JP2009233936A - Inkjet recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink recording medium which enables a printed material to obtain a texture of offset printing coating paper and to have a high water resistant ink receiving layer and a good quality without spur traces as well. <P>SOLUTION: The inkjet recording medium has, on one side or both sides of the base paper thereof, the base paper consisting mainly of wood pulp, an ink receiving layer mainly comprised of kaolin and acetoacetyl polyvinyl alcohol, wherein the ratio of the acetoacetyl polyvinyl alcohol to the total 100 parts by mass of all the inorganic dye contained in the ink receiving layer occupies 5 to 10 prts. by mass. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to an ink jet recording medium having a texture of coated paper for offset printing, and an ink jet recording method for performing ink jet recording using the same.
About.

  The ink jet recording method is easy to make full color and has little printing noise. Therefore, the ink jet recording method has been used in many applications as the printing performance is rapidly improved. These applications include, for example, document recording from document creation software, recording of digital images such as digital photographs, reproduction of beautiful printed materials such as silver halide photographs and books captured by a scanner, and a relatively small number of posters. For example, creating an image for exhibition. In particular, in recent years, in the commercial printing field of small lots and many varieties, printing is often performed by an ink jet recording method instead of an offset printing method.

  Ink jet recording media having configurations suitable for these applications have been proposed. For example, when simply recording characters, a plain paper type medium that directly records on the paper surface is used. In addition, when it is desired to obtain resolution and color reproducibility comparable to silver halide photography, it is necessary to absorb the ink ejected from the printer, so a coated paper type provided with an ink receiving layer as the coating layer is used. . When particularly high glossiness is required, a cast paper type in which a coating layer is formed by, for example, a cast method is used among the coated paper types. On the other hand, in the case of posters and display applications, a roll type having a thick coating layer has been developed and used.

In the case of the above-mentioned coated paper type, the amount of ink used increases as the color reproducibility of the image is improved, so that a larger ink absorption capacity is required for the ink receiving layer. For this reason, a porous material such as synthetic amorphous silica is often used for the ink receiving layer. In this case, the ink absorption is improved, but the glossiness is low and the texture is different from that of the offset printed matter. There's a problem. In the case of the cast paper type, the gloss is too high compared to general coated paper for offset printing, and the paper is thick, so the texture is different from that of the offset printed matter.
In addition, these inkjet recording media generally use a large amount of, for example, silica, alumina, polyvinyl alcohol, ethylene vinyl acetate emulsion, ink fixing agents (polyamine, DADMAC, polyamidine, etc.) as expensive raw materials. Compared with coated paper for offset printing, the manufacturing cost is higher.

On the other hand, when printing on general offset printing paper with an inkjet printer, the ink absorption capacity of the coating layer is low, so feathering (bleeding), bleed (color boundary bleeding), and solid printing unevenness ( Defects such as uneven printing density and cockling (waving the printed part) occur.
In addition, gravure coated coated paper, which is a type of printing paper, is relatively oil-absorbing among printed coated papers, so printing with an inkjet printer is slightly better than offset coated paper. Become. However, the coated paper for gravure printing is calendered with strong linear pressure to give gravure printing suitability, so there are few voids in the coating layer and the ink absorption capacity is not sufficient. The same defect as that of general offset printing paper occurs.

Therefore, as an inkjet recording medium having a texture of coated paper for offset printing, the recording layer (coating layer) has an average particle diameter of 0.2 to 2.0 μm and 1 ≦ L / W ≦. The composition has kaolin satisfying 50 (L represents the long diameter of the particle, W represents the short diameter (thickness) of the particle) as a pigment, and the 75 ° glossiness of the recording layer surface according to JIS-Z-8741 is 40% or more Is disclosed (for example, see Patent Document 1).
Moreover, as offset printing paper having ink jet aptitude, it has a pigment coating layer (coating layer) having kaolin as a main component and a predetermined cobb size (water absorption), and a cationic resin is applied to this pigment coating layer. A structure impregnated with coating is disclosed (for example, see Patent Document 2).
In addition, an ink containing a water-insoluble or hardly soluble color material, water as a dispersion medium, and a water-soluble organic solvent and having a color material concentration of 6% by mass or more and a viscosity at 25 ° C. of 5 mPa · s or more is used. Inkjet recording having an ink-receiving layer mainly composed of kaolin and binder, and the ratio of the binder to 100 parts by mass in total of all inorganic pigments contained in the ink-receiving layer is 0.5 parts by mass or more and less than 10 parts by mass A technique for performing ink jet recording on a medium is disclosed (for example, see Patent Document 3).

JP 2004-209965 A JP 2004-270104 A JP 2008-049541 A

However, when printing is performed with an inkjet printer using the coated paper described in Patent Document 1 and Patent Document 2, the ink absorbability is not sufficient, and good print quality may not be obtained. In the technique of Patent Document 3, although good print quality can be obtained, the ink receiving layer is insufficient in water resistance. Therefore, if the surface is rubbed with a wet hand, the printed part may be peeled off or called a spur mark. There were cases where defects occurred.
Here, the spur mark is a mark that is generated when the tooth tip of a gear (spur) attached to the paper discharge portion of the ink jet printer for the purpose of transporting the printed paper hits the print surface of the paper. This is composed of a white defect caused by the ink being peeled off by the gear and a stain defect caused by transferring the ink adhering to the gear to another portion of the paper.
Accordingly, an object of the present invention is to provide an ink jet recording medium that can obtain the texture of coated paper for offset printing, has a high water resistance of the ink receiving layer, and can obtain a good printed matter without spur marks.

  The inventors of the present invention are suitable for inkjet printing, can obtain the texture of coated paper for offset printing, and as a result of earnestly examining the structure having high water resistance of the ink receiving layer and no spurs, the kind of pigment in the ink receiving layer, It has been found that the above problem can be solved by defining the binder.

That is, the inkjet recording medium of the present invention has an ink receiving layer mainly composed of kaolin and acetoacetylated polyvinyl alcohol on one side or both sides of a base paper mainly composed of wood pulp, and is contained in the ink receiving layer. The ratio of the acetoacetylated polyvinyl alcohol to 100 parts by mass of all the inorganic pigments is 0.5 parts by mass or more and less than 10 parts by mass.
Further, the total amount of all the binder components contained in the ink receiving layer is 0.5 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass in total of all the inorganic pigments contained in the ink receiving layer. preferable.

The kaolin is preferably kaolin in which particles having a size of 0.4 μm or more and less than 4.2 μm account for 64% or more in terms of a volume-based integrated value when measured by a laser diffraction method.
The kaolin is preferably kaolin having an average particle size of 0.15 μm or more and less than 0.50 μm measured by a sedimentation method, and particles having a size of 2.0 μm or less occupy 95% or more by volume-based integrated value.

  The inkjet recording method according to the present invention is characterized in that an image is recorded on the inkjet recording medium using an ink containing at least water, a particulate colorant, and a wetting agent.

  According to the present invention, it is possible to obtain an ink jet recording medium in which a texture of coated paper for offset printing can be obtained, and a good printed matter having a high water resistance of the ink receiving layer and no spur trace can be obtained.

  Hereinafter, embodiments of an ink jet recording medium according to the present invention will be described.

(Base paper)
The base paper is mainly composed of wood pulp. Pulp such as chemical pulp (conifer bleached or unbleached kraft pulp, hardwood bleached or unbleached kraft pulp), mechanical pulp (ground pulp, thermomechanical pulp, chemical thermomechanical pulp, etc.), deinked pulp, etc. Can be used alone or in admixture at any ratio.
The pH at the time of papermaking of the base paper may be any of acidic, neutral and alkaline. Further, since the opacity of the paper tends to improve as the amount of the filler in the base paper increases, it is preferable to contain the filler in the paper. As the filler, known fillers such as hydrated silicic acid, white carbon, talc, kaolin, clay, calcium carbonate, titanium oxide, synthetic resin filler and the like can be used.
Furthermore, the base paper may contain auxiliary agents such as a sulfuric acid band, a sizing agent, a paper strength enhancer, a yield improver, a colorant, a dye, an antifoaming agent, and a pH adjuster as necessary. The basis weight of the base paper is not particularly limited.

  Before providing the ink receiving layer, a base press may be impregnated or coated with a size press solution prepared from starch, PVA, sizing agent, etc. for the purpose of enhancing paper strength and imparting size. The impregnation or coating method is not particularly limited, but may be performed by an impregnation method typified by a pound type size press or an application method typified by a rod metering size press, a gate roll coater, or a blade coater. preferable. In addition, the size press liquid is a fluorescent dye, a conductive agent, a water retention agent, a water resistance agent, a pH adjuster, an antifoaming agent, a lubricant, a preservative, as necessary, as long as the effects of the present invention are not impaired. An auxiliary agent such as a surfactant can be mixed in an arbitrary ratio.

(Ink receiving layer)
The ink receiving layer is provided on one side or both sides of the base paper.
1. Binder for Ink Receiving Layer The binder used for the ink receiving layer contains acetoacetylated polyvinyl alcohol. Thereby, the water resistance of the ink receiving layer can be improved, and spur marks can be reduced.
The acetoacetylated polyvinyl alcohol used in the present invention (hereinafter abbreviated as “acetoacetylated PVA”) is obtained by subjecting normal fully saponified polyvinyl alcohol or partially saponified polyvinyl alcohol to an addition reaction with diketene, or an acetoacetate ester. It can be obtained by transesterification and introducing an acetoacetyl group. The content of the acetoacetyl group in the acetoacetylated PVA is preferably in the range of about 0.2 to 15 mol%. When the content is less than 0.2 mol%, the water resistance tends to be insufficient, and when the content is more than 15 mol%. The ink absorbability tends to decrease.
Moreover, as a polymerization degree of acetoacetylated PVA, the thing of the range of 500-2500 is preferable. If the degree of polymerization is too small, the effect of improving water resistance will be reduced. If the degree of polymerization is too large, there will be no problem in terms of quality, but it will be difficult to dissolve in water and will become difficult to handle due to high viscosity after dissolution. In addition, the water resistance becomes too high, and the ink absorbability may be lowered. In view of the balance of ink fixability, water resistance, liquid viscosity, ink absorbability and the like, the polymerization degree is particularly preferably in the range of 1000 to 2000.

Furthermore, the saponification degree of acetoacetylated PVA is preferably in the range of 70 to 100 mol%. If it is less than 70 mol%, the ink absorbency tends to decrease. From the viewpoint of ink absorbability and practicality, the saponification degree is preferably in the range of 75 to 99 mol%, particularly in the range of 85 to 95 mol%.
The content of acetoacetyl groups is preferably in the range of 1 to 20 mol%. If this amount is less than 1 mol%, the effect of improving the water resistance is not sufficiently exhibited, and if it exceeds 20 mol%, the ink absorbability is lowered. Therefore, the content of the acetoacetyl group is particularly preferably in the range of 2 to 10 mol% from the viewpoint of balance between water resistance and ink absorbability.
In addition, there is no restriction | limiting in particular about the manufacturing method of the acetoacetylated polyvinyl alcohol used by this invention, For example, the method of making diketene addition reaction to the conventionally well-known method, for example, the complete saponification thing of polyvinyl alcohol, or a partial saponification thing, or polyvinyl It can be produced by a method of transesterifying a partially saponified alcohol with acetoacetate.

  In the present invention, when the total amount of inorganic pigments contained in the ink receiving layer is 100 parts by mass, the content of the acetoacetylated PVA described above needs to be 0.5 parts by mass or more and 10 parts by mass or less. Yes, it is preferably 2 parts by mass or more and 8 parts by mass or less. Since acetoacetylated PVA in the ink receiving layer has a function as a binder, the smaller the content ratio, the more voids in the ink receiving layer and the better the ink absorbability. However, when the content of acetoacetylated PVA is less than 0.5 parts by mass, the ink absorbability is good, but the strength of the ink receiving layer is insufficient, and paper dust is generated during cutting. On the other hand, when the content ratio of acetoacetylated PVA exceeds 10 parts by mass, voids existing in the ink receiving layer are filled with acetoacetylated PVA, and the ink absorption capacity is reduced, so that good print quality can be obtained. It becomes difficult.

In the present invention, in addition to the acetoacetylated PVA described above as a binder, other polymer compounds can be used. As a high molecular compound, for example, one kind from among starches such as oxidized starch, etherified starch and esterified starch, polyvinyl alcohol and modified products thereof, casein, gelatin, carboxymethylcellulose, polyurethane, vinyl acetate and unsaturated polyester resin Two or more types can be appropriately selected and used. In the case of using a plurality of polymer compounds in addition to acetoacetylated PVA as the binder of the ink receiving layer, in order to maintain the voids of the ink receiving layer, the total binder (acetate relative to 100 parts by weight of the inorganic pigment of the ink receiving layer) The content ratio of acetylated PVA) is preferably 10 parts by mass or less.
If the content of the resin other than acetoacetylated PVA in all binders exceeds 60 parts by mass, the ink-receiving layer tends to have poor water resistance or increase in spur marks.

  The reason why the spur mark is reduced by containing acetoacetylated PVA in the ink receiving layer binder is not clear, but is considered as follows. In a preferred embodiment of the present invention, the amount of the binder in the ink receiving layer is small (the content ratio of all binders to 100 parts by weight of the inorganic pigment is 10 parts by weight or less). Easier to dissolve in water. For this reason, the ink receiving layer of the printing unit is easily peeled off together with the ink colorant by the blade edge of the spur and easily becomes a spur mark. Since acetoacetylated PVA is water-insoluble in PVA by acetoacetylation, the ink receiving layer in the printed part does not dissolve in water as the ink solvent even if the amount added to the ink receiving layer is small. Spur marks can be reduced. Further, since the water resistance of acetoacetylated PVA is high, it is considered that the water resistance of the ink receiving layer is also improved.

2. Inorganic Pigment for Ink Receiving Layer The inorganic pigment for the ink receiving layer contains kaolin. Kaolin is a clay containing at least one kind of kaolin mineral such as kaolinite, halloysite, dickite, and nacklite, and has a plate-like shape. In the present invention, any known kaolin used for general coated paper for offset printing may be used. Examples of kaolin include Georgia, Brazil, and China, and grades such as grade 1, grade 2, and delami. However, kaolin is not limited to these. Moreover, what mixed 1 type or 2 or more types of kaolin can also be selected suitably, and can also be used as a pigment.
The particle size distribution measured by the general laser diffraction method of kaolin exists in the range of about 0.05 μm to about 40 μm. For example, the particle size distribution of KCS (product name of Kaolin manufactured by Imeris) is based on volume. Of particles having a particle diameter of 0.4 μm or more and less than 4.2 μm, 53% of particles having a particle diameter of less than 0.4 μm, and 21% of particles having a particle diameter of 4.2 μm or more. Moreover, the particle size distribution by the precipitation method of a general kaolin exists in the range of about 0.05-20 micrometers, for example, the particle size distribution by the precipitation method of KCS (Imeris Kaolin product name) is 0. 05 to 10 μm.

Here, in order to improve the ink absorptivity, it is preferable to use kaolin whose particle size distribution is adjusted instead of the above-described general kaolin.
In the present invention, it is preferable to use kaolin in which particles having a size of 0.4 μm or more and less than 4.2 μm account for 64% or more in terms of a volume-based integrated value when measured by a laser diffraction method. When kaolin having a particle size distribution concentrated in a range of 0.4 μm or more and less than 4.2 μm (64% or more) is used, the ink absorbability is superior to the above-described general kaolin.
Moreover, it is preferable to use kaolin having an average particle diameter measured by a sedimentation method of 0.15 μm or more and less than 0.50 μm, and particles of 2.0 μm or less occupying 95% or more by volume-based integrated value. When using kaolin having an average particle size measured by the sedimentation method of 0.15 μm or more and less than 0.50 μm and particles of 2.0 μm or less occupying 95% or more by volume-based integrated value, the above-mentioned general kaolin Excellent ink absorbency compared to

The reason why the ink absorbency is excellent when using kaolin whose particle size distribution is adjusted to the above range is that the particle size distribution width is narrow and the particle diameter is uniform, so the packing density of the pigment particles is low, and the porous and bulky ink acceptance This is because the layer can be formed. A porous ink receiving layer is considered to have better ink absorbability than an ink receiving layer with a densely packed pigment.
The measurement of the particle size distribution by the laser diffraction method uses a light scattering phenomenon, and is obtained by Mie theory and the Fraunhofer approximation. However, since the method for calculating the particle size distribution from the scattered light differs depending on the particle size measuring device, in the present invention, the laser method particle size measuring device (Malvern Mastersizer S type, the light source is red light of 633 nm (He-Ne laser) Use the value measured by blue light 466nm (LED)).
The measurement of the particle size distribution by the sedimentation method is a method of obtaining the particle size distribution from the sedimentation speed on the assumption that the particles dispersed in the solvent settle according to the Stokes sedimentation rate equation. The particle diameter obtained by the sedimentation method is called a Stokes equivalent diameter (Stokes diameter), and the particle size distribution is based on mass.
In the present invention, as a method for measuring the particle size distribution, a sample slurry containing a sample slurry containing kaolin in pure water is dropped and mixed to form a uniform dispersion.

(Other ingredients)
For the ink receiving layer, other organic pigments such as plastic pigments, pigment dispersants, printability improvers, thickeners, water retention agents, lubricants, antifoaming agents, foam suppressors, mold release agents, foaming, etc. Auxiliaries such as agents, colored dyes, colored pigments, fluorescent dyes, preservatives, water-resistant agents, surfactants, pH adjusters, and the like can be added as appropriate.

(Coating amount)
The coating amount of the ink receiving layer is not formed in particular limitation, it is possible at one side per 2 g / ^{m 2} or more 40 g / ^{m 2} or less is preferable, and 5 g / ^{m 2} or more 30 g / ^{m 2} or less per side preferable. The greater the coating amount, the greater the amount of voids in the ink receiving layer, and the better the ink absorbability. When the coating amount of the ink receiving layer is less than 2 g / m ² per side, the base paper as a base material cannot be sufficiently coated, and the coated paper surface remains rugged and resembles non-coated paper There is a tendency that the glossiness of the white paper does not improve and the glossy coated paper for offset printing is difficult to obtain. On the other hand, when the coating amount is less than 2 g / m ² per side, the absorption capacity of the ink receiving layer tends to decrease, and printing defects such as feathering and bleeding tend to occur. On the other hand, when the coating amount of the ink receiving layer exceeds 40 g / m ² per side, the drying load during coating is large, so that workability tends to be inferior and the cost tends to be high.

(Coating method)
As a method for providing an ink receiving layer on a base paper, a general coating apparatus, a blade coater, a roll coater, an air knife coater, a bar coater, a gate roll coater, a curtain coater, a gravure coater, a flexographic gravure coater, and a spray coater. Various devices such as a size press can be used on-machine or off-machine. The ink receiving layer may be provided on one side or both sides of the base paper, and may be provided in one layer or two or more layers.

(Surface roughness)
In the present invention, the glossy coated paper for offset printing and the matte coated paper for offset printing can be made separately by adjusting the surface roughness of the ink receiving layer. To make gloss coated paper for offset printing, hard backing with a clamping pressure of 1000 kPa according to JIS P8151 (paper and paperboard-surface roughness and smoothness test method (air leak method)-print surf tester method) Is used, the surface roughness of the ink receiving layer may be 0.6 μm or more and 1.4 μm or less. Further, in order to obtain a matte coated paper for offset printing, the surface roughness may be more than 1.4 μm and not more than 5.0 μm. Here, JIS P8151 defines a method for measuring surface roughness using a Print-surf tester.

The greater the surface roughness, the better the ink absorbency. However, if the surface roughness exceeds 5.0 μm, the surface of the ink receiving layer becomes rough, and a texture like matte coated paper for offset printing cannot be obtained. On the other hand, the smaller the surface roughness of the ink receiving layer, the closer to the glossy coated paper for offset printing. For this reason, the surface roughness of the ink receiving layer is defined within the above range.
When the surface roughness of the ink receiving layer is 1.4 μm or less, a texture of glossy coated paper for offset printing can be obtained, but when the surface roughness is less than 0.6 μm, a strong calendar is used to smooth the surface. By performing the treatment or the like, voids in the ink receiving layer are reduced, and furthermore, the contact area of the ink droplets with the paper surface is reduced and the ink absorbability is lowered. On the other hand, when the surface roughness of the ink receiving layer exceeds 1.4 μm, the ink absorbency is good, but the glossiness is low and the touch is not good. I can't get it. For this reason, the surface roughness of the ink receiving layer is defined within the above range.

As a method for adjusting the surface roughness, it is possible to appropriately change the pigment used in the ink receiving layer, the concentration of the paint, the coating amount, the coating method, and the like. For example, the surface roughness tends to increase by decreasing the coating concentration and decreasing the coating amount. Further, it is easier to increase the surface roughness by using the pre-metering coating method (curtain coating, gate roll coating, etc.) than the post-metering coating method (blade coating, etc.).
Further, as a method for obtaining a matte texture having a surface roughness of more than 1.4 μm and not more than 5.0 μm, there is a method in which no calendar treatment is performed.
On the other hand, as a method for obtaining a glossy texture with a surface roughness of 0.6 μm or more and 1.4 μm or less, there is a method of performing a calendar process. The calendering process uses a calender device such as a machine calender, super calender, soft calender, shoe calender, etc. after the ink-receiving layer is provided, and conditions such as treatment temperature, treatment speed, treatment line pressure, treatment step number, roll diameter, material, etc. Can be appropriately adjusted, selected, and surface-treated.

In general coated offset printing paper used is graded by coating weight, of high-quality paper (100% chemical pulp) based on both sides of the coating amount 20 g / m ² before and after the ones A2 coat It is called paper. Of the A2 coated paper, the one with high gloss is called A2 gloss coated paper, and the one with low gloss is called A2 mat coated paper. Examples of A2 matte coated paper include Oji Paper's New Age, OK Royal Court, Nippon Paper's Silver Diamond, Ulite, and Neptune.

(Blank gloss)
When obtaining the glossy coated paper for offset printing described above, it is preferable that the glossiness of the white paper at the light incident angle of 75 degrees according to JIS Z8741 on the surface of the ink receiving layer is 55% or more and less than 80%. In order to improve the ink absorbability, the lower the glossiness of the white paper, the better. On the other hand, the higher the glossiness of the white paper, the better the glossy coated paper for offset printing. Accordingly, the glossiness of blank paper is defined within the above range.
When the glossiness of the blank paper on the surface of the ink receiving layer is less than 55%, the texture of glossy coated paper for offset printing tends not to be obtained. On the other hand, when the glossiness of white paper exceeds 80%, voids in the ink receiving layer tend to decrease and ink absorbency tends to decrease. More preferably, the blank paper glossiness on the surface of the ink receiving layer is 60% or more and less than 75%.

  When obtaining the above-described matte coated paper for offset printing, it is preferable that the glossiness of the white paper at the light incident angle of 75 degrees according to JIS Z8741 on the surface of the ink receiving layer is 20% or more and less than 55%. In order to improve the ink absorbability, the lower the glossiness of the white paper, the better. However, when the glossiness of the white paper exceeds 55%, the texture of the matte coated paper for offset printing tends not to be obtained. On the other hand, when the blank paper glossiness of the surface of the ink receiving layer is less than 20%, the texture of the matte coated paper for offset printing tends not to be obtained. More preferably, the blank paper glossiness on the surface of the ink receiving layer is 25% or more and 45% or less.

The white paper glossiness can be adjusted by appropriately selecting the pigment used in the ink receiving layer, the coating concentration, the coating amount, the coating method, and the like.
In addition, the glossiness of the white paper is adjusted by using a calendar device such as a machine calendar, super calendar, soft calendar, shoe calendar, etc. after providing an ink receiving layer, processing temperature, processing speed, processing linear pressure, processing step number, and roll diameter. It is possible to perform the surface treatment by appropriately adjusting and selecting conditions such as material. The stronger the calendering process, the higher the white paper glossiness and the smaller the surface roughness value.

  The ink jet recording medium of the present invention can be used not only as an ink jet recording system recording paper as described above, but also as an electrophotographic recording paper, an offset printing paper, and a gravure printing paper.

<Ink>
The ink used in the inkjet recording medium of the present invention contains at least water, a particulate colorant, and a wetting agent, and contains a penetrating agent, a surfactant, and other components as necessary. The thing which becomes.
The ink has a surface tension at 25 ° C. of 20 to 35 mN / m, and more preferably 23 to 34 mN / m. If the surface tension is less than 20 mN / m, bleeding on the recording medium of the present invention becomes noticeable, and stable ink ejection may not be obtained. If the surface tension exceeds 35 mN / m, ink on the recording medium may be obtained. Infiltration may not occur sufficiently, leading to beading and prolonged drying time.
Here, the said surface tension can be measured at 25 degreeC using a platinum plate, for example using a surface tension measuring apparatus (Kyowa Interface Science Co., Ltd. make, CBVP-Z).

(Coloring agent)
As the particulate colorant, it is preferable to use colored fine particles (colored pigment), and in the ink, the colorant is dispersed in a liquid component mainly composed of water and a wetting agent. In the ink jet recording medium of the present invention, a white pigment called kaolin, which has low transparency and high concealment, is used for the ink receiving layer. Therefore, when the so-called dye ink in which the colorant is dissolved in the liquid component in the ink is applied to the ink jet recording medium of the present invention, the colorant in the ink soaked in the ink receiving layer has high concealability. It is hidden by the white pigment, and a high image density does not appear. When ink-jet printing with a dye ink on a recording medium using such a highly concealed white pigment, no matter how much the amount of ink to be applied is increased, only the colorant present near the surface layer contributes to the image density. It becomes a low and non-contrast image, and it is difficult to obtain an image quality close to that of offset printing.

  On the other hand, when the so-called pigment ink in which the colorant is dispersed in the liquid component of the ink is applied to the inkjet recording medium of the present invention, the ink receiving layer serves as a filter that separates the colorant and the liquid component in the ink. In order to work, only the liquid component in the ink is selectively soaked in the inside of the receiving layer or the support, and the colorant in the ink is efficiently retained on the surface of the ink receiving layer, so that a sufficient image density can be obtained even with a small amount of ink. Can be obtained.

As the colored fine particles, an aqueous dispersion of fine polymer particles containing at least one colorant of pigment and dye is preferably used.
Here, the term “containing a color material” means either or both of a state in which the color material is enclosed in the polymer fine particles and a state in which the color material is adsorbed on the surface of the polymer fine particles. In this case, it is not necessary for all of the color material blended in the ink of the present invention to be encapsulated or adsorbed in the polymer fine particles, and the color material is dispersed in the emulsion as long as the effects of the present invention are not impaired. Also good. The color material is not particularly limited as long as it is water-insoluble or hardly water-soluble and can be adsorbed by the polymer, and can be appropriately selected according to the purpose.
Here, the “water-insoluble or hardly water-soluble” means that the coloring material does not dissolve 10 parts by mass or more with respect to 100 parts by mass of water at 20 ° C. Further, “dissolve” means that separation or sedimentation of the coloring material is not observed in the surface layer or the lower layer of the aqueous solution visually.

  The volume average particle diameter of the polymer fine particles (colored fine particles) containing the colorant is preferably 0.01 to 0.16 μm in the ink.

Examples of the colorant include dyes such as oil-soluble dyes, disperse dyes, and water-soluble dyes, and pigments. Oil-soluble dyes and disperse dyes are preferable from the viewpoint of good adsorptivity and encapsulation, but pigments are preferably used from the light resistance of the obtained image.
In addition, from the viewpoint of efficiently impregnating the polymer fine particles, each of the dyes is preferably dissolved in an organic solvent, for example, a ketone solvent in an amount of 2 g / liter or more, and more preferably 20 to 600 g / liter.
The water-soluble dye is a dye classified into an acid dye, a direct dye, a basic dye, a reactive dye, and a food dye in the color index, and preferably has excellent water resistance and light resistance. .

  Examples of the acid dyes and food dyes include C.I. I. Acid Yellow 17, 23, 42, 44, 79, 142; C.I. I. Acid Red 1,8,13,14,18,26,27,35,37,42,52,82,87,89,92,97,106,111,114,115,134,186,249,254 289; I. Acid Blue 9, 29, 45, 92, 249; I. Acid Black 1, 2, 7, 24, 26, 94; I. Food Yellow 3, 4; I. Food red 7, 9, 14; I. Food black 1, 2 etc. are mentioned.

  Examples of the direct dye include C.I. I. Direct yellow 1,12,24,26,33,44,50,86,120,132,142,144; I. Direct red 1,4,9,13,17,20,28,31,39,80,81,83,89,225,227; I. Direct orange 26, 29, 62, 102; I. Direct Blue 1, 2, 6, 15, 22, 25, 71, 76, 79, 86, 87, 90, 98, 163, 165, 199, 202; I. Direct black 19, 22, 32, 38, 51, 56, 71, 74, 75, 77, 154, 168, 171 and the like.

  Examples of the basic dye include C.I. I. Basic yellow 1, 2, 11, 13, 14, 15, 19, 21, 23, 24, 25, 28, 29, 32, 36, 40, 41, 45, 49, 51, 53, 63, 64, 65, 67, 70, 73, 77, 87, 91; C.I. I. Basic Red 2,12,13,14,15,18,22,23,24,27,29,35,36,38,39,46,49,51,52,54,59,68,69,70, 73, 78, 82, 102, 104, 109, 112; I. Basic blue 1,3,5,7,9,21,22,26,35,41,45,47,54,62,65,66,67,69,75,77,78,89,92,93, 105, 117, 120, 122, 124, 129, 137, 141, 147, 155; I. Basic black 2, 8 etc. are mentioned.

  Examples of the reactive dye include C.I. I. Reactive Black 3, 4, 7, 11, 12, 17; C.I. I. Reactive Yellow 1,5,11,13,14,20,21,22,25,40,47,51,55,65,67; I. Reactive Red 1,14,17,25,26,32,37,44,46,55,60,66,74,79,96,97; I. Reactive blue 1, 2, 7, 14, 15, 23, 32, 35, 38, 41, 63, 80, 95, and the like.

There is no restriction | limiting in particular as said pigment, According to the objective, it can select suitably, For example, any of an inorganic pigment and an organic pigment may be sufficient.
Examples of the inorganic pigment include titanium oxide, iron oxide, calcium carbonate, barium sulfate, aluminum hydroxide, barium yellow, cadmium red, chrome yellow, and carbon black. Among these, carbon black is preferable. In addition, as said carbon black, what was manufactured by well-known methods, such as a contact method, a furnace method, and a thermal method, is mentioned, for example.

  Examples of the organic pigment include azo pigments, polycyclic pigments, dye chelates, nitro pigments, nitroso pigments, and aniline black. Among these, azo pigments and polycyclic pigments are more preferable. Examples of the azo pigment include azo lakes, insoluble azo pigments, condensed azo pigments, and chelate azo pigments. Examples of the polycyclic pigment include phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, indigo pigments, thioindigo pigments, isoindolinone pigments, and quinofullerone pigments. Examples of the dye chelates include basic dye chelates and acidic dye chelates.

There is no restriction | limiting in particular as a color of the said pigment, According to the objective, it can select suitably, For example, the thing for black, the thing for color, etc. are mentioned. These may be used individually by 1 type and may use 2 or more types together.
Examples of the black color include carbon black (CI pigment black 7) such as furnace black, lamp black, acetylene black, channel black, copper, iron (CI pigment black 11), oxidation, and the like. Examples thereof include metals such as titanium, organic pigments such as aniline black (CI pigment black 1), and the like.

As for the color, for yellow, for example, C.I. I. Pigment Yellow 1 (Fast Yellow G), 3, 12 (Disazo Yellow AAA), 13, 14, 17, 23, 24, 34, 35, 37, 42 (Yellow Iron Oxide), 53, 55, 74, 81, 83 (Disazo Yellow HR), 95, 97, 98, 100, 101, 104, 108, 109, 110, 117, 120, 128, 138, 150, 153, and the like.
For magenta, for example, C.I. I. Pigment Red 1, 2, 3, 5, 17, 22 (Brilliant First Scarlet), 23, 31, 38, 48: 2 (Permanent Red 2B (Ba)), 48: 2 (Permanent Red 2B (Ca)), 48 : 3 (Permanent Red 2B (Sr)), 48: 4 (Permanent Red 2B (Mn)), 49: 1, 52: 2, 53: 1, 57: 1 (Brilliant Carmine 6B), 60: 1, 63: 1, 63: 2, 64: 1, 81 (Rhodamine 6G Lake), 83, 88, 92, 101 (Bengara), 104, 105, 106, 108 (Cadmium Red), 112, 114, 122 (Dimethylquinacridone), 123, 146, 149, 166, 168, 170, 172, 177, 178, 179, 185, 190, 193, 209, 2 19, etc.
For cyan, for example, C.I. I. Pigment Blue 1, 2, 15 (copper phthalocyanine blue R), 15: 1, 15: 2, 15: 3 (phthalocyanine blue G), 15: 4, 15: 6 (phthalocyanine blue E), 16, 17: 1, 56, 60, 63 and the like. In addition, as the intermediate colors for red, green and blue, C.I. I. Pigment red 177, 194, 224, C.I. I. Pigment orange 43, C.I. I. Pigment violet 3, 19, 23, 37, C.I. I. Pigment green 7, 36, and the like.

As the pigment, a self-dispersing pigment that can be stably dispersed without using a dispersant in which at least one hydrophilic group is bonded to the surface of the pigment directly or via another atomic group is suitably used. . As a result, unlike the conventional ink, a dispersant for dispersing the pigment becomes unnecessary. As the self-dispersing pigment, those having ionicity are preferable, and those having an anionic charge or those having a cationic charge are suitable.
The volume average particle size of the self-dispersing pigment is preferably 0.01 to 0.16 μm in the ink.

Examples of the anionic hydrophilic group include —COOM, —SO ₃ M, —PO ₃ HM, —PO ₃ M ₂ , —SO ₂ NH ₂ , —SO ₂ NHCOR (wherein M is a hydrogen atom) R represents an alkyl group having 1 to 12 carbon atoms, a phenyl group which may have a substituent, or a naphthyl group which may have a substituent. Can be mentioned. Among these, it is preferable to use those in which —COOM and —SO ₃ M are bonded to the surface of the color pigment.

  Further, “M” in the hydrophilic group includes, for example, lithium, sodium, potassium and the like as an alkali metal. Examples of the organic ammonium include mono to trimethyl ammonium, mono to triethyl ammonium, and mono to trimethanol ammonium. As a method of obtaining the anionically charged color pigment, as a method of introducing —COONa to the color pigment surface, for example, a method of oxidizing the color pigment with sodium hypochlorite, a method of sulfonation, a diazonium salt The method of making it react is mentioned.

  As the cationic hydrophilic group, for example, a quaternary ammonium group is preferable, and one in which any of these is bonded to the pigment surface is suitable as a coloring material.

  The method for producing the cationic self-dispersing carbon black to which the hydrophilic group is bonded is not particularly limited and may be appropriately selected depending on the intended purpose. For example, N— represented by the following structural formula Examples of the method for bonding the ethylpyridyl group include a method of treating carbon black with 3-amino-N-ethylpyridinium bromide.

The hydrophilic group may be bonded to the surface of carbon black through another atomic group. Examples of other atomic groups include an alkyl group having 1 to 12 carbon atoms, a phenyl group which may have a substituent, or a naphthyl group which may have a substituent. Specific examples of the case where the above-described hydrophilic group is bonded to the surface of carbon black via another atomic group include, for example, —C ₂ H ₄ COOM (where M represents an alkali metal, quaternary ammonium), -PhSO ₃ M (however, Ph is a phenyl group, M is an alkali metal, represents a quaternary _{ammonium), - C 5 H 10 NH} 3 + , and the like.

A pigment dispersion using a pigment dispersant can also be used for the ink used in the ink jet recording medium of the present invention.
As the pigment dispersant, as the hydrophilic polymer compound, in the natural system, plant polymers such as gum arabic, tragan gum, guar gum, karaya gum, locust bean gum, arabinogalactone, pectin, quince seed starch, alginic acid, Examples include seaweed polymers such as carrageenan and agar, animal polymers such as gelatin, casein, albumin and collagen, and microbial polymers such as xanthene gum and dextran. For semi-synthetic systems, cellulose polymers such as methylcellulose, ethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, carboxymethylcellulose, starch polymers such as sodium starch glycolate and sodium starch phosphate, sodium alginate, propylene glycol alginate And seaweed polymers such as Pure synthetic systems include polyvinyl polymers such as polyvinyl alcohol, polyvinyl pyrrolidone, and polyvinyl methyl ether, non-crosslinked polyacrylamide, polyacrylic acid or alkali metal salts thereof, acrylic resins such as water-soluble styrene acrylic resins, and water-soluble styrene malees. Acid resin, water-soluble vinyl naphthalene acrylic resin, water-soluble vinyl naphthalene maleic resin, polyvinyl pyrrolidone, polyvinyl alcohol, alkali metal salts of β-naphthalene sulfonic acid formalin condensate, cationic functional groups such as quaternary ammonium and amino groups Examples thereof include a polymer compound having a salt in the side chain and a natural polymer compound such as shellac. Among these, those having a carboxyl group introduced from a homopolymer of acrylic acid, methacrylic acid, styrene acrylic acid or a copolymer of other monomer having a hydrophilic group are particularly preferable as the polymer dispersant.
The weight average molecular weight of the copolymer is preferably 3,000 to 50,000, more preferably 5,000 to 30,000, and still more preferably 7,000 to 15,000.
The mixing mass ratio of the pigment and the dispersant (pigment: dispersant) is preferably 1: 0.06 to 1: 3, and more preferably 1: 0.125 to 1: 3.

  The amount of the colorant added to the ink is preferably 6 to 15% by mass, and more preferably 8 to 12% by mass. When the addition amount is less than 6% by mass, the image density may be lowered due to a decrease in coloring power, or feathering or bleeding may be deteriorated due to a decrease in viscosity. If the nozzle is left unattended, the nozzles will be easy to dry, non-ejection phenomenon will occur, the viscosity will be too high, the permeability will decrease, and the dots will not spread, so the image density will decrease. Or a blurred image.

(Wetting agent)
There is no restriction | limiting in particular as said wetting agent, According to the objective, it can select suitably, For example, at least 1 sort (s) selected from a polyol compound, a lactam compound, a urea compound, and saccharides is suitable.

  Examples of the polyol compound include polyhydric alcohols, polyhydric alcohol alkyl ethers, polyhydric alcohol aryl ethers, amides, amines, sulfur-containing compounds, propylene carbonate, and ethylene carbonate. These may be used alone or in combination of two or more.

Examples of the polyhydric alcohols include ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, 1,3-purpandiol, 1,3-butanediol, 1,4 butanediol, and 3-methyl- 1,3-butanediol, 1,3-propanediol, 1,5-pentanediol, 1,6 hexanediol, glycerol, 1,2,6-hexanetriol, 1,2,4-butanetriol, 1,2, Examples include 3-butanetriol and petriol.
Examples of the polyhydric alcohol alkyl ethers include ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, and propylene glycol monoethyl ether. It is done.
Examples of the polyhydric alcohol aryl ethers include ethylene glycol monophenyl ether and ethylene glycol monobenzyl ether.
Examples of the nitrogen-containing heterocyclic compound include N-methyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone, 2-pyrrolidone, 1,3-dimethylimidazolidinone, and ε-caprolactam.
Examples of the amides include formamide, N-methylformamide, formamide, N, N-dimethylformamide and the like.
Examples of the amines include monoethanolamine, diethanolamine, triethanolamine, monoethylamine, diethylamine, and triethylamine.
Examples of the sulfur-containing compounds include dimethyl sulfoxide, sulfolane, thiodiethanol, and the like.

Examples of the lactam compound include at least one selected from 2-pyrrolidone, N-methyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone, and ε-caprolactam.
Examples of the urea compound include at least one selected from urea, thiourea, ethylene urea, and 1,3-dimethyl-2-imidazolidinone. In general, the amount of urea added to the ink is preferably 0.5 to 50% by mass, and more preferably 1 to 20% by mass.

Examples of the saccharide include monosaccharides, disaccharides, oligosaccharides (including trisaccharides and tetrasaccharides), polysaccharides, and derivatives thereof. Among these, glucose, mannose, fructose, ribose, xylose, arabinose, galactose, maltose, cellobiose, lactose, sucrose, trehalose, and maltotriose are preferable, and maltose, sorbitol, gluconolactone, and maltose are particularly preferable.
The polysaccharide means a saccharide in a broad sense and can be used to include substances widely existing in nature such as α-cyclodextrin and cellulose.
Examples of the saccharide derivatives include reducing sugars of the saccharides (for example, sugar alcohols (generally represented by HOCH ₂ (CHOH) _n CH ₂ OH (where n represents an integer of 2 to 5)). , Oxidized sugars (eg, aldonic acid, uronic acid, etc.), amino acids, thioic acids, etc. Among these, sugar alcohols are particularly preferable, and examples of the alcohol include maltitol, sorbit, and the like.

  Among these, glycerin, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, 1 from the viewpoint of obtaining excellent effects on solubility and prevention of poor jetting characteristics due to water evaporation , 3-butanediol, 2,3-butanediol, 1,4-butanediol, 3-methyl-1,3-butanediol, 1,3-propanediol, 1,5-pentanediol, tetraethylene glycol, 1 , 6-hexanediol, 2-methyl-2,4-pentanediol, polyethylene glycol, 1,2,4-butanetriol, 1,2,6-hexanetriol, thiodiglycol, 2-pyrrolidone, N-methyl- 2-pyrrolidone, N-hydroxyethyl-2- Pyrrolidone are preferred, glycerin, 3-methyl-1,3-butanediol, 2-pyrrolidone is particularly preferred.

  The content of the wetting agent in the ink is preferably 10 to 50% by mass, and more preferably 20 to 35% by mass. If the content is too small, the nozzle is likely to be dried and defective ejection of droplets may occur. If the content is too large, the ink viscosity is increased, and the proper viscosity range may be exceeded.

(Penetration agent)
As the penetrant, a water-soluble organic solvent such as a polyol compound or a glycol ether compound is used. In particular, at least one of a polyol compound having 8 or more carbon atoms and a glycol ether compound is preferably used.
If the polyol compound has less than 8 carbon atoms, sufficient penetrability cannot be obtained, and the recording medium is soiled during double-sided printing, or ink spreading on the recording medium is insufficient, resulting in poor pixel filling. In some cases, character quality and image density may decrease.
Examples of the polyol compound having 8 or more carbon atoms include 2-ethyl-1,3-hexanediol (solubility: 4.2% (25 ° C.)), 2,2,4-trimethyl-1,3-pentanediol. (Solubility: 2.0% (25 ° C.)) is preferable.

  The glycol ether compound is not particularly limited and may be appropriately selected depending on the intended purpose.For example, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, Examples include polyhydric alcohol alkyl ethers such as tetraethylene glycol monomethyl ether and propylene glycol monoethyl ether; polyhydric alcohol aryl ethers such as ethylene glycol monophenyl ether and ethylene glycol monobenzyl ether.

  There is no restriction | limiting in particular in the addition amount of the said penetrant, Although it can select suitably according to the objective, 0.1-20 mass% is preferable, and 0.5-10 mass% is more preferable.

(Surfactant)
There is no restriction | limiting in particular as said surfactant, According to the objective, it can select suitably, For example, anionic surfactant, nonionic surfactant, amphoteric surfactant, fluorine type surfactant etc. are mentioned. .

  Examples of the anionic surfactant include polyoxyethylene alkyl ether acetate, dodecyl benzene sulfonate, laurate, polyoxyethylene alkyl ether sulfate salt, and the like.

Examples of the nonionic surfactant include acetylene glycol surfactants, polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, polyoxyethylene alkyl esters, polyoxyethylene sorbitan fatty acid esters, and the like.
Examples of the acetylene glycol surfactant include 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 3,6-dimethyl-4-octyne-3,6-diol, , 5-dimethyl-1-hexyn-3-ol and the like. Examples of commercially available acetylene glycol surfactants include Surfynol 104, 82, 465, 485, and TG manufactured by Air Products (USA).

  Examples of the amphoteric surfactant include lauryl aminopropionate, lauryl dimethyl betaine, stearyl dimethyl betaine, and lauryl dihydroxyethyl betaine. Specific examples include lauryl dimethylamine oxide, myristyl dimethylamine oxide, stearyl dimethylamine oxide, dihydroxyethyl lauryl amine oxide, polyoxyethylene coconut oil alkyl dimethyl amine oxide, dimethyl alkyl (coconut) betaine, dimethyl lauryl betaine, and the like. It is done.

As the fluorine-based surfactant, the following general formula (A)
CF ₃ CF ₂ 2 (CF ₂ CF ₂ ) _m —CH ₂ CH ₂ O (CH ₂ CH ₂ O) _n H (A)
What is represented by these is suitable.
However, in formula (A), m represents an integer of 0 to 10, and n represents an integer of 1 to 40.

  Examples of the fluorosurfactant include a perfluoroalkyl sulfonic acid compound, a perfluoroalkyl carboxylic compound, a perfluoroalkyl phosphate compound, a perfluoroalkyl ethylene oxide adduct, and a perfluoroalkyl ether group in the side chain. And polyoxyalkylene ether polymer compounds. Among these, the polyoxyalkylene ether polymer compound having a perfluoroalkyl ether group in the side chain has a low foaming property, and the bioaccumulation property of a fluorine compound that has been regarded as a problem in recent years is low and highly safe. Particularly preferred.

Examples of the perfluoroalkyl sulfonic acid compound include perfluoroalkyl sulfonic acid, perfluoroalkyl sulfonate, and the like.
Examples of the perfluoroalkyl carboxylic compounds include perfluoroalkyl carboxylic acids and perfluoroalkyl carboxylic acid salts.
Examples of the perfluoroalkyl phosphate compound include perfluoroalkyl phosphate esters, perfluoroalkyl phosphate salts, and the like.
The polyoxyalkylene ether polymer compound having a perfluoroalkyl ether group in the side chain includes a polyoxyalkylene ether polymer having a perfluoroalkyl ether group in the side chain, and a polyoxyalkylene ether having a perfluoroalkyl ether group in the side chain. Examples thereof include a sulfate salt of a polymer and a salt of a polyoxyalkylene ether polymer having a perfluoroalkyl ether group in the side chain.
As counter ions of salts in these fluorosurfactants, Li, Na, K, NH ₄ , NH ₃ CH ₂ CH ₂ OH, NH ₂ (CH ₂ CH ₂ OH) ₂ , NH (CH ₂ CH ₂ OH) ₃ etc. are mentioned.

As said fluorosurfactant, what was synthesize | combined suitably may be used and a commercial item may be used.
As this commercial item, for example, Surflon S-111, S-112, S-113, S-121, S-131, S-132, S-141, S-145 (all manufactured by Asahi Glass Co., Ltd.), Fullrad FC -93, FC-95, FC-98, FC-129, FC-135, FC-170C, FC-430, FC-431 (all manufactured by Sumitomo 3M), MegaFuck F-470, F1405, F-474 (All manufactured by Dainippon Ink & Chemicals, Inc.), Zonyl TBS, FSP, FSA, FSN-100, FSN, FSO-100, FSO, FS-300, UR (all manufactured by DuPont), FT-110, FT- 250, FT-251, FT-400S, FT-150, FT-400SW (all manufactured by Neos Co., Ltd.), PF-151N (manufactured by Omninova), etc. I can get lost. Among these, Zonyl FS-300, FSN, FSN-100, and FSO (manufactured by DuPont) are particularly preferable from the viewpoints of reliability and color development improvement.

(Other ingredients)
The other components are not particularly limited and can be appropriately selected according to need. An ultraviolet absorber, an oxygen absorber, a light stabilizer, etc. are mentioned.

(Resin emulsion)
The resin emulsion is obtained by dispersing resin fine particles in water as a continuous phase, and may contain a dispersant such as a surfactant as necessary.
The content of resin fine particles as the dispersed phase component (content of resin fine particles in the resin emulsion) is generally preferably 10 to 70% by mass. Further, the particle diameter of the resin fine particles is preferably 10 to 1000 nm, more preferably 20 to 300 nm, particularly considering use in an ink jet recording apparatus.

The resin fine particle component of the dispersed phase is not particularly limited and may be appropriately selected according to the purpose. For example, acrylic resin, vinyl acetate resin, styrene resin, butadiene resin, styrene-butadiene resin , Vinyl chloride resins, acrylic styrene resins, acrylic silicone resins, and the like. Among these, acrylic silicone resins are particularly preferable.
As said resin emulsion, what was synthesize | combined suitably may be used and a commercial item may be used.
Examples of the commercially available resin emulsion include Microgel E-1002, E-5002 (styrene-acrylic resin emulsion, manufactured by Nippon Paint Co., Ltd.), and Boncoat 4001 (acrylic resin emulsion, manufactured by Dainippon Ink & Chemicals, Inc.). ), Boncoat 5454 (styrene-acrylic resin emulsion, manufactured by Dainippon Ink & Chemicals, Inc.), SAE-1014 (styrene-acrylic resin emulsion, manufactured by Nippon Zeon Co., Ltd.), Cybinol SK-200 (acrylic resin emulsion, Seiden Chemical Co., Ltd.), Primal AC-22, AC-61 (acrylic resin emulsion, manufactured by Rohm and Haas), Nanoacryl SBCX-2821, 3689 (acrylic silicone resin emulsion, Toyo Ink Co., Ltd.) Company Ltd.), # 3070 (methyl methacrylate polymer resin emulsion, manufactured by Mikuni Color Ltd.).

  The addition amount of the resin fine particle component in the resin emulsion in the ink is preferably 0.1 to 50% by mass, more preferably 0.5 to 20% by mass, and still more preferably 1 to 10% by mass. If the addition amount is less than 0.1% by mass, the effect of improving clogging resistance and ejection stability may not be sufficient, and if it exceeds 50% by mass, the storage stability of the ink may be reduced. There is.

The aminopropanediol compound is a water-soluble organic basic compound, and for example, an aminopropanediol derivative is suitable.
There is no restriction | limiting in particular as said aminopropanediol derivative, According to the objective, it can select suitably, For example, 1-amino-2,3-propanediol, 1-methylamino-2,3-propanediol, 2 -Amino-2-methyl-1,3-propanediol, 2-amino-2-ethyl-1,3-propanediol, etc., among which 2-amino-2-ethyl-1,3-propane Diols are particularly preferred.

  The addition amount of the aminopropanediol compound in the recording ink is preferably 0.01 to 10% by mass, more preferably 0.1 to 5.0% by mass, and still more preferably 0.1 to 2.0% by mass. . If the amount added is too large, disadvantages such as an increase in pH and an increase in viscosity may occur.

  Examples of the antiseptic / antifungal agent include 1,2-benzisothiazolin-3-one, sodium dehydroacetate, sodium sorbate, sodium 2-pyridinethiol-1-oxide, sodium benzoate, and sodium pentachlorophenol. Can be mentioned.

The pH adjusting agent is not particularly limited as long as the pH can be adjusted to 7 or more without adversely affecting the ink, and any substance can be used according to the purpose.
Examples of the pH adjusting agent include amines such as diethanolamine and triethanolamine, hydroxides of alkali metal elements such as lithium hydroxide, sodium hydroxide and potassium hydroxide; ammonium hydroxide and quaternary ammonium hydroxide. Quaternary phosphonium hydroxide, alkali metal carbonates such as lithium carbonate, sodium carbonate, potassium carbonate, and the like.

  Examples of the rust inhibitor include acidic sulfite, sodium thiosulfate, ammonium thiodiglycolate, diisopropylammonium nitrite, pentaerythritol tetranitrate, and dicyclohexylammonium nitrite.

Examples of the antioxidant include phenol-based antioxidants (including hindered phenol-based antioxidants), amine-based antioxidants, sulfur-based antioxidants, phosphorus-based antioxidants, and the like.
Examples of the phenol-based antioxidant (including hindered phenol-based antioxidant) include butylated hydroxyanisole, 2,6-di-tert-butyl-4-ethylphenol, stearyl-β- (3.5) -Di-tert-butyl-4-hydroxyphenyl) propionate, 2,2'-methylenebis (4-methyl-6-tert-butylphenol), 2,2'-methylenebis (4-ethyl-6-tert-butylphenol), 4,4′-Butylidenebis (3-methyl-6-tert-butylphenol), 3,9-bis [1,1-dimethyl-2- [β- (3-tert-butyl-4-hydroxy-5-methylphenyl) ) Propionyloxy] ethyl] 2,4,8,10-tetrixaspiro [5,5] undecane, 1,1,3-tris (2-methyl-4- Hydroxy-5-tert-butylphenyl) butane, 1,3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene, tetrakis [methylene-3- (3 ′, 5′-di-tert-butyl-4′-hydroxyphenyl) propionate] methane, and the like.

Examples of the amine-based antioxidant include phenyl-β-naphthylamine, α-naphthylamine, N, N′-di-sec-butyl-p-phenylenediamine, phenothiazine, N, N′-diphenyl-p-phenylenediamine. 2,6-di-tert-butyl-p-cresol, 2,6-di-tert-butylphenol, 2,4-dimethyl-6-tert-butyl-phenol, butylhydroxyanisole, 2,2′-methylenebis ( 4-methyl-6-tert-butylphenol), 4,4′-butylidenebis (3-methyl-6-tert-butylphenol), 4,4′-thiobis (3-methyl-6-tert-butylphenol), tetrakis [methylene -3 (3,5-di-tert-butyl-4-dihydroxyphenyl) propionate] methane, 1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, and the like.
Examples of the sulfur-based antioxidant include dilauryl 3,3′-thiodipropionate, distearyl thiodipropionate, lauryl stearyl thiodipropionate, dimyristyl 3,3′-thiodipropionate, distearyl β. , β′-thiodipropionate, 2-mercaptobenzimidazole, dilauryl sulfide and the like.
Examples of the phosphorus antioxidant include triphenyl phosphite, octadecyl phosphite, triisodecyl phosphite, trilauryl trithiophosphite, trinonyl phenyl phosphite, and the like.

Examples of the ultraviolet absorber include benzophenone ultraviolet absorbers, benzotriazole ultraviolet absorbers, salicylate ultraviolet absorbers, cyanoacrylate ultraviolet absorbers, and nickel complex salt ultraviolet absorbers.
Examples of the benzophenone-based ultraviolet absorber include 2-hydroxy-4-n-octoxybenzophenone, 2-hydroxy-4-n-dodecyloxybenzophenone, 2,4-dihydroxybenzophenone, and 2-hydroxy-4-methoxybenzophenone. 2,2 ′, 4,4′-tetrahydroxybenzophenone, and the like.
Examples of the benzotriazole ultraviolet absorber include 2- (2′-hydroxy-5′-tert-octylphenyl) benzotriazole, 2- (2′-hydroxy-5′-methylphenyl) benzotriazole, 2- (2′-hydroxy-4′-octoxyphenyl) benzotriazole, 2- (2′-hydroxy-3′-tert-butyl-5′-methylphenyl) -5-chlorobenzotriazole, and the like.
Examples of the salicylate-based ultraviolet absorber include phenyl salicylate, p-tert-butylphenyl salicylate, p-octylphenyl salicylate, and the like.
Examples of the cyanoacrylate ultraviolet absorber include ethyl-2-cyano-3,3′-diphenyl acrylate, methyl-2-cyano-3-methyl-3- (p-methoxyphenyl) acrylate, and butyl-2- And cyano-3-methyl-3- (p-methoxyphenyl) acrylate.
Examples of the nickel complex ultraviolet absorber include nickel bis (octylphenyl) sulfide, 2,2′-thiobis (4-tert-octylferrate) -n-butylamine nickel (II), 2,2′-thiobis. (4-tert-octyl ferrate) -2-ethylhexylamine nickel (II), 2,2′-thiobis (4-tert-octyl ferrate) triethanolamine nickel (II), and the like.

  The ink used in the ink jet recording medium of the present invention has at least water, a colorant, and a wetting agent, and if necessary, a penetrating agent, a surfactant, and other components as necessary dispersed or dissolved in an aqueous medium. Further, it is manufactured by stirring and mixing as necessary. The dispersion can be performed by, for example, a sand mill, a homogenizer, a ball mill, a paint shaker, an ultrasonic disperser, etc., and stirring and mixing are performed by a stirrer using a normal stirring blade, a magnetic stirrer, a high-speed disperser, or the like. be able to.

In consideration of image quality such as character quality, the viscosity of the ink is preferably 2 mPa · s or more, more preferably 3 to 20 mPa · s, and particularly preferably 5 to 20 mPa · s at 25 ° C. Furthermore, when the viscosity exceeds 20 mPa · s, it may be difficult to ensure ejection stability.
The pH of the ink is preferably 7 to 10, for example.
Higher concentrations and viscosities of inks are preferable because solidification is accelerated and feathering, bleeding, and cockling are less likely to occur. Also, when solidification is fast, more color material is likely to be present on the recording medium than in the recording medium, and the print density is increased. On the other hand, spur marks are likely to appear when printing on a recording medium with relatively low ink absorbency, but this can be reduced when printing on the ink jet recording medium of the present invention.

  There is no restriction | limiting in particular as coloring of the said ink, According to the objective, it can select suitably, Yellow, magenta, cyan, black etc. are mentioned. When recording is performed using an ink set in which two or more of these colorings are used in combination, a multicolor image can be formed. When recording is performed using an ink set in which all colors are combined, a full color image is formed. be able to.

<Example>
EXAMPLES Hereinafter, although an Example demonstrates this invention further in full detail, this invention is not limited by this. Unless otherwise specified, “part” and “%” described below represent “part by mass” and “% by mass”, respectively.
The volume-based particle size distribution of kaolin measured by the laser diffraction method is as follows. Laser particle size analyzer (Malvern Mastersizer type S, red light source is 633 nm (He-Ne laser), blue light is 466 nm ( LED)). As a method for measuring the particle size distribution, a sample slurry containing kaolin in pure water was dropped and mixed to obtain a uniform dispersion, and charged into a measuring machine.
Further, the average particle size and volume-based particle size distribution of kaolin measured by the sedimentation method were measured by a sedimentation method particle size measuring device (Sedigraph 5100 manufactured by Micromeritics). As a method for measuring the particle size distribution, a sample slurry containing kaolin in pure water was dropped and mixed to obtain a uniform dispersion, and charged into a measuring machine.

(Preparation of base paper)
70% by weight of hardwood bleached kraft pulp (freeness 480 ml) and 30% by weight of softwood bleached kraft pulp (freeness 500 ml) were mixed. On the other hand, cationized starch was added 0.5% to pulp. A ketene dimer was added to 0.05% pulp, a sulfuric acid band was added to 2% pulp, and calcium carbonate was added to 10% pulp to obtain a paper stock. Using this stock, a web was formed with a long paper machine, dried by performing a three-stage wet press, and then machine calendered to obtain a base paper having a basis weight of 80 g / m ² .

Kaolin A (Product name: Capim DG, manufactured by Rio Capim, a ratio of particles of 0.4 μm or more and less than 4.2 μm in a volume-based integrated value measured by a laser method: 71%, particles having a particle diameter of less than 0.4 μm Ratio: 18%, ratio of particles having a particle diameter of 4.2 μm or more: 11%), 2 parts of SB latex (glass transition temperature 15 ° C.) serving as a binder, and acetoacetylated polyvinyl alcohol A (Gosefimer Z100, Made by Nippon Synthetic Chemical Industry Co., Ltd., saponification degree of 98.5 mol% or more, polymerization degree of about 1100) 2 parts, sodium hydroxide 0.1 part, sodium acrylate 0.2 part as a dispersant and diluting water are mixed to form a solid A paint of 64% min was obtained.
This paint was coated on both sides of the base paper using a blade coater so that the coating amount per side was 13 g / m ² . After coating, the paper was dried until the moisture content in the paper reached 5%, and subjected to supercalendering to obtain an ink jet recording medium. Supercalendering is performed by setting the surface temperature of a metal roll (hereinafter referred to as a heat roll) to 55 ° C., the white paper glossiness at a light incident angle of 75 degrees according to JIS Z8741 is 61%, and the clamping pressure is set to 1000 kPa according to JIS P8151, and the hard backing is performed. The linear pressure was adjusted so that the surface roughness of the ink receiving layer was 0.9 μm. In all of the following Examples and Comparative Examples, supercalender treatment was performed so that the surface of the ink receiving layer was in contact with the metal roll (heat roll).

100 parts of kaolin A, 2 parts of SB latex serving as a binder (glass transition temperature 15 ° C.) and acetoacetylated polyvinyl alcohol B (Gosefimer Z200, manufactured by Nippon Synthetic Chemical Industry Co., Ltd., saponification degree 99 mol% or more, polymerization degree about 600) 2 Parts of sodium hydroxide, 0.1 part of sodium hydroxide, 0.2 part of sodium polyacrylate as a dispersing agent and dilution water were mixed to obtain a paint having a solid content of 64%.
This paint was coated on both sides of the base paper using a blade coater so that the coating amount per side was 13 g / m ² . After coating, the paper was dried until the moisture content in the paper reached 5%, and subjected to supercalendering to obtain an ink jet recording medium. The super calendar is performed at room temperature, the blank paper glossiness at a light incident angle of 75 degrees based on JIS Z8741 is 60%, and the surface roughness of the ink receiving layer is 0.9 μm when using a hard backing with a clamping pressure of 1000 kPa according to JIS P8151. The linear pressure was adjusted so that

100 parts of kaolin B (product name: Amazon Plus, manufactured by CADAM, average particle diameter 0.26 μm measured by sedimentation method, ratio of 98.4% of particles having a volume-based integrated value of 2.0 μm or less) 100 parts, binder 3 parts of SB latex (glass transition temperature 15 ° C.), 2 parts of acetoacetylated polyvinyl alcohol B, 0.1 part of sodium hydroxide, 0.2 part of sodium polyacrylate as a dispersant and diluting water are mixed to obtain a solid content. 64% paint was obtained.
This paint was coated on both sides of the base paper using a blade coater so that the coating amount per side was 13 g / m ² . After coating, the paper was dried until the moisture content in the paper reached 5%, and subjected to supercalendering to obtain an ink jet recording medium. The supercalender treatment is performed with the surface temperature of the heat roll set at 55 ° C., the glossiness of the blank paper at a light incident angle of 75 degrees based on JIS Z8741 is 66%, and the ink is used when using a hard backing with a clamping pressure of 1000 kPa according to JIS P8151. The linear pressure was adjusted so that the surface roughness of the receiving layer was 0.9 μm.

Kaolin C (product name: KCS, manufactured by Imeris Co., Ltd., the proportion of particles of 0.4 μm or more and less than 4.2 μm in volume-based integrated value measured by laser diffraction method: 53%, particles having a particle diameter of less than 0.4 μm) Ratio: 21%, ratio of particles having a particle diameter of 4.2 μm or more: 26%) 100 parts, 2 parts of SB latex (glass transition temperature 15 ° C.) serving as binder, 2 parts of acetoacetylated polyvinyl alcohol B, sodium hydroxide 0 .1 part, 0.2 part of sodium polyacrylate as a dispersant and dilution water were mixed to obtain a coating material having a solid content of 64%.
This paint was coated on both sides of the base paper using a blade coater so that the coating amount per side was 13 g / m ² . After coating, the paper was dried until the moisture content in the paper reached 5%, and subjected to supercalendering to obtain an ink jet recording medium. The supercalender treatment is performed with the surface temperature of the heat roll set at 55 ° C., the white paper glossiness at a light incident angle of 75 degrees based on JIS Z8741 is 58%, and the ink is used when a hard pressure is used with a clamp pressure of 1000 kPa according to JIS P8151. The linear pressure was adjusted so that the surface roughness of the receiving layer was 0.9 μm.

Kaolin D (Product name: Huber Prime 4000, manufactured by J.M.HUBER, average particle diameter of 0.88 μm by sedimentation method, 82.5% ratio of particles of 2.0 μm or less by volume-based integrated value) 100 parts 2 parts of SB latex (glass transition temperature 15 ° C.) as a binder, 2 parts of acetoacetylated polyvinyl alcohol B, 0.1 part of sodium hydroxide, 0.2 part of sodium polyacrylate as a dispersing agent and diluting water were mixed. A paint having a solid content of 64% was obtained.
This paint was coated on both sides of the base paper using a blade coater so that the coating amount per side was 13 g / m ² . After coating, the paper was dried until the moisture content in the paper reached 5%, and subjected to supercalendering to obtain an ink jet recording medium. The supercalender treatment is performed with the surface temperature of the heat roll set at 55 ° C., the white paper glossiness at a light incident angle of 75 degrees based on JIS Z8741 is 57%, and the ink is used when a hard pressure is used with a clamping pressure of 1000 kPa according to JIS P8151. The linear pressure was adjusted so that the surface roughness of the receiving layer was 0.9 μm.

  An ink jet recording medium was obtained in exactly the same manner as in Example 2 except that the super calendar process was not performed. The white paper glossiness at a light incident angle of 75 degrees based on JIS Z8741 was 27%.

  An ink jet recording medium was obtained in exactly the same manner as in Example 3 except that the super calendar process was not performed. The white paper glossiness at a light incident angle of 75 degrees based on JIS Z8741 was 31%.

  An ink jet recording medium was obtained in exactly the same manner as in Example 4 except that the super calendar process was not performed. The white paper glossiness at a light incident angle of 75 degrees based on JIS Z8741 was 27%.

100 parts of kaolin A, 10 parts of acetoacetylated polyvinyl alcohol A serving as a binder, 0.1 part of sodium hydroxide, 0.2 part of sodium polyacrylate as a dispersant and dilution water were mixed to obtain a paint having a solid content of 50%. .
This paint was coated on both sides of the base paper using a blade coater so that the coating amount per side was 13 g / m ² . After coating, the ink was dried until the moisture content in the paper reached 5% to obtain an ink jet recording medium. The white paper glossiness at a light incident angle of 75 degrees based on JIS Z8741 was 26%, and the surface roughness of the ink receiving layer was 2.2 μm when a hard pressure was used with a clamp pressure of 1000 kPa according to JIS P8151.

100 parts of kaolin A, 1 part of acetoacetylated polyvinyl alcohol B serving as a binder, 0.1 part of sodium hydroxide, 0.2 part of sodium polyacrylate as a dispersant and dilution water were mixed to obtain a paint having a solid content of 65%. .
This paint was coated on both sides of the base paper using a blade coater so that the coating amount per side was 13 g / m ² . After coating, the paper was dried until the moisture content in the paper reached 5%, and subjected to supercalendering to obtain an ink jet recording medium. The supercalender treatment is performed with the surface temperature of the heat roll being 55 ° C., the white paper glossiness at a light incident angle of 75 degrees according to JIS Z8741 is 70%, and the ink is used when a hard pressure is used with a clamping pressure of 1000 kPa according to JIS P8151. The linear pressure was adjusted so that the surface roughness of the receiving layer was 0.7 μm.

<Comparative Example 1>
100 parts of kaolin A, 3 parts of SB latex as a binder (glass transition temperature 15 ° C.) and 1 part of oxidized starch (Mermaid 210, manufactured by Shikishima Starch Co., Ltd.), 0.1 part of sodium hydroxide, sodium polyacrylate as a dispersant Two parts and dilution water were mixed to obtain a paint having a solid content of 64%.
This paint was coated on both sides of the base paper using a blade coater so that the coating amount per side was 13 g / m ² . After coating, the paper was dried until the moisture content in the paper reached 5%, and subjected to supercalendering to obtain an ink jet recording medium. Ink when the surface temperature of the heat roll is 55 ° C., the blank paper glossiness at a light incident angle of 75 degrees is 58% based on JIS Z8741, and the clamping pressure is 1000 kPa according to JIS P8151 and the hard backing is used. The linear pressure was adjusted so that the surface roughness of the receiving layer was 0.9 μm.

<Comparative Example 2>
100 parts of kaolin A, 2 parts of SB latex as a binder (glass transition temperature 15 ° C.) and 2 parts of polyvinyl alcohol A (PVA-103, manufactured by Kuraray Co., Ltd., saponification degree 98 to 99 mol%, polymerization degree about 300), sodium hydroxide 0 .1 part, 0.2 part of sodium polyacrylate as a dispersant and dilution water were mixed to obtain a coating material having a solid content of 64%.
This paint was coated on both sides of the base paper using a blade coater so that the coating amount per side was 13 g / m ² . After coating, the paper was dried until the moisture content in the paper reached 5%, and subjected to supercalendering to obtain an ink jet recording medium. The supercalender treatment is performed with the surface temperature of the heat roll set at 55 ° C., the white paper glossiness at a light incident angle of 75 degrees based on JIS Z8741 is 57%, and the ink is used when a hard pressure is used with a clamping pressure of 1000 kPa according to JIS P8151. The linear pressure was adjusted so that the surface roughness of the receiving layer was 0.9 μm.

<Comparative Example 3>
100 parts of kaolin A, 2 parts of SB latex as a binder (glass transition temperature 15 ° C.) and 2 parts of polyvinyl alcohol B (PVA-105, manufactured by Kuraray Co., Ltd., saponification degree 98-99 mol%, polymerization degree about 500), sodium hydroxide 0 .1 part, 0.2 part of sodium polyacrylate as a dispersant and dilution water were mixed to obtain a coating material having a solid content of 64%.
This paint was coated on both sides of the base paper using a blade coater so that the coating amount per side was 13 g / m ² . After coating, the paper was dried until the moisture content in the paper reached 5%, and subjected to supercalendering to obtain an ink jet recording medium. The supercalender treatment is performed with the surface temperature of the heat roll set at 55 ° C., the blank paper glossiness at a light incident angle of 75 degrees based on JIS Z8741 is 60%, and the ink is used when using a hard backing with a clamping pressure of 1000 kPa according to JIS P8151. The linear pressure was adjusted so that the surface roughness of the receiving layer was 0.9 μm.

<Comparative Example 4>
100 parts of kaolin A, 2 parts of SB latex as a binder (glass transition temperature 15 ° C.) and 2 parts of polyvinyl alcohol C (PVA-110, manufactured by Kuraray Co., Ltd., saponification degree 98 to 99 mol%, polymerization degree about 1000), sodium hydroxide 0 .1 part, 0.2 part of sodium polyacrylate as a dispersant and dilution water were mixed to obtain a coating material having a solid content of 64%.
This paint was coated on both sides of the base paper using a blade coater so that the coating amount per side was 13 g / m ² . After coating, the paper was dried until the moisture content in the paper reached 5%, and subjected to supercalendering to obtain an ink jet recording medium. The supercalender treatment is performed with the surface temperature of the heat roll set at 55 ° C., the blank paper glossiness at a light incident angle of 75 degrees based on JIS Z8741 is 60%, and the ink is used when using a hard backing with a clamping pressure of 1000 kPa according to JIS P8151. The linear pressure was adjusted so that the surface roughness of the receiving layer was 0.9 μm.

<Comparative Example 5>
Mixing 100 parts of kaolin A, 0.3 part of acetoacetylated polyvinyl alcohol B as a binder, 0.1 part of sodium hydroxide, 0.2 part of sodium polyacrylate as a dispersing agent and diluting water to prepare a paint having a solid content of 65% Obtained.
This paint was coated on both sides of the base paper using a blade coater so that the coating amount per side was 13 g / m ² . After coating, the paper was dried until the moisture content in the paper reached 5%, and subjected to supercalendering to obtain an ink jet recording medium. The supercalender treatment is performed with the surface temperature of the heat roll being 55 ° C., the white paper glossiness at a light incident angle of 75 degrees according to JIS Z8741 is 70%, and the ink is used when a hard pressure is used with a clamping pressure of 1000 kPa according to JIS P8151. The linear pressure was adjusted so that the surface roughness of the receiving layer was 0.7 μm.

<Comparative Example 6>
100 parts of kaolin A, 11 parts of SB latex (glass transition temperature 15 ° C.) serving as a binder, 2 parts of acetoacetylated polyvinyl alcohol B, 0.1 part of sodium hydroxide, 0.2 part of sodium polyacrylate as a dispersant and dilution water By mixing, a paint having a solid content of 50% was obtained.
This paint was coated on both sides of the base paper using a blade coater so that the coating amount per side was 13 g / m ² . After coating, the paper was dried until the moisture content in the paper reached 5%, and subjected to supercalendering to obtain an ink jet recording medium. The supercalender treatment is performed with the surface temperature of the heat roll set at 55 ° C., the blank paper glossiness at a light incident angle of 75 degrees based on JIS Z8741 is 60%, and the ink is used when using a hard backing with a clamping pressure of 1000 kPa according to JIS P8151. The linear pressure was adjusted so that the surface roughness of the receiving layer was 1.0 μm.

<Evaluation>
1. Blank paper glossiness According to JIS Z8741, the blank paper glossiness (light incident angle of 75 degrees) on the surface of the ink receiving layer was measured using a glossmeter (manufactured by Murakami Color Research Laboratory, True GLOSS GM-26PRO).
2. Inkjet printing quality Printing was performed using the following commercially available pigment inkjet printers, and printing evaluation was performed according to the following evaluation methods.
Evaluation printer: Ricoh, IPSiO GX5000, "Glossy paper / High speed" mode

2-1. Solid print unevenness Using the above evaluation printer, a green solid rectangle was printed, and the print density unevenness was visually observed and evaluated according to the following criteria.
(Double-circle): There is no unevenness of printing density and it is a very good level.
○: There is almost no unevenness in the print density, which is a good level.
Δ: There is a slight unevenness in the print density, but there is no practical problem.
X: Print density unevenness is conspicuous and is not practical.
2-2. Water resistance Using the evaluation printer, a thick straight line was printed on each colored solid part, and rubbed with a cotton swab 24 hours after printing, and water resistance was evaluated according to the following criteria.
○: The printed part hardly falls even when rubbed, and the level is good.
Δ: The printed part slightly falls when rubbed, but it is at a level where there is no practical problem.
X: The printed part falls when rubbed, and it is a level that cannot withstand practical use.

2-3. Spur Marks Using the above printer, a green solid rectangle was printed, and a white spot defect in the printed part due to the spur after paper discharge from the printer was visually observed and evaluated according to the following criteria.
○: Almost no white defect and a good level.
Δ: There is a slight white defect, but there is no practical problem.
X: White defect is conspicuous and is a level that cannot be put to practical use 2-4. Surface Strength After sticking the adhesive tape on the white paper portion of each inkjet recording medium and bringing it into close contact, the adhesive tape was peeled off and the surface of the ink receiving layer was visually observed and evaluated according to the following criteria.
A: Almost no removal of the ink receiving layer surface, which is a good level.
Δ: The surface of the ink receiving layer is slightly removed, but it is at a level that causes no practical problems.
X: The ink-receptive layer surface is conspicuous and is not practically usable.

2-5. Texture of matte coated paper for offset printing A predetermined pattern was inkjet printed using the evaluation printers 1 and 2 described above. The same pattern as this was offset printed on matte coated paper for offset printing (Ulite Ultra S: manufactured by Nippon Paper Industries Co., Ltd., basis weight 90.0 g / m 2). The appearance and feel of the inkjet print were compared with the offset print and evaluated according to the following criteria.
○: The texture such as appearance and touch is close to the matte coated paper for offset printing, and has a texture of offset printed matter.
×: Unlike the offset-printed matte coated paper, the texture such as appearance and touch is not the texture of the offset printed matter.

2-6. Glossy coated paper texture for offset printing A predetermined pattern was inkjet printed using the evaluation printers 1 and 2 described above. The same pattern as this was offset printed on glossy coated paper for offset printing (Aurora Coat: Nippon Paper Industries, Ltd., basis weight 104.7 g / m 2). The appearance and feel of the inkjet print were compared with the offset print and evaluated according to the following criteria.
○: The texture such as appearance and feel is close to the glossy coated paper for offset printing, and has the texture of offset printed matter.
X: Unlike the glossy coated paper for offset printing, the texture such as appearance and touch is not the texture of the offset printed matter.

  The obtained results are shown in Table 1.

As is apparent from Table 1, in the case of each of the examples, there was little printing unevenness in the solid portion, water resistance and excellent effect of reducing spur marks were satisfied, and various printing qualities were satisfied in a well-balanced manner. A paper texture was also obtained.
In the case of Examples 4 and 8, in which particles of 0.4 μm or more and less than 4.2 μm used less than 64% of kaolin as a pigment of the ink receiving layer as measured by the laser diffraction method, by volume-based integrated value, The ink absorptivity was slightly inferior to the other examples, and the printing unevenness was slightly inferior.
In addition, in the case of Example 5 using kaolin in which the average particle diameter measured by the sedimentation method is 0.15 μm or more and less than 0.50 μm, and particles having a diameter of 2.0 μm or less are 95% or less by volume-based integrated value However, the ink absorptivity was slightly inferior and the printing unevenness was slightly inferior.

On the other hand, in Comparative Examples 1 to 3 in which other binders were blended in place of acetoacetylated PVA, both the spur marks (white spots) and the water resistance of the printed part were inferior.
Moreover, in the case of the comparative example 4 which mix | blended PVA with a polymerization degree of 1000 instead of acetoacetylated PVA, the surface strength became strong and the spur mark was also favorable, but both the water resistance of the printing part was inferior. This is presumably because the binder component in the coating layer was swollen or dissolved by contact with water (water or a solvent component of water-based ink).
In Comparative Example 5 in which the blending ratio of acetoacetylated PVA to the inorganic pigment in the ink receiving layer was less than 0.5 parts by mass, both the surface strength and the water resistance of the printed part were inferior.
In the case of Comparative Example 6 in which the blending ratio of acetoacetylated PVA to the inorganic pigment of the ink receiving layer exceeded 10 parts by mass, solid printing unevenness occurred. This is presumably because the voids present in the ink receiving layer were filled with acetoacetylated PVA, and the ink absorbency was lowered.

Claims (5)

  A total of 100 parts by mass of all the inorganic pigments included in the ink receiving layer, having an ink receiving layer mainly composed of kaolin and acetoacetylated polyvinyl alcohol on one or both sides of the base paper mainly composed of wood pulp The inkjet recording medium whose ratio of the said acetoacetylated polyvinyl alcohol with respect to is 0.5 to 10 mass parts.   The total amount of all binder components contained in the ink receiving layer is 0.5 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass in total of all inorganic pigments contained in the ink receiving layer. The inkjet recording medium as described.   3. The ink jet recording medium according to claim 1, wherein the kaolin is kaolin in which particles of 0.4 μm or more and less than 4.2 μm occupy 64% or more by volume-based integrated value when measured by a laser diffraction method.   The kaolin is kaolin having an average particle diameter measured by a sedimentation method of 0.15 μm or more and less than 0.50 μm, and particles having a diameter of 2.0 μm or less occupy 95% or more by volume based integrated value. 2. An ink jet recording medium according to 2.   An ink jet recording method comprising: recording an image on an ink jet recording medium according to any one of claims 1 to 4 using an ink containing at least water, a particulate colorant, and a wetting agent.