JP2015127101A - Inkjet recording method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inkjet recording method effective for forming a printed matter which becomes necessary temporarily, where printed images decolor after a certain period of time by natural light such as sunlight, enabling repeated use of printing paper.SOLUTION: Provided is a recording method of performing inkjet recording using an aqueous inkjet recording ink containing at least an aqueous medium on a recording medium having formed on at least one surface of a substrate an ink-receiving layer containing inorganic fine powder and an a water-soluble resin and/or a water-dispersible resin. The ink-receiving layer of the recording medium contains dimethyl thiourea and the inkjet recording ink contains an orange color material.

Description

  The present invention relates to an ink jet recording method, and more specifically, for example, when applied to a printer or plotter using an ink jet recording method, a suitable image can be formed, and at the same time, the color can be easily erased by light irradiation for a predetermined time. The present invention relates to an ink jet recording method.

  The ink jet recording method is a recording method in which images, characters, and the like are recorded by causing micro droplets of ink to fly according to various operating principles and adhere to a recording medium such as paper. In addition, the ink jet recording method has advantages such as high-speed printability, low noise, and flexibility in recording patterns, can easily perform multi-coloring, and does not require development and image fixing. In particular, an image formed by the multicolor ink jet recording method can obtain a recording that is comparable to the printing by the multicolor printing by the plate making method and the printing by the color photographic method. Has the advantage that the printing cost is lower than that of ordinary printing technology and photographic technology. For these reasons, the ink jet recording system has been rapidly spread in recent years as an image recording apparatus for various information devices.

  While the image quality of the formed image is improved with the remarkable development of the ink jet recording apparatus, the image recorded by the ink jet recording method using the water-based ink is likely to cause discoloration and fading in a short period of time, and the weather resistance is improved. There was a disadvantage of being inferior. For this reason, color materials used in ink jet recording inks have as good weather resistance as possible, and efforts have been made to prevent deterioration due to light, heat, etc., and for recording media that accept ink. In other cases, efforts have been made to prevent deterioration due to light, heat, etc. by containing a gas resistance inhibitor or a light resistance inhibitor.

  For example, Patent Document 1 discloses an orange water-based ink composition in which the fastness of a recorded matter is strong and the storage stability is excellent by an aqueous ink composition containing a water-soluble monoazo compound and an ink jet recording method using the same. Things are disclosed.

  Patent Document 2 discloses that a recording medium contains a compound (B), which is a thiourea derivative, an acrylamide-diallylamine hydrochloride copolymer and / or a polyallylamine acetate polymer, and a boron compound, for long-term storage. Inkjet recording sheets in which the color fading and discoloration of the image and the migration of the dye after printing are suppressed are disclosed.

  On the other hand, in recent years, logging a large amount of rainforest for the purpose of paper production has become a social problem, and suppression of mass consumption of paper has been demanded. On the other hand, as described above, the conventional technology aims to provide a highly robust recorded material that does not deteriorate even after long-term storage, and in particular, has excellent weather resistance and prevents deterioration. A printed matter printed by an inkjet printer using the intended recording medium cannot be erased. For this reason, even if it is temporarily needed, for example, printing paper used for trial printing or printing paper used as reference material for a one-time meeting, it is not necessary to store it. The paper cannot be repeatedly used with the color erased, and these printing papers are immediately discarded as they are, which causes a large amount of paper consumption. In recent years, efforts have been made to reuse discarded printing paper for the purpose of effective use of resources. However, paper must be collected, brought back to the paper manufacturer, and reprocessed as recycled paper. It takes a lot of time and money. For this reason, attention has been focused on inks and recording methods that are suitable for forming a printed matter that is temporarily required, and that can be erased after a certain period of time with low energy and efficiency after printing.

  For example, Patent Document 3 uses, as a pigment, 5-5 ′ indigotin disulphonate disodium which changes its color and disappears when irradiated with ultraviolet rays, while a paper transport path for transporting printing paper. In the middle of this, an inkjet printer having a function for erasing the printed record is disclosed, which is provided with an ultraviolet irradiation lamp for irradiating ultraviolet rays toward the printing surface of the printing paper.

JP 2005-272746 A JP 2004-1332 A Japanese Patent No. 3105304

  However, in the above-described prior art, high energy such as an ultraviolet irradiation lamp is required for erasing the printed matter, and a special device is required. Therefore, the printed matter once printed on the recording medium (paper). The development of a technology capable of easily and easily erasing the color with low energy has been awaited.

  Therefore, the object of the present invention is useful for the formation of printed materials for the purpose of temporary use, such as trial prints and reference materials, which are conventionally stored without being stored. Another object of the present invention is to provide an ink jet recording method in which, after printing, the color is erased in a predetermined time by natural light such as sunlight without using a high energy ultraviolet irradiation lamp.

  In response to the above-described problems of the prior art, the present inventors have compared the composition of the ink (coloring material) for forming a printed image and the configuration of the ink receiving layer of the recording medium that receives the ink. As a result of extensive studies, the inventors have found that the above problems can be solved by using orange ink and including dimethylthiourea in the formation of the ink receiving layer of the recording medium, and have completed the present invention.

  That is, the present invention comprises at least an aqueous medium in a recording medium provided with an ink receiving layer containing inorganic fine particles and a water-soluble resin and / or a water-dispersible resin on at least one surface of a substrate. A recording method configured to perform inkjet recording using an aqueous inkjet recording ink, wherein the ink receiving layer of the recording medium contains dimethylthiourea, and the inkjet recording ink contains an orange color material An ink-jet recording method is provided which is an orange ink.

  According to the recording method of the present invention, the formed image (printed matter) has sufficient color developability, while the image (printed matter) is naturally irradiated by high energy light from an ultraviolet irradiation lamp or the like. Since the printed image can be erased efficiently even by irradiation with low energy light of natural light such as sunlight for a certain period of time, it is extremely useful for forming printed matter for the purpose of temporary use. According to the study by the present inventors, the dimethylthiourea that characterizes the present invention works as a light-proofing agent for color materials other than orange ink, but for the color material of orange ink, It acts as a substance that specifically accelerates the decomposition speed of the color material and promotes light resistance, and enables the above-mentioned remarkable effects to be realized. According to the present invention, there is provided a recording method in which orange ink is erased by irradiation with low energy light for a certain period of time by a very simple means such as printing on a recording medium containing dimethylthiourea in an ink receiving layer. Is done.

FIG. 3 is a top view schematically showing an internal structure of a nozzle of a recording head. It is a side view which shows typically the internal structure of the nozzle shown to FIG. 1A. It is a front view which shows typically the ink discharge port of the nozzle shown to FIG. 1A. FIG. 3 is a front view schematically showing a recording head. It is AA sectional drawing of the recording head shown to FIG. 2A. It is a BB sectional view of the recording head shown in FIG. 2A. It is an expanded sectional view of an ink tank. FIG. 3 is an enlarged cross-sectional view of a recording head. FIG. 5 is an enlarged perspective view of the ink holding member shown in FIG. 4. It is Vb-Vb sectional drawing of the ink holding member shown to FIG. 5A. 1 is a schematic configuration diagram schematically illustrating an overall configuration of an ink jet recording apparatus. It is a block block diagram of the control system of the recording apparatus shown in FIG. 6 is a flowchart showing a recording head recovery sequence process. It is a schematic sectional drawing shown.

Next, the present invention will be described in more detail with reference to preferred embodiments.
<Recording medium>
First, components of a recording medium used in the ink jet recording method of the present invention will be described. The recording medium constituting the present invention is provided with an ink receiving layer on at least one surface of a substrate, and the ink receiving layer is added together with inorganic fine particles and a water-soluble resin and / or a water-dispersible resin. It is characterized by containing dimethylthiourea as an agent.

(Base material)
Examples of the substrate used in the present invention include a resin film, cast coated paper, baryta paper, resin coated paper (resin-coated paper coated on both sides with a resin such as polyolefin), and any of them can be preferably used. . Examples of the resin film include transparent thermoplastic resin films such as polyethylene, polypropylene, polyester, polylactic acid, polystyrene, polyacetate, polyvinyl chloride, cellulose acetate, polyethylene terephthalate, polymethyl methacrylate, and polycarbonate.

  In addition to this, paper with moderate sizing, non-size paper, coated paper other than those described above, sheet-like substances (synthetic paper, etc.) composed of films made opaque by filling with inorganic substances or fine foaming, Further, a sheet made of glass or metal may be used. Moreover, in order to improve the adhesive strength between these base materials and the ink receiving layer characterizing the present invention, it is also a preferred form that the surface of the base material is subjected to corona discharge treatment or various undercoat treatments.

(Ink receiving layer)
Next, the ink receiving layer constituting the recording medium used in the present invention will be described. The ink receiving layer is formed on at least one surface of the substrate as mentioned above, but includes at least inorganic fine particles, a water-soluble resin and / or a water-dispersible resin, and particularly contains dimethylthiourea. It is characterized by becoming.

  The present invention is characterized in that dimethylthiourea is contained in the ink receiving layer constituting the recording medium to be used. The dimethylthiourea used in the present invention may be any of 1,1-dimethylthiourea and 1,3-dimethylthiourea (N, N′-dimethylthiourea). According to the study by the present inventors, as described above, dimethylthiourea works as a light-proofing agent for color materials other than orange ink. In particular, it acts as a substance that accelerates the color material decomposition rate and promotes light resistance, so that the printed matter formed with orange ink can be erased by irradiation with low energy light such as natural light. It becomes possible to make it color.

  The amount of dimethylthiourea in the ink receiving layer is not particularly limited, and is particularly an amount that is in the range of 0.1% by mass or more and less than 10% by mass with respect to the total amount of inorganic fine particles to be described later constituting the ink receiving layer. It is preferable. Furthermore, it is more preferable that it is 0.1 mass% or more and less than 5 mass% with respect to the total amount of inorganic fine particles. When the addition amount is less than 0.1% by mass, it is not preferable because an amount necessary for decomposing a color material constituting the orange ink described later is insufficient. On the other hand, if the amount of dimethylthiourea is 10% by mass or more, the viscosity of the coating liquid at the time of forming the ink receiving layer of the recording medium is increased, and the coating property may be deteriorated.

  In the present invention, by containing inorganic fine particles in the ink receiving layer constituting the recording medium to be used, the ink absorbing ability is high, the color developing property is excellent, and a high-quality image can be formed. Specific examples of inorganic fine particles that can be used include calcium carbonate, magnesium carbonate, kaolin, clay, talc, hydrotalcite, aluminum silicate, calcium silicate, magnesium silicate, diatomaceous earth, alumina, colloidal alumina, aluminum hydroxide, boehmite. Examples thereof include alumina hydrate having a structure, and alumina hydrate having a pseudo boehmite structure, lithopone, zeolite, and the like, and these can be used alone or in combination. Among these, alumina, boehmite structure alumina hydrate, and pseudoboehmite structure alumina hydrate are preferably used.

As the form of the inorganic fine particles, in order to obtain a highly glossy and highly transparent ink-receiving layer, the average particle diameter is 50 nm to 150 nm and the polydispersity index (μ / <Γ> ² ) is 0.01. It is preferable to use the thing of the range of -0.20. More preferably, the average particle diameter of the inorganic fine particles is in the range of 80 nm to 150 nm and the polydispersity index is in the range of 0.01 to 0.15. When the average particle size of the inorganic fine particles is smaller than 50 nm, the ink absorbability of the ink receiving layer is remarkably lowered, and ink bleeding or beading may occur after printing. On the other hand, when the average particle diameter is larger than 150 nm, the transparency of the ink receiving layer is lowered, the printing density and the gloss are also lowered, and the image after printing may be dull. Also, when the polydispersity index exceeds 0.20, the transparency, print density, and gloss of the ink receiving layer are lowered as in the case of the average particle size, and the image after printing may be dull, which is not preferable. .

The average particle size and polydispersity index referred to in the present invention are measured by a dynamic light scattering method, and are “polymer structure (2) scattering experiments and morphology observation chapter 1 light scattering” (edited by the Kyoritsu Shuppan Polymer Society). ) Or an analysis using the cumulant method described in J. Chem. Phys., 70 (B), 15Apl., 3965 (1979). The dynamic light scattering method has a distribution in the decay of the time correlation function from scattered light when fine particles having different particle sizes are mixed. By analyzing this time correlation function using the cumulant method, the average of the decay rates (<Γ>) and the variance (μ) of the decay rates can be obtained. Since the decay rate (Γ) is expressed as a function of the particle diffusion coefficient and the scattering vector, the hydrodynamic average particle diameter can be obtained using the Stokes-Einstein equation. Therefore, the polydispersity index (μ / <Γ> ² ) obtained by dividing the dispersion of the decay rate (μ) by the mean square of the decay rate (<Γ> ² ) represents the degree of dispersion of the particle size. The closer to 0, the narrower the particle size distribution. The average particle size and polydispersity index defined in the present invention can be easily measured using, for example, a laser particle size analyzer PARIII (manufactured by Otsuka Electronics Co., Ltd.).

The recording medium constituting the present invention can be obtained by preparing a coating liquid containing inorganic fine particles as described above, and coating the coating liquid on the surface of a substrate to form an ink receiving layer. The ink receiving layer comprises dimethylthiourea, inorganic fine particles as described above, and a small amount of water-soluble resin and / or water-dispersible resin. With such a configuration, voids are formed in the coating layer. Therefore, the ink receiving layer of the recording medium characterizing the present invention has voids. At this time, it is preferable to use alumina or alumina hydrate having a boehmite structure or pseudoboehmite structure as the inorganic fine particles in that finer voids can be formed. In particular, it is preferable to use alumina, boehmite structure or pseudo-boehmite structure alumina hydrate having a BET specific surface area of 50 m ² / g or more.

As an alumina hydrate used for this invention, what is represented by following General formula (1) can be used, for example.
Al ₂ O _3-n (OH) _2n · mH ₂ O General formula (1)
(In the formula, n represents one of integers of 0, 1, 2 or 3, and m represents a value of 0 to 10, preferably 0 to 5.)
In many cases, mH ₂ O represents a detachable aqueous phase that does not participate in the formation of a crystal lattice, and therefore m can take a non-integer value. Also, when this type of alumina hydrate is calcined, m can reach a value of zero.

  In general, an alumina hydrate crystal having a boehmite structure is a layered compound having a (020) plane forming a giant plane, and exhibits a diffraction peak peculiar to an X-ray diffraction pattern. As the boehmite structure, in addition to perfect boehmite, a structure called excess boehmite and containing excess water between layers of the (020) plane can be taken. The pseudo-boehmite X-ray diffraction pattern shows a broader diffraction peak than the complete boehmite. Since complete boehmite and pseudoboehmite cannot be clearly distinguished, hereinafter, unless otherwise specified, in the present invention, both boehmite and alumina boehmite are referred to as alumina hydrate showing a boehmite structure.

  In the present invention, the method for producing an alumina hydrate having a boehmite structure used for forming an ink receiving layer of a recording medium is not particularly limited as long as it can produce an alumina hydrate having a boehmite structure. For example, it can be produced by a known method such as hydrolysis of aluminum alkoxide or hydrolysis of sodium aluminate.

  Further, as disclosed in JP-A-56-120508, an amorphous hydrated X-ray diffraction amorphous hydrate is heat-treated at 50 ° C. or higher in the presence of water to form a boehmite structure. It can be used by changing. As a method that can be particularly preferably used, there is a method of obtaining an alumina hydrate by adding an acid to a long-chain aluminum alkoxide, followed by hydrolysis and peptization.

  Here, the long-chain aluminum alkoxide used in the above method includes, for example, an alkoxide having 5 or more carbon atoms. In particular, when an alkoxide having 12 to 22 carbon atoms is used, as described later, Further, it is preferable because the shape control of the alumina hydrate becomes easy.

  In addition, as the acid added in the above method, one or more of organic acids and inorganic acids can be freely selected and used. The hydrolysis reaction efficiency and the obtained alumina hydrate Nitric acid is most preferably used in terms of shape control and dispersibility. It is also possible to control the particle size by performing hydrothermal synthesis after the above-described steps. When hydrothermal synthesis is performed using an alumina hydrate dispersion containing nitric acid, the nitric acid in the aqueous solution can be taken into the surface of the alumina hydrate as a nitrate radical to improve water dispersibility.

  When alumina hydrate is produced by the above method, there is an advantage that impurities such as various ions are less likely to be mixed as compared with the method of producing alumina hydrogel or cationic alumina. Furthermore, since long-chain aluminum alkoxide is easy to remove alcohol after hydrolysis, compared with the case of using short-chain alkoxide such as aluminum isopropoxide, it is possible to completely dealcoholize alumina hydrate. There is an advantage that you can.

  In addition, the dispersion of inorganic fine particles synthesized by the above method can be further made to have a desired particle size by physical means using a pulverizer and the like. As the pulverizing and dispersing machine that can be used in this case, various known dispersing machines can be used. For example, a high-pressure homogenizer, an ultrasonic homogenizer, a wet media type pulverizer (sand mill, ball mill), a continuous type Examples thereof include a high-speed stirring type disperser and an ultrasonic disperser. Specifically, Menton Gorin homogenizer, Sonator (manufactured by Doei Shoji Co., Ltd.), microfluidizer (manufactured by Mizuho Kogyo Co., Ltd.), nanomizer (manufactured by Tsukishima Kikai Co., Ltd.), optimizer (manufactured by ITOCHU SEIKI Co., Ltd.), pearl mill, glen mill, Tornado (manufactured by Asada Steel), Viscomill (manufactured by IMEX), Mighty mill, RS mill, SΓ mill (manufactured by Inoue Seisakusho), Sugawara Milder (manufactured by Sugawara Seisakusho), Fine Flow Mill, Cavitron (manufactured by Taiyo Koki Co., Ltd.), etc. Is mentioned.

  The ink receiving layer of the recording medium characterizing the present invention is prepared by adding and mixing inorganic fine particles as described above, dimethylthiourea, and further water-soluble resin and / or water-dispersible resin, This can be easily obtained by a method of applying to the surface of the substrate as mentioned above and drying it.

  The configuration of the recording medium used in the present invention is not limited as long as an ink receiving layer is formed on at least one surface of the substrate. For example, the ink receiving layer is formed on the substrate such as coated paper and coated film. Of course, these are provided continuously, but are not limited thereto. Specifically, a part or most of the coating liquid is impregnated near the surface of the substrate to form an ink receiving layer, or a small amount of coating liquid is applied to the substrate surface to receive the ink. The structure etc. which formed the layer may be sufficient. That is, in the present invention, these configurations are also included as “an ink receiving layer is formed on at least one surface of the substrate”.

  The water-soluble resin and / or water-dispersible resin that can be used for the ink receiving layer of the recording medium characterizing the present invention is not particularly limited, and any of those used for forming a conventional ink receiving layer is used. it can. For example, starch, gelatin, casein and modified products thereof, cellulose derivatives such as methylcellulose, carboxymethylcellulose, hydroxyethylcellulose, fully or partially saponified polyvinyl alcohol or modified products thereof (cationic modification, anion modification, silanol modification, etc.), urea Resin, melamine resin, epoxy resin, epichlorohydrin resin, polyurethane resin, polyethyleneimine resin, polyamide resin, polyvinylpyrrolidone resin, polyvinyl butyral resin, poly (meth) acrylic acid or copolymer thereof, Acrylamide resin, maleic anhydride copolymer, polyester resin, SBR latex, NBR latex, methyl methacrylate-butadiene copolymer latex, acrylic ester Acrylic polymer latex such as polymer, vinyl polymer latex such as ethylene-vinyl acetate copolymer, and functional group-modified polymer latex obtained by adding a cationic group or an anionic group to these various polymer latexes Etc. Preferable is polyvinyl alcohol obtained by hydrolyzing polyvinyl acetate and having a weight average polymerization degree of 300 to 5,000. The saponification degree is preferably 70 to less than 100%, particularly preferably 80 to 99.5%. In addition, these water-soluble resins and / or water-dispersible resins can be used alone or in combination.

  The amount of water-soluble resin and / or water-dispersible resin as described above is preferably used as follows for the ink-receiving layer forming material of the recording medium that characterizes the present invention. That is, the mixing mass ratio between the inorganic fine particles and the water-soluble resin and / or water-dispersible resin is preferably 1: 1 to 30: 1, more preferably 3: 1 to 20: 1. If the amount of the water-soluble resin and / or the water-dispersible resin is within these ranges, it is preferable because the formed ink-receiving layer is hardly cracked or powdered and the ink absorbability is improved.

  An aqueous medium as described below can be appropriately added to the coating liquid used for forming the ink receiving layer. For example, water or a mixed solvent of water and an organic solvent that can be mixed with water can be used. Examples of organic solvents that can be mixed with water include alcohols such as methanol, ethanol, and propanol: lower alkyl ethers of polyhydric alcohols such as ethylene glycol monomethyl ether and ethylene glycol dimethyl ether: ketones such as acetone and methyl ethyl ketone: tetrahydrofuran And ethers.

  Furthermore, for the purpose of increasing the film strength of the ink receiving layer, it is also a preferred form to add a boron compound to the coating liquid used for forming the ink receiving layer. The boron compound used at this time is an oxygen acid or a salt thereof centered on a boron atom such as boric acid or borate, and specifically includes, for example, orthoboric acid, metaboric acid, hypoboric acid. , Tetraboric acid, pentaboric acid and their salts. In general, boric acid is used as a hardener for improving the film forming property, water resistance and film strength of a film formed by a hydrophilic polymer. Various hardeners are selected depending on the type of reactive group possessed by the polymer used. For example, in the case of a polyvinyl alcohol resin, an epoxy hardener, boric acid, or a water-soluble aluminum salt is used. Inorganic hardeners such as are used.

  In the present invention, a dye fixing agent generally used for the purpose of improving the water resistance of the recording medium may be added to the coating liquid used for forming the ink receiving layer of the recording medium. Such a dye fixing agent forms a salt with the anionic group when the coloring material used in the orange ink characterizing the present invention, which will be described later, has an anionic group. The water resistance of the image can be improved by insolubilizing the material (dye).

  The solid content concentration in the case of preparing a coating liquid for forming the ink receiving layer with the above-described materials is not particularly limited as long as the concentration is such that the ink receiving layer can be formed on the substrate. Although it is not, it is preferable that it is 5-50 mass% with respect to the coating liquid total weight. When the solid content concentration is less than 5% by mass, it is necessary to increase the coating amount in order to increase the thickness of the ink receiving layer, which requires a lot of time and energy for drying, which is uneconomical. Since it may be, it is not preferable. Moreover, when it exceeds 50 mass%, since the viscosity of a coating liquid will become high and coating property may fall, it is unpreferable.

  Moreover, various additives can be mix | blended with the said coating liquid in the range which does not prevent the effect of this invention. Such additives include surfactants, pigment dispersants, thickeners, antifoaming agents, ink fixing agents, dot modifiers, colorants, fluorescent brighteners, antioxidants, UV absorbers, preservatives. And a pH adjuster.

As a method of applying the coating liquid prepared as described above onto a substrate, any known coating method can be applied, for example, blade coating method, air knife coating method, curtain coating method, slot die coating, etc. Method, bar coating method, gravure coating method, roll coating method and the like. By these coating methods, it is preferable to apply so that the dry coating amount is 0.5 to 60 g / m ² .

  After coating by the coating method as described above, the ink receiving layer can be formed by drying using a drying device such as a hot air dryer, a thermal drum, or a far infrared dryer. The ink receiving layer only needs to contain dimethylthiourea, inorganic fine particles, a water-soluble resin and / or a water-dispersible resin, and other additives used as necessary. Can be changed. In addition, the ink receiving layer characterizing the present invention is not limited to one side of the substrate, and can be formed on both sides. Further, for the purpose of improving the resolution and transportability of the image, surface smoothing may be performed using an apparatus such as a super calendar or a soft calendar.

A preferred range for the coating amount of the coating liquid on the substrate is 0.5 to 60 g / m ² in terms of solid content, and a more preferred range is 5 to 55 g / m ² . When the coating amount is less than 0.5 g / m ² , the formed ink receiving layer may not sufficiently absorb the moisture of the ink, and the ink may flow or the image may bleed. 60 g / m ² Exceeding this is not preferable because curling may occur on the recording medium during drying or a remarkable effect may not be exhibited as expected for printing performance.

<Ink>
Next, the structure of the ink used in the ink jet recording method of the present invention will be described. In the ink jet recording method of the present invention, recording is performed using a water-based ink jet recording ink containing at least an aqueous medium on a recording medium provided with the ink receiving layer having the above-described specific configuration. Is an orange ink. The ink used in the present invention only needs to contain at least an aqueous medium and an orange coloring material. More specifically, an orange ink for ink jet recording (hereinafter simply referred to as orange ink) containing an orange coloring material and water or a mixed medium of water and a water-soluble organic solvent, and further, if necessary, a surfactant. Or called ink).

(Color material)
Examples of the color material for the orange ink used in the present invention include C.I. I. Disperse Orange 13, C.I. I. Disperse Orange 29, C.I. I. Disperse Orange 31: 1, C.I. I. Disperse Orange 33, C.I. I. Disperse Orange 49, C.I. I. Disperse Orange 54, C.I. I. Disperse Orange 55, C.I. I. Disperse Orange 66, C.I. I. Disperse Orange 73, C.I. I. Disperse Orange 119, C.I. I. Disperse Orange 163, C.I. I. Acid Orange 3, C.I. I. Acid Orange 10, C.I. I. Acid Orange 56, C.I. I. Acid Orange 95, C.I. I. Acid Orange 116, C.I. I. Acid Orange 156, C.I. I. Acid Orange 168, C.I. I. Direct Orange 27, C.I. I. Direct Orange 34, C.I. I. Direct Orange 46 and C.I. I. It is preferable to use at least one selected from the group consisting of direct orange 107. These color materials may be used alone or in combination with a plurality of types of color materials.

  The content of the color material contained in the orange ink used in the present invention is preferably 0.05% by mass to 15% by mass with respect to the total mass of the ink. When the amount of the coloring material is less than 0.05% by mass, the print density of the printed matter (printed matter) is not preferable because it is low. When the amount is more than 15% by mass, the viscosity of the ink is high. Is not preferable because it becomes difficult.

(Water-soluble compounds)
The ink used in the present invention is obtained by dispersing a pigment dispersion in at least a water-soluble compound. The type of the water-soluble compound used in the present invention is not particularly limited, but the water-soluble compound is preferably at least one selected from the group of a water-soluble organic solvent and a water-soluble compound that is solid at 25 ° C.

  The “water-soluble compound” as used herein means a compound that is freely miscible with water or has a solubility in water (25 ° C.) of 20 g / 100 g or more. More specifically, it is at least one selected from the group of water-soluble organic solvents and water-soluble compounds that are solid at 25 ° C. By containing the water-soluble compound, water can be prevented from evaporating and ink sticking due to drying can be prevented.

  As the water-soluble compound, for example, various water-soluble organic solvents such as alcohols, polyhydric alcohols, glycol ethers, carboxylic acid amides, heterocycles, ketones, alkanolamines and the like described below are used. be able to. A water-soluble compound that is solid at 25 ° C., such as urea, ethylene urea, trimethylol propane, or the like can also be used.

(1) Alcohols:
Chain alcohols having 1 to 5 carbon atoms such as methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, isobutyl alcohol, tert-butyl alcohol, n-pentyl alcohol;
(2) Polyhydric alcohols:
Ethylene glycol (ethanediol), propanediol (1,2-, 1,3-), butanediol (1,2-, 1,3-, 1,4-), 1,5-pentanediol, 1,2 -Alkanediols such as hexanediol;
Condensates of alkanediols such as diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, polyethylene glycol, polypropylene glycol;
Polyhydric alcohols other than alkanediols such as glycerin, trimethylolpropane, 1,2,6-hexanetriol, thiodiglycol;
(3) Glycol ethers:
Monomethyl ether of ethylene glycol;
Monomethyl ether, monoethyl ether of diethylene glycol;
Monomethyl ether, monoethyl ether, monobutyl ether, dimethyl ether, diethyl ether of triethylene glycol;
Tetraethylene glycol dimethyl ether, diethyl ether;
(4) Carboxylic acid amides:
N, N-dimethylformamide, N, N-dimethylacetamide;
(5) Heterocycles:
Cyclic ethers such as tetrahydrofuran and dioxane;
Nitrogen-containing heterocycles such as 2-pyrrolidone, N-methyl-2-pyrrolidone, N-methylmorpholine;
Sulfur-containing heterocycles such as sulfolane;
(6) Ureas:
Ureas such as urea, ethylene urea, 1,3-dimethyl-2-imidazolidinone (N, N≡-dimethylethylene urea);
(7) Ketones:
Ketones such as acetone and methyl ethyl ketone;
Keto alcohols such as 4-hydroxy-4-methyl-2-pentanone (diacetone alcohol);
(8) Alkanolamines:
Monoethanolamine, diethanolamine, triethanolamine;
(9) Other:
Sulfur-containing compounds such as dimethyl sulfoxide and bishydroxyethyl sulfone;

  Among the water-soluble organic solvents, polyhydric alcohols are preferable, and glycerin is more preferable. Glycerin is preferable in that it hardly volatilizes and is excellent in the effect of preventing ink sticking. Moreover, the said water-soluble organic solvent may be used individually by 1 type, and 2 or more types may be mixed and used for it. For example, it is also preferable to use glycerin together with polyhydric alcohols other than glycerin and nitrogen-containing heterocycles. At this time, triethylene glycol or the like can be used as the polyhydric alcohol other than glycerin, and 2-pyrrolidone or the like can be used as the nitrogen-containing heterocyclic ring. Such a mixed solvent is preferable in that it has a high effect of preventing thickening of the ink.

  The content rate of the water-soluble organic solvent is not particularly limited. However, in order to prevent the aqueous medium from evaporating and to obtain the effect of preventing ink sticking due to drying, the content is preferably 5% by mass or more, more preferably 10% by mass or more, and still more preferably based on the total mass of the ink. Is preferably 15% by mass or more. On the other hand, from the viewpoint of being able to cope with a high driving frequency and preventing the occurrence of mold, it is preferably 50% by mass or less, more preferably 40% by mass or less, and further preferably 30% by mass with respect to the total mass of the ink. It is preferable to set it as mass% or less.

  As the water-soluble compound that is solid at 25 ° C., urea, ethylene urea or the like is preferably used, and ethylene urea is preferably used. The content of the water-soluble compound that is solid at 25 ° C. is not particularly limited. However, in order to prevent evaporation of the aqueous medium and to prevent the ink from sticking due to drying, the content is preferably 5% by mass or more, more preferably 9% by mass or more based on the total mass of the ink. . On the other hand, in order to prevent problems due to excessive addition, the content is preferably 40% by mass or less, more preferably 30% by mass or less, and particularly preferably 15% by mass or less with respect to the total mass of the ink.

(Surfactant)
In the present invention, by controlling the surface tension of the ink, which will be described later, the degree of ink bleeding and penetrability in the recording medium can be arbitrarily controlled, the ink wettability in the head can be improved, and the surface of the ink heater For the purpose of preventing the kogation and improving the discharge, a surfactant may be contained in the above-described ink as necessary. Such a surfactant is not particularly limited, and examples thereof include the following. The surfactants may be used alone or in combination.

[Nonionic surfactant]
Polyoxyethylene alkyl ether, polyoxyethylene fatty acid ester, polyoxyethylene alkylphenyl ether, polyoxyethylene / polyoxypropylene block copolymer, and the like. Fatty acid diethanolamide, acetylene glycol ethylene oxide adduct, acetylene glycol surfactant, and the like.

[Anionic surfactant]
Polyoxyethylene alkyl ether sulfate, polyoxyethylene alkyl ether sulfonate, polyoxyethylene alkyl phenyl ether sulfate, polyoxyethylene alkyl phenyl ether sulfonate, and the like. Alpha sulfo fatty acid ester salts, alkylbenzene sulfonates, alkylphenol sulfonates, alkylnaphthalene sulfonates, alkyltetralin sulfonates, dialkylsulfosuccinates and the like.

[Cationic surfactant]
Alkyltrimethylammonium salt, dialkyldimethylammonium chloride and the like.

[Amphoteric surfactant]
Alkyl carboxybetaines and the like.

  Among those listed above, acetylene glycol surfactants, polyoxyethylene alkyl ethers, and the like are particularly preferably used because they can improve the ejection stability of the ink.

  Furthermore, as an acetylene glycol surfactant suitable for the present invention, ethylene oxide of 2,4,7,9-tetramethyl-5-decyne-4,7-diol, which is a compound having a structure represented by the following general formula: Addenda may be mentioned.

（上記一般式中、Ｕ、Ｖはそれぞれ独立に１以上の整数であり、Ｕ＋Ｖは０乃至２０の整数である）

(In the above general formula, U and V are each independently an integer of 1 or more, and U + V is an integer of 0 to 20)

(water)
As water, it is preferable to use deionized water (ion exchange water). The water content is not particularly limited. However, it is preferably 30% by mass to 90% by mass with respect to the total mass of the ink, more preferably 40% by mass to 85% by mass, and still more preferably 50% by mass to 80% by mass. is there. By setting it as 10 mass% or more, a dye and a water-soluble compound can be hydrated, and aggregation of a dye or a water-soluble compound can be prevented. On the other hand, by setting the amount to 90% by mass or less, even when the amount of the water-soluble organic compound is relatively increased and the volatile component (water, etc.) in the aqueous medium is volatilized, the dissolved state of the dye is maintained. And the precipitation and solidification of the dye can be prevented.

(Other additives)
The ink may contain an additive other than the surfactant depending on the purpose. Examples of such additives include pH adjusters, rust inhibitors, antiseptics, antifungal agents, antioxidants, reduction inhibitors, salts, and the like.

(Ink viscosity)
The viscosity η of the ink used in the present invention is preferably from 1.5 mPa · s to 5.0 mPa · s, more preferably from 1.6 mPa · s to 3.5 mPa · s, still more preferably 1 It is good to set it as 0.7 mPa * s or more and 3.0 mPa * s or less. By setting the viscosity to 1.5 mPa · s or more, good ink droplets can be formed. On the other hand, by setting the pressure to 5.0 mPa · s or less, the fluidity of the ink is improved, and the ink supply property to the nozzle, and thus the ejection stability of the ink is improved.

  The viscosity of the ink described above means a value measured using an E-type viscometer (for example, “RE-80L viscometer” manufactured by Toki Sangyo Co., Ltd.) under a temperature of 25 ° C. in accordance with JIS Z 8803. It shall be. The viscosity of the ink can be adjusted by the type and amount of the water-soluble organic solvent in addition to the type and amount of the surfactant.

(Ink surface tension)
The surface tension γ of the ink used in the present invention is preferably 25 mN / m or more and 45 mN / m or less. By setting the surface tension to 25 mN / m or more, the meniscus of the ink discharge port can be maintained, and a problem that ink flows out from the ink discharge port can be prevented. In addition, by setting the surface tension to 45 mN / m or less, it is possible to optimize the absorption speed of the ink onto the recording medium, and it is possible to prevent the problem of fixing failure due to insufficient ink absorption.

  The surface tension of the ink means a value measured by a plate method using a platinum plate at a temperature of 25 ° C. and using an automatic surface tension meter (for example, “CBVP-Z type” manufactured by Kyowa Interface Science). The surface tension of the ink can be adjusted by the amount of the surfactant added, the type and content of the water-soluble organic solvent, and the like.

(Ink pH)
The pH of the ink used in the present invention is preferably 7.5 or more and 10.0 or less, more preferably 8.5 or more and 9.5 or less. When the pH is less than 7.5, the solubility of the dye is deteriorated and the aggregation of the dye is liable to occur. On the other hand, if the pH exceeds 10.0, the pH of the ink is too high, and depending on the member of the device used, a chemical attack is caused by contact with the ink, thereby causing organic and inorganic substances to elute into the ink. As a result, defective discharge is caused, which is not preferable.
The viscosity of the ink means a value measured using a pH meter (for example, HRIBA (manufactured) D-51, etc.) under a temperature of 25 ° C.

<Inkjet recording method>
The inkjet recording method of the present invention is characterized in that recording is performed using the recording medium having the above-described specific configuration and the orange ink having the above-described configuration, and once a good image is formed on the recording medium. After the formation, the inkjet recording apparatus used at that time is, for example, a general household printer mainly used for A4 size paper, a printer for printing business cards or cards, or a large business printer Is mentioned.

  As a recording method for performing suitable recording using the recording medium and ink described above, thermal energy corresponding to a recording signal is applied to each color ink accommodated in the recording head, and droplets are generated by the energy. Examples include an inkjet recording method and inkjet recording using mechanical energy. According to the present invention, since the paper can be reused by erasing the print once formed by using the orange ink, the image can be appropriately formed with a single color of the orange ink according to the purpose of printing. Other than that, the same ink jet recording method as the conventional one can be used. Hereinafter, an example of an inkjet recording apparatus capable of realizing the inkjet recording method of the present invention to which the above-described inkjet recording method is applied will be described.

<Inkjet recording apparatus>
An ink jet recording apparatus suitable for carrying out the present invention includes a recording head for ink jet recording having the following configuration, and an ink containing portion (ink tank) for containing ink to be supplied to the recording head. And an inkjet recording apparatus provided. Hereinafter, the configuration of the recording head, the ink tank, and the entire apparatus, which are the main parts, will be described.
[1] Recording head:
Hereinafter, an example of the recording head will be described with reference to the drawings. However, the recording head is not limited to the configuration described below.

[1-1] Structure of nozzle portion:
First, the structure of the nozzle portion will be described with reference to FIGS. 1A to 1C. FIG. 1A is a top view schematically showing the internal structure of the nozzles of the recording head. FIG. 1B is a side view schematically showing the internal structure of the nozzle shown in FIG. 1A. FIG. 1C is a front view schematically showing an ink discharge port of the nozzle shown in FIG. 1A.

  As shown in the figure, the thermal recording head has a nozzle row composed of a plurality of nozzle flow paths 159 partitioned by a nozzle wall 153, and a plurality of ink discharge ports 151 communicating with the nozzle flow paths 159. An ink discharge heater 152 is disposed inside the nozzle flow path 159. The head having such a structure can cause ink droplets to fly from the ink discharge ports 151 by heating the ink filled in the nozzle flow path 159 with the heater 152 and causing the ink to foam.

  In the illustrated form, a nozzle filter 155 is provided between the nozzle channel 159 and the common liquid chamber 112 for trapping foreign matter floating in the ink channel in the head. The top plate member 113 to which the nozzle top plate 162 is attached has an ink supply opening (not shown) formed by anisotropic etching or the like, and introduces ink from the outside from the common liquid chamber 112 to the nozzle channel 159. It is configured to be possible.

  In addition to the right and left side surfaces of the nozzle channel 159 being partitioned by the nozzle wall 153, the upper surface side is partitioned by the nozzle top plate 162 and the bottom surface side is partitioned by the nozzle bottom plate 164. That is, the nozzle flow path 159 is a substantially rectangular columnar internal space partitioned from the surrounding space by using the nozzle wall 153, the nozzle top plate 162, and the nozzle bottom plate 164 as partitions. The nozzle top plate 162 is attached to a top plate member 113 made of Si or the like, and the nozzle bottom plate 164 is attached to the heater substrate 111.

The ink discharge port 151 is an opening that discharges ink formed at one end of the nozzle flow path 159 and communicates with the common liquid chamber 112 via the nozzle flow path 159. The ink discharge port 151 is formed on the face surface. In the illustrated example, the face surface is formed integrally with the nozzle wall 153, but a face plate may be separately provided to form the face surface. The opening area of the ink ejection port 151 is configured to be 100 μm ² or more and 350 μm ² or less. By setting the opening area to 100 μm ² or more, it is possible to prevent the occurrence of an undischarge nozzle. On the other hand, by setting it to 350 μm ² or less, it is possible to form minute droplets in which the amount of one ink droplet is 10 pL or less, and the resolution can be 600 dpi or more. The opening area is represented by the product of the discharge port width 171 and the discharge port height 172.

  The recording head is a line type head in which nozzle rows are formed by a plurality of nozzle flow paths. The number of nozzle flow paths forming the nozzle row is not particularly limited. However, in order to achieve the effect of the present invention, the total number of nozzles in the nozzle row needs to be 1200 or more, preferably 1200 or more and 9600 or less, and more preferably 1200 or more and 4800 or less. . The length of the nozzle row needs to be 2 inches or more, and preferably 2 inches or more and 4 inches or less.

  The heater 152 is a heating unit for heating and foaming the ink filled in the nozzle channel 159. The heater 152 is installed on the heater substrate 111. As the heater 152, a resistor (for example, a resistor made of tantalum nitride) can be used. An electrode (not shown) made of aluminum or the like for energization is connected to the heater 152, and a switching transistor (not shown) for controlling energization to the heater 152 is connected to one of the heaters 152. . The drive of the switch transistor is controlled by an IC including a circuit such as a control gate element, and the switch transistor is driven in a predetermined pattern by a signal from the outside of the head.

  The recording head can be driven at a driving frequency of 1 kHz to 10 kHz. By driving at a driving frequency of 1 kHz or more, even when the amount of ink per droplet is very small, the amount of ink applied per unit time can be increased, and the amount of image data and the number of recording dots can be increased. That is, a high-quality image can be printed at high speed. By driving at a driving frequency of 10 kHz or less, such a problem that the ink supply amount to the nozzle is insufficient with respect to the ink discharge amount at the time of high-speed printing as described above and the ejection stability is reduced is suppressed. In order to obtain the effect more reliably, it is preferable that the driving can be performed at a driving frequency of 3 kHz or more and 8 kHz or less. The recording head is also preferably capable of being driven at a driving frequency of 6 kHz or more and 10 kHz or less because ejection stability is unlikely to deteriorate even under a high driving frequency and nozzle ejection is difficult to occur.

  The overall length of the nozzle is preferably 200 μm or more and 300 μm or less. In this case, the “total length of the nozzle” means the length of the nozzle flow path 159, specifically, the common liquid chamber 112 from the end of the nozzle wall 153 constituting the nozzle flow path 159 on the ink discharge port 151 side. It means the length to the end of the side.

  The nozzle flow path 159 includes a nozzle front portion 181 that is a portion from the heater center 157 to the end portion on the ink discharge port 151 side, and a nozzle rear portion 182 that is a portion from the heater center 157 to the end portion on the common liquid chamber 112 side. It is divided into. From the viewpoint of the discharge speed, the flow resistance (front resistance) of the nozzle front part 181 and the flow resistance (rear resistance) of the nozzle rear part 182 have a front resistance / rear resistance value of 0.3 to 0.8. It is preferable. The flow resistance can be calculated by the Hagen-Poiseuille law from values such as the cross-sectional area of the flow path, the flow path length, and the viscosity of the ejected ink. That is, if the ink to be used (and its viscosity) is determined, the value of the front resistance / rear resistance can be adjusted by the flow path cross-sectional area of the nozzle, the flow path length, and the like.

[1-2] Nozzle material:
The nozzle wall 153, the nozzle top plate 162, and the nozzle bottom plate 164 that partition the nozzle flow path 159 can be formed of, for example, a photosensitive resin. As the photosensitive resin, a negative photoresist or the like can be used. Specific commercial products include, for example, “SU-8 series”, “KMPR-1000” (above, manufactured by Kayaku Microchem Corp.), “TMMR”, “TMMR S2000”, “TMMF S2000” (above, Tokyo Ohka). (Manufactured by Kogyo Co., Ltd.). Among these, it is preferable to use an epoxy photosensitive resin excellent in solvent resistance and strength as a nozzle wall. As a specific commercial product, “TMMR S2000” manufactured by Tokyo Ohka Kogyo Co., Ltd. is particularly preferable.

[1-3] Hydrophilic region and water-repellent region:
The recording head preferably has a hydrophilic region or a water-repellent region formed at the periphery of the ink discharge port. Which of the hydrophilic region and the water repellent region is formed may be determined in consideration of the type of the color material of the ink to be used and the surface tension.

  For example, when the color material is a pigment or when an ink having a surface tension of 34 mN / m or less is used, a recording head (hydrophilic head) in which a hydrophilic region is formed at the periphery of the ink discharge port is preferable. Further, it is preferable that a hydrophilic region having a contact angle of 60 ° or less with the ink to be used is formed at the periphery of the ink discharge port. The hydrophilic region having the contact angle of 0 ° (that is, forming no contact angle). It is more preferable that a sex region is formed.

  The hydrophilic region includes a method in which a member (face material) in which ink discharge ports are formed is made of a hydrophilic material, a method in which a surface of the face material (face surface) is subjected to a hydrophilic treatment, and a hydrophilic film on the face surface. It can form by the method of providing.

  As the face material, for example, a resin such as an epoxy resin, particularly an epoxy-based photosensitive resin can be used.

Examples of the method for hydrophilic treatment of the face surface include a method of roughening the face surface. Examples of the roughening method include laser irradiation treatment, UV / O ₃ treatment, plasma treatment, heat treatment, oxidation treatment, and embossing treatment. Lasers such as excimer laser, YAG laser, and CO ₂ laser can be used for the laser irradiation treatment. Alternatively, the peripheral portion of the ink discharge port may be treated by a method of immersing in a highly hydrophilic liquid for a long time. Examples of the “hydrophilic liquid” include pigment inks. For example, what is necessary is just to immerse in the pigment ink which uses a face material for 10 minutes or more.

  Examples of a method for providing a hydrophilic film on the face surface include a method of forming a metal film or a hydrophilic resin film on the face surface. The hydrophilic film is preferably formed of a material having good adhesion to the face material as well as hydrophilicity. Examples of such a material include a composition containing a water-soluble resin and a water-insoluble low molecular weight compound. For example, a water-soluble resin (such as hydroxypropylcellulose) and a water-insoluble low molecular weight compound (such as bisphenol A) are dissolved in a suitable solvent (such as dimethylformamide), and the solution is applied to the face and dried. Accordingly, a hydrophilic film can be formed by treatment with alcohol or the like.

The formation of the hydrophilic region may be appropriately selected from the above methods according to the material constituting the face material. In addition, the hydrophilic region may be formed by combining two or more of the above methods. Among the above methods, a method in which the peripheral portion of the nozzle is made of an epoxy-based photosensitive resin, and the peripheral portion of the nozzle is subjected to a UV / O ₃ treatment and further immersed in pigment ink to perform a hydrophilic treatment.

  For example, when the color material is a dye and an ink having a surface tension of more than 34 mN / m is used, a recording head (water-repellent head) in which a water-repellent region is formed at the periphery of the ink discharge port is provided. preferable. Further, it is more preferable that a water-repellent region having a contact angle of 90 ° or more with the ink to be used is formed at the periphery of the ink discharge port, and a water-repellent region having a contact angle with the ink to be used of 100 ° or more. It is particularly preferred that it is formed.

  The water repellent region can be formed by a method of providing a water repellent film on the surface (face surface) of the member (face material) on which the ink discharge ports are formed.

  Examples of the method for providing the water repellent film on the face surface include a method of forming a super water repellent resin film on the face surface. The super water-repellent resin film can be formed by a conventionally known method. For example, a method of forming a resin film by applying a fluororesin, a silicone resin or the like on the face surface, a method of forming a fluororesin film by plasma polymerizing a fluorine-based monomer on the face surface, and the like can be given. Further, a method of forming a water- and oil-repellent resin film on the face surface may be employed. Examples thereof include a method of forming a film made of a fluororesin obtained by polymerizing a fluorocarbon compound. Among them, fluorine-containing silicones are used in fluorine-based solvents (“CXT-809A” manufactured by Asahi Glass, “<Novec> HFE-7100”, “<Novec> HFE-7200”, “<Novec> HFE-71IPA”, etc., manufactured by Sumitomo 3M Ltd.). A method of forming a water-repellent film by preparing a solution in which a coupling agent (for example, “KP-801M” manufactured by Shin-Etsu Chemical Co., Ltd.) is dissolved and vapor-depositing this solution on the face surface is preferable.

[1-4] Overall structure of recording head:
Next, the overall structure of the recording head will be described with reference to FIGS. 2A to 2C. A recording head having a structure as shown in FIGS. 2A to 2C is disclosed in Japanese Patent Laid-Open No. 2013-014111. Therefore, in the present specification, the contents of the above publication are cited, and only an outline thereof is described. 2A is a front view schematically showing the recording head, FIG. 2B is a cross-sectional view taken along the line AA in FIG. 2A, and FIG. 2C is a cross-sectional view taken along the line BB in FIG. 2A. For convenience of explanation, the liquid supply case cover is omitted from the front view.

  As shown in the drawing, the recording head of the present invention includes a common liquid chamber 112 that communicates with a plurality of nozzle channels forming a nozzle row, a liquid supply port 127 that communicates with the common liquid chamber 112, and a liquid type head. A main liquid supply chamber 126 that communicates with the supply port 127, a liquid supply path 137 that communicates with the main liquid supply chamber 126, and a liquid supply chamber that communicates with the liquid supply path 137 (the first liquid supply chamber 134 and the second liquid supply chamber). 135), a supply filter 118 disposed so as to separate the liquid supply chamber into the first liquid supply chamber 134 and the second liquid supply chamber 135 from the upstream side along the flow in supplying the liquid, and the main liquid It is preferable that a gas-liquid separator 120 provided in a part of the supply chamber 126 and an air chamber 141 communicating with the gas-liquid separator 120 are provided.

  The nozzle channel, the common liquid chamber 112, the liquid supply port 127, the main liquid supply chamber 126, the liquid supply path 137, and the liquid supply chamber (the first liquid supply chamber 134 and the second liquid supply chamber 135) The supply filter 118, the gas-liquid separator 120, and the air chamber 141 are arranged on a plane parallel to the plane including the nozzle channel arrangement direction and the liquid discharge direction, and the main liquid supply chamber 126. The liquid supply path 137, the supply filter 118, the gas-liquid separation unit 120, and the air chamber 141 are preferably arranged without being stacked.

  The recording head having the structure shown in FIGS. 2A to 2C is referred to as a gas-liquid separation type recording head. Since the gas-liquid separation type recording head fills the nozzles with ink by utilizing its own weight, it is extremely difficult to ensure the ejection stability as compared with the recording head having a conventional structure. Therefore, it can be said that the gas-liquid separation type recording head is one of the forms in which the effects of the present invention can be most enjoyed.

  A ceramic base plate 110 supports a heater substrate 111 formed of silicon. The heater substrate 111 has a plurality of electrothermal transducers (heaters or energy generators) as liquid discharge energy generating elements and a plurality of flow path walls for constituting nozzles corresponding to these electrothermal transducers. Is formed. The heater substrate 111 is also formed with a liquid chamber frame surrounding the common liquid chamber 112 communicating with each nozzle. A top plate member 113 that forms the common liquid chamber 112 is joined on the side wall of the nozzle and the liquid chamber frame formed in this manner. Therefore, the heater substrate 111 and the top plate member 113 are laminated and bonded to the base plate 110 in an integrated state. Such lamination adhesion is performed with an adhesive having good thermal conductivity such as silver paste. A mounted electrical wiring board (PCB 114) is supported by a double-sided tape (not shown) behind the heater board 111 in the base plate 110. Each ejection energy generating element on the heater substrate 111 and the PCB 114 are electrically connected by wire bonding corresponding to each wiring.

  A liquid supply member 115 is joined to the top surface of the top plate member 113. The liquid supply member 115 includes a liquid supply case 116 and a liquid supply case cover 117. When the liquid supply case cover 117 closes the upper surface of the liquid supply case 116, a liquid chamber and a liquid supply path to be described later are formed. . The liquid supply case 116 and the liquid supply case cover 117 are joined by, for example, a thermosetting adhesive. The liquid supply case 116 is provided with a supply filter 118 and a discharge filter 119. The supply filter 118 is intended to remove foreign matters in the liquid supplied to the liquid supply member 115, and the discharge filter 119 is intended to prevent foreign matters from entering from the outside of the recording head. Each filter is fixed to the liquid supply case 116 by heat welding. Furthermore, a gas-liquid separation unit 120 is formed in a part of the liquid supply case 116, and a liquid level detection sensor 121 is mounted from the outside so as to protrude from the gas-liquid separation unit 120. Control the amount.

  Here, the configuration of the liquid chamber, the liquid supply path, and the like formed by fitting the two parts of the liquid supply case and the 116 liquid supply case cover 117 will be described. A liquid supply port 127 that is a rectangular opening is formed on the joint surface of the liquid supply case 116 with the top plate member 113 and is substantially parallel to the nozzle arrangement direction and across the width of the nozzle row. A storage liquid main liquid supply chamber 126 is formed on the extension of the mouth 127. That is, the main liquid supply chamber 126 is formed substantially parallel to the nozzle row and across the width of the nozzle row. Further, the top surface on the side opposite to the liquid supply port 127 constitutes an inclination (main liquid supply chamber inclination 129) with the gas-liquid separation part 120 as the uppermost portion over almost the entire area. Two openings are formed in the main liquid supply chamber inclination 129, one being the liquid communication part 131 and the other being the gas-liquid separation part 120.

  The gas-liquid separator 120 is formed as a part of the main liquid supply chamber 126 and has a depth larger than that of the other parts of the main liquid supply chamber 126. This is to enhance the effect of breaking bubbles that are mixed in the liquid in the liquid chamber, as will be described later. In the illustrated form, three stainless steel electrodes are mounted inside the gas-liquid separator 120, and are an upper limit detection electrode 123, a ground electrode 124, and a lower limit detection electrode 125 from the left side in the figure. The liquid level in the main liquid supply chamber 126 is maintained between the upper limit and the lower limit by energization between the ground electrode 124 and the upper limit detection electrode 123 and energization between the ground electrode 124 and the lower limit detection electrode 125. In the inkjet head of the illustrated form, the detection reliability can be improved by detecting the liquid level of the liquid that has undergone gas-liquid separation.

  On the extension of the gas-liquid separation unit 120, there is an air communication unit 130, and the tip is an air chamber 141 that functions as an air flow path. Further, the above-described discharge filter 119 is disposed and communicates with the discharge joint 133. The discharge filter 119 is made of a material having water repellency. If a liquid flows into the air flow path (air chamber 141) and the ink adheres to the discharge filter 119, an ink meniscus is formed inside the filter. However, the capillary force of the filter portion can be reduced by the water repellency, and the ink can be easily removed.

  On the other hand, a liquid supply path 137 is provided via a liquid communication portion 131 provided in the main liquid supply chamber inclination 129. The liquid supply path 137 has a tubular shape from the liquid communication portion 131 to the vicinity of the supply filter 118 and is formed on substantially the same plane as the main liquid supply chamber 126. The supply filter 118 is also disposed on substantially the same plane as the main liquid supply chamber 126. The supply filter 118 is disposed so as to separate the liquid supply chamber into two chambers. The chamber on the side communicating with the supply joint 132, that is, the upstream chamber along the flow of liquid supply in the recording head is the first liquid supply. The chamber 134 and the downstream chamber are the second liquid supply chamber 135. Since the supply filter 118 is disposed on substantially the same plane as the main liquid supply chamber 126, the first liquid supply chamber 134 and the second liquid supply chamber 135 adjacent to both surfaces of the supply filter 118 are also the main liquid supply chamber. 126 and the ink discharge port array surface 139 are arranged on a plane substantially parallel to the surface.

  The second liquid supply chamber 135 has an opening above the supply filter 118 (hereinafter referred to as a second liquid supply chamber opening 136), and communicates with the liquid supply path 137 through the opening. In addition, the top surface of the second liquid supply chamber 135 is formed with an inclination (hereinafter referred to as a second liquid supply chamber inclination 138) with this opening as the uppermost portion.

  As described above, the main liquid supply chamber 126, the gas-liquid separator 120, the liquid supply path 137, the supply filter 118, the first liquid supply chamber 134, and the second liquid supply chamber 135 are each substantially the same as the ink discharge port arrangement surface 139. Set on a parallel plane. On the other hand, as shown in the AA cross section, it is important to arrange the main liquid supply chamber 126, the liquid supply path 137, the supply filter 118, and the gas-liquid separator 120 so as not to overlap each other in the vertical direction of the plane.

The supply filter 118 is preferably a stainless steel mesh having a filter pore diameter of 1 μm to 10 μm and a filter area of 10 mm ^{2 to} 500 mm ² . By setting the filter hole diameter to 1 μm or more and the filter area to 10 mm ² or more, the flow path resistance (pressure loss) can be reduced, and the bubbles in the recording head can be easily moved. In order to obtain the above effect more reliably, the filter area is more preferably 200 mm ² or more. On the other hand, when the filter hole diameter is 10 μm or less, dust can be reliably prevented from flowing into the nozzle, and when the filter area is 500 mm ² or less, the recording head can be downsized. In order to obtain the effect more reliably, it is more preferable that the filter pore diameter is 3 μm or more and 8 μm or less.

[1-5] Ink filling:
In this recording head, ink for ink jet recording is filled in an internal space communicating with the ink discharge port of the line type head. The ink is preferably filled in at least a portion from the ink discharge port to the common liquid chamber (that is, the nozzle flow path and the common liquid chamber) in the internal space.

[2] Ink tank:
FIG. 3 is an enlarged sectional view of the ink tank. The ink tank 230 is a liquid storage container, and a liquid chamber (ink chamber 231) for storing ink is formed therein. The ink chamber 231 is a closed space in which only the joint portion 232 can communicate with the outside. The ink tank 230 is configured to be detachable from the recording head. The ink tank 230 is provided in the upper part of the recording head. The ink chamber 231 is formed of a flexible member, and a negative pressure generating spring 233-1 and a pressure plate 233-2 connected to the spring 233-1 are incorporated therein. The spring 233-1 urges the ink chamber 231 from the inside to the outside via the pressure plate 233-2, and expands the internal space of the ink chamber 231. That is, the spring 233-1 generates a predetermined negative pressure inside the ink chamber 231, and the spring 233-1, the pressure plate 233-2, and the ink chamber 231 together constitute a negative pressure generating unit 233. ing. The joint portion 232 is provided with a non-woven filter 234.

  FIG. 4 is an enlarged cross-sectional view of the recording head. The recording head 220 includes an energy generation element (not shown) such as an electrothermal conversion element (ink ejection heater). By this energy generating element, the ink I in the ink chamber 221 (liquid in the liquid chamber) is discharged from the discharge port 220A. In the ink chamber 221, air (gas) is present together with the ink I. Therefore, in the ink chamber 221, an ink storage part (liquid storage part) in which the ink I is stored and an air storage part (gas storage part) in which air (gas) is stored are formed. .

  An ink supply unit 222 for connecting the ink chamber 221 and the ink chamber of the ink tank is provided above the ink chamber 221. The average width of the ink supply unit 222 is about 10 mm. A filter member 223 is provided at the opening of the ink supply unit 222. The illustrated filter member 223 is formed of a SUS mesh. The mesh has a structure in which metal fibers are woven. Since the filter member 223 has fine eyes, it is difficult for dust to enter the recording head from the outside.

  The lower surface of the filter member 223 is pressed against an ink holding member 224 that can hold ink. 5A is an enlarged perspective view of the ink holding member shown in FIG. 4, and FIG. 5B is a Vb-Vb sectional view of the ink holding member shown in FIG. 5A. As shown in FIGS. 5A and 5B, the ink holding member 224 has a plurality of channels 224A having a circular cross section. The diameter of each flow path 224A is about 1.0 mm.

  As shown in FIG. 4, an opening 225 is provided in the upper part of the ink chamber 221. The opening 225 is provided with a filter 226. The opening 225 is configured to be connectable to a transfer unit (not shown) that is an external flow path. This transfer part is a flow path capable of transferring liquid and / or gas. The opening 225 allows the ink I and / or gas in the ink chamber 221 to flow out, or allows liquid (such as ink) and / or gas outside the recording head 220 to flow into the ink chamber 221. It is configured. That is, the opening 225 is formed so that not only the liquid can flow out and flow in alone, but also the gas can flow out and flow in with the liquid.

  The ink tank 230 shown in FIG. 3 and the recording head 220 shown in FIG. 4 are directly connected by connecting the joint part 232 of the ink tank 230 shown in FIG. 3 and the ink supply part 222 of the recording head 220 shown in FIG. Connected. At this time, the filter 234 of the ink tank 230 shown in FIG. 3 and the filter member 223 of the recording head 220 shown in FIG. 4 are in pressure contact with each other from above and below. The connecting portion between the ink tank and the recording head formed in this manner is surrounded by a rubber elastic cap member to maintain hermeticity. The structure in which the recording head and the ink tank are directly connected as described above is preferable in that the ink supply path (liquid supply path) between them can be extremely shortened.

[3] Overall configuration of recording apparatus:
Other structures of the ink jet recording apparatus are not particularly limited. For example, a recording apparatus 300 as shown in FIG. 6 can be suitably used.

  FIG. 6 is a schematic configuration diagram schematically showing the overall configuration of the ink jet recording apparatus. An external host device (computer device 308) is connected to the recording device 300. The recording apparatus 300 is configured to record an image by ejecting ink from the recording head 305 based on the recording data input from the computer apparatus 308.

  In the recording apparatus 300, a label sheet temporarily attached with a plurality of labels is used as the recording medium 301. The recording medium 301 is set in a state wound in a roll shape. However, in the ink jet recording apparatus of the present invention, any material can be used as long as it can accept not only paper, but also ink such as cloth, plastic film, metal plate, glass, ceramics, wood, and leather. Can be used.

  The recording apparatus 300 includes a conveyance motor 303, a conveyance roller 302, a rotary encoder 310, and a roll motor 311 as conveyance means for conveying the recording medium 301. By driving the conveyance roller 302 by the conveyance motor 303, the recording medium 301 can be conveyed at a constant speed in the direction of arrow A. The rotary encoder 310 can detect the conveyance speed and conveyance amount of the recording medium 301. The roll motor 311 can rewind the recording medium 301 in the direction opposite to the arrow A direction. The paper detection sensor 304 is a sensor that detects a specific portion of the recording medium 301. In the illustrated example, the tip of each label temporarily attached to the label sheet is detected. The recording timing of the image can be determined based on the detection.

  The recording apparatus 300 includes four recording heads 305 and ink tanks 306 corresponding to the four recording heads 305 at the top thereof. The four recording heads are recording heads for ejecting black, cyan, magenta, and yellow ink, respectively.

  The recording head 305 is a so-called line-type head configured to be wider than the maximum width recording width of the recording medium 301 and includes a plurality of nozzles that can eject ink. The ink discharge port of the nozzle is opened on the lower surface side of the recording head 305. The recording head 305 is disposed so that its longitudinal direction intersects with the conveyance direction of the recording medium 301 (direction orthogonal to the arrow A in the figure), and a plurality of nozzles are arranged along the longitudinal direction. As a result, a nozzle row is formed.

  In the recording apparatus 300, the conveyance roller 302 is driven by the conveyance motor 303, and the recording medium 301 is conveyed at a constant speed in the direction of arrow A by the conveyance roller 302. When a specific portion of the recording medium 301 is detected by the paper detection sensor 304, ink is sequentially discharged from the ink discharge ports of the four recording heads 305 based on the detection position. At this time, ink is supplied from the ink tank 306 to the recording head 305. Thus, when the recording medium 301 passes under the recording head 305, ink is ejected from the plurality of nozzles of the recording head 305, and an image is recorded on the recording medium 301. Note that since the recording head 305 is a line-type head, ink is ejected while being fixed at a fixed position. That is, ink is not ejected while reciprocating left and right like a serial head.

  The recording apparatus 300 includes a capping mechanism 307, a blade 309, and the like as a recovery mechanism for performing a recovery operation of the recording head 305.

  The recovery operation is an operation for recovering the recording head 305 so as to exhibit an appropriate ejection performance similar to the initial state. For example, operations such as suction recovery, pressure recovery, preliminary discharge, and wipe recovery can be given. The suction recovery is an operation of sucking and removing the thickened ink in the nozzles of the recording head 305 to the capping mechanism 307, and the pressure recovery is pressurizing the thickened ink in the nozzles of the recording head 305 to the capping mechanism 307. Preliminary ejection is an operation that discharges the thickened ink in the nozzles to the capping mechanism 307 by ejection, and stabilizes the ink meniscus. Wipe recovery means that the face surface of the recording head is wiped by the blade 309. In this operation, dust and ink attached to the face surface are removed. These recovery operations can also be implemented in combination.

  The capping mechanism 307 is a mechanism for capping the ink discharge port of each recording head 305 and is disposed below the recording head 305. The recording head 305 and the capping mechanism 307 are configured to be relatively movable in the left-right direction in FIG. On the other hand, the blade 309 is a member that wipes the face surface of each recording head 305, and is disposed below the recording head 305.

  When performing suction recovery, the inside of the buffer tank (not shown) of the capping mechanism 307 is decompressed by a tube pump (not shown) while the recording head 305 is capped by the capping mechanism 307. As a result, the thickened ink in the nozzles of the recording head 305 is removed by suction to the capping mechanism 307, and the nozzles are refreshed.

  When pressure recovery is performed, the inside of the nozzles of the recording head 305 is pressurized while the recording head 305 is capped by the capping mechanism 307. As a result, the thickened ink in the nozzle is pressurized and discharged into the cap of the capping mechanism 307, and the inside of the nozzle is refreshed.

  When performing wipe recovery, the blade 309 is driven by a blade motor (not shown), the face of the nozzle of the recording head 305 is wiped, and pressure recovery (preliminary ejection) is performed. Thereby, the face surface of the nozzle is cleaned, and the meniscus at the ink discharge port is adjusted.

  The ink accumulated in the capping mechanism 307 by these recovery operations is sucked by a tube pump (not shown) and discarded in a waste ink tank (not shown) when it is accumulated to a predetermined amount.

[4] Control system:
Next, control of the ink jet recording apparatus will be described. FIG. 7 is a block diagram of the control system of the recording apparatus shown in FIG. In addition to a recording mechanism including a recording head, the recording apparatus includes a control system component such as a CPU (Central Processing Unit), a USB interface unit, and a ROM. The CPU 401 executes a program stored in the program ROM 402 and controls each unit of the recording apparatus. A program ROM 402 stores programs and data for controlling the recording apparatus. The processing of the recording apparatus is realized by the CPU 401 reading and executing a program in the program ROM 402.

  The recording data output from the computer device 308 is input to the interface controller 403 of the recording device. Commands that specify the number, type, size, and the like of the recording medium (label) are also input to the interface controller 403 and analyzed. In addition to analyzing these commands, the CPU 401 executes arithmetic processing for controlling the entire recording apparatus, such as recording data input, recording operation, and recording medium handling. The arithmetic processing is executed based on a processing program stored in the program ROM 402. The program includes a program corresponding to the procedure of the flowchart shown in FIG. A work RAM 404 is used as a working memory for the CPU 401. The EEPROM 405 is a rewritable nonvolatile memory. This EEPROM 405 is specific to the recording apparatus, such as the time when the previous recovery operation was performed, the mutual distance of a plurality of recording heads, and the correction value for finely adjusting the recording position in the transport direction (vertical registration). Parameters are stored.

  More specifically, after analyzing the input command, the CPU 401 develops the image data of each color component of the recording data in the image memory 406 as a bitmap. Drawing is performed based on this data. Further, the CPU 401 controls the transport motor 303, the roll motor 311, the capping motor 409, the head motor 410, and the pump motor 418 via the input / output circuit 407 and the motor driving unit 408. The capping motor 409 is a motor for driving the capping mechanism 307, the head motor 410 is a motor for moving the recording heads 305K, 305Y, 305M, and 305C, and the pump motor 418 is a motor for driving the tube pump. It is. The recording heads 305K, 305Y, 305M, and 305C are moved between the capping position, the recording position, and the recovery position. The capping position is a position capped by the capping mechanism 307, the recording position is a position for recording an image, and the recovery position is a position for performing a recovery operation.

  When an image is recorded by the recording apparatus, the conveyance roller 302 is driven by the conveyance motor 303 as shown in FIG. 6 to convey the recording medium 301 (label paper in the illustrated example) at a constant speed. The rotary encoder 310 detects the conveyance speed and conveyance amount of the recording medium 301. In the control system shown in FIG. 7, the leading edge of the label is detected by the paper detection sensor 304 in order to determine the recording timing of the image on the recording medium conveyed at this constant speed. A detection signal from the paper detection sensor 304 is input to the CPU 401 via the input / output circuit 411. When the recording medium is conveyed by the conveyance motor, the CPU 401 sequentially reads out image data for each color from the image memory 406 in synchronization with a signal from a rotary encoder (not shown). The image data is transferred to one of the corresponding recording heads 305K, 305Y, 305M, and 305C via the recording head control circuit 412. Accordingly, the recording heads 305K, 305Y, 305M, and 305C eject ink based on the image data.

  The driving of the pump motor 413 for driving the pump is controlled via the input / output circuit 407 and the motor driving unit 408. The operation panel 414 is connected to the CPU 401 via the input / output circuit 415. Further, the environmental temperature and environmental humidity of the recording apparatus are detected by a temperature / humidity sensor 416 and input to the CPU 401 via the A / D converter 417.

[5] Recovery sequence:
When the environmental temperature is 40 ° C. or higher and the water evaporates, the ink sticks easily to the recording head. Accordingly, it is preferable to insert a recovery sequence for recovering the face surface of the recording head when the head cap is removed from the recording head and the moisture evaporates.

  FIG. 8 is a flowchart showing the steps of the printhead recovery sequence. The recovery sequence shown in FIG. 8 is activated when a cap opening condition (condition 501) in which the recording head is released from the cap is satisfied. When the recovery sequence is activated, the environmental temperature and the environmental humidity of the recording apparatus are acquired (detected) by the temperature / humidity sensor (step 502). As a result of the detection, when the environmental temperature is 40 ° C. or more, the environmental humidity is 70% or less (condition 503), and the cumulative time from the previous suction recovery is one hour or more (condition 504), the inside of the nozzle Pressure recovery (preliminary ejection) for refreshing the ink and wipe recovery for wiping and cleaning the face surface are performed (step 505). The condition 504 is reset when suction recovery is performed.

[6] Inkjet recording method:
The ink jet recording method of the present invention is characterized in that recording is performed by using the ink jet recording apparatus as described above and driving the recording head at a driving frequency of 1 kHz to 10 kHz. As described above, by driving at a drive frequency of 1 kHz or higher, it is possible to increase the amount of ink applied per unit time and print a high-quality image at high speed. On the other hand, by driving at a driving frequency of 10 kHz or less, it is possible to suppress a problem that the ink supply amount to the nozzle is insufficient with respect to the ink discharge amount and the discharge stability is lowered even during high-speed printing. In order to obtain the effect more reliably, it is preferable that the driving frequency is 3 kHz or more and 10 kHz or less. Further, according to the recording method of the present invention, even when the recording head is driven at a high driving frequency of 6 kHz or more and a driving frequency of 10 kHz or less, the ejection stability is unlikely to deteriorate and nozzle non-discharge is unlikely to occur.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. In the following text, “parts” and “%” are based on mass unless otherwise specified.

<Production of alumina hydrate>
Aluminum dodexide was prepared by the method described in US Pat. No. 4,242,271. Next, aluminum alkoxide was hydrolyzed to produce an alumina slurry by the method described in US Pat. No. 4,202,870. Water was added to the alumina slurry until the solid content of alumina hydrate having a boehmite structure was 7.7%. The pH of the alumina slurry obtained above was 9.4. The pH was adjusted to 6.0 by adding 3.9% nitric acid solution.

  Next, using an autoclave, aging was performed at pH before aging: 6.0, aging temperature: 150 ° C., aging time: 6 hours to obtain a colloidal sol. The colloidal sol was spray-dried at 87 ° C. to obtain an alumina hydrate powder having a boehmite structure. Further, an alumina hydrate dispersion was prepared by adding and mixing the alumina hydrate having the boehmite structure in ion-exchanged water to a concentration of 19%.

  The dispersion obtained by the above method was redispersed by passing it through an ultrasonic oscillation unit of an ultrasonic homogenizer MUS-600CCVP-12 (manufactured by Nippon Seiki Seisakusho Co., Ltd.) at a flow rate of about 1 l / min. After repeating this redispersion operation 1 to 5 times, coarse particles are removed by centrifugation, and finally ion-exchanged water is added to adjust the solid content concentration to 17%. A dispersion A of alumina hydrate was obtained.

<Example 1>
(Manufacture of recording medium 1)
100 parts of the alumina hydrate dispersion A obtained above and 1.7 parts of polyvinyl alcohol (PVA-235, manufactured by Kuraray Co., Ltd.) dissolved in 15.3 parts of water are mixed, and N, N'- Add 0.51 parts of dimethylthiourea (3.0% with respect to alumina hydrate) and 0.34 parts (2.0% with respect to alumina hydrate) of 3% -boric acid aqueous solution in terms of solid content. A coating solution for forming an ink receiving layer was prepared. Next, the resin-coated paper is used as a base material, and the coating liquid prepared above is applied onto the base material by a bar coating method so as to have a dry coating amount of 45 g / m ^2, and then at 100 ° C. for 30 minutes. The ink receiving layer was formed by hot air drying. The recording medium thus obtained was designated as recording medium 1.

(Preparation of orange ink 1)
Next, orange ink 1 was prepared as follows. Specifically, the components shown below are mixed in the following formulation, dissolved by sufficiently stirring, and then filtered under pressure with a microfilter (manufactured by Fuji Film) having a pore size of 0.2 μm to obtain an orange ink. 1 was obtained. Note that acetylenol E100 (trade name) manufactured by Kawaken Fine Chemical Co., Ltd. was used as the acetylene glycol ethylene oxide adduct as a surfactant added to the ink component.
・ C. I. Acid Orange 3 3.0 parts, Glycerol 10 parts, Diethylene glycol 4 parts, Acetylene glycol ethylene oxide adduct 1 part, Ion-exchanged water 82 parts

(Evaluation)
The orange ink 1 obtained above is mounted on an ink-jet recording apparatus P-660CII (manufactured by Canon Finetech) having an on-demand type multi-recording head that discharges ink by applying thermal energy corresponding to a recording signal to the ink. Solid printing was performed on the recording medium 1 manufactured previously with a printing speed of 5.3 m / min, a resolution of 600 dpi × 600 dpi, and an ink amount of 100%. And the following evaluation was performed using the obtained printed matter, and the obtained result is shown in Table 1.

[Evaluation method for fading / discoloration suppression effect]
About the printed matter obtained above, the degree of decoloring by light irradiation was tested as follows to evaluate the fading / discoloration suppressing effect of the printed matter. The sample was placed in a light resistance tester (made by Suga Test Instruments Co., Ltd., special order) and exposed for 30 hours under the conditions of xenon irradiation intensity: 0.63 W / m ² 23 ° C., 60% RH. The optical density (Optical Density: hereinafter abbreviated as OD) (measured density value of the surface printed part) before and after light irradiation was measured using an optical reflection densitometer (RD-918, manufactured by Gretag Macbeth Co., Ltd.). It was measured. Then, the amount of change in optical density (residual OD ratio = optical density after irradiation / optical density before irradiation × 100) was calculated from each measured value, and evaluated based on the following criteria. The evaluation results are shown as “residual OD rate” in Table 1.

(Evaluation criteria)
◎: Residual OD rate = 0 to less than 5% ○: Residual OD rate = 5 to less than 10% △: Residual OD rate = 10 to less than 70% ×: Residual OD rate = 70 to less than 100%

<Example 2>
C.I. used in the preparation of the orange ink 1 of Example 1 I. Orange ink 2 was prepared in the same manner except that the amount of acid orange 3 added was 1.0 part and the amount of ion-exchanged water added was 84 parts. Solid printing was performed in the same manner as in Example 1 except that the orange ink 2 obtained above was used. And the same evaluation was performed about printed matter, and the result was shown in Table 1.

<Example 3>
C.I. used in the preparation of the orange ink 1 of Example 1 I. Acid Orange 3 I. Orange ink 3 was prepared in the same manner except that the amount was changed to Direct Orange 27 and the addition amount was 7.0 parts and the addition amount of ion-exchanged water was 78 parts. Solid printing was performed in the same manner as in Example 1 except that the orange ink 3 obtained above was used. And the same evaluation was performed about printed matter, and the result was shown in Table 1.

<Comparative Example 1>
The N, N′-dimethylthiourea used in forming the ink receiving layer of the recording medium 1 used in Example 1 is changed to thiourea, and the recording medium 2 for comparison is the same as the recording medium 1. Manufactured. Using the obtained recording medium 2, C.I. I. Solid printing was performed in the same manner as in Example 1 except that the amount of Acid Orange 3 was changed to 1.5 parts and orange ink adjusted with water was used. And the same evaluation was performed about printed matter, and the result was shown in Table 1.

<Comparative Example 2>
C.I. used in the preparation of the orange ink 1 of Example 1 I. Acid Orange 3 I. Red ink was prepared in the same manner except that it was changed to Acid Red 16 and the addition amount was 1.5 parts and adjusted with water. Solid printing was performed in the same manner as in Example 1 except that the red ink obtained above was used. And the same evaluation was performed about printed matter, and the result was shown in Table 1.

<Comparative Example 3>
A comparative recording medium 3 was produced in the same manner except that the N, N′-dimethylthiourea used in forming the ink receiving layer of the recording medium 1 used in Example 1 was not added. Solid printing was performed in the same manner as in Example 1 except that the obtained recording medium 3 was used. And the same evaluation was performed about printed matter, and the result was shown in Table 1.

  From the above examples and comparative examples, dimethylthiourea added to the recording medium acts as a light-proofing agent for light-colored inks other than orange ink by light irradiation. It was confirmed that the material acts as a substance that promotes light fastness that specifically increases the decomposition rate of the color material. As can be seen from the evaluation results of Examples and Comparative Examples shown in Table 1, it was confirmed that the printed image formed by the method of the present invention was decolored by light irradiation.

  As an application example of the ink jet recording method of the present invention, the printed matter formed by the method of the present invention is decolored in a certain time by natural light such as sunlight, which is effective for the formation of a temporarily required printed matter. By using the method of the present invention, it becomes possible to repeatedly use printing paper, which is problematic for mass use, and its use is expected.

  110: base plate, 111: heater substrate, 112: common liquid chamber, 113: top plate member, 115: liquid supply member, 116: liquid supply case, 117: liquid supply case cover, 118: supply filter, 119: discharge filter, 120: Gas-liquid separator, 121: Liquid level detection sensor, 123: Upper limit detection electrode, 124: Ground electrode, 125: Lower limit detection electrode, 126: Main liquid supply chamber, 127: Liquid supply port, 129: Main liquid supply chamber Inclination, 130: air communication part, 131: liquid communication part, 132: supply joint, 133: discharge joint, 134: first liquid supply chamber, 135: second liquid supply chamber, 136: second liquid supply chamber opening, 137 : Liquid supply path, 138: second liquid supply chamber inclination, 139: ink discharge port arrangement surface, 141: air chamber, 151: ink discharge 152: heater, 153: nozzle wall, 155: nozzle filter, 157: heater center, 159: nozzle flow path, 162: nozzle top plate, 164: nozzle bottom plate, 171: discharge port width, 172: discharge port height, 181: nozzle front part, 182: nozzle rear part, 220: recording head, 220A: ejection port, 221: ink chamber, 222: ink supply part, 223: filter member, 224: ink holding member, 224A: flow path, 225 : Opening, 226: Filter, 230: Ink tank, 231: Ink chamber, 232: Joint part, 233: Negative pressure generating part, 2333-1: Spring, 233-2: Pressure plate, 234: Filter, 300: Recording Device 301: recording medium 302: transport roller 303: transport motor 304: paper detection sensor 305 305K 05Y, 305M, 305C: recording head, 306: ink tank, 307: capping mechanism, 308: computer device, 309: blade, 310: rotary encoder, 311: roll motor, 401: CPU, 402: program ROM, 403: interface Controller, 404: Work RAM, 405: EEPROM, 406: Image memory, 407: Input / output circuit, 408: Motor drive unit, 409: Capping motor, 410: Head motor, 411: Input / output circuit, 412: Print head control Circuit, 413: Pump motor, 414: Operation panel, 415: Input / output circuit, 416: Temperature / humidity sensor, 417: A / D converter, 418: Pump motor, 501: Condition, 502: Process, 503: Condition, 504: Condition 5 05: Process, I: Ink.

Claims (3)

  An aqueous inkjet recording ink comprising at least an aqueous medium on a recording medium provided with an ink receiving layer containing inorganic fine particles and a water-soluble resin and / or a water-dispersible resin on at least one surface of a substrate A recording method configured to perform inkjet recording using an ink, wherein the ink receiving layer of a recording medium contains dimethylthiourea, and the inkjet recording ink is an orange ink containing an orange coloring material. An ink jet recording method, comprising:   The inkjet recording method according to claim 1, wherein the inorganic fine particles are at least one of alumina, a boehmite structure, or an alumina hydrate having a pseudo boehmite structure.   The orange coloring material is C.I. I. Disperse Orange 13, C.I. I. Disperse Orange 29, C.I. I. Disperse Orange 31: 1, C.I. I. Disperse Orange 33, C.I. I. Disperse Orange 49, C.I. I. Disperse Orange 54, C.I. I. Disperse Orange 55, C.I. I. Disperse Orange 66, C.I. I. Disperse Orange 73, C.I. I. Disperse Orange 119, C.I. I. Disperse Orange 163, C.I. I. Acid Orange 3, C.I. I. Acid Orange 10, C.I. I. Acid Orange 56, C.I. I. Acid Orange 95, C.I. I. Acid Orange 116, C.I. I. Acid Orange 156, C.I. I. Acid Orange 168, C.I. I. Direct Orange 27, C.I. I. Direct Orange 34, C.I. I. Direct Orange 46 and C.I. I. The inkjet recording method according to claim 1, wherein the inkjet recording method is at least one selected from the group consisting of direct orange 107.

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