JP2000094831A - Recording medium and image forming method using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a medium to be recorded of superior ink absorption capability providing the high image density, sharp color tone and a number of gradations and not generating the color taste variation caused by density even when the printing by a pigment/dye mixed ink, the printing of combining a pigment ink with a dye ink, the printing of ink set of three kinds or more of different density or the like is carried out at high speed and also controlling the generation of beadings. SOLUTION: A medium to be recorded is of the structure in which a porous layer 4 containing an alumina hydrate of boehmite structure and a binder as a lower layer and a porous layer 5 composed of silica and a binder as an upper layer are formed on a base 2 in the above order, and voids are formed in the lower layer, and voids are communicated with the surface of an ink acceptive layer 3 through pores 7 of the radius smaller than the voids.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording medium suitable for recording using an aqueous ink, and more particularly to printing with a pigment / dye mixed ink, combined printing of a pigment ink and a dye ink, and three or more densities. When printing with a different ink set at high speed, the image density is high, the color tone is clear, the number of gradations is large, there is no color change due to density,
The present invention relates to a recording medium suitable for inkjet recording, which suppresses the occurrence of beading and has excellent ink absorbing ability, and an image forming method using the same.

[0002]

2. Description of the Related Art In recent years, an ink jet recording system records fine images or characters by flying fine droplets of ink according to various operating principles and attaching them to a recording medium such as paper. Features include high speed, low noise, easy multi-coloring, great flexibility in recording patterns, and no need for development and fixing.
2. Description of the Related Art As an image recording device for various images, it is rapidly spreading in various uses including information devices. Furthermore, images formed by the multi-color ink jet method can obtain multicolor printing by the plate-making method and recording comparable to printing by the color photographic method, and are usually used when the number of copies is small. It is being widely applied to the field of full-color image recording because it is cheaper than multicolor printing and printing.

The recording apparatus and the recording method have been improved in accordance with the improvement of the recording characteristics such as high-speed recording, high definition, full color, etc. However, the recording medium also requires advanced characteristics. It has become.

In order to solve such demands, various types of recording media have been proposed. For example, Japanese Patent Application Laid-Open No. 52-53012 discloses an ink jet paper in which a low-size base paper is impregnated with a paint for surface treatment. JP-A-53-49113 discloses an ink-jet paper in which a sheet containing urea-formalin resin powder is impregnated with a water-soluble polymer. JP 5
JP-A-6-5830 discloses an ink jet recording paper provided with an ink absorbing coating layer on the surface of a support.
JP-A-5-51583 discloses an example in which amorphous silica is used as a pigment in a coating layer. JP-A-55-144172 discloses an image receiving sheet having a pigment coating layer that adsorbs a coloring component of an aqueous ink. JP-A-55-146786 discloses an example using a water-soluble polymer coating layer.

[0005] US Patent Nos. 4,879,166 and 5
104730, JP-A-2-276670, 3
JP-A-215082, JP-A-3-281383, and JP-A-7-089221, JP-A-7-172038, JP-A-7-232473 of the present inventors,
JP-A-7-232474, JP-A-7-232475, JP-A-8-132731, JP-A-8-174499, JP-A-9-066664, JP-A-9-076628
Gazette, JP-A-9-086035 and JP-A-9-09962
No. 7, a recording sheet having an ink receiving layer using an alumina hydrate such as pseudo-boehmite is proposed.

US Pat. No. 4,879,166, European Patent 29
No. 8424, JP-A-1-97678 and JP-A-6-480.
JP-A Nos. 16-55829 and 16-55829 propose a recording medium in which alumina hydrate and silica having a specific adsorptivity are used in combination. U.S. Pat. No. 5,104,730, European Patent 407,720, JP-A-2-27671, JP-A-3-281383, JP-A-4-115984, and JP-A-4-115985 disclose porous fine powder on a porous alumina layer. A recording medium having a configuration in which a silica layer is laminated has been proposed.

Japanese Unexamined Patent Publications Nos. 62-174183, 1-114183 and 6-255235,
JP-A-6-270530 proposes a recording medium containing silica and alumina.

US Pat. No. 5,463,178, European Patent 63
No. 4287 and JP-A-7-76162 propose a recording medium having a structure in which a layer made of silica gel is laminated on a porous alumina hydrate layer. JP-A-8-208
Nos. 7 and 8-2091 have a configuration in which a silica gel layer is laminated on a porous alumina hydrate layer, and irregularities are formed on the surface of an ink receiving layer, and resin particles and silica particles are deposited on the silica layer. A recording medium containing the same has been proposed.

Japanese Patent Application Laid-Open No. Hei 8-290654 discloses a structure in which spherical primary particles of silica having a thickness of 0.1 to 10 μm are mutually bonded on a paper base material and has a thickness of 5 μm on a silica gel layer containing no secondary particles. A recording medium having a porous alumina hydrate layer of １００100 μm has been proposed. JP-A-3-2150
Nos. 80, 3-256785 and 7-089
No. 220, No. 7-101142, No. 7-11
No. 7335 proposes a recording medium in which the ink receiving layer has a two-layer structure and the upper layer is a glossy layer mainly composed of colloidal silica.

JP-A-9-150571 and 9-1
75000, 9-183265, 9-
183267, 9-286165, 1
No. 0-71764 discloses that the ink receiving layer has a two-layer structure, and silica or silica alumina is used for the surface layer.
There has been proposed a recording medium in which the pore structure and the particle diameter are within a specific range.

The ideas described above relate to the improvement of each characteristic of a recording medium, such as ink absorption, resolution, image density, color, color reproducibility, transparency, and glossiness. Even so, the following problems have occurred with the recent progress in recording devices that have achieved high-speed printing of image quality comparable to silver halide photography. (1) A recording medium in which an ink receiving layer has a two-layer structure in order to improve ink absorbency has been proposed. For example,
U.S. Pat. No. 5,104,730, EP 407720, JP-A-2-276671, and 3-28138.
Nos. 3, 115984 and 4-11598
No. 5 is a recording medium having a structure in which a porous fine silica layer is laminated on a porous alumina layer. The color material component of the printed ink is adsorbed by the porous alumina layer, and the silica layer absorbs the solvent component of the ink. In this configuration, ink absorption and color development are good due to functional separation, but in order to obtain good color development, it is necessary to use alumina hydrate with strong dye adsorption power. There was a problem that the width became narrow. Further, the silica layer used for absorbing the solvent of the ink has a problem that the silica layer becomes cloudy because fine silica powder is used. (2) There is a method of forming a two-layer ink receiving layer and obtaining surface gloss by using silica for the surface layer. For example, JP
No. 21580, No. 3-256785, No. 7
JP-A-089220, JP-A-7-101142 and JP-A-7-117335 disclose a recording medium having a form in which an ink-receiving layer has a two-layer structure and an upper layer is a glossy layer mainly composed of colloidal silica. Proposed. This method certainly increases the surface gloss of the ink receiving layer, but the gloss expressing layer is formed as a thin layer with a large pore radius in order to achieve both glossiness and ink absorption. However, there is a problem that the roundness is not easily increased. Further, since a polymer latex or casein is used for the casting in the gloss expression layer, there is a problem that the gloss of the printed portion is reduced. To improve this, Japanese Patent Application Laid-Open Nos. 9-286165 and 10-71764 propose a method using silica or silica-alumina aggregated particles for the surface layer. The idea is to achieve both ink permeability and gloss by controlling silica or the like having a primary particle diameter in a specific range to a secondary particle diameter in the specific range. However, since the silica layer forms secondary particles, there is a problem that the transparency of the ink receiving layer is not sufficient.

[0012]

SUMMARY OF THE INVENTION The present invention has been made for the purpose of solving the above-mentioned problems, and includes printing with a pigment / dye mixed ink, printing with a combination of a pigment ink and a dye ink, and printing three or more types. Printing with ink sets with different densities of
Even when printing at high speed, image density is high,
Provided is a recording medium having a clear color tone, a large number of gradations, no change in tint due to density, suppressing the occurrence of beading, and having excellent ink absorbing ability, and an image forming method using the recording medium. It is in.

[0013]

The above objects and objects are solved and achieved by the present invention described below. That is, the present invention relates to a recording medium having a two-layered ink-receiving layer in which a porous layer containing alumina hydrate having a boehmite structure and a binder and a porous layer containing silica and a binder are sequentially laminated on a substrate. In the medium, the ink receiving layer has voids inside a lower layer containing alumina hydrate and a binder, and the voids communicate with the surface of the ink receiving layer through pores having a smaller radius. The present invention discloses a recording medium.

According to the present invention, there is provided an image forming method for forming an image by applying ink to a recording medium, wherein the recording medium is the recording medium of the present invention. It discloses a method.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION In the recording medium of the present invention, the recording medium has a porous layer containing a boehmite-structured alumina hydrate and a binder and a porous layer containing silica and a binder on a base material. It has a configuration in which a two-layer ink receiving layer (hereinafter, ink receiving layer) formed in order is provided. FIG. 1 shows a schematic cross-sectional view of an example of a typical structure.

Alumina hydrate has a positive charge, so that the ink dye is fixed well and an image with good color development can be obtained, and there are no problems such as brown discoloration of the black ink and discoloration due to light fastness. Preferred materials are used for the ink receiving layer. As the alumina hydrate used in the recording medium of the present invention, an alumina hydrate having a boehmite structure by an X-ray diffraction method is preferable because it has good dye fixing properties, color development, ink absorbency, and transparency. Alumina hydrate is defined by the following general formula.

[0017]

## STR1 ## _{Al 2 O 3-n (OH} ) 2n · mH 2 O However Shikichu, n represents one of integers of 0 to 3, m is 0
It has a value of 10, preferably 0-5. The expression mH ₂ O often refers to a detachable aqueous phase that does not participate in the formation of the crystal lattice, so that m can also be a non-integer value.

In general, the crystal of alumina hydrate having a boehmite structure is a layered compound whose (020) plane forms a giant plane, and shows a diffraction peak specific to an X-ray diffraction pattern. In addition to complete boehmite, a structure called "pseudo-boehmite" containing an excessive amount of water between layers on the (020) plane can be employed. The X-ray diffraction pattern of this pseudo-boehmite shows a broader diffraction peak than boehmite. Since boehmite and pseudo-boehmite cannot be clearly distinguished from each other, they are referred to as alumina hydrate having a boehmite structure (hereinafter, alumina hydrate) including both, unless otherwise specified in the present invention.

The present inventors have proposed a recording medium using an alumina hydrate having a boehmite structure. The present application is an improvement thereof, in which a porous layer containing silica and a binder is formed on a porous layer containing alumina hydrate having a boehmite structure and a binder and having a cavity inside the layer.
The recording medium having the ink receiving layer having a cavity inside the layer had good ink absorbency for the second and subsequent colors when multicolor printing was performed at high speed. The inventors of the present invention further applied the recording medium having the two-layered ink receiving layer to printing with a pigment / dye mixed ink, printing using a pigment ink and a dye ink in combination, and using three or more types of ink sets having different densities. Even when high-speed printing is performed at a high speed, the ink density is excellent, the image density is high, the color tone is clear, the number of gradations is large, there is no color change due to density, and beading occurs. It has been found that no recording medium can be obtained. Further, the number of gradations can be increased by a printing method using a color material having a different color tone, such as a light and dark ink containing a black color material and a light and dark ink containing a mixed color material of a black color material and a blue color material. .

The method for producing the alumina hydrate used in the present invention is not particularly limited, but any method capable of producing an alumina hydrate having a boehmite structure, for example, hydrolysis of aluminum alkoxide, sodium aluminate It can be produced by a known method such as hydrolysis.

As the alumina hydrate used in the present invention, any alumina hydrate having a boehmite structure by X-ray diffraction can be used.
There is no particular limitation. For example, alumina hydrate containing titanium dioxide described in Japanese Patent No. 2714351 can be used. Content ratio of alumina hydrate is 0.01 to
1.00% by weight is preferable because the optical density becomes high. The content and distribution of titanium dioxide are described, for example, in Japanese Patent No. 27143.
It can be measured using the method described in No. 51. As another form, alumina hydrate containing silica described in Japanese Patent Application No. 10-174778 can be used. When silica-containing alumina hydrate is used, the content of silica is preferably from 0.1% by weight to 30% by weight. The crystallinity of the alumina hydrate layer is preferably in the range of 15 to 80. As a method for measuring the crystallinity and the silica content, the method described in JP-A-8-132731 can be used.

The shape of the alumina hydrate can be determined by dispersing the alumina hydrate in water, alcohol, or the like, dropping it on a collodion film, preparing a measurement sample, and observing the sample with a transmission electron microscope. Among the alumina hydrates, pseudo-boehmite is described in the literature (Rocek J., et al, Applied Catalysis, 7).
4, Vol. 29-36, 1991), it is generally known that there are cilia-like shapes and other shapes.

In the present invention, any of cilia-shaped or plate-shaped alumina hydrates can be used.
The shape (particle shape, particle size, aspect ratio) of alumina hydrate is prepared by dispersing alumina hydrate in ion-exchanged water and dropping it on a collodion membrane to prepare a sample for measurement. It can be measured by observation.

According to the findings of the present inventors, a flat plate shape has better dispersibility in water than a needle-like or hair-like bundle (ciliform). The random orientation of the hydrate particles is more preferable because the pore volume is large and the pore size distribution is wide. Here, the hair bundle shape refers to a state in which needle-like alumina hydrates are gathered like a bundle of hair in contact with side surfaces.
The aspect ratio of tabular grains is 5-160115
It can be determined by the method defined in the publication. The aspect ratio is indicated by the ratio of the diameter to the thickness of the particle.
Here, the diameter indicates the diameter of a circle having an area equal to the projected area of the particles when the alumina hydrate is observed with a microscope or an electron microscope. The aspect ratio is observed in the same manner as the aspect ratio, and is expressed by the ratio of the minimum value diameter to the maximum value diameter of the flat surface. In the case of the hair bundle shape, the method of determining the aspect ratio is to obtain the diameter and length of the upper and lower circles, respectively, using the individual acicular alumina hydrate particles forming the hair bundle as a cylinder, and calculating the aspect ratio. It can be determined by taking the ratio.

The most preferred shape of the alumina hydrate is a flat plate having an average aspect ratio of 3 to 10 and an average particle diameter of 1.0 to 50 nm, and a hairy bundle having an average aspect ratio of 3 to 10. The average particle length is preferably in the range of 1.0 to 50 nm in the range of 10 to 10. When the average particle diameter or the average particle length is within the above range, light scattering can be suppressed, so that the transparency of the ink receiving layer can be improved. When the average aspect ratio is within the above range, a gap is formed between particles when the ink receiving layer is formed, so that a porous structure can be easily formed.

When the average particle diameter or the average particle length is smaller than the lower limit of the above range, the pore size distribution becomes narrow and the ink absorption rate decreases, and when the average particle diameter or the average particle length is larger than the upper limit of the above range, haze occurs in the ink receiving layer. It is easy to occur and transparency may be reduced. When the average aspect ratio is smaller than the lower limit of the above range, the pore size distribution range of the ink receiving layer is narrowed and the ink absorption rate is reduced, and when the average aspect ratio is larger than the upper limit of the above range, the alumina hydrate In some cases, it may be difficult to produce particles having a uniform particle size.

The silica used in the present invention may be any of silica sol (colloidal silica) in which primary particles are monodispersed, silica colloid particles composed of secondary particles in which primary particles are aggregated, gel type silica, and sedimentation type silica. Can be. As a method for producing silica, any of a dry method and a wet method can be used. The shape of the silica may be, for example, either spherical or non-spherical. The particle size of the silica is not particularly limited, but is preferably in the range of 3 to 200 nm. Within this range, both ink absorbency and transparency can be achieved. Further, two or more kinds of silica can be used in combination. 20 in that case
A combination of inorganic fine particles having a diameter of 40 nm to 200 nm or less is desirable because cracks can be prevented from occurring and transparency is good. As described in JP-A-6-183131, silica having a particle size of 20 nm or less can be used as a binder. Further, it is more preferable that the silica particle diameter is 100 nm or less, since the surface is not disturbed after printing and the roundness of the printed dots is improved.

The recording medium of the present invention can be obtained by forming a porous ink receiving layer using alumina hydrate, silica and a binder. Various characteristics of the recording medium include alumina hydrate used, type and amount ratio of silica and binder, type and amount of additive, dispersion condition of coating liquid in which alumina hydrate is dispersed, heating condition during drying. Can be changed by

The porous lower layer containing the boehmite-structured alumina hydrate and the binder in the present invention has voids therein, and the voids communicate with the surface of the ink receiving layer through pores having a smaller radius. And preferably has a structure in which voids communicate with each other by pores inside the ink receiving layer. FIG. 2 shows a schematic cross-sectional view of one example of FIG. 1. The recording medium 1 has a structure in which an ink receiving layer 3 having a lower layer 4 and an upper layer 5 is provided on a base material 2, and an inner cavity 6 in the lower layer 4 has a smaller radius than the inner cavity 6. The surface of the ink receiving layer 3 communicates with the outside air through the pores 7.

The pore structure of the ink receiving layer can be measured by a nitrogen adsorption method or a mercury intrusion method. It is preferable that the maximum peak in the pore radius distribution is in the range of 2.0 to 20.0 nm. Within this range, both ink absorption speed and dye fixing speed can be increased to prevent bleeding and bleeding. A more preferred lower limit of this radius range is a radius of 6.0 nm, and an upper limit is 1
8.0 nm. Within this range, bleeding, bleeding, and color unevenness may occur even when printing is performed using any of the following inks: a pigment ink, a dye ink, a dye ink and a pigment ink, and a mixed ink. Can be prevented. The lower limit of the most preferred range is a radius of 6.0 nm.
And the upper limit is 16.0 nm. Within this range, even when three or more types of inks having different color material densities are used, there is no difference in tint due to the densities.

When the range of the maximum peak exceeds the upper limit of the above range, the fixing speed of the dye is reduced to cause bleeding and the roundness of the printed dot tends to be reduced. Also,
Below the lower limit of the above range, the ink absorption speed tends to decrease.

Here, bleeding refers to a phenomenon in which, when solid printing is performed on a fixed area, the area of a portion colored with a dye becomes larger (larger) than the printing area.
This is a phenomenon in which bleeding occurs at the boundary between different colors in a solid-color printed portion, and dyes are mixed without being fixed.

The pore volume of the ink receiving layer is 0.4 to 1.0.
It is preferably in the range of ml / g. Within this range, the ink absorption amount and ink absorption speed are good. Further, when the pore volume is in the range of 0.4 to 0.6 ml / g, the haze of the ink receiving layer can be reduced to improve the transparency, and the mechanical strength can be increased to reduce the occurrence of cracks. It is more preferable because it can be suppressed. If the pore volume exceeds the upper limit of the above range, cracks or peeling of the ink receiving layer, powder dropout occurs, or haze occurs, and the transparency tends to decrease. If the amount is less than the lower limit of the above range, the amount of ink absorption is insufficient and ink overflows, or the ink absorption speed is insufficient and ink fixability in the printing unit tends to decrease.

Further, the pore volume per unit area of the ink receiving layer is preferably 8 ml / m ² or more. In this range, ink overflow does not occur even when high-speed printing is performed. More preferably, in the range of 20 ml / m ² or more, even when multicolor printing is performed, ink does not overflow. If the pore volume per unit area is less than the lower limit of the above range,
In particular, when performing multi-color printing, ink overflows from the ink receiving layer and bleeding is likely to occur in the image. As a method of adjusting the pore volume, generally use a method selected from methods for adjusting the pore volume of the porous material, such as control of aging conditions of the alumina hydrate and control of the dispersion and drying conditions of the coating liquid. Can be. As a method for increasing the pore volume, for example,
Various methods described in -120508 can be used. The method of setting the pore volume per unit area in the above range can be similarly achieved by adjusting the alumina hydrate, the coating liquid, the coating / drying conditions, the thickness of the ink receiving layer, and the like.

Further, the pore volume of the pores of the ink receiving layer is as follows:
The pore volume with a pore radius of 2.0 to 20.0 nm is preferably 80% or more of the total pore volume. Within the above range, the transparency and surface smoothness of the ink receiving layer can be increased. If the amount is less than the lower limit of the above range, the transparency of the ink receiving layer is reduced, and the mechanical strength is reduced, so that cracks and powder fall are likely to occur.

Next, the size, radius, volume ratio, and the like of the voids inside the ink receiving layer in the present invention can be determined by observing the cross section of the ink receiving layer with an electron microscope or the like and measuring on a photograph thereof.

The radius of the void inside the ink receiving layer needs to be larger than the radius of the pores, and is preferably 1.5 times or more larger than the peak radius of the pores. Within the above range, it can sufficiently fulfill the role of diffusion and the like described above,
Even when printing is performed at a high speed with a recent high-speed full-color printing apparatus and with a large amount of ink per unit area, the ink can be quickly absorbed and the overflow of the ink can be prevented. A particularly desirable range is a range of a radius of 50.0 to 200.0 nm. In this range, it is possible to reliably prevent the occurrence of white turbidity and cracks in the ink absorbing layer. Radius is 200.0n
When m is larger than m, the ink receiving layer tends to be clouded, whereby the transparency is lowered and the mechanical strength is insufficient, so that cracks are easily formed.

In the present invention, the water absorption of the ink receiving layer is preferably in the range of 0.4 to 1.0 ml / g. Within this range, it is possible to prevent overflow of ink when repeatedly printing with a large amount of ink as in multicolor printing. A more preferred range is 0.6 to 0.9 ml / g.
Within this range, cracking and deformation of the ink receiving layer before and after printing can be prevented. If the amount of water absorption exceeds the upper limit of the above range, the mechanical strength of the ink receiving layer is insufficient, cracks and peels, powder fall occurs,
If the transparency is easily reduced, and if the lower limit of the range is less than the lower limit of the above range, the ink absorption speed of the second and subsequent colors decreases when multicolor printing is performed, and the diameter of the dots printed in the second and subsequent colors increases, resulting in a mixed color portion. Color uniformity tends to decrease.

The water absorption of the ink receiving layer is 10 to 50.
g / m ² is preferred. Within this range, beading and bleeding can be prevented from occurring even when printing is performed at a high speed, such as full-color printing, particularly when a large amount of ink is applied per unit time. Further, 15 to 40 g / m ²
In the range, the selection range with respect to the amount of ink to be printed is widened, and the dot diameter becomes constant independently of the amount of printing. If the amount of water absorption exceeds the upper limit of the above range, the dot diameter is small when the amount of ink to be printed is small, white spots are likely to occur, and the image tends to be unnatural in stippling style. When printing is performed, ink overflow and beading are likely to occur.

Here, the water absorption can be measured according to the following method. The recording medium on which the ink receiving layer is formed is cut into a square having a side length of 100 mm. Ion-exchanged water is dripped little by little into the center, and each time it is spread evenly with a spatula and absorbed. This operation is repeated until the ion exchange water overflows. Ion exchange water remaining on the sample surface is wiped off with a cloth or the like. The amount of water absorption is determined from the weight difference of the recording medium before and after the absorption of ion-exchanged water.

In the present invention, the in-plane diffusion coefficient of the ink receiving layer is preferably in the range of 0.7 to 1.0. Within this range, the ink absorption speed does not decrease even when overprinting two to four or more colors at short time intervals of about 50 ms.

Here, the in-plane diffusion coefficient of the ink receiving layer is:
This is an amount indicating the ease with which the printed ink is diffused in the plane of the ink receiving layer, and can be determined from the water absorption of the recording medium and the absorption at one point of the recording medium as described below. The absorption amount at one point on the recording medium can be determined by the following method. Similarly to the amount of water absorption, the recording medium on which the ink receiving layer is formed is cut into a square having a side length of 100 mm, and ion-exchanged water is dropped and absorbed little by little at a central point. It is necessary to prevent the ion-exchanged water dropped at this time from spreading on the surface of the ink receiving layer before being absorbed at the dropping point. As in the measurement of the water absorption, this operation is repeated until the overflow occurs, and the absorption amount at one point of the recording medium is determined from the weight difference of the recording medium before and after the absorption of ion-exchanged water. Then, the absorption amount at one point of the recording medium /
The amount of water absorption of the recording medium is determined and used as the in-plane diffusion coefficient.

The BET specific surface area of the ink receiving layer of the present invention is preferably in the range of 70 to 300 m ² / g. In this range, light scattering is reduced and the transparency of the ink receiving layer is improved. In addition, by using the fine alumina hydrate, the fixing speed and fixing amount of the dye to the alumina hydrate can be increased. When the BET specific surface area is smaller than the lower limit of the above range, the ink receiving layer is easily clouded, and the dye adsorption point is insufficient, so that the water resistance of the dye may be insufficient. When the BET specific surface area is larger than the upper limit of the above range, cracks are easily generated in the ink receiving layer.

In the present invention, alumina hydrate or silica can be used by adding other additives. As the additive, any of various metal oxides, salts of divalent or higher-valent metals, and cationic organic substances can be freely selected and used as necessary.

Examples of the metal oxide include oxides such as silica, silica alumina, boria, silica boria, magnesia, silica magnesia, titania, zirconia, and zinc oxide.
Hydroxides and salts of metals having two or more valencies include salts such as calcium carbonate and barium sulfate, and halogens such as magnesium chloride, calcium bromide, calcium nitrate, calcium iodide, zinc chloride, zinc bromide and zinc iodide. Preference is given to chloride salts, kaolin, talc and the like. As the cationic organic substance, a quaternary ammonium salt, a polyamine, an alkylamine and the like are preferable. The amount of the additive is 20% by weight of the pigment.
The following is good.

As the binder used in the present invention, one or more of water-soluble polymers can be freely selected and used. For example, polyvinyl alcohol or its modified product, starch or its modified product, gelatin or its modified product, casein or its modified product, gum arabic, cellulose derivatives such as carboxymethylcellulose, conjugated diene copolymer latex such as SBR latex, functional group Modified polymer latex, vinyl-based copolymer latex such as ethylene-vinyl acetate copolymer, polyvinylpyrrolidone, maleic anhydride or a copolymer thereof, and acrylate copolymer are preferred.

The mixing ratio of alumina hydrate and the binder and the mixing ratio of silica and the binder are 5: 1 to 20:
One can be arbitrarily selected from among 1. If the amount of the binder is less than the lower limit of the above range, the mechanical strength of the ink receiving layer is insufficient, cracks and powder fall easily occur, and if it is more than the upper limit of the above range, the pore volume is reduced. The absorbency of the ink may decrease.

For the alumina hydrate and the binder, if necessary, a pigment dispersant, a thickener, a pH adjuster, a lubricant, a fluidity modifier, a surfactant, an antifoaming agent, a waterproofing agent, a foam inhibitor A releasing agent, a foaming agent, a penetrating agent, a coloring dye, a fluorescent whitening agent, an ultraviolet absorber, an antioxidant, a preservative, and an antibacterial agent can be added as necessary. The water-proofing agent can be freely selected from known materials such as halogenated quaternary ammonium salts and quaternary ammonium salt polymers.

The base material used for forming the ink-receiving layer in the present invention includes papers such as properly sized paper, non-sized paper, resin-coated paper using polyethylene and the like, and thermoplastic films. Any suitable sheet-like substance can be used, and there is no particular limitation. For thermoplastic films, polyester, polystyrene, polyvinyl chloride,
It is also possible to use a transparent film of polymethyl methacrylate, cellulose acetate, polyethylene, polycarbonate, or the like, or an opaque sheet filled with pigments or finely foamed.

In the method of forming a recording medium of the present invention, a coating liquid containing alumina hydrate and a binder, and a coating liquid containing silica and a binder are coated on a substrate and dried to form an ink receiving layer. Can be formed. Further, post-drying, cutting, packing, inspection, and the like can be performed as necessary.

For example, the following method can be used for forming the ink receiving layer having a two-layer structure. For example, a method for forming a porous upper layer composed of silica and a binder is a method of performing simultaneous multilayer coating with a dispersion containing an alumina hydrate and a binder, and a dispersion containing an alumina hydrate and a binder using a plurality of coater heads. A method of applying and drying a coating liquid containing silica and a binder on a substrate coated with
A method of applying a coating liquid containing alumina hydrate and a binder on a substrate, drying the coating liquid containing silica on a porous layer composed of alumina hydrate and a binder, and drying the coating liquid. it can.

In the present invention, a method for forming an ink receiving layer having pores inside a porous lower layer containing alumina hydrate and a binder and communicating with the voids and having pores penetrating to the surface of the ink receiving layer is particularly preferred. Although there is no limitation,
One or more of the following four methods described in JP-A-664 can be selected and used. (1) A dispersion containing alumina hydrate and a binder is applied to a substrate, and drying conditions are controlled to dry the vicinity of the surface first to form a film without voids and then remain inside. A method of forming an ink receiving layer by drying a solvent component. (2) Agglomerates of alumina hydrate are formed, and the above-mentioned aggregates of alumina hydrate and a material for increasing the surface tension of a dispersion containing the same or a material having a strong film-forming power are added and coated and dried. To obtain an ink receiving layer. (3) A solvent having a boiling point higher than that of the dispersion medium of the dispersion is added to the dispersion of the alumina hydrate, and then applied to a substrate, and the vicinity of the surface is dried at a temperature equal to or lower than the boiling point of the high boiling point solvent. A dense film is formed, and then the solvent remaining inside is gradually dried. Alternatively, a material for increasing the surface tension of the dispersion or a material having a strong film-forming power is added to the dispersion,
How to dry. (4) A method in which a dispersion containing an aggregate of alumina hydrate and a binder is applied to a substrate, and then a dispersion containing a non-aggregated particulate alumina hydrate and a binder is applied and dried.

As a method for dispersing a dispersion containing alumina hydrate and a binder or a dispersion containing silica and a binder, any of the methods generally used for dispersion can be used. As a device to be used, a gentle mixer such as a homomixer or a rotary blade is more preferable than a grinding type disperser such as a ball mill or a sand mill. The shear stress varies depending on the viscosity, amount and volume of the dispersion,
A range of 100.0 N / m ² is preferred. If a strong shear force exceeding the above range is applied, the dispersion may gel or the crystal structure may change. Further, 0.1 to 20.0 N /
The range of m ² is more preferable because it can prevent the pore structure from being broken and the pore volume from being reduced.

The dispersion time varies depending on the amount of the dispersion, the size of the container, the temperature of the dispersion, etc., but is preferably 30 hours or less from the viewpoint of preventing a change in the crystal structure. Can be controlled within the above range. During the dispersion treatment, the temperature of the dispersion may be kept within a certain range by cooling or keeping the temperature. The preferred temperature range varies depending on the dispersion treatment method, material, and viscosity, but is 10 to 100 ° C.
It is. If it is lower than the lower limit of the above range, the dispersion treatment may be insufficient or aggregation may occur. If it is higher than the upper limit of the above range, gelation may occur or the crystal structure may change to amorphous.

In the present invention, as a method of applying the alumina hydrate dispersion when the ink receiving layer is provided, generally used blade coaters, air knife coaters, roll coaters, brush coaters, curtain coaters, bar coaters, and the like can be used. A gravure coater, a spray device or the like can be used.

The coating amount of the dispersion is preferably 0.5 to 60 g / m ^{2 in} terms of dry solid content of the whole ink receiving layer, and within this range, the ink absorption amount and the ink absorption speed can be satisfied. . In addition, the fixing speed and the fixing amount of the printed dye can be satisfied, the bleeding of the printed portion is small, and the water resistance is good. More preferably 5 to 5 in terms of dry solids
It is in the range of 45 g / m ² , and cracks and curls can be prevented within this range. Further, the coating amount of the porous upper layer containing silica and the binder is 0.5 to 20 g /
m ² is preferred. Within this range, the ink absorption speed is high even in high-speed printing using pigment ink, dye ink, a mixed system of pigment ink and dye ink, and combined ink, and the fixability and friction resistance of the pigment ink are good. become. A more preferable range is 0.5 to 10 g / m ² , and within this range, a large number of gradations can be obtained in printing using three or more types of inks of different shades. If the coating amount is larger than the upper limit of the above range, cracks are likely to occur and the ink absorption speed is slowed, and if the coating amount is smaller than the lower limit of the above range, the ink absorption amount is insufficient, and the dye The adsorption rate index may also be reduced.
If necessary, it is also possible to improve the surface smoothness of the ink receiving layer by using a calender roll or the like after coating.

The ink used in the image forming method of the present invention mainly contains a colorant (dye or pigment), a water-soluble organic solvent and water. As the dye, for example, a direct dye, an acid dye, a basic dye, a reactive dye, a water-soluble dye represented by an edible dye, and the like, are preferable, and in combination with the above-described recording medium, fixability, coloring, and sharpness are preferable. Any dye may be used as long as it provides an image satisfying the required performance, stability, light fastness and the like. As the pigment, for example, organic substances such as carbon black, metal fine particles, metal oxides, and metal compounds can be used. As the pigment colorant, either a self-dispersion type pigment or a pigment colorant using a dispersant such as a surfactant can be used.

The water-soluble dye is generally used by dissolving it in water or a solvent comprising water and an organic solvent. These solvent components are preferably a mixture of water and various water-soluble organic solvents. Is used, but it is preferable to adjust the water content in the ink to fall within a range of 20 to 90% by weight.

Examples of the water-soluble organic solvent include alkyl alcohols having 1 to 4 carbon atoms such as methyl alcohol; amides such as dimethylformamide; ketones or ketone alcohols such as acetone; ethers such as tetrahydrofuran; Examples thereof include polyalkylene glycols such as polyethylene glycol, alkylene glycols having an alkylene group having 2 to 6 carbon atoms such as ethylene glycol, and lower alkyl ethers of polyhydric alcohols such as glycerin and ethylene glycol methyl ether. .

Among these many water-soluble organic solvents,
Polyhydric alcohols such as diethylene glycol, and lower alkyl ethers of polyhydric alcohols such as triethylene glycol monomethyl ether and triethylene glycol monoethyl ether are preferred. Polyhydric alcohols are particularly preferable because they have a large effect as a lubricant for preventing nozzle clogging caused by evaporation of water in the ink and precipitation of a water-soluble dye.

A solubilizing agent can be added to the ink. Typical solubilizers are nitrogen-containing heterocyclic ketones, the purpose of which is to significantly improve the solubility of a water-soluble dye in a solvent. For example, N-methyl-2-pyrrolidone and 1,3-dimethyl-2-imidazolidinone are preferably used. In order to further improve the properties, a viscosity modifier, a surfactant, a surface tension modifier, p
Additives such as an H adjuster and a specific resistance adjuster can be used.

The method of performing recording by applying the ink to the recording medium is an ink jet recording method, and the recording method can effectively remove ink from nozzles and apply ink to the recording medium. Any method may be used. In particular, according to the method described in Japanese Patent Application Laid-Open No. 54-59936, an ink jet method in which ink subjected to the action of thermal energy causes a sudden volume change, and the ink is ejected from a nozzle by the action force due to this state change Can be used effectively.

For printing on the recording medium of the present invention, an ink using a dye as a coloring material, an ink using a pigment as a coloring material, an ink in which a pigment coloring material and a dye coloring material are mixed, an ink containing a pigment coloring material and a dye This is an ink containing both coloring materials. As a printing method, in addition to the conventional method, a method of printing inks with different types of color materials such as pigments and dyes in the same pixel, and printing three or more types of dark and light inks with different color material densities in the same pixel And a method of printing inks having different color tones in the same pixel.

[0064]

[Molar ratio of monomer (former / latter) = 2/8]

3 parts Monoethanolamine 1 part Diethylene glycol 5 parts Ion-exchanged water 76 parts (E: Ink composition 1 (dye standard concentration ink)) Dye 3 parts Diethylene glycol 5 parts Polyethylene glycol 10 parts Water 82 parts (F: Ink composition 2 (Dye light color Ink 1)) Dye 1 part Diethylene glycol 5 parts Polyethylene glycol 10 parts Water 84 parts (G: Ink composition 3 (dye light color ink 2)) Dye 0.6 part Diethylene glycol 5 parts Polyethylene glycol 10 parts Water 84.4 parts (H: Ink composition 4 (Pigment standard density ink)) Pigment dispersion 33 parts Diethylene glycol 4 parts Ion exchange water 63 parts (I: Ink composition 5 (Pigment light color ink 1)) Pigment dispersion 11 parts Diethylene glycol 4 parts Ion exchange water 85 parts ( J: Ink composition 6 (Pigment light color ink 2)) Pigment dispersion 6.6 parts Diethylene glycol 4 parts Deionized water 89.4 parts (K: Ink composition 7 (dye / pigment mixed standard concentration ink)) Dye 1.5 parts Pigment dispersion 16.5 parts Diethylene glycol 4 0.5 parts Polyethylene glycol 5 parts Water 72.5 parts (L: ink composition 8 (dye / pigment mixed light color ink 1)) Dye 0.5 part Pigment dispersion 5.5 parts Diethylene glycol 4.5 parts Polyethylene glycol 5 parts Water 84.5 parts (M: ink composition 9 (dye / pigment mixed light color ink 2)) Dye 0.3 part Pigment dispersion 3.3 parts Diethylene glycol 4.5 parts Polyethylene glycol 5 parts Water 86.9 parts (N: ink Composition 10 (dye / dye mixture standard concentration ink)) Black dye 2.4 parts Cyan dye 0.6 parts Diethylene glycol 5 parts Polyester Tylene glycol 10 parts Water 82 parts (O: Ink composition 11 (dye / dye mixed light color ink 1)) Black dye 0.8 parts Cyan dye 0.2 parts Diethylene glycol 5 parts Polyethylene glycol 10 parts Water 84 parts (P: Ink composition 12 (dye / dye mixed light color ink 2)) Black dye 0.5 part Cyan dye 0.1 part Diethylene glycol 5 parts Polyethylene glycol 10 parts Water 84.4 parts (A: ink absorption) Ink compositions 1, 4, 7, Using four types of inks, 1 and 4, 24 × 24 / mm ² for each ink using the recording apparatus described above.
Performs multi-color solid printing from single-color dot printing (printing amount 100%) to four-color printing (printing amount 400%), and prints the dry state of ink on the surface of the recording medium due to ink absorption immediately after printing to the recording unit. I checked it with my finger. When the ink amount is 400%, the ink does not adhere to the finger, ◎: when the ink amount is 300%, the ink does not adhere to the finger, ○: When the ink amount is 100%, the ink does not adhere to the finger, Δ: Is marked as x if attached to the finger.

(B: Roundness) Ink Compositions 1, 4, 7, 1
When 4 in combination, four of the ink using, 1 mm ² per 24 × using the recording device for each of the ink
The single dot printing of 24 dots (printing amount 100%) was performed, and the roundness of the printing dots of each color was determined by the same method as described in JP-A-61-3777. The roundness becomes 1.0 if the dot is a perfect circle, and becomes larger as the jaggedness around the dot increases. The roundness of the image was compared with the roundness of the dot of each shape, and the roundness of 1.5 or less was determined to be good. When the roundness of each color was good when the printing ink amount was 300%, the roundness was good, when the roundness was good when the ink amount was 100%, and when the roundness was poor under the same conditions, it was rated x. (C: Optical density) Ink compositions 1, 4, 7, 1 and 4 used together,
Using the four types of inks, for each ink, the printing ink amount of each color was set to 100
The optical density of an image solid printed in% (monochrome) was evaluated using a Macbeth reflection densitometer RD-918. When the ink receiving layer was formed on a transparent substrate, the measurement was performed by placing an electrophotographic paper (manufactured by EW-500 Canon) on the back side of the recording medium. (D: Color of mixed color portion) Using four types of inks of ink compositions 1, 4, 7, 1 and 4, and using each of the above-described devices for each ink, orange (Y + M) and green (Y +
C), purple (M + C), and black (Y + M + C) were printed by changing the order of the printing ink amount of each color at 100%. The difference in tint when the printing order was changed was visually observed on the front surface and the back surface of the ink receiving layer. If there was no difference in color between the three colors in the mixed color portion, it was evaluated as ○, if there was no difference in color between 1 and 2 colors, and if there was a difference in color between each color, it was evaluated as ×. (E: Solid uniformity, bleeding, bleeding, beading, cissing) Using four kinds of inks of ink compositions 1, 4, 7, 1 and 4, and using the above apparatus, the printing ink amount was 100% (monochromatic). ) To 400% (4 colors), and solid printing was performed, and the uniformity, bleeding, bleeding, beading, and cissing were visually evaluated. Printing ink amount 300
% If not generated at 100%, and Δ if not generated at 100% of the ink amount, and x if generated under the same conditions.

In the present invention, bleeding, bleeding, beading, and cissing are defined as follows. The bleeding refers to a phenomenon in which, when solid printing is performed on a fixed area, a portion colored with a dye becomes wider (larger) than the printing area.
Bleeding refers to a phenomenon in which bleeding occurs at the boundary of a solid-color-printed portion, and the dye is mixed without being fixed. Beading is a phenomenon that occurs because ink droplets printed on a recording medium aggregate into large droplets in a process such as absorption. It is visually recognized as color unevenness of the size of a bead ball. Repelling is a solid printed portion that is not colored with a dye. (F: Color change due to gradation number and density) Ink composition 1
Using the three types of dark and light ink sets 3, 4 to 6, and 7 to 9, each ink set was printed on the recording medium at the ratios shown in Table 3 using the recording apparatus. This is a density change of about 60 steps. When the difference in optical density could be determined by visually observing each printed portion, it was determined that gradation was obtained. The number of gradations obtained by this method was counted. In addition, when the color difference of each printed portion was not visually observed, it was evaluated as ○, when a color difference of less than three locations was observed, and when a color change of more than three locations was observed, it was rated X. (G: Number of gradations in mixed ink) Ink compositions 1-3, 10
Using the two types of dark and light ink sets in combination, the recording apparatus was used to print both ink sets at the ratios shown in Table 3. In some cases, the optical density of black to which cyan is added is different from that of pure black when the print density is low. The printed portions of the same ink set combination (same density) of both inks were visually observed and compared, and the number of which could be determined as having a difference in density was measured. If the number of discrimination was 10 or more, it was evaluated as ○. If the number of discrimination was 5 or more, it was evaluated as Δ. If it was 4 or less, it was evaluated as x. (H: Fixing property of coloring material) Using four kinds of inks of ink compositions 1, 4, 7, 1 and 4, and using the above-mentioned recording apparatus, for each ink, the printing ink amount of each color was 10%.
After the solid printed portion at 0% (single color) was dried, it was rubbed with a finger and examined for peeling of the coloring material. If there was no peeling of the coloring material, it was evaluated as 、, and if peeling of the coloring material occurred, it was evaluated as ×. (Re: Curl after printing) Recording medium is 297 × 210 mm
, And using the above-mentioned apparatus, using four kinds of inks of ink compositions 1, 4, 7, 1 and 4,
For each of the inks, solid printing was performed using the recording apparatus at a print ink amount of each color of 100% (single color). It was left on a flat table and the amount of warpage was measured with a height gauge. ○: 3mm or less, 3mm or less
x was defined as m or more. (Nu: tack after printing) The recording medium is 297 x 210 m
m, and using the above-mentioned apparatus, using four types of inks of ink compositions 1, 4, 7, 1 and 4,
For each of the inks, solid printing was performed using the recording apparatus at a print ink amount of each color of 100% (single color). When the printed surface of the recording medium was touched with a finger and did not adhere, it was evaluated as ○, and when adhered, evaluated as ×. (R: transport damage after printing) The recording medium is 297 × 210 m
The sheet was cut into a size of m, and 10 sheets were stacked and transported in order by an ink jet printer (BJC430J, manufactured by Canon Inc.), and surface scratches were observed. A sample having a length of 1 mm or more and having no scratches was evaluated as ○, a sample having no damage of 5 mm or more was evaluated as Δ, and a sample having a scratch of 5 mm or more was evaluated as ×. (2) Transparency The haze of a sample in which alumina hydrate was applied to a transparent PET film was measured with a haze meter (NDH-1001DP, manufactured by Nippon Denshoku Co., Ltd.) according to JIS K-1705. (3) Crack The sample was cut into a size of 297 × 210 mm, and the length of the crack was visually measured. 1 mm or more without cracks ○, 5 mm or more without cracks △,
Those with cracks of 5 mm or more were rated as x. (4) Curl The sample was cut into a size of 297 × 210 mm, left on a flat table, and the amount of warpage was measured with a height gauge. If the warp is 1 mm or less, ○, 3 mm or less, Δ, 3 m
x was defined as m or more. (5) Tack The surface of the recording medium was evaluated as ○ when the surface of the recording medium was touched with a finger and did not adhere, and as X when adhered. (6) Pore structure The maximum peak radius was determined by measuring the pore radius distribution by a mercury intrusion method. The measurement device was Autopore III 9420 (Micromerit
ics). Mercury has a surface tension of 485.0 dyn
e / cm, contact angle 135 °, mercury pressure 0-33
It was measured at 000 psia.

The pore volume and BET specific surface area were measured by using a nitrogen adsorption / desorption method. The measuring apparatus used was Autosorb 1 (manufactured by Kantachrome). (7) Void Radius / Volume Ratio The recording medium is cut with a microtome to make the ink receiving layer thin, and the cross section of the ink receiving layer is magnified 200,000 times by a transmission electron microscope (H-600, manufactured by Hitachi, Ltd.). As described above, the radius of the void inside the receiving layer was determined. Further, the area of the void was obtained from the same photograph, and the ratio to the total area of the photograph was obtained to derive the volume ratio (%). (8) Water absorption / in-plane diffusion index The recording medium on which the ink receiving layer is formed has a length of one side of 1
Cut into 00 mm squares. Ion-exchanged water is dripped little by little into the center, and each time it is spread evenly with a spatula and absorbed. This operation is repeated until the ink overflows.
Ion exchange water remaining on the sample surface is wiped off with a cloth or the like. The amount of water absorption is determined from the weight difference of the recording medium before and after the absorption of ion-exchanged water. Further, the absorption amount at one point of the recording medium is determined by the following method, and the absorption amount at one point of the recording medium / the water absorption amount of the recording medium is determined to be the in-plane diffusion coefficient. The recording medium on which the ink receiving layer is formed is cut into a square having a length of 100 mm on one side, and ion-exchanged water is dropped and absorbed at one point at the center of the recording medium. It is necessary to prevent the ion-exchanged water dropped at this time from spreading on the surface of the ink receiving layer before being absorbed at the dropping point. As in the measurement of the ink absorption amount, this operation is repeated until the overflow occurs, and the absorption amount at one point of the recording medium is obtained from the weight difference of the recording medium before and after the absorption of the ion-exchanged water.

[Examples 1 to 3] A porous alumina hydrate layer having a thickness of 30 μm was formed by the same method using the same material as in Examples 1, 16 and 18 of JP-A-9-66664. Recording media A to C were obtained. Polyvinyl alcohol (G
H-23, manufactured by Nippon Synthetic Chemical Co., Ltd.) was dispersed in ion-exchanged water to obtain a dispersion having a solid content of 10% by weight. The dispersion and colloidal silica (Snowtex OL, manufactured by Nissan Chemical Industries, Ltd.)
Were mixed at a solid content mixing ratio of 1: 3, and stirred at 2000 rpm for 5 minutes using a homomixer (manufactured by Tokushu Kika Co., Ltd.). This dispersion is applied to the recording media A to C
Was applied and dried to form a porous silica layer having a thickness of 10 μm. The physical properties of the recording medium were measured by the above methods. Table 1 shows the measurement results.

[Embodiment 4] Japanese Patent Application No. 10-174778
30 μm in thickness using the same material as in Example 17
recording medium D on which a porous alumina hydrate layer of m is formed
I got

That is, aluminum dodexide was produced according to the method described in US Pat. No. 4,242,271. The obtained aluminum dodoxide, ion-exchanged water, and orthosilicic acid were mixed. This mixed solution was placed in a reaction vessel and the aluminum dodoxide was hydrolyzed while stirring. The hydrolysis conditions and the mixing ratios of aluminum dodecoxide and orthosilicic acid are as follows. In addition, the same weight as aluminum dodexide in ion exchange water was used. Hydrolysis temperature: 110 ° C. Hydrolysis time: 30 minutes Mixing ratio: 0.85 (mixing ratio: amount of silicic acid added to 100 parts by weight of alkoxide: parts by weight) The obtained alumina hydrate suspension was heated at the inlet temperature. It was spray-dried at 280 ° C. to obtain a silica-containing alumina hydrate powder. The crystal structure of the alumina hydrate was boehmite, and the particle shape was flat. The physical properties are as follows. Silica content: 0.1% by weight Average particle diameter: 30.2 nm Aspect ratio: 6.0 Crystallinity: 65 Polyvinyl alcohol (manufactured by Nippon Synthetic Chemical Industry Co., Ltd.)
Gohsenol NH18 (trade name) was dissolved and dispersed in ion-exchanged water to obtain a solution having a solid content of 10% by weight. The silica-containing alumina hydrate powder obtained by the above operation is similarly dispersed in ion-exchanged water to prepare a silica-containing alumina dispersion having a solid content concentration of 15% by weight. (Kishida Chemical) is added in an amount that is 1/150 of the solid content of the silica-containing alumina hydrate dispersion,
With a homomixer (manufactured by Tokushu Kika) at 8000 rpm,
Stir for 30 minutes. The obtained dispersion and the previously prepared polyvinyl alcohol solution were weighed such that the solid content of the polyvinyl alcohol and the silica-containing alumina hydrate became 1:10 by weight mixing ratio, and the mixture was homomixed (special). The mixture was stirred at 8000 rpm for 30 minutes to obtain a mixed dispersion.

This mixed dispersion was die-coated on a 100 μm thick transparent polyethylene terephthalate (PET) film (Lumirror, trade name, manufactured by Toray Industries, Inc.). The PET film coated with the mixed dispersion was heated in an oven (manufactured by Yamato Scientific Co., Ltd.) at a temperature of 100 ° C. for 5 minutes to rapidly dry the vicinity of the surface. In addition, 120 ℃ in the same oven
The resultant was dried while increasing the temperature until an ink receiving layer having a thickness of 30 μm was formed on the PET film. Thus, a recording medium D was obtained.

On the ink receiving layer of the recording medium D, the same dispersion liquid comprising silica and binder as in Example 1 was applied and dried in the same manner as in Example 1 to obtain a film having a thickness of 10%.
A recording medium having a two-layered ink-receiving layer by forming a μm silica layer was obtained. The physical properties of the obtained recording media were measured by the above methods. Table 1 shows the measurement results.
Shown in

Example 5 Colloidal silica (Snowtex-YL, manufactured by Nissan Chemical) and ultrafine colloidal silica as a binder (Snowtex-UP, manufactured by Nissan Chemical) were mixed at a solids mixing ratio of 1: 1. The dispersion treatment was performed in the same manner as in Example 1 to obtain a dispersion. This dispersion was applied onto a recording medium A on which a porous alumina hydrate layer having a thickness of 30 μm was formed in the same manner as in Example 1 and dried to form a film having a thickness of 10 μm.
A μm porous silica layer was formed. The physical properties of the recording medium were measured by the above methods. Table 2 shows the measurement results. Example 6 Gel-type silica (P-78A, Mizusawa Chemical) was dispersed in ion-exchanged water to obtain a dispersion having a solid content of 10% by weight. This dispersion and the same polyvinyl alcohol dispersion as in Example 1 were mixed at a solid content mixing ratio of 3: 1 and subjected to dispersion treatment in the same manner as in Example 1 to obtain a mixed dispersion.

This dispersion was prepared in the same manner as in Example 1 with a thickness of 30 μm.
Was coated and dried on the recording medium A on which the porous alumina hydrate layer was formed to form a porous silica layer having a thickness of 10 μm. The physical properties of the recording medium were measured by the above methods. Table 2 shows the measurement results.

[Example 7] Precipitated silica (P-8)
02Y, Mizusawa Chemical) was dispersed in ion-exchanged water to obtain a dispersion having a solid content of 10% by weight. This dispersion and the same polyvinyl alcohol dispersion as in Example 1 were mixed at a solids mixing ratio of 3: 1.
And a dispersion treatment was performed in the same manner as in Example 1 to obtain a mixed dispersion.

This dispersion was treated with the same thickness of 30 μm as in Example 1.
Was coated and dried on the recording medium A on which the porous alumina hydrate layer was formed to form a porous silica layer having a thickness of 10 μm. The physical properties of the recording medium were measured by the above methods. Table 2 shows the measurement results.

Example 8 Synthetic amorphous silica having an average particle size of 2 μm (trade name: NipsilH, manufactured by Nippon Silica Industry Co., Ltd.)
After using D) for dispersion by a sand grinder, ultrasonic waves were applied, and the dispersion operation of the sand grinder and the ultrasonic waves was repeated until the average particle diameter became 40 nm, thereby preparing an 8% aqueous dispersion.

This dispersion and the same polyvinyl alcohol dispersion as in Example 1 were mixed at a solids mixing ratio of 3: 1 and subjected to dispersion treatment in the same manner as in Example 1 to obtain a mixed dispersion. This dispersion was applied and dried on a recording medium A on which a porous alumina hydrate layer having a thickness of 30 μm was formed as in Example 1, to form a porous silica layer having a thickness of 10 μm. The physical properties of the recording medium were measured by the above methods. Table 2 shows the measurement results.

[0079]

[Table 1]

[0080]

[Table 2]

[0081]

[Table 3]

[0082]

[Table 4]

[0083]

[Table 5]

[0084]

By using the recording medium and the image forming method of the present invention, the following excellent effects can be obtained. That is, even when (1) printing with a dye-mixed ink, printing with a pigment-based ink, and combined printing of a pigment ink and a dye ink are performed at a high speed, the ink absorption is fast and the image density can be increased. The printed image has a clear color tone irrespective of the type of ink, and no beading occurs. (2) In printing using three or more types of dark and light inks having different densities, a large number of gradations can be obtained, and there is no color change due to the density. (3) The fixation of the coloring material can be improved regardless of the type of the ink. Furthermore, the roundness of the printed dots can be improved regardless of the type of ink. For this reason, the color tone does not change depending on the density of the printed image even in the mixed color portion. (4) Color unevenness and fixation unevenness in a solid printed portion do not occur even when printing is performed using a pigment ink and a dye ink in combination or printing using a mixed ink of a pigment and a dye. (5) The transparency of the ink receiving layer can be improved.
Further, it is possible to prevent the surface of the ink receiving layer from being damaged and tacky. Further, cracks are less likely to occur in the ink receiving layer. (6) For example, as in a light and dark ink containing a black color material and a light and dark ink containing a mixed color material of a black color material and a blue color material,
The number of tones that can be visually observed can be increased by a printing method using color materials having different color tones. Curling, tacking, and transport damage after printing hardly occur.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing the structure of an ink receiving layer of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 recording medium 2 base material 3 ink receiving layer 4 porous lower layer composed of alumina hydrate and binder 5 porous upper layer composed of silica and binder 6 internal cavity 7 pore

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Hiroshi Tomioka 3-30-2 Shimomaruko, Ota-ku, Tokyo F-term in Canon Inc. (reference) 2H086 BA16 BA32 BA33 BA45

Claims (14)

[Claims] 1. A recording medium having a two-layered ink receiving layer on a substrate, wherein a lower layer is a porous layer containing alumina hydrate having a boehmite structure and a binder, and an upper layer formed thereon. Is a porous layer containing silica and a binder, wherein the lower layer has voids inside the layer, and the voids communicate with the surface of the ink receiving layer through pores having a smaller radius. . 2. The ink receiving layer according to claim 1, wherein said ink receiving layer has a radius of 2.0 to 20.
2. The recording medium according to claim 1, which has a maximum peak in a range of 0 nm. 3. The ink receiving layer has a radius of 6.0-20.
2. The recording medium according to claim 1, which has a maximum peak in a range of 0 nm. 4. The ink receiving layer having a pore volume of 0.4 to 0.4.
2. The recording medium according to claim 1, wherein the recording medium is in a range of 1.0 ml / g. 5. The ink receiving layer having a pore volume of 0.4 to 0.4.
2. The recording medium according to claim 1, wherein the content is in the range of 0.6 ml / g. 6. The recording medium according to claim 1, wherein the pore volume with a pore radius of 2.0 to 20.0 nm is 80% or more of the total pore volume. 7. The ink receiving layer having a water absorption of 0.4 to 0.4.
2. The recording medium according to claim 1, wherein the recording medium is in a range of 1.0 ml / g. 8. The ink receiving layer having an in-plane diffusion coefficient of 0.8.
2. The recording medium according to claim 1, wherein the recording medium is in the range of 7 to 1.0. 9. An image forming method for forming an image by applying ink to a recording medium, wherein the recording medium is the recording medium according to any one of claims 1 to 8. Image forming method. 10. The image forming method according to claim 9, wherein an ink jet system is used as the system for applying the ink. 11. The image forming method according to claim 10, wherein said ink jet system is a system in which thermal energy is applied to ink to eject ink droplets. 12. A method for discharging ink droplets,
12. The image forming method according to claim 11, wherein printing is performed using three or more types of inks having different color material densities. 13. The method of ejecting ink droplets,
12. The image forming method according to claim 11, wherein printing is performed by using both an ink containing a pigment and an ink containing a dye as color materials. 14. A method for discharging ink droplets,
12. The image forming method according to claim 11, wherein printing is performed using a plurality of inks having different color tones.