the inkjet recording sheet of Comparative Example 1 is 0 g / m ² .

(Comparative Example 2)
In the production of the ink jet recording sheet of Example 1, the ink receiving layer coating liquid A2 having the following composition was used instead of the ink receiving layer coating liquid A1, and the protective layer was not formed. Thus, an inkjet recording sheet of Comparative Example 2 was produced.

[Composition of coating liquid A2 for ink receiving layer]
(1) Gas phase method silica fine particles (inorganic fine particles) 8 parts [AEROSIL300SV, manufactured by Nippon Aerosil Co., Ltd.]
(2) Hollow silica fine particles 2 parts [Silinax, manufactured by Nippon Steel & Mining Co., Ltd .: particle diameter 130 nm]
(3) Ion-exchanged water 62.8 parts (4) “Charol DC-902P” (51.5% aqueous solution) 0.87 parts [Dispersant, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.]
(5) "ZA-30" [Zirconyl acetate, manufactured by Daiichi Rare Element Chemical Co., Ltd.] 0.54 parts (6) Boric acid (crosslinking agent) 0.44 parts (7) Polyvinyl alcohol (water-soluble resin) Solution B 34.9 parts

<Evaluation>
The following evaluation was performed about each of the inkjet recording sheet of Examples 1-6 obtained from the above, and the inkjet recording sheet of Comparative Examples 1-2.

[Scratch resistance]
Prepare two non-printed inkjet recording sheets, with the surfaces of the inkjet recording sheets (sides where the protective layer is exposed) facing each other, with one surface facing up and the other facing down Overlapped so that Further, after removing the one (lower) ink jet recording sheet with 100 g of weight placed on the other (upper) ink jet recording sheet, scratches on the ink receiving layer surface of the ink jet recording sheet Was visually observed. The scratch resistance of the inkjet recording sheet was evaluated according to the following criteria.
-Evaluation criteria-
A: No scratches are observed.
B: Scratches are slightly observed, but there is no problem in practical use.
C: Scratches are observed, but practically acceptable level.
D: A level of unacceptable practical damage due to strong scratches.

[Glossiness]
Using a digital variable gloss meter (Suga Test Instruments Co., Ltd .: UGV-6P), the 60-degree glossiness of each inkjet recording sheet before printing was evaluated. Thereafter, the glossiness of the inkjet recording sheet was evaluated according to the following criteria.
-Evaluation criteria-
A: 50 or more B: 40 or more and less than 50 C: 30 or more and less than 40 D: Less than 30

[Color density (black density)]
A black solid image was printed on each ink jet recording sheet using an ink jet printer (Seiko Epson Co., Ltd., PM-A820) loaded with a genuine ink set, and the environment was 23 ° C. and 50% RH. For 24 hours. Thereafter, the density of the black solid image portion of each inkjet recording sheet was measured with a reflection densitometer (Xrite 310TR, manufactured by X-rite).
Thereafter, the color density of the ink jet recording sheet was evaluated according to the following criteria.
-Evaluation criteria-
A: 2.5 or more B: 2.2 or more and less than 2.5 C: 2.0 or more and less than 2.2 D: Less than 2.0

[Ink absorbency]
Using an inkjet printer loaded with a genuine ink set (PM-A820, manufactured by Seiko Epson Corporation), yellow, magenta, cyan, red, blue, green, and black solid images are respectively printed on each inkjet recording sheet. Printing was performed, and the ink absorptivity was confirmed visually. Thereafter, the ink absorbability of the inkjet recording sheet was evaluated according to the following criteria.
-Evaluation criteria-
A: Ink absorption failure did not occur at all.
B: Ink absorption failure slightly occurred in one color, but it is within a practically allowable range.
C: Ink absorption failure occurs and unevenness can be visually recognized, which is a practical problem.

Contents of the protective layer for each of the inkjet recording sheets of Examples 1 to 6 and the inkjet recording sheets of Comparative Examples 1 and 2 (type of hollow inorganic particles in the protective layer, particle diameter [nm], solid content coating amount) Table 1 below shows the evaluation results of [g / m ² ] and protective layer layer thickness [μm]) and evaluation (the scratch resistance, glossiness, color density, and ink absorbency).

Claims (6)

  An ink jet recording medium comprising: a support; one or more ink receiving layers provided on the support; and a protective layer provided on the ink receiving layer and including hollow inorganic particles.   The inkjet recording medium according to claim 1, wherein the hollow inorganic particles have a particle diameter of 20 nm to 150 nm.   The inkjet recording medium according to claim 1, wherein the protective layer further contains a water-soluble resin. The inkjet recording medium according to any one of claims 1 to 3, wherein a solid content coating amount of the hollow inorganic particles in the protective layer is 0.05 g / m ² to ⁵ g / m ² .   The inkjet recording medium according to any one of claims 1 to 4, wherein the hollow inorganic particles are hollow silica particles.   (1) Simultaneously applying the ink receiving layer coating liquid and the protective layer coating liquid containing hollow inorganic particles to form the ink receiving layer and the protective layer, or (2) Ink receiving layer coating liquid and the hollow inorganic particles. A boron compound at any time during the drying of the ink receiving layer and the protective layer formed by applying a protective layer coating liquid containing the ink, and before the ink receiving layer and the protective layer exhibit reduced-rate drying. A method for producing an ink jet recording medium, comprising applying a basic solution having a water content to the ink receiving layer and the protective layer.