JP5854579B2 - Inkjet recording method - Google Patents

Description

  The present invention relates to an ink jet recording medium.

  As a technique for increasing the ink absorbability of an ink jet recording medium, conventionally, studies have been made to form a multilayer ink receiving layer using an inorganic pigment and PVA.

Japanese Patent Application Laid-Open No. 2004-228561 discloses a technique for increasing the ink receptivity by lowering the saponification degree of PVA contained in the surface layer to be lower than the saponification degree of PVA of the ink receiving layer. Also,
Patent Document 2 discloses a method of increasing ink absorbency by controlling the amount of PVA in the lower layer and the upper layer with a two-layered ink receiving layer.

  Patent Document 3 and Patent Document 4 disclose a method of increasing the ink absorbency by defining the saponification degree of PVA of each layer in a two-layer configuration, and making the saponification degree of the upper layer higher than the saponification degree of the lower layer. ing.

JP-A-8-112965 JP 2004-255594 A Japanese Patent Laid-Open No. 2004-2231992 JP 2008-246791 A

  In recent years, in ink jet recording, printing with pigment inks in a form dispersed in water as well as dye-based inks soluble in water is increasing. Furthermore, high-speed recording is being performed with pigment ink in accordance with the current trend toward higher speeds.

Therefore, the present inventor studied the methods of Patent Documents 1 to 4.
As a result, in the method of Patent Document 1, no cross-linking agent is used in both the upper layer and the lower layer, so that cracks occurred during the formation of the porous ink receiving layer. The method of Patent Document 1 is a problem in recent years. The ink absorptivity sufficient for high-speed recording with the pigment ink was not shown.

  The two-layer configuration of Patent Document 2 focuses on only the amount of PVA and does not focus on the hydrophilicity of the two layers. Further, the technique of Patent Document 2 does not exhibit ink absorbability that can sufficiently cope with high-speed recording with pigment ink, which is a recent problem.

  In both Examples of Patent Document 3 and Patent Document 4, a result of good ink absorbability is shown. However, when high-speed recording with pigment ink, which is a recent problem, is performed, the methods of Patent Document 3 and Patent Document 4 do not exhibit ink absorbability that can be sufficiently handled. Furthermore, as a result of examination of Patent Document 4, regarding the high-speed recording with the pigment ink, there was no great difference in the ink absorptivity in both the examples and the comparative examples, and the ink absorptivity sufficient for both was not shown.

  The present invention has been made in view of the above situation. An object of the present invention is to provide an ink jet recording medium having high ink absorbability capable of preventing the occurrence of cracks and supporting high speed recording with a pigment ink, which is a recent problem.

One embodiment is:
An inkjet recording method for recording an image by applying a pigment ink to an inkjet recording medium,
The inkjet recording medium has a support and at least two or more porous ink receiving layers on the support,
The porous ink receiving layer is obtained by applying a coating liquid for a porous ink receiving layer containing an inorganic pigment, polyvinyl alcohol and boric acid,
The boric acid content in each porous ink receiving layer coating solution is 0.2 equivalents or more of the polyvinyl alcohol content,
The contact angle a with respect to pure water of the porous ink receiving layer (ink receiving layer A) constituting the outermost layer and the contact with pure water of the porous ink receiving layer (ink receiving layer B) immediately below the ink receiving layer A The angle b satisfies the following relational expression (A),
The present invention relates to an ink jet recording method, wherein the saponification degree of polyvinyl alcohol contained in the ink receiving layer A is lower than the saponification degree of polyvinyl alcohol contained in the ink receiving layer B.
a> b, 30 ° <a ≦ 50 °, 30 ° ≦ b <50 ° (A).

  The contact angle to the pure water and the amount of the crosslinking agent of the outermost layer (ink receiving layer A) and the layer immediately below the outermost layer (ink receiving layer B) are controlled. Thereby, there is almost no crack generation and sufficient ink absorptivity can be exhibited even in high-speed recording with pigment ink.

Hereinafter, the ink jet recording medium will be described in detail.
The inkjet recording medium has a support and at least two or more porous ink receiving layers containing an inorganic pigment, PVA (polyvinyl alcohol), and a crosslinking agent on the support. In all the porous ink receiving layers, the content of the crosslinking agent in each porous ink receiving layer is 0.2 equivalent or more of the content of PVA. Of these two or more porous ink receiving layers, the contact angle of the porous ink receiving layer (ink receiving layer A) constituting the outermost layer with respect to pure water is a. In addition, a contact angle with respect to pure water of a porous ink receiving layer (ink receiving layer B) in contact with the ink receiving layer A immediately below the ink receiving layer A is defined as b. In this case, a and b satisfy the following relational expression (A).
a> b, 30 ° <a ≦ 50 °, 30 ° ≦ b <50 ° (A).

  In addition, about said "equivalent", the amount of crosslinking agents which react completely with the amount of hydroxyl groups which PVA has theoretically shall be 1.0 equivalent.

  The values of the contact angles a and b are measured as follows. Using a dynamic absorption tester (DAT) 1100 manufactured by Fibro, about 1.5 μl of pure water is dropped on the surfaces of the ink receiving layers A and B in an environment of 23 ° C. and 50% RH. Then, after dropping, the contact angles a and b after 0.1 seconds have been measured.

  Below, in this invention, the effect by having prescribed | regulated so that content of a crosslinking agent and contact angle a, b may satisfy | fill relational expression (A) is demonstrated in detail.

  The reason why the ink absorbability is improved in the present invention is considered as follows. The penetrability of the pigment ink into the porous ink receiving layer can be determined by the Lucas-Washburn equation expressed by the following equation (1).

(Where, l: penetration depth, R: pore radius in the porous ink receiving layer, γ: surface tension of the pigment ink, θ: contact angle of the pigment ink with respect to the porous ink receiving layer, t: penetration time, η : Viscosity of pigment ink).

  In addition, a capillary force represented by the following formula (2) works in the fine pores of the porous ink receiving layer, and the pigment ink penetrates into the pores.

(Where F: capillary force, R: pore radius in the porous ink receiving layer, γ: surface tension of the pigment ink, θ: contact angle of the pigment ink with respect to the porous ink receiving layer).

  Therefore, as can be seen from the above formulas (1) and (2), the smaller the contact angle θ, the larger the l (penetration depth) and the F (capillary force), and the amount of pigment ink applied to the porous ink receiving layer. It can be said that the permeability becomes high.

  The pigment ink contains various components, and the contact angle of the pigment ink to the porous ink receiving layer varies depending on the composition. However, since the pigment ink contains a large amount of water as a main component, the penetration of the pigment ink into the ink receiving layers A and B is substantially controlled by controlling the contact angle of pure water with the ink receiving layers A and B. Gender can be controlled.

In the present invention, the contact angles a and b of the ink receiving layers A and B with respect to pure water satisfy the following relational expression (A).
a> b, 30 ° <a ≦ 50 °, 30 ° ≦ b <50 ° (A).

  For this reason, when the pigment ink is driven onto the porous ink receiving layer at high speed, a large amount of the pigment ink exists on the outermost layer (ink receiving layer A) of the porous ink receiving layer. At this time, since the ink receiving layer A has a larger contact angle with respect to pure water than the porous ink receiving layer (ink receiving layer B) immediately below, the ink permeability of the pigment ink is relatively low. Yes. For this reason, a large amount of pigment ink that is driven into the ink receiving layer A at a high speed does not immediately penetrate into the ink receiving layer A, but gradually penetrates into the ink receiving layer A. In this way, the ink receiving layer A can retain a large amount of pigment ink on the surface of the ink receiving layer A for a certain time so as not to adversely affect the image characteristics.

  On the other hand, since the ink receiving layer B has a smaller contact angle with respect to pure water than the ink receiving layer A, the permeability of the pigment ink is relatively high. For this reason, the ink component that has permeated the ink receiving layer A quickly permeates the ink receiving layer B.

  Accordingly, a large amount of the pigment ink that has been ejected on the ink receiving layer A at a high speed can be smoothly absorbed through the ink receiving layers A and B without staying on the ink receiving layer A for a long time. Become. As a result, the ink jet recording medium can exhibit excellent pigment ink absorbability even in high-speed printing.

  As described above, the ink receiving layers A and B automatically adjust the permeability of the pigment ink printed at a high speed and in a large amount due to the difference in the permeability of the pigment ink, so that the pigment ink can be applied to a specific layer. Absorption can be effectively performed without being retained for a long time.

  Further, when the contact angle a is 30 ° or less, the absorbability of the pigment ink in the ink receiving layer A becomes too high, and the pigment particles are fixed on the surface of the ink receiving layer A to have excellent image characteristics. Can not be. If the contact angle a exceeds 50 °, the absorbability of the pigment ink into the ink receiving layer A is too low, and the pigment ink stays on the surface of the ink receiving layer A for a long time. As a result, bleeding or the like occurs and image characteristics of the ink jet recording medium are lowered. Further, the ink cannot be absorbed smoothly into the ink receiving layers A and B.

  When the contact angle b is less than 30, the absorbability of the pigment ink into the ink receiving layer B becomes too high, and the ink solvent spreads between the ink receiving layers A and B, thereby inhibiting ink absorption. If the contact angle b is 50 or more, the absorbability of the pigment ink into the ink receiving layer B becomes too low, and a large amount of pigment ink stays in the ink receiving layer A for a long time. As a result, ink bleeding or the like occurs, and the image characteristics of the ink jet recording medium deteriorate.

  The ink jet recording medium only needs to have two or more porous ink receiving layers on the support, and the number of porous ink receiving layers may be two or three or more. When the number of porous ink receiving layers is two, the surface side layer is the ink receiving layer A, and the ink receiving layer B exists between the support and the ink receiving layer A. That is, in this case, the ink jet recording medium is a layer in which layers are laminated in the order of support-ink-receiving layer B-ink-receiving layer A.

  When the number of porous ink receiving layers is three or more, the most surface layer on the opposite side of the support is the ink receiving layer A, and the layer immediately below the ink receiving layer A in contact with the ink receiving layer A is the ink receiving layer B. Become. That is, in this case, the ink jet recording medium is a layer in which the layers are laminated in the order of support- (one or more porous ink receiving layers) -ink receiving layer B-ink receiving layer A.

The coating amount after drying of the ink receiving layer A is preferably 3 g / m ² or more and 10 g / m ² or less. When the coating amount is 3 g / m ² or more, a more uniform coated surface can be obtained. Further, when the coating amount is 10 g / m ² or less, a sufficient effect due to the two-layer structure can be obtained, and the ink absorbability can be further improved.

  Moreover, it is preferable to form all the porous ink receiving layers by repeating the step of applying the coating liquid for the porous ink receiving layer twice or more.

  The saponification degree of PVA used for the ink receiving layer A is preferably lower than the saponification degree of PVA used for the ink receiving layer B. This is because it is easy to increase the contact angle by using PVA with a low saponification degree for the ink receiving layer A. The degree of saponification of PVA can be measured according to JIS K 6726.

The coating amount after drying of the ink receiving layer B is preferably 25 g / m ² or more and 45 g / m ² or less from the viewpoint of volume and cracks. When the coating amount is 25 g / m ² or more, the ink absorbability of the entire ink receiving layer is improved and sufficient ink absorbability can be obtained. Moreover, generation | occurrence | production of a crack can be suppressed more effectively as it is 45 g / m < ² > or less.
Below, the material used for an inkjet recording medium is demonstrated in detail.

(Support)
As the support, paper such as cast-coated paper, baryta paper, and resin-coated paper (resin-coated paper coated on both sides with a resin such as polyolefin) can be preferably used. In addition, transparent thermoplastic films such as polyethylene, polypropylene, polyester, polylactic acid, polystyrene, polyacetate, polyvinyl chloride, cellulose acetate, polyethylene terephthalate, polymethyl methacrylate, and polycarbonate can be preferably used.

  In addition to this, non-size paper or coated paper, which is appropriately sized paper, or a sheet-like substance (synthetic paper or the like) made of a film made opaque by filling with inorganic substances or fine foaming can be used. Further, a sheet made of glass or metal may be used. Furthermore, in order to improve the adhesive strength between the support and the porous ink receiving layer, the surface of the support can be subjected to corona discharge treatment or various undercoat treatments.

  Among the above-mentioned supports, it is preferable to use resin-coated paper from the standpoint of quality such as glossiness of the ink jet recording medium after forming the porous ink receiving layer.

(Inorganic pigment)
As the inorganic pigment used in the porous ink receiving layer, alumina hydrate and silica are preferable. As the alumina hydrate, for example, those represented by the following general formula (X) can be suitably used.
Al ₂ O _3-n (OH) _2n · mH ₂ O ... (X)
(In the above formula, n represents any of 0, 1, 2, or 3, and m represents a value in the range of 0 to 10, preferably 0 to 5. However, m and n are not 0 at the same time. MH ₂ O often represents a detachable aqueous phase that does not participate in the formation of the crystal lattice, so m can be an integer or non-integer value. When heated, m can reach a value of 0).

  As the crystal structure of the alumina hydrate, amorphous, kibsite type, and boehmite type are known according to the heat treatment temperature, and any of these crystal structures can be used.

  Among these, a preferred alumina hydrate is an alumina hydrate that exhibits a boehmite structure or an amorphous state by analysis by an X-ray diffraction method. Specific examples include alumina hydrates described in JP-A-7-232473, JP-A-8-132731, JP-A-9-66664, JP-A-9-76628, and the like.

  This alumina hydrate preferably has an average pore radius of 7.0 nm to 15.0 nm when the porous ink receiving layer is formed. When the average pore radius of the porous ink receiving layer is within these ranges, excellent ink absorbability and color developability can be exhibited. When the average pore radius of the porous ink receiving layer is larger than the above range, the haze of the porous ink receiving layer increases, and good color developability may not be obtained.

  Furthermore, it is preferable that pores having a pore radius of 25 nm or more are not substantially present as the pore radius of the porous ink receiving layer. By not having pores of 25 nm or more, the haze of the porous ink receiving layer is reduced, and good color developability can be obtained.

  The average pore radius and pore radius described above are determined by using the BJH (Barrett-Joyner-Halenda) method from the adsorption / desorption isotherm of nitrogen gas measured on the recording medium by the nitrogen adsorption / desorption method. Value. In this method, the average pore radius can be obtained by calculating from the total pore volume and specific surface area measured at the time of nitrogen gas desorption.

In order to obtain the average pore radius of the alumina hydrate when forming the porous ink receiving layer as described above, the alumina hydrate having a BET specific surface area of 100 m ² / g or more and 200 m ² / g or less. Is preferably used. Further, the BET specific surface area is more preferably 125 m ² / g or more and 175 m ² / g or less.

  The BET method is a method for measuring the surface area of a powder by a vapor phase adsorption method, and is a method for obtaining the total surface area, that is, the specific surface area of a 1 g sample from an adsorption isotherm. In this BET method, nitrogen gas is usually used as an adsorbed gas, and the most frequently used method is to measure the amount of adsorption from the change in pressure or volume of the gas to be adsorbed. At this time, the most prominent expression representing the isotherm of multimolecular adsorption is the Brunauer, Emmett, and Teller equation, which is called the BET equation and is widely used for determining the specific surface area. In the BET method, the specific surface area is obtained by calculating the amount of adsorption based on the BET formula and multiplying the area occupied by one adsorbed molecule on the surface.

  Further, the preferred shape of the alumina hydrate is preferably a flat plate having an average aspect ratio of 3.0 to 10 and an aspect ratio of the flat plate surface of 0.60 to 1.0. The aspect ratio can be determined by the method described in Japanese Patent Publication No. 5-16015. That is, the aspect ratio is expressed by the ratio of (diameter) to (thickness) of particles. Here, the “diameter” indicates a diameter (equivalent circle diameter) of a circle having an area equal to the projected area of the particles when the alumina hydrate is observed with a microscope or an electron microscope. Similarly to the aspect ratio, the aspect ratio of the flat plate surface indicates the ratio of the diameter indicating the minimum value of the flat plate surface and the diameter indicating the maximum value when the particles are observed with a microscope.

  When alumina hydrate having an aspect ratio outside the above range is used, the pore distribution range of the formed porous ink receiving layer may be narrowed. For this reason, it may be difficult to produce the alumina hydrate with the same particle size. Similarly, when a material having an aspect ratio outside the above range is used, the pore size distribution of the porous ink receiving layer may be narrowed.

(PVA)
Among the PVA (polyvinyl alcohol), PVA having a saponification degree of 70% to 100% is preferably used. The PVA content in the porous ink receiving layer is preferably 5 parts by mass or more and 13 parts by mass or less with respect to 100 parts by mass of the alumina hydrate. The PVA content is preferably 7 parts by mass or more and 12 parts by mass or less. The average degree of polymerization of PVA is preferably 1500 or more and 5000 or less.

  The PVA may be used alone or in combination of two or more. The contact angle of the porous ink receiving layer with pure water when two or more kinds of PVA are used in combination is affected by PVA having a low saponification degree, and therefore can be used in combination with PVA having a high saponification degree.

(Crosslinking agent)
As a crosslinking agent used suitably, what can raise | generate a crosslinking reaction with the said PVA and can harden | cure is preferable, and what does not impair the effect of this invention can be used. As the crosslinking agent, boric acid is particularly preferable. In this case, boric acid that can be used includes not only orthoboric acid (H ₃ BO ₃ ), but also metaboric acid and diboric acid. From the viewpoint of the stability of the coating solution over time and the effect of suppressing the generation of cracks. It is preferable to use orthoboric acid.

  The amount of boric acid used is preferably in the range of 0.2 equivalents to 1.2 equivalents with respect to PVA in the porous ink receiving layer. By setting it as the said range, the temporal stability of a coating liquid can be improved. That is, when forming the porous ink receiving layer, the coating solution is used for a long time. If the content of boric acid in the coating solution is large, the viscosity of the coating solution increases during that time. In addition, gelation may occur. For this reason, it is necessary to frequently change the coating liquid, clean the coater head, and the like, and the productivity of the ink jet recording medium is significantly reduced. Further, when the above range is exceeded, dot-like surface defects are likely to occur in the porous ink receiving layer, and a uniform and good glossy surface may not be obtained.

(PH adjuster)
In the coating liquid for forming the ink receiving layers A and B, for example, the following acids can be appropriately added as pH adjusters.
Formic acid, acetic acid, glycolic acid, oxalic acid, propionic acid, malonic acid, succinic acid, adipic acid, maleic acid, malic acid, tartaric acid, citric acid, benzoic acid, phthalic acid.
Isophthalic acid, terephthalic acid, glutaric acid, gluconic acid, lactic acid, aspartic acid, glutamic acid, pimelic acid, suberic acid, methanesulfonic acid.
Inorganic acids such as hydrochloric acid, nitric acid, phosphoric acid.

  It is preferable to use a monobasic acid to disperse the alumina hydrate in water. For this reason, it is preferable to use organic acids, such as formic acid, acetic acid, glycolic acid, and methanesulfonic acid, hydrochloric acid, nitric acid, etc. among the said pH adjusters.

(Additive)
As a coating liquid additive for a porous ink receiving layer, a pigment dispersant, a fastness improving agent, etc., should be used as long as the contact angle with pure water after the porous ink receiving layer is formed does not change significantly. Can do.

Next, a coating method of the coating liquid for the ink receiving layers A and B will be described.
In order to obtain an appropriate coating amount, for example, the following coating method can be used for coating the coating liquid for the ink receiving layers A and B, and coating is performed on-machine and off-machine.
・ Various curtain coaters and coaters using the extrusion method.
・ Coater using slide hopper method.
Incidentally, at the time of coating, for the purpose of adjusting the viscosity of the coating solution, the coating solution may be heated, or the coater head can be heated.

  For drying the coating liquid after coating, for example, a hot air dryer such as a straight tunnel dryer, an arch dryer, an air loop dryer, a sine curve air float dryer, or the like can be used. In addition, a dryer using infrared rays, a heated dryer, a microwave, or the like can be appropriately selected and used.

  When three or more porous ink receiving layers are provided, the coating liquid can be applied to the porous ink receiving layers other than the ink receiving layers A and B by the above coating method.

  Hereinafter, the present invention will be described more specifically with reference to examples. The following examples are specific examples shown for a deeper understanding of the present invention, and the present invention is not limited to these specific examples.

[Example 1]
<Production of support>
A support was prepared as follows.
First, a paper stock having the following composition was prepared.
-Pulp slurry 100 parts by weight Freeness 450 ml CSF (Canadian Standard Freeness), hardwood bleached kraft pulp (LBKP) 80 parts by weight Condensation degree 480 ml CSF, softwood bleached kraft pulp (NBKP)
20 parts by mass-cationized starch 0.60 parts by mass-heavy calcium carbonate 10 parts by mass-light calcium carbonate 15 parts by mass-alkyl ketene dimer 0.10 parts by mass-cationic polyacrylamide 0.030 parts by mass.

Next, this stock was made with a long paper machine, subjected to a three-stage wet press, and then dried with a multi-cylinder dryer. Thereafter, the starch starch aqueous solution was impregnated with a size press device so that the solid content was 1.0 g / m ² and dried. Thereafter, machine calendar finishing was performed to obtain a base paper A having a basis weight of 170 g / m ² , a Steecht size of 100 seconds, an air permeability of 50 seconds, a Beck smoothness of 30 seconds, and a Gurley stiffness of 11.0 mN.

On the base paper A, 25 g / m ^{2 of a} resin composition comprising low density polyethylene (70 parts by mass), high density polyethylene (20 parts by mass), and titanium oxide (10 parts by mass) was applied. Furthermore, a resin-coated support was obtained by applying 25 g / m ² of a resin composition consisting of high-density polyethylene (50 parts by mass) and low-density polyethylene (50 parts by mass) on the back surface.

<Manufacture of ink jet recording medium>
On the support, a coating liquid for ink receiving layers A and B was applied and dried to form a porous ink receiving layer. The composition of each coating liquid, the coating method, etc. at this time are as follows.

(Adjustment of coating liquid for ink receiving layer A)
First, alumina hydrate Dispersal HP14 (manufactured by Sasol Corporation) (inorganic pigment) was added to pure water as an inorganic alumina hydrate so as to be 30% by mass. Next, methanesulfonic acid was added to 100 parts by mass of this alumina hydrate so as to be 1.5 parts by mass and stirred to obtain a colloidal sol. The obtained colloidal sol was appropriately diluted so that the alumina hydrate was 27% by mass to obtain colloidal sol A.

  On the other hand, polyvinyl alcohol PVA420 (manufactured by Kuraray Co., Ltd., polymerization degree: 2000, saponification degree: 78%) was dissolved in ion-exchanged water to obtain a PVA aqueous solution having a solid content of 8.0% by mass. And the produced PVA solution was mixed with colloidal sol A prepared above so that the PVA solid content conversion was 9 parts by mass with respect to 100 parts by mass of the solid content of alumina hydrate.

  Next, the 3.0 mass% boric acid aqueous solution is 1.4 mass parts (0.7 equivalents relative to PVA420) in terms of boric acid solid content with respect to 100 mass parts of the solid content of alumina hydrate. To obtain a coating liquid A for the ink receiving layer A.

(Adjustment of coating liquid for ink receiving layer B)
First, alumina hydrate Dispersal HP14 (manufactured by Sasol Corporation) (inorganic pigment) was added to pure water as an inorganic alumina hydrate so as to be 30% by mass. Next, methanesulfonic acid was added to 100 parts by mass of this alumina hydrate so as to be 1.5 parts by mass and stirred to obtain a colloidal sol. The obtained colloidal sol was appropriately diluted so that the alumina hydrate was 27% by mass to obtain colloidal sol B.

  On the other hand, polyvinyl alcohol PVA235 (manufactured by Kuraray Co., Ltd., polymerization degree: 3500, saponification degree: 88%) was dissolved in ion-exchanged water to obtain a PVA aqueous solution having a solid content of 8.0% by mass. And the produced PVA solution was mixed with colloidal sol B prepared above so that PVA solid content conversion might be 9 mass parts with respect to 100 mass parts of solid content of an alumina hydrate.

  Next, the 3.0 mass% boric acid aqueous solution becomes 1.8 mass parts (0.7 equivalent with respect to PVA235) in terms of boric acid solid content with respect to 100 mass parts of the solid content of alumina hydrate. To obtain a coating liquid B for the ink receiving layer B.

(Coating method of porous ink receiving layer)
On the support, the coating liquid B for the ink receiving layer B was coated so that the coating amount after drying was 35 g / m ^2, and then dried at 50 ° C. Next, the coating liquid A for the ink-receiving layer A was applied so that the coating amount after drying was 8 g / m ^2, and then dried at 50 ° C. to produce the inkjet recording medium 1.
[Example 2]
In Example 1, with respect to the coating liquid A for the ink receiving layer A, 2.5 parts by mass in terms of boric acid solid content (1.2 equivalents with respect to PVA420) with respect to 100 parts by mass of the solid content of alumina hydrate. ). Except for this, an inkjet recording medium 2 was produced in the same manner as in Example 1.

Example 3
In Example 1, with respect to the coating liquid A for the ink receiving layer A, 0.4 parts by mass (0.2 equivalents with respect to PVA420) in terms of solid content of boric acid with respect to 100 parts by mass of solid content of alumina hydrate. ). Except for this, an inkjet recording medium 3 was produced in the same manner as in Example 1.

Example 4
In Example 1, with respect to the coating liquid B for the ink receiving layer B, 0.5 parts by mass in terms of boric acid solid content (0.2 equivalent to PVA235) with respect to 100 parts by mass of the solid content of alumina hydrate. ). Other than this, an inkjet recording medium 4 was produced in the same manner as in Example 1.

Example 5
In Example 1, with respect to the coating liquid B for the ink-receiving layer B, 2.8 parts by mass in terms of boric acid solid content with respect to 100 parts by mass of the solid content of alumina hydrate (1.1 equivalents with respect to PVA235) ). Except for this, an inkjet recording medium 5 was produced in the same manner as in Example 1.

Example 6
In Example 2, with respect to the coating liquid B for the ink receiving layer B, 0.5 parts by mass (0.2 equivalents with respect to PVA235) in terms of solid content of boric acid with respect to 100 parts by mass of the solid content of alumina hydrate. ). Other than this, an inkjet recording medium 6 was produced in the same manner as in Example 2.

Example 7
In Example 2, with respect to the coating liquid B for the ink receiving layer B, 3.0 parts by mass in terms of boric acid solid content (1.2 equivalents relative to PVA235) with respect to 100 parts by mass of the solid content of alumina hydrate. ). Except for this, an inkjet recording medium 7 was produced in the same manner as in Example 2.

[ Reference Example 8]
In Example 1, with respect to the coating liquid A for the ink receiving layer A, the PVA type was changed from PVA420 to PVA235. Moreover, it changed so that it might become 3.0 mass parts (1.2 equivalent with respect to PVA235) in conversion of a boric acid solid content with respect to 100 mass parts of solid content of an alumina hydrate. Other than this, an inkjet recording medium 8 was produced in the same manner as in Example 1.

[ Reference Example 9]
In Reference Example 8, with respect to the coating liquid B for the ink receiving layer B, 0.5 parts by mass in terms of boric acid solid content (0.2 equivalent to PVA235) with respect to 100 parts by mass of the solid content of alumina hydrate. ). Except for this, an inkjet recording medium 9 was produced in the same manner as in Reference Example 8.

[ Reference Example 10]
In Example 1, with respect to the coating liquid A for the ink receiving layer A, the PVA type was changed from PVA420 to PVA235. Moreover, it changed so that it might become 2.3 mass parts (0.9 equivalent with respect to PVA235) in conversion of boric acid solid content with respect to 100 mass parts of solid content of an alumina hydrate. Except for this, an inkjet recording medium 10 was produced in the same manner as in Example 1.

[ Reference Example 11]
In Example 1, with respect to the coating liquid A for the ink receiving layer A, the PVA type was changed from PVA420 to PVA235. Moreover, it was made to become 2.8 mass parts (1.1 equivalent with respect to PVA235) in conversion of boric acid solid content with respect to 100 mass parts of solid content of an alumina hydrate.

In Example 1, with respect to the coating liquid B for the ink receiving layer B, 2.3 parts by mass in terms of boric acid solid content with respect to 100 parts by mass of the solid content of alumina hydrate (0.9 equivalent to PVA235) ).
Other than this, an inkjet recording medium 11 was produced in the same manner as in Example 1.

[ Reference Example 12]
In Example 2, regarding the coating liquid B for the ink receiving layer B, the PVA type was changed from PVA235 to PVA420. Moreover, it changed so that it might become 1.4 mass parts (0.7 equivalent with respect to PVA420) in conversion of boric acid solid content with respect to 100 mass parts of solid content of an alumina hydrate. Except for this, an inkjet recording medium 12 was produced in the same manner as in Example 2.

[ Reference Example 13]
In Reference Example 12, with respect to the coating liquid B for the ink-receiving layer B, 0.4 parts by mass (0.2 equivalent to PVA420) in terms of boric acid solid content with respect to 100 parts by mass of the solid content of alumina hydrate. ). Except for this, an inkjet recording medium 13 was produced in the same manner as in Reference Example 12.

[ Reference Example 14]
In Reference Example 12, with respect to the coating liquid B for the ink receiving layer B, 2.2 parts by mass in terms of boric acid solid content (1.1 equivalents with respect to PVA420) with respect to 100 parts by mass of the solid content of alumina hydrate. ). Except for this, an inkjet recording medium 14 was produced in the same manner as in Reference Example 12.

[ Reference Example 15]
In Example 1, with respect to the coating liquid A for the ink receiving layer A, 2.2 parts by mass in terms of boric acid solid content with respect to 100 parts by mass of the solid content of alumina hydrate (1.1 equivalents with respect to PVA420) ).

In Example 1, with respect to the coating liquid B for the ink receiving layer B, the PVA type was changed from PVA235 to PVA420. Moreover, it changed so that it might become 2.0 mass parts (1.0 equivalent with respect to PVA420) in conversion of boric acid solid content with respect to 100 mass parts of solid content of an alumina hydrate.
Other than this, an inkjet recording medium 15 was produced in the same manner as in Example 1.

Example 16
Polyvinyl alcohol PVA117 (manufactured by Kuraray Co., Ltd., polymerization degree: 1700, saponification degree: 98%) was dissolved in ion-exchanged water to obtain a PVA aqueous solution having a solid content of 8.0% by mass. And this produced PVA117 solution and the PVA420 solution of Example 1 were mixed in the ratio of PVA117: PVA420 = 1: 1 on a mass basis. Thereafter, the PVA solution prepared above was mixed with colloidal sol A prepared as described above so that the PVA solid content conversion was 9 parts by mass with respect to 100 parts by mass of the solid content of the alumina hydrate.

  Next, a 3.0% by mass boric acid aqueous solution was added in an amount of 1.8 parts by mass in terms of boric acid solid content with respect to 100 parts by mass of alumina hydrate (0.7 equivalent based on the mixture of PVA117 and PVA420). ) Were mixed. Then, a coating liquid C for the ink receiving layer A was obtained.

  An ink jet recording medium 16 was produced in the same manner as in Example 1 except that the coating liquid A for the ink receiving layer A was changed to the coating liquid C in Example 1.

Example 17
The PVA117 solution of Example 16 and the PVA235 solution of Example 1 were mixed at a ratio of PVA117: PVA235 = 1: 1 based on mass. Thereafter, the prepared mixed PVA solution was mixed with colloidal sol B prepared as described above so as to be 9 parts by mass in terms of PVA solid content with respect to 100 parts by mass of solid content of alumina hydrate.

  Next, the 3.0 mass% boric acid aqueous solution was added to 1.9 mass parts in terms of boric acid solid content with respect to 100 mass parts of the solid content of alumina hydrate (0.7 equivalent to the mixture of PVA117 and PVA235). ) Were mixed. And the coating liquid D for ink receptive layers B was obtained.

  An ink jet recording medium 17 was produced in the same manner as in Example 1 except that the coating liquid B for the ink receiving layer B was changed to the coating liquid D in Example 1.

Example 18
In Example 1, except that the coating liquid A for the ink receiving layer A was changed to the coating liquid C, and the coating liquid B for the ink receiving layer B was changed to the coating liquid D, respectively. Thus, an inkjet recording medium 18 was produced.

Example 19
An ink jet recording medium 19 was produced in the same manner as in Example 1 except that the coating amount of the ink receiving layer A was changed to 10 g / m ² in Example 1.

Example 20
Inkjet recording medium 20 was produced in the same manner as in Example 1 except that the coating amount of the ink receiving layer A was changed to 15 g / m ² in Example 1.

Example 21
An ink jet recording medium 21 was produced in the same manner as in Example 1 except that the coating amount of the ink receiving layer A was changed to 3 g / m ² in Example 1.

[Comparative Example 1]
In Example 1, with respect to the coating liquid A for the ink receiving layer A, 0.2 parts by mass in terms of boric acid solid content (0.1 equivalent to PVA420) with respect to 100 parts by mass of the solid content of alumina hydrate. ). Except for this, an inkjet recording medium 22 was produced in the same manner as in Example 1.

[Comparative Example 2]
In Example 1, with respect to the coating liquid A for the ink-receiving layer A, 2.7 parts by mass in terms of boric acid solid content (1.3 equivalents with respect to PVA420) with respect to 100 parts by mass of the solid content of alumina hydrate. ). Except for this, an inkjet recording medium 23 was produced in the same manner as in Example 1.

[Comparative Example 3]
An ink jet recording medium 24 was produced in the same manner as in Example 1 except that the boric acid aqueous solution was removed from the coating liquid A for the ink receiving layer A in Example 1.

[Comparative Example 4]
In Example 1, with respect to the coating liquid B for the ink receiving layer B, 0.3 parts by mass in terms of boric acid solid content (0.1 equivalent to PVA235) with respect to 100 parts by mass of the solid content of alumina hydrate. ). Except for this, an inkjet recording medium 25 was produced in the same manner as in Example 1.

[Comparative Example 5]
In Example 1, with respect to the coating liquid B for the ink receiving layer B, 3.0 parts by mass in terms of boric acid solid content (1.2 equivalents relative to PVA235) with respect to 100 parts by mass of the solid content of alumina hydrate. ). Other than this, an inkjet recording medium 26 was produced in the same manner as in Example 1.

[Comparative Example 6]
In Example 1, with respect to the coating liquid B for the ink receiving layer B, 3.3 parts by mass in terms of boric acid solid content (1.3 equivalents with respect to PVA235) with respect to 100 parts by mass of the solid content of alumina hydrate. ). Other than this, an inkjet recording medium 27 was produced in the same manner as in Example 1.

[Comparative Example 7]
An ink jet recording medium 28 was produced in the same manner as in Example 1 except that the boric acid aqueous solution was removed from the coating liquid B for the ink receiving layer B in Example 1.

[Comparative Example 8]
In Comparative Example 2, with respect to the coating liquid B for the ink receiving layer B, 3.0 parts by mass in terms of boric acid solid content (1.2 equivalents relative to PVA235) with respect to 100 parts by mass of the solid content of alumina hydrate. ). Except for this, an inkjet recording medium 29 was produced in the same manner as in Comparative Example 2.

[Comparative Example 9]
In Comparative Example 2, with respect to the coating liquid B for the ink receiving layer B, 3.3 parts by mass in terms of boric acid solid content (1.3 equivalents with respect to PVA235) with respect to 100 parts by mass of the solid content of alumina hydrate. ). Except for this, an inkjet recording medium 30 was produced in the same manner as in Comparative Example 2.

[Comparative Example 10]
In Comparative Example 1, with respect to the coating liquid B for the ink-receiving layer B, 0.3 parts by mass in terms of boric acid solid content (0.1 equivalent to PVA235) with respect to 100 parts by mass of the solid content of alumina hydrate. ). Except for this, an inkjet recording medium 31 was produced in the same manner as in Comparative Example 1.

[Comparative Example 11]
In Comparative Example 3, an inkjet recording medium 32 was produced in the same manner as in Comparative Example 3 except that the boric acid aqueous solution was removed with respect to the coating liquid B for the ink receiving layer B.

[Comparative Example 12]
In Example 1, with respect to the coating liquid B for the ink receiving layer B, the PVA type was changed from PVA235 to PVA117. Moreover, it changed so that it might become 0.6 mass part (0.2 equivalent with respect to PVA117) in conversion of boric acid solid content with respect to 100 mass parts of solid content of an alumina hydrate. Other than this, an inkjet recording medium 33 was produced in the same manner as in Example 1.

[Comparative Example 13]
In Comparative Example 12, with respect to the coating liquid B for the ink receiving layer B, 2.1 parts by mass in terms of boric acid solid content (0.7 equivalent to PVA117) with respect to 100 parts by mass of the solid content of alumina hydrate. ). Except this, an inkjet recording medium 34 was produced in the same manner as in Comparative Example 12.

[Comparative Example 14]
In Comparative Example 12, with respect to the coating liquid B for the ink receiving layer B, 3.7 parts by mass in terms of boric acid solid content with respect to 100 parts by mass of the solid content of alumina hydrate (1.2 equivalents with respect to PVA117) ). Except for this, an inkjet recording medium 35 was produced in the same manner as in Comparative Example 12.

[Comparative Example 15]
In Comparative Example 14, with respect to the coating liquid A for the ink receiving layer A, 2.5 parts by mass in terms of boric acid solid content (1.2 equivalents relative to PVA420) with respect to 100 parts by mass of the solid content of alumina hydrate. ). Other than this, an inkjet recording medium 36 was produced in the same manner as in Comparative Example 14.

[Comparative Example 16]
An ink jet recording medium 37 was produced in the same manner as in Example 1 except that the coating liquid B for the ink receiving layer B was changed to the coating liquid A in Example 1.

[Comparative Example 17]
In Comparative Example 16, the coating liquid A was changed to 2.5 parts by mass in terms of boric acid solids (1.2 equivalents to PVA420) with respect to 100 parts by mass of alumina hydrate. did. Except for this, an inkjet recording medium 38 was produced in the same manner as in Comparative Example 16.

[Comparative Example 18]
An ink jet recording medium 39 was produced in the same manner as in Example 1 except that the coating liquid A for the ink receiving layer A was changed to the coating liquid B in Example 1.

[Comparative Example 19]
In the comparative example 18, regarding the coating liquid B, it changed so that it might become 2.8 mass parts (1.1 equivalent with respect to PVA235) in conversion of boric acid solid content with respect to 100 mass parts of solid content of an alumina hydrate. did. Except for this, an inkjet recording medium 40 was produced in the same manner as in Comparative Example 18.

[Comparative Example 20]
In Example 1, with respect to the coating liquid A for the ink receiving layer A, the PVA type was changed from PVA420 to PVA235. Moreover, it was made to become 1.8 mass parts (0.7 equivalent with respect to PVA235) in conversion of boric acid solid content with respect to 100 mass parts of solid content of an alumina hydrate.

In Example 1, with respect to the coating liquid B for the ink receiving layer B, the PVA type was changed from PVA235 to PVA117. Moreover, it changed so that it might become 2.1 mass parts (0.7 equivalent with respect to PVA117) in conversion of boric acid solid content with respect to 100 mass parts of solid content of an alumina hydrate.
Other than this, an inkjet recording medium 41 was produced in the same manner as in Example 1.

[Comparative Example 21]
In Example 1, with respect to the coating liquid A for the ink receiving layer A, the PVA type was changed from PVA420 to PVA235. Moreover, it was made to become 2.3 mass parts (0.9 equivalent with respect to PVA235) in conversion of boric acid solid content with respect to 100 mass parts of solid content of an alumina hydrate.

In Example 1, with respect to the coating liquid B for the ink receiving layer B, the PVA type was changed from PVA235 to PVA117. Moreover, it changed so that it might become 3.7 mass parts (1.2 equivalent with respect to PVA117) in conversion of boric acid solid content with respect to 100 mass parts of solid content of an alumina hydrate.
Other than this, an inkjet recording medium 42 was produced in the same manner as in Example 1.

<Evaluation method>
(Ink absorption)
Ink for a pigment ink printer (product name: PIXUS Pro 9500 Canon) was refilled in a dedicated ink tank of a photo printer (product name: PIXUS iP8600 Canon product) using an inkjet method. In super photo paper mode (standard setting), gradation batches of 0% to 150% Duty of secondary colors red, green, and blue were printed on the recording surface of the inkjet recording medium. And it evaluated as follows by visual observation of a printing part.
A: No beading is confirmed even at 150% duty.
B: No beading is confirmed at 135% duty.
C: No beading is confirmed at 120% duty.
D: Beading is confirmed even at 120% duty.

(Occurrence of cracks)
After cutting each recording medium into A4 size, five sheets were visually observed and evaluated in three stages. The evaluation criteria were as follows.
A: Good with no occurrence of cracks.
B: Although cracks are slightly confirmed, there is no practical problem.
C: Many cracks are confirmed.
Tables 1 and 2 show the evaluation results of the ink jet recording media produced in the above Examples , Reference Examples and Comparative Examples. The contact angle of each layer is as shown in Tables 1 and 2.

  In each Example, the amount of the crosslinking agent (boric acid) in each layer was set to 0.2 equivalent or more with respect to the amount of PVA in each layer. Further, the contact angle a of the ink receiving layer A with respect to pure water is set larger than the contact angle b of the ink receiving layer B with respect to pure water, and 30 ° <a ≦ 50 ° and 30 ° ≦ b <50.

  As can be seen from the results of Table 1, in these examples, “ink absorbability” and “crack” are both “A” or “B”, and it can be seen that the desired effects are exhibited.

  On the other hand, as shown in Table 2, in the comparative example, an ink jet recording medium in which the contact angles a and b do not satisfy the relationship of a> b, 30 ° <a ≦ 50 °, 30 ° ≦ b <50 ° at the same time. Formed. In this case, neither “ink absorbability” nor “crack” becomes “A” or “B”, and the configuration of the comparative example achieves both excellent ink absorbency and prevention of cracking at the same time. Proves difficult.

Claims (3)

An inkjet recording method for recording an image by applying a pigment ink to an inkjet recording medium,
The inkjet recording medium has a support and at least two or more porous ink receiving layers on the support,
The porous ink receiving layer is obtained by applying a coating liquid for a porous ink receiving layer containing an inorganic pigment, polyvinyl alcohol and boric acid,
The boric acid content in each porous ink receiving layer coating solution is 0.2 equivalents or more of the polyvinyl alcohol content,
The contact angle a with respect to pure water of the porous ink receiving layer (ink receiving layer A) constituting the outermost layer and the contact with pure water of the porous ink receiving layer (ink receiving layer B) immediately below the ink receiving layer A The angle b satisfies the following relational expression (A),
An ink jet recording method, wherein the saponification degree of polyvinyl alcohol contained in the ink receiving layer A is lower than the saponification degree of polyvinyl alcohol contained in the ink receiving layer B.
a> b, 30 ° <a ≦ 50 °, 30 ° ≦ b <50 ° (A). The coating amount of the ink receiving layer A after drying is 3 g / m. ² 10 g / m or more ² The inkjet recording method according to claim 1, wherein: 3. The porous ink receiving layer according to claim 1, wherein all of the porous ink receiving layer is formed by repeating the step of applying the coating liquid for the porous ink receiving layer twice or more. The inkjet recording method as described.