JP6542558B2 - Ink jet recording medium - Google Patents

Description

  The present invention relates to an ink jet recording medium having an ink receiving layer provided on a substrate, and more particularly, the ink is excellent in ink drying property in ink jet printing with pigment ink, and has high definition image quality and high color development. The present invention also relates to an ink jet recording medium having a texture of offset printing type.

The ink jet recording method has been used in many applications with rapid improvement of printing performance because it is easy to achieve full color and noise in printing is small. These applications include, for example, document recording from document creation software, recording of digital images such as digital photographs, copying of beautiful printed materials such as silver salt photographs and books taken with a scanner, relatively small number of posters, etc. Image creation for
For these applications, ink jet recording media having a configuration suitable for each have been proposed. For example, when recording mainly characters, a plain paper type medium for directly recording on a paper substrate is used, and when it is desired to obtain higher image quality and high color development, an ink receiving layer is formed on the substrate A coated paper type medium provided by coating is used. In particular, when high glossiness comparable to silver salt photography is required, a cast paper type medium in which the outermost layer of a coated layer such as an ink receiving layer is formed by a cast coating method is used.

One of the developments in various fields of the ink jet recording system is the printing field. In the prior art, offset printing has been mainly used in this field, but this method requires making a printing plate. On the other hand, in the inkjet recording method, since it is not necessary to make a printing plate, it is easy to cope with small lot printing. In addition, there are merits such as continuous printing of variable information which is different for each part is possible, color adjustment and the like are easy, and it is not necessary to be skilled in the operation of the printing press.
Here, in consideration of substitution of the offset printing method by the ink jet recording method, the printed matter by the ink jet recording method is also required to have the same texture as the printed matter by the conventional offset printing method. Further, while the offset printing method tends to retain the ink on the surface of the medium, the ink jet recording method tends to cause the ink to penetrate into the medium, so that the color developability tends to be inferior as compared to the offset printing method.

In order to improve the color developability in the ink jet recording system, it is known to use a coated paper type ink jet recording medium as described above. In general, coated paper type inkjet recording media are coated with a bulky pigment having many voids such as silica, aluminum oxide (alumina) and an ink receiving layer mainly composed of a binder such as polyvinyl alcohol or starch on a substrate. By providing it, it is excellent in ink absorbability, and high definition image quality and high color development can be expressed. However, in addition to the fact that the texture is different from that of the offset printing recording medium in which pigments such as kaolin and clay are coated, there is a problem that the phenomenon that the ink receiving layer falls off from the substrate (powdering) easily occurs.
An inkjet recording sheet provided with an ink receiving layer containing non-spherical cationic colloidal silica on a substrate using a specific filler and a sizing agent in order to solve these problems in a coated paper type inkjet recording medium (patent document 1-3), a sheet for inkjet printing (patent document 4) in which the surface of a specific substrate is coated with a fine particle inorganic pigment of a composition mainly composed of aluminum oxide (alumina), calcium carbonate and clay on a support Patent Document 5 discloses an ink jet recording aptitude and offset printing aptitude which is provided with a coating layer comprising a white pigment containing and a binder containing an acrylamide / diallylamine type copolymer and a styrene-butadiene type copolymer. It is done.

  The present applicant has developed a technology in which a pigment in which engineered calcium carbonate in which light particle size distribution of light calcium carbonate is sharpened is blended with fine particles of kaolin is used as an ink receiving layer (Patent Document 6).

Japanese Patent Application Laid-Open No. 07-017126 Japanese Patent Application Laid-Open No. 07-017127 Japanese Patent Application Laid-Open No. 07-025131 JP 2001-246831 A Japanese Patent Application Publication No. 2004-082464 JP, 2009-234894, A

However, since the ink jet recording sheets described in Patent Documents 1 to 4 use very expensive materials such as colloidal silica and aluminum oxide (alumina) as pigments for the ink receiving layer, the ink jet recording sheets obtained are expensive. In addition to the above, the drying property of the ink at the time of ink jet printing is inferior, bleeding occurs in the printed image, or since the drying property of the ink is good but the spreading is insufficient, streaks of unprinted on the printed image In any case, high definition image quality can not be obtained due to the occurrence of a part (strike). Moreover, the texture is different from that of the recording medium for offset printing, and the gloss is not sufficient.
Since the recording paper described in Patent Document 5 uses calcium carbonate and clay as white pigments, the resulting recording paper is inexpensive and has an offset printing type texture. However, when an acrylamide / diallylamine type copolymer is used as a binder, the drying property of the ink at the time of inkjet printing using a pigment ink is particularly poor. In particular, when the content of the clay is large, the absorption of the ink is inhibited, so that the drying property of the ink at the time of ink jet printing is remarkably deteriorated, and it is not possible to obtain sufficient image quality and color development.
Further, in the case of the technology described in Patent Document 6, the texture of the gloss coated paper for offset printing is not considered, and the glossiness of the white paper is not sufficient as the gloss coated paper for offset printing.

  Accordingly, the present invention is an ink jet recording medium which is excellent in the drying property of ink particularly in ink jet printing with pigment ink, has high definition image quality and high color forming property, and has an offset printing type feeling and high gloss. It is to provide.

  As a result of intensive investigations, the present inventors incorporated engineered calcium carbonate, kaolin and an organic pigment in the ink receiving layer, and further, by using starch and copolymer latex as a binder, particularly in the case of ink jet printing with pigment ink. The inventors have found that the ink has excellent drying properties, high definition image quality and high color development, and that an offset printing type texture and high gloss can be obtained, and the present invention has been completed. In particular, in order to increase the gloss of the ink receiving layer, it is better to increase the amount of engineered calcium carbonate by increasing the amount of kaolin or organic pigment, but if the amount of kaolin or organic pigment is increased, the image quality and the ink drying properties are degraded. The respective blending amounts were specified in consideration.

That is, the ink jet recording medium of the present invention is an ink jet recording medium provided with an ink receiving layer containing an inorganic pigment and a starch and a copolymer latex on at least one surface of a substrate, and coated with the ink receiving layer The amount of processing is 10.0 g / m ² or more and 20.0 g / m ² or less per one side, the inorganic pigment contains engineered calcium carbonate and kaolin, and the engineered calcium carbonate is 50% by mass or more based on the total amount of the inorganic pigment It is less than 80% by mass, 10% by mass or more and less than 50% by mass of the kaolin, and further , 1 part by mass or more and 3 parts by mass or less of the starch in 100 parts by mass of the inorganic pigment in the ink receiving layer . the copolymer latex 5 parts by mass or more and 7 parts by weight, the glass transition point (Tg) of 1 part by mass or more organic pigments is 20 ° C. or higher Characterized in that it contains less 0 parts by weight.

The engineered calcium carbonate preferably has a 50% volume particle diameter (D50) measured by a laser light scattering method of 0.3 μm or more and 1.2 μm or less.
The ratio of particle size (D75 (μm)) of cumulative 75% by weight and particle size (D25 (μm)) of cumulative 25% by weight of the above-mentioned engineered calcium carbonate was measured by X-ray transmission sedimentation particle size distribution measurement. It is preferable that D75 / D25) is 3.0 or less.
It is preferable that the above-mentioned kaolin has a 50% volume average particle diameter (D50) measured by a laser light scattering method of 0.1 μm or more and 1.0 μm or less.
It is preferable that the said kaolin is 20 mass% or more and 40 mass% or less with respect to the said inorganic pigment whole quantity.
It is preferable that the said copolymer latex contains an acrylonitrile styrene butadiene type copolymer.
The white paper glossiness at a light incident angle of 75 degrees according to JIS Z8741 on the surface of the ink receiving layer is preferably 50% to 85%.

  According to the present invention, an ink jet recording medium which is excellent in the drying property of ink particularly in ink jet printing with pigment ink, has high definition image quality and high color forming property, and has offset printing type texture and high glossiness. can get.

The inkjet recording medium of the present invention is an inkjet recording medium provided with an ink receiving layer containing an inorganic pigment and a starch and a copolymer latex on at least one surface of a substrate,
The inorganic pigment contains engineered calcium carbonate and kaolin, and the engineered calcium carbonate is 50% by mass or more and less than 80% by mass, and the kaolin is 10% by mass or more and less than 50% by mass with respect to the total amount of the inorganic pigment. Furthermore, an organic pigment having a glass transition point (Tg) of 20 ° C. or higher is contained in an amount of 1 to 10 parts by mass with respect to 100 parts by mass of the inorganic pigment.

(Inorganic pigment)
In the present invention, the ink receiving layer contains an inorganic pigment. The inorganic pigments contained in the ink receiving layer include calcium carbonate, silica, kaolin, calcined kaolin, clay, calcium silicate, calcium sulfate, aluminum oxide (alumina), aluminum hydroxide, aluminum hydroxide, aluminum silicate, titanium oxide, zinc oxide, magnesium carbonate Known pigments such as magnesium silicate, talc and zeolite can be exemplified. It is also possible to use these in combination depending on the required quality.

(Engineered calcium carbonate)
In general, calcium carbonate is used to grind coarse particles to reduce the particle size, but depending on the grinding method, fine particles increase and the particle size distribution becomes broad. When calcium carbonate having a large amount of fine particles is used in the ink receiving layer, the fine particles are fitted into the voids of the ink receiving layer and the packing progresses, whereby the ink receiving layer becomes high in density and the drying property of the ink decreases. Image quality (bleeding) may be poor. Therefore, as described in the above-mentioned Patent Document 6, engineered calcium carbonate has been developed in which the particle size distribution of calcium carbonate is sharply engineered.
In the present invention, the content of engineered calcium carbonate is 50% by mass or more and less than 80% by mass with respect to the total amount of the inorganic pigment. In this case, the phenomenon (migration) that the binder in the coating liquid for the ink receiving layer penetrates the substrate hardly occurs, and the coating unevenness of the ink receiving layer is reduced, particularly in the case of inkjet printing with pigment ink. An excellent drying property of the ink and a high definition image quality can be obtained, and the receptive layer has a high coloring property. Furthermore, by setting the content of engineered calcium carbonate to 50% by mass or more, kaolin and clay are mainly used as compared with inkjet recording media mainly using bulky pigments such as silica and aluminum oxide (alumina). An ink jet recording medium having characteristics close to that of offset printing recording media mainly using pigments such as, that is, an offset printing type texture and high gloss, can be easily obtained.

In addition, when the content of engineered calcium carbonate is 50% by mass or more, it is easy to increase the concentration of the inorganic pigment slurry and, consequently, to increase the concentration of the coating liquid for the ink receiving layer, thereby drying the coating liquid. The load is small, and the inkjet recording medium can be manufactured at high speed. However, when the content of engineered calcium carbonate is 80% by mass or more, the absorbability of the ink becomes excessive and the image quality (through streaks) is inferior, so the content of engineered calcium carbonate is made less than 80% by mass.
Preferably, the amount of engineered calcium carbonate is 65% by mass or more and less than 80% by mass with respect to the total amount of the inorganic pigment.

  In the present invention, engineered calcium carbonate may be either engineered heavy calcium carbonate engineered with heavy calcium carbonate or engineered light calcium carbonate engineered with light calcium carbonate. If the content of the hard calcium carbonate is high, it is easy to increase the concentration of the slurry of the inorganic pigment, and it is further easy to increase the concentration of the coating liquid for the ink receiving layer, and the load on drying the coating liquid is small. It is preferable because an inkjet recording medium can be manufactured at high speed.

The particle size of engineered calcium carbonate used in the present invention is not particularly limited, but generally, the 50% volume average particle size (D50) measured by a laser light scattering method (laser diffraction method) is 0.3 μm or more and 1.2 μm or less It is good to use what is. In particular, when the D50 is 0.4 to 1.1 μm, the concentration increase of the pigment slurry and the coating liquid of the ink receiving layer is further facilitated, the coating unevenness of the ink receiving layer is further reduced, and the white paper glossiness is It is preferable because it is excellent. More preferably, D50 is 0.5 to 1.0 μm, and particularly preferably D50 is 0.6 to 0.9 μm.
The measurement of the particle size distribution by the laser light scattering method (laser diffraction method) utilizes the light scattering phenomenon, and is obtained by the Mie theory and the Fraunhofer approximation. However, since the method of calculating the particle size distribution from the scattered light differs depending on the particle size measuring machine, in the present invention, the laser method particle size measuring machine (Mastersizer S type manufactured by Malvern Co., Ltd., light source is red light 633 nm (He-Ne laser) , Blue light use the value measured by 466 nm (LED)).
Moreover, the measuring method of a particle size distribution uses what drip-mixed the sample slurry which contains calcium carbonate in a pure water, and was made into the uniform dispersion body for a sample.

Also, the engineered calcium carbonate used in the present invention has a cumulative 75% by weight particle diameter (D 75 (μm)) and a cumulative weight measured by X-ray transmission sedimentation particle size distribution measurement (X-ray transmission gravity sedimentation) It is preferable that (D75 / D25) which is a ratio of the particle diameter (D25 (μm)) of 25% by weight is 3.0 or less. The closer the D75 / D25 is to 1.0, the narrower the particle size distribution, ie, the sharper the peak.
The measurement of the particle size distribution by the X-ray transmission type particle size distribution measurement method adopts the liquid phase sedimentation method, and measures the particle diameter based on Stokes's law. In addition, the suspension during sedimentation is irradiated with X-rays, and the particle size distribution is measured from the amount of X-ray transmission according to Lambert-Beer's law.
In the present invention, a value measured by an X-ray transmission sedimentation particle size distribution measuring apparatus (Cedigraph 5100 manufactured by Micromeritics) is used.

(Kaolin)
In the present invention, the content of kaolin is 10% by mass or more and less than 50% by mass with respect to the total amount of the inorganic pigment. In this manner, the gloss of the ink receiving layer can be increased while securing the image quality and the ink drying property. When the content of kaolin is less than 10% by mass, it becomes difficult to increase the gloss of the ink receiving layer. When the content of kaolin is 50% by mass or more, the gloss of the ink receiving layer is increased, but the image quality and the ink drying property are reduced.
Preferably, kaolin is 20% by mass or more and 40% by mass or less with respect to the total amount of the inorganic pigment.
The particle diameter of kaolin is not particularly limited, but usually, the 50% volume average particle diameter (D50) measured by the laser light scattering method (laser diffraction method) is 0.1 μm or more from the viewpoint of the ink drying property and the gloss of the ink receiving layer. It is good to use what is 1.0 micrometer or less. In particular, it is preferable that the D50 is 0.3 to 0.8 μm because it is easy to increase the gloss of the ink receiving layer while securing the ink drying property.

(Organic pigment)
In the present invention, the ink receiving layer contains 1 part by mass or more and 10 parts by mass or less of an organic pigment having a glass transition point (Tg) of 20 ° C. or more based on 100 parts by mass of the inorganic pigment. The organic pigment has the effect of enhancing the gloss of the ink receiving layer, but the image quality is degraded when the content of the organic pigment exceeds 10% by mass with respect to the total amount of the inorganic pigment.
In addition, when the Tg of the organic pigment is less than 20 ° C., the drying property of the ink is poor. The upper limit of the Tg of the organic pigment is not particularly limited, but the upper limit of production is about 140 ° C.
As a specific example of the organic pigment, manufactured by Nippon Zeon, product name: LX407BP9 (polystyrene-based organic pigment is coated with styrene-butadiene copolymer latex, Tg: 60 ° C.), product name: LX407 BP6 (Tg: 75 ° C.) Product name: MH 8101 (Tg: 105 ° C.) and the like.
As described later, the ink receiving layer may contain various binders other than starch and copolymer latex, but the same compound as the organic pigment is not used for the binder. When the cross section of the ink receiving layer is observed with a scanning electron microscope or the like, the organic pigment is dispersed in the form of particles in the matrix of the ink receiving layer, so that it can be determined that the composition is different from the binder.

(binder)
In the present invention, the ink receiving layer contains a binder, which is mainly composed of starch and copolymer latex.

(starch)
In the present invention, as the above-mentioned starch, known starches used for general coated paper can be used without particular limitation, but enzyme-modified starch, thermochemically modified starch, oxidized starch, esterified starch, hydroxyethylated Various starches, such as etherified starches such as starches and cationized starches, can be exemplified. These starches can be used alone or in combination of two or more.
In the present invention, the blending amount of starch is based on 100 parts by mass of the inorganic pigment in order to improve the drying property of the ink at the time of ink jet printing with the pigment ink and to prevent the ink from spreading too much and bleeding. 0.5 parts by mass or more and 5 parts by mass or less.
When the blending amount of starch is less than 0.5 parts by mass, the water retentivity of the coating liquid for the ink receiving layer is insufficient, and the phenomenon (migration) in which the binder in the coating liquid penetrates to the substrate is likely to occur. As a result, the coating unevenness of the ink receiving layer becomes large, and partial streaks and bleeding occur during ink jet printing, resulting in a decrease in image quality. In addition, when the blending amount of starch exceeds 5 parts by mass, the drying property of the ink is lowered, and bleeding occurs to deteriorate the image quality.
When the blending amount of starch is 1 part by mass or more and 3 parts by mass or less, the image quality is further improved, which is preferable.

(Copolymer latex)
The copolymer latex used in the present invention includes acrylonitrile-butadiene copolymer, styrene-butadiene copolymer, conjugated diene copolymer latex such as methyl methacrylate butadiene copolymer, acrylic ester and methacrylic ester. Acrylic copolymer latex such as the copolymer of the above, and vinyl copolymer latex such as the ethylene-vinyl acetate copolymer and the vinyl chloride-vinyl acetate copolymer. Among these, conjugated diene copolymer latex is preferable from the viewpoint of good ink drying properties during ink jet recording with a pigment ink and sufficient spread of the ink, and an acrylonitrile butadiene copolymer and a styrene butadiene copolymer. Copolymers are more preferable, and acrylonitrile butadiene type copolymers are particularly preferable.

The copolymer latex in the present invention is a copolymer latex obtained by polymerizing at least (A) an aliphatic conjugated diene monomer and (B) another vinyl monomer copolymerizable therewith. It is good.
As the copolymer latex, for example, the component (A) is 1,3-butadiene, the component (B) is an aromatic vinyl compound (for example, styrene), an alkyl (meth) acrylate (for example, methyl methacrylate), or An acrylonitrile styrene butadiene type copolymer (NSBR) which is a vinyl cyanide compound (for example, acrylonitrile) is mentioned. The copolymer latex in the present invention is produced by copolymerizing the monomer mixture by a known polymerization method such as bulk polymerization, solution polymerization, suspension polymerization, emulsion polymerization and the like.

  It is preferable that 25 to 40 parts by mass of the component (A) and 50 to 74.5 parts by mass of the component (B) in 100 parts by mass of the total monomers, 30 to 40 parts by mass of the component (A), More preferably, the component (B) is 55 to 70 parts by mass. The above copolymer latex is obtained by copolymerizing at least the components (A) and (B), and when the monomer is composed of only the components (A) and (B), the total of single copolymer latex is obtained. The mer is the total amount of the (A) component and the (B) component. On the other hand, when the above-mentioned copolymer latex contains other monomer components in addition to the (A) component and the (B) component, all the monomers are the (A) component, the (B) component and the other single components. It is the total amount of body components.

(Aliphatic conjugated diene monomer)
Examples of the (A) aliphatic conjugated diene monomer include 1,3-butadiene, isoprene, 2-chloro-1,3-butadiene, chloroprene, 2,3-dimethyl-1,3-butadiene and the like. is there. Preferably, it is 1,3-butadiene, isoprene, more preferably 1,3-butadiene. These aliphatic conjugated diene monomers may be used alone or in combination of two or more.

(Other vinyl monomers that can be copolymerized)
(B) As another vinyl-based monomer which can be copolymerized, aromatic vinyl compounds, alkyl (meth) acrylates, vinyl cyanide compounds, vinyl acetate, acrylamide compounds, N-methylol acrylamide, ethylenically unsaturated carboxylic acids An acid monomer etc. can be illustrated.

Examples of the aromatic vinyl compound include styrene, α-methylstyrene, p-methylstyrene, vinyl toluene, chlorostyrene and the like. Preferably it is styrene.
In addition, as the alkyl (meth) acrylate of the present invention, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate , Benzyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, isobornyl (meth) acrylate, 2-cyanoethyl (meth) acrylate, glycidyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, etc. It is possible. Preferred are methyl (meth) acrylate and ethyl (meth) acrylate, and more preferred is methyl (meth) acrylate.
Moreover, an acrylonitrile, methacrylonitrile etc. can be illustrated as a cyanidated vinyl compound. More preferably, it is acrylonitrile.
Moreover, acrylamide, N, N- dimethylaminopropyl (meth) acrylamide etc. can be illustrated as an acrylamide type compound.
Further, as the ethylenically unsaturated carboxylic acid monomer, monocarboxylic acids such as acrylic acid, methacrylic acid and crotonic acid, dicarboxylic acids such as maleic acid, fumaric acid and itaconic acid, methyl maleate, methyl itaconate, β -A half ester such as methacryloxyethyl acid hexahydrophthalate can be exemplified. Preferred are acrylic acid and methacrylic acid.
The other copolymerizable vinyl monomers as the component (B) can be used singly or in combination of two or more. When mixing 2 or more types, it is preferable to use at least the ethylenically unsaturated carboxylic acid monomer in them which are mixed.

In the present invention, in order to improve the drying property of the ink at the time of ink jet printing with the pigment ink, and to spread the ink sufficiently and to prevent the generation of streaky non-printing portions (striations) in the printed image The blending amount of the united latex is 3 parts by mass to 9 parts by mass with respect to 100 parts by mass of the inorganic pigment. It is preferable to be 5 parts by mass or more and 7 parts by mass or less.
If the blending amount of the copolymer latex is less than 3 parts by mass, the ink does not spread sufficiently at the time of ink jet printing, so that an unprinted portion (stripe) occurs and the image quality is deteriorated. When the blending amount of the copolymer latex exceeds 9 parts by mass, the spreading of the ink is excessive, the drying property of the ink is lowered, and bleeding occurs to deteriorate the image quality.

(Others)
The ink receiving layer may optionally contain various binders other than starch and copolymer latex.
As these various binders, known binders used for general coated paper can be used and are not particularly limited, but completely saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, acetoacetylated polyvinyl alcohol, carboxy modified polyvinyl Alcohol, amide modified polyvinyl alcohol, sulfonic acid modified polyvinyl alcohol, butyral modified polyvinyl alcohol, olefin modified polyvinyl alcohol, nitrile modified polyvinyl alcohol, pyrrolidone modified polyvinyl alcohol, silicone modified polyvinyl alcohol, silanol modified polyvinyl alcohol, cation modified polyvinyl alcohol, terminal alkyl Polyvinyl alcohols such as modified polyvinyl alcohol; hydroxyethyl cellulose, methyl cellulose Cellulose ethers such as loin, ethyl cellulose, carboxymethyl cellulose and acetyl cellulose and derivatives thereof; polyacrylamides such as polyacrylamide, cationic polyacrylamide, anionic polyacrylamide and amphoteric polyacrylamide; polyester polyurethane resin, polyether polyurethane resin, Urethane resin such as polyurethane ionomer resin; unsaturated polyester resin, polyvinyl acetate, vinyl chloride-vinyl acetate copolymer, polyvinyl chloride, polyvinylidene chloride, polyacrylic ester, casein, gelatin, arabic gum, polyvinyl butyral, To exemplify polystyrene and copolymers thereof, silicone resin, petroleum resin, terpene resin, ketone resin, coumarone resin, etc. It can be. These may be used in combination.
In the present invention, when the ink receiving layer contains the above-mentioned various binders other than starch and copolymer latex, 100 parts by mass of the total binder (total of starch and copolymer latex and the above various binders) contained in the ink receiving layer. On the other hand, the total blending amount of starch and copolymer latex is preferably 50 parts by mass or more and 100 parts by mass or less, more preferably 75 parts by mass or more and 100 parts by mass or less, particularly preferably 90 It is not less than mass part and not more than 100 parts by mass. Most preferably, the total binder contained in the ink receiving layer is starch and copolymer latex.

(Other ingredients)
In the present invention, the ink receptive layer may further contain, if necessary, a pigment dispersant, a thickener, a water retention agent, a lubricant, an antifoamer, a foam inhibitor, a mold release agent, a sizing agent, and a printability improver Appropriate agents) Add auxiliaries such as foaming agents, coloring dyes, coloring pigments, fluorescent dyes, preservatives, water resistance agents, surfactants, pH adjusters, antistatic agents, UV absorbers, antioxidants, etc. as appropriate. be able to.

(Base material)
As the base material, any known sheet can be used as long as it is in the form of sheet, but it is preferable to use paper mainly composed of wood pulp because the price and availability are easy. As wood pulp, chemical pulp (such as softwood bleached or unbleached kraft pulp, hardwood bleached or unbleached kraft pulp), mechanical pulp (ground pulp, thermomechanical pulp, chemical thermomechanical pulp, etc.), deinked pulp, etc. The pulp can be used alone or mixed in any proportion.
The inclusion of a filler in the substrate is preferred because the opacity and smoothness of the substrate are improved. Examples of the filler include known fillers such as hydrated silica, white carbon, talc, kaolin, clay, calcium carbonate, titanium oxide, synthetic resin filler and the like. It is also possible to use these in combination depending on the required quality.
In the present invention, it is preferable to contain calcium carbonate as a filler in the base material because an offset printing type texture and high gloss are easily obtained.

The pH at the time of making the substrate may be any of acidic, neutral and alkaline, and the basis weight of the substrate is not particularly limited. In addition, the base material may, if necessary, be a sulfate band, a sizing agent, a paper strength enhancer, a yield enhancer, a coloring agent, a dye, an antifoaming agent, a pH adjuster, etc. within the range not impairing the effects of the present invention. You may contain an auxiliary agent.
The base material may be impregnated or coated with a sizing solution containing starch, polyvinyl alcohol, a sizing agent, etc. for the purpose of enhancing paper strength, imparting of sizing properties and the like. In addition, in the size liquid, fluorescent dye, conductive agent, water retention agent, water resistant agent, pH adjuster, antifoam agent, lubricant, preservative, surfactant, as needed, as long as the effects of the present invention are not impaired. You may contain adjuvants, such as an agent. The method for impregnating or coating the size liquid is not particularly limited, but the impregnation method represented by the pound type size press or the coating method represented by the rod metering size press, the gate roll coater, and the blade coater can be exemplified. It is.

(Layer structure)
The ink receiving layer may be provided on only one side of the substrate or on both sides of the substrate. The ink receptive layer may be a single layer or two or more layers. However, in the present invention, sufficient performance can be obtained even with a single layer, so that the operability can be improved and the cost can be reduced. Therefore, the ink receiving layer is preferably one layer.
Furthermore, in order to improve the smoothness of the ink receiving layer, a precoat layer (priming layer) mainly composed of the pigment and the binder may be provided between the ink receiving layer and the substrate.

(Coating amount)
The coating amount of the ink receiving layer is appropriately selected depending on the desired quality, particularly but not a limit is 0.5 g / m ² or more 30.0 g / m ² or less in terms of solid per side content Is preferably 6.0 g / m ² or more and 25.0 g / m ² or less per side, and particularly preferably 10.0 g / m ² or more and 20.0 g / m ² or less per side.
When the coating amount of the ink receiving layer is less than 0.5 g / m < ² > in solid content per one side, it is difficult to sufficiently cover the surface of the substrate, sufficient image quality and color development, or offset printing type May not be obtained. On the other hand, when the coating amount of the ink receiving layer is large, the white paper glossiness is high, but when the coating amount of the ink receiving layer exceeds 30.0 g / m ² in solid content per one side, an offset printing type texture is obtained In addition, the surface strength of the ink receiving layer may be reduced. In addition, when the coating amount of the ink receiving layer is less than 6.0 g / m ^{2 as} solid content per one side, the image quality (line defects) in the ink jet printing with the pigment ink tends to slightly decrease, If it exceeds 0 g / m ² , the drying properties of the ink and the image quality (bleeding) tend to be slightly reduced.

(Coating method)
In the present invention, the method of coating and providing the ink receiving layer on the substrate is not particularly limited, and the coating can be performed according to a known method. Moreover, as a coating apparatus, the blade coater which is a general coating apparatus, a roll coater, an air knife coater, a bar coater, a gate roll coater, a curtain coater, a gravure coater, a flexogravure coater, a spray coater, a size press etc. Various devices can be used on-machine or off-machine as appropriate.

(White paper glossiness)
The white paper glossiness at a light incident angle of 75 degrees according to JIS Z8741 on the surface of the ink receiving layer is not particularly limited, and can be appropriately set according to the application. In particular, in order to give the texture of the gloss-like coated paper for offset printing, the white paper glossiness is preferably 50% or more and 85% or less.
When the white paper glossiness is less than 50%, the texture of the gloss coated paper can not be obtained, and the matte coated paper is obtained. In addition, it is practically difficult that the white paper glossiness exceeds 85%.
The white paper glossiness, after providing the ink receiving layer, appropriately use various calendering devices such as hard nip calender, soft nip calender, super calender, shoe calender, etc. on machine or off machine, processing temperature, processing speed, The adjustment can be made by appropriately adjusting and selecting the conditions such as the treatment linear pressure, the number of treatment steps, the diameter of the roll, the material and the like, and performing surface treatment.

  Hereinafter, the present invention will be described in more detail by way of examples, but is not limited thereto. Moreover, unless otherwise indicated, "part" and "%" described below show the "mass part" and "mass%" in an effective part, respectively. Also, the coating amount is a solid content per one side.

Example 1
The following substrates were prepared.
(Base material)
Using CSF 390 ml hardwood bleached kraft pulp (LBKP) 87 parts and CSF 480 ml softwood bleached kraft pulp (NBKP) 13 parts as pulp materials, 0.5 part paper strength agent (cationized starch) per 100 parts pulp A stock comprising 0.55 parts of aluminum sulfate and 13 parts of calcium carbonate was formed by a Fourdrinier machine to obtain a base material having a basis weight of 80 g / m ² .

A formulation having the following formulation was stirred and dispersed to obtain a coating liquid for an ink receiving layer.
<Coating fluid for ink receiving layer>
Engineered Heavy Calcium Carbonate (manufactured by Fimatech, product name: FMT-OP, D50: 0.7 μm,
X-ray transmission type D75 / D25 in the particle size distribution measurement method: 2.6) 75.0 parts Kaolin (manufactured by Thiele, product name: Kaofine, D50: 0.3 μm) 25.0 parts Organic pigment (Japan Product name: LX407 BP9, product name: LX407BP9, Tg: 60 ° C. 6.0 parts Starch (manufactured by Penford, product name: PG 295) 1.0 part copolymer latex (manufactured by JSR Co., Ltd. NSBR, product name: NP- 150) 6.0 parts Water 32.0 parts

Next, the coating liquid for the ink receiving layer is applied on one side of the substrate using a blade coater so that the coating amount is 18.0 g / m ² in solid content, and then dried and softly applied. The calendering was performed twice with a nip calender (linear pressure: 150 kN / m, roll temperature: 40 ° C.) to prepare an inkjet recording medium.

Example 2
In the inorganic pigment in the coating liquid for ink receiving layer, Example 1 and Example 1 were modified except that the blending amount of engineered heavy calcium carbonate was changed to 55.0 parts and the blending amount of kaolin was changed to 45.0 parts. An ink jet recording medium was produced in the same manner.
[Example 3]
Example 1 except that D50 of engineered heavy calcium carbonate in the coating liquid for ink receiving layer is changed to 0.2 μm, and D75 / D25 in the X-ray transmission type particle size distribution measurement method is changed to 2.8. An ink jet recording medium was produced in the same manner as in the above.
Example 4
Example 1 except that D50 of engineered heavy calcium carbonate in the coating liquid for ink receiving layer is changed to 0.3 μm, and D75 / D25 in the X-ray transmission type particle size distribution measurement method is changed to 2.7. An ink jet recording medium was produced in the same manner as in the above.
[Example 5]
Example 1 except that D50 of engineered heavy calcium carbonate in the coating liquid for ink receiving layer is changed to 1.2 μm, and D75 / D25 in the X-ray transmission sedimentation particle size distribution measuring method is changed to 2.6. An ink jet recording medium was produced in the same manner as in the above.

[Example 6]
Example 1 except that D50 of engineered heavy calcium carbonate in the coating liquid for ink receiving layer is changed to 2.0 μm, and D75 / D25 in the X-ray transmission type particle size distribution measuring method is changed to 2.6. An ink jet recording medium was produced in the same manner as in the above.
[Example 7]
An ink jet recording medium in the same manner as in Example 1 except that the kaolin in the coating liquid for the ink receiving layer was changed to 25.0 parts of kaolin (manufactured by KaMin, product name: Hydragloss, D50: 0.2 μm) Was produced.
[Example 8]
Inkjet recording was carried out in the same manner as in Example 1 except that the kaolin in the coating liquid for the ink receiving layer was changed to 25.0 parts of kaolin (made by Imerys, product name: Contour Extreme, D50: 1.5 μm). The medium was made.
[Example 9]
An ink jet recording medium was produced in the same manner as in Example 1 except that the coating amount of the ink receiving layer was changed to 5.0 g / m ² .

[Example 10]
An ink jet recording medium was produced in the same manner as in Example 1 except that the coating amount of the ink receiving layer was changed to 30.0 g / m ² .

Comparative Example 1
In the inorganic pigment in the coating liquid for ink receiving layer, Example 1 is the same as Example 1 except that the blending amount of engineered heavy calcium carbonate is changed to 40.0 parts and the blending amount of kaolin is changed to 60.0 parts. An ink jet recording medium was produced in the same manner.
Comparative Example 2
With respect to the inorganic pigment in the coating liquid for ink receiving layer, Example 1 is the same as Example 1 except that the blending amount of engineered heavy calcium carbonate is changed to 85.0 parts and the blending amount of kaolin is changed to 15.0 parts. An ink jet recording medium was produced in the same manner.
Comparative Example 3
In the inorganic pigment in the coating liquid for ink receiving layer, Example 1 is the same as Example 1 except that the blending amount of engineered heavy calcium carbonate is changed to 95.0 parts and the blending amount of kaolin is changed to 5.0 parts. An ink jet recording medium was produced in the same manner.
Comparative Example 4
An ink jet recording medium was produced in the same manner as in Example 1 except that the starch was not blended in the coating liquid for ink receiving layer.
Comparative Example 5
An ink jet recording medium was produced in the same manner as in Example 1 except that the copolymer latex was not blended in the coating liquid for ink receiving layer.

Comparative Example 6
In inorganic pigment in the coating liquid for ink receiving layer, engineered calcium carbonate is not engineered and processed with engineered calcium carbonate (Fimatech, product name: FMT-100, D50: 0.8 μm, X-ray) An inkjet recording medium was produced in the same manner as in Example 1 except that D75 / D25 in the transmission sedimentation particle size distribution measurement method was changed to 75 parts by 3.5).
Comparative Example 7
An ink jet recording medium was produced in the same manner as in Example 1 except that the organic pigment was not blended in the coating liquid for ink receiving layer.
Comparative Example 8
An ink jet recording medium was produced in the same manner as in Example 1 except that the blending amount of the organic pigment in the coating liquid for ink receiving layer was changed to 12.0 parts.
Comparative Example 9
An inkjet recording medium was produced in the same manner as in Example 1 except that the Tg of the organic pigment in the coating liquid for ink receiving layer was changed to 10 ° C.

The following evaluation was performed about the produced inkjet recording medium.
<Coloring property>
A commercially available pigment inkjet printer (product name: PX-V630, manufactured by Seiko Epson Corporation, printing conditions: (condition 1) super fine / clean mode, or (condition 2) plain paper / standard mode) Using this, solid printing (size: 2 cm long × 3 cm wide) of black, cyan, magenta and yellow was performed. One day later, the printing density of each color was measured using a Macbeth densitometer (Gretag Macbeth RD-19), and the coloring property was evaluated by the total value of four colors.
<Image quality (bars)>
A commercially available pigment inkjet printer (product name: PX-V630, manufactured by Seiko Epson Corporation, printing conditions: (condition 1) super fine / clean mode, or (condition 2) plain paper / standard mode) Using this, solid printing of magenta (size: 2 cm long × 3 cm wide) was performed, and the occurrence of streaks of non-printed portions (striations missing) was evaluated according to the following criteria.
◎: no streaks and uniform solid.
:: Some streaks are seen in part, but it is almost uniformly solid.
:: Partial bruising is observed.
X: Streaks are noticeable.

<Image quality (blur)>
With respect to the manufactured inkjet recording medium, using a commercially available pigment inkjet printer (product name: PX-V630, manufactured by Seiko Epson Corporation, printing conditions: (condition 1) super fine / clean mode), red solid (size: The printing pattern is printed with 2 cm long x 3 cm wide and green solid (size: 2 cm long x 3 cm wide) adjacent to each other in the horizontal direction, and the occurrence of bleeding at the boundary between red solid and green solid is as follows: It evaluated by the standard.
:: The boundary can be clearly identified without any mixing of the ink at the solid boundary.
Good: The ink is slightly mixed at solid boundaries, but the boundaries can be identified.
Δ: Ink is mixed at solid boundaries, but the boundaries can be generally identified.
X: Ink is mixed at solid boundaries, and it is difficult to identify the boundaries.

<Ink drying property>
With respect to the manufactured inkjet recording medium, using a commercially available pigment inkjet printer (product name: PX-V630, manufactured by Seiko Epson Corporation, printing conditions: (condition 1) super fine / clean mode), a black solid of 2 cm × 3 cm wide After printing, 5 seconds after printing, one high-quality paper with a basis weight of 80 g / m ² (npi high quality / made by Nippon Paper Industries Co., Ltd.) is stacked on the printing surface, 10 cm in diameter, 13 cm in width, and 2.7 kg in weight After pressing once, the density of the black solid transferred to wood free paper was measured using a Macbeth densitometer (Gretag Macbeth RD-19), and evaluated according to the following criteria.
◎: The density of the black solid transferred to high quality paper is less than 0.10.
Good: The density of the black solid transferred to high quality paper is 0.10 or more and less than 0.15.
B: The density of the black solid transferred to high quality paper is 0.15 or more and less than 0.20.
X: The density of the black solid transferred to high quality paper is 0.20 or more.

<White paper glossiness>
According to JIS Z8741, the white paper glossiness (light incident angle 75 degrees) of the ink receptive layer surface was measured using a glossmeter (manufactured by Murakami Color Research Laboratory, True GLOSS GM-26 PRO).
<Texture of offset printing type>
The surface feeling of the surface for the ink receiving layer of the manufactured ink jet recording medium was visually evaluated according to the following criteria.
Good: The white paper glossiness (light incident angle 75 degrees) is 60% or more, and the texture of the offset printing type is obtained.
Fair: The white paper glossiness (light incident angle 75 degrees) is 50% or more and less than 60%, and a texture similar to that of the offset printing type is obtained.
X: The white paper glossiness (light incident angle 75 degrees) is less than 50%, and the texture of the offset printing type can not be obtained.

The paper quality and the evaluation results of the ink jet recording media obtained in Examples and Comparative Examples are shown in Table 1 and Table 2.
If the evaluation of the image quality (straightness) is (, ○, there is no problem in practical use. If the other evaluations are で あ れ ば, 、, △, there is no problem in practice.

As apparent from Tables 1 and 2, in the case of each embodiment in which the ink receptive layer contains engineered calcium carbonate and kaolin and an organic pigment, and the binder comprises a starch and a copolymer latex, ink jet printing using a pigment ink is particularly effective. The ink was excellent in the drying property of the ink, had high definition image quality and high color developability, and a touch of offset printing type was obtained.
In addition, the white paper glossiness on the surface of the ink receiving layer was 50% or more, and the texture of the gloss-like coated paper for offset printing was obtained.

In Example 3, the D50 of engineered calcium carbonate was less than 0.3 μm, so the image quality (spread) and the drying property of the ink were slightly inferior to those of the other examples. In Example 6, since D50 of engineered heavy calcium carbonate exceeded 1.2 μm, coloring properties, streaking and white paper glossiness were slightly inferior to those of the other examples.
In Example 8, the D50 of kaolin exceeded 1.0 μm, so the white paper glossiness was slightly inferior to that of the other examples.
In Example 9, since the coating amount of the ink receiving layer was less than 6.0 g / m ² , the image quality (straight line) in the plain paper / standard mode was slightly inferior to the other examples.
In Example 10, since the coating amount of the ink receiving layer exceeded 25.0 g / m ² , the image quality (bleeding) and the drying property of the ink were slightly inferior to those of the other examples.
However, these examples also have no problem in practical use.

On the other hand, in the case of Comparative Example 1 in which the engineered heavy calcium carbonate is less than 50% by weight based on the total amount of the inorganic pigment, the image quality (bleeding) and the ink drying property were inferior. It is considered that this is because the blending amount of the poorly absorbable kaolin is too large.
In the case of Comparative Examples 2 and 3 in which the engineered heavy calcium carbonate exceeded 80% by weight with respect to the total amount of the inorganic pigment, the image quality (line defect) was inferior. This is considered to be due to the fact that the amount of engineered heavy calcium carbonate is too much and the ink absorbability is excessive.
Furthermore, in the case of Comparative Example 3 in which kaolin is less than 10% by mass, the white paper glossiness on the surface of the ink receiving layer is less than 50%, and the texture of the gloss-like coated paper for offset printing was not obtained.

In the case of the comparative example 4 which did not mix | blend a starch in the coating liquid for ink receptive layers, the image quality (bleeding) was inferior.
In the case of Comparative Example 5 in which the copolymer latex was not blended in the coating liquid for the ink receiving layer, the image quality was deteriorated due to the occurrence of the unprinted portion (stripe).

In the case of Comparative Example 6 in which heavy calcium carbonate not engineered was used, the image quality (bleeding) and the ink drying property were inferior. It is considered that this is because heavy calcium carbonate which is not engineered has a large amount of fine particles, and the fine particles are fitted into and filled in the voids of the ink receiving layer.
In the case of Comparative Example 7 in which the ink receiving layer did not contain an organic pigment, the blank paper glossiness was reduced to less than 50%, and a touch of offset printing type was not obtained.
In the case of Comparative Example 8 in which the compounding amount of the organic pigment in the ink receiving layer exceeded 10 parts by mass, the image quality (bleeding) was inferior.
In the case of Comparative Example 9 in which the Tg of the organic pigment in the ink receiving layer is less than 20 ° C., the drying property of the ink was inferior.

Claims (7)

An ink jet recording medium provided with an ink receiving layer containing an inorganic pigment and a starch and a copolymer latex on at least one surface of a substrate,
The coated amount of the ink receiving layer is 10.0 g / m ² or more and 20.0 g / m ² or less per one side,
The inorganic pigment contains engineered calcium carbonate and kaolin, and the engineered calcium carbonate is 50% by mass or more and less than 80% by mass, and the kaolin is 10% by mass or more and less than 50% by mass with respect to the total amount of the inorganic pigment. ,
Furthermore , 1 part by mass or more and 3 parts by mass or less of the starch, 5 parts by mass or more and 7 parts by mass or less of the copolymer latex with respect to 100 parts by mass of the inorganic pigment in the ink receiving layer An ink jet recording medium comprising 1 part by mass or more and 10 parts by mass or less of an organic pigment having a temperature of 20 ° C. or more.   The inkjet recording medium according to claim 1, wherein the engineered calcium carbonate has a 50% volume average particle diameter (D50) measured by a laser light scattering method of 0.3 μm or more and 1.2 μm or less.   The ratio of particle size (D75 (μm)) of cumulative 75% by weight and particle size (D25 (μm)) of cumulative 25% by weight of the above-mentioned engineered calcium carbonate was measured by X-ray transmission sedimentation particle size distribution measurement. The ink jet recording medium according to claim 1, wherein D75 / D25) is 3.0 or less.   The ink jet recording according to any one of claims 1 to 3, wherein the kaolin has a volume 50% average particle diameter (D50) measured by a laser light scattering method of 0.1 μm to 1.0 μm. Medium.   The ink jet recording medium according to any one of claims 1 to 4, wherein the kaolin is 20% by mass or more and 40% by mass or less based on the total amount of the inorganic pigment.   The ink jet recording medium according to any one of claims 1 to 5, wherein the copolymer latex contains an acrylonitrile styrene butadiene copolymer.   The ink jet recording medium according to any one of claims 1 to 6, wherein a white paper glossiness at a light incident angle of 75 degrees according to JIS Z8741 on the surface of the ink receiving layer is 50% to 85%.