JP2006272934A - Ink jet recording method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink jet recording method which provides a recorded matters excellent in a glossiness and scratch resistance of a printing part with extremely reduced gloss irregularity. <P>SOLUTION: By using a color ink containing a pigment as a colorant and a clear ink which does not contain the colorant and contains at least polyurethane resin and water, discharge amounts of the color ink and the clear ink are adjusted so that a sticking amount of a resin component derived from the ink per unit area in a recorded area of a recording medium becomes uniform in the whole area of the recorded area. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ink jet recording method using a color ink containing a colorant and a clear ink not containing a colorant.

  The inkjet recording method is a printing method in which recording is performed by flying ink droplets and attaching them to a recording medium such as paper. Due to recent advances in inkjet recording technology, the inkjet recording method has been applied to the field of high-definition printing that has been realized only by silver salt photography and offset printing. In addition, the inkjet recording method is applied to glossy paper having high gloss such as photographic paper and art paper. Furthermore, in recent years, ink-jet prints printed with an ink-jet printer are often used not only indoors but also for outdoor use for advertising and ornamental purposes. Ink-jet prints are often used for light resistance, gas resistance, water resistance. It has been required to have excellent characteristics such as stability and excellent storage stability.

  Conventionally, dye inks using dyes as colorants have been mainstream as inks for ink jet recording, but dye inks have the disadvantages of being inferior in light resistance, gas resistance and water resistance. In recent years, pigment inks using pigments having excellent characteristics as compared with dyes as colorants have been used. A pigment ink for inkjet recording is usually a pigment dispersion in which pigment particles are uniformly dispersed in an aqueous solvent, and after recording, an ink film containing the pigment particles is formed on a recording medium. The image quality of the recorded matter by the pigment ink is greatly influenced by the color development and gloss of the pigment particles themselves in the ink film. When plain paper is used, a recorded matter having good color development and glossiness can be obtained. In the case of using a recording medium with a smooth recording surface such as glossy paper, there is a problem that the color developability and glossiness of the recording portion are impaired due to irregular reflection of light by the pigment particles in the ink film. there were. Further, the conventional pigment ink has a problem that the fixing property to a recording medium is insufficient, and an image formed using the pigment ink has poor abrasion resistance.

  For such problems, Patent Document 1 discloses an aqueous dispersion of polymer particles of a water-insoluble vinyl polymer containing a pigment as a pigment ink capable of printing with excellent color developability, glossiness, and abrasion resistance. The water-based ink used is disclosed. However, although this water-based ink can achieve a certain level of color developability in the printed part, it cannot be said that it can sufficiently meet the demands from the user side regarding glossiness and still has excellent glossiness. At present, there is a demand for an ink jet recording technique that can provide a printed portion.

  Further, when recording is performed using a pigment ink containing a resin component as disclosed in Patent Document 1, a high duty area having a large ink adhesion amount is high due to a large amount of the resin component. In contrast to the glossiness, the low-duty area with a small amount of ink adhesion has a low glossiness, and the non-printing area to which no ink is adhered has a lower glossiness. As described above, when the ink containing the resin component is used, a difference in glossiness of the recorded matter is caused depending on the amount of the resin component adhering, and the recording quality is adversely affected as uneven glossiness. Become. Such gloss unevenness is a problem particularly in inkjet glossy paper that has been developed so that a photo-like high-definition image quality of silver salt photographic tone can be obtained.

JP 2004-75988 A

  Accordingly, an object of the present invention is to provide an ink jet recording method capable of providing a recorded matter which is excellent in glossiness and abrasion resistance of a printing portion and in which gloss unevenness is greatly reduced.

  The present invention is an ink jet recording method for forming an image by ejecting a color ink containing a pigment as a colorant and a clear ink not containing a colorant toward a recording area of a recording medium, the clear ink Includes at least a polyurethane resin and water, and the discharge amount of the color ink and the clear ink is determined so that the adhesion amount of the resin component derived from the ink per unit area in the recording area is in the entire recording area. The above object is achieved by providing an ink jet recording method in which adjustment is made to be uniform.

  According to the present invention, together with a color ink containing a pigment as a colorant, a clear ink having a specific composition not containing a colorant is used, and the discharge amount of each ink is determined by the unit area of the resin component contained in both the inks. Since the amount of adhesion to the recording area is adjusted to be uniform over the entire recording area, the characteristics of the pigment ink (excellent light resistance, gas resistance, and water resistance) are utilized, and the printing portion Recorded matter with excellent glossiness and abrasion resistance and greatly reduced gloss unevenness can be obtained.

  In the inkjet recording method of the present invention, a color ink containing a pigment as a colorant and a clear ink not containing a colorant are used. Hereinafter, these inks will be described.

  As the pigment (colorant) contained in the color ink according to the present invention, various pigments conventionally used in inks for inkjet recording can be used. For example, azo pigments (including azo lakes, insoluble azo pigments, condensed azo pigments, chelate azo pigments, etc.), polycyclic pigments (for example, phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, thioindigo Pigments, isoindolinone pigments, quinophthalone pigments, etc.), nitro pigments, nitroso pigments, organic pigments such as aniline black; carbon blacks (eg furnace black, thermal lamp black, acetylene black, channel black, etc.), metal oxides, metals Inorganic pigments such as sulfides and metal chlorides; extender pigments such as silica, calcium carbonate and talc can be used as colorants.

  As the organic pigment used in the chromatic color ink, preferable yellow pigments include C.I. I. Pigment yellow 74, 93, 109, 110, 128, 138, 150, 151, 154, 155, 180, 185, and the like. Pigment yellow 74 is particularly preferable. Preferred magenta pigments include C.I. I. Pigment red 122, 202, 209 and C.I. I. Pigment violet 19 and the like. I. Pigment Red 122 and Pigment Violet 19 are preferable. Further, as a preferable cyan pigment, C.I. I. Pigment blue 15: 3, 15: 4, 60, and the like. I. Pigment Blue 15: 3 and Pigment Blue 15: 4 are preferred. Examples of organic pigments used for chromatic color inks other than yellow, cyan, and magenta include C.I. I. Pigment green 7 (phthalocyanine green), 10 (green gold), 36, 37; C.I. I. Pigment brown 3, 5, 25, 26; I. Pigment Orange 1, 2, 5, 7, 13, 14, 15, 16, 34, 36, 38, etc. can be used.

  The content of the pigment (colorant) is preferably 5 to 20% by weight with respect to the total weight of the color ink from the viewpoint of the balance between the image density and the ejection stability.

  The color ink according to the present invention contains water as a main solvent as an essential component in addition to the pigment. As this water, pure water such as ion exchange water, ultrafiltration water, reverse osmosis water, distilled water, or ultrapure water can be used. In addition, water sterilized by ultraviolet irradiation or addition of hydrogen peroxide is preferable because it can prevent generation of mold and bacteria when the ink is stored for a long period of time.

  The color ink according to the present invention preferably contains a resin (pigment dispersion resin) as a pigment dispersant from the viewpoint of enhancing the dispersion stability of the pigment. As the pigment dispersion resin, those similar to those used as a dispersant in this type of aqueous pigment ink can be used. For example, polyvinyl alcohols; polyvinyl pyrrolidones; polyacrylic acid, acrylic acid-acrylonitrile copolymer Acrylic resins such as coalescence, potassium acrylate-acrylonitrile copolymer, vinyl acetate-acrylic ester copolymer, acrylic acid-alkyl acrylate copolymer; styrene-acrylic acid copolymer, styrene-methacrylic acid Styrene such as copolymer, styrene-methacrylic acid-acrylic acid alkyl ester copolymer, styrene-α-methylstyrene-acrylic acid copolymer, styrene-α-methylstyrene-acrylic acid-acrylic acid alkyl ester copolymer -Acrylic acid copolymer; Styrene-Male Inic acid copolymer; Styrene-maleic anhydride copolymer; Vinyl naphthalene-acrylic acid copolymer; Vinyl naphthalene-maleic acid copolymer; Vinyl acetate-ethylene copolymer, Vinyl acetate-Fatty acid vinyl ethylene copolymer , Vinyl acetate-maleic acid ester copolymer, vinyl acetate-crotonic acid copolymer, vinyl acetate-based copolymer such as vinyl acetate-acrylic acid copolymer, or salts thereof; glue, gelatin, casein, albumin Natural rubbers such as gum arabic and tragacanth; glucosides such as saponin; alginic acid derivatives such as alginic acid and propylene glycol alginate, triethanolamine alginate, ammonium alginate; methylcellulose, carboxymethylcellulose, hydroxyethyl Cellulose, and cellulose derivatives such as ethyl hydroxyethyl cellulose. In this invention, these 1 type can be used individually or in mixture of 2 or more types.

  The content of the pigment-dispersed resin is preferably 10 to 50 parts by weight with respect to 100 parts by weight of the pigment (colorant) from the viewpoint of achieving both pigment dispersion stability, gloss of printed parts, and prevention of bronzing. Yes, more preferably 10 to 35 parts by weight.

  In addition, the color ink according to the present invention preferably contains a water-soluble organic solvent from the viewpoint of improving the permeability to a recording medium and preventing clogging in a recording head in an ink jet printer due to drying of the ink. . Examples of the water-soluble organic solvent include alkanediols such as 1,2-pentanediol and 1,2-hexanediol; ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono Glycol ethers such as butyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether; ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, propylene glycol, butylene glycol, 1, 2 , 6-hexanetriol, thiodiglycol, hex Polyhydric alcohols such as ethylene glycol, glycerin, trimethylolethane, trimethylolpropane; urea, 2-pyrrolidone, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, triethanolamine, sugar Examples include saccharides such as alcohol. In this invention, these 1 type can be used individually or in mixture of 2 or more types.

  The content of the water-soluble organic solvent is not particularly limited, but is usually about 0.1 to 30% by weight with respect to the total weight of the ink.

  Further, in the color ink according to the present invention, various surfactants such as acetylene glycol compounds and polysiloxane compounds, pH adjusters such as triethanolamine, preservatives and fungicides, chelating agents, Antioxidants, conductivity modifiers, viscosity modifiers, surface tension modifiers, oxygen absorbers and the like can be included.

  The color ink according to the present invention preferably has a pH in the range of 8.0 to 11. The same applies to the pH of the clear ink described later. By adjusting the pH of the ink within such a range, a more excellent gloss feeling can be realized. A pH adjuster is suitable for adjusting the pH of the ink.

  The clear ink according to the present invention is a substantially colorless ink that does not contain a colorant, and includes at least a polyurethane resin and water. As the water, the same water as the main solvent in the color ink described above can be used.

  The polyurethane resin is a substance that is particularly effective for improving the glossiness and abrasion resistance of the printed part, and is a resin containing a polymer obtained by reacting a diisocyanate compound and a diol compound. Examples of the diisocyanate compound include araliphatic diisocyanate compounds such as hexamethylene diisocyanate and 2,2,4-trimethylhexamethylene diisocyanate, aromatic diisocyanate compounds such as toluylene diisocyanate and phenylmethane diisocyanate, and modified products thereof. Can be mentioned. Examples of the diol compound include polyethers such as polyethylene glycol and polypropylene glycol, polyesters such as polyethylene abido and polybutylene abates, and polycarbonates. In the present invention, the polyurethane resin preferably has a carboxyl group.

The polyurethane resin preferably has at least one of the following characteristics in consideration of glossiness and abrasion resistance of the printed part and storage stability of the ink, and has all the following characteristics: More preferred is.
Acid value (mg amount of KOH necessary for neutralizing 1 g of resin): preferably 10 to 300, more preferably 20 to 100.
-Weight average molecular weight (Mw): Preferably it is 100-200,000, More preferably, it is 1000-50,000. In addition, Mw said here is the weight average molecular weight of the polyurethane resin before bridge | crosslinking. Mw can be measured using, for example, GPC (gel permeation chromatography).
-Glass transition temperature (Tg, measured according to JIS-K6900): preferably -50 to 200 ° C, more preferably -50 to 100 ° C.

  The polyurethane resin is usually dispersed in the form of particles in the ink, and the maximum particle size of the polyurethane resin particles is preferably 0.3 μm or less, particularly 0.2 μm or less, especially 0.1 μm or less. This is preferable from the viewpoint of improving gloss and rubbing resistance of the printed portion and storage stability of the ink.

  The content of the polyurethane resin is preferably 0.5 to 10 weights with respect to the total weight of the clear ink from the viewpoint of the balance between the gloss and rub resistance of the printed portion and the storage stability of the ink, and prevention of bronzing. %, More preferably 1 to 5% by weight.

  In addition to the above-mentioned polyurethane resin and water, the clear ink according to the present invention may further contain 1,2-hexanediol. 1,2-Hexanediol is effective in improving the glossiness of the printed portion, and is also effective in eliminating inconveniences that are a concern when a polyurethane resin is used as an ink component. That is, when a polyurethane resin is contained in the ink, the polyurethane molecular chain may be hydrolyzed due to environmental factors such as high temperature and alkaline conditions. As a result, the viscosity of the ink changes with time, resulting in the viscosity of the ink. The use of 1,2-hexanediol together with the polyurethane resin may cause the hydrolysis of polyurethane molecular chains, where adjustment may be difficult and ink ejection stability and storage stability may decrease. As a result, the viscosity of the ink can be stabilized over a long period of time, and good ejection stability and storage stability can be obtained. In order to ensure the effect of improving the ink ejection stability and storage stability by 1,2-hexanediol, it is preferable to perform a predetermined heat treatment during the production of the ink. This heat treatment will be described later.

  The content of 1,2-hexanediol is preferably 1 to 20% by weight, more preferably 1 to 10% by weight, which improves the glossiness of the printed part, the ink ejection stability and the storage stability. Effective in terms.

  The clear ink according to the present invention may contain a copolymer resin of a hydrophobic monomer and a hydrophilic monomer and a crosslinking agent. As a result, the polyurethane resin and the copolymer resin are cross-linked by the cross-linking agent, so that the glossiness of the printed portion can be further enhanced.

  Specific examples of the hydrophobic monomer include, for example, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, n-propyl acrylate, n-propyl methacrylate, iso-propyl acrylate, iso-propyl methacrylate, n-butyl acrylate, n -Butyl methacrylate, sec-butyl acrylate, sec-butyl methacrylate, tert-butyl acrylate, tert-butyl methacrylate, n-hexyl acrylate, n-hexyl methacrylate, n-octyl acrylate, n-octyl methacrylate, iso-octyl acrylate, iso -Octyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, decyl acrylate, decyl methacrylate, lauryl acrylate , Lauryl methacrylate, stearyl acrylate, stearyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 2-dimethylaminoethyl acrylate, 2-dimethylaminoethyl methacrylate, 2- Ethylaminoethyl acrylate, 2-diethylaminoethyl methacrylate, glycidyl acrylate, glycidyl methacrylate, allyl acrylate, allyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, phenyl acrylate, phenyl methacrylate, nonyl phenyl acrylate, nonyl phenyl methacrylate, benzyl acrylate, benzyl methacrylate Dicyclopentenyl acrylate, dicyclopentenyl methacrylate, bornyl acrylate, bornyl methacrylate, 1,3-butanediol diacrylate, 1,3-butanediol dimethacrylate, 1,4-butanediol diacrylate, 1, 4-butanediol dimethacrylate, ethylene glycol diacrylate, ethylene glycol dimethacrylate, diethylene glycol diacrylate, diethylene glycol dimethacrylate, triethylene glycol diacrylate, triethylene glycol dimethacrylate, tetraethylene glycol diacrylate, tetraethylene glycol dimethacrylate, polyethylene Glycol diacrylate, polyethylene glycol dimethacrylate, neopen Diglycol diacrylate, 1,6-hexanediol diacrylate, 1,6-hexanediol dimethacrylate, dipropylene glycol diacrylate, dipropylene glycol dimethacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, glycerol acrylate, Examples thereof include glycerol methacrylate, styrene, methyl styrene, vinyl toluene and the like.

  Specific examples of the hydrophilic monomer include acrylic acid, methacrylic acid, maleic acid, itaconic acid and the like.

  Particularly preferred copolymer resins of the hydrophobic monomer and the hydrophilic monomer are styrene- (meth) acrylic acid copolymer resins, styrene-methylstyrene- (meth) acrylic acid copolymer resins, and styrene-maleic acid copolymers. Resin, (meth) acrylic acid- (meth) acrylic acid ester copolymer resin, and styrene- (meth) acrylic acid- (meth) acrylic acid ester copolymer resin.

  The content of the copolymer resin is preferably 0.5 to 10% by weight, based on the total weight of the clear ink, from the viewpoint of the balance between the glossiness of the printed portion and the ejection stability and storage stability. More preferably, it is 1 to 5% by weight.

  As the crosslinking agent, an epoxy resin having a glycidyl ether skeleton or a resin having an oxazoline group is preferably used. Among these, a resin that reacts with a carboxyl group (carboxyl group attacking resin) is particularly preferable. Examples of the carboxyl group attacking resin include a polycarbodiimide type having a carbodiimide group in the molecule, an oxazoline type having an oxazoline group in the molecule, and an aziridine type.

The content of the cross-linking agent is preferably 1 to 50% by weight with respect to the polyurethane resin from the viewpoint of the balance between the glossiness of the printed part and the ejection stability and storage stability.
In addition, the effective solid content weight ratio [crosslinking agent / (copolymer resin + polyurethane resin)] in the clear ink according to the present invention is preferably in the range of 1/100 to 50/100, and preferably 1/100 to 40 / More preferably, it is in the range of 10.
0.

  In addition to the above-mentioned various components, the clear ink according to the present invention appropriately contains the same components as those that can be contained in the color ink, such as a water-soluble organic solvent, a surfactant, and a pH adjuster, as necessary. Can be made.

  The clear ink according to the present invention can be produced according to the production method of this type of water-based pigment ink, similarly to the color ink, but when 1,2-hexanediol is contained as described above. In order to ensure the effect of improving the ink ejection stability and storage stability by 1,2-hexanediol, it is preferable to introduce a heat treatment into the ink production process. Specifically, first, a polyurethane resin is dispersed in a solvent, and if necessary, a copolymer resin and a crosslinking agent are further added to perform a crosslinking treatment to prepare a resin dispersion. Next, after adding a predetermined amount of 1,2-hexanediol to the resin dispersion, the resin dispersion is subjected to heat treatment. In the heat treatment, the heating temperature is preferably 60 to 70 ° C., and the heating time is preferably 3 to 7 days. The clear ink according to the present invention can be obtained by mixing the heated resin dispersion thus obtained and a solvent to which a surfactant, a pH adjuster or the like is added as necessary.

  Thus, “a heated resin dispersion obtained by subjecting a resin dispersion containing at least polyurethane resin, 1,2-hexanediol, a copolymer resin of a hydrophobic monomer and a hydrophilic monomer, and a crosslinking agent to heat treatment,” Since the "clear ink containing" suppresses hydrolysis of polyurethane molecular chains, the ink viscosity does not substantially change over a long period of time, and exhibits good ejection stability and storage stability.

  The ink jet recording method of the present invention uses the above-described color ink and clear ink, and discharges these inks toward a recording area in a recording medium such as paper to form an image. The number and type (color) of the color ink are not particularly limited, and one or more kinds of color inks arbitrarily selected can be used.

  In the inkjet recording method of the present invention, the discharge amounts of the color ink and the clear ink are adjusted so that the adhesion amount of the resin component derived from the ink per unit area is uniform over the entire recording area. In a conventional inkjet recording method, that is, a method of forming an image by discharging only color inks such as cyan, magenta, yellow, and black according to image data without using clear ink, the discharge amount per unit area of ink is Depending on the difference, there was a difference in the adhesion amount of the resin component derived from the ink per unit area (the resin component originally contained in the ink, such as pigment dispersion resin), which was the main cause of uneven gloss. In the present invention, the clear ink is used in combination with the color ink, and the resin component is replenished by discharging a relatively large amount of the clear ink to a location where the adhesion amount of the resin component derived from the color ink is relatively small. The adhesion amount of the resin component derived from the ink per area is made uniform over the entire recording area, and gloss unevenness is greatly reduced.

  The ink discharge amount is preferably adjusted by adjusting the clear ink discharge amount in accordance with the duty of the color ink. Specifically, the clear ink discharge amount is relatively increased in areas where the color ink duty is relatively low, and the clear ink discharge amount is relatively increased in areas where the color ink duty is relatively high. By reducing the amount, the ejection amount of each ink is adjusted. In this adjustment method, the clear ink discharge amount is maximized for the minimum duty region of color ink, the clear ink discharge amount is minimized for the maximum duty region of color ink, and the resin component adhesion amount from the ink in the minimum duty region It is preferable that the ink-derived resin component adhesion amount in the maximum duty region is substantially matched. Regarding the intermediate region between the lowest duty region and the highest duty region of the color ink, it is preferable that the duty of the color ink and the duty of the clear ink are in an inversely proportional relationship.

  In the present invention, “duty” is a value calculated by the following equation. Duty (%) = actual print dots / (vertical resolution x horizontal resolution) x 100 where "actual print dots" is the actual print dots per unit area, and "vertical resolution" and "horizontal resolution" are Each is a resolution per unit area. A duty of 100% means the maximum ink weight of a single color for a pixel.

The above-described inkjet recording method of the present invention can be carried out, for example, as follows.
First, image data (for example, image data that conforms to the RGB color system) acquired by shooting with a digital camera is used to convert the color ink to a color that matches the color ink used in the inkjet printer. Color conversion processing and halftone processing are performed to generate primary print data.

  Next, the duty of the color ink is calculated for each predetermined area based on the primary print data. At that time, for a region where a plurality of color inks are used, the total duty of each color ink is set as the duty of the color ink in the region.

  Next, the discharge amount of the clear ink is determined based on the duty of the color ink in the predetermined region thus obtained. In this determination process, for example, “a clear ink discharge amount is relatively increased in a region where the color ink duty is relatively low, and a clear ink discharge amount is set in a region where the color ink duty is relatively high. The LUT with the content “relatively reduce” is referred to, and the discharge amount of the clear ink is determined for each predetermined area based on the content. Then, the determined discharge amount of the clear ink is converted into a duty, and secondary print data is generated.

  The primary print data (color ink print data) and secondary print data (clear ink print data) generated in this way are rearranged in the printing order, and predetermined information is added as necessary and transmitted to the ink jet printer. Then, using this ink jet printer as usual, the color ink and the clear ink are respectively ejected from the recording head of the ink jet printer and adhered onto the recording area of the recording medium, whereby the image indicated by the image data is displayed. Thus, it is possible to obtain an image having excellent glossiness and rubbing resistance of the printed portion and greatly reduced gloss unevenness.

  In the ink jet recording method of the present invention, the color ink and the clear ink may be ejected during the same processing. “At the same time” refers to the time of processing so as to form one specific image with both color ink and clear ink in one recording (one pass), and both inks are ejected at the same time. In addition, the case where the color ink and the clear ink are ejected in the order of one pass, or the case where the clear ink and the color ink are ejected in the order of one pass, is included in the “same processing”.

  The ink jet recording method of the present invention can be applied without particular limitation as long as it is a recording medium capable of ink jet recording, and is particularly effective for so-called glossy paper having a high surface gloss on the recording surface. It is possible to output an image that is excellent in gloss of the printed portion and in which gloss unevenness is greatly reduced. Glossy papers that are effective in the present invention include glossy type inkjet recording papers that are generally marketed as ink jet dedicated papers, as well as CD-Rs, CD-ROMs, CDs that are provided with a surface glossy layer capable of ink jet recording. -Optical disks such as RW and DVD-RAM. The present invention is particularly effective when glossy paper having a 20 ° glossiness of 10% or more as defined in JIS-Z8741 on the recording surface is used.

  Hereinafter, the present invention will be described more specifically with reference to examples of the present invention and test examples showing the effects of the present invention. However, the present invention is not limited to the examples.

(Preparation of color ink)
7 parts by weight of styrene-methylstyrene-acrylic acid copolymer resin (pigment dispersion resin, Mw = 8000) is dissolved in 45 parts by weight of methyl ethyl ketone, and a neutralizer (20% by weight aqueous sodium hydroxide solution) is placed therein. A fixed amount was added for neutralization, and the following pigment (colorant) was further added in the following amount, followed by kneading for 2 hours in a bead mill. Then, after adding 110 parts by weight of ion-exchanged water to the kneaded product and stirring, methyl ethyl ketone is removed, and a part of the water is further removed to obtain pigment dispersions for cyan, magenta, and yellow color inks (whichever Also obtained a solid concentration of 20% by weight.
・ For cyan ink: C.I. I. Pigment Violet 19 20 parts by weight for magenta ink C.I. I. Pigment Red 122 20 parts by weight for yellow ink C.I. I. Pigment Yellow 74 20 parts by weight

  Using the pigment dispersion obtained above, three color inks of cyan, magenta and yellow having the following composition were prepared according to a conventional method.

<Color ink>
・ Pigment dispersion 5% by weight
・ Triethanolamine 1% by weight
・ Glycerin 15% by weight
・ Triethylene glycol 2% by weight
・ Triethylene glycol monobutyl ether 1% by weight
・ 1,2-hexanediol 3% by weight
・ Surfactant (Olfin E1010, manufactured by Nissin Chemical Industry) 1% by weight
・ Pure water balance

(Preparation of clear ink 1)
The following various components were charged into a stirrer at the following blending ratio and stirred at 90 ° C. for 5 hours to obtain a resin dispersion A.

<Resin dispersion A>
Polyester polyurethane resin (acid value 50, Mw = 50,000) 10 parts by weight Styrene-methylstyrene-acrylic acid copolymer resin 2 parts by weight (Mw = 8000)
・ Crosslinking agent (epoxy resin based on glycidyl ether) 8 parts by weight ・ Pure water balance

  To the resin dispersion A thus obtained, 1,2-hexanediol was added in an amount of 5% by weight based on the dispersion A, and after sufficient stirring, heat treatment was performed at a heating temperature of 70 ° C. for 3 days. A heated resin dispersion A was obtained. Then, using this heated resin dispersion A, a clear ink 1 (Example Production Example 1) having the following composition was prepared.

<Clear ink 1>
-Heated resin dispersion A 5% by weight
・ Glycerin 15% by weight
・ Surfactant (BYK-348, manufactured by Big Chemie Japan) 0.5% by weight
・ Triethanolamine 0.9% by weight
・ Pure water balance

(Preparation of clear ink 2)
The above (Preparation of Clear Ink 1) except that in the above (Preparation of Clear Ink 1), the resin dispersion B having a composition obtained by removing the styrene-methylstyrene-acrylic acid copolymer resin and the crosslinking agent from the resin dispersion A was used. Preparation was performed in the same manner as described above, and the obtained ink was designated as clear ink 2 (Example Production Example 2).

(Preparation of clear ink 3)
In the above (Preparation of Clear Ink 1), preparation was performed in the same manner as in the above (Preparation of Clear Ink 1) except that no heat treatment was performed, and the obtained ink was designated as Clear Ink 3 (Example Production Example 3).

(Preparation of clear ink 4)
In the above (Preparation of Clear Ink 1), preparation was performed in the same manner as in the above (Preparation of Clear Ink 1) except that 1,2-hexanediol was not added to the resin dispersion A and no heat treatment was performed. The obtained ink was designated as clear ink 4 (Example Production Example 4).

(Preparation of clear ink 5)
A clear ink 5 (Comparative Production Example 1) having the following composition containing no polyurethane resin was prepared.
<Clear ink 5>
・ Styrene-methylstyrene-acrylic acid copolymer resin 10% by weight
(Mw = 8000)
・ 1,2-hexanediol 5% by weight
・ Glycerin 15% by weight
・ Surfactant (BYK-348, manufactured by Big Chemie Japan) 0.5% by weight
・ Pure water balance

(Evaluation test of clear ink ejection stability)
About the said clear inks 1-5, the ejection stability evaluation test was done in the following way. First, replace the clear ink with the yellow ink that is standard on inkjet printers (manufactured by Seiko Epson, PM-G900), perform printing using the clear ink, and ensure that the clear ink is ejected stably. confirmed. Next, this ink jet printer was left for 4 weeks in an environment of room temperature 50 ° C. and relative humidity 40% with the recording head removed from the home position. Next, the ink jet printer was placed in a normal indoor environment, and when the printer temperature was almost the same as room temperature, the printer was turned on and printing was performed. The ink discharge state at this time was visually observed, and a predetermined cleaning operation was performed on the recording head as necessary. Then, A (discharging stability is good) when the discharge is performed extremely stably and no cleaning operation is required, and within 2 times until the discharge is a little unstable and stable discharging is performed. B is required for the cleaning operation, C is required for the cleaning operation 3 to 5 times until stable discharge is performed, the discharge is unstable, and the cleaning operation is performed 6 times or more. D was not stable. The results are shown in Table 1 below.

  Glossy ink jet recording paper (manufactured by Seiko Epson Corporation) is mounted on an ink jet printer (PX-G900 manufactured by Seiko Epson Corporation) with the above three color inks of cyan, magenta, and yellow and the clear ink 1. Each ink is ejected at the same processing at a resolution of 1440 × 720 dpi on a PM photographic paper, a recording surface of the recording surface having a 20-degree glossiness of 15% defined by JIS-Z8741 and the following recording pattern ( Recording was performed according to 1) to (3) to prepare a recorded matter.

(1) Recording pattern 1 (Example 1): The clear ink discharge amount is increased in the region where the color ink duty is low, and the clear ink discharge amount is decreased in the region where the color ink duty is high. . Specifically, the color ink duty is set to 10% from 0 to 100%, and each of the three color inks is ejected individually, and the duty of the clear ink is set to 10% from 100 to 0%. The total duty of the color ink and the clear ink was made 100% uniform.
(2) Recording pattern 2 (Comparative example 1): The same as recording pattern 1 except that clear ink was not used.
(3) Print pattern 3 (Comparative example 2); Print pattern 1 except that the duty of the clear ink is uniformly 10% and the total duty of the color ink and the clear ink in each region is 10 to 110%. The same was done.

  The printed matter thus produced was evaluated by the following evaluation tests for the gloss of printed portion, abrasion resistance, and gloss uniformity. These results are shown in Table 2 below.

(Print section glossiness evaluation test)
After the recorded matter was allowed to stand at 25 ° C. for 24 hours, the specular glossiness at an incident angle of 20 degrees for the printed portion was measured using a gloss meter GM-268 manufactured by Konica Minolta Sensing Co., Ltd. The specular glossiness is measured twice for each duty of each color, and the average value of them is calculated. The average value is 60 or more when the average value is A (good gloss on the printed part), and 55 or more and less than 60. B, 50 or more and less than 55 was designated as C, and less than 50 was designated as D.

(Rubbing resistance evaluation test)
Lightly rub the printed part of the recorded matter with your finger and visually observe it. A (the image has good abrasion resistance) that does not turn or disturb the image, there is a slight turn on the edge of the image, or the image is disturbed. Slightly recognized but no problem in practical use was designated as B, and the image edge was largely turned up or the image was markedly stained as C.

(Gloss uniformity evaluation test)
Two places are selected arbitrarily for each duty for each color from the printed part of the recorded matter, and the specular glossiness for each of these selected places is set to 20 degrees using a variable angle gloss meter GM-3D manufactured by Murakami Color Research Co., Ltd. Measurements were made based on the following evaluation criteria from the average value and standard deviation of these measured values, and the 20-degree specular gloss (white gloss) of the non-printed area. The results are shown in Table 4 below.
A: The difference between the average glossiness and the white glossiness is within ± 15, and the standard deviation of glossiness is 15 or less. Good gloss uniformity.
B: The difference between the average glossiness and the white background glossiness is within ± (over 15 and below 20), and the standard deviation of glossiness is above 15 and below 20
C: The difference between the average glossiness and the white glossiness exceeds ± 20, or the standard deviation of glossiness exceeds 20.

Claims (3)

An ink jet recording method for forming an image by discharging a color ink containing a pigment as a colorant and a clear ink not containing a colorant toward a recording area of a recording medium,
The clear ink contains at least a polyurethane resin and water,
An ink jet recording method in which the discharge amounts of the color ink and the clear ink are adjusted so that the adhesion amount of the resin component derived from the ink per unit area in the recording area is uniform throughout the recording area.   2. The ink jet recording method according to claim 1, wherein the discharge amount of the clear ink is increased in a region where the duty of the color ink is low, and the discharge amount of the clear ink is decreased in a region where the duty of the color ink is high. The inkjet recording method according to claim 1 or 2, wherein the recording area has a 20 degree glossiness of 10% or more as defined in JIS-Z8741.