JP2003220754A - Ink-jet recording medium, ink-jet image forming method using the same, and ink-jet image - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink-jet recording medium which is excellent in writing properties, fingerprint adhesion resistance, and glossiness and controls the occurrence of cockling and film peeling, to provide an ink-jet image forming method using the medium, and an ink-jet image. <P>SOLUTION: In the ink-jet recording medium, at least one ink absorbing layer is formed on a support, and its surface layer contains a thermoplastic resin. The surface layer is characteristically porous after being passed through a treatment process in which at least part of the resin is melted or dissolved after printing. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inkjet recording medium, an inkjet image forming method using the same, and an inkjet image.

[0002]

2. Description of the Related Art In recent years, the progress of ink jet technology has been remarkable, and printer technology, ink technology and dedicated recording medium technology have come to be called photographic image quality.
With the improvement of image quality, the preservability of inkjet images has been compared with that of conventional silver salt photographs, and in many dye inks, the deterioration of inkjet images due to migration of colorants such as poor water resistance and bleeding resistance. It is also pointed out that the deterioration due to the chemical reaction of the coloring agent such as the weakness of light resistance and oxidation resistance gas resistance.

To improve the storability of dye ink images,
Many suggestions have been made. As an inkjet recording medium, for example, in Japanese Examined Patent Publication No. 31673/1990, a layer made of thermoplastic organic polymer particles is provided on the outermost layer of the recording medium,
After image recording, the thermoplastic organic polymer particles are melted to form a film, and as a result, a polymer protective film is formed,
Achieves improved water resistance and weather resistance and imparts gloss to images.

Further, in a conventional recording medium having a layer comprising thermoplastic organic polymer particles as the outermost layer, gloss is imparted by fixing treatment, but the gloss is insufficient as compared with silver salt photography, Further, the ink absorption rate is at an insufficient level, and is particularly remarkable when a pigment ink is used. Furthermore, when a layer made of thermoplastic organic polymer particles is provided on the surface layer, problems such as inability to write on the formed image, fingerprints being attached and being easily noticeable, and melting of the surface layer by heat treatment In addition, since the solvent of the printed ink is enclosed in the ink jet recording medium, swelling due to steam at the time of heating occurs, which easily causes film breakage or film peeling.

Various investigations have been made on the film destruction due to the evaporation of the ink solvent when a layer made of thermoplastic organic polymer particles is provided on the surface layer, but an effective means has not been found yet. is the current situation. For example, in Japanese Unexamined Patent Publication No. 11-291611, in a method of applying heat fixing treatment after printing on an ink jet recording medium containing a thermoplastic resin on the surface layer, the heat treatment process is controlled so that the ink solvent reaches its boiling point. , A method of losing the liquid permeability of the surface layer has been proposed, but no mention is made of the correspondence with respect to the writing property or the fingerprint adhesion property.

Further, in Japanese Patent Laid-Open No. 2000-127609,
Regarding a recording sheet containing a thermoplastic resin in the surface layer, a method has been proposed in which the Gurley air permeability is regulated and the solvent vapor is scattered during the heat treatment. However, since the absorbent paper support is used, the occurrence of cockling has become a major issue.

Further, Japanese Patent Laid-Open No. 2000-203151 discloses that
A means for increasing the particle size of the thermoplastic organic polymer particles to be used has been proposed, but if the thermoplastic organic polymer particles are increased in size, it takes a long time for fixing, resulting in poor suitability for high-speed image formation. There is a problem that the glossiness of the formed image is reduced.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object thereof is to have excellent writability, anti-fingerprint adhesion, glossiness, cockling, and film peeling. An object of the present invention is to provide a reduced inkjet recording medium, an inkjet image forming method using the same, and an inkjet image.

[0009]

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

1. In an inkjet recording medium having at least one ink absorbing layer on a support and a surface layer containing a thermoplastic resin, after printing, after passing through a treatment step in which at least a part of the thermoplastic resin is melted or dissolved. The ink jet recording medium, wherein the surface layer of the is a porous layer.

2. 2. The inkjet recording medium as described in 1 above, wherein the surface layer contains a thermoplastic resin and an inorganic pigment.

3. 3. The ink jet recording medium as described in 1 or 2 above, wherein the support is a non-absorbent support.

4. The ink jet recording medium according to any one of items 1 to 3, wherein the ink absorption capacity of the white background portion after passing through the treatment step is 5 ml / m ² or more.

5. The ink absorption capacity of the white background portion after passing through the treatment step is 50% or more of the ink absorption capacity of the white background portion before passing through the treatment step.
Item 5. The inkjet recording medium according to any one of items 4 to 4.

6. Any one of the above items 1 to 5, wherein the amount of ink transferred at a contact time of 40 msec according to the Bristow method of the white background portion after passing through the treatment step is 5 ml / m ² or more and 15 ml / m ² or less. 2. The inkjet recording medium according to item 1.

7. Performing inkjet image formation on the inkjet recording medium according to any one of items 1 to 6 by a step of printing with a pigment ink and a treatment step in which at least a part of the thermoplastic resin is melted or dissolved. An inkjet image forming method, comprising:

8. 7. The inkjet recording medium according to any one of items 1 to 6 above is formed by printing with a pigment ink and then performing a process of melting or dissolving at least a part of the thermoplastic resin. Inkjet image to do.

As a result of intensive investigations in view of the above problems, the present inventors have found that an ink jet recording medium having at least one ink absorbing layer on a support and a surface layer containing a thermoplastic resin (hereinafter, (Also simply referred to as a recording medium),
As a result of earnest studies, the surface layer after passing through the treatment step in which at least a part of the thermoplastic resin is melted or dissolved after printing has a porous structure, so that the image after treatment can be written with a pen, pencil, etc. Property can be imparted, fingerprints are less likely to adhere to the image, and when heating is used in the processing step, water and solvent in the ink are likely to evaporate and scatter, and a film due to volume expansion of these vapors. It has been found that the present invention has been achieved by finding that it becomes difficult to cause destruction.

Further, by incorporating a thermoplastic resin and an inorganic pigment in the surface layer, the ink jet recording medium is
It becomes easy to maintain the porosity even after the treatment, achieves high glossiness, and exhibits an excellent effect on high-speed printing suitability as the ink absorption speed increases.

On the other hand, as a method of evaporating the solvent in the ink, it is effective to provide a layer containing a thermoplastic resin on the absorptive support. However, the support itself absorbs the solvent and the like to cause cockling. As a result, the gloss is lowered and contact with the inkjet head at the time of printing is brought about, but it was found that these problems can be solved by using a non-absorbent support as the support.

In addition, in the present invention, the surface layer after passing through the treatment step has a porous structure, which means that the ink absorption capacity of the white background portion has a specific value as a characteristic value after treatment of the ink jet recording medium, It was found that this can be achieved by setting the ink absorption capacity of the white background portion before and after the treatment to a specific ratio, or by setting the ink transfer amount of the white background portion by the Bristow method at a contact time of 40 msec to a specific value. .

The details of the present invention will be described below. In the invention according to claim 1, in an inkjet recording medium having at least one ink absorbing layer on a support and a surface layer containing a thermoplastic resin, after printing, at least a part of the thermoplastic resin is melted or The surface layer after passing through the dissolving treatment step is characterized by being porous.

The term "the surface layer after passing through the treatment step" as used in the present invention means that the thermoplastic resin contained in the surface layer is subjected to a treatment step such as heat treatment, pressure treatment, or pressurization / heating. It is to maintain a porous structure in the surface layer portion by melting or dissolving at least a part by the treatment, and specifically, it means that the treatment step completely melts and does not form a uniform film. . In the present invention, whether or not the surface layer after passing through the treatment step is porous can be confirmed by directly observing the surface or cross section thereof with an electron microscope or the like.

In the present invention, a method for quantitatively determining that the surface layer after passing through the treatment step is porous is as follows:
The ink absorption capacity of the white background portion after passing through the treatment step of the invention according to claim 4 is 5 ml / m ² or more,
The ink absorption capacity of the white background portion after passing through the treatment step of the invention according to claim 5 is 50% or more of the ink absorption capacity of the white background portion before passing through the treatment step, or
The ink transfer amount of the white background portion after passing through the treatment step according to the invention according to the invention according to the Bristow method at a contact time of 40 msec is 5 ml / m ² or more and 15 ml / m ² or less. It is preferable that the ink jet recording medium is satisfactory.

In the invention according to claim 4, the ink absorption capacity of the white background portion after passing through the treatment step is preferably 5 ml / m ² or more, more preferably 5 to 40 ml / m ^2.
m ² and particularly preferably 15 to 30 ml / m ² .

The ink absorption capacity as used in the present invention can be determined by the following method, for a recording medium which has been subjected to a treatment process in an unprinted state of a certain area, at 25 ° C. and 50% RH for 24 hours or more. After controlling the humidity, this recording medium is immersed in pure water for 10 seconds. At this time, as the water is absorbed, the air in the voids of the recording medium adheres to the surface as bubbles to prevent water absorption. Therefore, the recording medium is appropriately vibrated to remove the bubbles. After 10 seconds, the recording medium was pulled up from the water, water on the surface was quickly removed with a water-absorbing material such as filter paper, and then the amount of ink absorbed (ml / ml
m ² ) can be calculated.

In the invention according to claim 5, the ink absorption capacity of the white background portion after passing through the processing step is preferably 50% or more of the ink absorption capacity of the white background portion before passing through the processing step, and more preferably. It is 50 to 98%, more preferably 70 to 98%. The ink absorption capacity of the recording medium before passing through the processing step can also be determined by the method described above.

Further, in the invention according to claim 6, the ink transfer amount of the white background portion after passing through the processing step by the Bristow method at a contact time of 40 msec is 5 ml / m ² or more and 15 m or more.
It is preferably 1 / m ² or less, more preferably 8
It is not less than ml / m ^{2 and not} more than 15 ml / m ² .

The Bristow method referred to in the present invention is a method for measuring the liquid absorption behavior of paper and paperboard in a short time. TAPPI paper pulp test method No. 51-
87 Liquid absorption test method for paper or paperboard (Bristow method)
The amount of ink transferred (ml / m ² ) at a contact time of 40 msec is measured. In the above measurement method, pure water (ion-exchanged water) is used for measurement,
In the present invention, less than 2% of a water-soluble dye may be contained in order to facilitate determination of the measurement area.

An example of a specific measuring method will be described below. As a method for measuring the amount of ink transfer, a recording medium that has been subjected to a treatment step in an unprinted state is left in an atmosphere of 25 ° C. and 50% RH for 12 hours or more, and then, for example, a liquid manufactured by Kumagai Riki Kogyo Co., Ltd. Bristow, a dynamic absorption tester
Measure with a tester type II (pressurized). The liquid used for measurement is a commercially available water-based inkjet ink (for example, magenta ink) in order to improve the measurement accuracy, and the area of the magenta dyed portion on the recording medium is measured after a specified contact time to determine the amount of ink transfer. Can be asked.

In the ink jet recording medium of the present invention, the method for making the surface layer porous after passing through the treatment step is not particularly limited, but, for example, the kind and the addition amount of the thermoplastic resin of the surface layer, the inorganic pigment Types and their addition amount,
Alternatively, as the treatment step, the heating temperature in the heat treatment,
Pressurizing force in pressure treatment or its method (for example,
It can be achieved by appropriately selecting or combining the roll fixing method and the belt fixing method).

First, the details of the ink jet recording medium of the present invention will be described. The ink jet recording medium of the present invention has at least one ink absorbing layer on the support, and the surface layer contains the thermoplastic resin.

Generally, the ink absorbing layer is roughly classified into a swelling type and a void type. As the swelling type, a water-soluble binder is used and, for example, gelatin, polyvinyl alcohol, polyvinylpyrrolidone, polyethylene oxide or the like is applied alone or in combination, and this is used as an ink absorbing layer.

As the void type, fine particles and a water-soluble binder are mixed and applied, and those having gloss are particularly preferable. As fine particles, alumina or silica is preferable, and silica having a particle diameter of 0.1 μm or less is particularly preferable. As the water-soluble binder, gelatin, polyvinyl alcohol, polyvinylpyrrolidone, polyethylene oxide and the like are preferably used alone or in combination.

Of the two types described above, a faster ink absorption speed of the recording medium is more suitable for continuous high-speed printing. From this point, the void type is particularly preferably used in the present invention. it can.

The void type ink absorbing layer will be described in more detail below. The void layer is mainly formed by soft aggregation of the hydrophilic binder and the inorganic fine particles. Conventionally, various methods for forming voids in a film are known,
For example, a method of applying a uniform coating solution containing two or more kinds of polymers on a support, and phase-separating these polymers in a drying process to form voids, solid fine particles and a hydrophilic or hydrophobic resin After coating the coating liquid containing it on a support and drying it, the ink jet recording paper is immersed in water or a liquid containing an appropriate organic solvent to dissolve solid fine particles to form voids, and foaming is performed during film formation. After applying a coating solution containing a compound having properties, a method of foaming this compound in the drying process to form voids in the coating, and a coating solution containing porous solid fine particles and a hydrophilic binder is applied on a support. Then, a method for forming voids in the porous fine particles or between the fine particles, solid fine particles and / or fine particle oil droplets and hydrophilic binder having a volume that is approximately equal to or more than that of the hydrophilic binder. The coating liquid containing coated on a support, and a method of forming an air gap between the solid particles are known. In the present invention, the void layer has an average particle size of 10
It is particularly preferable that it is formed by containing various inorganic solid fine particles of 0 nm or less.

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

The average particle size of the inorganic fine particles is a simple average value obtained by observing the particles themselves or particles appearing on the cross section or surface of the void layer with an electron microscope and measuring the particle size of 1,000 arbitrary particles. It is calculated as (number average). Here, the particle size of each particle is represented by the diameter assuming a circle equal to the projected area.

As the inorganic fine particles, solid fine particles selected from silica and alumina or alumina hydrate are preferably used.

As the silica which can be used in the present invention, silica synthesized by a usual wet method, colloidal silica, silica synthesized by a vapor phase method and the like are preferably used, and fine particles particularly preferably used in the present invention. As silica, colloidal silica or fine particle silica synthesized by a gas phase method is preferable, and among them, fine particle silica synthesized by a gas phase method is used not only for obtaining a high porosity but also for the purpose of immobilizing a dye. Coarse aggregates are less likely to be formed when added to the cationic polymer, which is preferable. Further, the alumina or alumina hydrate may be crystalline or amorphous, and those having any shape such as amorphous particles, spherical particles and acicular particles can be used.

The inorganic fine particles are preferably in a state in which the fine particle dispersion liquid before mixing with the cationic polymer is dispersed up to the primary particles.

The particle size of the inorganic fine particles is preferably 100 nm or less. For example, in the case of the gas phase method fine particle silica, the average particle diameter of the primary particles of the inorganic fine particles dispersed in the state of primary particles (particle diameter in the dispersion state before coating) is
It is preferably 100 nm or less, more preferably 4 to
50 nm, most preferably 4 to 20 nm.

As the most preferably used silica synthesized by the gas phase method having an average primary particle diameter of 4 to 20 nm, for example, Aerosil manufactured by Nippon Aerosil Co., Ltd. is commercially available. The fine particles of the vapor phase method silica can be relatively easily dispersed even in water by suction with a jet stream inductor mixer manufactured by Mitamura Riken Kogyo Co., Ltd.

In the present invention, a water-soluble binder can be used in the ink absorbing layer. Examples of the water-soluble binder that can be used in the present invention include polyvinyl alcohol, gelatin, polyethylene oxide, polyvinylpyrrolidone, polyacrylic acid, polyacrylamide, polyurethane, dextran, dextrin, color genin (κ, ι, λ, etc.), agar. , Pullulan, water-soluble polyvinyl butyral, hydroxyethyl cellulose, carboxymethyl cellulose and the like. It is also possible to use two or more of these water-soluble binders in combination.

The water-soluble binder preferably used in the present invention is polyvinyl alcohol.

The polyvinyl alcohol preferably used in the present invention includes, in addition to ordinary polyvinyl alcohol obtained by hydrolyzing polyvinyl acetate, polyvinyl alcohol having a cation-modified terminal and anion-modified polyvinyl alcohol having an anionic group. The modified polyvinyl alcohol of is also included.

The polyvinyl alcohol obtained by hydrolyzing vinyl acetate preferably has an average degree of polymerization of 1,000 or more, and particularly preferably an average degree of polymerization of 1,500 to.
Those of 5,000 are preferably used. Further, the saponification degree is preferably 70 to 100%, and 80 to 99.
5% is particularly preferable.

As the cation-modified polyvinyl alcohol, for example, primary to tertiary amino groups and quaternary ammonium groups as described in JP-A-61-10483 can be used as the main chain or side chain of the polyvinyl alcohol. The polyvinyl alcohol contained therein is obtained by saponifying a copolymer of an ethylenically unsaturated monomer having a cationic group and vinyl acetate.

Examples of the ethylenically unsaturated monomer having a cationic group include trimethyl- (2-acrylamido-2,2-dimethylethyl) ammonium chloride and trimethyl- (3-acrylamido-3,3-dimethylpropyl). ) Ammonium chloride, N-vinylimidazole, N-vinyl-2-methylimidazole, N
-(3-dimethylaminopropyl) methacrylamide,
Hydroxylethyltrimethylammonium chloride, trimethyl- (2-methacrylamidopropyl) ammonium chloride, N- (1,1-dimethyl-3-)
Examples include dimethylaminopropyl) acrylamide.

The ratio of the cation-modified group-containing monomer of the cation-modified polyvinyl alcohol is 0.1 to 10 mol%, preferably 0.2 to 5 mol% with respect to vinyl acetate.

The anion-modified polyvinyl alcohol is described in, for example, polyvinyl alcohol having an anionic group as described in JP-A-1-206088 and JP-A-61-237681 and 63-307979. Such a copolymer of vinyl alcohol and a vinyl compound having a water-soluble group, and JP-A-7-285.
The modified polyvinyl alcohol which has a water-soluble group as described in No. 265 is mentioned.

As the nonion-modified polyvinyl alcohol, for example, a polyvinyl alcohol derivative obtained by adding a polyalkylene oxide group to a part of vinyl alcohol as described in JP-A-7-9758, JP-A-8-25795. And a block copolymer of a vinyl compound having a hydrophobic group and vinyl alcohol as described in 1. Polyvinyl alcohol can be used in combination of two or more types such as different degree of polymerization or modification.

The amount of the inorganic fine particles used in the ink absorbing layer depends on the required ink absorbing capacity, the porosity of the void layer,
Generally depends on the type of inorganic pigment and the type of water-soluble binder, but generally 5 to 3 per 1 m ^{2 of} recording paper.
It is 0 g, preferably 10 to 25 g.

The ratio of the inorganic fine particles used in the ink absorbing layer to the water-soluble binder is usually 2: 1 by mass.
It is 20: 1, and particularly preferably 3: 1 to 10: 1.

Further, a cationic water-soluble polymer having a quaternary ammonium salt group may be contained in the molecule,
Usually 0.1 to 10 per 1 m ^{2 of} inkjet recording paper
g, preferably in the range of 0.2-5 g.

In the void layer, the total amount of voids (void volume)
Is preferably 20 ml or more per 1 m ² of recording paper. If the void volume is less than 20 ml / m ^{2 and} the ink amount during printing is small, the ink absorbability is good, but if the ink amount is large, the ink is not completely absorbed, and the image quality may deteriorate. Problems such as delayed drying tend to occur.

In the void layer having an ink holding ability, the void volume relative to the solid content volume is called the void ratio. In the present invention, it is preferable that the porosity is 50% or more because the voids can be efficiently formed without unnecessarily increasing the film thickness.

As the other type of void type, a polyurethane resin emulsion, a water-soluble epoxy compound and /
Or in combination with acetoacetylated polyvinyl alcohol,
Further, the ink absorbing layer may be formed by using a coating liquid in which epichlorohydrin polyamide resin is used in combination. The polyurethane resin emulsion in this case is preferably a polyurethane resin emulsion having a polycarbonate chain, a polycarbonate chain and a polyester chain and having a particle diameter of 3.0 μm, and the polyurethane resin of the polyurethane resin emulsion is a polycarbonate polyol, a polyol having a polycarbonate polyol and a polyester polyol. Polyurethane resin obtained by reacting with an aliphatic isocyanate compound has a sulfonic acid group in the molecule, and further has an epichlorohydrin polyamide resin and a water-soluble epoxy compound and / or acetoacetylated vinyl alcohol. preferable. It is presumed that in the ink absorbing layer using the polyurethane resin, weak cations and anions are formed, and along with this, voids having an ink solvent absorbing ability are formed and an image can be formed.

In the present invention, it is preferable to use a curing agent. The curing agent can be added at any time during the production of the inkjet recording medium, and may be added to the coating liquid for forming the ink absorption layer, for example.

In the present invention, the method of supplying the curing agent for the water-soluble binder after the formation of the ink absorbing layer may be used alone, but the above-mentioned curing agent is preferably used in the coating liquid for forming the ink absorbing layer. It is to be used in combination with the method of adding to.

The curing agent that can be used in the present invention is not particularly limited as long as it causes a curing reaction with a water-soluble binder, but boric acid and salts thereof are preferable, but other known ones are used. In general, a compound having a group capable of reacting with a water-soluble binder or a compound that promotes a reaction between different groups of the water-soluble binder, and is appropriately selected and used according to the type of the water-soluble binder. To be Specific examples of the curing agent include, for example,
Epoxy curing agent (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 curing agents (formaldehyde, glyoxal, etc.), active halogen curing agents (2,4-dichloro-4-)
Hydroxy-1,3,5, -s-triazine etc.), active vinyl compounds (1,3,5-trisacryloyl-hexahydro-s-triazine, bisvinylsulfonylmethyl ether etc.), aluminum alum and the like.

Boric acid or a salt thereof means an oxygen acid having a boron atom as a central atom and a salt thereof, and specifically, orthoboric acid, diboric acid, metaboric acid, tetraboric acid,
Pentaboric acid and octaboric acid and their salts are mentioned.

The boric acid having a boron atom and its salt as a curing agent may be used as an aqueous solution alone or as a mixture of two or more kinds. Particularly preferred is a mixed aqueous solution of boric acid and borax.

The aqueous solutions of boric acid and borax can be added only in relatively dilute aqueous solutions, but by mixing them, a concentrated aqueous solution can be obtained and the coating solution can be concentrated. . Further, there is an advantage that the pH of the aqueous solution to be added can be controlled relatively freely. The total amount of the curing agent used is the above water-soluble binder 1
1 to 600 mg per g is preferred.

The ink absorbing layer according to the present invention is characterized in that its surface layer contains a thermoplastic resin, or in the invention according to claim 2, an inorganic pigment together with the thermoplastic resin.

The surface layer as referred to in the present invention is not limited to the outermost surface layer, and is not particularly limited as long as it has a constitution in which the effects of the present invention are exhibited. The recording medium of the present invention exhibits many of the effects of the present invention by, for example, heating and melting the thermoplastic resin contained in the surface layer to form a film after image recording. For example, in the case of printing with a dye ink, if light resistance or water resistance is improved with or without heat treatment after image recording, a layer containing a thermoplastic resin, or an inorganic pigment and a thermoplastic resin is used. Even if it is not the outermost layer, its configuration corresponds to the present invention.

In the case of printing with pigment ink, if the image quality such as gloss is improved, abrasion resistance is improved, or the degree of bronzing is improved depending on the presence or absence of heat treatment after image recording, heat Even if the layer containing the plastic resin or the inorganic pigment and the thermoplastic resin is not the outermost layer, the structure thereof corresponds to the present invention.

Preferred constitutional examples for clearly indicating the surface layer in the present invention are listed below. The layer constitution according to the present invention is as follows.
It is not limited to these.

1: Structure having a void type ink absorbing layer on a support, and a layer containing a thermoplastic resin or an inorganic pigment and a thermoplastic resin thereon is the outermost layer. Structure 2: on the support Structure 3 having a void-type ink absorbing layer, on which a thermoplastic resin, or a layer containing an inorganic pigment and a thermoplastic resin, is provided with a thin layer for the purpose of improving surface properties: Support It has a void-type ink absorption layer on the body and a layer containing a thermoplastic resin, or an inorganic pigment and a thermoplastic resin thereon, and a thin layer having an ultraviolet absorption function for the purpose of cutting harmful light. Structure 4 in which a layer is provided: A layer containing a matting agent is provided on a layer having a void-type ink absorbing layer on a support, on which a thermoplastic resin, or an inorganic pigment and a thermoplastic resin are contained. Structure 5 provided: having a void type ink absorbing layer on the support Thermoplastic resin thereon, or on an inorganic pigment and a layer that contains a thermoplastic resin, structure in which a peelable layer.

The most preferable constitution among the constitution examples described above is the case where the layer containing the inorganic pigment and the thermoplastic resin according to the item 1 which can most exert the effect of the present invention is the outermost layer.

The surface layer containing the thermoplastic resin or the inorganic pigment and the thermoplastic resin according to the present invention may contain the inorganic pigment, the thermoplastic resin and, if necessary, the binder component and the like.

The inorganic pigment can be selected from the inorganic fine particles that can be used in the above-mentioned void layer.

For example, light calcium carbonate, heavy calcium carbonate, magnesium carbonate, kaolin, clay, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc hydroxide, zinc sulfide, zinc carbonate, hydrotalcite, silicic acid. Examples include white inorganic pigments such as aluminum, diatomaceous earth, calcium silicate, magnesium silicate, synthetic amorphous silica, colloidal silica, alumina, colloidal alumina, pseudoboehmite, aluminum hydroxide, lithopone, zeolite, and magnesium hydroxide. .

As the preferred inorganic pigment, solid fine particles selected from silica and alumina or alumina hydrate are preferably used, and silica is more preferred.

As the silica, silica synthesized by a usual wet method, colloidal silica, silica synthesized by a vapor phase method or the like is preferably used, and as the fine particle silica particularly preferably used in the present invention, colloidal silica or Fine particle silica synthesized by a gas phase method is preferable, and among them, fine particle silica synthesized by a gas phase method not only obtains a high porosity, but also when added to a cationic polymer used for the purpose of immobilizing a dye. It is preferable because coarse aggregates are less likely to be formed. Further, alumina or hydrated alumina may be crystalline or amorphous, and amorphous particles, spherical particles, acicular particles having any shape can be used, In the present invention, it is preferable to use silica and alumina as the inorganic pigment, and among them, silica is more preferable.

The inorganic pigment is preferably in a state in which the fine particle dispersion liquid before being mixed with the cationic polymer is dispersed up to the primary particles.

The particle size of the inorganic pigment is preferably 100 nm or less. For example, in the case of gas phase method fine particle silica, the average particle diameter of the primary particles of the inorganic pigment dispersed in the state of primary particles (particle diameter in the dispersion state before coating) is 100 n.
It is preferably m or less, more preferably 4 to 50 n.
m, most preferably 4 to 20 nm.

Examples of the thermoplastic resin that can be used in the present invention include polycarbonate, polyacrylonitrile, polystyrene, polyacrylic acid, polymethacrylic acid, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, polyester, polyamide, Polyether,
These copolymers and these salts are mentioned. Among them, styrene-acrylic acid ester copolymer, vinyl chloride-vinyl acetate copolymer, vinyl chloride-acrylic acid ester copolymer, ethylene-vinyl acetate copolymer, ethylene-acrylic acid ester copolymer, SBR latex preferable. In addition, the thermoplastic resin may be used by mixing a plurality of polymers having different monomer compositions, particle sizes, and degrees of polymerization.

In selecting a thermoplastic resin, ink receptivity, glossiness of an image after fixing by heating and pressurization,
Image fastness and releasability should be considered.

Regarding the ink receptivity, when the particle diameter of the thermoplastic resin is less than 0.05 μm, the separation of the pigment particles and the ink solvent in the pigment ink becomes slow, which causes a decrease in the ink absorption speed. On the other hand, if it exceeds 10 μm, it is not preferable from the viewpoint of film strength and gloss deterioration of the inkjet recording medium after coating and drying. For this reason, the preferable thermoplastic resin diameter is preferably 0.05 to 10 μm,
More preferably, it is 0.1 to 5 μm. More preferably, it is 0.1 to 1 μm.

The glass transition point (Tg) can be mentioned as a criterion for selecting the thermoplastic resin. When Tg is lower than the coating drying temperature, for example, the coating drying temperature at the time of manufacturing the recording medium is already higher than Tg, the ink solvent permeates, and the voids due to the thermoplastic resin disappear. See also T
If g is higher than the temperature at which the support is denatured by heat, a fixing operation at a high temperature is required in order to melt and form a film after ink jet recording with a pigment ink. Thermal stability etc. becomes a problem. The preferable Tg of the thermoplastic resin is 50 to 150 ° C.

The minimum film forming temperature (MFT) is
It is preferably 50 to 150 ° C. The thermoplastic resin is preferably dispersed in an aqueous system from the viewpoint of environmental suitability,
In particular, an aqueous latex obtained by emulsion polymerization is preferable. At this time, the type obtained by emulsion polymerization using a nonionic dispersant as an emulsifier is a form that can be preferably used. From the viewpoint of odor and safety, the thermoplastic resin used preferably has a small amount of residual monomer components, and is preferably 3% by mass or less, more preferably 1% by mass or less, based on the solid content of the polymer. It is preferably 0.1% by mass or less.

In the case of the surface layer containing an inorganic pigment and a thermoplastic resin, the solid content mass ratio of thermoplastic resin / inorganic pigment can be selected from the range of 90/10 to 10/90, preferably 70/30 to 30 /. The range is 70, more preferably 60/40 to 40/60.

Further, in the present invention, the solid content of the thermoplastic resin contained in the surface layer is 2 g / m ² or more,
It is preferably 20 g / m ² or less, more preferably in the range of ^{2 to} 15 g / m ² , and further preferably 2.5 to.
It is in the range of 10 g / m ² . If the solid content of the thermoplastic resin is too small, a sufficient film cannot be formed and the pigment cannot be sufficiently dispersed in the film. Therefore, the image quality and gloss are not sufficiently improved. On the other hand, if the solid content of the thermoplastic resin is too large, the thermoplastic resin cannot be completely formed into a film in a heating step for a short time, and the fine particles remain as opaqueness to deteriorate the image quality. In addition, the ink absorption speed is also reduced, causing bleeding at the boundary, which is a problem.

The surface layer coating liquid containing the inorganic pigment and the thermoplastic resin may be prepared by dispersing the inorganic pigment and the thermoplastic resin at the same time, or may be prepared by dispersing them and mixing them at the time of preparing the coating liquid.

The support that can be used in the present invention is a support that has been conventionally used for ink jet recording media, for example, an absorbent paper support such as plain paper, art paper, coated paper and cast coated paper. , A plastic support, a non-absorptive support such as a paper support having both surfaces coated with polyolefin, or a composite support obtained by laminating these can be appropriately selected and used. In the invention according to claim 3, It is preferably a non-absorbent support.

In the recording medium of the present invention, the support is subjected to corona discharge treatment or subbing treatment prior to the application of the ink absorption layer for the purpose of increasing the adhesive strength between the support and the ink absorption layer. Is preferred. Furthermore, the recording medium of the present invention does not necessarily have to be colorless, and may be colored recording paper.

In the third aspect of the invention, it is preferable to use a non-absorbent support. However, when a paper support in which both sides of the base paper support are laminated with polyethylene or the like is used, the recorded image is photographic quality. It is particularly preferable because a high quality image can be obtained at a low cost. A paper support laminated with such polyethylene will be described below.

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

Chemical pulp (sulfate pulp or sulfite pulp) having few impurities is preferably used as the above pulp, and pulp having a whiteness improved by bleaching treatment 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 that covers 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 low density polyethylene), polypropylene, etc. Can be used. In particular, the polyethylene layer on the ink absorption layer side is preferably one in which rutile or anatase type titanium oxide is added to polyethylene to improve opacity and whiteness, as is widely used in photographic printing paper. The titanium oxide content is usually 3 to 20 mass% with respect to polyethylene,
It is preferably 4 to 13% by mass.

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

The amount of polyethylene used on the front and back sides of the base paper is selected so as to optimize curling under low humidity and high humidity after providing the void layer and the back layer, but the polyethylene layer on the void layer side is usually 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. Surface roughness: The surface roughness defined by JIS-B-0601 has a maximum height of 10 μ per reference length of 2.5 mm.
It is preferably m or less. 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 ^*
It is preferable that ==-6 to +2. Surface gloss: 6 specified in JIS-Z-8741
9. The 0 degree specular gloss is preferably 10 to 95%. Clark stiffness: Clark stiffness in the conveying direction of the recording medium 50~300cm ^2/100 in which the support is preferably 10. Water content of middle paper: usually 2 to 100% by mass, preferably 2 to 6% by mass relative to the middle paper, the recording medium of the present invention is any of dye ink, pigment ink, water-based ink, oil-based ink, and hot melt ink. It can also be used for water-based dye inks, water-based pigment inks,
It is suitable for oil-based pigment inks, more suitable for water-based dye inks and water-based pigment inks, and among them, water-based pigment inks are most suitable.

Next, a method for manufacturing the ink jet recording medium of the present invention will be described. As a method for producing an inkjet recording medium, each of the constituent layers including the ink absorbing layer can be produced individually or simultaneously by appropriately selecting from known coating methods, coating on a support and drying. As the coating method, for example, roll coating method, rod bar coating method, air knife coating method, spray coating method, curtain coating method, or US Pat. Nos. 2,761,419 and 2,762
A slide bead coating method using a hopper described in Japanese Patent No. 1,791, an extrusion coating method and the like are preferably used.

The viscosity of each coating solution at the time of simultaneous multi-layer coating is 5 when the slide bead coating method is used.
The range is preferably from 100 to 100 mPa · s, more preferably from 10 to 50 mPa · s. When using the curtain coating method, the range of 5 to 1200 mPa · s is preferable, and the range of 25 to 500 mPa is more preferable.
・ S range.

The viscosity of the coating liquid at 15 ° C. is preferably 100 mPa · s or more, and 100 to 30,
000 mPa · s is more preferable, still more preferably 3,000 to 30,000 mPa · s, and most preferably 10,000 to 30,000 mPa · s.

As the coating and drying method, the coating solution is 3 times.
It is preferable that after the simultaneous multilayer coating is performed by heating to 0 ° C. or higher, the temperature of the formed coating film is once cooled to 1 to 15 ° C. and dried at 10 ° C. or higher. During preparation of the coating solution, during coating and during drying, it is preferable to prepare, coat and dry the coating solution at a temperature not higher than Tg of the thermoplastic resin so that the thermoplastic resin contained in the surface layer does not form a film. More preferably,
As the drying conditions, a wet bulb temperature of 5 to 50 ° C. and a film surface temperature of 10
It is carried out under the condition of a temperature range of 50 ° C. In addition, as a cooling method immediately after coating, it is preferable to use a horizontal setting method from the viewpoint of uniformity of the formed coating film.

In the present invention, it is preferable that the step of manufacturing the recording medium has a step of supplying a curing agent for the water-soluble binder after forming the ink absorbing layer. The method of supplying the curing agent is not particularly limited, and for example, a method of applying a solution containing the curing agent after forming the ink absorbing layer, a method of spraying the solution containing the curing agent onto the surface of the recording medium on which the ink absorbing layer has been formed. Etc. can be appropriately selected and used.

Next, the ink jet image forming method and ink jet image of the present invention will be described.

The inkjet image of the present invention can be obtained by recording an image on a recording medium with an inkjet printer. One feature of the present invention is that the method for forming an inkjet image has a treatment step of melting or melting the thermoplastic resin contained in the surface layer. As a method of melting or dissolving the thermoplastic resin contained in the surface layer, for example, a method of applying an organic solvent capable of melting the thermoplastic resin to the image, for example, by applying with an inkjet head, or by melting and dissolving by heating Among these, it is preferable to carry out pressure treatment in combination, but in the present invention, a heating method is preferable, and more preferable is a method of applying pressure simultaneously with heating.

As the ink used for image recording, a water-based ink composition, an oil-based ink composition, a solid (phase change) ink composition, or the like can be used, and the water-based ink composition (for example, 10 per total mass of ink). A water-based inkjet recording liquid containing water in an amount of at least mass% can be particularly preferably used.

As the colorant used in the ink, water-soluble dyes such as acid dyes, direct dyes, reactive dyes, disperse dyes and pigments can be used.

In the invention according to claim 7, it is a preferred embodiment that a pigment ink is used as the colorant, which is particularly preferred from the viewpoint of image storability. As the pigment used in the pigment ink, an insoluble pigment, an organic pigment such as a lake pigment, and carbon black can be preferably used.

The insoluble pigment is not particularly limited, but for example, azo, azomethine, methine, diphenylmethane, triphenylmethane, quinacridone, anthraquinone, perylene, indigo, quinophthalone, isoindolinone, isoindoline, azine, oxazine. ,
Thiazine, dioxazine, thiazole, phthalocyanine, diketopyrrolopyrrole and the like are preferable.

Specific pigments that can be preferably used include the following pigments. Examples of magenta or red pigments 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 15,
C. I. Pigment Red 16, C.I. I. Pigment Red 48: 1, C.I. I. Pigment Red 53: 1,
C. I. Pigment Red 57: 1, C.I. I. Pigment Red 122, C.I. I. Pigment Red 123,
C. I. Pigment Red 139, C.I. I. Pigment Red 144, C.I. I. Pigment Red 149, C.I.
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.

Examples of 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. 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 93, C.I. I. Pigment Yellow 9
4, C.I. I. Pigment Yellow 138 and the like.

As the pigment for green or cyan,
For example, C.I. I. Pigment Blue 15, C.I. I. Pigment Blue 15: 2, C.I. I. Pigment Blue 1
5: 3, C.I. I. Pigment Blue 16, C.I. I. Pigment Blue 60, C.I. I. Pigment Green 7 and the like.

A pigment dispersant may be used for these pigments if necessary, and examples of the pigment dispersant which can be used include higher fatty acid salts, alkyl sulfates, alkyl ester sulfates and alkyl sulfonic acids. Salt, sulfosuccinate, naphthalene sulfonate, alkyl phosphate,
Activator such as polyoxyalkylene alkyl ether phosphate, polyoxyalkylene alkyl phenyl ether, polyoxyethylene polyoxypropylene glycol, glycerin ester, sorbitan ester, polyoxyethylene fatty acid amide, amine oxide, or styrene, styrene derivative, vinyl Block copolymers of two or more monomers selected from naphthalene derivatives, acrylic acid, acrylic acid derivatives, maleic acid, maleic acid derivatives, itaconic acid, itaconic acid derivatives, fumaric acid, fumaric acid derivatives, random copolymers Mention may be made of polymers and their salts.

As a method for dispersing the pigment, various dispersing machines such as a ball mill, a sand mill, an attritor, a roll mill, an agitator, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a pearl mill, a wet jet mill and a paint shaker can be used. it can. Also,
It is also preferable to use a centrifugal separator and a filter for the purpose of removing coarse particles of the pigment dispersion.

The average particle size of the pigment particles in the pigment ink is selected in consideration of stability in the ink, image density, glossiness, light resistance, etc. In addition, in the image forming method of the present invention,
From the viewpoint of improving gloss and improving texture, it is preferable to appropriately select the particle size. In the present invention, the reason why the glossiness or texture is improved is not clear at this stage, but in the formed image, the pigment is in a state in which it is preferably dispersed in the film in which the thermoplastic resin is melted. Presumed to be related to. For the purpose of high-speed treatment, it is necessary to melt the thermoplastic resin into a film in a short time and further sufficiently disperse the pigment in the film. At this time, it is considered that the surface area of the pigment has a great influence, and therefore the average particle size has an optimum region.

The water-based ink composition, which is a preferred form of the pigment ink, is preferably used in combination with a water-soluble organic solvent. Examples of the water-soluble organic solvent that can be used in the present invention include alcohols (for example, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, secondary butanol, tertiary butanol, pentanol, hexanol, cyclohexanol, benzyl). Alcohol, etc.), polyhydric alcohols (for example, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, butylene glycol,
Hexanediol, pentanediol, glycerin, hexanetriol, thiodiglycol, etc.), polyhydric alcohol ethers (for example, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether,
Ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monoethyl ether Butyl ether, ethylene glycol monophenyl ether, propylene glycol monophenyl ether, etc.),
Amines (for example, ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, morpholine,
N-ethylmorpholine, ethylenediamine, diethylenediamine, triethylenetetramine, tetraethylenepentamine, polyethyleneimine, pentamethyldiethylenetriamine, tetramethylpropylenediamine, etc.),
Amides (eg, formamide, N, N-dimethylformamide, N, N-dimethylacetamide, etc.), heterocycles (eg, 2-pyrrolidone, N-methyl-2-pyrrolidone, cyclohexylpyrrolidone, 2-oxazolidone, 1, 3-dimethyl-2-imidazolidinone etc.), sulfoxides (eg dimethyl sulfoxide etc.), sulfones (eg sulfolane etc.), urea, acetonitrile, acetone and the like. Examples of preferable water-soluble organic solvent include polyhydric alcohols. further,
It is particularly preferable to use a polyhydric alcohol and a polyhydric alcohol ether together.

The water-soluble organic solvent may be used alone or in combination of two or more. The total amount of the water-soluble organic solvent added to the ink is 5 to 60% by mass, preferably 10 to
It is 35 mass%.

If necessary, the ink composition may contain various known additives depending on the purpose of improving ejection stability, compatibility with print heads and ink cartridges, storage stability, image storability, and other various performances. For example, a viscosity modifier, a surface tension modifier, a specific resistance modifier, a film-forming agent, a dispersant, a surfactant, a UV absorber, an antioxidant, an anti-fading agent, an anti-fouling agent, an anticorrosive agent, etc. are appropriately selected. For example, polystyrene, polyacrylic acid esters, polymethacrylic acid esters, polyacrylamides, polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, or copolymers thereof, urea resins, or Organic latex fine particles such as melamine resin, liquid paraffin, dioctyl phthalate, tricresyl phosphate, silicone oil, etc. Droplet particles, various surfactants of cationic or nonionic, JP 57-74193,
UV absorbers described in JP-A-57-87988 and JP-A-62-261476, JP-A-57-74192 and 57.
-87989, 60-72785, 61-14.
6591, JP-A-1-95091 and 3-133.
No. 76, etc., anti-fading agent, JP-A-59-4
2993, 59-52689, 62-2800.
69, 61-242871, and JP-A-4-21.
Examples thereof include fluorescent whitening agents, pH adjusting agents such as sulfuric acid, phosphoric acid, citric acid, sodium hydroxide, potassium hydroxide, potassium carbonate and the like described in No. 9266.

The viscosity of the ink composition during flight is preferably 40 mPa · s or less, more preferably 30 mPa · s or less. The surface tension of the ink composition during flight is preferably 20 mN / m or more,
More preferably, it is 30 to 45 mN / m.

A preferred mode of the image forming method of the present invention is
That is, at least a part of the thermoplastic resin contained in the surface layer is melted or dissolved by a heat treatment after image recording.
The heat treatment is performed for the purpose of imparting writability, improving fingerprint adhesion, preventing film peeling, and improving image quality such as gloss by melting or dissolving at least a part of the thermoplastic resin in the recording medium. In the heat treatment, it is desirable to apply the amount of heat necessary to melt or dissolve at least a part of the thermoplastic resin in the recording medium, while the heat treatment should be performed in a short time to shorten the treatment time. However, in the present invention, it is necessary that the melting and dissolving treatment of the thermoplastic resin is not completed within a range where there is substantially no difference in image quality, and the type of thermoplastic resin used in the recording medium ( In particular, it is important to optimally set the heating temperature conditions according to the glass transition temperature) and the amount added.

In order to give the necessary amount of heat in a short time,
It is desirable to heat with a heat source as high as possible, but if the temperature is excessively high, the thermoplastic resin contained in the surface layer will completely melt and form a film, damage to the support, severe curling, or image Surface roughness and roller contamination may occur, and the range of 100 to 200 ° C is preferable, and the range of 100 to 150 ° C is more preferable.

The heating method may be performed by a heater built in the printer or by another heater. The use of a heating roller as the heating means is suitable for preventing the occurrence of unevenness and for performing a continuous process in a small space. In addition, it is cost-effective to use a heat fixing device for electrophotography. For example, a method of heating and pressurizing by passing a recording medium between a heating roller having a built-in heating element and a pressure roller, a method of heat treatment by sandwiching the recording medium between two heating rollers, or a pair of heating rollers. There is a method of providing a fixing belt between them and performing heat treatment.

The heating roller is a hollow roller and is rotated by the driving means. As a heat source, for example, a heating element made of a halogen lamp heater, a ceramic heater, a nichrome wire or the like is built in the roller. The roller is preferably made of a material having high heat conductivity, and particularly preferably a metal roller. The roller surface is preferably coated with a fluororesin to prevent contamination. In addition, a silicon rubber roller coated with heat resistant silicon can be used.

When the heating roller is used, the conveying speed of the recording medium is preferably in the range of 1 to 15 mm / sec. It has been found that this is preferable not only from the viewpoint of high-speed processing but also from the viewpoint of image quality improvement. In order to obtain higher texture and gloss, it is preferable to apply pressure simultaneously with or immediately after heating. The pressure to be applied is 9.8 × 10 ^{4 to} 4.9.
The range of × 10 ⁶ Pa is preferable. This is because pressurization promotes film formation.

FIG. 1 shows an example of an ink jet recording apparatus having a heating roll which can be used in the present invention.
Further, FIG. 2 shows another example of an inkjet recording apparatus having a heating belt which can be used in the present invention.

Next, the printer used for forming the inkjet image of the present invention will be described. The printer that can be used in the present invention is not particularly limited as long as it has, for example, a recording medium storage section, a transport section, an ink cartridge, and an inkjet print head, like a commercially available printer, but at least a roll shape. It is preferable that the printer set includes a recording medium storage section, a transport section, an inkjet print head, a cutting section, and if necessary, a heating section, a pressurizing section, and a recording print storage section. The recording head may be any one of a piezo system, a thermal system, and a continuous system, but the piezo system is preferable from the viewpoint of stability in pigment ink.

[0125]

The present invention will be specifically described below with reference to examples, but the present invention is not limited thereto.

Example 1 << Preparation of Inkjet Recording Medium >> An inkjet recording medium was prepared according to the following procedure.

[Preparation of Inorganic Fine Particle Dispersion] (Preparation of Silica Dispersion-1) Vapor phase silica with an average primary particle size of about 0.012 μm (manufactured by Tokuyama Corporation: QS-
20) 125 kg was suction-dispersed at room temperature in 620 L of pure water whose pH was adjusted to 2.5 with nitric acid using a jet stream inductor mixer TDS manufactured by Mitamura Riken Kogyo Co., Ltd. To 694 L to prepare a silica dispersion liquid-1.

(Preparation of silica dispersion-2) 1.14 kg of the following cationic polymer (P-1), ethanol 2.2
An aqueous solution containing 1.5 L of L and n-propanol (pH =
2.3) 6 L of the silica dispersion-1 prepared above in 18 L
9.4 L was added with stirring, then boric acid 260
7.0 L of an aqueous solution containing g and 230 g of borax was added, and 1 g of an antifoaming agent SN381 (manufactured by San Nopco Ltd.) was added. This mixed liquid was dispersed with a high pressure homogenizer manufactured by Sanwa Kogyo Co., Ltd., and the total amount was adjusted to 97 L with pure water to prepare a silica dispersion liquid-2.

[0129]

[Chemical 1]

[Preparation of Thermoplastic Resin Coating Liquid] (Preparation of Thermoplastic Resin Coating Liquid 1) Styrene-acrylic latex polymer emulsion-polymerized using polyvinyl alcohol as an emulsifier (Tg 78 ° C., average particle size 0.3 μm, solid content concentration) 40%) was adjusted to pH 4.7 with a 6% nitric acid aqueous solution, and this was used as a thermoplastic resin coating liquid 1.

[Preparation of Each Coating Solution] After preparing each coating solution as described below, each coating solution was put into a commercially available filter (TCP10 or TCP30 manufactured by Toyo Roshi Kaisha, Ltd.).
Filtered.

(Preparation of Lower Layer Coating Liquid 1) While stirring at 40 ° C., to 710 ml of the silica dispersion-2 prepared above,
The following additives were sequentially mixed to prepare Lower Layer Coating Liquid 1.

[0133]   Polyvinyl alcohol (Kuraray Industry Co., Ltd .: PVA203)     10% aqueous solution of 3 ml   Polyvinyl alcohol (Kuraray Industry Co., Ltd .: PVA235) 4.8% and     Polyvinyl alcohol (Kuraray Industry Co., Ltd .: PVA245)     273 ml of an aqueous solution containing 1.84% of The total volume was adjusted to 1000 ml with pure water.

(Preparation of Upper Layer Coating Liquid 1) The thermoplastic resin coating liquid 1 prepared above was used as the upper layer coating liquid 1.

(Preparation of Upper Layer Coating Liquid 2) The thermoplastic resin coating liquid 1 and the lower layer coating liquid 1 prepared above were mixed so that the solid content ratio of the thermoplastic resin and the inorganic pigment was 50:50. Thereafter, water was added so that the viscosity at 43 ° C. was 45 mPa · s, and this was used as upper layer coating liquid 2.

(Preparation of Upper Layer Coating Solution 3) Above Upper Layer Coating Solution 2
In the preparation of, the upper layer coating liquid 3 was prepared in the same manner except that the solid content ratio of the thermoplastic resin and the inorganic pigment was changed to 40:60.

(Preparation of Upper Layer Coating Solution 4) Above Upper Layer Coating Solution 2
In the preparation of, the upper layer coating liquid 4 was prepared in the same manner except that the solid content ratio of the thermoplastic resin and the inorganic pigment was changed to 30:70.

(Preparation of Upper Layer Coating Liquid 5) Above Upper Layer Coating Liquid 2
In the preparation of, the upper layer coating liquid 5 was prepared in the same manner except that the solid content ratio of the thermoplastic resin and the inorganic pigment was changed to 60:40.

(Preparation of Upper Layer Coating Liquid 6) Above Upper Layer Coating Liquid 2
In the preparation of, the upper layer coating liquid 6 was prepared in the same manner except that the solid content ratio of the thermoplastic resin and the inorganic pigment was changed to 70:30.

(Preparation of Upper Layer Coating Liquid 7) Above Upper Layer Coating Liquid 2
In the preparation of, the upper layer coating liquid 7 was prepared in the same manner except that the solid content ratio of the thermoplastic resin and the inorganic pigment was changed to 80:20.

(Preparation of upper layer coating liquid 8) 100 parts of alumina hydrate (Cataloid AS-3, manufactured by Catalyst Kasei), polyvinyl alcohol (PVA11, manufactured by Kuraray Industries Co., Ltd.)
7) Disperse 30 parts to prepare an alumina solution, and add the alumina solution and the thermoplastic resin coating liquid 1 prepared above to
An upper layer coating liquid 8 was prepared by mixing the thermoplastic resin and alumina so that the solid content ratio was 50:50.

[Preparation of Inkjet Recording Medium] (Preparation of Sample 1: Comparative Example) Paper support having both sides coated with polyethylene (RC paper, thickness: 220 μm, polyethylene 13 in polyethylene in the ink absorption layer side) (Containing a mass% of anatase type titanium oxide), in order from the support side, the lower layer coating solution 1 was wetted as a first layer to a film thickness of 18
In 4 [mu] m, the (average particle size of the thermoplastic resin: 0.3 [mu] m) layer coating solution 1 as the second layer to a condition in which the 2.0 g / m ² as solid content of the thermoplastic resin, using a slide hopper 2 The layers were simultaneously coated and dried. Each coating solution was heated to 40 ° C. for coating, immediately after coating, cooled in a cooling zone maintained at 0 ° C. for 20 seconds, and then blown with 25 ° C. air (15% relative humidity) for 60 seconds for 45 seconds. ℃ wind (relative humidity 25
%) For 60 seconds, 6 at 50 ° C wind (relative humidity 25%)
Sequential drying for 0 seconds, 20 ~ 25 ℃, relative humidity 40 ~ 6
After conditioning the humidity for 2 minutes in an atmosphere of 0 ° C., the sample was wound up to prepare Sample 1 as a recording medium.

(Production of Samples 2 to 8: Present Invention) Sample 1 above
In the same manner as described above, except that the prepared upper layer coating liquids 2 to 8 were used in place of the second layer upper layer coating liquid 1,
Samples 2 to 8 having different solid content ratios of the upper layer thermoplastic resin and the inorganic pigment were prepared.

(Preparation of Sample 9: Present Invention) Sample 2 was prepared in the same manner as in Sample 2, except that the support was changed to a water-absorbent paper support (middle paper for coated paper, thickness 165 μm, referred to as paper support). 9 was produced.

<< Preparation of Ink >> [Preparation of Aqueous Pigment Ink] (Preparation of Pigment Dispersion Liquid) <Preparation of Yellow Pigment Dispersion 1> C.I. I. Pigment Yellow 74 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 to obtain a yellow pigment dispersion 1. The average particle size of the obtained yellow pigment was 112 nm.

<Preparation of Magenta Pigment Dispersion 1> C.I. I. Pigment Red 122 25% by mass John Cryl 61 (acrylic-styrene resin, manufactured by Johnson Co.) Solid content 18% by mass Diethylene glycol 15% by mass Ion-exchanged water 42% by mass Mixing the above additives, 0.3 mm zirconia beads Was dispersed using a horizontal bead mill (System Zetamini manufactured by Ashizawa Co., Ltd.) filled with 60% by volume to obtain a magenta pigment dispersion 1. The average particle size of the obtained magenta pigment was 105 nm.

<Preparation of Cyan Pigment Dispersion 1> C.I. I. Pigment Blue 15: 3 25% by mass John Cryl 61 (acrylic-styrene resin, manufactured by Johnson Co.) 15% by mass as solid content Glycerin 10% by mass Ion-exchanged water 50% by mass Add each of the above additives to obtain 0.3 mm Cyan pigment dispersion 1 was obtained by dispersing using a horizontal bead mill (System Zetamini manufactured by Ashizawa Co., Ltd.) filled with zirconia beads at a volume ratio of 60%. The average particle size of the obtained cyan pigment is 87.
was nm.

<Preparation of Black Pigment Dispersion 1> Carbon black 20% by mass Styrene-acrylic acid copolymer (molecular weight 7,000, acid value 150) 10% by mass Glycerin 10% by mass Ion-exchanged water 60% by mass Each of the above additions The agents were mixed and dispersed using a horizontal bead mill (System Zetamini manufactured by Ashizawa Co.) filled with 0.3 mm zirconia beads at a volume ratio of 60% to obtain a black pigment dispersion 1. The average particle size of the obtained black pigment was 75 nm.

(Preparation of Pigment Ink) <Preparation of Yellow Dark 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 Mass% Ion-exchanged water 54.9 mass% The above compositions were mixed, stirred, and filtered through a 1 μm filter to prepare Yellow Dark Ink 1, which is the aqueous pigment ink of the present invention. The average particle size of the pigment in the ink is 120 n
m, and the surface tension γ was 36 mN / m.

<Preparation of Yellow Light Ink 1> Yellow Pigment Dispersion 1 3% by mass Ethylene glycol 25% by mass Diethylene glycol 10% by mass Surfactant (Surfynol 465, Nissin Chemical Industry Co., Ltd.) 0.1% by mass Ion-exchanged water 61 1.9% by mass or more of the respective compositions were mixed, stirred, and filtered with a 1 μm filter to prepare Yellow Light Ink 1 which is the aqueous pigment ink of the present invention. The average particle size of the pigment in the ink is 118 n
m, and the surface tension γ was 37 mN / m.

<Preparation of Magenta Dark 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 1.9% by mass or more of each composition were mixed, stirred, and filtered with a 1 μm filter to prepare magenta dark ink 1 which is the aqueous pigment ink of the present invention. The average particle size of the pigment in the ink is 113n
m, and the surface tension γ was 35 mN / m.

<Preparation of Magenta Light Ink 1> Magenta Pigment Dispersion 1 3% by mass Ethylene glycol 25% by mass Diethylene glycol 10% by mass Surfactant (Surfynol 465, Nissin Chemical Industry Co., Ltd.) 0.1% by mass Ion-exchanged water 61 0.9% by mass or more of the respective compositions were mixed, stirred, and filtered through a 1 μm filter to prepare magenta light ink 1, which is the aqueous pigment ink of the present invention. The average particle size of the pigment in the ink is 110 n
m, and the surface tension γ was 37 mN / m.

<Preparation of Cyan Dark Ink 1> Cyan Pigment Dispersion 1 10% by mass Ethylene glycol 20% by mass Diethylene glycol 10% by mass Surfactant (Surfynol 465 Nisshin Chemical Industry Co., Ltd.) 0.1% by mass Ion-exchanged water 59 Cyan dark ink 1 which is the water-based pigment ink of the present invention was mixed with 9% by mass or more of each composition, stirred and filtered with a 1 μm filter.
Was prepared. The average particle size of the pigment in the ink was 95 nm, and the surface tension γ was 36 mN / m.

<Preparation of Cyan Light Ink 1> Cyan Pigment Dispersion 1 2% by mass Ethylene glycol 25% by mass Diethylene glycol 10% by mass Surfactant (Surfynol 465 Nisshin Chemical Industry Co., Ltd.) 0.2% by mass Ion-exchanged water 62 C. 8% by mass or more of each composition was mixed, stirred, filtered with a 1 .mu.m filter, and cyan light ink 1 which is an aqueous pigment ink of the present invention.
Was prepared. The average particle size of the pigment in the ink was 92 nm, and the surface tension γ was 33 mN / m.

<Preparation of Black Dark Ink 1> Black Pigment Dispersion 1 10% by mass Ethylene glycol 20% by mass Diethylene glycol 10% by mass Surfactant (Surfynol 465 Nisshin Chemical Industry Co., Ltd.) 0.1% by mass Ion-exchanged water 59 1.9% by mass or more of the respective compositions were mixed, stirred, and filtered with a 1 μm filter to prepare Black Dark Ink 1 which is the aqueous pigment ink of the present invention. The average particle diameter of the pigment in the ink is 85 nm
And the surface tension γ was 35 mN / m.

<Preparation of Black Light Ink 1> Black Pigment Dispersion 1 2% by mass Ethylene glycol 25% by mass Diethylene glycol 10% by mass Surfactant (Surfynol 465, Nissin Chemical Industry Co., Ltd.) 0.1% by mass Ion-exchanged water 62 1.9% by mass or more of the respective compositions were mixed, stirred, and filtered through a 1 μm filter to prepare Black Light Ink 1 which is the aqueous pigment ink of the present invention. The average particle size of the pigment in the ink is 89 nm
And the surface tension γ was 36 mN / m.

<< Preparation of Inkjet Images >> Inkjet images 1 to 9 were prepared using the recording media prepared above and the pigment inks.

As the ink jet printer, each image was formed by using a head for 8 colors and the printer of FIG. 2 described below. The printed image is each wedge image of yellow, magenta, cyan and black,
A sample in which a grid-shaped test chart and a portrait image of a person are drawn with Y-, M-, C-, B-, G-, R-, and Bk bands of 1 cm width vertically and horizontally, and are not printed at all (white background sample) Was also subjected to the same heat treatment.

FIG. 2 is a schematic diagram showing an ink jet recording apparatus having a heating belt used in the examples.

In FIG. 2, ink (yellow, magenta, cyan, black ink) is set on the head corresponding to eight colors of the printer, a roll-shaped recording medium having a roll width of 12.7 cm is set, and yellow, magenta, cyan, and Images were continuously printed, including the black wedge image.
Samples 1 to 9, which are recording media, were cut every 8.9 cm by a built-in cutter and printed. In this way, prints corresponding to the L plate were continuously produced. In the post-treatment after inkjet recording, heat fixing treatment was carried out using a heat fixing belt having a belt surface temperature of 117 ° C., and a part of the thermoplastic resin in the uppermost layer was melted and melted to form an image. As the heat treatment conditions, the belt surface temperature is 117 ° C., a pressure of 314 N as a linear pressure per 24 cm width is applied between the heating roller 41 and the pressure bonding roller 42 shown in FIG.
<< Measurement of Characteristic Value of Inkjet Recording Medium >> Treated at 4 m / min (Observation of Surface After Heat Treatment) After the above heat treatment, the white background portion was observed with a reflection electron microscope to obtain a porous structure. Was determined to exist.

(Measurement of Ink Absorption Capacity-1) The white background sample after the heat treatment was cut into 80 mm × 100 mm, 25 ° C.
After conditioning the humidity for 24 hours in an atmosphere of 50% RH, this sample was immersed in pure water for 10 seconds. At this time, the air in the voids of the sample adheres to the surface as bubbles due to the absorption of water to prevent water absorption, so the sample was vibrated appropriately to remove the bubbles. Then, after 10 seconds, the sample was pulled up from water, the water content on the surface was quickly removed with a filter paper, and the mass before and after the immersion was measured.
Sought as.

(Measurement of Ink Absorption Capacity-2) The ink absorption amount of unprinted and unheated samples (each recording medium immediately after preparation) was measured by the same method as described above, and the ink absorption amount B
Then, the ink absorption ratio before and after the heat treatment was determined according to the following equation.

Ink absorption amount ratio = (ink absorption amount A / ink absorption amount B) × 100 (%) (Measurement of ink transfer amount: Bristow method) Each of the heat-treated white background samples was heated at 25 ° C. and 50% RH. After standing in the atmosphere for 12 hours, the measurement was performed using a Bristow tester type II (pressurized type), which is a liquid dynamic absorption tester manufactured by Kumagai Riki Kogyo Co., Ltd. In order to improve the measurement accuracy, the liquid used for the measurement was a commercially available water-based magenta ink, and the area of the magenta-stained portion on the sample was measured after a contact time of 40 msec to determine the ink transfer amount. Then, the amount of ink transfer after a contact time of 200 msec was determined by the same method.

Table 1 shows the results obtained as described above.

[0165]

[Table 1]

<< Evaluation of Each Characteristic of Inkjet Recording Medium >> (Evaluation of Writing Property) With respect to the above-prepared heat-treated white background sample, use a fountain pen, an oil-based ballpoint pen, and a water-based pen to write characters on the white background. , Evaluated the ink ride. Furthermore, in order to evaluate the durability of the character, the character was evaluated by rubbing the character once with Kimwipe S-200 (made by Crecia) and the writing property was evaluated according to the criteria described below.

5: All writing tools can be used for writing without problems, and the durability of the characters is very good. 4: Some writing tools have slightly weak character parts, but the durability of the characters. Is good and almost no problem 3: Some writing tools have a weak character part and the durability of the character is a little bad, but there is no problem in practical use 2: The writing part is bad with all writing tools Moreover, the durability of the characters is also poor and there is a problem with the writing performance. 1: Writing is extremely low because it cannot be written with all writing tools (evaluation of anti-fingerprint adhesion). The patch with the highest image density created above. For the image (output density 100%), the wedge image, and the white background portion, five persons arbitrarily selected attach three fingerprints to each image surface and the white background portion with their right thumbs, and then the adhered portion 20 Visual evaluation is performed by a general evaluator, and the It was boss.

5: 15 or more people judged that the fingerprint adhered part was hardly noticed 4: 10 to 14 people judged that the fingerprint adhered part was hardly noticeable 3: Judged that the fingerprint adhered part was hardly noticeable 7 to 9 people 2: 4 to 6 people judged that the fingerprint adhered part was hardly noticeable 1: 3 people or less judged that the fingerprint adhered part was hardly noticeable (evaluation of film peeling resistance) 25 white background samples
After being left for 3 months in an atmosphere of 50 ° C. and 50% relative humidity, the surface was observed with a magnifying glass to confirm the presence or absence of fine film peeling on the surface, and the judgment was made according to the evaluation criteria described below.

5: No film peeling was observed at all 4: Very fine film peeling occurred at 1-2 places, but not visually observable 3: Ultra fine film peeling occurred at 3-6 places, but visually 2) Fine film peeling has occurred partially, and it can be visually observed 1: Film peeling has clearly occurred, which can be clearly confirmed even visually (evaluation of cockling) Each sample surface after heat fixing was visually observed to determine whether cockling (wrinkles or waviness of the recording medium) occurred.

(Evaluation of Glossiness) The image of the black solid chart portion of the evaluation sample was reflected by the image clarity measuring device ICM-1DP (manufactured by Suga Test Machine Co., Ltd.) at 60 degrees, and the image clarity at an optical comb 2 mm (gloss value C value). %) Was measured. The evaluation was performed according to the following criteria.

5: C value% is 61 or more 4: C value% is 60 to 55 3: C value% is 54 to 51 2: C value% is 50 to 41 1: C value% is 40 or less In the above evaluation rank It was judged that 4 and 3 were practically preferable ranks.

Table 2 shows the evaluation results obtained as described above.

[0173]

[Table 2]

As is clear from Table 2, the sample of the present invention, which contains a thermoplastic resin in the surface layer and has a porous surface after heat treatment, has a writing property in comparison with the comparative example. ,
It can be seen that the anti-fingerprint property and the film peeling resistance are excellent and the good glossiness is maintained.

Further, as a characteristic of the white background portion of the recording medium after the heat treatment, the ink absorption capacity specified in the present invention is 5 ml.
/ M ² or more, a sample in which the ink absorption capacity of the white background portion after passing through the treatment step is 50% or more of the ink absorption capacity of the white background portion before passing through the treatment step, and the contact time by the Bristow method is 40 ms. Ink transfer amount is 5ml / m
² or more 15 ml / m ² or less samples, it is seen that exhibits a more favorable effect. It was also confirmed that cockling did not occur and good characteristics were obtained by using a non-absorbent support (RC paper) for the absorbent support.

[0176]

According to the present invention, writability, anti-fingerprint adhesion,
It was possible to provide an inkjet recording medium having excellent glossiness and reduced occurrence of cockling and film peeling, an inkjet image forming method using the same, and an inkjet image.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an example of an inkjet recording apparatus having a heating roller used in the present invention.

FIG. 2 is a schematic configuration diagram showing another example of an inkjet recording apparatus having a heating belt used in the present invention.

[Explanation of symbols]

1 recording medium 1a slack section 2 Transporting means for recording medium 21 Transport roller pair 3 recording head 34 recording medium holding unit 4 heating and pressurizing means 41 heating roller 42 Crimping roller 43 heating element 44 heating belt 45 Lower belt 46 Driven roller 5 Temperature sensor 6 Recording medium cutting means 61, 62 cutter 7 Slack forming means 71 First Roller Pair 72 Second Roller Pair

Continued front page    (72) Inventor Makoto Kaga             Konica Stock Market, 1 Sakura-cho, Hino City, Tokyo             In-house (72) Inventor Teruyuki Fukuda             Konica Stock Market, 1 Sakura-cho, Hino City, Tokyo             In-house F term (reference) 2C056 EA04 EA13 EC13 EC29 FC02                       FC06 HA29                 2H086 BA03 BA05 BA13 BA15 BA16                       BA19 BA33 BA55

Claims (8)

[Claims] 1. A treatment in which at least a part of the thermoplastic resin is melted or dissolved after printing in an ink jet recording medium having at least one ink absorbing layer on a support and having a surface layer containing a thermoplastic resin. An ink jet recording medium, wherein the surface layer after passing through the step is porous. 2. The ink jet recording medium according to claim 1, wherein the surface layer contains a thermoplastic resin and an inorganic pigment. 3. The inkjet recording medium according to claim 1, wherein the support is a non-absorbent support. 4. The ink jet recording medium according to claim 1, wherein the ink absorption capacity of the white background portion after passing through the treatment step is 5 ml / m ² or more. 5. The ink absorption capacity of the white background portion after passing through the processing step is 50% or more of the ink absorption capacity of the white background portion before passing through the processing step.
5. The inkjet recording medium according to any one of items 4 to 4. 6. The amount of ink transfer at a contact time of 40 ms according to the Bristow method for a white background portion after passing through the treatment step is 5 ml / m ² or more and 15 ml / m ² or less. 6. The inkjet recording medium according to any one of items 1 to 5. 7. An inkjet according to any one of claims 1 to 6 comprising a step of printing with a pigment ink and a treatment step of melting or dissolving at least a part of a thermoplastic resin. An inkjet image forming method characterized by forming an image. 8. An ink jet recording medium according to any one of claims 1 to 6 is printed with a pigment ink,
An inkjet image formed by performing a treatment for melting or dissolving at least a part of the thermoplastic resin.