JP2007290339A - Inkjet recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording medium excellent in glossiness and smoothness which keeps blur over time of an image improved, a coating film not cracked by folding, and paper dust not generated during cutting by a cutter. <P>SOLUTION: In the inkjet recording medium having at least two coating layers on an air-permeable base material, a first coating layer close to the base material of the coating layers contains an inorganic pigment with a pore volume of 0.5 ml/g or more according to a BET and an average particle size of 1.5 μm or less and an emulsion type adhesive as main components, a second coating layer on the first coating layer contains an inorganic fine pigment with a pore volume of 0.8 ml/g or more according to the BET and an average particle size of 0.7 μm or less and polyvinyl alcohol as main components, the first coating layer is substantially free from the polyvinyl alcohol, the first and second coating layer contains a compound crosslinkable with the polyvinyl alcohol, further the inkjet recording medium is obtained by pressing the same to a heated mirror face drum and drying the same during the second coating layer is in a wet condition. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an ink jet recording material having improved gloss and smoothness, with improved bleeding over the image of the ink jet recording material, no cracking of the coating film, little occurrence of paper dust during cutter cutting, and the like. is there.

  The ink jet recording system that ejects water-based ink from fine nozzles toward the ink jet recording body and forms an image on the recording surface has low noise during recording operation, easy formation of a full color image, high speed recording This is widely used in terminal printers, facsimiles, plotters, form printing, and the like because of the fact that it is possible and the recording cost is lower than other printing apparatuses.

  In recent years, the rapid spread of printers and higher definition and higher speed have been accompanied, and along with this, inkjet recording media have been required to improve the ink absorption speed more than before. There is a strong demand for high uniformity of images comparable to silver salt photography. Further, in order to bring the quality of a recorded image closer to that of a photographic image, further improvement in the color density and glossiness of the recorded image is desired.

In order to satisfy the improvement of ink absorbency and gloss at the same time, Japanese Patent No. 324687 (see Patent Document 1) discloses that at least one selected from silica, alumina, kaolin, titanium dioxide, etc. on the surface of non-coated paper. A coating layer containing a pigment and a binder is proposed, and the coating layer has a Cobb water absorption of 30 to 100 g / m ² and a Oken type smoothness of 30 seconds or more. Yes. However, this recording medium has a low printing density and the image quality is far from photographic. It is also difficult to achieve both cockling of the recording medium and ink absorbability.

  In recent years, in order to obtain a photographic-quality high-quality recording material, a fine pigment having a primary particle diameter of 3 to 30 nm and a secondary particle diameter of 1 μm or less has been accepted to achieve both ink absorption and printing density. Many ink jet recording materials contained in the layer have been disclosed. Although the printing density is improved by using fine pigments, the ink receiving layer is easily cracked, and how to suppress the cracking and increase the coating amount has become a development point.

Among them, the most effective method is to contain a compound that causes a cross-linking reaction with polyvinyl alcohol contained in the ink receiving layer in the ink receiving layer to suppress cracking of the ink receiving layer. The ink jet recording material obtained by this method exhibits excellent image quality and can achieve both ink absorbency and printing density.
However, since the ink receiving layer is cured by crosslinking, the coating film is easily broken due to bending stress or the like, and a large amount of paper dust is generated from the cut edge of the recording medium at the time of cutting.

In order to reduce paper dust at the time of cutter cutting, Japanese Patent Application Laid-Open No. 2004-114475 (see Patent Document 2) describes a cast coat containing an ethylene-vinyl acetate copolymer having high water resistance as a binder in a base paper undercoat. Paper has been proposed. However, in this method, since a fine pigment having a secondary particle diameter of 1 μm or less is not used, the image quality is low.
Japanese Patent Application Laid-Open No. 2004-82448 (see Patent Document 3) has an ink-receiving layer that has one layer containing an emulsion-type adhesive and inorganic fine particles on a support, and does not contain an emulsion-type adhesive thereon. By having one layer of the recording material, a recording material excellent in gloss without a crack in the coating film has been proposed. Since this recording medium contains a fine pigment having a high pore volume in both the upper and lower layers, a recording medium having high ink absorbability and excellent image quality can be obtained. However, since polyvinyl alcohol is also contained in the lower layer together with the emulsion type adhesive, the coating film is still easily broken and paper powder is often generated.

  In JP-A-2001-246832 (see Patent Document 4), only a boron compound containing no pigment or binder is applied on a support, and an ink receiving layer containing vapor-phase process silica is provided thereon. Recorders have been proposed. This recording medium has a high printing density and good ink absorbency, but the texture of the paper is conspicuous, resulting in insufficient surface smoothness and insufficient gloss.

On the other hand, in order to improve the smoothness and gloss of the recording material, Japanese Patent Application Laid-Open No. 2005-96285 (see Patent Document 5) provides a layer of a white pigment such as titanium oxide and thermoplastic resin fine particles on a support. It has been proposed that the support is heated and pressurized at a temperature equal to or higher than the glass transition temperature of the thermoplastic resin fine particles. Although this layer improves the smoothness of the recording material, the air gap of the layer is reduced due to the pressure treatment by heating, the ink absorption capacity is lowered (the air permeability is increased), and the release from the mirror drum is performed. In addition, since the undercoat layer contains a white pigment, the printing density, that is, the image quality was also lowered.
In Japanese Patent Application Laid-Open No. 2002-219854 (see Patent Document 6) and Japanese Patent Application Laid-Open No. 2002-292996 (see Patent Document 7), an undercoat layer made of an alkaline earth metal salt and an acrylic resin is formed on a support. It proposes a recording material obtained by coating an ink receiving layer containing vapor phase method silica thereon and press-contacting a heated mirror drum while the ink receiving layer is in a wet state.
The recording material thus obtained is excellent in smoothness and gloss, but since the alkaline earth metal salt has a large particle diameter, the coating strength of the undercoat layer is weak and the ink absorbency is too low, resulting in poor image quality. A decrease was seen.

Japanese Patent No. 324687 JP 2004-114475 A JP 2004-82448 A JP 2001-246832 A JP 2005-96285 A JP 2002-219854 A JP 2002-292996 A

  The present invention relates to an ink jet recording material having improved gloss and smoothness, in which bleeding of an image of the ink jet recording material is improved, coating film is not cracked, paper dust is not generated at the time of cutter cutting. .

As a result of intensive studies to solve such problems, the inventors of the present invention are ink jet recording bodies having at least two coating layers on a substrate, and the first coating layer close to the substrate is formed by BET. By containing an inorganic pigment having a pore volume of 0.5 ml / g or less and an average particle size of 1.5 μm or less and an emulsion-type adhesive as main components, ink solvent absorption and coating layer smoothness are imparted. did.
Next, the second coating layer on the first coating layer is mainly composed of an inorganic fine pigment having a BET pore volume of 0.8 ml / g or more and an average particle diameter of 0.7 μm or less and polyvinyl alcohol. A compound that imparts high image quality and gloss by containing, substantially does not contain polyvinyl alcohol in the first coating layer, and has crosslinkability with polyvinyl alcohol in the first and second coating layers. By containing, the cracking of the coating film and the generation of paper dust during cutting were improved.

  Then, while the second coating layer is in a wet state, it is found that high gloss, high smoothness and ink absorbency are simultaneously improved by pressing and drying on a heated mirror drum. 1 Invented.

  Further, a third coating layer is provided on the second coating layer, and while the third coating layer is in a wet state, it is pressed against a heated mirror drum and dried to provide high gloss and high smoothness. In addition, the present inventors have found that the ink absorption can be improved at the same time, and have reached the second invention.

The present invention includes the following embodiments.
[1] In an inkjet recording medium having at least two coating layers on a gas-permeable substrate, the first coating layer close to the substrate among the coating layers has a pore volume of 0.5 ml by BET. The main component is an inorganic pigment having an average particle size of 1.5 μm or less and an emulsion type adhesive, and the second coating layer on the first coating layer has a BET pore volume of 0.8 ml. / G or more and an inorganic fine pigment having an average particle diameter of 0.7 μm or less and polyvinyl alcohol as main components, the first coating layer substantially not containing polyvinyl alcohol, and the first and second coatings An ink jet recording material obtained by containing a compound having crosslinkability with polyvinyl alcohol in a layer, and further pressing and drying a heated mirror drum while the second coating layer is in a wet state. .
[2] In an inkjet recording medium having at least two coating layers on a gas-permeable substrate, the first coating layer close to the substrate among the coating layers has a pore volume of 0.5 ml by BET. The main component is an inorganic pigment having an average particle size of 1.5 μm or less and an emulsion type adhesive, and the second coating layer on the first coating layer has a BET pore volume of 0.8 ml. / G or more and an inorganic fine pigment having an average particle diameter of 0.7 μm or less and polyvinyl alcohol as main components, the first coating layer substantially not containing polyvinyl alcohol, and the first and second coatings The layer contains a compound having crosslinkability with polyvinyl alcohol, and further has a third coating layer on the second coating layer, and heating while the third coating layer is in a wet state. Inkjet obtained by pressure-bonding and drying on a mirror-finished drum It is a record.
[3] The third coating layer is a monodispersed colloidal pigment having an average primary particle diameter of 0.01 to 0.06 μm, alumina having an average secondary particle diameter of 1 μm or less, an alumina hydrate, an average secondary particle diameter of 0. The ink jet recording material according to [2], wherein at least one pigment selected from the group consisting of gas phase method silica of 7 μm or less and wet method gel method silica is used as a main component.

[4] The inorganic pigment having a BET pore volume of 0.5 ml / g or less contained in the first coating layer is at least one selected from monodispersed colloidal silica, wet-process silica, and calcium carbonate. It is an inkjet recording body as described in any one of [1]-[3].
[5] The emulsion-type adhesive contained in the first coating layer is at least one emulsion-type adhesive selected from acrylic, acrylic silicone, acrylic epoxy, acrylic styrene, acrylic urethane, and vinyl acetate. The inkjet recording material according to any one of [1] to [4].

[6] Average obtained by agglomerating primary particles having an average primary particle size of 0.003 to 0.04 μm in an inorganic fine pigment having a pore volume of 0.8 ml / g or more by BET contained in the second coating layer The inkjet recording material according to any one of [1] to [5], which is any one of gas phase method silica, alumina, and alumina hydrate having a secondary particle size of 0.7 μm or less.
[7] The inkjet recording material according to any one of [1] to [6], wherein the compound having crosslinkability with polyvinyl alcohol is a boron compound.

  According to the present invention, it is possible to provide an ink jet recording material which is improved in bleeding of images over time, has no cracking of the coating film, generates less paper dust during cutter cutting, and is excellent in gloss and smoothness.

  The gas-permeable substrate used in the ink jet recording material of the present invention is not particularly limited as long as it is a sheet-like material having gas permeability. For example, high-quality paper, medium-quality paper, coated paper, art paper, cast coat A paper base material such as paper, a nonwoven fabric, a gas permeable film, and the like can be used, but the use of a paper base material is preferred.

The paper base is generally composed mainly of wood pulp and a filler containing it if necessary.
As the wood pulp, various chemical pulps, mechanical pulps, regenerated pulps and the like can be used, and these pulps can be adjusted in a beating degree by a beating machine in order to adjust paper strength, papermaking suitability, and the like. The beating degree (freeness) of the pulp is not particularly limited, but is generally about 250 to 550 ml (CSF: JIS P8121). In order to improve smoothness, it is desirable to advance the beating degree. However, when recording on paper, the paper waving (cockling) caused by moisture in the ink and the blurring of the recorded image are better if the beating is not advanced. Often get. Accordingly, the freeness is preferably about 300 to 500 ml.

The filler is blended for the purpose of imparting opacity and the like, and calcium carbonate, calcined kaolin, silica, titanium oxide and the like can be used. In particular, calcium carbonate is preferable because it becomes a substrate with high whiteness and glossiness of the ink jet recording paper is enhanced. The content (ash content) of the filler in the paper substrate is preferably about 1 to 20%, and if it is too much, the paper strength may be reduced. If the amount is too small, the air permeability of the paper base material is deteriorated. Therefore, the preferable filler content is 7 to 20%. Within this range, the smoothness, air permeability, and paper strength are balanced, and as a result, it is easy to obtain an ink jet recording paper with excellent gloss.
A sizing agent, a fixing agent, a paper strength enhancer, a cationizing agent, a yield improving agent, a dye, a fluorescent brightening agent, and the like can be added to the paper base as an auxiliary agent. Furthermore, in the size press process of the paper machine, starch, polyvinyl alcohol, cationic resin, and the like can be applied and impregnated to prepare surface strength, sizing degree, and the like.

Although there is no restriction | limiting in particular about the kind of an air permeable base material, a shape, a dimension, etc., As for a steech human sizing degree (as 100 g / m < ² > paper), about 1 to 200 second is preferable. If the sizing degree is low, there may be operational problems such as wrinkling during coating, and if it is high, the dye may not be applied uniformly. A more preferred range of sizing is 4 to 120 seconds. The thickness of the substrate is preferably 150 to 280 μm in order to obtain a photographic texture. The basis weight is not particularly limited, but is about 120 to 280 g / m ² .

  In the present invention, since the second coating layer or the third coating layer is processed by the mirror drum, the air permeability (JIS P8117) of the base material is preferably 30 to 500 sec, and further 35 -300 sec is more preferable. Incidentally, by setting the air permeability to 30 sec or more, the blur of the ink jet recording material can be greatly reduced, and by setting it to 500 sec or less, the release from the mirror drum is excellent and high surface gloss is obtained.

  The smoothness of the substrate is not particularly limited, but the Beck smoothness is preferably 70 seconds (Oken type, J. TAPPI No. 5) or more in order to obtain a highly glossy and highly smooth surface. Further, the opacity of the substrate is not particularly limited, but in order to obtain a silver salt photograph-like appearance (particularly visual whiteness), the opacity (JIS P8138) is preferably 85% or more. More preferably, it is 93% or more.

  The back surface of the base material (the surface on which the first coating layer and the second coating layer are not formed) is provided with a coating layer for correcting curling to the front surface side or a laminate layer of a polyolefin resin. It is preferable to provide a layer. The back layer can be provided before or after the second coating layer or the third coating layer is processed with the mirror drum, but if the back layer has a high air permeability, the back layer is processed before the mirror drum is processed. It is possible to provide a layer. Further, the back surface of the base material may be further treated with an antistatic agent, an antiblocking agent or the like for transportability improving treatment, antistatic treatment, and antiblocking treatment.

  In addition, if the substrate is air permeable (liquid absorbing), the ink solvent when ink jet recording is performed is absorbed by the substrate from the first coating layer, and therefore the first coating layer and the second coating layer. The ink does not move again into the coating layer, and the bleeding over time is very good as compared with an ink jet recording material of a non-liquid-absorbing (non-air-permeable) substrate.

(Regarding the layer structure of the ink jet recording material)
In the present invention, using such advantages of the substrate, the first coating layer containing the specific pigment and the binder is provided on the gas-permeable substrate, and the specific pigment and the binder are provided on the first coating layer. It has a 2nd coating layer at least (1st invention). Alternatively, a third coating layer is further provided on the second coating layer (second invention).

(About the first coating layer)
The first coating layer contains, as main components, an inorganic pigment having a pore volume by BET method of 0.5 ml / g or less and an average particle diameter of 1.5 μm or less and an emulsion adhesive. The main component is sufficient if the total of the inorganic pigment and the emulsion type adhesive is larger than the other components, but it is preferably 80% by mass or more based on the total mass of the first coating layer.
When the average particle diameter of the inorganic pigment is larger than 1.5 μm, the sharpness of the recorded image is lowered. If the average particle diameter is smaller than 0.01 μm, the solvent absorbability in the ink tends to decrease, so that the average particle diameter is preferably 0.01 to 1.5 μm. In order to further improve the balance between image quality and solvent absorbability, the average particle size is preferably 1 μm or less.
Furthermore, if the pore volume by the BET method is larger than 0.5 ml / g, the stencil (cockling) of the base paper is observed after printing, and a large amount of paper dust tends to be generated during cutting. In addition, when the pore volume is smaller than 0.15 ml / g, the absorbability of the solvent is insufficient. Therefore, the pore volume is preferably 0.15 to 0.5 ml / g.

  Examples of the inorganic pigment used in the first coating layer include monodispersed colloidal silica, wet process silica, alumina, kaolin, titanium dioxide, calcium carbonate, and the like, and these inorganic pigments can be used in combination as appropriate. . In this case, a composite pigment in which the surface of the inorganic pigment is coated with another inorganic pigment is also included. Of these, monodispersed colloidal silica, wet-process silica, and calcium carbonate are particularly preferable because of their excellent solvent absorbability. The inorganic pigment is more preferably dispersed in water only as primary particles or as secondary particles in which primary particles are aggregated.

Monodispersed colloidal silica preferably has a primary particle size of 0.01 to 0.07 μm, more preferably 0.02 to 0.06 μm. Silica may be anionic or cationic, and may be alkaline or acidic.
Examples of the wet process silica include gel process silica and sedimentation process silica. Further, after adding an alkali to a colloidally dispersed silica seed solution, the wet process silica is selected from an active silicic acid aqueous solution and an alkoxysilane. A secondary silica dispersion obtained by growing silica fine particles by adding at least one kind of feed solution little by little can be obtained by a method described in JP-A-2001-354408.

The emulsion-type adhesive used for the first coating layer is used as a binder, and the first coating layer does not substantially contain polyvinyl alcohol.
Emulsion adhesives include acrylic, acrylic silicone, acrylic epoxy, acrylic styrene, acrylic urethane and vinyl acetate emulsions, butadiene latex and the like. Anionic, cationic or nonionic But it doesn't matter. Of these, acrylic resin emulsions, (poly) urethane resin emulsions, and styrene resin emulsions are particularly preferred because of the good storage stability of white paper over time.
Further, the glass transition temperature of the emulsion type adhesive is not particularly limited, but the emulsion type adhesive having a high glass transition temperature is preferable because the air permeability of the coating layer is low (ink absorption capacity is high).

  Although the blending ratio of the inorganic pigment and the binder depends on the kind thereof, it is generally adjusted in the range of 5 to 50 parts by mass, preferably 10 to 40 parts by mass with respect to 100 parts by mass of the inorganic pigment. In addition, various auxiliary agents such as dispersants, thickeners, antifoaming agents, antistatic agents, preservatives and the like used in the production of general coated paper are appropriately added. It is also possible to add a fluorescent dye, a colorant, a white pigment or the like to bring the recording body close to photographic whiteness.

  As a method for forming the first coating layer, a coating liquid containing the above components may be applied by a known coating method. For example, by various known coating devices such as blade coaters, air knife coaters, roll coaters, bar coaters, gravure coaters, rod blade coaters, lip coaters, curtain coaters, slide beads, slide hoppers, and die coaters such as slot dies. It is good to apply. In addition, you may laminate | stack several 1st coating layers, and the compounding component of both coating layers may differ in this case.

The dry solids coating weight of the first coating layer, without limitation, is preferably a generally 2~16g / ^{m 2} approximately, more preferably 4~14g / ^{m 2.} If the coating amount is too small, it may not be possible to suppress unevenness or poor texture of the base material. If the coating amount is too large, the air permeability increases, and the second coating layer or the third coating layer is When drying is performed by pressure bonding to a cast drum, drying may be insufficient, which is not preferable.

In addition, it is preferable that the water absorption (JIS P8140) of 60 seconds by the Cobb method when providing the 1st coating layer on a base material is 8-50 g / m < ² >. If the water absorption is less than 8 g / m ² , the solvent absorbability of the ink is insufficient, and if it is greater than 50 g / m ^2, it is difficult to suppress the substrate blur.

(About the second coating layer)
The second coating layer contains an inorganic pigment having a pore volume by the BET method of 0.8 ml / g or more and an average particle diameter of 0.7 μm or less and polyvinyl alcohol as main components. Here, the main component may be a total mass of the inorganic pigment and polyvinyl alcohol of 50% by mass or more based on the total mass of the second coating layer. In particular, 80 mass% or more in the total mass of the second coating layer is preferable, and more preferably 90 mass% or more.

  When an inorganic pigment having an average particle diameter of greater than 0.7 μm is used, the printing density is lowered. In order to adjust the particle diameter to 0.7 μm or less, it can be produced by, for example, a method of applying a strong force by mechanical means, that is, a so-called breaking down method (a method of subdividing a bulk material). Mechanical means include: ultrasonic homogenizer, pressure homogenizer, liquid collision homogenizer, high-speed rotary mill, roller mill, container drive medium mill, medium agitator mill, jet mill, mortar, disintegrator (covered in a bowl-shaped container) A device for grinding and kneading the pulverized product with a bowl-shaped stirring bar), a sand grinder, a nanomizer and the like. In order to reduce the particle size, classification and pulverization can be repeated. On the other hand, if the average particle size is smaller than 0.03 μm, cracks are likely to occur in the coating film, so 0.03-0.7 μm is preferable.

  Further, if the pore volume by the BET method is smaller than 0.8 ml / g, the ink absorbability is insufficient. A more preferable pore volume is 1.0 to 1.2 ml / g.

  As such an inorganic pigment, a fine pigment which is a dispersion of secondary particles formed by agglomerating primary particles having an average primary particle diameter of 0.003 to 0.04 μm is preferable. Gas phase method silica, alumina, alumina water Japanese products are listed. Of these, vapor-phase method silica is most preferably used from the viewpoint of the film formability of the coating layer and the image density after printing.

  Silica fine particles are generally roughly classified into wet process silica and dry process (vapor phase process) silica depending on the production method. In the wet method, active silica is produced by acid decomposition of silicate, and this is a method in which this is appropriately polymerized and agglomerated and precipitated to obtain hydrous silica. Gel method silica, precipitation method silica, colloidal silica, etc. Belong to these. On the other hand, the gas phase method is a method by high-temperature gas phase hydrolysis of silicon halide (flame hydrolysis method), a method in which silica sand and coke are heated and reduced by an arc in an electric furnace and oxidized with air. The method of obtaining anhydrous silica by the (arc method) is the mainstream, and the gas phase method silica means anhydrous silica fine particles obtained by the gas phase method.

Vapor phase method silica differs from wet method silica in the density of silanol groups on the surface, pore volume, and the like, and exhibits different properties. In the case of wet process silica, the density of silanol groups on the fine particle surface is high at 5 to 8 / nm ² , and the silica fine particles tend to aggregate (aggregate) easily, so the pore volume when the pore diameter is 100 nm or less is In the case of gas phase method silica, the density of silanol groups on the surface of the fine particles is as low as ² to 3 / nm ² , so that the volume of pores increases due to sparse soft aggregation (flocculate), As a result, a three-dimensional structure with a high porosity is formed.
Also in the present invention, by utilizing this difference in properties, the first coating layer contains a wet process silica to control solvent absorption and cockling of the base paper, and the second coating layer contains a vapor phase process silica. The combination of forming a three-dimensional structure with a high porosity and containing ink and controlling ink absorbency and image quality is most suitable.

Alumina is generally called aluminum oxide having crystallinity. Generally, alumina having χ, κ, γ, δ, θ, η, ρ, pseudo γ, and α crystals can be mentioned. From the viewpoint of glossiness and ink absorbability, vapor-phase method alumina and alumina having γ, δ, and θ crystals are preferably selected. Vapor phase alumina (fumed alumina) having a sharp particle size distribution and particularly excellent film formability is particularly preferred. Vapor phase alumina is formed by high temperature hydrolysis of gaseous aluminum trichloride.
The alumina hydrate is not particularly limited, but boehmite or pseudoboehmite is preferably selected from the viewpoints of ink absorbability and film formability. The production method of alumina hydrate includes, for example, a method of hydrolyzing aluminum isopropoxide with water (BE Yoldas, Amer. Ceram. Soc. Bull., 54, 289 (1975), etc.) and aluminum alkoxide. (Japanese Patent Laid-Open No. 06-064918) and the like.

The polyvinyl alcohol used as the binder in the second coating layer preferably has a degree of polymerization of 2000 or more in order to improve the balance between the film formability and the ink absorbability, and has a degree of polymerization of 3600 to 5000. Alcohol is more preferred. A water-insoluble resin latex or the like may be mixed and used as long as it is less than 10% by mass in the total mass of the second coating layer.
In this case, the dry solid content mass ratio between the pigment and the water-soluble resin in the second coating layer is preferably in the range of 5 to 30 parts by mass with respect to 100 parts by mass of the pigment. In order to further improve the balance between ink absorbency and coating strength, the content is preferably 10 to 25 parts by mass.

  In the present invention, the first and second coating layers contain a compound having crosslinkability with polyvinyl alcohol. As a method of containing, a first coating layer containing a crosslinking agent in advance is applied, a method of applying a second coating layer coating liquid after drying, and a first coating layer containing a crosslinking agent in advance. Applying and impregnating a coating solution containing a crosslinking agent after forming the first coating layer after applying the second coating layer while being wet and applying the second coating layer (that is, the wet-on-wet method) Thus, any of the methods for applying the second coating layer coating liquid is preferable because it is easy to obtain a coating layer free from cracks.

In order to form the second coating layer without cracking, the second coating layer is immediately after coating or during the drying of the coated coating solution, and the coating layer has a reduced drying rate. Before showing, it is better to thicken and crosslink the paint with a compound having crosslinkability with polyvinyl alcohol. However, if a crosslinker is included in the coating liquid for the second coating layer, the viscosity of the coating liquid increases and is uniform. The second coating layer cannot be obtained. When the first coating layer is previously incorporated with a crosslinking agent and the second coating layer is applied, a part of the crosslinking agent moves to the second coating layer, and the second coating layer is thickened and crosslinked. By making it, the 2nd coating layer without a crack can be formed.
In particular, it is preferable to add a crosslinking agent to the first coating layer coating liquid because it is not necessary to newly apply a coating liquid containing a crosslinking agent and the productivity is excellent. Since this invention does not contain polyvinyl alcohol substantially in a 1st coating layer, a crosslinking agent can be mix | blended.

Examples of the compound having crosslinkability with respect to polyvinyl alcohol include boron compounds, epoxy compounds, glycidyl compounds, zirconium compounds, aluminum compounds, chromium compounds, and the like. Among them, boron compounds cause thickening or gelation of paints quickly. Therefore, it is particularly preferable.
The boron compound is an oxygen acid having a boron atom as a central atom and a salt thereof. Examples include orthoboric acid, metaboric acid, hypoboric acid, tetraboric acid, pentaboric acid, and their sodium, potassium, and ammonium salts. Among these, orthoboric acid and disodium tetraborate are preferably used because they have an effect of moderately thickening the paint.

  Although content of a boron compound is based also on the kind of boron compound and the polymerization degree of polyvinyl alcohol, it is preferable to contain 2-10 mass% with respect to the total mass of a 2nd coating layer. When it is less than 2% by mass, the crosslinking with polyvinyl alcohol is weak, the gelation of the coating is weakened, and the coating film is easily cracked. Moreover, when it exceeds 10 mass%, a coating film becomes hard and is unpreferable.

The second coating layer preferably contains a cationic polymer in order to improve the water resistance and storage stability of the recorded image. Examples of the cationic polymer include polyalkyleneamine compounds (for example, polyethylenepolyamine, polypropylenepolyamine), acrylic resins having secondary, tertiary amino groups, or quaternary ammonium groups, polyvinylamine, polyvinylamidine, and five-membered rings. Amidine compound formed, dicyan cation resin (for example, dicyandiamide-kilmaldehyde polycondensate), epoxychlorohydrin-dimethylamine addition polymer, dimethylallyl ammonium chloride-SO ₂ copolymer, diallylamine-SO ₂ co-polymer Examples thereof include polymers, dimethyldiallylammonium chloride polymers, allylamine salt polymers, dialkylaminoethyl (meth) acrylate ammonium salt polymers, acrylamide-diallylamine salt copolymers, and the like. You can use. These cationic polymers may have a molecular weight of 5000 or more because they may inhibit ink absorbability when the molecular weight is lower than 5000.

In general, in the case of silica, since silanol groups are present on the surface, it is electrically negative and aggregates when mixed with a cationic polymer. Therefore, when silica is used in the form of composite particles treated with a cationic polymer, the dispersibility is excellent, the printing density and the image water resistance are excellent, and an excellent quality comparable to a silver salt photograph can be obtained.
In order to obtain such composite particles, for example, an aggregate particle of a cationic polymer-silica obtained by mixing and aggregating vapor phase method silica and a cationic polymer in water and having an average particle diameter is obtained. It is preferable to produce the cationic polymer-silica composite particles by pulverizing and dispersing to 0.1 to 1 μm, preferably 0.1 to 0.7 μm, more preferably 0.1 to 0.5 μm.
The cationic polymer is appropriately selected from the above exemplified cationic polymers and used alone or in combination. In order to improve the fixability of the dye and pigment in the ink and the dispersibility of the silica dispersion, it is more preferable to use a polymer of 5-membered amidines, dimethyldiallylammonium chloride, and alkoxycarbonyl-modified allylamine salt. . The addition amount of the cationic compound is preferably 1 to 30 parts by mass, and more preferably 2 to 15 parts by mass with respect to 100 parts by mass of the pigment.

In order to disperse or pulverize the mixture or aggregate of the silica and the cationic polymer, a homomixer, a pressure homogenizer, an ultrasonic homogenizer, a microfluidizer, an optimizer, a nanomizer, a high-speed rotary mill, a roller mill, and a container drive A medium mill, a medium stirring mill, a jet mill, a sand grinder, a Clare mix, etc. are used.
When the average particle diameter exceeds 1 μm, it is sufficiently dispersed if treated with a weak mechanical force such as a homomixer, but it is effective to apply a stronger mechanical force to pulverize the average particle diameter to 1 μm or less, It is preferable to use a pressure type dispersion method.
Examples of the high-pressure pulverizer that is a pressure dispersion method include a pressure homogenizer, an ultrasonic homogenizer, a microfluidizer, and a nanomizer. Particularly, a microfluidizer and a nanomizer are preferable as a high-speed flow collision type homogenizer.

The dry solids coating weight of the second coating layer, without limitation, is preferably generally is 5 to 20 g / ^{m 2,} more preferably about a 7~18g / ^{m 2.} If the coating amount is too small, the high-definition and high-speed printer may have insufficient ink absorbability. If the coating amount is too large, it may be difficult to control cracks in the coating film.
Various coating apparatuses such as a blade coater, an air knife coater, a roll coater, a bar coater, a gravure coater, a rod blade coater, a lip coater, a curtain coater, and a die coater can be used for coating the second coating layer. .

  In the first invention, while the second coating layer is in a wet state, it is pressed against a heated mirror drum, dried, and the mirror surface is copied onto the coating layer by a so-called casting method. Finish. As the casting method, a wet casting method, a rewet casting method, a gelled casting method, and the like that are conventionally known in the field of coated paper for printing can be applied. In particular, the rewetting method in which the second coating layer is applied, dried or semi-dried, moistened with a wetting liquid, and then immediately pressed onto a mirror drum and dried. This is preferable because gloss and image quality comparable to those of photographs can be obtained.

  The surface temperature of the heated mirror surface is preferably controlled within the range of 80 to 120 ° C. in view of drying efficiency. In order to make it easy to peel the second coating layer from the crimped mirror surface, a release agent such as stearamide, polyethylene wax, ammonium oleate or the like may be contained in the aqueous solution, or applied to the mirror surface. May be. Among these, it is particularly preferable to use a cationic release agent, and the addition amount of the release agent is not particularly limited, but is generally 0.1 to 5 parts by mass with respect to 100 parts by mass of the aqueous solution. .

(About the third coating layer)
In the second invention, an ink jet recording having a glossiness different from that of the first invention is formed on the second coating layer by further forming a third coating layer (outermost layer) that is pressed against a mirror drum and dried. The body can be formed.

  Examples of the pigment contained in the third coating layer include monodispersed colloidal pigments having an average primary particle diameter of 0.01 to 0.06 μm, alumina and alumina hydrate having an average secondary particle diameter of 1 μm or less, and average secondary particles. Vapor phase silica or gel silica having a diameter of 0.7 μm or less is preferably used.

  The third coating layer may contain a binder in addition to the fine pigment. The binder may be a water-soluble resin such as polyvinyl alcohol or a water-insoluble emulsion resin. In the case of water-soluble resin, there is no restriction | limiting in molecular weight etc., The dry solid content mass ratio of a pigment and a binder has preferable 100 / 10-100 / 0. When the addition rate is more than 10%, the ink absorption rate is slow. In the case of an emulsion resin, in order to increase the color density of the recorded image, the average particle size of the resin-containing particles is preferably 100 nm or less, more preferably 10 to 80 nm, and the dry solid mass of the pigment and binder. The ratio is preferably 100/30 to 100/5.

The binder used for the third coating layer is not particularly limited, but a water-insoluble emulsion resin having a cationic substituent is preferable in order to improve the fixing property and water resistance of the ink.
In particular, an acrylic ester emulsion resin having a cationic substituent in the ester group, or an acrylic ester emulsion resin having at least one component of a methacrylic ester as a copolymerization component, a copolymer of an isocyanate and a polyol having a cationic substituent. A urethane emulsion resin in which polymer ionomer resin particles are dispersed is preferably used.
The glass transition temperature is not particularly limited, but the particle diameter of the emulsion resin is preferably 20 to 50 nm. If the particle diameter is smaller than 20 nm, the ink absorption rate is slow, and if it is larger than 50 nm, the image density is lowered, which is not preferable.

Dry solid coating amount of the third coating layer is preferably in the range of ^{0.3~5g / m 2, 0.5~3g / m} 2 is more preferable. If the coating amount is too small, the coating film becomes excessively thin and an interference color due to light tends to be generated. On the other hand, if the coating amount is excessive, the ink absorption rate may be remarkably reduced. In order to improve the balance between the ink absorption speed and the ink absorption capacity, the coating amount of the second coating layer is preferably 3 to 20 times the coating amount of the third coating layer, preferably 5 to 15 times. More preferably it is.

While the third coating layer is in a wet state, it is applied by a casting method in which the third coating layer is pressed against a heated mirror drum and dried, and the mirror surface is copied onto the coating layer. As the casting method, a wet casting method, a rewet casting method, a gelled casting method, and the like that are conventionally known in the field of coated paper for printing can be applied.
Further, immediately before the second coating layer is pressed against the mirror drum, a third coating layer coating solution is applied between the second coating layer surface on the press roll and the mirror drum, and immediately pressed and dried. Mirror finish (hereinafter also referred to as nip cast finishing) can be applied, and a recording material obtained by this method is preferable because gloss and image quality comparable to a silver salt photograph can be obtained.

  At this time, in order to prevent cracking and increase the drying efficiency, the surface temperature of the heated mirror surface is preferably controlled within the range of 80 to 120 ° C. A release agent such as stearamide, polyethylene wax, ammonium oleate or the like may be included in the third coating layer in order to facilitate peeling of the third coating layer from the pressure-bonded mirror surface, or May be applied to the mirror surface. Among these, it is particularly preferable to use a cationic release agent. Although the addition amount of a mold release agent does not have limitation in particular, Generally it is preferable that it is 0.5-10 mass parts with respect to 100 mass parts of pigments contained in a 3rd coating layer.

(Measurement method of average particle size)
The average particle diameter of the pigment referred to in the present invention is the secondary particle diameter when primary particles are aggregated to form secondary particles, and the primary particle diameter when monodispersed with only primary particles. Regardless of whether the pigment is in the form of a powder or a slurry.
The measurement method was to prepare 200 g of an aqueous dispersion having a pigment concentration of 3% by mass, apply this to a homomixer, stir and disperse at 1000 rpm for 30 minutes, and then immediately remove this dispersion with an electron microscope (SEM and TEM). ) For observation, take an electron microscope photograph of 10,000 to 400,000 times, and measure and average the martin diameter of particles present in an area of 5 cm × 5 cm square in the photograph. (See "Particle Handbook", Asakura Shoten, p52, 1991).

(Method of measuring pore volume by BET)
The inorganic pigment or the dispersion of the inorganic pigment was dried at 105 ° C. to obtain a powder sample for measurement. The pore volume of this powder sample was measured after vacuum degassing at 200 ° C. for 2 hours as a pretreatment using a nitrogen gas adsorption specific surface area / pore distribution measuring apparatus (SA3100 plus type manufactured by Coulter). As the pore volume, the value of the total pore volume (nitrogen relative pressure 0.991) having a pore diameter of 3 to 200 nm was used.

  The present invention will be described more specifically with reference to the following examples, but the technical scope of the present invention is not limited thereto. First, materials used in Examples and Comparative Examples will be described.

(1) Preparation of paper base In pulp slurry (NBKP; freeness 250 mlCSF and LBKP; freeness 280 mlCSF mixed at a mass ratio of 2: 8) with a concentration of 0.5% by weight Add 2.0% by weight of cationized starch, 0.4% by weight of alkyl ketene dimer, 0.1% by weight of anionized polyacrylamide resin, 0.7% by weight of polyamide polyamine epichlorohydrin resin, and stir well. And dispersed. The pulp slurry having the above composition was made with a long net machine and passed through a drier, a size press, and a machine calendar to produce a paper substrate having a basis weight of 101 g / m ² and a tenacity of 1.0 g / cm ³ .
The size press solution used in the size press step was prepared by mixing carboxyl-modified polyvinyl alcohol and sodium chloride at a mass ratio of 2: 1, adding this to water and dissolving it by heating to a concentration of 5% by mass. A total of 25 ml / m ² of this size press solution was applied to both sides of the paper to produce a paper base with a smoothness (J.TAPPI No. 5-2) of 380 seconds.

(2) Preparation of cationic polymer-silica composite particle dispersion A (use of gas phase method silica: for second coating layer)
Gas phase method silica having an average particle diameter of 1.0 μm (manufactured by Nippon Aerosil Co., Ltd., trade name: Aerosil A300, average primary particle diameter: about 8 nm) was dispersed by a homomixer, and then the average secondary particle diameter was 800 nm. A 10% by mass silica fine particle dispersion was prepared by pulverizing and dispersing with a high-speed collision type homogenizer.
10 parts by mass of a cationic compound having a 5-membered ring amidine structure (product name: SC-700M, molecular weight: 30,000) having a 5-membered ring amidine structure is added to 100 parts by mass of this silica fine particle dispersion, and a high-speed flow collision type homogenizer is added. And 10% by weight of a cationic polymer-silica composite particle dispersion A having an average secondary particle diameter of 0.15 μm was prepared. The pore volume of this composite particle by BET was 1.1 ml / g.

(3) Preparation of silica particle dispersion B (use of wet method silica obtained by condensing activated silicic acid: for the first coating layer)
(A) Preparation of Active Silicic Acid Aqueous Solution Distilled water was added to a sodium silicate solution (trade name: No. 3 sodium silicate manufactured by Tokuyama Co., Ltd.) having a SiO ₂ concentration of 30% by mass and a SiO ₂ / Na ₂ O molar ratio of 3.1. By mixing, a dilute sodium silicate aqueous solution having a SiO ₂ concentration of 4.0% by mass was prepared. This aqueous solution was passed through a column packed with a hydrogen-type cation exchange resin (manufactured by Mitsubishi Chemical Corporation, trade name: Diaion SK-1BH) to prepare an active silicic acid aqueous solution. The SiO ₂ concentration in the obtained active silicic acid aqueous solution was 4.0% by mass, and the pH was 2.9. Further, Na ₂ O in terms of concentration was 0.1% by mass or less.
(B) Preparation of seed solution 500 g of distilled water was heated to 100 ° C. in a 5 liter glass reaction vessel equipped with a refluxer, a stirrer, and a thermometer. While maintaining this hot water at 100 ° C., a total of 450 g of the above active silicic acid aqueous solution was added at a rate of 1.5 g / min to prepare a seed solution.
(C) Preparation of Silica Fine Particle Dispersion In the glass reaction vessel, 0.015 mol of ammonia was added to 950 g of the seed solution, stabilized, and heated to 100 ° C. A total of 550 g of the above active silicic acid aqueous solution was added to the seed solution at a rate of 1.5 g / min. After completion of the addition of activated silicic acid, the solution was kept at 100 ° C. and heated to reflux for 9 hours to obtain a silica fine particle dispersion. This dispersion was concentrated with an evaporator to prepare a 10% by mass silica fine particle dispersion B.
The silica particle diameter was 0.1 μm, and the pore volume by BET was 0.4 ml / g.

[Example 1]
"Formation of the first coating layer"
On one surface of the paper substrate, the coating liquid A having the following composition was coated with a bar so that the dry coating amount was 7 g / m ² and dried to obtain a first coating layer.
<Coating fluid A>
Acrylic polymer as a binder in 100 parts by mass (solid content) of acidic colloidal silica (manufactured by Nissan Chemical Co., Ltd., trade name: ST-OL, average particle size 0.045 μm, pore volume 0.3 ml / g, anionic) (Rohm and Haas Co., Ltd., trade name: Primal P-376, emulsion type adhesive) 20 parts by mass was mixed in water to prepare an aqueous dispersion (concentration: 20% by mass).

"Formation of second coating layer"
Next, an 8% aqueous borax solution was applied onto the first coating layer, and then a coating solution B having the following composition was applied to hydrogel the second coating layer. Subsequently, the hydrogelled coating liquid layer was pressure-bonded to a mirror drum (surface temperature 95 ° C.) and dried to prepare an ink jet recording material. The dry coating amount of the second coating layer was 18 g / m ² .
<Coating fluid B>
As an inorganic pigment, 100 parts by weight (solid content) of the above cationic polymer-silica composite particle dispersion A, 18 parts by weight of polyvinyl alcohol having a polymerization degree of 3500 and a saponification degree of 88.5% as a binder, and a dispersant (Toa Gosei) An aqueous dispersion (concentration: 15% by mass) was prepared by mixing 0.05 part by mass, trade name: Aron SD-10) manufactured by the company.

[Example 2]
"Formation of the first coating layer"
In Example 1, the acidic colloidal silica contained in the first coating layer was changed to cationic colloidal silica (manufactured by Nissan Chemical Co., Ltd., trade name: ST-AKL, average particle size 0.045 μm, pore volume 0.2 ml / g). The first coating layer was formed in the same manner as in Example 1 except that the first coating layer was changed.

"Formation of second coating layer"
Next, an 8% borax aqueous solution was applied onto the first coating layer, and then the same coating liquid B as in Example 1 was applied to hydrogel the second coating layer, followed by hot air drying at 90 ° C. It was dried with a machine. The dry coating amount of the second coating layer was 18 g / m ² .
Next, the second coating layer is placed on the mirror drum side at the nip portion between the mirror drum and the press roll, and a release agent (ammonium oleate) is added in 100 masses of water between the second coating layer surface and the mirror drum. 1 wt% added aqueous solution was supplied to the part to wet the second coating layer, and then immediately dried with a mirror drum (surface temperature of 95 ° C.) while pressing with a press roll to produce an ink jet recording material did.

Example 3
"Formation of the first coating layer"
On one surface of the paper substrate, the coating liquid C having the following composition was coated with a bar so that the dry coating amount was 7 g / m ² and dried to obtain a first coating layer.
<Coating fluid C>
Alkaline colloidal silica (manufactured by Nissan Chemical Co., Ltd., trade name: ST-20L, average particle size 0.045 μm, pore volume 0.2 ml / g, anionic) 100 parts by mass (solid content), acrylic emulsion type as binder An aqueous dispersion (concentration: 20% by mass) was prepared by mixing 20 parts by mass of an adhesive (manufactured by Meisei Chemical Co., Ltd., trade name: JK7000) and 13 parts by mass of borax in water.

"Formation of second coating layer"
Next, the same coating liquid B as in Example 1 was applied onto the first coating layer, the second coating layer was hydrogelated, and dried with a 90 ° C. hot air dryer. The dry coating amount of the second coating layer was 18 g / m ² .
Next, the second coating layer is placed on the mirror drum side at the nip portion between the mirror drum and the press roll, and a release agent (ammonium oleate) is added in 100 masses of water between the second coating layer surface and the mirror drum. 1 wt% added aqueous solution was supplied to the part to wet the second coating layer, and then immediately dried with a mirror drum (surface temperature of 95 ° C.) while pressing with a press roll to produce an ink jet recording material did.

Example 4
In Example 3, the alkaline colloidal silica of the coating liquid C for forming the first coating layer was changed to the wet process silica of the dispersion B (average particle diameter 0.1 μm, pore volume 0.4 ml / g). An ink jet recording material was prepared in the same manner as Example 3 except for the above.

Example 5
In Example 3, 10 parts by mass of the alkaline colloidal silica of the coating liquid C for forming the first coating layer was treated with kaolin (manufactured by Engelhard, trade name: ULTLA WHITE 90, average particle size 0.7 μm, pores). An ink jet recording material was produced in the same manner as in Example 3 except that the mixed pigment of colloidal silica and kaolin was used instead of the volume 0.2 ml / g).

Example 6
In Example 3, 20 parts by mass of the colloidal silica of the coating liquid C forming the first coating layer was replaced with titanium dioxide (manufactured by Sakai Chemical Co., Ltd., trade name: R-21, average particle size 0.5 μm, fine). An ink jet recording material was produced in the same manner as in Example 3 except that the mixed pigment of colloidal silica and titanium dioxide was used instead of the pore volume of 0.5 ml / g).

Example 7
In Example 3, the inorganic pigment (cationic polymer-silica composite particles) of the coating liquid for forming the second coating layer was vapor-phase-processed alumina (trade name: PG003, manufactured by CABOT Co., Ltd.) with an average particle size of 0.8. An ink jet recording material was produced in the same manner as in Example 3 except that the pore volume was changed to 25 μm and the pore volume was 0.9 ml / g.

Example 8
"Formation of the first coating layer"
In the same manner as in Example 3, a first coating layer was formed.

"Formation of second coating layer"
Next, the same coating liquid B as in Example 1 was applied onto the first coating layer, the second coating layer was hydrogelated, and dried with a 90 ° C. hot air dryer. The dry coating amount of the second coating layer was 18 g / m ² .

"3rd coating layer"
Next, the second coating layer is placed on the mirror drum side at the nip between the mirror drum and the press roll, and the following coating liquid D is supplied between the second coating layer surface and the mirror drum, and is crimped by the press roll. Then, after coating, it was dried as it was with a mirror drum (surface temperature was 95 ° C.) to form a third coating layer to obtain an ink jet recording material. The dry coating amount was 1.5 g / m ² .
<Coating fluid D>
An acrylic emulsion-type adhesive (average particle size: 0.06 μm, Tg = 100 ° C.) as a binder to 100 parts by mass (solid content) of the cationic polymer-silica composite particle dispersion A (average particle size 0.1 μm) 10 parts by mass and 5 parts by mass of a release agent (ammonium oleate) were mixed in water to prepare an aqueous dispersion (concentration: 10% by mass).

Example 9
In Example 8, the inorganic pigment (cationic polymer-silica composite particles) of the coating liquid D forming the third coating layer was converted to cationic colloidal silica (produced by Grace, trade name: SJ4001, average particle size 0. 0). An ink jet recording material was produced in the same manner as in Example 8 except that the thickness was changed to 04 μm).

Example 10
In Example 3, the alkaline colloidal silica of the coating liquid C for forming the first coating layer was changed to heavy calcium carbonate (manufactured by PMMA Tech, average particle size 0.8 μm, pore volume 0.2 ml / g). An ink jet recording material was produced in the same manner as in Example 3 except for the change.

Example 11
In Example 3, 100 parts by mass of the alkaline colloidal silica of the coating liquid C for forming the first coating layer was mixed with 80 parts by mass of heavy calcium carbonate (average particle size 0.5 μm, pore volume 0.15 ml / g). And gel method silica (average particle diameter 6 μm, pore volume 2.0 ml / g) was changed to 20 parts by mass, and an ink jet recording material was produced in the same manner as in Example 3.

[Comparative Example 1]
In Example 2, after changing the base material to a gas-permeable paper base material and using a resin-coated paper in which both sides of the paper base material A are coated with a polyolefin resin, the second coating layer is hydrogelated, Implemented with the exception of drying with a hot air dryer at ℃, immediately pressing onto a mirror drum (surface temperature of 95 ℃), and then peeling (substrate is non-permeable and does not dry substantially on the mirror drum) In the same manner as in Example 2, an ink jet recording material was produced.

[Comparative Example 2]
An ink jet recording material was produced in the same manner as in Example 1. However, in the production of the first coating layer, in place of the colloidal silica of the coating liquid A, wet method silica (manufactured by Tokuyama Corporation, trade name: Fine Seal X-30, average particle size: 3 μm, pore volume 2. 0 ml / g) was used.

[Comparative Example 3]
An ink jet recording material was produced in the same manner as in Example 1. However, in the production of the first coating layer, in place of the colloidal silica of the coating liquid A, the vapor phase silica of the dispersion liquid A (average particle diameter 0.15 μm, pore volume 1.1 ml / g) was used. .

[Comparative Example 4]
An ink jet recording material was produced in the same manner as in Example 1. However, in the production of the second coating layer, in place of the gas phase method silica of the coating solution B, the wet method silica of the dispersion B (average particle size 0.1 μm, pore volume 0.4 ml / g) is used. did.

[Comparative Example 5]
An ink jet recording material was produced in the same manner as in Example 1. However, in the production of the first coating layer, the colloidal silica of coating solution A was changed to gas phase method silica of dispersion A (average particle size 0.15 μm, pore volume 1.1 ml / g), and emulsion The mold adhesive was changed to polyvinyl alcohol (saponification degree 88%, polymerization degree 3500).

[Comparative Example 6]
An ink jet recording material was produced in the same manner as in Example 1. However, in producing the second coating layer, an acrylic resin emulsion adhesive (trade name: Primal P-376, manufactured by Rohm and Haas Co.) was used in place of the polyvinyl alcohol of the coating liquid A.

[Comparative Example 7]
An ink jet recording material was produced in the same manner as in Example 3. However, when the coating liquid C did not contain borax in the production of the first coating layer, the second coating layer was cracked and could not be applied.

[Comparative Example 8]
An ink jet recording material was produced in the same manner as in Example 2. However, the 8% borax aqueous solution was applied only on the second coating layer without applying the 8% borax aqueous solution on the first coating layer.

[Comparative Example 9]
An ink jet recording material was produced in the same manner as in Example 3. However, after the second coating layer was wetted with an aqueous solution, it was not pressed and dried on the mirror drum.

Evaluation Method The ink absorbability, gloss, image quality, coating film cracking, and amount of paper dust generated at the time of cutting were evaluated by the following methods. For the evaluation, a dye ink jet printer (manufactured by EPSON, trademark: PM-G820, printing mode: EPSON photographic paper clean mode) was used. The evaluation results are shown in Table 1.

(1) Ink absorbability (print spots)
A green recording medium was solid-printed on the recorded recording medium, and whether or not there were spots in the solid-printed image was visually observed and evaluated in the following four stages. Print spots are a phenomenon that occurs when the ink that has been struck first is not completely absorbed by the coating layer of the ink jet recording body, and the next ink comes and overlaps the surface. It becomes noticeable when it becomes late.
A: No printed spots are seen.
○: There are some printed spots, but there is no practical problem.
X: Print spots are seen and practicality is low.

(2) Color density of recorded image Each color ink and heavy color portion were solid-printed, and the color density was measured with a Macbeth reflection densitometer (model: Macbeth RD-920, manufactured by Macbeth).

(3) Glossy An ISO-400 image ("high-definition color digital standard image data ISO / JIS-SCID", p13, image name: fruit basket) is printed on the sample recording medium, and the image is recorded on the recording medium. Visual observation was performed from the angle inclined with respect to the surface, and the following four levels were evaluated.
A: There is a glossiness similar to that of a silver salt photograph.
○: Slightly inferior to silver salt photograph, but with sufficient gloss.
Δ: Glossy paper lacks glossiness.
X: There is almost no gloss and it is a level close to a mat.

(4) Cracking of coating film After the sampled recording body (A4 size) was rolled into a cylinder having a diameter of 12 cm, this was taken out and lateral cracks observed on the surface of the coating film were visually determined.
○: No cracking in the coating film.
X: A crack is seen in a coating film.

(5) Amount of paper dust generated at the time of cutting 20 sheets of the tested recording medium (A4 size) were stacked and cut with a cutter, and the amount of paper dust generated was visually judged and evaluated in the following three stages. .
A: Paper dust is hardly generated.
○: A level of paper dust is generated but does not cause a problem in use.
X: The coating film on the end face of the recording material is peeled off and a lot of paper dust is generated.

(6) Image blurring over time After printing an image on 3 sheets of the tested recording medium (L size), they are immediately stacked and placed in a plastic bag, taken out one day later, and the image blur is judged visually. The following three levels were evaluated.
○: There is almost no blur of the image. Δ: There is a little blur.
X: The blur is large and the image is blurred.

From Table 1, the first coating layer contains an inorganic pigment having a pore volume of 0.5 ml / g or less and an average particle size of 1.5 μm or less and an emulsion type adhesive as main components, and the second coating layer. Contains an inorganic fine pigment having a pore volume of 0.8 ml / g or more and an average particle size of 0.7 μm or less and polyvinyl alcohol as main components, and the first coating layer substantially contains polyvinyl alcohol. In addition, the first and second coating layers contain a compound having crosslinkability with polyvinyl alcohol, and while the second coating layer is in a wet state, it is pressed and dried on a heated mirror drum. The ink jet recording material of the obtained example can achieve both high gloss and suppression of paper dust generation at the time of cutting, and good results were obtained for any other evaluation items.
Moreover, even when the third coating layer was provided on the second coating layer by the nip cast method (method of forming the coating layer at the nip portion), all the evaluation items were good as in the above results. It was.
On the other hand, the ink jet recording material of the comparative example containing an inorganic pigment different from the average particle diameter and pore volume was inferior to any of the evaluation items. In addition, an ink jet recording material of a comparative example that is different from the binder, does not contain a crosslinkable compound in the first and second coating layers, or has not been finished by casting has good gloss and paper dust. It was impossible to achieve both suppression of occurrence.
Further, the bleeding of the image over time was also better than that of the ink-jet recording material of the non-permeable substrate.
Therefore, according to the present invention, the bleeding of the image with time is improved, the coating film is not cracked, the generation of paper dust at the time of cutting the cutter is small, and the ink jet recording material is excellent in gloss and smoothness.

Claims (6)

In the ink jet recording body having at least two coating layers on a gas-permeable substrate, the first coating layer close to the substrate among the coating layers has a pore volume by BET of 0.5 ml / g or less. The main component is an inorganic pigment having an average particle diameter of 1.5 μm or less and an emulsion adhesive, and the second coating layer on the first coating layer has a pore volume of 0.8 ml / g or more by BET And an inorganic fine pigment having an average particle diameter of 0.7 μm or less and polyvinyl alcohol as main components, the first coating layer being substantially free of polyvinyl alcohol, and in the first and second coating layers An ink jet recording material comprising a compound having a crosslinking property with polyvinyl alcohol, and further obtained by pressing and drying a heated mirror drum while the second coating layer is in a wet state. In the ink jet recording body having at least two coating layers on a gas-permeable substrate, the first coating layer close to the substrate among the coating layers has a pore volume by BET of 0.5 ml / g or less. The main component is an inorganic pigment having an average particle diameter of 1.5 μm or less and an emulsion adhesive, and the second coating layer on the first coating layer has a pore volume of 0.8 ml / g or more by BET And an inorganic fine pigment having an average particle diameter of 0.7 μm or less and polyvinyl alcohol as main components, the first coating layer being substantially free of polyvinyl alcohol, and in the first and second coating layers A mirror surface that contains a compound having crosslinkability with polyvinyl alcohol, further has a third coating layer on the second coating layer, and is heated while the third coating layer is in a wet state. Inkjet recording body obtained by pressure bonding to a drum and drying . The third coating layer is a monodispersed colloidal pigment having an average primary particle diameter of 0.01 to 0.06 μm, alumina having an average secondary particle diameter of 1 μm or less, alumina hydrate, and having an average secondary particle diameter of 0.7 μm or less. The ink jet recording material according to claim 2, comprising at least one pigment selected from the group consisting of gas phase method silica and wet method gel method silica as a main component. The inorganic pigment having a BET pore volume of 0.5 ml / g or less contained in the first coating layer is at least one selected from monodispersed colloidal silica, wet process silica, and calcium carbonate. Item 4. The inkjet recording material according to any one of Items 1 to 3. The emulsion adhesive contained in the first coating layer is at least one emulsion adhesive selected from acrylic, acrylic silicone, acrylic epoxy, acrylic styrene, acrylic urethane, and vinyl acetate. The inkjet recording body of any one of 1-4. Average secondary particles obtained by agglomerating primary particles having an average primary particle diameter of 0.003 to 0.04 μm with an inorganic fine pigment having a pore volume of 0.8 ml / g or more by BET contained in the second coating layer The ink jet recording material according to any one of claims 1 to 5, which is any one of gas phase method silica having a diameter of 0.7 µm or less, alumina, or alumina hydrate.