JP2003094792A - Ink jet recording method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet recording method improving a feeling of physical disorder due to the gloss difference between a printed part and an unprinted part, capable of reducing the glittering feeling of the printed part and capable of obtaining high printing density. SOLUTION: In the ink jet recording method using yellow, magenta and cyan pigment inks on a recording medium having an ink absorbing layer on a support, the recording medium is characterized in that the 60 deg. mirror surface gloss prescribed in JIS-Z-8741 of the surface on the surface side of the ink absorbing layer is 10-30%, center line average surface roughness Ra prescribed in JISB-0.601 is 0.6-4.0 μm, a Bristol penetration speed is 20-100 ml/m<2> sec<1/2> and at least one of the pigment inks contains pigment particles with an absolute value of zeta potential of 30-100 mV.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inkjet image recording method, and more particularly, to an inkjet recording method which reduces the difference in gloss between a printed portion and a non-printed portion and the glare of the printed portion and has a high print density. Regarding

[0002]

2. Description of the Related Art In recent years, along with the widespread use of digital cameras or computers, hard copy image recording technology for recording those images on a paper surface has been rapidly developed. The ultimate goal of these hard copies is to bring their image quality closer to that of silver halide photography, especially color reproducibility,
The goal of development is to bring color density, texture, resolution, gloss, light resistance, etc. closer to those of silver halide photography.

As such a hard copy recording system,
In addition to a method of directly photographing a display on which an image is displayed by a silver salt photograph, various recording methods such as a sublimation type thermal transfer method, an inkjet method and an electrostatic recording method have been proposed and put into practical use. Among these recording methods, inkjet printers have been rapidly popularized in recent years because they have the advantages of easy full-color printing and low printing noise.

The ink jet recording method is capable of recording a high-definition image with a relatively simple device, and is rapidly developing in various fields. Further, there are various uses, and a recording medium or ink suitable for each purpose is used.

The recording medium used in the ink jet recording method is one in which the ink receiving layer is a support itself such as paper such as plain paper, or a support which also serves as an absorber such as coated paper. An ink absorption layer is applied,
Alternatively, there is one in which an ink absorbing layer is coated on a non-absorbent support such as resin-coated paper or polyester film. Among them, a recording medium of a type in which an ink absorbing layer is coated on a non-absorptive support has a high surface smoothness of the support and has less waviness, and therefore, silver salts such as glossiness, gloss and depth. It is preferably used for output that requires a high-quality texture such as a photograph. Furthermore, as a glossy recording medium having a high glossiness and glossiness, a swelling type recording medium in which a water-soluble binder such as polyvinylpyrrolidone or polyvinyl alcohol is coated as an ink absorbing layer on a non-absorbent support, A so-called void type recording medium is used as an ink absorbing layer in which a fine void structure is formed by a pigment or a pigment and a binder and the ink is absorbed in the voids.

On the other hand, the ink is roughly classified into a dye ink in which a coloring material is dissolved in a solvent and a dispersed ink in which the coloring material is dispersed in a solvent. Since the dye ink is dissolved in a solvent, it tends to have good color developability and high saturation, and is preferably used for outputting silver salt photographic images and the like. However, the dye ink is basically prone to fading, and when posting for a certain period like a signboard or poster,
If the surface is not laminated, there is a problem of fading immediately. On the other hand, the dispersed ink is generally less prone to photobleaching, and is preferably used for the production of posters such as posters. Dispersion inks used to have a large particle size of dispersed particles, mainly from the viewpoint of ensuring dispersion stability, and were completely unsuitable for silver salt photographic printing.
Due to recent advances in dispersion technology, the dispersion particle size has been reduced and silver salt photographic printing has come to be performed. Here, as the coloring material of the dispersed ink, for example, an organic pigment, an inorganic pigment, and colored fine particles are used.

In recent years, ink-jet recording has also been made higher in definition, and printing is often performed to obtain a high-quality texture of silver salt photographs. When performing printing that requires such a high texture, a glossy recording medium such as the swelling recording medium or the void recording medium described above is preferably used.

When the above dye ink is recorded, the entire ink penetrates into the ink absorption layer, so that the surface of the medium after recording is almost the same as that before recording, and the boundary between the non-image portion and the recording portion. There was not much discomfort at the time. On the other hand, when the dispersed ink is recorded on the glossy recording medium, even if the ink absorbing layer has no holes like the swelling type recording medium, or even if it has the holes like the void type recording medium, the hole diameter Since the particle diameter of the coloring material is larger than that of the above, most of the dispersed coloring material cannot enter the inside of the ink absorbing layer and is exposed on the surface of the recording medium. As a result,
In the dispersed ink recording portion, a new surface is formed by the dispersed coloring material exposed on the surface of the medium. Therefore, the smoothness of the surface changes from the original medium surface depending on the deposition state of the exposed coloring material. This change in smoothness appears as a change in glossiness, and the gloss is different between the recorded portion of the image and the non-image portion. If there is a difference in gloss within one recording medium, it feels very uncomfortable and is perceived as far from the homogeneity of silver halide photography. In particular, in the conventional dispersion ink, the surface smoothness tends to be considerably rough from the original recording medium surface due to the coloring material deposited on the recording medium surface, the glossiness is lowered, and an image with a strong discomfort is likely to be formed. Had.

As a method of eliminating such an uncomfortable feeling, a method of laminating after image recording and a method of pressing with a hot roll after image formation are known, but the processing is required after the image formation, which is troublesome. Further, it has drawbacks such that relatively large energy is consumed and that a laminate material and a dedicated recording medium are required, and thus there is a demand for urgent development of improvement means.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object thereof is to improve a feeling of discomfort due to a difference in gloss between a printed portion and a non-printed portion and to prevent glare in the printed portion. An object of the present invention is to provide an ink jet recording method capable of reducing the feeling and obtaining a high print density.

[0011]

The above objects of the present invention have been achieved by the following constitutions.

1. In an inkjet recording method of recording with a yellow pigment ink, a magenta pigment ink, and a cyan pigment ink on a recording medium having at least one ink absorbing layer on a support, the recording medium is 6 specified in JIS-Z-8741
0 degree specular gloss is 10 to 30%, center line average surface roughness Ra prescribed by JISB-0601 is 0.6 to 4.0 μm.
And has a Bristow permeation rate of 20 to 100 ml / m ^2.
An ink jet recording method characterized in that it is sec ^1/2 and at least one of the pigment inks contains pigment particles having an absolute value of zeta potential of 30 to 100 mV.

2. Maximum particle size of the pigment particles (D99)
Is less than 300 nm, the inkjet recording method described in the item 1 above.

3. Average particle diameter of the pigment particles (D50)
Is 35 to 120 nm. 3. The ink jet recording method as described in 1 or 2 above.

4. 400 to 700n represented by the formula 1
The ink absorbance ε at m is 10,000 or more and 50,000 or less for yellow ink, magenta ink, or cyan ink, and 50,000 or more and 150,000 or less for black ink. Inkjet recording method described.

5. 1 to 4 above, wherein the inkjet recording medium contains a cationic polymer.
The inkjet recording method according to any one of items.

In view of the above-mentioned problems, the present inventors have obtained a difference in gloss due to a difference in height between a printed portion and a non-printed portion of a formed ink jet output image, a glaring sensation in the printed portion, and a desired density. As a result of earnestly studying the problems that cannot be solved, the 60-degree specular gloss of the printing surface of the recording medium to be used is set to a specific range, and the center line average surface roughness Ra of the printing surface of the recording medium is set to a specific value. Range, and the Bristow absorption rate, which is one guideline of the ink absorption rate, is specified under specific conditions, and at least one color of pigment ink is
By containing pigment particles having an absolute value of zeta potential of 30 to 100 mV, it is possible to remarkably improve the inhomogeneity and glare caused by the difference in texture between the printed part and the non-printed part, which tends to occur during printing with pigment ink. It was found that a smooth print and a texture similar to those of a silver salt photograph can be obtained and a high print density can be obtained.

Further, the above effects are further exhibited by setting the particle size of the pigment within a specific range, using pigment particles having a specific ink absorbance, or using a cationic polymer for the recording medium. After finding out the above, the present invention has been completed.

The details of the present invention will be described below. In the inkjet recording method of the present invention, the 60-degree specular gloss defined by JIS-Z-8741 on the ink absorption layer surface side is 10 to 30%, and the center line average surface roughness Ra defined by JISB-0601 is 0.6 to 4.0 μm,
And the Bristow penetration rate is 20 to 100 ml / m ² · s
A characteristic feature is that a pigment ink containing pigment particles having an absolute value of zeta potential of at least one color of 30 to 100 mV is printed on an inkjet recording medium having an ec ^1/2 .

First, the ink jet recording medium according to the present invention will be described. The inkjet recording medium (hereinafter, simply referred to as a recording medium) according to the present invention has an ink absorbing layer on the ink printing surface of a support.

As the support used in the recording medium according to the present invention, either a water-absorbent support or a non-water-absorbent support can be used, but the non-water-absorbent support does not cause wrinkles and is easily formed. It is preferable because a semi-glossy surface can be formed.

Examples of the water-absorbent support that can be used in the present invention include general paper, cloth, sheets and plates having wood, etc. Most preferable because it is excellent and cost effective.

The paper support can be produced by mixing the above-mentioned fibrous substances such as wood pulp and various additives with various paper machines such as a Fourdrinier paper machine, a cylinder paper machine and a twin wire paper machine. . Further, if necessary, it may be subjected to size press treatment with starch, polyvinyl alcohol or the like in a papermaking stage or a papermaking machine, various coat treatments, and calendar treatment.

Examples of the non-water-absorptive support include a plastic resin film support or a support in which both sides of paper are coated with a plastic resin film.

As the plastic resin film support, polyester film, polyvinyl chloride film,
Examples thereof include polypropylene film, cellulose triacetate film, polystyrene film and the like. These plastic resin films may be transparent or translucent, but are preferably transparent.

In the recording medium according to the present invention, the use of a paper support in which both sides of the paper support are laminated with polyethylene or the like allows a recorded image to be close to a photographic image quality and a high quality image to be obtained at low cost. , Particularly preferred. A paper support laminated with such polyethylene will be described below.

The base paper used for the paper support is mainly made of wood pulp, and if necessary, synthetic paper such as polypropylene or synthetic fiber such as nylon or polyester is used in addition to wood pulp. As wood pulp, LBKP, LBSP, NBKP, NBSP,
Any of LDP, NDP, LUKP, and NUKP can be used, but LBKP, NBSP, which has a large amount of short fibers,
It is preferable to use more LBSP, NDP, and LDP. However, the ratio of LBSP and / or LDP is 1
0 mass% or more and 70 mass% or less are preferable.

As the above-mentioned pulp, a chemical pulp containing few impurities (sulfate pulp or sulfite pulp) is preferably used, and a pulp whose whiteness is improved by bleaching is also useful. The base paper contains sizing agents such as higher fatty acids and alkyl ketene dimers, white pigments such as calcium carbonate, talc and titanium oxide, paper strength enhancers such as starch, polyacrylamide and polyvinyl alcohol, optical brighteners and polyethylene glycols. A water retention agent such as, a dispersant, and a softening agent such as quaternary ammonium can be appropriately added.

The freeness of pulp used for papermaking is CSF.
Is preferably 200 to 500 ml, and the fiber length after beating is 30 to 70% of the sum of the mass% of the 24 mesh residue and the mass% of the 42 mesh residue defined in JIS-P-8207. preferable. The mass% of the 4-mesh residue is preferably 20 mass% or less. The basis weight of the base paper is preferably 30 to 250 g / m ² , and particularly 50 to ²
00 g / m ² is preferred. The thickness of the base paper is 40-250μ
m is preferred. The base paper can be given a high smoothness by calendering at the papermaking stage or after the papermaking. Base paper density is 0.7 to 1.2 g / m ² (JIS-P-8118)
Is common. Furthermore, the stiffness of base paper is JIS-P-814.
20 to 200 g is preferable under the conditions specified in 3. A surface sizing agent may be applied to the surface of the base paper, and as the surface sizing agent, the same sizing agent as that which can be added to the base paper can be used. The pH of the base paper is preferably 5 to 9 when measured by the hot water extraction method specified in JIS-P-8113.

The polyethylene covering the front and back surfaces of the base paper is mainly low-density polyethylene (LDPE) and / or high-density polyethylene (HDPE), but in addition, LLDPE (linear rhodity polyethylene), polypropylene, etc. Can be used. In particular, the polyethylene layer on the ink absorption layer side is preferably one in which rutile or anatase type titanium oxide is added to polyethylene to improve opacity and whiteness, as is widely used in photographic printing paper. The titanium oxide content is usually 3 to 20 mass% with respect to polyethylene,
It is preferably 4 to 13% by mass.

The polyethylene-coated paper can be used as a glossy paper, and when polyethylene is melt-extruded and coated on the surface of a raw paper, a so-called patterning treatment is performed to obtain a matte surface which can be obtained by ordinary photographic printing paper. Those having a silky surface can also be used in the present invention.

The amount of polyethylene used on the front and back of the base paper is selected so as to optimize curling under low humidity and high humidity after providing the void layer and the back layer, but usually the polyethylene layer on the void layer side is used. Is 20 to 40 μm, and the back layer side is 10
It is in the range of 30 μm.

Further, the polyethylene-coated paper support preferably has the following characteristics.

1. Tensile strength: JIS-P-8113
It is preferable that the strength is 20 to 300 N in the vertical direction and 10 to 200 N in the horizontal direction with the strength defined in 2. Tear strength: A method defined in JIS-P-8116, 0.1 to 20 N in the longitudinal direction and 2 to 20 N in the lateral direction.
Is preferred. Compression modulus ≧ 98.1 MPa 4. Surface Beck smoothness: 20 seconds or more is preferable as a glossy surface under the conditions specified in JIS-P-8119,
It may be less than this for so-called typed products. Opacity: When measured by the method specified in JIS-P-8138, 80% or more, particularly 85 to 98% is preferable. Whiteness: L ^* specified by JIS-Z-8729,
a ^* and b ^* are L ^* = 80 to 95, a ^* = − 3 to +5, b ^*
7. It is preferable that it is = -6 to +2. Clark stiffness: Clark stiffness in the conveying direction of the recording medium is a 50~300cm ^2/100 support is preferably 8. Water content of inner paper: usually 2 to 100% by mass, preferably 2 to 6% by mass relative to the inner paper. In the recording medium of the present invention, the ink absorption layer side surface is defined by JIS-Z-8741 60. Specular gloss is 1
One characteristic is that the center line average surface roughness Ra defined by JISB-0601 is 0 to 30% and is 0.6 to 4.0 μm, but the characteristic value of the ink absorption layer surface side defined above is The means for achieving the above is not particularly limited, but a method for providing irregular or regular fine-grained surface irregularities on the surface of the recording medium by the method described below is preferable.

The unevenness in the present invention is defined in JISB-0601 with respect to the surface of the ink absorption layer side defined in the present invention from the viewpoint of preventing glare from being noticeably reduced and preventing glare. Standard length 2.5m
m, the center line average surface roughness Ra when measured at a cutoff value of 0.8 mm is 0.6 to 4.0 μm, and JIS-Z-8.
It is necessary to provide unevenness such that the 60-degree specular gloss of 741 satisfies 10 to 30%.

Due to the unevenness, the surface glossiness is appropriately suppressed and unnecessary glare is eliminated. Further, the glossiness at the time of ink jet recording does not have a large difference between the printed portion and the non-printed portion, resulting in a uniform visual appearance. You can get high quality prints.

Such surface characteristics obtained with the present invention are:
Conventionally, the matting agent used for the ink absorbing layer cannot be obtained by including fine particles having a particle size of about 0.5 to 50 μm as a matting agent in a flat ink absorbing layer.

When a matting agent is contained, a convex state is usually formed mainly on the surface of the ink absorbing layer. In order to suppress the gloss to some extent only by this convexity, it is necessary to use a matting agent that is considerably larger than the above-mentioned particle size, but if this is done, the surface roughness will become too large, and as a result, it will be easily scratched or the print surface will feel Aggravate. Therefore, the method of incorporating the matting agent into the ink absorbing layer cannot satisfy both the surface roughness and the glossiness.

As described above, the roughness of the surface of the ink absorbing layer according to the present invention is the center line surface roughness when measured with a standard length of 2.5 mm and a cutoff value of 0.8 mm specified in JISB-0601. Ra is 0.6 to 4.0 μm,
60-degree specular gloss of JIS-Z-8741 is 10
The roughness is such that 30% is satisfied, but Ra is 0.6.
If it is less than μm, the effect of suppressing glare on the surface is lost, and if Ra exceeds 4.0 μm, the ink is likely to accumulate in the concave portions, and uneven spots are likely to occur. Further, when the ink absorption layer is a hard porous film having voids, if Ra exceeds 4.0 μm, the film is likely to be cracked during production. Preferably Ra ranges from 0.9 to
It is 3.0 μm.

The center line surface roughness Ra of the back surface of the recording medium according to the present invention is preferably 0.6 to 2.5 μm, more preferably 0.8 to 2.2 μm.

The recording medium according to the present invention has relatively large irregularities having a regular shape or an irregular shape on the surface of the ink absorbing layer. May be provided with an ink absorbing layer, or a smooth support may be provided with the ink absorbing layer, and then the surface may be shaped, but when the ink absorbing layer is post-treated, The former is preferable because it is difficult to form uniform unevenness. The latter is preferable when the ink absorption layer is a relatively hard porous film.

In the case of a support in which both sides of paper, which is a particularly preferred support, are coated with polyethylene resin, it is preferable to engrave the surface after coating the paper with polyethylene resin.

A typical method of previously forming irregularities on the surface of a polyethylene resin is to perform extrusion coating of a molten polyethylene resin on a base paper, and then press-contact with a molding roller to form a pattern of fine irregularities. Be seen.

As the method of patterning, a resin-coated paper obtained by melt extrusion is subjected to an embossing calendar treatment at around room temperature, and a cooling roll having a pattern engraved on the roll surface at the time of extrusion coating of polyethylene resin is used. Then, there is a method of forming unevenness while cooling, but the latter is preferable because it is possible to mold with a relatively weak pressure, and more accurate and uniform molding is possible.

The relationship between the irregularities on the surface of the support and the surface of the ink-absorbing layer depends on the characteristics of the ink-absorbing layer, but the ink-absorbing layer has a high ink-absorbing speed and has voids that allow printing with higher image quality. In the case of a porous film, since the dry film thickness becomes thicker, the height difference on the surface of the support tends to decrease.

In the case of an ink jet recording paper obtained by applying an ink absorbing layer to a support having irregularities on its surface in advance, the surface roughness of the support is higher than the desired height difference of the irregularities on the surface of the ink absorbing layer. The surface roughness of the support has a center line average roughness (Ra) of 1 when measured at a standard length of 2.5 mm and a cutoff value of 0.8 mm specified in JIS B-0601. It is preferable that the support has an irregular or regular shape of 0.0 to 5.0 μm. Ra of a particularly preferred support is 1.0 to 4.0.
belongs to.

As a result, the recording medium according to the present invention produced using such a support has a specular gloss of 10 to 30 according to JIS-Z-8741 on the surface on the ink absorbing layer side.
%, And preferably the unevenness is formed on the surface of the ink absorbing layer.

The surface glossiness is affected by the above-mentioned unevenness of the support, the fine structure itself of the ink absorbing layer itself and the matting agent used as an auxiliary.

When the glossiness is less than 10%, the matting degree of the surface is too high, and an unclear image tends to be formed.
After ink jet recording, uneven gloss (glare) tends to be conspicuous due to a slight difference in gloss on the image surface.

On the other hand, when the glossiness exceeds 30%,
Generally, the glossiness of the image surface is high and it is difficult to call it a semi-glossy surface. Particularly preferred glossiness is in the range of 12 to 25%.

The glossiness in such a range can be obtained by making the outermost surface layer of the ink absorbing layer as uniform as possible to reduce unnecessary fine particles that lower the gloss as much as possible.

A so-called matting agent may be contained on the outermost surface of the ink absorbing layer, but it should be used within a range that does not significantly impair the gloss. As such a matting agent, it is preferable to use one having an average particle size of usually about 5 to 30 μm.

Next, the ink absorbing layer provided on the support will be described. The ink absorption layer may be provided on only one side of the support, or may be provided on both sides. At this time, the ink absorbing layers provided on both sides may be the same or different.

The recording medium according to the present invention is characterized in that the Bristow permeation rate is 20 to 100 ml / m ² · sec ^1/2 , and preferably 30 to 70 ml / m ^2.
・ It is sec ^1/2 . Bristow penetration rate of 20 ml /
If it is less than m ² · sec ^1/2 , the aggregation of the ink on the surface of the recording medium may occur and the glossiness may be deteriorated.
When it exceeds 0 ml / m ² · sec ^1/2 , the concentration is lowered.

The Bristow permeation rate referred to in the present invention is
J. TAPPI paper pulp test method No. Based on the liquid absorption test method for paper and paperboard of No. 51-87 (Bristow method), the speed setting was set to 0.2 mm / s (that is, contact time) using the test apparatus (Bristow test machine) described here. 5 seconds) and can be measured. When the transfer amount is measured using a Bristow tester, the transfer amount V
(Ml / m ² ) is the amount that actually permeated the paper (ml / m ² ).
m ² ) and roughness index Vr (ml / m ² ) which is irrelevant to permeation and is due to surface irregularities. In a normal ink jet recording sheet, since the glossiness is high and the surface smoothness is also high, the value of the roughness index Vr is small, and it is negligibly small compared with the transfer amount of the contact time of 5 seconds.

Therefore, the absorption amount in the present invention is defined by J. T
APPI paper pulp test method No. Using the Bristow tester described in No. 51-87, a transfer amount of 5 seconds in contact time can be obtained.

In the measurement, distilled water or pure water used for convenience of measurement may be colored.
For coloring, J. TAPPI paper pulp test method No. 51
In addition to malachite green described in the -87 Bristow method, water-soluble dyes such as Direct Blue 199 can be preferably used.

More specifically, the principle of measuring the permeation rate of the ink liquid into the paper by the Bristow method will be described.

The ink was sampled with a 40 μl microsyringe and p (nozzle gap) = 1 mm, w (nozzle width) = 1.75 cm from the nozzle opening, υ (paper moving speed) = 0.5- It is permeated and transferred onto a paper rotating at a speed of 50 mm / sec. The transition length at this time is L (cm)
At this time, the ink permeation amount V is obtained by the following equation 2.

[0060]

[Equation 2]

The transition time t at that time is t = p / υ = 1.
It is 0 / υ (sec). The following Lucas-Washburn's relational expression (Equation 3) is known as a theoretical expression when the penetration of ink progresses in the capillary of the paper due to the penetration and wetting of the ink.

[0062]

[Equation 3]

In the equation, γ: radius of capillary tube of paper, γ: surface tension of ink, θ: contact angle of ink with ink, η: viscosity of ink, and therefore V is expected to be proportional to √t. . In reality, ink transfer occurs instantaneously due to the roughness of the paper surface. When this transfer amount is V ₀ , the following equation 4 is obtained,

[0064]

[Equation 4]

The permeation rate is d (V-V ₀ ) / d√t (ml
/ M ² · sec ^1/2 ). In the present invention, the Bristow permeation rate of the recording medium is 25 ml / m ² · sec.
^As a method of ^1/2 or more, for example, the type of inorganic fine particles described below, the addition amount, or the type of hydrophilic binder,
This can be achieved by appropriately selecting or combining constituent conditions such as an addition amount.

Regarding the ink jet recording medium according to the present invention, constituent factors other than those described above will be described below.

The ink absorbing layer according to the present invention may be a so-called swelling type ink absorbing layer containing a hydrophilic binder as a main constituent component, or a void type ink absorbing layer containing a small amount of binder and a large amount of fine particles. May be
The void-type ink absorbing layer is preferable from the viewpoint of good ink absorbability.

The void-type ink absorbing layer is mainly formed of a small amount of binder and fine particles. As the fine particles used in the present invention, inorganic fine particles are those which give a higher color density and which have a smaller particle size. It is preferable because it is easily obtained.

The inorganic fine particles preferably used in the recording medium according to the present invention will be described. As inorganic fine particles,
Various solid particles known in the related art can be used in conventional inkjet recording paper.

Examples of the inorganic fine particles include light calcium carbonate, heavy calcium carbonate, magnesium carbonate, kaolin, clay, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc hydroxide, zinc sulfide and carbonic acid. Zinc, hydrotalcite, aluminum silicate, diatomaceous earth, calcium silicate, magnesium silicate,
Synthetic amorphous silica, colloidal silica, alumina, colloidal alumina, pseudo-boehmite, aluminum hydroxide,
Examples thereof include white inorganic pigments such as lithopone, zeolite, and magnesium hydroxide.

The above-mentioned fine particles may be used in a state of being uniformly dispersed in a binder as primary particles, or may be added in a state of forming secondary aggregated particles and being dispersed in a binder. Good, but the latter is more preferred.

The shape of the above-mentioned inorganic fine particles is not particularly limited in the present invention, and may be spherical, rod-shaped, needle-shaped, plate-shaped or beaded. The inorganic fine particles have an average particle size of 3 to 20.
It is preferably 0 nm. When fine particles having an average particle size of more than 200 nm are used, the glossiness of the recording paper is reduced, or the maximum density is reduced due to light scattering on the surface, making it difficult to obtain a clear image. The lower limit of the average particle size is not particularly limited, but is generally 3 from the viewpoint of particle production.
nm or more, particularly 6 nm or more is preferable. Particularly preferable inorganic fine particles have an average particle diameter of 10 to 100 nm.

In the above, the average particle size of the fine particles is obtained by observing the particle itself or the cross section or the surface of the void layer with an electron microscope, obtaining the particle size of a large number of arbitrary particles, and calculating the simple average value (number average) Desired. Here, each grain size is represented by a diameter assuming a circle equal to the projected area.

As the inorganic fine particles according to the present invention, even composite particles composed of the inorganic fine particles and a small amount of an organic substance (a low molecular compound or a high molecular compound may be used) are substantially regarded as the inorganic fine particles. Also in this case, the particle size of the highest order particles observed in the dry film is used as the particle size of the inorganic fine particles.

The mass ratio of organic / inorganic fine particles in the composite particles of the above inorganic fine particles and a small amount of organic matter is about 1/1.
It is 00 to 1/4.

The inorganic fine particles according to the present invention are preferably fine particles having a low refractive index from the viewpoints of low cost and high reflection density, and silica, particularly silica or colloidal synthesized by a vapor phase method. Silica is more preferred. Further, a cation surface-treated vapor phase method silica,
Cation surface-treated colloidal silica and alumina, colloidal alumina, pseudo-boehmite and the like can also be used.

The addition amount of the inorganic fine particles used in the void type ink absorbing layer largely depends on the required ink absorption capacity, the void ratio of the void layer, the type of the inorganic fine particles and the type of the hydrophilic binder. It is usually 3 to 30 g, preferably 5 to 25 g per 1 m ^{2 of the} recording paper. The mass ratio of the inorganic fine particles to the polyvinyl alcohol used in the void-type ink absorbing layer is usually 2: 1 to 20: 1.
It is particularly preferably 3: 1 to 10: 1.

The ink absorbing layer of the recording medium according to the present invention is
The ink absorption layer having a single layer structure or the ink absorption layer having a multi-layer structure may be used, but an ink absorption layer having a multi-layer structure that causes less color change when environmental humidity changes is more preferable.

The ink absorbing layer of the recording medium according to the present invention may contain a hardening agent. As the hardener, boric acid described above also has a hardener action, but in addition to this, an epoxy hardener (for example, diglycidyl ethyl ether, ethylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,6-diglycidyl cyclohexane, N, N-diglycidyl-4-glycidyloxyaniline, sorbitol polyglycidyl ether,
Glycerol polyglycidyl ether etc.), aldehyde type hardener (eg formaldehyde, glyoxal etc.), active halogen type hardener (eg 2,4-dichloro-4-hydroxy-1,3,5-s-triazine etc.) ), An active vinyl compound (for example, 1,3,5-trisacryloyl-hexahydro-s-triazine, bisvinylsulfonylmethyl ether, etc.), aluminum alum, an isocyanate compound and the like.

The amount of the hardener used varies depending on the type and amount of polyvinyl alcohol, the type of hardener, the type of inorganic fine particles, etc., but is usually 5 per 1 g of polyvinyl alcohol.
~ 500 mg, preferably 10-300 mg.

The invention according to claim 5 is characterized in that the recording medium contains a cationic polymer.

As the cationic polymer, known polymers can be used. Examples thereof include polyethyleneimine, polyallylamine, dicyandiamide polyalkylenepolyamine, a condensate of dialkylamine and epichlorohydrin, polyvinylamine, polyvinylpyridine, polyvinylimidazole. Examples thereof include condensates of diallyldimethylammonium salts and quaternary compounds of polyacrylic acid esters. Particularly, JP-A-10-193776,
Those described in JP-A-10-217601, JP-A-11-20300, and Japanese Patent Application No. 10-178126 are preferable.

In the present invention, the cationic polymer can be used without any particular limitation, but the particularly preferable one is
It has a weight average molecular weight of 2000 to 100,000.

As the polymer mordant, a cationic polymer mordant having a primary to tertiary amino group and a quaternary ammonium salt group is used. However, it does not cause discoloration or deterioration of light resistance with time, and the mordant ability of the dye. The cationic polymer mordant having a quaternary ammonium salt group is preferable because of its sufficiently high value.

The cationic polymer preferably used in the present invention is more preferably a polymer having a quaternary ammonium salt group, and particularly preferably a homopolymer or other copolymer of a monomer having a quaternary ammonium salt group. It is a copolymer with one or more monomers.

The following examples can be given as examples of the monomer having a quaternary ammonium salt group.

[0087]

[Chemical 1]

[0088]

[Chemical 2]

The monomer copolymerizable with the quaternary ammonium salt group is a compound having an ethylenically unsaturated group, and the following specific examples can be given.

[0090]

[Chemical 3]

Specific examples of the cationic polymer preferably used in the present invention are shown below, but the present invention is not limited thereto.

[0092]

[Chemical 4]

[0093]

[Chemical 5]

[0094]

[Chemical 6]

[0095]

[Chemical 7]

In particular, when the cationic polymer having a quaternary ammonium salt group is a copolymer, the ratio of the cationic monomer is usually 10 mol% or more, preferably 20 mol% or more, particularly preferably 30 mol% or more. is there.

The monomer having a quaternary ammonium salt group may be a single type or two or more types.

Cationic polymers having a quaternary ammonium salt group are generally highly water-soluble due to the quaternary ammonium salt group, but depending on the composition and the ratio of the monomer containing no quaternary ammonium salt group to be copolymerized, they are sufficiently water-soluble. Although it may not dissolve in water, it can be used in the present invention as long as it can be dissolved in a mixed solvent of a water-miscible organic solvent and water.

Here, the water-miscible organic solvent means alcohols such as methanol, ethanol, isopropanol and n-propanol, glycols such as ethylene glycol, diethylene glycol and glycerin, esters such as ethyl acetate and propyl acetate, acetone, It refers to an organic solvent that is usually soluble in water by 10% or more, such as ketones such as methyl ethyl ketone and amides such as N, N-dimethylformamide. In this case, the amount of the organic solvent used is preferably less than the amount of water used.

Various additives other than those described above can be added to the ink absorbing layer of the recording medium according to the present invention and other layers provided as necessary.

Examples of the above-mentioned additives include polystyrene, polyacrylic acid esters, polymethacrylic acid esters, polyacrylamides, polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, their copolymers, and urea. Organic latex fine particles such as resin or melamine resin, various cationic or nonionic surfactants, JP-A-57-74193 and 57-
UV absorbers described in JP-A Nos. 87988 and 62-261476, JP-A-57-74192 and 57-879.
89, 60-72785, 61-146591.
And anti-fading agents described in JP-A-1-95091 and JP-A-3-13376, and JP-A-59-429993.
No. 59-52689, No. 62-280069,
Fluorescent whitening agents, pH adjusting agents such as sulfuric acid, phosphoric acid, citric acid, sodium hydroxide, potassium hydroxide, potassium carbonate, etc., and defoaming agents described in JP-A-61-242871 and JP-A-4-219266. Various known additives such as antiseptics, thickeners, antistatic agents and matting agents can also be incorporated.

In the recording medium according to the present invention, various hydrophilic layers, such as a porous layer and an undercoat layer, which are appropriately provided as necessary, are coated on the support by appropriately selecting from known methods. be able to. A preferred method is obtained by applying a coating solution forming each layer on a support and drying. In this case, two or more layers can be applied simultaneously,
In particular, a multi-layer simultaneous coating method in which all hydrophilic binder layers are formed by one coating is preferable.

The coating method is, for example, a roll coating method, a rod bar coating method, an air knife coating method, a spray coating method, a curtain coating method or an extrusion coating method using a hopper described in US Pat. No. 2,681,294. Is preferably used.

Next, the pigment ink according to the present invention will be described. The present invention is characterized in that at least one color of pigment ink contains pigment particles having an absolute value of zeta potential of 30 to 100 mV, and preferably contains pigment particles having an absolute value of zeta potential of 35 to 80 mV. It is to be. If the absolute value of the zeta potential is less than 30 mV,
After printing, agglomeration of pigment particles occurs on the recording medium to reduce the glossiness, and conversely, when it is higher than 100 mV, the printed image becomes glaring and it becomes impossible to obtain a desirable texture.

In the present invention, the method for imparting the zeta potential defined above to the pigment particles is not particularly limited, but, for example, the kind and addition amount of the surfactant used at the time of dispersing the pigment, addition of an additive having a charge are added. A desired zeta potential can be obtained by appropriately selecting the above. The zeta potential according to the present invention can be measured using, for example, ELS-800 (manufactured by Otsuka Electronics Co., Ltd.).

Examples of the pigment dispersant that can be used in the present invention include higher fatty acid salts, alkyl sulfates, alkyl ester sulfates, alkyl sulfonates, sulfosuccinates, naphthalene sulfonates, alkyl phosphates, Polyoxyalkylene alkyl ether phosphate,
Activator such as polyoxyalkylene alkyl phenyl ether, polyoxyethylene polyoxypropylene glycol, glycerin ester, sorbitan ester, polyoxyethylene fatty acid amide, amine oxide, or styrene, styrene derivative, vinylnaphthalene derivative, acrylic acid, acrylic acid derivative And block copolymers, random copolymers and salts thereof composed of two or more kinds of monomers selected from maleic acid, maleic acid derivatives, itaconic acid, itaconic acid derivatives, fumaric acid and fumaric acid derivatives. You can

As the dispersing means that can be used in the present invention, for example, a ball mill, a sand mill, an attritor, a roll mill, an agitator, a Henschel mixer,
Various dispersers such as a colloid mill, an ultrasonic homogenizer, a pearl mill, a wet jet mill and a paint shaker can be used. Further, it is also preferable to use a centrifugal separator and a filter for the purpose of removing coarse particles of the pigment dispersion.

The invention according to claim 2 is characterized in that the maximum particle diameter (D99) of the pigment particles is less than 300 nm, and in the invention according to claim 3, the average particle diameter (D50) of the pigment particles. Is 35 to 120 nm.

The D99 value and the D50 value are distribution functions dG = F
In the integral curve of (D) × dD, particle diameters equal to 0.99 (99% by number) and 0.5 (50% by number) of the total number of pigment particles are shown. In addition, G represents the number of pigment particles, and D represents the particle diameter of the pigment particles.

The above relational expression will be further described with reference to the drawings.
FIG. 1 shows a pigment dispersion in a coordinate system in which the particle size (D) of the pigment particles is plotted on the abscissa and the particle number function (G) of each pigment particle of a given dimension is plotted on the ordinate. The curve of the particle size distribution function is shown as a solid line. further,
In the same coordinate system, the dashed curve shows the integral of the distribution function with the points of the 50% and 99% particle number functions and the relevant points of particle size D50 and D99 represented by a cross.

The particle size of the pigment dispersion can be measured by a commercially available particle size measuring device using a light scattering method, an electrophoresis method, a laser Doppler method or the like. In addition, a particle image is photographed with a transmission electron microscope for at least 100 particles, and the image is statistically processed using image analysis software such as Image-Pro (manufactured by Media Cybernetics), or for analysis. By an ultracentrifuge (eg W. Maechtle, Makromol. Che
m. 185 (1984), pp. 1025-1039).

The invention according to claim 2 is characterized in that the maximum particle diameter (D99) of the pigment particles is less than 300 nm, preferably 50 to 290 nm, more preferably 70 to 250 nm. When the maximum particle diameter (D99) of the pigment particles is 300 nm or more, the glossiness is deteriorated due to the coarse pigment particles, which is not preferable.

The invention according to claim 3 is characterized in that the average particle diameter (D50) of the pigment particles is 35 to 120 nm, preferably 50 to 90 nm.
When the average particle diameter (D50) of the pigment particles exceeds 120 nm, the glossiness is deteriorated due to the coarse pigment particles, which is not preferable, and when the average particle diameter (D50) is less than 35 nm, the pigment particles are filled in the voids of the recording medium. However, the desired print density cannot be obtained.

In the present invention, the method for controlling the average particle diameter (D50) of the pigment particles to a specified range is not particularly limited, but, for example, as described above, the dispersing agent, dispersing means, and dispersing agent at the time of dispersing the pigment particles. By selecting conditions etc. appropriately,
It is possible to obtain a pigment dispersion having a desired average particle diameter.

The method for controlling the maximum particle diameter (D99) of the pigment particles to a specified range is not particularly limited, but, for example, as described above, the dispersant at the time of dispersing the pigment particles, the dispersing means,
This can be achieved by a method of appropriately selecting dispersion conditions and the like, and by combining coarse particle separation means such as centrifugation or filter filtration after dispersion.

In the invention according to claim 4, as the pigment ink, the ink absorbance ε at 400 to 700 nm represented by the above formula (1) is 10,000 or more and 50,000 or less for the yellow ink, magenta ink or cyan ink, and black. The feature is that a pigment having an ink content of 50,000 or more and 150,000 or less is used.

The ink absorbance ε in the present invention is a value defined by the above formula (1), and specifically, the absorption wavelength 4
The absorbance per 5 nm at 00 to 700 nm is 60
It is the value obtained by point integration.

One of the characteristics of the yellow ink, magenta ink or cyan ink is 10,000 or more and 50,000 or less, preferably 12,000 or more and 45,000 or less, and black ink. Is characterized by 50,000 or more and 150,000 or less, preferably 70,000 or more and 140,000 or less.

In the present invention, the ink absorbance ε can be measured by, for example, diluting the ink with an appropriate solvent and then using a commercially available spectrophotometer, for example, Hitachi Model 330 self-recording spectrophotometer, U-3210. Type self-recording spectrophotometer, U-3
410, etc., in the measurement wavelength range of 400 to 700 nm,
It is possible to obtain the ink absorbance ε by measuring the absorbance every 5 nm, obtaining the integrated absorbance according to the above formula (1), and multiplying the absorbance by the dilution factor.

The pigment that can be preferably used in the present invention is not particularly limited as long as it is a pigment having the ink absorbance ε range defined above.

In the present invention, conventionally known organic and inorganic pigments can be used. For example, azo pigments such as azo lake, insoluble azo pigment, condensed azo pigment, chelate azo pigment, phthalocyanine pigment, perylene and perylene pigment,
Anthraquinone pigments, quinacridone pigments, dioxazine pigments, thioindigo pigments, isoindolinone pigments, polycyclic pigments such as quinophthaloni pigments, basic dye type lakes, dye lakes such as acid dye type lakes, nitro pigments,
Examples include nitroso pigments, aniline black, organic pigments such as daylight fluorescent pigments, and inorganic pigments such as carbon black.

Specific organic pigments are exemplified below. Pigments for magenta or red include C.I. I. Pigment Red 2, C.I. I. Pigment Red 3, C.I. I. Pigment Red 5, C.I. I. Pigment Red 6, C.I.
I. Pigment Red 7, C.I. I. Pigment Red 1
5, C.I. I. Pigment Red 16, C.I. I. Pigment Red 48: 1, C.I. I. Pigment Red 53:
1, C.I. I. Pigment Red 57: 1, C.I. I. Pigment Red 122, C.I. I. Pigment Red 12
3, C.I. I. Pigment Red 139, C.I. I. Pigment Red 144, C.I. I. Pigment Red 149,
C. I. Pigment Red 166, C.I. I. Pigment Red 177, C.I. I. Pigment Red 178, C.I.
I. Pigment Red 222 and the like.

Pigments for orange or yellow include C.I. I. Pigment Orange 31, C.I. I. Pigment Orange 43, C.I. I. Pigment Yellow 12,
C. I. Pigment Yellow 13, C.I. I. Pigment Yellow 14, C.I. I. Pigment Yellow 15, C.I.
I. Pigment Yellow 17, C.I. I. Pigment Yellow 74, C.I. I. Pigment Yellow 93, C.I. I.
Pigment Yellow 94, C.I. I. Pigment Yellow 128, C.I. I. Pigment Yellow 138 and the like.

As the pigment for green or cyan,
C. I. Pigment Blue 15, C.I. I. Pigment Blue 15: 2, C.I. I. Pigment Blue 15: 3,
C. I. Pigment Blue 16, C.I. I. Pigment Blue 60, C.I. I. Pigment Green 7 and the like.

The pigment ink used in the present invention may contain the above-mentioned pigment dispersant, if necessary. As the method for dispersing the pigment, the above-mentioned various methods can be appropriately selected and used.

Next, with respect to the pigment ink according to the present invention, constituent factors other than those described above will be described below.

The ink according to the present invention may contain latex. The latex in the present invention refers to polymer particles in a dispersed state in a medium. Examples of the type of polymer include styrene-butadiene copolymer, polystyrene, acrylonitrile-butadiene copolymer, acrylic ester copolymer, polyurethane, silicon-acrylic copolymer, and acrylic modified fluororesin. However, acrylic acid ester, polyurethane and silicone-acrylic copolymer are preferred.

As the emulsifier used in the production of latex, a low molecular weight surfactant is generally used, but a high molecular weight surfactant (for example, a type in which a solubilizing group is graft-bonded to a polymer or There is a type of block polymer in which a portion having a solubilizing group and an insoluble portion are linked) can be used as an emulsifier. Also,
There are also latices dispersed without emulsifiers by directly attaching the solubilizing groups to the central polymer of the latex. The latex using a high molecular weight surfactant as the emulsifier and the latex not using the emulsifier as described above are called soap-free latex.
As the latex used in the present invention, the type of emulsifier,
Regardless of the form, it is more preferable to use soap-free latex, which is excellent in ink storage stability.

Recently, in addition to the latex in which the central polymer is uniform, there is also a core / shell type latex in which the composition is different between the central part and the outer edge part of the polymer particles, and it is also preferable to use this type of latex. it can.

The average particle size of the latex in the present invention is 1
The thickness is preferably 50 nm or less, more preferably 50 nm or less.

The average particle size of the latex can be easily measured by using a commercially available measuring device using a light scattering method or a laser Doppler method.

The solid content of the latex in the present invention is preferably 0.1% by mass or more and 10% by mass or less, and particularly preferably 0.3% by mass or more and 5% by mass or less, based on the total mass of the ink. . If the added amount is less than 0.1% by mass, it is difficult to exert a sufficient effect on water resistance, and if the added amount exceeds 10% by mass, the ink viscosity and the pigment dispersed particle size tend to increase with the passage of time. There are often problems in terms.

In the present invention, the pigment ink preferably contains 0.3 to 10% by mass of a water-soluble polymer compound having a weight average molecular weight of 3,000 to 30,000.

The water-soluble polymer referred to in the present invention is, for example,
Natural water-soluble polymers such as corn and wheat starches, carboxymethyl cellulose, methyl cellulose, cellulose derivatives such as hydroxyethyl cellulose, sodium alginate, guar gum, tamarind gum, locust bean gum, polysaccharides such as gum arabic, gelatin, and casein. , Protein substances such as keratin, and the like.

Further, synthetic polymers are mentioned as preferred examples of the water-soluble polymer, and polyvinyl alcohols, polyvinyl pyrrolidones, polyacrylic acid, acrylic acid-acrylonitrile copolymers, potassium acrylate-acrylonitrile copolymers. Acrylic resins such as vinyl acetate-acrylic acid ester copolymers or acrylic acid-acrylic acid ester copolymers, styrene-acrylic acid copolymers, styrene-methacrylic acid copolymers, styrene-methacrylic acid-acrylic acid Ester copolymer, styrene-
Styrene acrylic acid resin such as α-methylstyrene-acrylic acid copolymer or styrene-α-methylstyrene-acrylic acid-acrylic acid ester copolymer, styrene-sodium styrenesulfonate copolymer, styrene-2-hydroxy Ethyl acrylate copolymer, styrene-2-hydroxyethyl acrylate-potassium styrenesulfonate copolymer, styrene-maleic acid copolymer, styrene-maleic anhydride copolymer, vinylnaphthalene-acrylic acid copolymer, vinylnaphthalene -Maleic acid copolymer, vinyl acetate-maleic acid ester copolymer, vinyl acetate-crotonic acid copolymer, vinyl acetate-
Examples thereof include vinyl acetate-based copolymers such as acrylic acid copolymers and salts thereof.

The water-soluble polymer has a molecular weight of 3,000 to 3
It is preferably 50,000, more preferably 3,
000 to 20,000, particularly preferably 3,000
It is 0 to 10,000. When it is less than 3,000, the effect of suppressing the growth and aggregation of pigment particles is reduced, and the effect of improving the gloss is reduced, and when it exceeds 30,000, the viscosity is increased, the dissolution is poor, the storage stability of the ink is stable, and the ejection stability is stable. This is not preferable because it tends to result in deterioration of the property.

The addition amount of the water-soluble polymer is characterized by being 0.3 to 10% by mass with respect to the mass of the pigment ink, but preferably 0.6 to 4.0% by mass. 0.3%
If it is less than 10% by weight, the effect of suppressing the growth and aggregation of pigment particles is reduced, and the effect of improving the glossiness is reduced, and if it exceeds 10% by mass, viscosity increase, poor dissolution, ink storage stability, and ejection stability are reduced. It is not preferable because it tends to result in damage.

The water-soluble polymer according to the present invention may be added either when the pigment is dispersed or after the dispersion. Further, in the pigment ink according to the present invention, two or more kinds of the above water-soluble polymers may be used.

In the present invention, an electric conductivity modifier may be used, and examples thereof include inorganic salts such as potassium chloride, ammonium chloride, sodium sulfate, sodium nitrate and sodium chloride, and aqueous amines such as triethanolamine. .

In the ink of the present invention and the constituent layers provided as necessary, depending on the purpose of improving ejection stability, compatibility with print heads and ink cartridges, storage stability, image storability, and other performances, Further viscosity modifier,
A specific resistance adjusting agent, a film-forming agent, an ultraviolet absorber, an antioxidant, an anti-fading agent, a rust preventive, an antiseptic agent and the like can be added, for example, polystyrene, polyacrylic acid esters, polymethacrylic acid esters. , Polyacrylamides, polyethylene, polypropylene, polyvinyl chloride,
Polyvinylidene chloride or a copolymer thereof, organic latex particles such as urea resin or melamine resin, liquid paraffin, dioctyl phthalate, tricresyl phosphate, oil droplet particles such as silicone oil, various cationic or nonionic surfactants. JP-A-57-741
No. 93, No. 57-87988, and No. 62-2.
UV absorbers described in JP-A-61476, JP-A-57-
74192, 57-87989, and 60-7.
No. 2,785, No. 61-146591, No. 1-95091, No. 3-13376, and the like, anti-fading agents, No. 59-42493, No. 59-52689. , Ibid.
No. 9, JP-A No. 61-242871, and Japanese Patent Laid-Open No. Hei.
Fluorescent whitening agents described in JP-A-219266,
Contains various known additives such as pH adjusting agents such as sulfuric acid, phosphoric acid, citric acid, sodium hydroxide, potassium hydroxide, potassium carbonate, defoaming agents, preservatives, thickeners, antistatic agents, matting agents, etc. You can also let it.

The ink jet head which can be used in the ink jet recording method of the present invention may be either an on-demand type or a continuous type. In addition, as a discharge method, an electro-mechanical conversion method (for example, a single cavity type, a double cavity type, a bender type, a piston type, a shear mode type, a shared wall type, etc.), an electric-heat conversion method (for example, a thermal type Inkjet type,
Bubble jet (registered trademark) type, etc., electrostatic attraction method (for example, electric field control type, slit jet type, etc.), discharge method (for example, spark jet type, etc.) and the like can be mentioned as specific examples. Either ejection method may be used.

[0142]

EXAMPLES Examples of the present invention will be described below.
The invention is not limited to these examples. In addition,
In the examples, "%" represents mass% unless otherwise specified.

<< Preparation of Recording Medium 1 >> [Preparation of Support 1] Moisture content of 6.5% by mass, basis weight of 170
Low density polyethylene with a density of 0.92 was applied to the backside of g / m ² photographic base paper with a thickness of 20 μm by the extrusion coating method, and after corona discharge, styrene-acryl with Tg of about 80 ° C. About 0.4 g of acid ester latex binder, 0.1 g of antistatic agent (cationic polymer)
And a back layer containing 0.1 g of silica of about 2 μm as a matting agent was applied.

Next, low density polyethylene containing 5.5% by mass of anatase type titanium oxide and having a density of 0.92 was applied on the front side (ink absorption layer coated surface side) by a melt extrusion coating method to a thickness of 14 μm. Immediately after the melt-extrusion coating, both surfaces were coated with polyethylene, and the surface of the polyethylene on the front side was subjected to a mold treatment while cooling on the surface on which the ink absorbing layer was coated, using a mirror cooling roll. Then
After subjecting this surface to corona discharge, a gelatin subbing layer containing a crosslinking agent was applied at 0.03 g / m ² to prepare a support 1.

[Preparation of Dispersions] (Preparation of Titanium Oxide Dispersion-1) The average particle size is about 0.25.
20 μm of titanium oxide (μm: W-10, manufactured by Ishihara Sangyo), 150 g of sodium tripolyphosphate with pH = 7.5,
Polyvinyl alcohol (Kuraray Co., Ltd .: PVA23
5) 500 g, cationic polymer (exemplary compound P-
9) 150 g and 10 g of Sannobuco Ltd. antifoaming agent SN381 was added to 90 L of an aqueous solution and dispersed by a high-pressure homogenizer (manufactured by Sanwa Kogyo Co., Ltd.). Liquid-1
Was prepared.

(Preparation of Silica Dispersion-1) 125 kg of vapor-phase process silica (A300 manufactured by Nippon Aerosil Co., Ltd.) having an average primary particle size of about 0.007 μm was jetted by Mitamura Riken Kogyo Co., Ltd. Using a stream inductor mixer TDS, after suction-dispersing in 600 L of pure water adjusted to pH = 3.0 with nitric acid at room temperature, the total amount is finished to 660 L with pure water to prepare silica dispersion liquid-1. did.

(Preparation of Silica Dispersion Liquid-2) An aqueous solution (pH = 2.3) containing 1.29 kg of a cationic polymer (exemplary compound P-9), 4.2 L of ethanol and 1.5 L of n-propanol. ) In 15 L, the above silica dispersion liquid-
66.0 L of 1 was added with stirring, and then 7.0 L of an aqueous solution containing 260 g of boric acid and 230 g of borax.
Was added, and 1 g of the above defoaming agent SN381 was added.

This mixed solution was dispersed with a high pressure homogenizer manufactured by Sanwa Kogyo Co., Ltd., and the total amount was adjusted to 90 L with pure water to prepare a silica dispersion liquid-2.

(Preparation of Optical Brightening Agent Dispersion-1) Oil-soluble optical brightening agent UVITEX-OB manufactured by Ciba-Geigy Co., Ltd.
Was dissolved in 9000 g of diisodecyl phthalate and 12 L of ethyl acetate by heating, and 3500 g of acid-treated gelatin and a cationic polymer (exemplified compound P-
9), mixed and added to 65 L of an aqueous solution containing 6,000 ml of saponin (50% aqueous solution), emulsified and dispersed with a high pressure homogenizer manufactured by Sanwa Kogyo Co., Ltd., and after removing ethyl acetate under reduced pressure, the total amount is 100 L. Thus, an optical brightener dispersion liquid-1 was prepared.

(Preparation of Matting Agent Dispersion-1) Methacrylic acid ester type monodisperse matting agent MX manufactured by Soken Kagaku Co., Ltd.
156 g of -1500 (average particle size 15 μm) was added to the P
VA235 was added to 7 L of pure water containing 3 g and dispersed with a high-speed homogenizer to finish the total amount to 7.8 L to prepare Matting Agent Dispersion-1.

[Preparation of Ink Absorbing Layer Coating Liquid] First, second and third ink absorbing layer coating liquids were prepared by the following procedure.

(Preparation of coating liquid for first layer) While stirring 560 ml of the above silica dispersion liquid-2 at 40 ° C., the following additives were sequentially mixed to prepare a coating liquid for first layer.

[0153]   Polyvinyl alcohol (Kuraray Industry Co., Ltd .: PVA203)     10% aqueous solution of 0.6 ml   Polyvinyl alcohol (Kuraray Industries Co., Ltd .: PVA235)     260 ml of 5% aqueous solution   Optical brightener dispersion-1 22 ml   Titanium oxide dispersion-1 40 ml   Daiichi Kogyo Co., Ltd .: Latex emulsion-AE-803 24 ml   The total volume was adjusted to 1000 ml with pure water.

(Preparation of Second Layer Coating Liquid) While stirring 650 ml of the above silica dispersion liquid-2 at 40 ° C., the following additives were sequentially mixed to prepare a second layer coating liquid.

[0155]   Polyvinyl alcohol (Kuraray Industry Co., Ltd .: PVA203)     10% aqueous solution of 0.6 ml   Polyvinyl alcohol (Kuraray Industries Co., Ltd .: PVA235)     270ml of 5% aqueous solution   Optical brightener dispersion-1 30 ml   The total volume was adjusted to 1000 ml with pure water.

(Preparation of Coating Solution for Third Layer) While stirring 650 ml of the above silica dispersion liquid-2 at 40 ° C., the following additives were sequentially mixed to prepare a coating solution for third layer.

[0157]   Polyvinyl alcohol (Kuraray Industry Co., Ltd .: PVA203)     10% aqueous solution of 0.6 ml   Polyvinyl alcohol (Kuraray Industries Co., Ltd .: PVA235)     270ml of 5% aqueous solution   Silicon dispersion (manufactured by Toray Dow Corning Silicone Co., Ltd .:     BY-22-839) 3.5 ml   Saponin 50% aqueous solution 4 ml   Matting agent dispersion-1 10 ml   The total volume was adjusted to 1000 ml with pure water.

Each coating solution prepared as described above was filtered with the following filter. First layer, second layer: TCP10 manufactured by Toyo Roshi Kaisha, Ltd. filtered in two steps Third layer: TCP30 manufactured by Toyo Roshi Kaisha, Ltd. filtered in two steps [Application of ink absorbing layer] Each application prepared as described above The liquid was applied with a three-layer slide hopper at 40 ° C., immediately after the application, cooled in a cooling zone kept at 8 ° C. for 20 seconds, and then blown at 20 to 30 ° C. for 60 seconds and at 45 ° C. for 60 seconds. After drying for 60 seconds with a 50 ° C. air for 60 seconds, 23
Recording medium 1 was prepared by controlling the humidity at 40 to 60% relative humidity.

[Surface Characteristics of Recording Medium 1] (Measurement of Centerline Surface Roughness of Surface) The centerline surface roughness of the surface of the recording medium 1 produced above was measured by the following method. The center line average roughness Ra (μm) was measured using a non-contact three-dimensional surface analyzer (RST / PLUS manufactured by WYKO). Ra is defined by JIS surface roughness (B060
Followed 1). In the measurement, each sample of 30 cm × 30 cm was divided into 100 on a grid at intervals of 3 cm, the center of each square area was measured, and the average value and standard deviation were obtained from 100 measurements. Centerline average roughness (R
In a), a portion having a measurement length of 2.5 mm is extracted from the obtained roughness curve in the direction of its center line, and the cutoff value is set to 0.
When the center line of the extracted portion is set to 8 mm, the longitudinal magnification direction is represented by Y axis, and the roughness curve is represented by Y = f (X), the value obtained by the formula (Equation 5) is expressed in micrometers (μm). ).

[0160]

[Equation 5]

The center line surface roughness of the surface of the recording medium 1 measured by the above method was 0.4 μm.

(Measurement of 60-degree specular glossiness) The surface of the recording medium 1 prepared above was measured for 60-degree specular glossiness in accordance with JIS-Z-8741, and as a result, the 60-degree specular glossiness was 35%. It was A gonio gloss meter (VGS-1001DP) manufactured by Nippon Denshoku Industries Co., Ltd. was used for the measurement.

(Measurement of Bristow Permeation Rate on Surface) The Bristow permeation rate was measured according to J. TAPPI paper pulp test method
No. The measurement was carried out according to the liquid absorption test method (Bristow method) of paper and paperboard of 51-87.

40 μl of the test solution was sampled with a microsyringe and p (nozzle gap) = 1 mm, w (nozzle width) = 1.75 cm from the nozzle port, ν (paper moving speed) = 20 mm / sec. It is permeated and moved onto the recording medium 1 rotating at a speed. The transition length at this time is L (cm)
At this time, the ink permeation amount V was obtained by the above equation 3. Further, the transition time t at that time is t = p / υ = 1.0 / υ (se
Determined in c).

As the test solution, an aqueous solution prepared by adding 0.1% of the dye Direct Blue 199 to ion-exchanged water was used.

The amount of transfer obtained from the above Lucas-Washburn relational expression (Equation 3) and Equation 4 which is known as a theoretical equation when the penetration of the test solution proceeds into the capillary of the paper by permeation wetness. by using the V _0, the penetration rate _{d (V-V 0) /} d
√t (ml / m ² · sec ^1/2 ) was calculated. The Bristow penetration rate of the recording medium 1 calculated as described above is 6
It was 1 ml / m ² · sec ^1/2 .

<< Preparation of Recording Medium 2 >> A recording medium 2 was prepared in the same manner as in the preparation of the recording medium 1 except that the following support 2 was used instead of the support 1.

(Preparation of Support 2) In the preparation of Support 1, immediately after melt extrusion of polyethylene on the front side, a mirror-like cooling roll was replaced with a cooling roll having irregular irregularities on the surface, A support 2 was produced in the same manner except that the polyethylene surface on the front side was subjected to a molding treatment while being cooled.

The surface characteristics of the recording medium 2 produced as described above were measured by the same method as used for the recording medium 1, and as a result, the center line surface roughness of the surface was 4.5 μm, and the surface had a 60 ° specular gloss. 7%, Bristow penetration rate is 61 ml / m
It was ² sec ^1/2 .

<< Preparation of Recording Medium 3 >> In the preparation of the recording medium 1, the following support 3 was used instead of the support 1.
In addition, the mixing ratio of the binder (polyvinyl alcohol) and the inorganic fine particles (silica particles) of the first, second and third layers of the ink absorbing layer is appropriately changed so that the Bristow permeation rate is 1.
A recording medium 3 having a volume of 6 ml / m ² · sec ^1/2 was prepared.

(Preparation of Support 3) Support 2 was prepared in the same manner as in preparation of Support 2 except that the number of irregularly-shaped irregularities on the surface of the cooling roll used in the embossing treatment on the front side was changed to 0.6 times. Body 3 was produced.

The surface characteristics of the recording medium 3 produced as described above were measured by the same method as used for the recording medium 1. As a result, the center line surface roughness of the surface was 2.8 μm and the surface had a 60 ° specular gloss. The degree was 18%.

<< Preparation of Recording Medium 4 >> In the preparation of the recording medium 3 described above, the mixing ratio of the binder (polyvinyl alcohol) and the inorganic fine particles (silica particles) of the first, second and third layers of the ink absorbing layer. Recording medium 4 having a Bristow permeation rate of 120 ml / m ² · sec ^1/2
Was produced.

<< Preparation of Recording Medium 5 >> In the preparation of the above recording medium 3, the mixing ratio of the binder (polyvinyl alcohol) and the inorganic fine particles (silica particles) of the first, second and third layers of the ink absorbing layer. Was appropriately changed to prepare a recording medium 5 having a Bristow permeation rate of 61 ml / m ² · sec ^1/2 .

<< Preparation of Recording Mediums 6-9 >> Recording Medium 5
In the preparation of, the center line surface roughness of the surface, the 60-degree specular gloss of the surface, and the Bristow permeation rate were set to the characteristic values shown in Table 1, so that the number of irregular shape irregularities on the surface of the cooling roll on the surface of the support was Recording media 6 to 9 were prepared by appropriately changing the ratio of the binder and the inorganic fine particles in the supports 4 and 5 and the ink absorbing layer in which the above was changed.

<Preparation of Recording Medium 10> The recording medium 5 was prepared in the same manner as in the preparation of the recording medium 5, except that the cationic polymer (P-9) in each dispersion used for forming the ink absorbing layer was removed. 10 was produced.

Table 1 shows characteristic values of the respective recording media manufactured as described above.

[0178]

[Table 1]

<< Preparation of Pigment Ink Set 1 >> [Preparation of Pigment Dispersion] (Preparation of Yellow Pigment Dispersion 1) C.I. I. Pigment Yellow 128 20% by mass Styrene-acrylic acid copolymer (molecular weight 10,000, acid value 120) 12% by mass Diethylene glycol 15% by mass Ion-exchanged water 53% by mass Mixing the above additives, 0.3 mm zirconia beads Was dispersed using a horizontal bead mill (System Zetamini manufactured by Ashizawa Co., Ltd.) filled with 60% by volume, and then undispersed coarse particles were removed by centrifugation to obtain Yellow Pigment Dispersion 1
Got

(Preparation of Magenta Pigment Dispersion 1) C.I. I. Pigment Red 122 25% by mass John Cryl 61 (acrylic-styrene resin, manufactured by Johnson Co.) Solid content 18% by mass Diethylene glycol 15% by mass Ion-exchanged water 42% by mass Mixing the above additives, 0.3 mm zirconia beads Was dispersed using a horizontal bead mill (System Zetamini manufactured by Ashizawa Co., Ltd.) filled with 60% by volume, and then undispersed coarse particles were removed by centrifugation to obtain a magenta pigment dispersion 1
Got

(Preparation of Cyan Pigment Dispersion 1) C.I. I. Pigment Blue 15: 3 25% by mass John Cryl 61 (acrylic-styrene resin, manufactured by Johnson Co.) 15% by mass as solid content Glycerin 10% by mass Ion-exchanged water 50% by mass Add each of the above additives to obtain 0.3 mm Cyan pigment dispersion 1 was obtained by dispersing using a horizontal bead mill (System Zetamini manufactured by Ashizawa Co., Ltd.) filled with zirconia beads at a volume ratio of 60% and removing undispersed coarse particles by centrifugation.

(Preparation of Black Pigment Dispersion 1) Carbon black 20% by mass Styrene-acrylic acid copolymer (molecular weight 7,000, acid value 150) 10% by mass Glycerin 10% by mass Ion-exchanged water 60% by mass Each of the above additions The agents were mixed and dispersed using a horizontal bead mill (System Zetamini manufactured by Ashizawa Co., Ltd.) filled with 0.3 mm zirconia beads at a volume ratio of 60%, and then undispersed coarse particles were removed by centrifugation to disperse the black pigment. Body 1
Got

[Preparation of Ink] (Preparation of Yellow Ink 1) Yellow Pigment Dispersion 1 15% by mass Ethylene glycol 20% by mass Diethylene glycol 10% by mass Surfactant (Surfynol 465, Nissin Chemical Industry Co., Ltd.) 0.1% by mass Ion-exchanged water 54.9% by mass After mixing the above compositions and thoroughly stirring, the pore size 1
Yellow ink 1 was prepared by passing through a μm Millipore filter filter twice. The absorbance ε of the obtained ink was measured by the above-mentioned method and was 13,000.

(Preparation of Magenta Ink 1) Magenta Pigment Dispersion 1 15% by mass Ethylene glycol 20% by mass Diethylene glycol 10% by mass Surfactant (Surfynol 465 Nisshin Chemical Industry Co., Ltd.) 0.1% by mass ion-exchanged water 54. After mixing 9% by mass or more of each composition and thoroughly stirring,
Magenta ink 1 was prepared by passing it twice through a Millipore filter of μm. Absorbance ε of the obtained ink
Was 15,000.

(Preparation of Cyan Ink 1) Cyan Pigment Dispersion 1 10% by mass Ethylene glycol 20% by mass Diethylene glycol 10% by mass Surfactant (Surfynol 465 Nisshin Chemical Industry Co., Ltd.) 0.1% by mass ion-exchanged water 59. After mixing 9% by mass or more of each composition and thoroughly stirring,
Cyan ink 1 was prepared by passing twice through a μm Millipore filter filter. The absorbance ε of the obtained ink is
It was 26,000.

(Preparation of Black Ink 1) Black Pigment Dispersion 1 10% by mass Ethylene glycol 20% by mass Diethylene glycol 10% by mass Surfactant (Surfynol 465, Nisshin Chemical Industry Co., Ltd.) 0.1% by mass ion-exchanged water 59. After mixing 9% by mass or more of each composition and thoroughly stirring,
Black ink 1 was prepared by passing through a μm Millipore filter filter twice. Absorbance ε of the obtained ink
Was 98,000.

[Zeta potential of each ink, D99, D50
(Measurement of Zeta Potential) Each of the inks prepared above was diluted with pure water to a pigment particle concentration of 0.01%, and then ELS-800 (manufactured by Otsuka Electronics Co., Ltd.) was used. Zeta measurement was performed.

The zeta potential of each ink of the pigment ink set 1 measured by the above method is as follows.

Yellow ink 1-67 mV Magenta ink 1-63 mV Cyan ink 1-66 mV Black ink 1-61 mV (measurement of D99, D50) Each pigment ink was diluted to 0.01% pigment concentration, and the pigment ink droplets were made into polyethylene. After being dropped on a terephthalate film and dried, a sample was prepared using a JFD-7000 type (manufactured by JEOL Ltd.) as a vacuum vapor deposition device, and as a FE-SEM, S-5000.
Using an H type (manufactured by Hitachi, Ltd.), the number of fields of view was selected and observed at an acceleration voltage of 2.0 kV so that the number of pigment particles was 1000 or more. The images were digitized and transferred to a connected filing device (VIDEOBANK) and stored in an MO disc. Then, if particles overlap or come into contact with a LUZEX-III type (manufactured by Nireco) image processing apparatus, the particles are extracted manually, and the particle size of each particle is measured to obtain an average value. It was

Based on the particle size measurement data of 1,000 particles measured by the above method, the abscissa represents the particle size (D) and the ordinate represents the particle number function (G). 1 and the integral curve 2 of the distribution function are created, and from the integral curve 2, the particle size points D50 corresponding to 50% by number and 99% by number in the particle number function.
And D99 were measured.

D50 and D99 of the pigment ink set 1 obtained by the above method are as follows.

Yellow Ink 1 D50: 74 nm D99: 229 nm Magenta Ink 1 D50: 71 nm D99: 230 nm Cyan Ink 1 D50: 77 nm D99: 235 nm Black Ink 1 D50: 79 nm D99: 241 nm << Preparation of Pigment Ink Sets 2-9 >> In the preparation of the pigment ink set 1, the kind and addition amount of the surfactant at the time of preparation of each pigment dispersion 1, the condition or presence of centrifugal separation, the dispersion strength, the pore size of the filter at the time of preparation of each pigment ink, and the number of filtrations Pigment ink sets 2 to 9 having the characteristics of zeta potential, D50 and D99 shown in Table 2 were prepared by appropriately adjusting and combining.

<< Preparation of Pigment Ink Set 10 >> In the preparation of the above pigment ink set 1, the pigment used in the preparation of each pigment dispersion 1 was changed in the same manner as described below except that the pigments and the contents thereof were changed appropriately. A pigment ink set 10 was prepared.

Yellow pigment: C.I. I. Pigment Yellow 128 (ε: 9,500) Magenta Pigment: C.I. I. Pigment Red 48 (ε:
8,700) Cyan pigment: C.I. I. Pigment Blue 16 (ε: 9,
000) Black pigment: carbon black (ε: 43,000) << Preparation of pigment ink set 11 >> In the preparation of the pigment ink set 1, the pigments used at the time of preparation of the respective pigment dispersions 1 are the pigments described below and the inclusion thereof. A pigment ink set 11 was prepared in the same manner except that the amount was changed appropriately. The value in parentheses is the ink absorbance.

Yellow pigment: C.I. I. Pigment Yellow 74 (ε: 55,000) Magenta Pigment: C.I. I. Pigment Red 144 (ε:
53,000) Cyan pigment: C.I. I. Pigment Blue 60 (ε: 6
50,000) Black pigment: Carbon black (ε: 165,00)
0) Table 2 shows the zeta potentials D50 and D99 of the inks of the ink sets 1 to 11 prepared as described above.

[0196]

[Table 2]

<Image printing> Nozzle hole diameter of 20 μm was obtained by combining the recording medium shown in Table 3 and the pigment ink set.
m, driving frequency 12 kHz, 12 nozzles per color
8. A piezo type head having a nozzle density of 180 dpi between the same colors is mounted, and an on-demand type ink jet printer having a maximum recording density of 720 × 720 dpi is used to set a reflection density of 1.0 and a maximum density on each recording medium. Printed images 1 to 20 of the given monochrome image patterns were output.
The term "dpi" used in the present invention means 2.54 cm (1 in
The number of dots per ch).

<< Evaluation of Characteristic of Printed Image >> The following characteristic evaluations were performed on the printed image prepared as described above.

(Evaluation of Gloss Difference) With respect to each printed image, the gloss difference between the printed portion and the non-printed portion was visually observed according to the following criteria to evaluate the gloss difference.

⊚: The ink image of all colors has a marked glossiness in the printed area, and the difference from the non-printed area is not noticeable. ○: The ink image of all colors has a glossy feeling in the printed area. I don't care about the difference in glossiness from the printed area. △: In some ink images, the glossiness in the printed area is small and the difference from the non-image area is a little worrisome, but it is practically acceptable ×: All There is no glossiness in the printed part over the color and the difference with the non-image part is remarkable (evaluation of bronzing).
After storage at 0% RH for 7 days, the bronzing was visually evaluated in the following 5 grades.

◎: Bronzing does not occur at all ○: Bronzing occurs in a slightly black solid portion Δ: Bronzing occurs in the black solid portion at a practically acceptable limit ×: Practically acceptable in the entire black solid portion Bronzing at a level that cannot be performed occurs (evaluation of the maximum density). In the printed image, the maximum printed density portion of the magenta image is measured by an optical densitometer (X-Rite X-
The concentration was measured using Rite 938), and racking was performed according to the criteria described below.

[0202] ◯: The maximum density is 2.10 or higher Δ: The maximum concentration is 1.90 or more and less than 2.10. X: Maximum concentration is less than 1.90 Table 3 shows each evaluation result obtained as described above.

[0203]

[Table 3]

As is clear from Table 3, the ink absorption layer surface
60 degree specular gloss of the side surface is 10-30%, Ra is 0.6
~ 4.0μm, Bristow penetration rate 20 ~ 100ml
/ M ²・ Sec^1/2The inkjet recording medium that is
The pigment particles whose absolute value of the data potential is -30 to -100 mV.
The sample of the present invention printed using the contained pigment ink,
Gloss difference, abrasion resistance, maximum density and printer
It can be seen that it has excellent transportability. In addition, the pigment
The maximum particle size (D99) of the pigment particles is 3
The average particle diameter of the pigment particles (D5
0) is 35 to 120 nm, and the ink absorption of the pigment is
The luminous intensity ε is yellow ink, magenta ink, or cyan ink.
50,000 or more and 50,000 or less for black ink, 50,000 or more for black ink1
50,000 or less, or the recording medium is cationic
The effect is further enhanced by containing the limmer
I was able to confirm that

Example 2 In the combination of the recording medium and the ink set of Example 1, the type of pigment and the surfactant were changed so that the zeta potential of the pigment particles used in the ink set would have a positive charge. As a result of the same evaluation, it was possible to confirm the same effect as in Example 1 by using pigment particles having a surface characteristic of +30 to +100 as the zeta potential.

[0206]

According to the present invention, there is provided an ink jet recording method capable of improving a feeling of strangeness caused by a difference in gloss between a printed portion and a non-printed portion, reducing glare in the printed portion, and obtaining a high print density. I was able to.

[Brief description of drawings]

FIG. 1 is a particle size distribution function curve representing D50 and D99 according to the present invention.

[Explanation of symbols]

1 Particle size distribution curve of pigment dispersion 2 Integral curve of particle size distribution function 3 Display of D99 4 Display of D50

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2C056 EA04 FC02 FC06                 2H086 BA02 BA15 BA19 BA21 BA24                       BA33 BA35 BA41 BA53 BA55                 4J039 BE01 BE29 EA15 EA16 EA17                       EA24 EA33 EA48 GA24

Claims (5)

[Claims] 1. An inkjet recording method for recording with a yellow pigment ink, a magenta pigment ink, and a cyan pigment ink on a recording medium having at least one ink absorbing layer on a support, the recording medium being an ink. 60 specified by JIS-Z-8741 on the surface of the absorption layer side
Degree specular gloss of 10 to 30%, center line average surface roughness Ra specified by JISB-0601 is 0.6 to 4.0 μm.
And has a Bristow permeation rate of 20 to 100 ml / m ^2.
An ink jet recording method characterized in that it is sec ^1/2 and at least one of the pigment inks contains pigment particles having an absolute value of zeta potential of 30 to 100 mV. 2. The maximum particle diameter (D99) of the pigment particles.
Is less than 300 nm, the inkjet recording method according to claim 1. 3. The average particle diameter (D50) of the pigment particles.
Is 35 to 120 nm.
Or the inkjet recording method described in 2. 4. The ink absorbance ε at 400 to 700 nm represented by the following formula 1 is 10,000 or more and 50,000 or less for yellow ink, magenta ink or cyan ink, and 50,000 or more and 150,000 or less for black ink. The inkjet recording method according to any one of claims 1 to 3, which is characterized in that. [Equation 1] [In the formula, OD represents an absorption concentration value, and Δλ represents a measurement wavelength interval. ] 5. The inkjet recording method according to claim 1, wherein the recording medium contains a cationic polymer.