JP2003089260A - Method for ink-jet recording - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for ink-jet recording with excellent resistance to scuffing, printing density and printer carrying properties by improving a sense of incongruity by decreasing in difference in gloss between a printed part and a non-printed part. SOLUTION: In the method for ink-jet recording wherein recording is performed on a recording medium with an ink-absorbing layer on a substrate by using a yellow pigment ink, a magenta pigment ink and a cyan pigment ink, the method for ink-jet recording is characterized by the recording medium having 60 deg. mirror surface gloss of the surface on the ink-absorbing layer face side of 10-30%, a surface roughness Ra on the central line of 0.6-4.0 μm and a surface roughness Ra on the central line on the surface on the opposite side to the ink-absorbing layer face of 0.6-2.5 μm and at least one of the pigment inks containing at least 50% by number of pieces of pigment particles with a needle-shape ratio (the maximum length/the minimum width of the particle) of 1-3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for recording an inkjet image, and more specifically, an inkjet recording which improves a difference in gloss between a printed portion and a non-printed portion and is excellent in abrasion resistance, print density and printer transportability. Regarding the method.

[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.

Further, when the dispersed ink is used for the dye ink in which the color material printed as described above enters the voids of the ink recording medium, it is exposed on the surface of the recording medium and becomes a deposited state. It has a problem that the scratching property is deteriorated.

As a method of eliminating such an uncomfortable feeling, a method of performing a laminating treatment after image recording and a method of pressing with a hot roll after the image formation are also known, but the treatment is required after the image formation, which is troublesome, In addition, there are drawbacks such as relatively large energy consumption and the need for a laminate material and a dedicated recording medium.

Further, when the recording medium is conveyed by the printer at the time of ink jet image formation, troubles such as misfeeding of not feeding paper and multi-feeding of feeding two or more sheets may occur due to the surface characteristics of the recording medium. Immediate response was required.

[0012]

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 reduction in gloss difference between a printed portion and a non-printed portion, and to improve abrasion resistance,
An object of the present invention is to provide an inkjet recording method which is excellent in print density and printer transportability.

[0013]

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
The 0 degree specular gloss is 10 to 30%, the center line surface roughness Ra defined in JIS B-0601 is 0.6 to 4.0 μm, and the surface of the surface opposite to the ink absorption layer surface with the support interposed therebetween is The center line surface roughness Ra is 0.6 to 2.5 μm,
At least one of the pigment inks contains 50 number% or more of pigment particles having a needle-shaped ratio (maximum length / minimum width of particles) of 1 to 3 or more.

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. The pigment ink contains a water-soluble polymer compound having a weight average molecular weight of 3,000 to 30,000 in an amount of 0.
The ink jet recording method according to any one of items 1 to 3, wherein the content is 3 to 10 mass%.

5. Any one of the above items 1 to 4, wherein the recording medium contains a cationic polymer.
Inkjet recording method according to item.

In view of the above problems, the present inventors have made earnest studies on the glossiness, abrasion resistance, and printer transportability of the formed inkjet output image, and as a result, found that the printing surface of the recording medium to be used has a surface of 60 degrees. By setting the specular gloss to a specific range, the centerline surface roughness Ra of each of the front and back surfaces of the recording medium to a specific value, and further specifically defining the shape of the pigment particles in the pigment ink, It significantly improves the inhomogeneity caused by the difference in texture between the image and non-image areas that tends to occur during printing, and gives the smoothness and texture of silver salt photographs, while also providing abrasion resistance and printer transportability. I found that it could be improved.

Further, the above effects can be further exhibited by setting the particle size of the pigment within a specific range, using a water-soluble polymer compound in the ink, or using a cationic polymer in the recording medium. The present invention has been found and 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 recording medium has a 60-degree specular gloss of 10 to 30% specified by JIS-Z-8741 on the surface of the ink absorption layer side, and JISB-0601.
Has a center line surface roughness Ra of 0.6 to 4.0 μm.
And the center line surface roughness Ra of the surface on the side opposite to the ink absorption layer surface with the support interposed is 0.6 to 2.5 μm, and at least one of the pigment inks has a needle-like ratio (maximum of particles). It is characterized by containing 50% by number or more of pigment particles having a length / minimum width of 1 to 3.

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.

The support used in the recording medium according to the present invention may be either a water-absorbing support or a non-water-absorbing support, but the non-water-absorbing 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 a fibrous substance such as wood pulp with various additives and using 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 surfaces 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 quality, and a high-quality image can 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 made of wood pulp as a main raw material, 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 pulp, a chemical pulp containing few impurities (sulfate pulp or sulfite pulp) is preferably used, and a pulp having a whiteness 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 for 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. are also partially used. 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, or when a polyethylene is melt-extruded on the surface of a base paper for coating, a so-called patterning treatment is performed to obtain a matte surface as 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 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
The center line surface roughness Ra of 0 to 30% and the center line surface roughness Ra specified in JIS B-0601 is 0.6 to 4.0 μm, and the center line surface of the surface opposite to the ink absorption layer surface with the support interposed therebetween. One of the characteristics is that the roughness Ra is 0.6 to 2.5 μm, but the method for achieving the characteristic value of the ink absorption layer surface side defined above is not particularly limited as its method.
A method of providing irregular or regular fine-grained surface irregularities on the surface of the recording medium by the method described below is preferable.

In terms of the unevenness in the present invention, from the viewpoint of preventing glare from being noticeably reduced and glaring being prevented, the surface on the ink absorbing layer side defined in the present invention is defined in JIS B-0601. Standard length 2.5m
m, the center line surface roughness Ra when measured at a cutoff value of 0.8 mm is 0.6 to 4.0 μm, JIS-Z-874.
It is necessary to provide unevenness such that the 60-degree specular glossiness of 1 satisfies 10 to 30%.

Due to the unevenness, the surface glossiness is appropriately suppressed to eliminate unnecessary glare, and there is no great difference in the glossiness at the time of inkjet recording between the printed portion and the non-printed portion. 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 reference 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 0.6 to 2.5 μm, which is one of the characteristics, but preferably 0.8 to 2.2 μm.
Is.

There is no particular limitation on the method for setting the center line surface roughness on the back surface side within the range specified in the present invention. For example, on the high density polyethylene layer provided on the back surface of the support, This can be achieved by coating a layer containing a silica matting agent and appropriately adjusting the particle size and addition amount of the silica matting agent.

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 absorption 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 a polyethylene resin, it is preferable to engrave the surface of the paper after coating the paper with the polyethylene resin.

A typical method of imprinting irregularities on the polyethylene resin surface in advance is to perform extrusion coating of molten polyethylene resin on a base paper, and then press it against 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 by 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 influenced by the above-mentioned unevenness of the support, the fine structure of the ink absorbing layer itself and the matting agent used as an auxiliary.

When the glossiness is less than 10%, the matteness of the surface is too high, which may result in an unclear image.
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.

Constituent factors of the ink jet recording medium according to the present invention 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, but 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, and 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 the state of being uniformly dispersed in the binder as the primary particles, or may be added in the state of forming secondary aggregated particles and being dispersed in the 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, flat-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 (may be a low molecular compound or a high molecular compound) 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 substance / 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 comprises
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, for example, 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 has little discoloration with time and deterioration of light resistance, 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 another copolymer of a monomer having a quaternary ammonium salt group. It is a copolymer with one or more monomers.

Examples of the monomer having a quaternary ammonium salt group include the followings.

[0078]

[Chemical 1]

[0079]

[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.

[0081]

[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.

[0083]

[Chemical 4]

[0084]

[Chemical 5]

[0085]

[Chemical 6]

[0086]

[Chemical 7]

Particularly 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 that does not contain the 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. In the present invention, at least one of the pigment inks has an acicular ratio (maximum length / minimum width of pigment particles) of 1 to
The feature is that the pigment particles of No. 3 are contained in an amount of 50% by number or more.

The acicular ratio referred to in the present invention can be determined by the method described below. Specifically, an ink containing pigment particles is diluted with an appropriate solvent so that the pigment concentration becomes 0.01%, and then dropped on a polyethylene terephthalate film hydrophilized by glow discharge and dried.

The film on which the pigment particles are mounted may be used for observation after Pt-C having a thickness of 3 nm is obliquely vapor-deposited by an electron beam from an angle of 30 ° with respect to the film surface by a vacuum vapor deposition apparatus. preferable.

For details of the electron microscope observing technique and the sample preparation technique, "Electron Microscope Society of Japan Kanto Branch Edition / Medical / Biological Electron Microscope Observation Method" (Maruzen), "Electron Microscope Society of Japan Kanto Chapter Edition / Electronics" Microscopic biological sample preparation method "(Maruzen) can be referred to respectively.

The produced sample was subjected to an accelerating voltage of 2 kV using a field emission scanning electron microscope (hereinafter referred to as FE-SEM).
The secondary electron image is observed at a magnification of 5,000 to 20,000 at 4 to 4 kV and the image is stored in an appropriate recording medium.

For the above-mentioned processing, it is convenient to use a device capable of AD-converting the image signal from the electron microscope main body and directly recording it as digital information on the memory, but recording it on Polaroid (registered trademark) film or the like. The converted analog image can also be used by converting it into a digital image with a scanner or the like, and performing shading correction, contrast / edge enhancement, etc. as necessary.

As for an image recorded on a suitable medium, it is preferable that one image is decomposed into at least 1024 pixels × 1024 pixels, preferably 2048 pixels × 2048 pixels or more, and image processing is performed by a computer.

As a procedure of the above-mentioned image processing, first, a histogram is prepared and binarization processing is performed to extract a portion corresponding to a pigment particle. The unavoidably agglomerated particles are cut by an appropriate algorithm or manual operation, and the contour is extracted. Then, the maximum length of each particle (MX
LNG) and the minimum width when sandwiched between two parallel lines, that is, the minimum ferret diameter width (WIDTH) is at least 1000.
Each particle is measured and the acicular ratio is calculated for each particle by the following formula.

Needle ratio = (MX LNG) / (WIDTH) After that, the number average of needle ratios for all measured particles is calculated. When performing the measurement according to the above procedure, it is preferable to sufficiently perform length correction per pixel (scale correction) and two-dimensional distortion correction of the measurement system using a standard sample in advance. As a standard sample, uniform latex particles (DULP) commercially available from Dow Chemical Company in the United States are suitable, and polystyrene particles having a coefficient of variation of less than 10% for a particle size of 0.1 to 0.3 μm are suitable. Preferably, specifically a particle size of 0.2
Lots with 12 μm and standard deviation 0.0029 μm are available.

Details of the image processing technology can be referred to “Hiroshi Tanaka, Image Processing Application Technology (Industry Research Committee)”,
The image processing program or device is not particularly limited as long as the above operation can be performed, and an example thereof is Luzex-III manufactured by Nireco.

In the present invention, at least one of the pigment inks has an acicular ratio (maximum length / minimum width of pigment particles) of 1.
It is characterized in that the pigment particles of No. 3 to 50 are contained in an amount of 50% by number or more, preferably 50 to 100% by number, more preferably 75 to 100% by number, particularly preferably 90 to 10%.
It is 0% by number. Further, the average value of the acicular ratio of the pigment particles is characterized by being 1 to 3, but preferably 1 to
It is 2.5.

By using the pigment particles having the above-defined acicular ratio, an image excellent in scratch resistance and gloss can be obtained.

In the present invention, the method for obtaining the pigment particles having the needle-like ratio defined above is not particularly limited, but, for example, a dispersant at the time of dispersing the pigment particles, a dispersing means, a dispersing condition and the like are appropriately selected. As a result, pigment particles having a desired acicular ratio can be obtained.

Examples of the pigment dispersant usable 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 abrasion resistance 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, but preferably 50 to 90 nm.
When the average particle diameter (D50) of the pigment particles exceeds 120 nm, the abrasion resistance 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. Therefore, 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 be within the specified range is not particularly limited. For example, as described above, the dispersing agent, dispersing means, dispersing agent at the time of dispersing the pigment particles are used. 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. For example, as described above, the dispersing agent, dispersing means, and the like at the time of dispersing the pigment particles,
This can be achieved by combining a method of appropriately selecting dispersion conditions and the like, and a method of separating coarse particles such as centrifugation or filter filtration after dispersion.

In the invention according to claim 4, the pigment ink is
It is characterized by containing 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, as a preferable example of the water-soluble polymer, a synthetic polymer can be mentioned. 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 characterized by being 30,000, but preferably 3,
000 to 20,000, more preferably 3,000
It is 0 to 10,000. If 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 scratching property is reduced. If it exceeds 30,000, the viscosity is increased, the dissolution is poor, the storage stability of the ink and the ejection stability are improved. This is not preferable because it tends to result in deterioration of the property.

The amount of the water-soluble polymer added is characteristically 0.3 to 10% by mass, preferably 0.6 to 4.0% by mass, based on the mass of the pigment ink. 0.3%
If it is less than 10% by weight, the effect of suppressing the growth and aggregation of the pigment particles is reduced, and the effect of improving the rubbing property 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 pigment is dispersed. Further, in the pigment ink according to the present invention, two or more kinds of the above water-soluble polymers may be used.

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

As the pigment that can be used in the present invention, conventionally known organic and inorganic pigments can be used. For example, azo pigments such as azo lakes, insoluble azo pigments, condensed azo pigments, chelate azo pigments, phthalocyanine pigments, perylene and perylene pigments, anthraquinone pigments, quinacridone pigments,
Polycyclic pigments such as dioxane pigments, thioindigo pigments, isoindolinone pigments, quinophthalone pigments, dye lakes such as basic dye type lakes and acid dye type lakes, nitro pigments, nitroso pigments, aniline black, daylight fluorescence Examples include organic pigments such as 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 a 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.

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 portion and the outer edge portion 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, more 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, 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 various 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 inkjet head used for inkjet recording 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 Specific examples include an inkjet type, a bubble jet (registered trademark) type, an electrostatic suction type (for example, an electric field control type, a slit jet type, etc.), and a discharge type (for example, a spark jet type). However, any ejection method may be used.

[0139]

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] Water content is 6.5% by mass and basis weight is 170.
A low-density polyethylene having a density of 0.92 was applied to a back surface of a g / m ² photographic base paper by an extrusion coating method to a thickness of 20 μm, and corona discharge was performed, and then a latex layer was 0.2 g / m thick. ^It was applied so as to be ² .

Then, a low-density polyethylene having a density of 0.92 and containing 5.5% by mass of anatase type titanium oxide was applied on the front side (on the side where the ink absorbing layer was coated) 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 molding treatment while being cooled using a cooling roll having irregularly shaped irregularities on the ink absorption layer coating surface side. Then, after corona discharge was applied to this surface, a gelatin subbing layer containing a cross-linking agent was added at 0.03 g /
m ^{2 was} applied to prepare Support 1.

[Preparation of Each Dispersion] (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, pH = 7.5, polyvinyl alcohol (Kuraray Co., Ltd .: PVA23)
5) 500 g, cationic polymer (exemplary compound P-
9) Add to 90 L of an aqueous solution containing 150 g and 10 g of the antifoaming agent SN381 of Sannobuco Co., Ltd. and disperse with a high-pressure homogenizer (manufactured by Sanwa Kogyo Co., Ltd.), and then make the total amount 100 L to obtain a uniform titanium oxide dispersion 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 is 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] Ink absorbing layer coating liquids for the first, second and third layers were prepared by the following procedure.

(Preparation of coating liquid for the 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 the first layer.

[0150]   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   Latex emulsion (Daiichi Kogyo KK: 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.

[0152]   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 liquid 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 liquid for third layer.

[0154]   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 Backside) The centerline surface roughness of the backside of the recording medium 1 prepared 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 grids at intervals of 3 cm, the center of each square region was measured, and the average value and standard deviation were calculated 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 the Y axis, and the roughness curve is represented by Y = f (X), the value obtained by the formula (Formula 1) is set to 8 mm. ).

[0157]

[Equation 1]

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

(Measurement of Centerline Surface Roughness of Surface) As a result of measuring the centerline surface roughness of the surface (ink-absorption layer coated surface) of the recording medium 1 prepared above by the same method as described above, 2.8 μm.
It was m.

(Measurement of 60-degree specular glossiness) The surface of the recording medium 1 prepared above was measured for 60-degree specular glossiness according to JIS-Z-8741, and as a result, the 60-degree specular glossiness was 18%. It was A gonio gloss meter (VGS-1001DP) manufactured by Nippon Denshoku Industries Co., Ltd. was used for the measurement.

<< 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.

(Production of Support 2) In the production of Support 1, 1.4 g / m ^{2 of} a methacrylate ester-based monodisperse matting agent having an average particle diameter of 0.3 μm was added to the latex layer on the back surface.
A support 2 was prepared in the same manner except that it was added so that

The front and back surface characteristics of the recording medium 2 manufactured 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 back surface was 2.8 μm, and the center line surface of the surface was Roughness is 2.8 μm, surface 60 degree specular gloss is 1
It was 8%.

<< Preparation of Recording Medium 3 >> A recording medium 3 was prepared in the same manner as in the preparation of the recording medium 1 except that the support 3 described below was used instead of the support 1.

(Production of Support 3) In the production of Support 1, 0.8 g / m ^{2 of} a methacrylic acid ester-based monodisperse matting agent having an average particle diameter of 0.3 μm was added to the latex layer on the back surface.
In the same manner as above, except that the polyethylene on the front side was melt-extruded and immediately after the extrusion was applied, the surface of the polyethylene on the front side was subjected to a molding process while being cooled using a cooling roll having a matte surface. It was made.

The front and back surface characteristics of the recording medium 3 manufactured 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 back surface was 1.2 μm, and the center line surface of the surface was Roughness 0.4 μm, surface 60 degree specular gloss 3
It was 5%.

<Preparation of Recording Medium 4> In the preparation of the recording medium 1, a recording medium 4 was prepared in the same manner except that the support 4 described below was used in place of the support 1.

(Production of Support 4) In the production of Support 1, 0.8 g / m ^{2 of} a methacrylate ester-based monodisperse matting agent having an average particle diameter of 0.3 μm was added to the latex layer on the back surface.
And the number of irregularly-shaped irregularities on the surface of the cooling roll used in the surface-side imprinting treatment is 1.6.
A support 4 was prepared in the same manner except that the number was doubled.

The front and back surface characteristics of the recording medium 4 manufactured as described above were measured by the same method as that used for the recording medium 1, and as a result, the center line surface roughness of the back surface was 1.2 μm, and the center line surface of the front surface was Roughness is 4.5 μm, surface 60 degree specular gloss is 7
%Met.

<< Preparation of Recording Medium 5 >> A recording medium 5 was prepared in the same manner as in the preparation of the recording medium 1 except that the support 5 described below was used instead of the support 1.

(Production of Support 5) In the production of Support 1, 0.8 g / m ^{2 of} a methacrylic acid ester-based monodisperse matting agent having an average particle diameter of 0.3 μm was added to the latex layer on the back surface.
A support 5 was prepared in the same manner except that it was added so that

The front and back surface characteristics of the recording medium 5 manufactured as described above were measured by the same method as that used for the recording medium 1, and as a result, the center line surface roughness of the back surface was 1.2 μm, and the center line surface of the front surface was 1.2 μm. Roughness is 2.8 μm, surface 60 degree specular gloss is 1
It was 8%.

<< Preparation of Recording Mediums 6-9 >> Recording Medium 5
In the production of, the center line surface roughness of the back surface, the center line surface roughness of the surface, and the 60-degree specular gloss of the surface have the characteristic values described in Table 1, so that the amount of the matting agent added on the back surface side is In addition, on the front side, using the supports 6 to 9 in which the number of irregular irregularities on the surface of the cooling roll is appropriately changed, the recording medium 6 to
9 was produced.

<< Preparation of Recording Medium 10 >> In the same manner as in preparation of the recording medium 5, except that the cationic polymer (P-1) in each dispersion used in the formation of the ink absorbing layer was omitted. 10 was produced.

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

[0176]

[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 Magnesium pigment dispersion 1 was prepared by dispersing 60% by volume of a horizontal bead mill (Ashizawa Co., Ltd .: System Zeta Mini) and then removing undispersed coarse particles by centrifugation.
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 (Ashizawa Co .: System Zetamini) 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 (Ashizawa Co .: System Zetamini) in which 0.3 mm zirconia beads were packed at a volume ratio of 60%, and then undispersed coarse particles were removed by centrifugation to obtain a black pigment. Dispersion 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.

(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: Nissin 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, the pore size 1
Magenta ink 1 was prepared by passing it twice through a Millipore filter of μm.

(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: Nissin 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, the pore size 1
Cyan ink 1 was prepared by passing twice through a μm Millipore filter filter.

(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: Nissin 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, the pore size 1
Black ink 1 was prepared by passing through a μm Millipore filter filter twice.

[Measurement of Needle Ratio of Each Ink, D99, D50] (Measurement of Needle Ratio) Each pigment ink was diluted to 0.01% pigment concentration, and pigment ink droplets were dropped on a polyethylene terephthalate film. After drying, a sample was prepared using a JFD-7000 type (manufactured by JEOL Ltd.) as a vacuum vapor deposition device, and an acceleration voltage of 2. S-5000H type (manufactured by Hitachi Ltd.) was used as an FE-SEM. The number of visual fields was selected and observed so that the number of pigment particles was 1000 or more at 0 kV. The images were digitized and transferred to a connected filing device (VIDEOBANK) and stored in an MO disc. Subsequently, LUZEX-III type (manufactured by Nireco)
When the particles were overlapped or contacted by the image processing apparatus, the particles were extracted by a manual operation, and the acicular ratio (MX LNG / WIDTH) was measured for each particle, and the average value was obtained.

The needle-like ratio of the pigment ink set 1 obtained by the above method is as follows. Yellow ink 1: 1.73 Magenta ink 1: 1.69 Cyan ink 1: 1.78 Black ink 1: 1.84 (D99, D50 measurement) 1,0 measured by the above method
A particle size distribution curve 1 in which the abscissa is the particle size (D) and the ordinate is the particle number function (G) shown in FIG. , Integral curve 2
Thus, the particle size points D50 and D99 corresponding to 50% by number and 99% by number in the particle number function 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 to 6 >> In the preparation of the pigment ink set 1, the conditions or presence / absence of centrifugal separation at the time of preparation of each pigment dispersion 1, the dispersion strength, and the pore size of the filter at the time of preparation of each pigment ink and the number of filtrations were appropriately adjusted and combined, and shown in Table 2. Pigment ink sets 2 to 6 having the above-mentioned acicular ratio, D50, and D99 characteristics were prepared.

<< Preparation of Pigment Ink Set 7 >> In the preparation of Pigment Ink Set 1, the styrene-acrylic acid copolymer (molecular weight 10,0) used when preparing each pigment dispersion 1 was prepared.
No. 00, acid value 120), Jonkryl 61 (acrylic-styrene resin, manufactured by Johnson), and styrene-acrylic acid copolymer (molecular weight 7,000, acid value 150) were used in the same manner except that the pigment ink was omitted. Set 7 was prepared.

Table 2 shows the needle-like ratios, D50 and D99, of the respective color inks of the respective ink sets prepared as described above.

[0191]

[Table 2]

<Image printing> By combining the recording medium shown in Table 3 and the pigment ink set, the nozzle hole diameter was 20 μm.
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 16 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).

<< Characteristic Evaluation of Printed Image >> Each of the following characteristic evaluations was performed on the printed image produced 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 criteria described below to evaluate the gloss difference.

⊚: The ink image of all colors has a marked glossy feeling in the printed part, and the difference from the non-printed part is not noticeable. ○: The ink image of all colors has a glossy feeling in the printed part, 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 from the non-image part is significant (evaluation of abrasion resistance). The highest print density part of each printed image is erased 10 times with an eraser (MONO Dragonfly pencil company). The degree of stains on the printed part when rubbed was visually observed, and the rub resistance was evaluated according to the criteria described below.

⊚: No stain is observed on the printed part. ◯: Slight stain on the printed part is observed. Δ: Slight stain on the printed part is observed, but it is in a practically acceptable range. The stain was clearly observed, which was a problem in practical use (evaluation of the highest density). Among the printed images, the highest printed density portion of the magenta image was measured with an optical densitometer (X-Rite X-
The concentration was measured using Rite 938), and racking was performed according to the criteria described below.

◯: Maximum density is 2.10 or more Δ: Maximum density is 1.90 or more and less than 2.10 ×: Maximum density is less than 1.90 (evaluation of printer transportability) <Evaluation of continuous transportability> 20 sheets of each recording medium are stacked and set in the printer, and the image is printed by the above-mentioned method.
Twenty sheets were continuously performed in a 55 ° C., 55% RH atmosphere.

◯: All 20 sheets were conveyed without any problem Δ: 1-2 cases were double-fed or cases were not conveyed ×: 3-5 sheets were double-fed or cases were not conveyed × X: A case where 6 or more sheets were double-fed or not conveyed <Evaluation of single sheet conveying property> Only one cane was set in the above printer and printed in an atmosphere of 23 ° C and 55% RH.

[0199] ○: Transported without problems △: A little meandering can be printed ×: Meandering occurs and printing cannot be performed well XX: It meanders greatly and the recording medium is not conveyed. Table 3 shows each evaluation result obtained as described above.

[0200]

[Table 3]

As is clear from Table 3, the 60-degree specular gloss of the ink absorbing layer side surface is 10 to 30%, the Ra is 0.6 to 4.0 μm, and the back surface Ra is 0.6 to 2. 5μ
The sample of the present invention, which was printed by using a pigment ink containing pigment particles having an acicular ratio (maximum length / minimum width of pigment particles) of 1 to 3 on an inkjet recording medium of m, is a comparative example. On the other hand, it is found that the difference in gloss, the abrasion resistance, the maximum density, and the transportability to the printer are excellent. Furthermore, in the pigment ink used, the maximum particle diameter (D99) of the pigment particles is
The average particle size of the pigment particles (D
50) is 35 to 120 nm, contains a water-soluble polymer compound having a weight average molecular weight of 3,000 to 30,000 in an amount of 0.3 to 10% by mass, or the recording medium contains a cationic polymer. Therefore, it was confirmed that the effect was further exerted.

[0202]

According to the present invention, it is possible to provide an ink jet recording method in which the discomfort due to the reduction of the gloss difference between the printed portion and the non-printed portion is improved, and the abrasion resistance, the print density and the printer transportability are excellent. .

[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 function 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 FC01 FC06                 2H086 BA01 BA15 BA35 BA37 BA41                       BA53 BA55 BA59 BA60                 4J039 AB01 AB02 AB07 AD03 AD06                       AD08 AD09 AD10 AD11 AD14                       AD23 BA04 BE01 CA06 EA15                       EA16 EA17 EA33 EA36 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
The degree of specular gloss is 10 to 30%, the center line surface roughness Ra specified in JIS B-0601 is 0.6 to 4.0 μm, and the center of the surface opposite to the ink absorption layer surface with the support interposed. The line surface roughness Ra is 0.6 to 2.5 μm, and at least one of the pigment inks contains 50% by number or more of pigment particles having an acicular ratio (maximum length / minimum width of particles) of 1 to 3. An inkjet recording method characterized by the above. 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 pigment ink has a weight average molecular weight of 3,
000-30,000 water-soluble polymer compound 0.3-
The inkjet recording method according to any one of claims 1 to 3, wherein the content is 10% by mass. 5. The inkjet recording method according to claim 1, wherein the recording medium contains a cationic polymer.