JP2005081754A - Inkjet recording method and recorded matter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording method for providing a high-quality image which combines high glossiness with uniformity of ozone fading, which has excellent fretting resistance and which has no unevenness in gloss, and recorded matter created by using the inkjet recording method. <P>SOLUTION: In this inkjet recording method, after the image is formed on an inkjet recording paper sheet by using ink containing a coloring agent, colorless ink, which contains a polymer with a film forming ability and which does not substantially contain the coloring agent, is ejected onto the image. The inkjet recording method is characterized as follows: the amount of inorganic ink droplets is in a range of 1.0-5.0 pl (picoliter); and a protective film layer with a dry solid of 0.05-0.3 g per 1 m<SP>2</SP>of the inkjet recording paper sheet is formed substantially all over the printed image. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a novel ink jet recording method and recorded matter produced using the same.

  In recent years, ink jet recording materials have been rapidly improved in image quality and approaching photographic image quality. In particular, in order to achieve image quality comparable to photographic image quality by ink jet recording, improvements have been made from the aspect of ink jet recording paper (hereinafter simply referred to as recording paper). A void-type recording paper provided with a porous layer made of a hydrophilic polymer has a high gloss, shows a vivid color, or has an excellent ink absorption and drying property. It is becoming one. In particular, when a non-water-absorbing support is used, there is no occurrence of cockling after printing, as seen on a water-absorbing support, so-called “wrinkles”, and a high smooth surface can be maintained. Prints can be obtained and gradually become the mainstream of photographic prints created by inkjet recording.

  Inkjet recording is generally divided into ink using water and a water-soluble solvent as an ink solvent, and ink using a non-aqueous oil-based solvent, and each has a type using a dye and a type using a pigment. In order to obtain a recorded image, dedicated paper suitable for each type is required. Of these, water-based inks are mainly used from the viewpoint of environment and safety.

  Inkjet prints using water-soluble dye inks have high image sharpness, uniform surface gloss, and color prints comparable to photographic image quality. However, prints using this water-soluble dye have poor storage stability compared to pigment inks, are susceptible to fading due to sunlight, ozone, or other oxidizing gases, and have a large image blur. It has become. In particular, in a void-type recording paper provided with a fine porous layer, the contact area between the dye and the indoor air is widened, and therefore, fading due to the oxidizing gas in the air is large, and improvement thereof is desired.

  In order to improve the deterioration due to such storage, it has been proposed to add various antioxidants as anti-fading agents. For example, JP-A-57-87989, JP-A-57-74192 and JP-A-60-72785 discloses an ink-jet recording paper containing various compounds as an antioxidant, and JP-A-57-74193 discloses an ink-jet recording paper containing an ultraviolet absorber. Hydrazides are added to No. 61-14659, hindered amine antioxidants are added to JP-A 61-14659, and nitrogen-containing heterocyclic mercapto compounds are added to JP-A 61-177279. However, Japanese Patent Laid-Open Nos. 1-115677 and 1-335479 may be added with a thioether-based antioxidant. Hindered phenol antioxidants having a specific structure are added to No. 3, and JP-A-3-13376 includes adding a hindered phenol antioxidant and a hindered amine antioxidant in combination. Ascorbic acids are added to 7-195824 and 8-150773, zinc sulfate is added to JP-A-7-149037, and thiocyanate is contained in JP-A-7-314882. Japanese Patent Application Laid-Open No. 8-318792 discloses that thiourea derivatives and the like are added, and that Japanese Patent Application Laid-Open Nos. 7-276790 and 8-108617 contain saccharides. Can be added with a phosphoric acid antioxidant, and nitrite, sulfite, thiosulfate, etc. are added to JP-A-8-300807. But the Japanese Patent Laid-Open No. 9-267544 discloses that the addition of hydroxylamine derivative.

  However, the effect of ink jet recording paper having fine pores is not always sufficient, and when these various anti-fading agents are added in a large amount in order to obtain a sufficient anti-fading effect, the ink absorption of the porous layer There are many disadvantages such as lowering the performance.

  Further, when water-soluble dye ink is used, there is a weak point that bleeding occurs due to high hydrophilicity and water resistance is inferior. That is, the dye is likely to bleed when stored for a long time under high humidity after image recording or when water droplets adhere to the printed surface. In order to solve this problem, it is a common practice to add a dye-fixing substance such as a cationic substance to the porous layer. For example, a method of binding to an anionic ink dye using a cationic polymer and immobilizing it firmly is preferably used. Examples of such a cationic polymer include a polymer having a quaternary ammonium group. For example, “Inkjet printer technology and materials” (issued by CMC, July 1998) and JP-A-9-193532 [ [0008] is described in the literature. Also proposed is a method in which water-soluble polyvalent metal ions are added in advance to an ink jet recording paper, and the dye is solidified and fixed during ink jet recording. Although the use of a cationic polymer or polyvalent metal ion improves bleeding and water resistance, the dye is unevenly dyed in the ink absorption layer due to binding with the cationic polymer or polyvalent metal. For this reason, even if the anti-fading agent described above is added, if the diffusibility is small in the ink absorbing layer, the effect may not be sufficiently exhibited.

  On the other hand, the pigment ink has high durability of the image such as light resistance, gas resistance, and bleeding of the image, but it has a weak point that the gloss is easily changed to an image shape, and as a result, it is difficult to obtain a print close to photographic quality.

  Various techniques have been proposed to compensate for such weak points. However, it is difficult to obtain an ink jet print having high gloss and no change in gloss in an image state by a normal recording method for the basic reason. That is, the pigment particles used in the pigment ink generally have a size of about 0.1 μm (100 nm). The size of the dye molecule is on the order of 1 nm. When the ink is made of pigment particles much smaller than 0.1 μm, the characteristics approach that of the dye ink, and the high durability characteristic of the pigment ink is lowered. .

  On the other hand, in order to obtain a highly glossy and highly colored recording paper, the size of the inorganic fine particles used for making the ink absorbing layer of the recording paper porous should be 0.1 μm or less. It is necessary because of the relationship.

  Therefore, in order for the pigment particles of the ink to land on the recording paper composed of particles of the same size in order to achieve high gloss and high color, the pigment ink particles do not penetrate into the ink absorbing layer and the surface is uneven. Will form. At this time, the pigment particles of the ink are oriented on the surface of the receiving layer, and the gloss increases from the white background (becomes metallic glossy), or the pigment particles randomly coalesce on the surface to make the surface unevenness coarser This causes problems such as causing irregular reflection and reducing gloss. Such behavior is largely dependent on the characteristics of the pigment ink, but when a normal image is printed, it is common that a very unnatural gloss change occurs in the image and a high-quality print cannot be obtained. .

  The present applicant has made various studies in order to improve the unnaturalness of an image formed with the pigment ink as described above. For example, Japanese Patent Laid-Open No. 2001-341409 proposes a recording sheet that improves the unnaturalness of an image by using a recording sheet having a specific range of surface roughness (Ra). According to this technique, although the unnaturalness that the gloss changes to an image is improved, a recording sheet having a sufficiently high gloss cannot be obtained. In addition, in International Publication Nos. WO03 / 02473, Japanese Patent Application Nos. 2002-352196, 2003-27191, and 2003-77673, a polymer is formed in an area where an image is recorded with pigment ink or an area where no image is recorded with pigment ink. An ink jet recording method has been proposed in which the uniformity of gloss is improved by spraying a colorless ink containing a liquid. However, according to the results of subsequent studies, when such colorless ink is sprayed in an image-like or non-image-like manner, not only sufficient gloss uniformity cannot be achieved at the interface or intermediate density region, but also light resistance. It was found that the fading image and the gas fading improvement effect are partially different and the fading image becomes unnatural.

  Further, an inkjet recording method in which a protective film layer is formed with a polymer-containing colorless ink on an image surface printed with pigment ink is disclosed (for example, see Patent Documents 1 to 7).

  Prints in which colorless ink is ejected over the entire image recording surface as described in each of the above publications and a protective film layer is formed on the entire image area have a glossy or fading color at the interface or intermediate density area. It is possible to obtain a color print that is less dull in nature, highly durable, high gloss, and closer to the texture of a silver salt photograph. However, on the other hand, it has been found that there is a new problem when forming a protective coating layer by spraying colorless ink over the entire image recording area. That is, when colorless ink is sprayed onto the area printed with pigment ink, if the ink is not discharged below the ink absorption capacity of the porous ink absorption layer, the colorless ink overflows in the image area and forms a patchy protective film layer. . When the protective coating layer is formed in a patchy shape, a local change in the thickness of the protective coating layer occurs, which causes a slight point-like gloss unevenness or a rainbow unevenness phenomenon due to light diffraction. Therefore, in order to avoid this phenomenon, the droplet forming the protective film layer and the film thickness to be formed are important.

  Furthermore, in order to improve the scratch resistance of the image with the protective film layer, not only the film thickness of the protective film layer becomes a problem, but also the uniformity of the film is important. That is, it is difficult to obtain sufficient scratching properties when the film is not uniform. For example, in the case where the surface of the protective coating layer has a large number of surface irregularities, the scratching force is locally concentrated due to unevenness, and the protective coating layer is damaged therefrom, and the expected scratching property cannot be obtained.

In general, the ejection amount of pigment ink necessary for forming an image is approximately 15 to 25 ml per 1 m ^{2 of} recording paper, and ink absorption of an ink jet recording paper provided with a porous ink absorbing layer on a non-water-absorbing support. The volume is generally 20-30 ml. Therefore, in order to form a protective film layer with colorless ink, it is necessary to carry out the discharge amount of this colorless ink at about 10 ml or less per 1 m ^{2 of} recording paper. If a measure for further increasing the porous ink absorption capacity of the recording paper is taken, this limitation is eased, but it is not preferable because of a significant increase in cost and curl.

By the way, the film-forming polymer concentration contained in the colorless ink cannot be extremely increased due to the restriction that it should have an appropriate viscosity (usually about several mPa · s) as the ink. Therefore, the range which can be normally used is about 10% or less. Due to such restrictions, in practice, the thickness of the protective coating layer formed of colorless ink is about 1 g / m ² as a polymer, and the thickness is about 1 μm or less.

In this regard, Japanese Patent Application Laid-Open No. 2002-301428 describes the thickness of the coating layer as 0.1 to 100 μm, preferably 0.5 to 20 μm as the thickness after drying. Japanese Patent Application Laid-Open No. 2003-53942 discloses that the amount of coating layer is 0.77 to 7.7 g / m ² in terms of wet film thickness, and the solid content concentration of the coating liquid is 0.5 to 20% by mass. Therefore, the dry solid content of the coat layer is 0.0039 to 1.54 g / m ² . Japanese Patent Laid-Open No. 2002-264465 has a description of coating in the range of 0.1 to 5 g / m ² . When the dry solid mass is 1 g / m ² and the solid density is 1, the dry film thickness of the coat layer is 1 μm.

According to the study by the present inventors, when a protective film having a film thickness of about 0.5 to 1 μm is formed, a change in color tone or a slight change in film thickness that is considered to be caused by rainbow-like interference fringes in the coat layer. It has been found that minute glaring easily occurs. The rainbow-like interference fringe is a phenomenon that changes the color tone when the viewing angle of the recording paper is changed, and is a phenomenon that gives a different color tone depending on the viewing angle of the white background portion or the image recording portion.
International Patent Publication WO00 / 06390 Pamphlet JP 2000-225695 A JP 2001-270217 A JP 2001-277488 A Japanese Patent Laid-Open No. 2002-201428 JP 2002-264465 A JP 2002-307755 A

  SUMMARY OF THE INVENTION An object of the present invention is an ink jet recording method that provides both high glossiness and uniformity of ozone fading, has excellent scratch resistance, and gives a high-quality image without gloss unevenness, and is produced using the same. Is to provide the recorded material.

The above object of the present invention is achieved by the following configurations.
(Claim 1)
Inkjet recording in which an image is formed on an inkjet recording paper with an ink containing a colorant, and then a colorless ink containing a polymer having a film-forming ability and containing substantially no colorant is ejected onto the image. In the method, a protective film layer having a colorless ink droplet amount of 1.0 to 5.0 pl (picoliter) and a dry solid content of 0.05 to 0.3 g per 1 m ^{2 of the} inkjet recording paper is formed. An ink jet recording method characterized by forming the image on the entire surface of a substantially printed image.
(Claim 2)
2. The ink jet recording method according to claim 1, wherein the film-forming polymer in the colorless ink contains a water-based dissolved resin or a water-based dispersed resin.
(Claim 3)
3. The ink jet recording method according to claim 1, wherein insolubilization or aggregation of the colorant does not occur even when the ink containing the colorant and the colorless ink come into contact with each other.
(Claim 4)
The inkjet recording method according to claim 1, wherein the colorant of the ink containing the colorant is a pigment.
(Claim 5)
A recorded matter, wherein an image is formed by the ink jet recording method according to claim 1.

  According to the present invention, an ink jet recording method that achieves both high glossiness and uniformity of ozone fading, has excellent scratch resistance, and gives a high-quality image without gloss unevenness, and produced using the same Recorded material can be provided.

  Hereinafter, the best mode for carrying out the present invention will be described in detail, but the present invention is not limited thereto.

In the present invention, after an image is formed on an inkjet recording paper with an ink containing a colorant, a colorless ink containing a polymer having a film-forming ability and containing substantially no colorant on the image. In the ink jet recording method for discharging ink, a protective film layer having a colorless ink droplet amount of 1 pl (picoliter) to 5 pl and a dry solid content of 0.05 to 0.3 g per 1 m ^{2 of the} ink jet recording paper. Is formed on the entire surface of the printed image to achieve both high glossiness and uniformity of ozone fading, and has a high-quality image having excellent abrasion resistance and no gloss unevenness. As soon as the present inventors have found that an ink jet recording method can be realized, the present invention has been achieved.

  Details of the present invention will be described below.

[Ink containing colorant]
In the ink jet recording method of the present invention, as the ink containing a colorant, either a dye ink or a pigment ink can be applied, but it is preferable to use a pigment ink in terms of light resistance.

  Examples of water-soluble dye inks include direct dyes, acid dyes, basic dyes, and reactive dyes.

  As the pigment, organic pigments such as insoluble pigments and lake pigments, and carbon black can be preferably used. The insoluble pigment is not particularly limited. Dioxazine, thiazole, phthalocyanine, diketopyrrolopyrrole and the like are preferable. Specific pigments that can be preferably used include the following pigments.

  Examples of the magenta or red pigment 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. I. Pigment red 16, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 53: 1, C.I. I. Pigment red 57: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 123, C.I. 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. And CI Pigment Red 222.

  Examples of the pigment 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 94, C.I. I. And CI Pigment Yellow 138.

  Examples of the pigment for green or cyan include C.I. I. Pigment blue 15, C.I. I. Pigment blue 15: 2, C.I. I. Pigment blue 15: 3, C.I. I. Pigment blue 16, C.I. I. Pigment blue 60, C.I. I. And CI Pigment Green 7.

  These pigments may use a pigment dispersant as needed. Examples of the pigment dispersant that can be used include higher fatty acid salts, alkyl sulfates, alkyl ester sulfates, alkyl sulfonates, and sulfosuccinates. , Naphthalene sulfonate, alkyl phosphate, polyoxyalkylene alkyl ether phosphate, polyoxyalkylene alkyl phenyl ether, polyoxyethylene polyoxypropylene glycol, glycerin ester, sorbitan ester, polyoxyethylene fatty acid amide, amine oxide, etc. Activators, or styrene, styrene derivatives, vinyl naphthalene derivatives, acrylic acid, acrylic acid derivatives, maleic acid, maleic acid derivatives, itaconic acid, itaconic acid derivatives, fumaric acid, fumaric acid derivatives. Block copolymer comprising a body, it may be mentioned random copolymers and salts thereof.

  The method for dispersing the pigment is not particularly limited. For example, 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, a paint shaker, or the like is used. be able to.

  In order to remove the coarse particle component of the pigment dispersion according to the present invention, it is also preferable to use a centrifugal separator or a filter.

  The average particle diameter of the pigment particles in the pigment ink is appropriately selected in consideration of stability in the ink, image density, glossiness, light resistance, and the like.

(Water-soluble organic solvent)
The ink containing the colorant according to the present invention preferably uses a water-soluble organic solvent in combination.

  Examples of water-soluble organic solvents include alcohols (eg, 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 ether (E.g., ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, Tylene 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 mono 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.) ), Heterocyclic rings (for example, 2-pyrrolidone, N-methyl-2-pyrrolidone, cyclohexyl pyrrolidone, 2-oxazolidone, 1,3-dimethyl-2-imidazolidinone), sulfoxides (for example, dimethyl sulfoxide) , Sulfones (for example, sulfolane), urea, acetonitrile, acetone and the like. Preferable water-soluble organic solvents include polyhydric alcohols. Furthermore, it is particularly preferable to use a polyhydric alcohol and a polyhydric alcohol ether in combination.

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

  Examples of the surfactant that can be used in the ink containing the colorant according to the present invention include anionic surfactants such as dialkylsulfosuccinates, alkylnaphthalenesulfonates, fatty acid salts, and polyoxyethylene alkyl ethers. Nonionic surfactants such as polyoxyethylene alkyl allyl ethers, acetylene glycols, polyoxyethylene / polyoxypropylene block copolymers, and cationic surfactants such as alkylamine salts and quaternary ammonium salts . In particular, an anionic surfactant and a nonionic surfactant can be preferably used.

[Other additives used in inks containing colorants]
The ink composition containing the colorant according to the present invention includes thermoplastic resin fine particles for the purpose of improving ejection stability, print head and ink cartridge compatibility, storage stability, image storage stability, and other various performances. Viscosity modifiers, surface tension modifiers, specific resistance modifiers, film formers, dispersants, ultraviolet absorbers, antioxidants, fading inhibitors, antifungal agents, rust inhibitors, and the like can be added as appropriate.

[Physical properties of ink containing colorant]
The ink containing the colorant according to the present invention has a viscosity at the time of flight of preferably 10 mPa · s or less, and more preferably 5 mPa · s or less. The surface tension is preferably 20 mN / m or more, and more preferably 30 to 45 mN / m.

  The concentration of the colorant in the ink containing the colorant according to the present invention can be selected in the range of 0.1 to 10% by mass. In order to obtain a photographic image, so-called dark and light inks having different colorant concentrations are used. It is particularly preferable to use yellow, magenta, cyan and black dark and light inks, respectively. It is also preferable from the viewpoint of color reproducibility to use special color inks such as red, green, and blue as necessary.

[Drop volume of ink containing colorant]
The ink droplet amount of the ink containing the colorant according to the present invention is not particularly limited, but is preferably 1.0 to 10 pl, more preferably 2 pl to 8 pl.

[Colorless ink]
In the recording method of the present invention, the colorless ink containing a polymer that does not substantially contain a colorant and has a film-forming ability is substantially free of the colorant contained in the ink containing the colorant. It is. It is preferable that the change in chromaticity difference (ΔE) in the image portion is 3 or less depending on the presence or absence of colorless ink. The component contained in the colorless ink may be either uniformly dissolved or present in a non-uniform dispersion system. As the polymer having a film-forming ability, an aqueous resin that is dissolved or an aqueous resin that is dispersed is preferable.

  Further, when the ink containing the colorant and the colorless ink come into contact, it is preferable that the colorant contained in the ink containing the colorant does not insolubilize or aggregate. If the colorant in the ink containing the colorant is insolubilized or aggregated, the effect of improving the glossiness of the image is reduced, or the ink containing the colorant and the colorless ink come into contact with each other in the vicinity of the inkjet nozzle for some reason. Then, the problem that an insoluble matter and aggregate block | close an inkjet nozzle arises.

  As a polymer having a film-forming ability, examples of water-based resins in a dissolved state include, for example, polyvinyl alcohol, gelatin, polyethylene oxide, polyvinyl pyrrolidone, polyacrylic acid, polyacrylamide, polyurethane, dextran, dextrin, dextrin, κ, ι, λ Etc.), agar, pullulan, water-soluble polyvinyl butyral, hydroxyethyl cellulose, carboxymethyl cellulose and the like.

  Further, the aqueous resin is preferably a thermoplastic resin, for example, polycarbonate, polyacrylonitrile, polystyrene, polyacrylic acid, polymethacrylic acid, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, polyester, polyamide, Examples include polyethers, copolymers thereof, and salts thereof. Among them, styrene-acrylic acid ester copolymers, methacrylic acid ester-acrylic acid ester copolymers, vinyl chloride-vinyl acetate copolymers, vinyl chloride-acrylic. An acid ester copolymer, an ethylene-vinyl acetate copolymer, an ethylene-acrylic acid ester copolymer, and an SBR latex are preferable. The thermoplastic resin or fine particles thereof may be used by mixing a plurality of polymers having different monomer compositions, particle sizes, and polymerization degrees.

  The content of the film-forming polymer in the colorless ink is preferably adjusted to a range of 0.5 to 10% by mass because of restrictions on ink viscosity and ink adhesion amount.

  The method for supplying colorless ink to the recording paper is not particularly limited, but from the viewpoint of controllability, cost, etc., it is preferable to use an ink jet nozzle because of the necessity of forming fine droplets.

  The amount of ink droplets for supplying the colorless ink according to the present invention is selected from the range of 1.0 pl (picoliter) to 5.0 pl. When the amount of droplets exceeds 5.0 pl, the uniformity of the formed film is not sufficient, and the gloss and scratch resistance are poor. Further, even if the droplet amount is reduced to less than 1.0 pl, glossiness and scratch resistance are similarly deteriorated.

  At this time, the cause is not clear, but this is because the surface area is larger than the volume ratio when the amount of droplets is reduced, so volatile solvents such as water in colorless ink are very easy to evaporate. It is presumed that the film reaches the recording sheet with a high viscosity and cannot be leveled sufficiently, so that uniform film formation is not formed and gloss is not improved.

The colorless ink according to the present invention is ejected so as to form a protective film layer having a dry solid content of 0.05 to 0.3 g per m ² on recording paper. If the adhesion amount of the protective film layer is less than 0.05 g per 1 m ² , sufficient gloss cannot be obtained. Conversely, if the protective film layer exceeds 0.3 g, for example, about 1.0 g, rainbow-like interference occurs on the protective film layer. Stripes are generated, which is not preferable as an image texture. If it exceeds 1.0 g, the applied amount is so large that it exceeds the liquid viscosity that can be ejected. This causes a problem that ink overflows beyond the ink receiving capacity of the recording paper and spots occur.

  Since colorless ink is also preferably supplied from an inkjet nozzle, the ink composition, physical properties, and the like can be adjusted in the same manner as the ink containing the above-described colorant.

  Also, as a method of discharging colorless ink and forming a protective film layer, an image is formed with an ink containing a colorant, and simultaneously, a method of forming a film layer with a colorless ink and an image formation with an ink containing a colorant. After the process is completed, there is a method of forming a film layer with a colorless ink, but any method may be selected in the ink jet recording method of the present invention.

  In the inkjet image forming method of the present invention, the inkjet printer that discharges the ink containing the colorant and the colorless ink according to the present invention is not particularly limited, but an example thereof will be described with reference to FIG. The invention is not limited to this.

  FIG. 1 is a perspective view showing an example of an ink jet printer that simultaneously discharges an ink containing a colorant according to the present invention and a colorless ink.

  In FIG. 1, the recording head 22 for ink containing a colorant and the recording head 22 for colorless ink are used to print an image and form a protective coating layer using a carriage arranged in series.

  On the other hand, when an image is formed with an ink containing a colorant and then a protective film is formed with a colorless ink, another carriage equipped with a head for colorless ink is installed in the downstream part for conveying the recording paper, and the colorant A method of forming a protective film with colorless ink immediately after the image is formed with an ink containing the ink, and a method of forming a protective film by discharging only the colorless ink after setting the image on the printer again after forming the image. is there.

  Specifically, the recording head 22 may be any of a piezo method, a thermal method, and a continuous method, but the piezo method is preferable from the viewpoint of the stability of pigment ink and the like.

  Ink is supplied to each recording head 22 from a recording ink cartridge and a colorless ink cartridge (not shown) through a tube for piping. Eight recording heads 22 are arranged along the scanning direction, and are used for six colors of C, M, and K shades, Y, and colorless ink, respectively. FIG. 1 shows an example in which seven types of inks C, M, Y, K, LC, LM, and LK are used as recording inks.

  As the colorless ink medium, water and a water-soluble organic solvent are preferable. Examples of the water-soluble organic solvent 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 (eg ethylene glycol Methyl 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 monobutyl ether, ethylene glycol monophenyl ether, propylene glycol monophenyl ether, etc.), amines (eg, ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N- Tildiethanolamine, morpholine, N-ethylmorpholine, ethylenediamine, diethylenediamine, triethylenetetramine, tetraethylenepentamine, polyethyleneimine, pentamethyldiethylenetriamine, tetramethylpropylenediamine, etc.), amides (eg, formamide, N, N-dimethyl) Formamide, N, N-dimethylacetamide, etc.), heterocyclic rings (for example, 2-pyrrolidone, N-methyl-2-pyrrolidone, cyclohexylpyrrolidone, 2-oxazolidone, 1,3-dimethyl-2-imidazolidinone, etc.), Examples include sulfoxides (for example, dimethyl sulfoxide), sulfones (for example, sulfolane), urea, acetonitrile, acetone, and the like. Preferable water-soluble organic solvents include polyhydric alcohols. Furthermore, it is particularly preferable to use a polyhydric alcohol and a polyhydric alcohol ether in combination.

  One or more water-soluble organic solvents may be used in combination. The addition amount of the water-soluble organic solvent in the colorless ink is 5 to 60% by mass, preferably 10 to 35% by mass in total.

  Examples of the surfactant used in the colorless ink according to the present invention include anionic surfactants such as dialkylsulfosuccinates, alkylnaphthalenesulfonates, and fatty acid salts, polyoxyethylene alkyl ethers, and polyoxyethylene alkylallyl. Nonionic surfactants such as ethers, acetylene glycols, polyoxyethylene / polyoxypropylene block copolymers, and cationic surfactants such as alkylamine salts and quaternary ammonium salts. In particular, an anionic surfactant and a nonionic surfactant can be preferably used.

[Other additives used in colorless ink]
The colorless ink according to the present invention includes a viscosity adjusting agent, a surface tension adjusting agent, a ratio according to the purpose of improving ejection stability, print head and ink cartridge compatibility, storage stability, image storage stability, and other various performances. Resistance adjusting agents, film forming agents, dispersants, ultraviolet absorbers, antioxidants, anti-fading agents, antibacterial agents, rust inhibitors and the like can be added as appropriate.

[Inkjet recording paper]
As the recording paper used in the inkjet recording method of the present invention, conventionally known various recording papers can be applied. However, a type having an ink absorbing layer on a support is preferable from the viewpoint of the obtained image quality. There are gap type recording paper and swelling type recording paper.

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

<Preparation of pigment ink set>
(Preparation of pigment dispersion)
<Preparation of yellow pigment dispersion>
C. 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
100% by mass of ion-exchanged water The above additives are mixed, dispersed using a horizontal bead mill (System Zeta Mini, manufactured by Ashizawa) filled with 0.3 mm zirconia beads by volume, and yellow pigment dispersion Got the body. The average particle size of the obtained yellow pigment was 112 nm.

<Preparation of magenta pigment dispersion>
C. I. Pigment Red 122 25% by mass
Jonkrill 61 (acrylic-styrene resin, manufactured by Johnson)
18% by mass in solid content
Diethylene glycol 15% by mass
100% by mass of ion-exchanged water The above additives are mixed, dispersed using a horizontal bead mill (System Zeta Mini, manufactured by Ashizawa) filled with 0.3 mm zirconia beads at a volume ratio, and magenta pigment dispersion Got the body. The average particle size of the obtained magenta pigment was 105 nm.

<Preparation of cyan pigment dispersion>
C. I. Pigment Blue 15: 3 25% by mass
Jonkrill 61 (acrylic-styrene resin, manufactured by Johnson)
15% by mass as solid content
Glycerin 10% by mass
100% by mass of ion-exchanged water The above additives are mixed and dispersed using a horizontal bead mill (System Zetamini manufactured by Ashizawa Co., Ltd.) filled with 0.3% zirconia beads at a volume ratio of 60%. Got the body. The average particle diameter of the obtained cyan pigment was 87 nm.

<Preparation of black pigment dispersion>
Carbon black 20% by mass
Styrene-acrylic acid copolymer (molecular weight 7000, acid value 150) 10% by mass
Glycerin 10% by mass
100% by mass of ion-exchanged water The above additives are mixed, dispersed using a horizontal bead mill (System Zetamini, manufactured by Ashizawa) filled with 0.3% zirconia beads at a volume ratio of 60%, and black pigment dispersion Got the body. The average particle size of the obtained black pigment was 75 nm.

(Preparation of pigment ink set)
<Preparation of yellow dark ink>
Yellow pigment dispersion 15% by mass
20% by mass of ethylene glycol
Diethylene glycol 10% by mass
Surfactant (Surfinol 465 manufactured by Nissin Chemical Industry Co., Ltd.) 1% by mass
Amount to be 100% by mass of ion-exchanged water The above compositions were mixed, stirred, and filtered through a 1 μm filter to prepare a yellow dark ink which is an aqueous pigment ink of the present invention. The average particle diameter of the pigment in the ink was 120 nm, and the surface tension γ was 36 mN / m.

<Preparation of magenta dark ink>
Magenta pigment dispersion 15% by mass
20% by mass of ethylene glycol
Diethylene glycol 10% by mass
Surfactant (Surfinol 465 manufactured by Nissin Chemical Industry Co., Ltd.) 1% by mass
Amount to be 100% by mass of ion-exchanged water The above compositions were mixed, stirred, and filtered through a 1 μm filter to prepare a magenta dark ink that is the aqueous pigment ink of the present invention. The average particle size of the pigment in the ink was 113 nm, and the surface tension γ was 35 mN / m.

<Preparation of magenta light ink>
Magenta pigment dispersion 3% by mass
Ethylene glycol 25% by mass
Diethylene glycol 10% by mass
Surfactant (Surfinol 465 manufactured by Nissin Chemical Industry Co., Ltd.) 1% by mass
Amount to be 100% by mass of ion-exchanged water The above compositions were mixed, stirred, and filtered through a 1 μm filter to prepare a magenta light ink that is the aqueous pigment ink of the present invention. The average particle diameter of the pigment in the ink was 110 nm, and the surface tension γ was 37 mN / m.

<Preparation of cyan dark ink>
Cyan pigment dispersion 10% by mass
20% by mass of ethylene glycol
Diethylene glycol 10% by mass
Surfactant (Surfinol 465 manufactured by Nissin Chemical Industry Co., Ltd.) 1% by mass
Amount to be 100% by mass of ion-exchanged water The above compositions were mixed, stirred, and filtered through a 1 μm filter to prepare a cyan dark ink which is the aqueous pigment ink of the present invention. 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>
Cyan pigment dispersion 2% by mass
Ethylene glycol 25% by mass
Diethylene glycol 10% by mass
Surfactant (Surfinol 465 manufactured by Nissin Chemical Industry Co., Ltd.) 1% by mass
Amount to be 100% by mass of ion-exchanged water The above compositions were mixed, stirred, and filtered through a 1 μm filter to prepare a cyan light ink which is an aqueous pigment ink of the present invention. 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>
Black pigment dispersion 10% by mass
20% by mass of ethylene glycol
Diethylene glycol 10% by mass
Surfactant (Surfinol 465 manufactured by Nissin Chemical Industry Co., Ltd.) 1% by mass
Amount to be 100% by mass of ion-exchanged water The above compositions were mixed, stirred, and filtered through a 1 μm filter to prepare a dark black ink that is the aqueous pigment ink of the present invention. The average particle diameter of the pigment in the ink was 85 nm, and the surface tension γ was 35 mN / m.

<Preparation of black light ink>
Black pigment dispersion 2% by mass
Ethylene glycol 25% by mass
Diethylene glycol 10% by mass
Surfactant (Surfinol 465 manufactured by Nissin Chemical Industry Co., Ltd.) 1% by mass
Amount to be 100% by mass of ion-exchanged water The above compositions were mixed, stirred, and filtered through a 1 μm filter to prepare a black light ink which is the aqueous pigment ink of the present invention. The average particle size of the pigment in the ink was 89 nm, and the surface tension γ was 36 mN / m.

<< Preparation of colorless ink >>
[Preparation of colorless ink 1]
Thermoplastic resin (urethane resin, Tg 30 ° C, average particle size 80nm)
5% by mass as solid content
20% by mass of ethylene glycol
Diethylene glycol 10% by mass
Surfactant (Surfinol 465 manufactured by Nissin Chemical Industry Co., Ltd.) 1% by mass
Amount to be 100% by mass of ion-exchanged water The above compositions were mixed and stirred, filtered through a 1 μm filter, and a colorless ink 1 dispersed in an aqueous system of the present invention was prepared. The surface tension γ of the colorless ink 1 was 35 mN / m.

  Further, it was confirmed that even when the same amount of the colorless ink 1 and each pigment ink was mixed, there was no change in the average particle diameter of the pigment particles and no aggregation occurred.

[Preparation of colorless ink 2]
1% by mass of polyvinyl alcohol (PVA105 Kuraray Co., Ltd.)
20% by mass of ethylene glycol
Surfactant (Surfinol 465 manufactured by Nissin Chemical Industry Co., Ltd.) 1% by mass
Amount to be 100% by mass of ion-exchanged water The above compositions were mixed and stirred, filtered through a 1 μm filter, and colorless ink 2 dissolved in the aqueous system of the present invention was prepared. The colorless ink 2 had a surface tension γ of 36 mN / m. Further, even when the same amount of the colorless ink 2 and the pigment ink were mixed, it was confirmed that there was no change in the average particle diameter of the pigment particles and no aggregation occurred.

<Inkjet recording paper>
For image printing, “QP-pro photo gloss G (manufactured by Konica Photo Imaging)”, which is a gap type recording paper, was used.

<Inkjet recording device>
As shown in FIG. 1, the ink droplet amount per discharge operation can be adjusted, and Y, M, C, K and LM (light magenta), LC (light cyan), and LK (light black) are used as recording ink. A piezo-type ink jet recording apparatus equipped with the recording heads of the 7-color ink and colorless ink was prepared. Each pigment ink formed an image with a droplet amount of 4 pl and a recording resolution of 1280 × 1280 dpi (dpi: representing the number of dots per 2.54 cm).

  For the colorless ink, the droplet amount and the adhesion amount to the recording paper can be variably controlled, the recording resolution is 2880 × 2880 dpi, and the colorless ink is ejected simultaneously with the production of the recorded image or after the image formation. In the case of ejection after image formation, the recording paper after image formation with pigment ink was set again in the printer, and colorless ink was ejected.

  Images 1 to 13 were prepared using the combinations shown in Table 1 for the types of colorless ink, the printing range, the amount of droplets, the amount of adhesion, and the thickness of the protective film formed from the colorless ink.

  The ink jet recording apparatus used for the printing will be described with reference to FIG.

  The recording head 22 may be any of a piezo method, a thermal method, and a continuous method, but the piezo method is used from the viewpoint of the stability of the pigment ink.

  Ink is supplied to each recording head 22 from a recording ink cartridge and a colorless ink cartridge (not shown) through a tube for piping. Eight recording heads 22 are arranged in the carriage 23 along the scanning direction, and are used for C, M, and K shades of 6 colors, Y, and colorless ink, respectively. In this embodiment, seven types of inks C, M, Y, K, LC, LM, and LK are used as the recording ink.

<Evaluation of formed image>
The following evaluations were performed on the images formed as described above.

[Glossiness evaluation]
For a solid black image provided with a protective film, the C value (%) was measured at 60 degrees reflection with an image clarity measuring instrument ICM-1DP (manufactured by Suga Test Machine Co., Ltd.) and with an optical comb of 2 mm, and this was used as a measure of gloss .

[Evaluation of rainbow unevenness and overflow]
The black solid image provided with the protective film was visually observed, and rainbow unevenness and overflow were evaluated according to the following criteria.

◎: Neither rainbow unevenness nor overflow are observed even at close distance observation ○: If the observation distance is 30 cm or more, neither rainbow unevenness nor overflow is observed △: Rainbow unevenness is observed ×: Overflow is recognized [ (Evaluation of ozone fading resistance)
A person portrait image is created under the above conditions, and this image is left in an environment with an ozone concentration of 50 ppm (25 ° C., 50%) for 10 days. The image after fading and the image before fading are visually compared, Evaluation of ozone fading resistance was performed in accordance with the above criteria.

◎: Before and after the fading process, there is no change in both the dark color part and the light color part. Later, both the dark and light color areas drop dramatically (evaluation of scratch resistance)
When the created portrait image was rubbed 10 times with an eraser (MONO, manufactured by Dragonfly Pencil Co., Ltd.), the change in the density of the image area was visually observed, and the scratch resistance was evaluated according to the following criteria. Went.

◎: No change in both dark and light color portions ○: Slightly decreased density in both dark color and light color portions △: Reduced density in dark color portion ×: Reduced density in both dark and light color portions The results obtained are shown in Table 1.

As is apparent from Table 1, after forming an image with an ink containing a colorant, the colorless ink has a droplet amount of 1 pl (picoliter) to 5 pl, and a dry solid content of 0.05 per 1 m ^{2 of} recording paper. The image produced by the ink jet recording method of the present invention in which a protective film layer of .about.0.3 g is formed on the entire surface of the printed image has higher gloss than the comparative example, and rainbow unevenness and overflow occur. It can be seen that it is excellent in ozone fading resistance and scratch resistance.

It is a perspective view which shows an example of the inkjet printer used with the inkjet recording method of this invention.

Explanation of symbols

22 Recording head 23 Carriage

Claims (5)

Inkjet recording in which an image is formed on an inkjet recording paper with an ink containing a colorant, and then a colorless ink containing a polymer having a film-forming ability and containing substantially no colorant is ejected onto the image. In the method, a protective film layer having a colorless ink droplet amount of 1.0 to 5.0 pl (picoliter) and a dry solid content of 0.05 to 0.3 g per 1 m ^{2 of the} inkjet recording paper is formed. An ink jet recording method characterized by forming the image on the entire surface of a substantially printed image. 2. The ink jet recording method according to claim 1, wherein the film-forming polymer in the colorless ink contains a water-based dissolved resin or a water-based dispersed resin. 3. The ink jet recording method according to claim 1, wherein insolubilization or aggregation of the colorant does not occur even when the ink containing the colorant and the colorless ink come into contact with each other. The inkjet recording method according to claim 1, wherein the colorant of the ink containing the colorant is a pigment. A recorded matter, wherein an image is formed by the ink jet recording method according to claim 1.

Images