JP2005153384A - Method of recording by using water-curable inkjet ink - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To hold a high image fastness of a pigment, to realize forming of a highly precise image by a pigment ink and fast crosslinking-fixing of the ink by radiation of a light, and to, particularly, realize a sufficient density, fastness or glossiness of an image/character formed material in black. <P>SOLUTION: This method of recording uses a water curable inkjet ink containing an oligomer or monomer having a photopolymerizable functional group and a hydrophilic part, a pigment, a photopolymerization initiator, and a water. The method of recording comprises a process (1) of using a water curable inkjet color ink set including colorants capable of forming a black by subtractive color mixing and a process (2) of performing printing by an inkjet black ink including a black colorant or an inkjet clear ink not including a colorant before and after performing the printing by the water curable inkjet color ink set. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an ink used in an ink jet recording method for recording an image by discharging ink, and a recording method using the ink.

  The ink jet method is a method for recording images, characters, and the like by ejecting micro droplets of ink by various operating principles and attaching them to a recording medium (paper, etc.). It has features such as easy, high flexibility of recording patterns, no need for development and fixing, and is rapidly spreading in various applications. Furthermore, in recent years, full-color multi-color inkjet recording technology has been developed, and it is also possible to form multi-color images that are comparable to multi-color printing by plate-making methods and printing by color photographic methods. When the amount of ink is small, a printed matter can be obtained at a lower cost than ordinary multicolor printing or printing, so that it is widely applied to the field of full-color image recording.

  2. Description of the Related Art Conventionally, ink jet recording apparatuses and recording methods have been improved in accordance with demands for improving recording characteristics such as higher recording speed, higher definition, and full color.

  Among them, various attempts have been made not only to increase the definition of recorded images but also to improve image robustness. Therefore, development of pigment inks using pigments as color materials instead of using dyes as color materials is active.

  However, pigment inks also have unique problems. For example, when these pigment inks are used to record on a medium having a high surface gloss such as an ink-jet glossy paper or an ink-jet glossy film, the glossiness of the glossy media tends to be lost in the print area. . In addition, the rubbing property of the printed part is often inferior to that of the dye ink. In addition, when printing on plain paper, problems such as insufficient color developability and image density and insufficient fixability occur.

  Various technical means have been devised for these conventional problems. For example, JP-B-62-1426, JP-A-55-157668, JP-A-3-160068, and JP-A-4-18427 describe that a water-insoluble resin emulsion is added to a pigment ink. However, these resin emulsion-added inks are not sufficient in terms of clogging at the head and ink dispersion stability, but the above disadvantages have not been solved. Even if such a resin emulsion is added to the ink, the pigment after printing does not permeate and diffuse into the recording medium, and is only present on the surface of the medium. I was still not satisfied.

  JP-A-9-151342, JP-A-2001-234097, and the like are inks coated with a pigment, and JP-A-2001-247800 discloses an aqueous dispersion of polymer particles containing a pigment. A water-based ink containing is described. Further, as described in JP-A-10-316909, a method for adjusting a pigment coated with a resin is described. That is, a reactive surfactant is used to coat and process a pigment as a coloring material, and the pigment surface is coated as a polymer obtained by copolymerization with a monomer. However, here, the photopolymerization functional group reacts at the time of copolymerization at the time of ink ejection and landing, and does not contribute to the subsequent fixability because it does not exist in the ink and in the vicinity of the pigment surface. In addition, in the ink in which the polymer resin is arranged around the pigment, there are others, but generally, it is not sufficient to secure the gloss of the printed part, the scratch, and the color density of the glossy paper.

  In contrast to these methods, a method using an ink containing a photopolymerizable compound that is crosslinked by ultraviolet rays or electron beams is known. Here, most of these curable inks that use energy rays such as ultraviolet rays are non-aqueous inks, and typical examples thereof are organic solvents such as toluene and methyl ethyl ketone. Oil-based inks in which pigments are dispersed are used. Further, there is known an ink composed of a monomer, an oligomer, and a pigment dispersion without using a solvent as described in JP-B-5-64667. However, these inks are not suitable for precise printing because the viscosity of the ink does not become sufficiently low. In addition, oil-based inks need to be used with care from an environmental point of view.

  On the other hand, the viscosity can be lowered by the water-based ultraviolet inkjet ink, and a high-definition image is also possible. However, since water-based ultraviolet inkjet ink uses water as a solvent, it has been pointed out that water is disadvantageous in drying compared with an organic solvent.

However, the water-based ultraviolet inkjet curing technology is useful because it is an image recording method that uses energy-saving, environmental pollution, and environmental impact-free curing technology, and can obtain a high-definition and highly robust image. It is believed that there is.
For such water-based ultraviolet inkjet ink, a material having low viscosity and good fluidity that can be used for a high-density nozzle is required. As a result, the amount of the polymerizable compound added in the ink can be increased, the substantial curing time can be shortened, and the cured ink film when the ink is cured after being discharged to a predetermined portion on the non-recording medium. Therefore, it is necessary to select a polymerizable substance or a photocatalyst having good compatibility with the coloring material in order to sufficiently secure the physical properties.

  In recent years, the development of water-soluble polymeric substances and photocatalysts has progressed, and the curing time has been shortened. There is room for improvement in durability, and sufficient glossiness and image density are still not sufficient.

  These problems are important for black inks having a wide light absorption wavelength region, and improvements are required.

  As a solution to these problems, Japanese Patent Application Laid-Open No. 8-150707 and Japanese Patent Application Laid-Open No. 2000-141616 describe a method of forming an image with an ink and curing with ultraviolet irradiation after forming a base layer. Japanese Patent Application Laid-Open No. 2000-158793 describes a method in which a white underlayer is formed and color printing is performed by ink jetting, followed by overcoating and curing by coating and ultraviolet irradiation.

According to these methods, it is possible to improve the strength of the adhesion of the recorded image with ink to the adherend, but the former still does not provide sufficient gloss and secure image density. Also, when the latter overcoat is applied, the scratch resistance from the surface can be improved. However, the image density of black ink has not been improved, and it has not yet been applied to plain paper, so there is room for improvement. There is.
Japanese Examined Patent Publication No. 62-1426 JP 55-157668 A Japanese Patent Laid-Open No. 3-160068 JP-A-4-18427 Japanese Patent Laid-Open No. 9-151342 JP 2001-234097 A JP 2001-247800 A Japanese Patent Laid-Open No. 10-316909 Japanese Patent Publication No. 5-64667 JP-A-8-150707 JP 2000-141616 A JP 2000-158793 A

  Therefore, the present invention solves the above-mentioned problems, maintains high image fastness of the pigment as the color material, and further achieves high-definition image formation with the pigment ink, and promptly cross-links the ink by light irradiation. Fixing can be realized, and in particular, sufficient image density, fastness, and glossiness of a black image / character formed product are realized.

That is, the present invention relates to a recording method using an aqueous curable inkjet ink containing an oligomer or monomer having a photopolymerizable functional group and a hydrophilic site, a pigment, a photopolymerization initiator, and water.
1) Use an aqueous curable inkjet color ink set containing a colorant capable of forming black by subtractive color mixing 2) Before and after printing with an aqueous curable inkjet color ink set containing a colorant capable of forming black by subtractive color mixing The recording method is characterized in that printing is performed with an inkjet black ink containing a black color material or an inkjet clear ink not containing a color material.

  As described above, according to the present invention, the high image fastness of the pigment as the coloring material is maintained, and further, high-definition image formation is realized with the pigment ink, and the ink is rapidly crosslinked by light irradiation. There is provided a recording method that can realize fixing, and in particular, a sufficient image density, fastness, and glossiness of a black image / character formed product.

  Next, the present invention will be described in detail with reference to preferred embodiments. In order to solve the above-described problems of the prior art, the present inventors have intensively studied, an aqueous curable type containing an oligomer or monomer having a photopolymerizable functional group and a hydrophilic site, a pigment, a photopolymerization initiator, and water. In the ink jet recording using ink, a clear black character image, high scratching and glossy image formation have been realized.

  In general, ink-jet inks are roughly classified into dye inks and pigment inks. However, when dye inks require images with good colors, they are particularly high-definition and are used to obtain images with high gloss such as photographs. It is used for. On the other hand, pigment inks are widely used for large format printers and printing applications because of their high fastness such as light resistance and gas resistance. However, at present, printing systems using special special paper are the mainstream for pigment inks. The reason for this is that special image with high gloss such as glossy paper cannot be obtained when printing on plain paper. On paper, scratch resistance such as scratching and glossiness are insufficient.

  In order to solve these problems, UV curable pigment ink systems have been studied and put into practical use. However, when black pigments are used, the light absorption wavelength range is wide, so that crosslinking reactivity due to light irradiation is reduced. It is not easy to get enough. In contrast, in general, non-aqueous photo-curable ink can increase the resin content that contributes to photo-curing, and realizes recording with high scratching characteristics even for non-absorbable recording materials, The viscosity of the ink composition itself is high, and it is mainly used for large format printing, and it cannot realize image formation with higher image quality.

  From the above, high-definition black and high-definition recording suitable for plain paper while simultaneously using process black formation by subtractive color mixing in order to achieve high color density and high durability such as scratch resistance The method has been realized.

  Here, subtractive color mixing will be described. In general, color mixture is the superposition of two or more kinds of light, or the superposition and mixing of absorbing materials to produce a color that is different from the original color. This is called additive color mixing, and the method of superimposing is by making light incident simultaneously or rapidly alternately in the same part of the retina or in a form that is so fine that it cannot be visually resolved. The spectral distribution and tristimulus values (CIE color system) resulting from the additive color mixture are expressed by weighted addition of the original colors, and subtracted when overlaying transparent selective absorption films such as a color film. This is called color mixing, and the resulting spectral transmittance is represented by the product of the spectral transmittance of the original color. In the case of halftone dot printing, subtractive color mixing and additive color mixing are performed simultaneously, and pigment mixing and dyeing of diffusing materials are a kind of subtractive color mixing in the case of superposition of diffusible absorbent materials. It is represented. C, M, and Y are three primary colors of the subtractive color mixture system. By printing three colors of Y (yellow), M (magenta), and C (cyan) in accordance with the color information of each pixel to be printed, it is possible to obtain a print output with a desired hue. According to the method of color mixture, only the R (red) light is transmitted through the area where the Y and M inks overlap, and only the G (green) light is transmitted through the area where the Y and C inks overlap. Since the area where the M and C inks are overlapped transmits only B (blue) light, and the area where all the Y, M and C inks overlap is that no light is transmitted, K (black) can be expressed. it can.

  In the present invention, the subtractive color mixture as described above is used, and a desired black is formed by using superposition of a desired ink set. Here, it is also possible to superimpose a small amount of ink containing a pigment such as carbon black for color matching as long as curing by ultraviolet rays is not impaired. Also, not only the superimposition of the three primary colors of Y, C and M, but also the superposition of R, G and B and various color combinations are possible. To select.

  Details of the recording method using the subtractive color mixture described above are as follows. First, an image is formed using yellow (Y), magenta (M), and cyan (C) to form a black image. Next, black or clear ink is overprinted. Then, again, an image is formed using yellow (Y), magenta (M), and cyan (C), that is, black ink in which black ink or clear ink not containing a coloring material is sandwiched. The image is complete.

  What is important here is that yellow (Y), magenta (M), cyan (in view of obtaining a preferable black color, obtaining a halftone and gradation, and obtaining sufficient scratch resistance and glossiness. C) The combination of each ink, the printing order, the amount of black applied, the intensity of light irradiation, and the timing are important.

  Specifically, the sensitivity to the irradiated ultraviolet rays depends on the type of photopolymerization initiator, but in the order of yellow (Y), magenta (M), cyan (C), and black (Bk), which is close to the adherend. It is desirable that yellow ink is disposed on the portion and the surface portion. Furthermore, it is also effective to select a photopolymerization initiator that does not overlap the absorption wavelength of the color material. In addition, although the example mentioned above is a three-color process of Y, M, and C, the thing of colors, such as red (R), green (G), blue (B), and violet (V), and also the hue were adjusted. You may add things suitably.

  Further, in order to make these image recording methods more effective, a recording head with light irradiation devices as shown in FIG. 1 can be used, or multi-pass printing can be used for light irradiation. The timing can be adjusted appropriately, or the arrangement of the discharge nozzles for each color can be devised as shown in FIG. Details will be described later.

  In this recording method, when black ink is arranged in the middle, higher image density of black is expected, and when clear ink is arranged, high glossiness and scratch resistance of black are expected. Also, black and clear ink can be used in combination. FIG. 2 shows an example of the nozzle arrangement of FIG. 2-a when used alone and FIG. 2-b when used together.

  FIG. 3 shows a schematic cross-sectional view when an ink layer is laminated by the recording method of the present invention.

  Here, FIG. 3A is a schematic diagram when black ink is arranged in the middle, 300 is the surface of the recording medium, 301 is an ink lower layer formed by a combination of color inks, and 302 is formed by black ink. Ink intermediate layer 303 is an ink upper layer formed by a combination of color inks, FIG. 3B is a schematic view when clear ink is arranged in the middle, and 304 shows an ink intermediate layer formed by clear ink. In order to form these upper layers, intermediate layers, and lower layers, light irradiation and printing are performed using the recording apparatus shown in FIG. 1, etc., but the intensity of light irradiated before and after the formation of each layer, irradiation timing, irradiation time, number of irradiations The cured state can be controlled according to the type of recording medium to be recorded and the ink composition. For example, for plain paper, the irradiation conditions immediately after forming the lower layer are strong, and after the intermediate layer is formed, the semi-cured state is slightly weakened. Integrates the lower layer, the intermediate layer, and the upper layer, and as a result, sufficient curing can be performed, and recording with black having high image density, quality, and abrasion can be performed. By temporarily maintaining the semi-cured state of the intermediate layer, an overall strong ink layer can be formed by a temporary compatibility effect between the lower layer and the upper layer. In particular, when black ink is used (FIG. 3-a), high image density can be expected even on plain paper recording, and when clear ink is used (FIG. 3-b), lower layer, intermediate layer, and upper layer inks are used. The layers can be integrated to form a stronger ink layer. This is because the binder component in the intermediate layer enters the lower and upper pigment ink layers and is integrated. As a result, higher glossiness can be expected. This is particularly effective when recording on special paper such as glossy paper.

  In the present invention, in order to secure a high image density of black and obtain a higher winding strength, the concentration of the pigment in the upper layer and the lower layer, the amount of the oligomer or monomer having a photopolymerizable functional group and a hydrophilic portion, and the intermediate layer The concentration of the black pigment to be formed and the amount of the oligomer or monomer having a photopolymerizable polymerizable functional group and a hydrophilic site are important. Here, when the pigment component in the black ink of the intermediate layer is 1, the pigment component of the black ink formed in combination is 0.1 to 2 times, so that the color density of each ink layer and the entire ink layer is increased. And the film strength can be secured.

  Further, in the present invention, the black ink forming the intermediate layer is not only a pigment ink containing an oligomer or monomer having a photopolymerizable functional group and a hydrophilic site, but also a black colorant and a resin that contributes to dispersion. In other words, a resin-dispersed pigment, a microcapsule ink coated with a pigment with a resin, or the like may be used. However, there is a limit to the amount of black ink applied to form the intermediate layer, and the photopolymerizable functional group and the hydrophilic part are used in order that the upper and lower ink layers have the role of maintaining the film strength of the entire ink layer. It is necessary to increase the amount of the oligomer or monomer having sigma and the driving amount at the time of printing.

  Next, materials to be used, recording apparatus, etc. in the present invention will be described in detail.

(Pigment)
Specific examples of the black pigment used in the present invention include carbon black. The carbon black is, for example, a carbon black produced by a furnace method or a channel method, and has a primary particle diameter of 15 to 40 mμ, a specific surface area by a BET method of 50 to 300 m ² / g, and a DBP oil absorption of 40 to 150 ml. / 100 g, a volatile component of 0.5 to 10%, a pH value of 2 to 9 and the like are preferably used. Examples of commercially available products having such characteristics include No. 2300, no. 900, MCF88, No. 33, no. 40, no. 45, no. 52, MA7, MA8, no. 2200B (Mitsubishi Kasei), RAVEN 1255 (Columbia), REGAL400R, REGAL 330R, REGAL 660R, MOGUL L (Cabot) Printex U (manufactured by Degussa) and the like can be used preferably.

  Examples of the color pigment used in the present invention include, for example, pigment yellow 1, pigment yellow 2, pigment yellow 3, pigment yellow 12, pigment yellow 13, pigment yellow 14, pigment yellow 16, pigment yellow 17, Pigment Yellow 55, Pigment Yellow 73, Pigment Yellow 74, Pigment Yellow 75, Pigment Yellow 83, Pigment Yellow 93, Pigment Yellow 95, Pigment Yellow 97, Pigment Yellow 98, Pigment Yellow 109, Pigment Yellow 110, Pigment Yellow 114, Pigment Yellow 128, Pigment Yellow 138, Pigment Yellow 139, Pigment Yellow 150, Pigment Yellow 151, Pigment Yellow 154, Pigment Yellow 155 and Pigment Yellow 180, and the like.

  Examples of magenta pigments include, for example, Pigment Red 5, Pigment Red 7, Pigment Red 12, Pigment Red 48 (Ca), Pigment Red 48 (Mn), Pigment Red 57: 1, Pigment Red 57 (Sr), and Pigment Red 57: 2, Pigment Red 122, Pigment Red 123, Pigment Red 168, Pigment Red 184, Pigment Red 202, Pigment Red 238, and the like.

  Examples of cyan pigments include Pigment Blue 1, Pigment Blue 2, Pigment Blue 3, Pigment Blue 16, Pigment Blue 22, Pigment Blue 60, Pigment Blue 15: 2, Pigment Blue 15: 3, Bat Blue 4 and Bat Blue 60. Etc.

  The average particle diameter of the pigment particles is preferably in the range of about 25 nm to 200 nm. Although this range depends on the use of the printed matter, it is sufficiently smaller than the wavelength of visible light, so that it can be said that the printed matter can be said to be sufficiently clear if the scattering is small.

  The content of the pigment in the ink is appropriately selected depending on the marking application and the photographic image forming application, but it is preferable that the pigment is contained in the range of 0.1% to 10% in terms of solid content with respect to the whole ink. The pigment contained in each ink forming the upper layer, the intermediate layer, and the lower layer is appropriately adjusted.

In addition, it is important that these pigments are previously dispersed in the ink, and better dispersion can suppress an increase in viscosity and aggregation over time. Specifically, a dispersion method in which a water-soluble polymer is adsorbed on the pigment surface is common. In this case, a water-soluble polymer having an anionic dissociative group is adsorbed on the pigment surface. Specifically, acrylic acid, acrylic acid derivatives, methacrylic acid, methacrylic acid derivatives, bezyl methacrylate, styrene, styrene derivatives, vinyl naphthalene derivatives, aliphatic alcohol esters of α, β-ethylenically unsaturated carboxylic acids, maleic acid, etc. From at least two monomers selected from maleic acid derivatives, itaconic acid, itaconic acid derivatives, fumaric acid, fumaric acid derivatives, vinyl acetate, vinylpyrrolidone, etc. (one of which is a hydrophilic monomer) And a random copolymer, a block copolymer, a graft copolymer, or a salt thereof. These water-soluble polymers are not limited to those mentioned above, and are appropriately selected according to the type of pigment and surface characteristics, and used alone or in combination of two or more. Further, in the present invention, pigments coated with a resin and dispersed in JP-A-9-151342, JP-A-2001-234097 and the like may be used.

(Hydrophilic oligomer / monomer having a photopolymerizable functional group)
In addition, the hydrophilic oligomer or monomer having a photopolymerizable functional group that may be added in combination with the pigment that can be used in the present invention is polymerized by irradiation with ultraviolet rays in the presence of a photopolymerization initiator to make it desirable. A material that has the characteristics of a cured film and that satisfies the characteristics of an inkjet ink when used as an ink is used. These oligomers or monomers having a photopolymerizable functional group are added and used during ink preparation.

  Specifically, what is used as a conventional ultraviolet curable material for water-based inkjet can be used, and as a monofunctional one, both an acidic group and a (meth) acryloyl group or vinyl group are present in the molecule, and Examples of water-soluble polymerizable compounds include esters of succinic anhydride and 2-hydroxyethyl (meth) acrylate, esters of orthophthalic anhydride and 2-hydroxyethyl (meth) acrylate, vinyl naphthalene sulfone. An acid or the like is used. Further, methoxypolyethylene glycol methacrylate, methoxypolyethylene glycol acrylate, etc. are used. As the water-soluble monomer, acryloyl morphophorin, diacetone acrylamide, N-vinyl-2-pyrrolidone, N-vinyl-formamide and the like are used.

  Furthermore, in the present invention, a water-soluble polyfunctional polymerizable compound is selected in order to increase the reactivity by light irradiation. For example, a compound having two or more acryloyl groups in one molecule is suitable, and a compound having a solubility in water of 10% by weight or more can be suitably used. Examples thereof include (meth) acrylic acid esters of polyhydric alcohols and (meth) acrylic acid esters of glycidyl ethers derived from polyhydric alcohols. Specific examples of the (meth) acrylic acid ester of a polyhydric alcohol include polyethylene glycols such as polyethylene glycol diacrylate and polyethylene glycol dimethacrylate. Specific examples of the (meth) acrylic acid ester of glycidyl ether include (meth) acrylic acid esters of polyhydric alcohols and the like. Specific examples include the following compounds.

尚、これらの多価アルコール類は、エチレンオキシドの付加によって内部がエチレンオキシド鎖で鎖長が延長されたものであってもよい。また、以上に挙げた水溶性の光重合性官能基を有するオリゴマーやモノマーは上記のものに限定されるものではない。

In addition, these polyhydric alcohols may have an ethylene oxide chain and an extended chain length by addition of ethylene oxide. Further, the oligomers and monomers having the water-soluble photopolymerizable functional groups mentioned above are not limited to the above.

(Photopolymerization initiator)
As the photopolymerizable initiator used in the present invention, a general aqueous one can be used. Here, a hydrogen abstraction or α-cleavage type photopolymerization initiator is used. Specifically, acetophenone, 2,2-diethoxyacetophenone, p-dimethylaminoacetophene, p-dimethylaminopropiophenone, benzophenone, 2-chlorobenzophenone, pp′-dichlorobenzophene, pp′-bisdiethylaminobenzophenone, Michler's ketone, benzyl, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin n-propyl ether, benzoin isobutyl ether, benzoin n-butyl ether, benzyl dimethyl ketal, tetramethylthiuram monosulfide, thioxanthone, 2-chlorothioxan Son, 2-methylthioxanthone, azobisisobutyronitrile, benzoin peroxide, di-tert-butylper Xoxide, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-1-one, 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropan-1-one, methylbenzoylpho Mate. The amount used is usually 0.1 to 10% by weight based on the total amount of the ultraviolet curable resin. Among the photopolymerizable initiators, those having good hydrophilicity and water-solubility are preferable in the present invention, and compounds having the following structures are preferably used.
1) α-hydroxyphenyl ketone derivative 2) thioxanthone derivative 3) acridone derivative 4) benzophenone derivative The above photopolymerization initiator is present in an amount sufficient to cure the composition, and is usually 1 by weight relative to the whole ink composition. Contains ~ 6%.

(Sensitizer)
Further, a sensitizer may be added to accelerate the reaction. Specifically 1) Amine type: aliphatic amine, amine containing aromatic group, piperidine, etc. 2) Urea: allyl type, o-tolylthiourea, etc. 3) Sulfur compound: sodium diethyldithiophosphate, solubility of aromatic sulfinic acid 4) Nitrile compounds: N, N, di-substituted p-aminobenzonitrile, etc. 5) Phosphorus compounds: tri-n-butylphosphine, netium diethyldithiophosfeed, etc. 6) Nitrogen compounds: Michler's ketone, N-nitrisohydroxylamine derivative, Examples thereof include oxazolidine compounds, tetrahydro-1,3 oxazine compounds, formaldehyde or a condensate of acetaldehyde and a diamine.

(Additive)
In the present invention, the ink may contain any additive in addition to the above substances. Examples of such additives include pH modifiers, leveling agents, viscosity modifiers, antioxidants, hindered amine light stabilizers (HALS), preservatives, fungicides and the like. When used, it is usually contained in an amount of 0.1 to 5% by weight with respect to the whole ink composition.

(Diluted solvent component)
In the present invention, as a diluent solvent other than pigments, photopolymerization initiators, water-soluble polymerizable oligomers / monomers, sensitizers, additives, etc., in order to obtain stable ejection in inkjet recording, particularly in thermal inkjet recording systems. Water is mainly used, but other than this, an aqueous and polymerization-reactive low-viscosity monomer can be used. The advantage of using such substances, not usually solvents, is that these substances do not remain as plasticizers in post-reaction solids that have been cured with UV light, thus reducing the effect on solid physical properties. . Examples of reactive dilution solvent components selected for such purposes include acryloyl morphophorin, N-2-vinylpyrrolidone, acrylamide, methylene bisacrylamide, monosaccharide monoacrylate, oligoethylene oxide mono acrylate as mentioned above. Examples include acrylic acid esters and dibasic acid monoacrylic acid esters.

  In the present invention, it is also possible to add a solvent component conventionally used in water-based inkjet inks. However, as described above, a solvent to be added in order to reduce the influence on the solid physical properties of the cured product. It is necessary to pay careful attention to the type and amount of components, the absorbability of the recording medium, and the like. That is, when 10% or more of the solvent component used in the conventional ink-jet ink is used, it is a recording medium having a certain wetting, penetrating and absorbing properties, and is also a gap type (consisting of inorganic particles and a binder). It is desirable to use a recording medium. That is, glossy paper, coated paper, etc. are desirable.

  Further, these solvent components are preferably those which are evaporated and dried relatively easily, and can be arbitrarily added from the following. For example, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monoallyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, propylene glycol Examples thereof include glycol ethers such as monomethyl ether and dipropylene glycol monomethyl ether, and monohydric alcohols.

  In the present invention, an ink is prepared using the above-described substances. Many of the above-described oligomers having a photopolymerizable functional group and a hydrophilic portion have an acidic functional group. It is desirable to have a neutralized and dissociated state. Therefore, it is usually adjusted from neutral to basic by alkali metal, alcohol amine, ammonia, morpholine, piperidine, etc., and then dissolved in water. At this time, the use of a compound having a primary or secondary amino group may be avoided because addition of a polymerizable substance to a double bond (Michael addition) may occur even in an aqueous solution. Good. Since this reaction is inhibited by polar groups, the reaction proceeds very little as long as water is present in a large amount. Therefore, the extent to which the use of compounds having primary and secondary amino groups should be avoided depends on the shelf life guarantee of the composition. The ink may be mixed in any order with the raw materials to be used, but in order to ensure stability during mixing, the ink is not uniform when mixed in order to modify the dispersibility of the pigment depending on the pH range. It is preferable to stir quickly so as not to hold it for a long time. Moreover, after mixing, it is preferable to perform further stirring so as not to impair the uniformity.

  In addition, the clear ink can be produced by a combination of the above substances, that is, it can be produced by a combination excluding the pigment component, but attention is required for solidification in the ink tank because of its high reactivity. The effects of light and drying temperature during tank storage can be excluded.

(Recording system)
As an apparatus suitable for performing recording using the ink according to the present invention described above, for example, a method of applying thermal energy corresponding to a recording signal to ink in a recording head chamber and generating droplets by the thermal energy. And devices.

  Specifically, as shown in the schematic diagram of the front of the printer in FIG. 1, an ink tank unit 101 that holds the ink of the present invention, and a head unit 102 (here, the head is attached) that is attached with an ink tank and actually performs recording. A plurality of arranged multi-heads), a lamp unit 103 that emits light for curing, a drive unit 104 that drives the head unit and the lamp unit, and a paper discharge unit 105 that conveys a recording medium to be recorded. When the recording apparatus is used, image recording and crosslinking are effectively performed. In addition to these, a wiping unit, a capping unit, a paper feeding unit, a drive motor unit, etc. (not shown) are provided.

  In FIG. 1, a head unit 102 and a lamp unit 103 are simultaneously scanned left and right to sequentially record and irradiate a recording medium. As shown in FIG. 1, the lamp unit 103 may be arranged on the left or right side of the head unit 102 or may be arranged on either one of them. Details of the lamp will be described later.

  In this case, four colors of black (Bk), cyan (C), magenta (M), and yellow (Y) are arranged in the tank unit 1, but light cyan (LC) is used to record a higher definition image. Or six colors of light magenta (LM) may be arranged. A clear (CL) may be arranged instead of black, or it may be used in combination with black. In the present invention, it is preferable that the tank can block light.

  In the present invention, in addition to the recording system described above, a lamp is disposed on the front surface of the paper discharge unit, a paper feed / discharge is performed by being wound around a rotating drum, and a drying unit is separately provided. Things can be selected as appropriate.

  FIG. 2 shows a schematic diagram of a head configuration for carrying out the recording method of the present invention. As shown in the figure, a Bk (or CL) nozzle row is arranged at the center, and Y, M, and C are arranged on the left and right sides thereof. Thereby, the ink layer which consists of a lower layer, an intermediate | middle layer, and an upper layer as mentioned above can be formed also in bidirectional printing. In addition, this makes it possible to make the apparatus compact.

(Light irradiation lamp)
The ultraviolet irradiation lamp used for curing the ink composition particularly suitable in the present invention will be described below. The ultraviolet irradiation lamp is preferably a so-called low-pressure mercury lamp, high-pressure mercury lamp, mercury lamp coated with a phosphor, or the like whose mercury vapor pressure is 1 to 10 Pa during lighting. The emission spectrum of these mercury lamps in the ultraviolet region is in the range of 184 nm to 450 nm, and is suitable for efficiently reacting a polymerizable substance in black or colored ink. Also, a small power supply can be used for mounting the power supply in the printer, which is also suitable in that sense. For example, metal halide lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, xenon flash lamps, deep UV lamps, lamps that excite mercury lamps from the outside using microwaves, UV lasers, etc. are in practical use. Since the wavelength range includes the above range, it is basically applicable if the power source size, input intensity, lamp shape, etc. are allowed. The light source is selected according to the sensitivity of the catalyst used.

The necessary UV integrated intensity is preferably about 500 to 5,000 mJ / cm ² in terms of the polymerization rate. If the integrated irradiation amount is insufficient, the adhesion force of the ink adhered to a predetermined portion on the recording medium cannot be sufficiently exhibited. Furthermore, in color recording, there is a deficiency in the fastness of the printed recorded image, which is an object of the present invention, such as insufficient water resistance.

  Next, an Example and a comparative example are given and this invention is demonstrated concretely. The present invention is not limited by the following examples unless it exceeds the gist. In the text, “part” or “%” is based on mass unless otherwise specified.

  The recording ink used in Example 1 and Comparative Example 1 was prepared as follows.

(Example 1 and Comparative Example 1)
The pigments Bk, C, M, and Y used in Example 1 and Comparative Example 1 are as follows, and pigment dispersions were prepared using these pigments.

Pigment Bk: Carbon black pigment (CI Pigment Black 7: Made of Columbian Carbon)
Pigment C: Copper phthalocyanine pigment (C.I Pigment Blue 15: 3: manufactured by Clariant)
Pigment M: Gimethylquinacridone pigment (CI Pigment Red 122: manufactured by Clariant)
Pigment Y: benzimidazolone pigment (CI Pigment Yellow 180: manufactured by Clariant)
Creation of dispersion of recording ink 1)
The following composition was used, and dispersion treatment was performed for 5 hours in a sand mill (not shown).

Pigment Bk 30 parts by mass Water-soluble polymer: Styrene-acrylic copolymer (molecular weight 10,000, acid value 200) 10 parts by mass Ion-exchanged water Remainder The liquid obtained in the same manner as in Example 1 was filtered through a 0.5 μm membrane filter. Then, a Bk pigment dispersion liquid was prepared.

  Similarly, a pigment dispersion of the recording ink 1 of Pigment C, Pigment M, and Pigment Y was prepared.

(Preparation of recording ink 1 and comparative ink 1)
Next, using this dispersion, each ink was prepared with the following composition.

Here, the structures of the photopolymerization initiator and the photopolymerizable oligomer are as follows. Acroyl morphophorin was used as a monomer, and triethanolamine was used as a pH adjuster.
Photopolymerization initiator (8)

光重合性オリゴマー（9）

Photopolymerizable oligomer (9)

顔料分散体 １２部
光重合性開始剤 １．５部
モノマー希釈剤（ＡＣＭＯ） １０部
光重合性オリゴマー ２０部
ｐＨ調整剤（ＴＥＡ） ０．５部
イオン交換水 残部
得られたインク組成物を０．５μｍのメンブランフィルターにてろ過し、粘度を不図示のＥ型粘度計にて測定したところ３．１ｃｐｓであった。

Pigment dispersion 12 parts Photopolymerizable initiator 1.5 parts Monomer diluent (ACMO) 10 parts Photopolymerizable oligomer 20 parts pH adjuster (TEA) 0.5 parts Ion-exchanged water remainder The resulting ink composition is 0 It was 3.1 cps when it filtered with a 0.5 micrometer membrane filter and the viscosity was measured with the E-type viscosity meter not shown.

(Print evaluation)
In Example 1 and Comparative Example 1 described above, printing evaluation was performed using the above ink. As the ink jet recording apparatus used here, the same recording apparatus as shown in FIG. 1 was used. The recording head used had a recording density of 1200 dpi, and the driving condition was a driving frequency of 10 kHz. When a 1200 dpi head was used, a discharge amount per dot was 5.0 pL. The center emission wavelength of the lamp is 365 nm, and the intensity at the irradiation position is 300 mW / cm ² . These recording conditions are the same throughout the examples and comparative examples.

  In the first embodiment, this recording apparatus is used to perform overprinting with 20% printing in the order of yellow, magenta, and cyan. Thereafter, printing with 100% printing in black was performed, and a pattern and 16-point characters with 20% printing in the order of cyan, magenta, and yellow were formed.

  In Comparative Example 1, 100% printing with black was performed using the same recording apparatus. Immediately after printing, light was irradiated in the same manner as in Example 1.

  The recording paper used for the evaluation is A4 size PPC paper (manufactured by Canon).

(Evaluation 1)
For the print samples of Example 1 and Comparative Example 1 created under the above-described conditions, the image density, character quality, and whether the formed film has sufficient strength are rubbed and line marker resistance The gloss test was conducted as follows.
The results are shown in Table 1.

(1) Image Density The above samples that were allowed to stand for 24 hours after printing were measured using a primary densitometer Macbeth RD-918 (manufactured by Macbeth). The obtained results were evaluated according to the following criteria.

A: Image density is 1.35 or more B: Image density is 1.2 to 1.34
C: Image density is less than 1.2 (2) Character quality The 16-point character portion of the sample was visually observed and the bleeding of the character was evaluated according to the following criteria.

A: There is almost no bleeding.
B: Some blurring characters are seen.
C: Many characters are blurred.

(3) Scratch resistance When the sample was allowed to stand for 24 hours after printing, when the Sylbon paper was placed on the printed paper and the weight of 40 g / cm ² was placed on the recording surface, Whether or not the non-printed portion (white background portion) and the Sylbon paper were stained due to rubbing of the printed portion was visually observed and evaluated according to the following criteria.

A: Dirt due to rubbing is not seen.
B: There is almost no dirt due to rubbing.
C: The dirt part by a blur is conspicuous.
(4) Line marker resistance For the above sample that was left for 1 hour after printing, using the yellow fluorescent pen spot lighter yellow manufactured by Pilot, the character part was marked once with normal writing pressure, and the presence or absence of character disturbance was visually observed. Observed and evaluated according to the following criteria.

A: Character disturbance due to the marker does not occur.
B: Character disturbance due to the marker occurs slightly.
C: Character disturbance due to the marker is remarkably generated.

（実施例２及び比較例２）
実施例１において用いた被記録媒体を光沢紙ＧＰ−３０１（キヤノン製）変え対外は同様にインク作製及び印字を行い、以下の評価を行った。

(Example 2 and Comparative Example 2)
The recording medium used in Example 1 was changed to glossy paper GP-301 (manufactured by Canon), and ink was prepared and printed in the same manner, and the following evaluation was performed.

  The results are shown in Table 2.

(Evaluation 2)
(5) Scratch resistance The above samples left for 24 hours after printing were rubbed with an eraser 5 times under normal use, and the portions were visually observed. The results were evaluated according to the following criteria.

A: No change in the rubbed part.
B: A trace is made on the rubbed portion, but the decrease in density is small.
C: The ink layer is scraped off.

(6) Glossiness The 60-degree glossiness was measured with a gloss meter IG-320 (manufactured by HORIBA, Ltd.) for the sample left for 24 hours after printing.

  The glossiness was evaluated according to the following criteria.

A: Less than 60 to 80 B: Less than 40 to 60 C: Less than 40

FIG. 2 is a schematic view of the front of a suitable printer used in the present invention. It is the schematic which showed the nozzle structure of the suitable printer head used for this invention. It is the schematic which showed the cross section of the ink layer formed by printing of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Ink tank part which hold | maintains the ink of this invention 102 Head part which an ink tank is attached and actually performs recording 103 Lamp part which performs light irradiation for hardening 104 Drive part which drives a head part and a lamp part 105 Recording To transport the recording medium to be recorded

Claims (7)

In a recording method using an aqueous curable inkjet ink containing an oligomer or a monomer having a photopolymerizable functional group and a hydrophilic site, a pigment, a photopolymerization initiator, and water,
1) Use an aqueous curable inkjet color ink set containing a colorant capable of forming black by subtractive color mixing 2) Before and after printing with an aqueous curable inkjet color ink set containing a colorant capable of forming black by subtractive color mixing A recording method comprising performing printing with an inkjet black ink containing a black color material or an inkjet clear ink not containing a color material.   Printing with an aqueous curable inkjet color ink set containing a color material capable of forming black by the subtractive color mixture, then printing with an inkjet black ink containing a black color material or an inkjet clear ink not containing a color material, the subtractive color mixture The recording method according to claim 1, wherein the recording is sequentially performed in the order of printing with an aqueous curable inkjet color ink set containing a colorant capable of forming black.   The recording method according to claim 1, wherein the color material contained in the color ink and the black ink is a pigment.   The recording method according to claim 1, wherein the black ink contains a black color material, a photopolymerizable functional group, an oligomer or monomer having a hydrophilic portion, a pigment, a photopolymerization initiator, and water.   The recording method according to claim 1, wherein the black ink includes a black color material and a resin that contributes to dispersion.   The recording method according to claim 1, wherein the clear ink contains an oligomer or monomer having a photopolymerizable functional group and a hydrophilic site, a photopolymerization initiator, and water. 2. The recording according to claim 1, wherein the ink composition is cured by irradiating with ultraviolet light before and after printing with an aqueous curable inkjet color ink set containing a colorant capable of forming black by the subtractive color mixture. Method.

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