Ink, ink-jet recording method, and ink-jet recording apparatus

Abstract: Provided is an ink for ink-jet recording, comprising a dye, water, and the components (a), (b), and (c) below: (a) at least one surfactant selected from the group consisting of higher alcohol-ethylene oxide adducts represented by General Formula [1], alkylphenol-ethylene oxide adducts represented by General Formula [2], ethylene oxide-propylene oxide copolymers represented by General Formula [3], and acetylene glycol-ethylene oxide adducts represented by General Formula [4], at a content of from 0.1 to 20 % by weight; R-O-(CH₂CH₂O) n -H [1] where R is alkyl, and n is an integer; where R is alkyl, and n is an integer; where R is alkyl, and n and ℓ are respectively an integer; where m and n are respectively an integer; (b) thiodiglycol; and (c) urea or an derivative thereof.

Description: BACKGROUND OF THE INVENTION Field of the invention The present invention relates to an ink which provides excellent color recording on plain paper such as wood-free paper, medium-quality paper, bond paper, and paper for copying. The present invention also relates to an ink-jet recording method, and an ink-jet recording apparatus employing the above ink. Related Background Art Personal computers including desk-top types, lap-top types, and book types have come to employ a color display unit in recent years. Software is also directing to color representation. Consequently, printers are changing from monocolor types to color types. Among recording methods employed by such printers, ink-jet recording is attracting attention. In the ink-jet recording, ink droplets are ejected and are attached to a recording medium such as paper sheets, converted paper sheets, plastic films, and cloths without contact of a recording head with the recording medium. The ink-jet recording method is advantageous in that noise is not produced because of non-contact of the recording head with the recording medium, and high speed printing and color recording is practicable. In the ink-jet recording method, it is required that (1) ink does not cause running of ink at the recorded portion on the recording medium, (2) ink is sufficiently stable during storage, and (3) the safety is high. In color ink-jet recording, it is further required that (4) mixing (or bleeding) of different colors of inks caused by unfixed ink droplets does not occur on contact of different color inks on a recording medium, (5) a solid color portion is uniform in color, and (6) failure of ink ejection does not occur after interruption of ink ejection (first-ejection difficulty), since limited colors of inks are more frequently used in color printing unlike monocolor printing. Conventional inks for writing implements such as for use in a marking pen, a ball-point pen and the like are, for example, known from the JP-A-56-167 775 and JP-A-59-045 372. The former reference discloses the addition of a dye, water and a specific acetylene derivative, and the latter reference discloses the inclusion of (thio)urea derivative, a dye, water and a preservative as essential components of the water-based ink composition. However, conventional inks per se are not usable as inks for color recording because they cause serious bleeding and do not give high-quality images. Presumably, the bleeding is caused by the fact that the ink is dotted before the previously dotted different color of ink has been sufficiently fixed. Coat paper, which has high ink-absorbing ability, is used for color recording in order to prevent the bleeding. Further, for printing on plain paper such as paper for copying and bond paper, a printing method reflecting upon the fixing time of ink is proposed in which ink is dotted after the previously dotted ink droplet has been fixed. In such a printing method, speed of paper feed have to be slowed down disadvantageously, thereby the printing time becomes longer irrespectively of the ink-dotting method. Therefore, high speed printing which is characteristic of ink-jet recording cannot be practised with such a printing method. To shorten the fixing time, Japanese Patent Application Laid-Open No. 55-29546 discloses a method in which a surfactant is incorporated into ink in a larger amount than usual and thereby the ink seems to become dry instantaneously owing to the increased penetration power of ink afforded by the surfactant. However, the simple addition of a surfactant in a larger amount as above cannot prevent mixing of different colors of inks at the border of colors even though it improves the ink fixation. Moreover, it augments penetration of ink toward the back face of the paper, which lowers color density on the paper face, or causes nonuniform dyeing of a fiber layer on the paper surface, resulting in irregularity of color density in solid printing area and deterioration of image quality. Furthermore, feathering and ink fixation on a plain paper are improved by use of strongly alkaline ink (see Japanese Patent Application Laid-Open No. 56-57862, etc.), or by use of a specific kind of ink (see Japanese Patent Application Laid-Open No. 56-5871, etc.). These inks, however, do not always prevent bleeding satisfactorily, and even in the case where the bleeding is relatively slight,, the feathering is conspicuous (not satisfying the aforementioned requirement (1) of the prior art) or ejection failure is liable to occur (not satisfying the aforementioned requirement (6) of the prior art). As above, no color ink has been obtained which satisfies all the above requirements and gives high quality of an image with high speed on plain paper. SUMMARY OF THE INVENTION The present invention intends to provide an ink for ink-jet recording which is capable of forming a color image of high quality at high and uniform color density on a usual recording medium such as plain paper without feathering or ink-bleeding, and especially without mixing of different colors of inks at the color border. The present invention also intends to provide an ink-jet recording method, and an ink-jet recording apparatus employing the above ink. According to a first aspect of the present invention, there is provided an ink for ink-jet recording which contains a dye and water, and further comprises the components (a), (b), and (c) below: (a) at least one surfactant selected from the group consisting of higher alcohol-ethylene oxide adducts represented by General Formula [1], alkylphenol-ethylene oxide adducts represented by General Formula [2], ethylene oxide-propylene oxide copolymers represented by General Formula [3], and acetylene glycol-ethylene oxide adducts represented by General Formula [4], at a content of from 0.1 to 20 % by weight based on the total weight of the ink; R-O-(CH 2 CH 2 O) n -H where R is alkyl, and n is an integer; where R is alkyl, and n is an integer; where R is alkyl or hydrogen, and n and ℓ are respectively an integer; where m and n are respectively an integer; (b) thiodiglycol at a content of from 1 to 30% by weight; and (c) urea or a derivative thereof at a content of 1 to 30% by weight. According to a second aspect of the present invention, there is provided an ink-jet recording method which conducts recording on a recording medium with droplets of ink, which comprises dye, water, and the aforementioned components (a), (b), and (c). According to a third aspect of the present invention, there is provided a color ink-jet recording method which conducts recording by ejecting droplets of inks of two or more colors to adjacent or superposed positions on a recording medium, using the ink comprising a dye, water and the aforementioned components (a), (b), and (c). BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 shows an example of the pattern of dotting of different color inks. Fig. 2 shows another example of the pattern of dotting of different color inks. Fig. 3 is a longitudinal cross-sectional view of a head portion of an ink-jet recording apparatus of the present invention. Fig. 4 is a transverse cross-sectional view of a head portion of an ink-jet recording apparatus of the present invention. Fig. 5 is a perspective view of a head portion of an ink-jet recording apparatus of the present invention. Fig. 6 is a perspective view of an ink-jet recording apparatus of the present invention. Fig. 7 is a longitudinal sectional view of an ink cartridge of the present invention. Fig. 8 is a perspective view of a recording unit of the present invention. Fig. 9 is a perspective view of a recording portion in which a plurality of recording heads are arranged and which was used in an example of the present invention. Fig. 10 is a perspective view of another recording head used in the present invention. DESCRIPTION OF THE PREFERRED EMBODIMENT The inventors of the present invention have studied comprehensively a method of color image formation which does not cause bleeding of ink and gives a uniform color image without irregularity of colors. As the result, it has been found that an ink containing the components (a), (b), and (c) below is extremely effective: (a) at least one surfactant selected from the group consisting of higher alcohol-ethylene oxide adducts represented by General Formula [1], alkylphenol-ethylene oxide adducts represented by General Formula [2], ethylene oxide-propylene oxide copolymers represented by General Formula [3], and acetylene glycol-ethylene oxide adducts represented by General Formula [4], at a content of from 0.1 to 20 % by weight; R-O-(CH 2 CH 2 O) n -H where R is alkyl, and n is an integer; where R is alkyl, and n is an integer; where R is alkyl or hydrogen, and n and ℓ are respectively an integer; where m and n are respectively an integer; (b) thiodiglycol, at a content of from 1 to 30% by weight; and (c) urea or an derivative thereof, at a concentration of from 1 to 30% by weight. The inks of the invention are effective for formation of uniform images without bleeding or color irregularity presumably from the reasons below. The most important factor which affects prevention of ink bleeding and uniformity of color of recorded images is considered to be the wettability of a recording medium by the ink, or a wetting power of the ink on the recording medium. Among the recording media, plain paper especially has fibers exposed on the recording surface, and the fiber density on the surface is not uniform. At the portion where the fiber density is high, the ink fixation is slow, whereby ink bleeds or color of an image becomes irregular. The ink which has a sufficient wetting power is considered to be fixed uniformly irrespectively of the paper fiber density, and to be free from bleeding and color irregularity. Further, the ink which has excellent wetting power is considered to form precisely circular dots with uniformity of color, thereby providing images of higher quality. The invention of the present invention will be described in detail. The wetting power of the ink relates closely to the interaction between the ink and the recording material at the interface. Addition of a surfactant generally decreases the interfacial tension between the ink and the recording medium, and improves the wetting power of the ink. In particular, the nonionic surfactant having ethylene oxide chain as the component (a) of the first invention, when incorporated in the ink, the hydrophilic ethylene oxide portion of the surfactant presumably orients toward the recording medium to give a specific uniform wettability. On the contrary, an ionic surfactant, which has a hydrophilic portion which has less affinity with the recording medium than the nonionic surfactant, does not exhibit such effect. The ethylene oxide addition type nonionic surfactant in the present first invention is preferably added in an amount of from 0.1 to 20 %, more preferably from 0.1 to 5 % by weight based on the weight of the ink. The wetting power is not sufficient at the amount of the surfactant of less than 0.1 % by weight, while, addition of the surfactant in an amount exceeding 20 % by weight does not improve more the wetting property and is disadvantageous in production cost and ink reliability. The addition number of the ethylene oxide unit, the hydrophilic portion, in the ethylene oxide addition type nonionic surfactant in the present first invention is preferably in the range of from 4 to 20, more preferably from 4 to 10 in terms of "n" or "n+m" in consideration of the affinity of the ethylene oxide moiety with the recording medium and orientation thereon. At the value of "n" or "n+m" of less than 4, the solubility of the surfactant is not sufficient to achieve the effect of the present invention, while at the value of more than 20, the excessive ethylene oxide is not necessarily effective and leads to slightly unstable ink ejection. The medium for the aforementioned ethylene oxide addition type nonionic surfactant is described below. Generally, the ethylene oxide addition type nonionic surfactant is inconvenient for stabilization of ink ejection because of its relatively high viscosity in consideration of ejection stabilization. Therefore, an additional water-soluble organic solvent is studied to improve the ink ejection without impairing the effects of the present invention. Consequently, thiodiglycol has been found to be satisfactory. The failure of ink ejection is caused generally by rise of viscosity resulting from vaporization of water at the nozzle. The use of thiodiglycol is considered to reduce more the rise of the viscosity than other solvents, thereby improving the ejection property. However, single use of thiodiglycol is not sufficiently effective yet for ejection stabilization. After comprehensive study, it has been found that combined use of thiodiglycol and urea or a derivative of urea improves greatly the ink ejection property. Presumably, the interaction between the thiodiglycol and urea or a urea derivative suppresses the rise of the viscosity specifically, and the dissolution of a dye is improved. The thiodiglycol and a urea derivative-thiourea derivative are used respectively in an amount of from 1 to 30 % by weight. The amount of water used in the present first invention is preferably in the range of from 50 to 85 %, more preferably from 55 to 75 % by weight. If the amount of water is less than 50 %, the viscosity of the ink is relatively high, and the ejection stability tends to be relatively lower, even when thiodiglycol or urea or derivative thereof is used concurrently. If the amount of water is more than 85 %, the ethylene oxide portion, which is the hydrophilic portion of the ethylene oxide addition type nonionic surfactant, is relatively free, resulting in less orientation thereof and less uniformity. The water-soluble organic solvents constituting the ink of the present first invention include polyalkylene glycols such as polyethylene glycol, and polypropylene glycol; alkylene glycols having 2 to 6 carbon atoms such as ethylene glycol, propylene glycol, butylene glycol, triethylene glycol, hexylene glycol, and diethylene glycol; glycerin; 1,2,6-hexanetriol; lower alkyl ether of polyhydric alcohols such as ethylene glycol methyl ether, diethylene glycol methyl (or ethyl) ether, and triethylene glycol monomethyl (or ethyl) ether; alcohols such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, t-butyl alcohol, isobutyl alcohol, benzyl alcohol, and cyclohexanol; amides such as dimethylformamide, and dimethylacetamide; ketones and ketone alcohols such as acetone, and diacetone alcohol; ethers such as tetrahydrofuran, and dioxane; and nitrogen-containing heterocyclic ketones such as N-methyl-2-pyrrolidone, 2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone. The water-soluble organic solvent may be incorporated in such an amount that the ink-bleeding is not caused and the ejection property is not impaired. Among the above solvents, preferred are ethylene glycol, triethylene glycol, hexylene glycol, diethylene glycol, glycerin, ethyl alcohol, isopropyl alcohol, cyclohexanol, and so forth. The solvent preferably is contained in an amount of from 1 to 15 % by weight based on the total weight of the ink. The dyes employed in the present invention include direct dyes, acid dyes, reactive dyes, disperse dyes, vat dyes, and the like. The content of the dye is decided depending on the kinds of the liquid medium components and the required properties of the ink, and is generally in the range of from 0.5 to 15 %, preferably from 1 to 7% by weight based on the total weight of the ink. The main constituents of the ink of the present first invention are described above. Other additives may be incorporated provided that the objects of the invention are achievable. The additive includes viscosity-adjusting agents such as polyvinyl alcohol, celluloses, and water-soluble resins; pH-controlling agents such as diethanolamine, triethanolamine, and buffer solutions; fungicides; and so forth. To the ink of electrically chargeable type used for ink-jet recording in which the ink droplets are charged, a resistivity-adjusting agent is added such as lithium chloride, ammonium chloride, and sodium chloride. The inks of the present invention are suitable for ink-jet recording in which the ink droplets are ejected by action of thermal energy. However, the inks are naturally useful also for other types of ink-jet recording and for general writing implements. The recording apparatus suitable for recording with the ink of the present invention includes those in which thermal energy is given to the ink in a chamber in a recording head in correspondence with recording signals and thereby ink droplets are formed. A recording apparatus is described below which produces ink droplets by thermal energy and is suitable for practising the recording of the present invention. The present invention is suitable for the recording system in which recording signal is applied to a recording ink in a recording head and ink droplets are ejected by the action of the generated thermal energy. The construction of the recording head, which is the main portion of the apparatus, is shown in Figs. 3, 4, and 5. A head 13 is constructed by bonding a plate of glass, ceramics, or plastics having an ink flow path to a heat-generating head 15. (The head is shown in the drawing, but the invention is not limited to this.) The heat-generating head 15 is constituted of a protection layer 16 formed of silicon oxide or the like, aluminum electrodes 17-1 and 17-2, a heat-generating resistance layer 18 formed of nichrome or the like, a heat accumulation layer 19, and a substrate plate 20 made of aluminum or the like having a high heat-radiating property. Ink 21 reaches the ejection orifice 22, forming a meniscus 23 by action of pressure P not shown in the drawing. On application of an electric signal to the electrodes 17-1 and 17-2, the region designated by a symbol "n" on the heat-generating head 15 generates abruptly heat to form a bubble in the portion of the ink 21 contacting therewith. The pressure generated by the bubble pushes out the meniscus 23 and ejects the ink 21 from the orifice 22 in a form of ink droplets 24, and the ink droplets are ejected to a recording medium 25. Fig. 5 shows a rough sketch of a multiple recording head constructed by juxtaposing a multiplicity of heads shown in Fig. 3. The recording head is prepared by bonding a glass plate 27 having a plurality of flow paths to a heat-generating head 28 similar to the one shown in Fig. 3. Incidentally, Fig. 3 is a cross-sectional view of the head 13 along an ink flow path, and Fig. 4 is a cross-sectional view of the head at the line A-B in Fig. 3. Fig. 6 illustrates an example of the ink-jet recording apparatus having such a head mounted therein. In Fig. 6, a blade 61 as a wiping member is held at one end by a blade-holding member, forming a fixed end in a shape of a cantilever. The blade 61 is placed at a position adjacent to the recording region of the recording head, and is constituted such that it moves in the direction perpendicular to the moving direction of the recording head to come into contact with the ejection nozzle face to cap the nozzles. An ink absorption member 63 is provided at a position adjacent to the blade 61, and is held so as to protrude into the moving path of the recording head in a manner similar to that of the blade 61. The aforementioned blade 61, the cap 62, and the absorption member 63 constitute an ejection-recovery section 64. The blade 61 and the absorption member 63 remove water, dust, and the like from the ink ejecting nozzle face. A recording head 65 has an ejection energy-generating means for ejection, and conducts recording by ejecting ink onto a recording medium opposing to the ejection nozzle face. A carriage 66 is provided for supporting and moving the recording head 65. The carriage 66 is engaged slideably with a guide rod 67. A portion of the carriage 66 is connected (not shown in the drawing) to a belt 69 driven by a motor 68, so that the carriage 66 is movable along the guide rod 67 to the recording region of the recording head 65 and the adjacent region thereto. A paper delivery portion 51 for delivery of a recording medium and a paper delivery roller 52 driven by a motor (not shown in the drawing) delivers the recording medium to the position opposing to the ejecting nozzle face of the recording head, and the recording medium is discharged with the progress of the recording to a paper discharge portion provided with paper-discharging rollers 53. In the above constitution, when the recording head 65 returns to a home position at the completion of the recording or other timing, the cap 62 of the ejection-recovery portion 64 is positioned out of the moving path of the recording head 65, and the blade 61 is made to protrude into the moving path. Therefore, the ejecting nozzle face of the recording head 65 is wiped therewith. The cap 62 moves to protrude toward the moving path of the recording head when the cap 62 comes into contact with the ejecting nozzle face of the recording head for capping. At the time when the recording head 65 moves from the home position to the record-starting position, the cap 62 and the blade 61 are at the same position as in the above-mentioned wiping time, so that the ejection nozzle face of the recording head is wiped also in this movement. The recording head moves to the home position not only at the end of the recording and at the time of ejection recovery, but also at a predetermined interval during movement for recording in the recording region. By such movement, the wiping is conducted. Fig. 7 illustrates an example of the ink cartridge that contains ink to be supplied through an ink supplying member such as a tube. The ink container portion 40, for example an ink bag, contains an ink to be supplied, and has a rubber plug 42 at the tip. By inserting a needle (not shown in the drawing) into the plug 42, the ink in the ink bag 40 becomes suppliable. An ink absorption member 44 absorbs waste ink. The ink container portion has preferably a liquid-contacting surface made of polyolefin, particularly preferably made of polyethylene. The ink-jet recording apparatus used in the present invention is not limited to the above-mentioned one which has separately a head and an ink cartridge. Integration thereof as shown in Fig. 8 may suitably be used. In Fig. 8, a recording unit 70 houses an ink container portion such as an ink absorption member, and the ink in the ink absorption member is ejected from a head 71 having a plurality of orifices. The ink absorption member may be made of a material such as polyurethane. An air-communication opening 72 is provided to communicate interior of the cartridge with the open air. The recording unit 70 may be used in place of the recording head shown in Fig. 6, and is readily mountable to and demountable from the carriage 66. An ink-jet recording apparatus which ejects ink droplets by action of thermal energy to the ink is exemplified above. The present invention, however, is applicable also to other ink-jet recording apparatuses such as the one of piezo type which employs a piezoelectric element. For practising the recording according to the present invention, a recording apparatus, for example, is used which has four in number of recording heads shown in Fig. 5 juxtaposed on a carriage. Fig. 9 shows an example of the apparatus. Recording heads 81, 82, 83, and 84 are recording heads ejecting respectively recording inks of yellow, magenta, cyan, and black. The heads are mounted on the aforementioned recording apparatus, and eject respective color inks in accordance with recording signals. The apparatus in Fig. 9 employs four recording heads, but the present invention is not limited thereto. One recording head may be constructed to ejects all of the yellow, magenta, cyan, and black inks as shown in Fig. 10. The present invention is described in more detail by reference to Examples and Comparative Examples. In the description, the terms "parts" and "%" are based on weight unless otherwise mentioned. Hereinafter, the ethylene oxide adduct is simply referred to as "EO adduct". The dyes and liquid medium in an amount (parts) shown below are employed in the Example and Comparative Example to provide each 100 parts of inks, respectively. Example 1 Each of the four color compositions was stirred sufficiently, and was filtered under pressure through a Fluoropore Filter (trade name, made by Sumitomo Electric Industries, Ltd.) having a pore diameter of 0.22 µm to prepare the ink of the present invention. The respective inks were introduced into a color ink-jet printer BJC-820J (tarde name, made by Canon K.K.) which conducts recording by forming ink droplets by applying thermal energy to the inks in the recording heads, and recording was conducted on commercial paper sheets for copying (Canon NP Dry SK), and bond paper sheets (Plover Bond Paper PB). Evaluation was made as described below. The results are shown in Table 1. (1) Bleeding: Color samples were prepared by printing such that different colors are adjacent to each other, and the occurrence of bleeding was evaluated by the standard below. The evaluation was made for seven colors: black, yellow, cyan, and magenta; and red, green, and blue formed by dotting in superposition of two colors taken from the colors of yellow, cyan, and magenta. o : No bleeding is observed at every boundary. ▵ : Bleeding is remarkable at the boundaries of red, green, and blue where a larger amount of ink is applied. X : Bleeding is remarkable at nearly all the boundaries. (2) Color uniformity: Uniformity at solid color print portions are examined visually. o : Solid color print is completely uniform without irregularity. ▵ : Nonuniformity is remarkable at the portion where fiber density is high. X : Color irregularity is much more remarkable. (3) Occurrence of feathering: Three hundred dots are printed continuously on a commercial paper sheet for copying and a commercial bond paper sheet such that the dots are not brought into contact with each other. The dotted ink are dried in the air for 24 hours at room temperature. Irregular shape and irregular feathering of dots are counted under microscope. The evaluation is made by the percentage of the counted dot number according to the standard below: o ○ : not more than 10 % o : 11 % to 30 % ▵ : 31 % to 50 % X : not less than 51 % (4) Ejection property: The ink to be tested is filled to the printer, and alphabet and numeral letters are printed continuously for 10 minutes with the printer. Thereafter, printer is left standing without capping of the nozzles. After 10 minutes of intermission of the printing, the printing is started again. The ejection property is evaluated from scratches and unsharped edges in printed letters after restarting the printing. o : No scratch and no unsharped edge is observed from the first letter. ▵ : A part of the first letter is scratched or unsharped. X : The first letter cannot be printed. (5) Storage stability: The ink is placed in an amount of 100 mℓ in a heat-resistant glass bottle, stoppered tightly, and stored in a thermostatic chamber at 60°C. After 2 months of storage, the ink is used for printing, and evaluated. o : No abnormality is observed. X : Failure of discharge, or irregularity or discoloration of printed letters is observed. (6) Anti-Clogging (crusting recovery): The ink to be tested is filled to the printer, and alphabet and numeral letters are printed continuously for 10 minutes with the printer. Thereafter, printer is left standing without capping of the nozzles. After one month of intermission of the printing, ejection recovery operation was conducted. The evaluation was made by counting the required number of times of the ejection recovery operations for carrying out normal printing. o : Printing is normal after 1 to 5 times of ejection recovery operation. Δ : Printing is normal after 6 to 10 times of ejection recovery operation. X : Printing is normal after 11 or more times of ejection recovery operation. Examples 2 to 5 In respective Examples, the kind and the amount of the dyes used were as below: (Dyes for Examples 2 to 4) Black: C.I. Food Black 2 2 parts Dye A 1.2 parts Dye B 0.8 part Yellow: C.I. Direct Yellow 86 2.5 parts Cyan: C.I. Direct Blue 199 3.5 parts Magenta: Dye C 3.5 parts (Dyes for Example 5) Black: C.I. Food Black 2 2 parts Dye A 1.2 parts Dye B 0.8 part Yellow: C.I. Direct Yellow 86 2.5 parts Cyan: C.I. Acid Blue 9 3.0 parts Magenta: Dye C 3.5 parts The liquid mediums used in respective Examples were as below: (Liquid medium for Example 2) Thiodiglycol 7.5 parts Urea 7.5 parts Glycerin 7.5 parts Nonylphenyl ether-EO adduct (n =9 to 10) 5 part Pure water balance (Liquid medium for Example 3) Thiodiglycol 7.5 parts Thiourea 7.5 parts Glycerin 7.5 parts Ethylene oxide-propylene oxide copolymer (n=10, L=7) 15 parts Pure water balance (Liquid medium for Example 4) Thiodiglycol 7.5 parts Urea 7.5 parts Glycerin 7.5 parts Acetylene glycol-EO adduct (n+m = 10) 5 parts Pure water balance (Liquid medium for Example 5) Thiodiglycol 7.5 parts Urea 7.5 parts Glycerin 7.5 parts Acetylene glycol-EO adduct (n+m = 4) 1 parts Pure water balance In the above, as acetylene glycol-EO adduct, Acetylenol (made by Kawaken Fine Chemical K.K.), as the nonylphenyl ether-EO adduct, Emulgen 909 (made by Kao Corporation), and as the ethylene oxide-propylene oxide copolymer, Karpole MH-50 (made by Asahi Denka Kogyo K.K.) are used, respectively. The respective inks were prepared with the dye and the liquid medium shown above in the same manner as in Example 1. Printing properties, ejection properties, and the storage stability of the inks were evaluated in the same manner as in Example 1. The results are shown in Table 1. Comparative Examples 1 to 5 In respective Comparative Examples, the kind and the amount of the dyes were are as below: (Dyes for Comparative Examples 1 to 5) Black: C.I. Food Black 2 2 parts Dye A 1.2 parts Dye B 0.8 part Yellow: C.I. Direct Yellow 86 2.5 parts Cyan: C.I. Direct Blue 199 3.5 parts Magenta: Dye C 3.5 parts The liquid mediums used in respective Comparative Examples were as below: (Liquid medium for Comparative Example 1) Thiodiglycol 7.5 parts Urea 7.5 parts Glycerin 7.5 parts Pure water balance (Liquid medium for Comparative Example 2) Thiodiglycol 15 parts Glycerin 7.5 parts Acetylene glycol-EO adduct (n+m = 10) 5 parts Pure water balance (Liquid medium for Comparative Example 3) Urea 10 parts Glycerin 12.5 parts Acetylene glycol-EO adduct (n+m = 10) 5 parts Pure water balance (Liquid medium for Comparative Example 4) Thiodiglycol 7.5 parts Urea 7.5 parts Glycerin 7.5 parts Anionic surfactant (Neopelex 25, made by Kao Corporation) 7 parts Pure water balance (Liquid medium for Comparative Example 5) Thiodiglycol 7.5 parts Urea 7.5 parts Glycerin 7.5 parts Cationic surfactant (Cation DDC-50, made by Sanyo Chemical Industries, Ltd.) 5 parts Pure water balance The respective inks were prepared with the dye and the liquid medium shown above in the same manner as in Example 1. Printing properties, ejection properties, and the storage stability of the inks were evaluated in the same manner as in Example 1. The results are shown in Table 1. Evaluation item (1) (2) (3) (4) (5) (6) Examples 1 o o o o o o o o o 2 o o o o o o o o o 3 o o o o o o o o o 4 o o o o o ○ o ○ o o o 5 o o o o o ○ o ○ o o o Comparative examples 1 X X X X o ○ o ○ o o o 2 o o o o o ○ o ○ ▵ o X 3 o o o o o o X o ▵ 4 o o ▵ X X X X X ▵ 5 ▵ X ▵ X ▵ ▵ X X X As described above, the present invention gives color images of high quality formed by dots of precisely circle shape with excellent color density without causing feathering, bleeding, and color nonuniformity even on plain paper. Furthermore, the present invention enables excellent recording without failure of ejection after intermission of printing with stability and without nozzle clogging.

Claims: An ink for ink-jet recording, comprising a dye, water, and the components (a), (b), and (c) below: (a) at least one surfactant selected from the group consisting of higher alcohol-ethylene oxide adducts represented by General Formula [1], alkylphenol-ethylene oxide adducts represented by General Formula [2], ethylene oxide-propylene oxide copolymers represented by General Formula [3], and acetylene glycol-ethylene oxide adducts represented by General Formula [4], at a content of from 0.1 to 20 % by weight; R-O-(CH 2 CH 2 O) n -H where R is alkyl, and n is an integer; where R is alkyl, and n is an integer; where R is alkyl or hydrogen, and n and ℓ are respectively an integer; where m and n are respectively an integer; (b) thiodiglycol, at a content of from 1 to 30 % by weight; and (c) urea or a derivative thereof, at a content of from 1 to 30 % by weight. An ink for ink-jet recording according to Claim 1, wherein the value of n or n+m in General Formulas [1] to [4] is from 4 to 20. An ink-jet recording method comprising the steps of: (i) selecting an ink comprising a dye, water, and the components (a), (b), and (c): (a) at least one surfactant selected from the group consisting of higher alcohol-ethylene oxide adducts represented by General Formula [1], alkylphenol-ethylene oxide adducts represented by General Formula [2], ethylene oxide-propylene oxide copolymers represented by General Formula [3], and acetylene glycol-ethylene oxide adducts represented by General Formula [4], at a content of from 0.1 to 20 % by weight; R-O-(CH 2 CH 2 O) n -H where R is alkyl, and n is an integer; where R is alkyl, and n is an integer; where R is alkyl or hydrogen, and n and ℓ are respectively an integer; where m and n are respectively an integer; (b) thiodiglycol; and (c) urea or an derivative thereof; and (ii) conducting recording on a recording medium with ink droplets of said ink. An ink-jet recording method according to Claim 3, wherein ink droplets are ejected by action of thermal energy applied to the ink. A color ink-jet recording method comprising the step of conducting recording by ejecting droplets of ink of two or mote colors onto adjacent or superposed positions on a recording medium, said ink comprises a dye, water and the components (a), (b), and (c): (a) at least one surfactant selected from the group consisting of higher alcohol-ethylene oxide adducts represented by General Formula [1], alkylphenol-ethylene oxide adducts represented by General Formula [2], ethylene oxide-propylene oxide copolymers represented by General Formula [3], and acetylene glycol-ethylene oxide adducts represented by General Formula [4], at a content of from 0.1 to 20 % by weight; R-O-(CH 2 CH 2 O) n -H where R is alkyl, and n is an integer; where R is alkyl, and n is an integer; where R is alkyl or hydrogen, and n and ℓ are respectively an integer; where m and n are respectively an integer; (b) thiodiglycol; and (c) urea or an derivative thereof. A color ink-jet recording method according to Claim 5, wherein ink droplets are ejected by action of thermal energy applied to the ink. An ink-jet recording method according to claim 3 or 5, wherein the recording medium has fiber exposed on the surface thereof. A recording unit having an ink container portion for holding ink, and a head portion for ejecting an ink as ink droplets, said ink is as defined in claim 1. A recording unit according to Claim 8, wherein the head portion comprises a head which ejects ink droplets by action of thermal energy applied to the ink. An ink cartridge comprising an ink container portion for holding ink, said ink is as defined in Claim 1. An ink cartridge according to Claim 10, wherein the ink container portion is in a bag-shape structure. An ink-jet recording apparatus, comprising the recording unit of Claim 8. An ink-jet recording apparatus, comprising the ink cartridge of Claim 10 and a recording head. Use of the ink according to Claim 1, in an ink-jet recording method. Use of the ink according to Claim 1, in a recording unit. Use of the ink according to Claim 1, in an ink cartridge. Use of the ink according to Claim 1, in an ink-jet recording apparatus.

Inventors: GOTOH FUMIHIRO, SATO SHINICHI, SUGIMOTO HITOSHI, TOCHIHARA SHINICHI, UETUKI MASAYA, GOTOH, FUMIHIRO, SATO, SHINICHI, SUGIMOTO, HITOSHI, TOCHIHARA, SHINICHI, UETUKI, MASAYA
Applicants: CANON KK, CANON KABUSHIKI KAISHA
Application year: 1993
Main classification: C09D11
IPC codes: C09D11