ink jet recording inks of the present invention comprise as a dispersant greater than or equal to two dispersants each having a different hlb . there have been suggested various methods to measure and calculate hlb , and the calculated hlbs slightly differ in accordance with the method of calculation . in the present invention , hlbs are represented by the following equation which was suggested by davies in 1957 : in the present invention , the number , n , of dispersants each having a different hlb which is defined by this formula is required to be 2 or more , and the number is preferably from 2 to 3 . given that respective hlbs of n ( n ≧ 2 ) kinds of dispersants are such that hlb 1 & lt ; hlb 2 & lt ; . . . & lt ; hlb n , it is preferable that at least two dispersants satisfy the following formula : namely , it is desired that the difference between at least two dispersants is from 1 to 30 , and more preferably from 2 to 25 , most preferably from 12 to 20 . in ink jet recording inks of the present invention , when the difference between at least two dispersants is less than 1 or more than 30 , problems such as variation in dot diameters , clogging in a nozzle and the like easily occur and the effect of use of dispersants is not fully manifested . for example , if the number of dispersants is 3 or more , it is most preferable that each difference between adjacent two hlbs is in the range from 1 to 30 when hlbs are arranged in descending order ( or in ascending order ). however , when the difference between hlbs of at least two dispersants is in the range from 1 to 30 , the differes between hlbs of the other pairs are not necessarily required to be in the range from 1 to 30 . in the present invention , given that respective hlbs of n ( n ≧ 2 ) kinds of dispersants are hlb 1 , hlb 2 , . . . , hlb n and respective weights are w 1 , w 2 , . . . , w n , the average hlb of the mixture of n kinds of dispersants is represented by the following formula . namely , the average hlb is defined by the weighted mean of hlbs of respective dispersants . ## equ1 ## ( wherein y is an integer from 1 to n ) in ink jet recording inks of the present invention , the average hlb of the mixture of dispersants is preferably from 10 to 40 , more preferably from 12 to 30 , further preferably from 18 to 22 . when the average hlb of the mixture of dispersants is less than 10 , hydrophobicity of the dispersants is too high and it is difficult to disperse the dispersants in an aqueous medium , therefore , problems such as variation in dot diameters , clogging in a nozzle and the like easily occur . when the average hlb of the mixture of dispersants is more than 40 , hydrophobicity of the dispersants is too low , adsorbability between the pigment and the dispersants is low , and dispersion stability of ink tends to lower . as the dispersant used in an ink jet recording ink of the present invention , a high - molecular dispersant is preferably used in addition to publicly - known surfactants . as the high - molecular dispersant , polymers having a hydrophilic portion and hydrophobic portion can be used . as the polymer having a hydrophilic portion and hydrophobic portion , condensation polymers and addition polymers can be used . examples of the condensation polymers include publicly - known polyester dispersants . examples of the addition polymers include addition polymers of a monomer having an α , β - ethylenic unsaturated group . desired high - molecular dispersants can be obtained by selecting a suitable combination of a monomer having an α , β - ethylenic unsaturated group which has a hydrophilic group and a monomer having an α , β - ethylenic unsaturated group which has a hydrophobic group , and by copolymerizing these monomers . also , homopolymers of a monomer having an α , β - ethylenic unsaturated group which has a hydrophilic group can be used as the high - molecular dispersant . examples of the monomer having an α , β - ethylenic unsaturated group which has a hydrophilic group include monomers having a carboxyl group , sulfonic group and the like , such as acrylic acid , methacrylic acid , crotonic acid , itaconic acid , mono ester of itaconic acid , maleic acid , mono ester of maleic acid , fumaric acid , mono ester of fumaric acid , vinyl sulfonic acid , styrene sulfonic acid , sulfonated vinylnaphthalene and the like . examples of the monomer having an α , β - ethylenic unsaturated group which has a hydrophobic group include styrene derivatives such as styrene , α - methylstyrene , vinyl toluene and the like , vinylnaphthalene , vinylnaphthalene derivatives , alkyl acrylates , alkyl methacrylates , alkyl crotonates , dialkyl itaconates , dialkyl maleates , and the like . examples of the preferable copolymer include styrene / styrenesulfonic acid copolymers , styrene / maleic acid copolymers , styrene / methacrylic acid copolymers , styrene / acrylic acid copolymers , vinylnaphthalene / maleic acid copolymers , vinylnaphthalene / methacrylic acid copolymers , vinylnaphthalene / acrylic acid copolymers , alkyl acrylate / acrylic acid copolymers , alkyl methacrylate / methacrylic acid copolymers , styrene / alkyl methacrylate / methacrylic acid terpolymers , styrene / alkyl acrylate / acrylic acid terpolymers , and the like . the number of carbon atoms in the above - mentioned alkyl ester is preferably from 1 to 6 . further , these polymers may be copolymerized with a monomer having a polyoxyethylene group or hydroxyl group , if necessary . the above - mentioned copolymer may be also copolymerized with a monomer having cationic functional group , for example , n , n - dimethylaminoethyl methacrylate , n , n - dimethylaminoethyl acrylate , n , n - dimethylamino methacrylamide , n , n - dimethylamino acrylamide , vinyl pyridine , vinyl pyrrolidone and the like , to enhance hydrophilicity with a pigment having an acidic functional group on the surface and to improve dispersion stability . the copolymer may be any of random , block and graft copolymer . also , polystyrenesulfonic acids , polyacrylic acids , polymethacrylic acids , polyvinylsulfonic acids , polyalginic acids , polyoxyethylene / plyoxypropylene block copolymers , condensation products of naphthalenesulfonic acid and formalin , cellulose derivatives such as carboxymethyl cellulose , carboxyethyl cellulose and the like , polysaccharides and derivatives thereof , polyvinylpyrrolidones , polyethyleneimines , polyamines , polyamides and the like can be used as the high - molecular dispersant . among these polymers , polymers containing acids as a hydrophilic group are preferably used in the form of salts with basic compounds to enhance water - solubility . examples of the compounds which form salts with the polymer containing acids as a hydrophilic group include alkaline metals such as sodium , potassium , lithium and the like , aliphatic amines such as monomethylamine , dimethyamine , triethylamine and the like , alcoholamines such as monomethanolamine , monoethanolamine , diethanolamine , triethanolamine , diisopropanolamine and the like , ammonia and the like . in the present invention , the combination of dispersants can be appropriately selected in consideration of hlbs of various dispersants , and the following combinations are preferably used . ( 1 ) combinations of the salt of a styrene / styrenesulfonic acid copolymer or a partially - sulfonated polystyrene , with at least one of the salt of a n - butyl methacrylate / methacrylic acid copolymer , the salt of a styrene / n - butyl methacrylate / methacrylic acid terpolymer , the salt of a styrene / methacrylic acid copolymer and the salt of a styrene / acrylic acid copolymer , ( 2 ) combinations of the salt of polystyrenesulfonic acid , with at least one of the salt of a n - butyl methacrylate / methacrylic acid copolymer , the salt of a styrene / n - butyl methacrylate / methacrylic acid terpolymer , the salt of a styrene / methacrylic acid copolymer and the salt of a styrene / acrylic acid copolymer , or combinations of the salt of polystyrenesulfonic acid , with both of a styrene / acrylic acid copolymer and the salt of a styrene / triethylene glycol methacrylate / styrenesulfonic acid terpolymer , ( 3 ) combinations of the salt of a n - butyl methacrylate / methacrylic acid copolymer , with at least one of the salt of a styrene / maleic acid copolymer , the salt of a styrene / methacrylic acid copolymer , the salt of a styrene / acrylic acid copolymer , the salt of a styrene / triethylene glycol methacrylate / methacrylic acid terpolymer , the salt of a styrene / ethoxytriethylene glycol methacrylate / methacrylic acid terpolymer and the salt of a styrene / ethoxytriethylene glycol methacrylate / styrenesulfonic acid terpolymer , ( 4 ) combinations of the salt of a styrene / n - butyl methacrylate / methacrylic acid terpolymer , with at least one of the salt of a styrene / maleic acid copolymer , the salt of a styrene / methacrylic acid copolymer and the salt of a styrene / acrylic acid copolymer , ( 5 ) combinations of the salt of the condensation product of naphthalene sulfonic acid and formalin , with at least one of the salt of a n - butyl methacrylate / methacrylic acid copolymer , the salt of a styrene / n - butyl methacrylate / methacrylic acid terpolymer and the salt of a styrene / methacrylic acid copolymer , or combinations of the salt of the condensation product of naphthalene sulfonic acid and formalin , with both of the salt of a styrene / methacrylic acid copolymer and polyoxyethylene / polyoxypropylene block copolymer , ( 6 ) combinations of the salt of a styrene / acrylic acid copolymer , with at least one of the salt of a styrene / triethylene glycol methacrylate / methacrylic acid terpolymer , the salt of a styrene / ethoxytriethylene glycol methacrylate / methacrylic acid terpolymer and the salt of a styrene / triethylene glycol methacrylate / styrenesulfonic acid terpolymer , or combinations of the salt of a styrene / acrylic acid copolymer , with both of the salt of a styrene / n - butyl methacrylate / methacrylic acid terpolymer and a polyoxyethylene / polyoxypropylene block copolymer , ( 7 ) combinations of the salt of a styrene / methacrylic acid copolymer , with at least one of the salt of a styrene / ethoxytriethylene glycol methacrylate / methacrylic acid terpolymer , the salt of a styrene / ethoxytriethylene glycol methacrylate / styrenesulfonic acid terpolymer , a polyoxyethylene / polyoxypropylene block copolymer , the salt of a n - butyl methacrylate / methacrylic acid block copolymer , the salt of a block terpolymer composed of n - butyl methacrylate and 2 - hydroxyethyl methacrylate / methacrylic acid copolymer and the salt of a n - butyl methacrylate / dimethylaminoethyl methacrylate / methacrylic acid terpolymer , or combinations of the salt of a styrene / methacrylic acid copolymer , with both of the salt of a n - butyl methacrylate / methacrylic acid copolymer and the salt of a styrene / ethoxytriethylene glycol methacrylate / methacrylic acid terpolymer , both of the salt of a n - butyl methacrylate / methacrylic acid copolymer and a styrene / ethoxytriethylene glycol methacrylate / styrenesulfonic acid terpolymer or both of the salt of a styrene / n - butyl methacrylate / methacrylic acid terpolymer and the salt of a n - butyl methacrylate / dimethylaminoethyl methacrylate / methacrylic acid terpolymer , ( 8 ) combinations of the salt of a styrene / 2 - hydroxyethyl methacrylate / methacrylic acid terpolymer , with the salt of a methyl methacrylate / dimethylaminoethyl methacrylate / methacrylic acid terpolymer . ( 9 ) combinations other than the above - mentioned combinations may be appropriately selected from the dispersants exemplified in ( 1 ) to ( 8 ) in consideration of hlb . ( 10 ) combinations of a known surfactant with the above - described high - molecular dispersant may also be used . there are known various methods for measuring the weight - average molecular weights of dispersants . in the present invention , the weight - average molecular weights of dispersants are measured by gpc ( gel permeation chromatography ). the weight - average molecular weights of the high molecular dispersants used in ink jet recording inks of the present invention are preferably from 1000 to 30000 , more preferably from 3000 to 15000 , and further preferably from 4500 to 10000 . when the weight - average molecular weights of the high molecular dispersants are less than 1000 , dispersion of a pigment is unstable and the pigment is likely to aggregate during storage for a long period of time . when the weight - average molecular weights of the high molecular dispersants are more than 30000 , the viscosity of ink tends to increase , and discharge of ink drops is liable to be unstable . in the present invention , a low - molecular dispersant can also be used in addition to a high - molecular dispersant , however , when a low - molecular dispersant is used , the surface tension of inks are liable to lower and qualities of the resulting images are apt to deteriorate . when a high - molecular dispersant is used , such deterioration of a surface tension of inks does not occur and excellent image quality is obtained . further , a high - molecular dispersant is believed to have steric stability , therefore , dispersion stability obtained by the use of a high - molecular dispersant is higher than that obtained by the use of a low - molecular dispersant . for these reasons , a high - molecular dispersant is preferably used in the present invention . various surfactants can be used as the additives for controlling the surface tensions of dispersants and an ink . examples of a surfactant include anionic surfactants , nonionic surfactants , cationic surfactants , ampholytic surfactants and the like , and the anionic surfactants and nonionic surfactants are preferably used . examples of a anionic surfactant include alkylbenzene sulfonates , alkylphenyl sulfonates , alkylnaphthalene sulfonates , salts of higher fatty acids , sulfate salts of higher fatty esters , sulfonates of higher fatty esters , sulfate salts and sulfonates of higher alcohol ethers , higher alkylsulfosuccinates and the like and , more particularly , include dodecylbenzene sulfonate , chelilbenzene sulfonate , isopropylnaphthalene sulfonate , monobutylphenylphenol monosulfonate , monobutylbiphenyl sulfonate , dibutylphenylphenol disulfonate and the like . examples of the nonionic surface acitive agent include polyoxyethylenenonylphenyl ethers , polyoxyethyleneoctylphenyl ethers , polyoxyethylenedodecylphenyl ethers , polyoxyethylenealkyl ethers , polyoxyethylene fatty esters , sorbitan fatty esters , polyoxyethylene sorbitan fatty esters , fatty acid alkylolamides , acetylene glycol , oxyethylene adduct of acetylene glycol , and the like . the amount of dispersants added is selected according to the kind of a coloring material used , particularly pigment . in general , the total amount of dispersants added is from 0 . 1 to 100 parts by weight , preferably from 1 to 50 parts by weight , more preferably from 3 to 20 parts by weight based on 100 parts by weight of the pigment . water used in ink jet recording inks of the present invention is preferably ion exchanged water , ultra pure water , distilled water or ultrafiltered water to prevent mixing of impurity . as the pigment used as a coloring material in ink jet recording inks of the present invention , any of inorganic pigment and organic pigment can be used . examples of a black pigment include , but are not limited to , carbon black pigments such as furnace black , lamp black , acetylene black , channel black and the like , and , more particularly , include raven 7000 , raven 5750 , raven 5250 , raven 5000 ultra -, raven 3500 , raven 2000 , raven 1500 , raven 1250 , raven 1200 , raven 1290 ultra -, raven 1170 , raven 1255 ( the above - mentioned compounds are manufactured by columbian carbon corp . ), regal 400 , regal 400r , regal 330 , regal 330r , regal 660 , regal 660r , mogul l , monarch 700 , monarch 800 , monarch 880 , monarch 900 , monarch 1000 , monarch 1100 , monarch 1300 , monarch 1400 ( the above - mentioned compounds are manufactured by cabot corp . ), color black fw1 , color black fw2 , color black fw2v , color black 18 , color black fw200 , color black s150 , color black s160 , color black s170 , printex 35 , printex u , printex v , printex 140u , printex 140v , special black 6 , special black 5 , special black 4a , special black 4 ( the above - mentioned compounds are manufactured by degussa corp . ), no . 25 , no . 33 , no . 40 , no . 47 , no . 52 , no . 900 , no . 2300 , mcf - 88 , ma600 , ma7 , ma8 , ma100 ( the above - mentioned compounds are manufactured by mitsubishi chemical corporation ), and the like . further , magnetic fine particles such as magnetite , ferrite or the like , titanium black and the like can also be used as the black pigment . examples of a cyan pigment include , but are not limited to , c . i . pigment blue - 1 , c . i . pigment blue - 2 , c . i . pigment blue - 3 , c . i . pigment blue - 15 , c . i . pigment blue - 15 : 1 , c . i . pigment blue - 15 : 3 , c . i . pigment blue - 15 : 34 , c . i . pigment blue - 16 , c . i . pigment blue - 22 , c . i . pigment blue - 60 and the like . examples of a magenta pigment include c . i . pigment red 5 , c . i . pigment red 7 , c . i . pigment red 12 , c . i . pigment red 48 , c . i . pigment red 48 : 1 , c . i . pigment red 57 , c . i . pigment red 112 , c . i . pigment red 122 , c . i . pigment red 123 , c . i . pigment red 146 , c . i . pigment red 168 , c . i . pigment red 184 , c . i . pigment red 202 and the like . examples of a yellow pigment include , but are not limited to , c . i . pigmentyellow - 1 , c . i . pigmentyellow - 2 , c . i . pigment yellow - 3 , c . i . pigment yellow - 12 , c . i . pigment yellow - 13 , c . i . pigment yellow - 14 , c . i . pigment yellow - 16 , c . i . pigment yellow - 17 , c . i . pigment yellow - 73 , c . i . pigment yellow - 74 , c . i . pigment yellow - 75 , c . i . pigment yellow - 83 , c . i . pigment yellow - 93 , c . i . pigment yellow - 95 , c . i . pigment yellow - 97 , c . i . pigmentyellow - 98 , c . i . pigmentyellow - 114 , c . i . pigment yellow - 128 , c . i . pigment yellow - 129 , c . i . pigment yellow - 151 , c . i . pigment yellow - 154 and the like . in addition to a black pigment and three primary colors pigments of cyan , magenta and yellow , specific color pigments such as red , green , blue , brown , white or the like , pigments having metallic gloss such as gold , silver or the like , colorless extender pigments , plastic pigments and the like may be used in the present invention . also , novel pigments may be used . further , these pigments may be subjected to surface treatment . examples of a surface treatment include , for example , treatment with alcohol , acid , base , a coupling agent such as silane compound or the like , polymer grafting treatment , plasma treatment and the like . it is preferable to remove organic and inorganic impurities from these pigments for the purpose of prevention of clogging , and kogation on a heater in thermal ink jet method . in particular , it is desired that the concentration of calcium , iron , silicon , magnesium , phosphorus , zinc and the like in ink is 5 ppm or less . such removal can be conducted by washing with water , ultra filtration method , ion exchange treatment , adsorption by activated charcoal or zeolite , and the like . in ink jet recording inks of the present invention , the pigment is used in the range from 1 to 20 %, preferably from 2 to 10 % based on the weight of the ink . the coloring material used in ink jet recording inks of the present invention includes dyes in addition to the pigments . the effect of the present invention is manifested particularly when ink jet recording inks contain a dye having low water - solubility . examples of the dye having low water - solubility include dyes in which the number of sulfonic groups contained in the dye molecule is 2 or less and the number of carboxyl groups is higher than the number of sulfonic groups and whose water - solubility is 10 % by weight or less at 20 ° c ., and the like . examples of the water - soluble organic solvent used in ink jet recording inks of the present invention include polyhydric alcohols such as ethylene glycol , diethylene glycol , propylene glycol , butylene glycol , triethylene glycol , 1 , 5 - pentanediol , 1 , 2 , 6 - hexanetriol , glycerin and the like , polyhydric alcohol derivatives such as ethylene glycol monomethyl ether , ethylene glycol monoethyl ether , ethylene glycol monobutyl ether , diethylene glycol monomethyl ether , diethylene glycol monoethyl ether , diethylene glycol monobutyl ether , propylene glycol monobutyl ether , dipropylene glycol monobutyl ether and the like , nitrogen - containing solvents such as pyrrolidone , n - methyl - 2 - pyrrolidone , cyclohexylpyrrolidone , triethanolamine and the like , alcohols such as ethanol , isopropyl alcohol , butyl alcohol , benzyl alcohol and the like , or sulfur - containing solvents such as thiodiethanol , thiodiglycerol , sulfolane , dimethylsulfoxide and the like , propylene carbonate , ethylene carbonate , and the like . these water - soluble organic solvents may be used alone or in combination . the water - soluble organic solvent is used in the range from 1 to 60 %, preferably from 5 to 40 % based on the weight of the ink . ink jet recording inks of the present invention can comprise polyethyleneimine , polyamines , polyvinylpyrrolidone , polyethylene glycol , cellulose derivatives such as ethyl cellulose , carboxymethyl cellulose and the like , polysaccharides and derivative thereof , water - soluble polymer , polymer emulsion such as acrylic emulsion , polyurethane emulsion and the like , cyclodextrin , macrocyclic amines , dendrimer , crowm ethers , urea and derivative thereof , acetamides , and the like in addition to the above - mentioned components , to control the characteristics of the ink . ink jet recording inks can optionally comprise a ph regulator , antioxidant , antifungal agent , viscosity regulator , electro conductive agent , ultraviolet absorbing agent , chelating agent , water - soluble dye , dispersed dye , oil - soluble dye and the like . examples of the ph regulator include , for example , potassium hydroxide , sodium hydroxide , lithium hydroxide , ammonium hydroxide , triethanolamine , diethanolamine , ethanolamine , 2 - amino - 2 - ethyl - 1 - propanol , ammonia and the like . further , publicly - known ph buffers can also be used as the ph regulator . the ph of the ink is preferably from 6 . 0 to 11 . 0 , more preferably from 7 . 5 to 9 . 0 . the surface tension of the ink is controlled to be within the range from 20 to 65 mn / m , preferably from 30 to 50 mn / m . the viscosity of the ink is controlled to be within the range from 1 . 0 to 10 . 0 mpa · s , preferably from 1 . 5 to 3 . 5 mpa · s . ink jet recording inks of the present invention can be prepared , for example , by adding a predetermined amount of a pigment to an aqueous solution containing a predetermined amount of dispersants , stirring completely the mixture , dispersing the mixture using a dispersing machine , removing coarse particles in the mixture by centrifugal separation and the like , adding a desired solvent , additive and the like to the disperse system , stirring the resulting mixture , and filtering the mixture . also , inks may be prepared by forming a thick disperse system comprising a pigment , and diluting the disperse system . further , inks may be prepared by mixing a desired solvent , water and dispersant , adding a pigment to the mixture , and dispersing the resultant mixture using a dispersing machine . any commercially available dispersing machine , for example , colloid mill , flowjet mill , slasher mill , high speed disperser , ball mill , attritor , sand mill , sand grinder , ultrafine mill , aigarmotor mill , dyno mill , pearl mill , agitator mill , cobol mill , three - roll , two - roll , extruder , kneader , microfluidizer , laboratory homogenizer , supersonic homogenizer and the like may be used for dispersion and these may be used alone or in combination . ink jet recording inks of the present invention can also be used for a recording apparatus equipped with a heater to aid in the fixing of ink to a paper sheet , and a recording apparatus equipped with a intermediate transfer mechanism having an intermediate in which apparatus an ink is applied to an intermidiate an the ink on the intermidiate is transferred onto a recording medium such as a paper sheet or the like , in addition to conventional ink jet recording apparatuses . the present invention will be illustrated more particularly in accordance with the following examples . ______________________________________ parts by weight______________________________________polystyrene / sodium styrenesulfonate polymer 0 . 5 ( weight - average molecular weight 10000 , sulfonation degree 95 %, hlb calculated value 40 . 9 ) n - butyl methacrylate / sodium methacrylate copolymer 2 ( weight - average molecular weight 7500 , n - butyl methacrylate / methacrylic acid = 50 / 50 mol , hlb calculated value 14 . 1 ) ultra pure water 70 ( hlb difference 26 . 8 , the average hlb of a mixture of dispersants = 19 . 5 ) ______________________________________ the above - described components were mixed , and dispersants were dissolved in water . while this solution was stirred , 10 parts by weight of carbon black ( raven 5250 , manufactured by columbian carbon corp .) was added to the solution , the mixture was stirred for 30 minutes , then , this mixture was dispersed by attritor ( media : 3 mm diameter sus beads ) for 2 hours , and the coarse particles in the mixture were removed by a centrifugal separator . the ph value of the mixture was controlled to be 9 . 0 by 1 n naoh to obtain a dispersed liquid . ______________________________________ parts by weight______________________________________dispersed liquid ( described above ) 45 diethylene glycol 7 glycerin 4 isopropyl alcohol 3 polyoxyethyleneoleyl ether ( oxyethylene = 30 mol ) 0 . 1 ultra pure water 40 . 9______________________________________ the above - mentioned components were mixed and stirred , and the mixture was filtrated by a membrane filter having a pore size of 1 μm , to obtain an ink . ______________________________________ parts by weight______________________________________polystyrene / sodium styrenesulfonate polymer 0 . 6 ( weight - average molecular weight 10000 , sulfonation degree 95 %, hlb calculated value 40 . 9 ) styrene / potassium methacrylate copolymer 1 . 8 ( weight - average molecular weight 5000 , styrene / methacrylic acid = 33 / 67 mol , hlb calculated value 19 . 9 ) carbon black 10 ( raven 5250 , manufactured by columbian carbon corp .) ultra pure water 70 ( hlb difference 21 . 0 , the average hlb of a mixture of dispersants = 25 . 2 ) ______________________________________ the above - described components were mixed in the same manner as in example 1 to obtain a dispersed liquid ( pigment concentration 11 . 0 %). ______________________________________ parts by weight______________________________________dispersed liquid ( described above ) 45 sulfolane 9 diethylene glycol 6 surfynol 104 0 . 03 ( manufactured by nisshin chemical industry corp .) ultra pure water 39 . 97______________________________________ the above - mentioned components were mixed and stirred , and the mixture was filtrated by a membrane filter having a pore size of 1 μm , to obtain an ink . ______________________________________ parts by weight______________________________________n - butyl methacrylate / sodium methacrylate copolymer 0 . 7 ( weight - average molecular weight 7500 , n - butyl methacrylate / methacrylic acid = 50 / 50 mol , hlb calculated value 14 . 1 ) styrene / sodium maleate copolymer 0 . 3 ( weight - average molecular weight 5000 , styrene / methacrylic acid = 50 / 50 mol , hlb calculated value 28 . 1 ) ultra pure water 70 ( hlb difference 14 . 0 , the average hlb of a mixture of dispersants = 18 . 3 ) ______________________________________ the above - described components were mixed , and dispersants were dissolved in water . while this solution was stirred , 10 parts by weight of carbon black ( regal 330 , manufactured by cabot corp .) was added to the solution , the mixture was stirred for 30 minutes , then , this mixture was dispersed by dynomill ( media : 0 . 5 mm diameter zirconia beads ) for 1 hour , and the coarse particles in the mixture were removed by a centrifugal separator , to obtain a dispersed liquid . an ink was prepared in the same manner as in example 1 except that the above - mentioned dispersed liquid was used in an amount of 45 parts by weight . ______________________________________ parts by weight______________________________________sodium polystyrenesulfonate 0 . 2 ( weight - average molecular weight 5500 , hlb calculated value 41 . 9 ) styrene / sodium styrenesulfonate / triethylene glycol 0 . 3 methacrylate terpolymer ( weight - average molecular weight 25000 , styrene / sodium styrenesulfonate / triethylene glycol methacrylate = 10 / 60 / 30 mol , hlb calculated value 2 . 9 . 7 ) styrene / sodium acrylate copolymer ( weight - average 0 . 5 molecular weight 3000 , styrene / acrylic acid = 67 / 33 mol , hlb calculated value 10 . 0 ) carbon black 10 ( regal 330 , manufactured by cabot corp .) ultra pure water 70 ( hlb difference 12 . 2 , 19 . 9 , the average hlb of a mixutre of dispersants = 22 . 3 ) ______________________________________ the above - described components were mixed in the same manner as in example 3 to obtain a dispersed liquid ( pigment concentration 11 . 1 %). ______________________________________ parts by weight______________________________________dispersed liquid ( described above ) 45 thiodiethanol 9 glycerin 4 isopropyl alcohol 3 urea 5 surfynol 465 0 . 05 ( manufactured by nisshin chemical industry corp .) ultra pure water 33 . 95______________________________________ the above - mentioned components were mixed and stirred , and the mixture was filtrated by a membrane filter having a pore size of 1 μm , to obtain an ink . ______________________________________ parts by weight______________________________________condensation product of naphthalene sulfonic acid and 0 . 3 formalin ( weight - average molecular weight 4500 , hlb calculated value 40 . 5 ) styrene / n - butyl / methacrylate / sodium methacrylate 0 . 9 terpolymer ( weight - average molecular weight 3000 , styrene / n - butyl methacrylate / methacrylic acid = 20 / 40 / 40 mol , hlb calculated value 12 . 2 ) ultra pure water 70 ( hlb difference 28 . 3 , the average hlb of a mixture of dispersants = 19 . 3 ) ______________________________________ the above - described components were mixed , and dispersants were dissolved in water . while this solution was stirred , 10 parts by weight of carbon black ( mogul l , manufactured by cabot corp .) was added to the solution , the mixture was stirred for 30 minutes , then , this mixture was dispersed by dynomill ( media : 0 . 5 mm diameter zirconia beads ) for 1 hour , and the coarse particles in the mixture were removed by a centrifugal separator , and the ph value of the mixture was controlled to be 9 . 0 by 1 n naoh to obtain a dispersed liquid ( pigment concentration 11 . 5 %). ______________________________________ parts by weight______________________________________dispersed liquid ( described above ) 45 thiodiethanol 8 2 - pyrrolidone 4 isopropyl alcohol 3 ultra pure water 40______________________________________ the above - mentioned components were mixed and stirred , and the mixture was filtrated by a membrane filter having a pore size of 1 μm , to obtain an ink . ______________________________________ parts by weight______________________________________styrene / sodium acrylate copolymer 0 . 9 ( weight - average molecular weight 3000 , styrene / acrylic acid = 75 / 25 mol , hlb calculated value 8 . 3 ) styrene / n - butyl methacrylate / sodium methacrylate 0 . 8 terpolymer ( weight - average molecular weight 5700 , styrene / n - butyl / methacrylate / methacrylic acid = 20 / 40 / 40 mol , hlb calculated value 12 . 2 ) polyoxyethylene / polyoxypropylene / polyoxyethylene 0 . 3 block copolymer ( weight - average molecular weight 3000 , oxypropylene = 30 mol , oxyethylene = 27 mol , hlb calculated value 14 . 7 ) ultra pure water 70 ( hlb difference 2 . 5 , 3 . 9 , the average hlb of a mixture of dispersants = 10 . 8 ) ______________________________________ the above - described components were mixed , and dispersants were dissolved in water . while this solution was stirred , 10 parts by weight of a copper phthalocyanine pigment ( c . i . pigment blue - 15 ) was added to the solution , the mixture was stirred for 30 minutes , then , this mixture was dispersed by dynomill ( media : 0 . 5 mm diameter zirconia beads ) for 1 hour , and the coarse particles in the mixture were removed by a centrifugal separator , to obtain a dispersed liquid . ______________________________________ parts by weight______________________________________dispersed liquid ( described above ) 40 diethylene glycol 10 butyl carbitol 5 ultra pure water 45______________________________________ the above - mentioned components were mixed and stirred , and the mixture was dispersed by a ultrasonic homogenizer for 30 minutes and the mixture was filtrated by a membrane filter having a pore size of 1 μm , to obtain an ink . ______________________________________ parts by weight______________________________________condensation product of naphthalene sulfonic acid and 0 . 4 formalin ( weight - average molecular weight 4500 , hlb calculated value 40 . 5 ) styrene / potassium methacrylate copolymer 1 . 2 ( weight - average molecular weight 5000 , styrene / methacrylic acid = 33 / 67 mol , hlb calculated value 19 . 9 ) polyoxyethylene / polyoxypropylene / polyoxyethylene 0 . 4 block copolymer ( weight - average molecular weight 1700 , oxypropylene = 19 mol , oxyethylene = 11 mol , hlb calculated value 10 . 8 ) ultra pure water 70 ( hlb difference 20 . 6 , 9 . 1 , the average hlb of a mixture of dispersants = 22 . 2 ) ______________________________________ the above - described components were mixed , and dispersants were dissolved in water . while this solution was stirred , 10 parts by weight of a quinacridone pigment ( c . i . pigment red - 122 ) was added to the solution , the mixture was stirred for 30 minutes , then , this mixture was dispersed by dynomill ( media : 0 . 5 mm diameter zirconia beads ) for 1 hour , and the coarse particles in the mixture were removed by a centrifugal separator , to obtain a dispersed liquid . an ink was prepared in the same manner as in example 6 except that the above - mentioned dispersed liquid was used in an amount of 40 parts by weight . an ink was prepared in the same manner as in example 7 except that bisazoyellow pigment ( c . i . pigment yellow - 83 ) was used in an amount of 10 parts by weight as a pigment . an ink was prepared in the same manner as in example 1 except that only a polystyrene / sodium styrenesulfonate polymer ( weight - average molecular weight 10000 , sulfonation degree 95 %, hlb calculated value 40 . 9 ) was used in an amount of 2 . 5 parts by weight as a dispersant . an ink was prepared in the same manner as in example 1 except that only a n - butyl methacrylate / sodium methacrylate copolymer ( weight - average molecular weight 7500 , n - butyl methacrylate / methacrylic acid = 50 / 50 mol , hlb calculated value 14 . 1 ) was used in an amount of 2 . 5 parts by weight as a dispersant . an ink was prepared in the same manner as in example 1 except that only a styrene / sodium methacrylate copolymer ( weight - average molecular weight 6000 , styrene / methacrylic acid = 25 / 75 mol , hlb calculated value 19 . 5 ) was used in an amount of 2 . 5 parts by weight as a dispersant . ______________________________________ parts by weight______________________________________n - butyl methacrylate / sodium methacrylate copolymer 1 . 0 ( weight - average molecular weight 7500 , n - butyl methacrylate / methacrylic acid = 50 / 50 , hlb calculated value 14 . 1 ) styrene / potassium methacrylate copolymer 1 . 5 ( weight - average molecular weight 5500 , styrene / methacrylic acid = 50 / 50 mol , hlb calculated value 14 . 1 ) carbon black ( regal 330 , manufactured by cabot corp .) 10 ultra pure water 70 ( hlb difference 0 , the average hlb of a mixture of dispersants = 14 . 1 ) ______________________________________ the above - described components were dispersed in the same manner as in example 3 to obtain a dispersed liquid . an ink was prepared in the same manner as in example 1 except that the above - mentioned dispersed liquid was used in an amount of 45 parts by weight . ______________________________________ parts by weight______________________________________sodium polystyrenesulfonate 0 . 5 ( weight - average molecular weight 5500 , hlb calculated value 41 . 9 ) styrene / sodium acrylate copolymer 0 . 5 ( weight - average molecular weight 3200 , styrene / acrylic acid = 67 / 33 mol , hlb calculated value 10 . 0 ) carbon black ( regal 330 , manufactured by cabot corp .) 10 ultra pure water 70 ( hlb difference 31 . 9 , the average hlb of a mixture of dispersants = 26 . 0 ) ______________________________________ the above - described components were dispersed in the same manner as in example 3 to obtain a dispersed liquid . an ink was prepared in the same manner as in example 4 except that the above - mentioned dispersed liquid was used in an amount of 45 parts by weight . ______________________________________ parts by weight______________________________________condensation product of naphthalene sulfonic acid and 0 . 4 formalin ( weight - average molecular weight 4500 , hlb calculated value 40 . 5 ) sodium polystyrenesulfonate 0 . 6 ( weight - average molecular weight 5500 , hlb calculated ( value 41 . 9 ) carbon black ( mogul l , manufactured by cabot corp .) 10 ultra pure water 70 ( hlb difference 1 . 4 , the average hlb of a mixture of dispersants = 41 . 9 ) ______________________________________ the above - described components were dispersed in the same manner as in example 5 to obtain a dispersed liquid . an ink was prepared in the same manner as in example 5 except that the above - mentioned dispersed liquid was used in an amount of 45 parts by weight . ______________________________________ parts by weight______________________________________styrene / sodium acrylate copolymer 1 . 3 ( weight - average molecular weight 3000 , styrene / acrylic acid = 75 / 25 mol , hlb calculated value 8 . 3 ) styrene / n - butyl methacrylate / sodium methacrylate 0 . 7 terpolymer ( weight - average molecular weight 5700 , styrene / n - butyl methacrylate / methacrylic acid = 20 / 40 / 40 mol , hlb calculated value 12 . 2 ) copper phthalocyanine pigment ( c . i . pigment blue - 15 ) 10 ultra pure water 70 ( hlb difference 3 . 9 , the average hlb of a mixture of dispersants = 9 . 7 ) ______________________________________ the above - described components were dispersed in the same manner as in example 6 to obtain a dispersed liquid . an ink was prepared in the same manner as in example 6 except that the above - mentioned dispersed liquid was used in an amount of 40 parts by weight . the surface tension of each ink was measured using wilhelmy type surface tension measuring apparatus in the atmosphere of 23 ° c . and 55 % rh . the viscosity of each ink was measured at a shearing speed of 1400 / s in the atmosphere of 23 ° c . and 55 % rh . the ph value of each ink was measured using a glass electrode in the atmosphere of 23 ° c . and 55 % rh . each ink ( 100 g ) was charged in a glass tube having a lid . the glass tube was sealed with the lid , and was allowed to stand for 4 hours in the atmosphere of 70 ° c . and for 4 hours in the atmosphere of - 20 ° c . this standing procedure at 70 ° c . and - 20 ° c . was repeated for 4 times . the ink in the glass tube was filtered by a 1 μm filter with the ink being subjected to pressure . the time required for the ink to pass through the filter was measured , and the dispersion stability of each ink was evaluated according to the following standard . ∘ . . . [( time for the ink which has been subjected to the above acceleration test to pass through the filter )/( time for the ink before the acceleration test to pass through the filter )× 100 - 100 ] is less than 10 %. δ . . . [( time for the ink which has been subjected to the above acceleration test to pass through the filter )/( time for the ink before the acceleration test to pass through the filter )× 100 - 100 ] is greater than or equal to 10 % and less than 20 %. x . . . [( time for the ink which has been subjected to the above acceleration test to pass through the filter )/( time for the ink before the acceleration test to pass through the filter )× 100 - 100 ] is greater than or equal to 20 %. printing was conducted on fx - l paper ( manufactured by fuji xerox co ., ltd .) and 4024 paper ( manufactured by xerox co ., ltd .) using a prototyped ink jet printer ( thermal ink jet method , 600 dpi ), and the resulting line images were evaluated according to the following standard . printing was conducted on fx - l paper ( manufactured by fuji xerox co ., ltd .) and 4024 paper ( manufactured by xerox co ., ltd .) using the prototyped machine used in ( 5 ), these recording media were allowed to stand for one day , then the image on each recording medium was rubbed with a cotton rod several times , and whether a stain around the image occurred was observed . printing was conducted on fx - l paper ( manufactured by fuji xerox co ., ltd .) by discharging ink successively from nozzles while applying 1 × 10 8 pulses per nozzle to the respective nozzles using the same printer as used in ( 5 ). the diameter of the resulting dot was measured , and variation in the dot diameter was evaluated according to the following standard . ⊚ . . . variation in dot diameter based on the initial dot diameter is less than 3 %. ∘ . . . variation in dot diameter based on the initial dot diameter is greater than or equal to 3 % and less than 5 %. δ . . . variation in dot diameter based on the initial dot diameter is greater than or equal to 5 % and less than 10 %. x . . . variation in dot diameter based on the initial dot diameter is greater than or equal to 10 %. the printer used in ( 5 ), whose nozzles were not covered with caps , was allowed to stand in an atmosphere of 23 ° c . and 55 % rh after discharging of the ink was stopped . then , an image was formed by using the printer , and it was judged whether this image was of sufficient quality . if the image was of sufficient quality , the printer was again allowed to stand in an atmosphere of 23 ° c . and 55 % rh after discharging of the ink was stopped . again , an image was printed and the quality thereof was judged . this process was repeated , each time increasing the length of time until the formation of an image , until an image of insufficient quality was obtained . the period of time corresponding to the formation of the unsatisfactory image was used for evaluation . clogging difficulty of the ink was evaluated according to the following standard . ∘ . . . greater than or equal to 60 seconds and less than 80 seconds δ . . . greater than or equal to 30 seconds and less than 60 seconds the printer used in ( 5 ), whose nozzles were not covered with caps , was allowed to stand for one week , and then the nozzle was sucked by a suction apparatus installed in the printer , and the number of suction operations and the number of nozzles which could not discharge an ink were measured . ∘ . . . all nozzles could discharge ink after one suction operation δ . . . all nozzles could discharge ink after two suction operations x . . . some nozzles could not discharge ink after two suction operations table 1__________________________________________________________________________ average hlb of ink surface ink image paper hlb a mixture of tension viscosity dispersion quality fixing kogation clogging clogging difference dispersants ( mn / m ) ( mpa · s ) ink ph stability test test test test test 1 test__________________________________________________________________________ 2ex . 1 26 . 8 19 . 5 46 2 . 5 8 . 9 ◯ ◯ ◯ ◯ ◯ ◯ ex . 2 21 . 0 25 . 2 44 2 . 3 8 . 8 ◯ ◯ ◯ ◯ ◯ ◯ ex . 3 14 . 0 18 . 3 45 1 . 9 9 . 7 ⊚ ◯ ◯ ⊚ ⊚ ◯ ex . 4 12 . 2 , 19 . 9 22 . 3 42 2 . 0 9 . 8 ⊚ ◯ ◯ ⊚ ⊚ ◯ ex . 5 28 . 3 19 . 3 50 1 . 8 8 . 8 ◯ ◯ ◯ ◯ ◯ ◯ ex . 6 2 . 5 , 3 . 9 10 . 8 36 2 . 6 8 . 2 ⊚ ◯ ◯ ◯ ◯ ◯ ex . 7 20 . 6 , 9 . 1 22 . 2 35 2 . 5 8 . 3 ◯ ◯ ◯ ◯ ◯ ◯ ex . 8 20 . 6 , 9 . 1 22 . 2 35 2 . 6 8 . 2 ◯ ◯ ◯ ◯ ◯ ◯ comp . -- 40 . 9 48 2 . 0 8 . 9 x ◯ x x δ δ ex . 1 comp . -- 14 . 1 46 2 . 7 8 . 8 δ ◯ ◯ x x δ ex . 2 comp . -- 19 . 5 45 2 . 8 8 . 8 δ ◯ ◯ δ x x ex . 3 comp . 0 14 . 1 46 2 . 1 9 . 5 δ ◯ ◯ x x x ex . 4 ex . 9 31 . 9 26 . 0 44 1 . 9 9 . 9 δ ◯ ◯ δ δ δ ex . 10 1 . 4 41 . 9 51 1 . 6 8 . 9 δ . largecirc le . δ δ δ δ ex . 11 3 . 9 9 . 7 35 2 . 4 8 . 3 ◯ ◯ ◯ δ δ δ__________________________________________________________________________ ex : example comp . ex . : comparative example as shown in table 1 , respective characteristics are cellent in examples 1 to 11 in which hlb difference is from 1 to 30 , and respective characteristics are particularly excellent in examples 1 to 8 in which hlb difference is from 5 to 25 . further , particularly remarkable effects in the dispersion stability test , the kogation test and the clogging test 1 are obtained in examples 3 and 4 in which hlb difference is from 12 to 20 and the average hlb of the dispersants is from 18 to 22 .