Patent Publication Number: US-2007103526-A1

Title: Recording liquid, liquid cartridge and liquid emitting apparatus and method technical field

Description:
TECHNICAL FIELD  
      This invention relates to a recording liquid, deposited on a support in the form of liquid droplets for performing recording thereon, and a liquid cartridge in which the recording liquid is accommodated. This invention also relates to liquid emitting methods and apparatus for emitting a liquid, accommodated in this liquid cartridge and pressurized by the pressure generated by a pressure generating device, onto a support via emitting port in the form of liquid droplets.  
      The present application contains subject matter related to Japanese Patent Application JP-2003-344970 filed in the Japanese Patent Office on Oct. 2, 2003, the entire contents of which being incorporated herein by reference.  
     BACKGROUND ART  
      As an apparatus for emitting the liquid, there has so far been known a printer apparatus of the ink jet system in which the ink is emitted via head chip onto a recording paper sheet, as a support, for recording an image or letters/characters thereon. The printer apparatus, employing this ink jet system, has merits that it is low in running costs and small-sized and lends itself to printing an image as a color image. In the printing apparatus of the ink jet system, inks of plural colors, exemplified by yellow, magenta, cyan and black, are supplied from ink cartridges, containing the inks of these various colors, into e.g. ink liquid chambers of a head chip.  
      With this printer apparatus, the inks supplied to for example the ink liquid chambers are pressurized by pressure generating devices, such as heating resistors, arranged in the ink liquid chambers, so as to be emitted via small-sized ink emitting ports, that is, so-called nozzles, provided in the head chip. Specifically, the inks in the ink chambers are heated by heating resistors, provided within the ink liquid chambers, to generate air bubbles in the inks on the heating resistors. The inks are emitted from the nozzles under the pressure generated in the ink liquid chambers by the air bubbles, with the so emitted inks being deposited on for example a recording paper sheet, as a support, for printing an image or letters/characters thereon.  
      For the ink used for the above-described printer apparatus of the ink jet system, a solution composed of a coloring agent, such as a variety of dyes or pigments, as dyestuff, dispersed in for example an organic solvent, is used. It is required of the ink that it is of high image quality such that it is not bled when deposited on for example a recording paper sheet, and that is not deteriorated in quality when stored for long, such that it has long shelf life. It is also required that its color is not changed by light, heat or moisture after deposition on a recording paper sheet, that is, it has high color-fastness, that the ink is emitted from a nozzle in keeping with the printing speed of the printer apparatus, and that the ink dries promptly following the printing, that is, it has quick drying properties. It is furthermore required that the ink does not stop up the nozzle during printing or on the occasion of re-start of printing following interruption of printing. A variety of proposals which satisfy these requests have so far been made in Japanese Laid-Open Patent Publications S59-93765, S60-243175, S56-149475, S56-163168, S56-5781, S63-139964, S53-61412 and S62-116676.  
      It has however long been felt to be difficult to develop the ink which lends itself to increasing the printing speed of the printer apparatus, that is, to shortening the time interval of consecutive ink emission from the nozzle. Specifically, the viscosity of the ink needs to be lowered with increase in the printing speed of the printer apparatus, however, if the viscosity of the ink is lowered in this way, there is raised a problem that ink emission from the nozzle is destabilized.  
      In printing with a printer apparatus, plain paper sheets, such as copy paper sheets, bond paper sheets or report paper sheets, are mainly used as recording paper sheets for suppressing the printing cost. In such case, there is a fear that problems may be raised such that the deposited ink is bled along the fiber of the plain paper sheet, or is delayed in drying depending on for example the type of the sizing agent contained in the plain paper sheets.  
      For solving such problems, it is proposed in Japanese Laid-Open Patent Publications S-56-57862 and S-55-29546 to set the pH of the ink to high alkalinity or to use larger quantities of surfactants.  
      However, in case a strongly alkaline ink is used, the ink applied to the plain paper sheet also becomes strongly alkaline, which means that objects that may come in touch with the ink may be altered in physical properties.  
      With the use of larger quantities of surfactants, there is a fear that severe bleeding may occur depending on the types of the plain paper sheet used. Moreover, in this case, the ink tends to be excessively receded from the nozzle opening surface towards the ink liquid chamber or to leak outward beyond the nozzle opening surface to render it difficult to control the degree of wetting of the nozzle by the ink or to emit the ink from the nozzle. In addition, the cloud point of the surfactant commonly used is approximately 60° C. However, this cloud point may be exceeded as a result of heating of a heating resistor in case of emitting the ink from the nozzle. If the ink is heated beyond the cloud point of the surfactant, the surfactant may be precipitated into the ink to alter its physical properties. In such case, printing to a high image quality cannot be achieved, or it becomes impossible to cope with the shortened ink emission time intervals.  
     DISCLOSURE OF THE INVENTION  
     Problems to be Solved by the Invention  
      It is an object of the present invention to provide a recording liquid superior in wetting properties for a support and susceptible only to limited foaming or bleeding, and which will assure printing to high image quality as the shortened emission interval is coped with. The present invention also contemplates to provide a liquid cartridge for accommodating the recording liquid and methods and apparatus capable of printing to high image quality using the recording liquid contained in this liquid cartridge.  
      According to the present invention, there is provided, for achieving the above object, a recording liquid deposited on a support as liquid droplets for performing recording thereon, wherein the recording liquid contains a dyestuff, a solvent for dispersing the dyestuff and a surfactant containing an organic compound represented by the chemical formula (1):  
                 
 
 where k+1=1˜10 and m+n=2˜30. 
 
      According to the present invention, there is also provided a liquid cartridge mounted to a liquid supplying device provided to a liquid emitting apparatus which is configured for emitting a recording liquid contained in a liquid vessel in the form of liquid droplets for depositing the so emitted liquid droplets on a support to effect the recording. The liquid cartridge operates as a supply source for the recording liquid for the liquid supplying device. The recording liquid contains a dyestuff, a solvent for dispersing the dyestuff and an organic compound represented by the chemical formula (1):  
                 
 
 where k+1=1˜10 and m+n=2˜30. 
 
      According to the present invention, there is also provided a liquid emitting apparatus comprising emitting means including a liquid chamber for storage of a recording liquid therein, a supply unit for supplying the recording liquid to the liquid chamber, at least one pressure generating device provided in the liquid chamber for pressurizing the recording liquid stored in the liquid chamber, and an emitting port for emitting the recording liquid, pressurized by the pressure generating devices, onto the major surface of a support, from the liquid chamber, in the form of liquid droplets, and a liquid cartridge connected to the emitting means and operating as a supply source of the recording liquid to the supply unit. The recording liquid contains a dyestuff, a solvent for dispersing the dyestuff and a surfactant containing an organic compound represented by the chemical formula (1):  
                 
 
 where k+1=1˜10 and m+n=2˜30. 
 
      According to the present invention, there is also provided a method for emitting a liquid by a liquid emitting apparatus comprising emitting means including a liquid chamber for storage of a recording liquid therein, a supply unit for supplying the recording liquid to the liquid chamber, at least one pressure generating device provided in the liquid chamber for pressurizing the recording liquid stored in the liquid chamber, and an emitting port for emitting the recording liquid, pressurized by the pressure generating device, onto the major surface of a support, from the liquid chamber, in the form of liquid droplets, and a liquid cartridge connected to the emitting means and operating as a supply source of the recording liquid to the supply unit. The method comprises employing, as the recording liquid, a liquid mixture composed of a dyestuff, a solvent for dispersing the dyestuff, and a surfactant containing an organic compound represented by the chemical formula 1:  
                 
 
 where k+1=1˜10 and m+n=2˜30. 
 
      According to the present invention, in which a surfactant containing at least an organic compound represented by the chemical formula (1) is contained in the recording liquid, it is possible to suppress the foaming of the recording liquid in the liquid chamber and to provide for optimum wettability of the recording liquid for the support. Thus, according to the present invention, in which the foaming of the recording liquid in the liquid chamber in the emitting means may be suppressed to provide for optimum wettability of the recording liquid for e.g. a port for emission, the recording liquid can be emitted satisfactorily from the emitting port. Moreover, according to the present invention, in which the cloud point of the surfactant containing at least an organic compound represented by the chemical formula (1) is approximately 80° C. which is higher than that of the conventional surfactant, it is possible to prevent the temperature of the recording liquid on the pressure generating device from exceeding the cloud point of the surfactant when the recording liquid is emitted via emission port.  
      That is, according to the present invention, in which a surfactant containing at least the organic compound represented by the chemical formula (1):  
                 
 
 where k+1=1˜10 and m+n=2˜30, 
 
 is contained in the recording liquid, the recording liquid in the liquid chamber is prevented from foaming, whilst the recording liquid may be of optimum wettability with respect to the support. Hence, when a recording paper sheet is used as a support, the recording liquid, deposited on the recording paper sheet, may be prohibited from becoming bled or blurred, thus achieving printing to high image quality. 
 
      According to the present invention, in which the cloud point of the surfactant contained in the recording liquid is higher than heretofore, there is no risk that, when the recording liquid is emitted from the emitting port, the temperature of the recording liquid on the pressure generating device readily exceeds the cloud point of the surfactant to deteriorate the properties of the recording liquid. Hence, with the present invention, it is possible to avoid the inconvenience that liquid droplets from the emitting port become unable to be emitted via emitting ports due to deteriorated characteristics of the recording liquid.  
      According to the present invention, in which excessive foaming of the recording liquid in the liquid chamber may be prohibited and wettability of the recording liquid for the emitting port may be optimized, the recording liquid may be optimally emitted in the state of liquid droplets from the emitting port.  
      According to the present invention, the recorded liquid is not excessively foamed in the recording chamber, even though the emission interval of the recording liquid via emitting port is shortened. In addition, the recording liquid may exhibit optimum wettability with respect to e.g. the emitting port. Hence, the recording liquid may be optimally supplied into the liquid chamber or the emitting port, such that the recording liquid may be emitted in keeping up with an increased printing speed.  
      Other objects and specified advantages of the present invention will become more apparent from reading the following explanation of preferred embodiments which will now be made with reference to the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a perspective view showing an ink jet printer apparatus embodying the present invention.  
       FIG. 2  is a perspective view showing an ink jet print head cartridge provided to the ink jet printer apparatus.  
       FIG. 3  is a cross-sectional view showing the ink jet print head cartridge.  
       FIGS. 4A and 4B  are schematic views illustrating an ink supply unit when an ink cartridge has been mounted to an ink jet print head cartridge,  FIG. 4A  showing the unit with a supply port closed and  FIG. 4B  showing the unit with the supply port opened.  
       FIG. 5  is a schematic view for illustrating the relationship between the ink cartridge and the head chip in the ink jet print head cartridge.  
       FIGS. 6A and 6B  are cross-sectional views showing a valving unit in a connecting unit of an ink cartridge, with  FIG. 6A  showing the unit with a valve closed and  FIG. 6B  showing the unit with the valve opened.  
       FIG. 7  is an exploded perspective view showing the chip head of the ink jet print head cartridge.  
       FIG. 8  is a plan view showing the head chip.  
       FIG. 9 , illustrating the state of the head chip emitting an ink droplet, is a cross-sectional view for showing the state in which ink air bubbles of approximately the same size have been formed in an ink liquid chamber.  
       FIG. 10 , illustrating the state of the head chip emitting an ink droplet, is a cross-sectional view for showing the state in which an ink liquid droplet has been emitted vertically downward from the nozzle by two ink air bubbles.  
       FIG. 11 , illustrating the state of the head chip emitting an ink liquid droplet, is a cross-sectional view for showing the state in which ink air bubbles of differing sizes have been formed in the ink liquid chamber.  
       FIG. 12 , illustrating the state of the head chip emitting an ink droplet, is a cross-sectional view for showing the state in which an ink liquid droplet has been emitted in a substantially oblique direction from the nozzle by two ink air bubbles.  
       FIG. 13  is a side view of an ink jet printer apparatus, with a portion thereof being shown in a see-through fashion.  
       FIG. 14  is a schematic block diagram showing a control circuit of the ink jet printer apparatus.  
       FIG. 15  is a schematic block diagram showing an emission control unit of a control circuit.  
       FIGS. 16A  to  16 C are cross-sectional views showing the state of the emission control unit controlling the emitting direction of the ink liquid droplets, with  FIG. 16A  schematically showing the state of emission of an ink liquid droplet in a directly downward direction,  FIG. 16B  schematically showing the state of emission of ink liquid droplets in one of oblique directions, along the width of the recording paper sheet, with the nozzle as center, and  FIG. 16C  schematically showing the state of emission of ink liquid droplets in the other oblique direction along the width of the recording paper sheet, with the nozzle as center.  
       FIG. 17  is a flowchart for illustrating the printing operation of the ink jet printer apparatus.  
       FIG. 18  is a side view showing the state in which a head cap opening/closing unit in the ink jet printer apparatus has been opened, with a portion thereof being shown in a see-through fashion.  
       FIGS. 19A  to  19 C are plan views showing other instances of the head chip, with  FIG. 19A  showing the state in which heating resistors are arranged side-by-side along the running direction of the recording paper sheet,  FIG. 19B  showing the state in which three heating resistors are provided in an ink chamber and  FIG. 19C  showing the state in which four heating resistors are provided in an ink chamber.  
       FIG. 20  is a plan view showing yet another instance of the head chip wherein there is provided one heating resistor. 
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION  
      The recording liquid, liquid cartridge and the liquid emitting apparatus and methods, embodying the present invention, will now be explained with reference to the drawings.  
      An ink jet printer apparatus of the present embodiment, shown in  FIG. 1 , referred to below simply as a printer apparatus, prints images or letters/characters by emitting for example the ink onto a recording paper sheet P running in a predetermined direction. This printer apparatus  1  is a so-called line printer apparatus in which a plural number of ink emitting ports (nozzles) are arranged side-by-side along the width of the recording paper sheet P, that is, in the direction indicated by arrow W in  FIG. 1 , in keeping with the printing width of the recording paper sheet P.  
      Referring to  FIGS. 2 and 3 , this printer apparatus  1  includes an ink jet print head cartridge  3 , for emitting an ink  2 , referred to below simply as a head cartridge, and a printer main  4  on which to mount the head cartridge  3 . With the printer apparatus  1 , the head cartridge  3  is detachably mounted to the printer main  4 , and furthermore, ink cartridges  11   y,    11   m,    11   c  and  11   k,  as liquid cartridges for accommodating the ink  2  therein, operating as ink supply sources, are detachably mounted to the printer main  4 . With the printer apparatus  1 , the ink cartridge  11   y,  enclosing therein a yellow ink, the ink cartridge  11   m,  enclosing therein a magenta ink, the ink cartridge  11   c,  enclosing therein a cyan ink, and the ink cartridge  11   k,  enclosing therein a black ink, may be used. The head cartridge  3 , detachably mounted to the printer main  4 , and the ink cartridges  11   y,    11   m,    11   c  an  11   k,  detachably mounted to the head cartridge  3 , are consumable supplies and may be exchanged by spare items.  
      With the printer apparatus  1 , the recording paper sheet P, accommodated in a tray  55   a,  may be supplied into the inside of the printer main  4 , by mounting the tray  55   a  in a tray mounting section  5  provided on a front side bottom of the printer main  4 . The tray has housed therein a stack of the recording paper sheets P. When the tray  55   a  is mounted in the tray mounting section  5 , provided in the front side of the printer main  4 , the recording paper sheet P is fed by a paper sheet feed/discharge unit  54  from a paper feed port  55  to the back side surface of the printer main  4 . The recording paper sheet P, fed to the back side surface of the printer main  4 , has its running direction reversed by a reversing roll  83 , and is fed from the back side towards the front side of the printer main  4  on a path above a forward or on-going path. On the recording paper sheet P, fed from the back side towards the front side of the printer main  4 , printing data corresponding to letter/character data or image data, supplied from an information processing system  69 , such as personal computer, are printed as letters/characters or images, before the recording paper sheet P, sent from the back side to the front side of the printer main  4 , is discharged from a paper sheet discharge port  56 , provided in the front side of the printer main  4 .  
      The ink  2 , which proves the recording liquid on printing, is a liquid mixture composed of a coloring agent, a solvent for dispersing this coloring agent and a surfactant containing an organic compound shown by the following chemical formula 1:  
                 
 
 where k+1 is 1˜10 and m+n is 2˜30. 
 
 It is noted that the coloring agent may be exemplified by water-soluble dyes, which prove dyestuffs, and by a variety of pigments. 
 
      As the coloring agents, water-soluble dyes, exemplified by direct dyes, acidic dyes, basic dyes or reactive dyes, shown below, may be used. Specifically, C.I. Direct Yellow 1, 8, 11, 12, 24, 26, 27, 28, 33, 39, 44, 50, 58, 85, 86, 87, 88, 89, 98, 100 or 110, may, for example, be used as yellow-based direct dyes. These dyes may be used either alone or in combination. As magenta-based direct dyes, C.I. Direct Red 1, 2, 4, 9, 11, 13, 17, 20, 23, 24, 28, 31, 33, 37, 39, 44, 46, 62, 63, 75, 79, 80, 81, 83, 84, 89, 95, 99, 113, 197, 201, 218, 220, 224, 225, 226, 227, 228, 229, 230 and 321, for example, may be used. These dyes may be used either alone or in combination.  
      As cyan-based direct dyes, C.I. Direct Blue 1, 2, 6, 8, 15, 22, 25, 41, 71, 76, 77, 78, 80, 86, 90, 98, 106, 108, 120, 158, 160, 163, 165, 168, 192, 193, 194, 195, 196, 199, 200, 201, 202, 203, 207, 225, 226, 236, 237, 246, 248 or 249, for example, may be used. These dyes may be used either alone or in combination. As black-based direct dyes, C.I. Direct Black 17, 19, 22, 32, 38, 51, 56, 62, 71, 74, 75, 77, 94, 105, 106, 107, 108, 112, 113, 117, 118, 132, 133 or 146, may, for example, be used. These dyes may be used either alone or in combination.  
      As yellow-based acidic dyes, C.I. Acid Yellow 1, 3, 7, 11, 17, 19, 23, 25, 29, 36, 38, 40, 42, 44, 49, 59, 61, 70, 72, 75, 76, 78, 79, 98, 99, 110, 111, 112, 114, 116, 118, 119, 127, 128, 131, 135, 141, 142, 161, 162, 163, 164 or 165, may, for example, be used. These dyes may be used either alone or in combination. As magenta-based acidic dyes, C.I. Acid Red 1, 6, 8, 9, 13, 14, 18, 26, 27, 32, 35, 37, 42, 51, 52, 57, 75, 77, 80, 82, 83, 85, 87, 88, 89, 92, 94, 97, 106, 111, 114, 115, 117, 118, 119, 129, 130, 131, 133, 134, 138, 143, 145, 154, 155, 158, 168, 180, 183, 184, 186, 194, 198, 199, 209, 211, 215, 216, 217, 219, 249, 252, 254, 256, 257, 262, 265, 266, 274, 276, 282, 283, 303, 317, 318, 320, 321 or 322, for example, may be used, either alone or in combination.  
      As cyan-based acidic dyes, C.I. Acid Blue 1, 7, 9, 15, 22, 23, 25, 27, 29, 40, 41, 43, 45, 54, 59, 60, 62, 72, 74, 78, 80, 82, 83, 90, 92, 93, 100, 102, 103, 104, 112, 113, 117, 120, 126, 127, 129, 130, 131, 138, 140, 142, 143, 151, 154, 158, 161, 166, 167, 168, 170, 175, 182, 183, 184, 187, 192, 199, 203, 204, 205, 229, 234 or 236, may, for example, be used, either alone or in combination. As black-based acidic dyes, C.I. Acid Black 1, 2, 7, 24, 26, 29, 31, 44, 48, 50, 51, 52, 58, 60, 62, 64, 67, 72, 76, 77, 94, 107, 108, 109, 110, 112, 115, 118, 119, 121, 122, 131, 132, 139, 140, 155, 156, 157, 158, 159 or 191, may, for example, be used, either alone or in combination.  
      As yellow-based basic dyes, C.I. Basic Black 2.8, C.I. Basic Yellow 1, 2, 11, 12, 14, 21, 32 or 36, or C.I. Basic Orange 2, 15, 21 or 22 may, for example, be used, either alone or in combination.  
      As magenta-based basic dyes, C.I. Basic Red 1, 2, 9, 12, 13 or 37, or C.I. Basic Violet 1, 3, 7, 10 or 14, may, for example, be used, either alone or in combination. As cyan-based basic dyes, C.I. Basic Blue 1, 3, 5, 7, 9, 24, 25, 26, 28 or 29 or C.I. Basic Green 1 or 4 may, for example, be used, either alone or in combination.  
      As yellow-based reactive dyes, C.I. Reactive Yellow 1, 2, 3, 13, 14, 15 or 17, or C.I. Reactive Orange 2, 5, 7, 16, 20 or 24 may, for example, be used, either alone or in combination.  
      As magenta-based reactive dyes, C.I. Reactive Red 6, 7, 11, 12, 13, 14, 15, 17, 21, 23, 24, 35, 36, 42, 63, 66 or 84 may, for example, be used, either alone or in combination.  
      As cyan-based reactive dyes, C.I. Reactive Blue 2, 5, 7, 12, 13, 14, 15, 17, 18, 19, 20, 21, 25, 27, 28, 37, 38, 40 or 41, or C.I. Reactive Green 5 or 7 may, for example, be used, either alone or in combination.  
      As a solvent used for dispersing the dyes, shown above, such solvent which satisfies characteristics, for example, low viscosity, ease of handling, low cost or odorlessness, such as water, is used. As a solvent for the ink  2 , ion-exchanged water, for example, may be used for prohibiting unneeded ions from mixing into the ink  2 .  
      In addition to the solvents, such as water or ion-exchanged water, water-soluble organic solvents, such as aliphatic monohydric alcohols, aliphatic polyhydric alcohols or derivatives of the aliphatic polyhydric alcohols, may be contained, in addition to a solvent, such as water or ion-exchanged water, in the ink  2  as solvents.  
      The aliphatic monohydric alcohols may be enumerated by, for example, lower alcohols, such as methyl alcohol, ethyl alcohol, n-propyl alcohol, i-propyl alcohol, n-butyl alcohol, s-butyl alcohol or t-butyl alcohol, these being used either alone or in combination. With the use of the above-mentioned aliphatic monohydric alcohols, as solvent, surface tension of the ink  2  may be optimized, such that it is possible to obtain the ink  2  superior in penetrability to the recording paper sheet P, dot-forming properties or in the drying performance of the printed image.  
      In this case, with the use of, for example, ethyl alcohol, i-propyl alcohol or n-butyl alcohol, among the aforementioned aliphatic monohydric alcohols, as the solvent for the solvent of the ink  2 , it is possible to produce the ink  2  superior in the above-mentioned properties or performance.  
      The aliphatic polyhydric alcohols may be enumerated by, for example, alkylene glycols, such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butylenes glycol or glycerol, polyalkylene glycols, such as polyethylene glycol or polypropylene glycol, and thioglycol. These may be used either alone or in combination.  
      The derivatives of the aliphatic polyhydric alcohols may be enumerated by, for example, lower alkyl ethers of the aforementioned aliphatic polyhydric alcohols, such as ethylene glycol dimethylether, and lower carboxylates of the aforementioned aliphatic polyhydric alcohols, such as ethylene glycol diacetate. When the aforementioned aliphatic polyhydric alcohols and derivatives thereof are used as solvent for the ink  2 , the ink  2  may be less susceptible to drying, while its freezing point may be lowered, so that it becomes possible to suppress deterioration in physical properties on prolonged storage of the ink  2  and to suppress the nozzle  44   a  from being stopped up with the dried ink  2 .  
      Thus, with the use of one or a mixture of aliphatic monohydric alcohols, aliphatic polyhydric alcohols and derivatives of the aliphatic polyhydric alcohols, having respective inherent properties, in addition to water, for example, as a solvent, it is possible to obtain the ink  2  suited for an aim or application in view.  
      The ink  2  may also be added with amides, such as dimethyl formamide or diethyl acetoamide, ketones, such as acetone or diacetone alcohol, keto-alcohols, trihydric alcohols, such as tetrahydrofuran, dioxane, γ-butyl lactone, glycerin or 1,2,6-hexane triols, or with nitrogen-containing heterocyclic compounds, such as diethanolamine, triethanolamine, sulforan, 2-pyrrolidone, N-methyl-2-pyrrolidone, or 1,3-dimethyl-2-imidazolidinone, in addition to the aliphatic monohydric alcohols, aliphatic polyhydric alcohols and derivatives of the aliphatic polyhydric alcohols. This improves the aforementioned various characteristics of the ink  2 .  
      In addition to the above-described dyes and solvents, a surfactant containing at least the organic compound represented by the following chemical formula (1):  
                 
 
 where k+1=1˜10 and m+n=2˜30, 
 
 is also contained in the ink  2 . 
 
      Moreover, in addition to the surfactant containing at least the organic compound represented by the chemical formula (1), a surfactant having an organic compound represented by the following chemical formula (2)  
                 
 
 where o+p is an integer not less than 2, 
 
 may also be contained in the ink  2 . 
 
      Moreover, in addition to the surfactant containing an organic compound represented by the chemical formula 1, a surfactant obtained on mixing polyoxyethylene acetyleneglycols to at least one of ethers, such as polxyethylene alkylether or polyoxyethylene alkylphenyl ether, esters, such as polyoxyethylene fatty acid esters, polyoxyethylene polyoxypropylene copolymers, or nitrogen-containing compounds, such as polyoxyethylene alkylamine ether or fatty acid diethanol amide, may be contained in the ink  2 .  
      Since the ink  2 , obtained on mixing the above-described components, contains a surfactant containing at least the organic compound represented by the chemical formula 1, it is possible to suppress foaming and to optimize wetting performance with respect to the recording paper sheet P. That is, the ink may be quickly penetrated into the recording paper sheet P in a direction along its thickness so that it assumes a state as if it has been dried in situ. Hence, the printed image or the letter/character data, obtained on depositing the ink  2  on the recording paper sheet P, is of high quality, being free of bleeding or blurring.  
      Moreover, with the ink  2 , since the cloud point of the surfactant, containing an organic compound represented by the chemical formula 1, is as high as about 80° C., there is no risk that the cloud point of the surfactant contained in the ink is exceeded when the ink containing the surfactant is emitted as liquid droplet, as was the case with the conventional system. Hence, the ink may be deposited on the recording paper sheet P as liquid droplets in the state of stabilized physical properties.  
      The content in the ink  2  of the surfactant containing the organic compound represented by the chemical formula 1 is not less than 0.05 wt % and not larger than 10 wt %, preferably not less than 1 wt % and not larger than 5 wt %, based on the total weight of the ink  2 . If the content of the surfactant containing the organic compound, shown by the chemical formula 1, is lesser than 0.05 wt %, the wetting performance of the ink for the recorded paper sheet tends to be lowered.  
      On the other hand, if the content in the total quantity of the ink  2  of the surfactant containing the organic compound represented by the chemical formula 1 is larger than 10 wt %, there is presented an inconvenience that the ink  2  is liable to foaming. It is therefore crucial, for obtaining the ink  2  less susceptible to foaming, and for assuring proper seeping of the ink into the bulk of the recording paper sheet P, that the content in the total quantity of the ink  2  of the surfactant containing the organic compound of the chemical formula 1 shall be not less than 0.05 wt % and not larger than 10 wt %.  
      It is also possible for the ink  2  to contain for example a viscosity adjustment agent, a surface tension adjustment agent, a pH adjustment agent, antiseptics, a rust-proofing agent or a mold-proofing agent, in addition to the aforementioned dyes, solvents and surfactants. Specifically, the viscosity adjustment agent, surface tension adjustment agent and the pH adjustment agent may be exemplified by proteins, such as gelatin or casein, natural rubber, such as gum Arabic, cellulose derivatives, such as methyl cellulose, carboxymethyl cellulose or hydroxymethyl cellulose, lignin sulfonate, natural high polymeric materials, such as schellac, polyacrylates, salts of a styrene-acrylic acid copolymer, polyvinyl alcohol or polyvinyl pyrrolidone. The ink  2  may be added with one or more of these agents.  
      The antiseptics, rust-proofing agent and the mold-proofing agent may be enumerated by, for example, benzoic acid, dichlorophene, hexachlorophene, sorbic acid, p-hydroxy benzoate and ethylene diamine tetraacetate (EDTA). The ink may be added with one or more of these agents.  
      The ink  2  of the above-described configuration may be prepared as follows: In preparing the ink  2  of the solution system, employing for example a dye as a coloring agent, the coloring agent, composed of the above-described dye, the solvent and the surfactant are mixed together, and the resulting mixture is agitated and dispersed with for example a screw stirrer, as the mixture is heated to 40° C. to 80° C, to prepare the ink  2 . The ink  2  of the dispersion system, employing a pigment as the coloring agent, as an example, may be prepared by a pigment comminuting method, which has so far been known and used. This pigment comminuting method consists in dispersing the pigment and the surfactant in a solvent, using a dispersion device. such as a ball mill, a sand mill, an attriter, a roll mill, an agitator, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a pearl mill or a wet jet mill, to prepare the ink. The ink, prepared in this manner, is passed through for example a filter for filtration for removing contaminants or coarse-sized particles.  
      The so prepared ink  2  is accommodated in the ink cartridge  11 , such that the yellow-tinted ink, magenta-tinted ink, cyan-tinted ink and the black-tinted ink are accommodated in the ink cartridges  11   y,    11   m,    11   c  and  11   k,  respectively, as shown in  FIGS. 2 and 3 .  
      The head cartridge  3 , detachably mounted to the printer main  2 , forming the above-described printer apparatus  1 , and the ink cartridges  11   y,    11   m,    11   c  and  11   k,  detachably mounted to the head cartridge  3 , will now be explained with reference to the drawings.  
      The head cartridge  3 , performing the printing on the recording paper sheet P, is loaded from the upper surface of the printer main  4 , that is, from the direction indicated by arrow A in  FIG. 1 , and emits the ink  2  onto the recording paper sheet P, traveling by a paper sheet feed/discharge unit  54 , by way of effecting the printing.  
      The head cartridge  3  pressurizes the ink  2 , by the pressure generated by a pressure generating means of, for example, the electro-thermal or electro-mechanical system, for finely dividing the ink  2  into fine particles, which are then emitted and sprayed in the form of liquid droplets on the major surface of a support, such as recording paper sheet P. Specifically, the head cartridge  3  includes a cartridge main  21 , on which cartridge main  21  are mounted the ink cartridges  11   y,    11   m,    11   c  and  11   k,  which are containers charged with the inks  2  of respective colors. Meanwhile, the ink cartridges  11   y,    11   m,    11   c  and  11   k  are sometimes referred to below simply as ink cartridge or cartridges  11 .  
      Each ink cartridge  11 , detachably mounted to the head cartridge  3 , includes a cartridge vessel  12 , molded by injection molding a synthetic resin material, such as polypropylene, exhibiting high strength and resistance against ink. The cartridge vessel  12  is formed to a substantially rectangular shape, with the length of a longitudinal side thereof approximately equal to the width-wise size of the recording paper sheet P used, such as to provide for the largest possible capacity of the ink to be stored in its inside.  
      Specifically, the cartridge vessel  12 , forming the ink cartridges  11 , is provided with an ink container  13 , holding the ink  2 , an ink supply unit  14  for supplying the ink  2  from the ink container  13  into the inside of the cartridge main  21  of the head cartridge  3 , and an opening for communication with outside  15  for air intake from outside into the inside of the ink container  13 . The cartridge vessel also includes an air inlet duct  16  for introducing air taken in via opening  15  into the inside of the ink container  13 , and a reservoir  17  for transient storage of the ink  2  between the opening  15  and the air inlet duct  16 . The cartridge vessel  12  is also provided with a plural number of retention lugs  18  and a plural number of engagement steps  19  for retaining the ink cartridge  11  to the cartridge main  21 .  
      The ink container  13  is formed of a material exhibiting high air-tightness and delimits a space within which to accommodate the ink  2 . The ink container  13  is formed to approximately a rectangular shape having a longitudinal size approximately equal to the size along the width-wise direction W of the recording paper sheet P shown in  FIG. 3 .  
      The ink supply unit  14  is provided at a mid lower portion of the ink container  13 . This ink supply unit  14  is a protuberantly-shaped nozzle communicating with and intruding into the ink container  13 . The distal end of the nozzle is fitted in a connecting unit  26  of the head cartridge  3 , as later explained, to connect the cartridge vessel  12  of the head cartridge  3  to the cartridge main  21  of the head cartridge  3 .  
      Referring to  FIGS. 4A and 4B , the ink supply unit  14  is provided with a supply port  14   b  for supplying the ink  2  onto the bottom surface  14   a  of the ink cartridges  11 . This bottom surface  14   a  is provided with a valve  14   c  for opening/closing a supply port  14   b,  a coil spring  14   d  for biasing the valve  14   c  in a direction of closing the supply port  14   b,  and an opening/closing pin  14   e  for opening/closing the valve  14   c.    
      The supply port  14   b,  connected to the connecting unit  26  of the head cartridge  3 , for supplying the ink  2 , is closed, in a stage prior to loading of the ink cartridge  11  on the cartridge main  21  of the head cartridge  3 , by the valve  14   c  being biased in a direction of closing the supply port  14   b,  under the biasing force of the coil spring  14   d,  as a biasing member, as shown in  FIG. 4A .  
      When the ink cartridges  11  is loaded on the cartridge main  21 , the opening/closing pin  14   e  is uplifted in an opposite direction to the biasing direction of the coil spring  14   d,  by an upper part of the connecting unit  26  of the cartridge main  21 , constituting the head cartridge  3 , as shown in  FIG. 4B . The so uplifted opening/closing pin  14   e  uplifts the valve  14   c,  against the bias of the coil spring  14   d,  to open the supply port  14   b.    
      In this manner, the ink supply unit  14  of the ink cartridges  11  is connected to the connecting unit  26  of the head cartridge  3  to establish communication between the ink container  13  and an ink reservoir  31  to enable the ink  2  to be supplied to the ink reservoir  31 .  
      When the ink cartridges  11  is extracted from the connecting unit  26  of the head cartridge  3 , that is, when the ink cartridges  11  is dismounted from the mounting unit  22  of the head cartridge  3 , the uplifting of the valve  14   c  by the opening/closing pin  14   e  is released, with the valve  14   c  being moved in the biasing direction of the coil spring  14   d  to close the supply port  14   b.  This prohibits the ink  2  in the ink container  13  from leaking even when the ink cartridges  11  is about to be loaded on the cartridge main  21  with the distal end of the ink supply unit  14  facing downwards. When the ink cartridge  11  is extracted from the cartridge main  21 , the supply port  14   b  is closed quickly by the valve  14   c,  thereby prohibiting the ink  2  from leaking from the distal end of the ink supply unit  14 .  
      Referring to  FIG. 3 , the opening for communication with outside  15  is an air communication opening for air intake from outside the ink cartridge  11  into the ink container  13 . The opening  15  is provided in the upper surface, herein at a mid portion of the upper surface, of the cartridge vessel  12 , where the opening faces outwards in order to take in air even when the ink cartridge is mounted on the mounting unit  22  of the head cartridge  3 . That is, the opening  15  faces outwards so that, when the ink cartridge is mounted on the mounting unit  22 , the opening  15  faces outwards in order to take in air from outside. The opening  15  takes in air in an amount corresponding to the decreased quantity of the ink  2  in the ink container  13  when the ink cartridge  11  is mounted to the cartridge main  21  and the ink  2  has flown down from the ink container  13  towards the cartridge main  21 .  
      The air inlet duct  16  provides for communication between the ink container  13  and the opening  15  to introduce air taken in from the opening  15  into the ink container  13 . Hence, when the ink cartridge  11  is mounted on the cartridge main  21  and the ink  2  is supplied into the inside of the cartridge main  21  of the head cartridge  3 , with the quantity of the ink  2  in the ink container  13  then being decreased to lower the pressure inside the ink container, the inner pressure in the ink container  13  may be maintained in a balanced state due to air introduced into the ink container via air inlet duct  16  into the ink container  13  to enable the ink  2  to be adequately supplied into the inside of the cartridge main  21 .  
      The reservoir  17  is provided between the opening for communication with outside  15  and the air inlet duct  16 , and is used for transiently holding the ink  2  to prohibit the ink from flowing out precipitously when the ink  2  has leaked from the air inlet duct  16  communicating with the ink container  13 . The reservoir  17  is substantially diamond-shaped in cross-section with the long diagonal line of the diamond shape of the reservoir parallel to the longitudinal direction of the ink container  13 . The air inlet duct  16  is provided at a lower apex point of the diamond shape of the ink container  13 , that is, at the lowermost end of the short diagonal line of the reservoir, for restoring the ink  2  which has flown out into the reservoir from the ink container  13  back into the ink container  13 .  
      The opening for communication with outside  15  is also provided at the lowermost apex on the short diagonal line of the reservoir  17  to render it difficult for the ink intruded from the ink container  13  to flow outwards via opening for communication with outside  15 .  
      A plural number of retention lugs  18  are formed on one short lateral side of the ink cartridges  11 , and are engaged with engagement openings  24   a  formed in a plural number of latch levers  24  of the cartridge main  21  of the head cartridge  3 , as shown in  FIGS. 2 and 3 . Each retention lug  18  has its upper surface formed on a plane substantially perpendicular to the lateral surface of the ink container  13 , while having its lower surface inclined from the lateral surface towards the aforementioned upper surface.  
      The engagement steps  19  are provided towards an upper end of the lateral surface of the ink cartridge  11  provided with the retention lugs  18 . Each engagement step  19  is formed by an inclined surface  19   a,  having one end continuing to the upper surface of the cartridge vessel  12 , and a planar surface  19   b,  continuing to the other end of the inclined surface  19   a  and to the opposite side lateral surface of the ink cartridge and extending parallel to the upper surface of the ink cartridge. Since the ink cartridge  11  is provided in this manner with the engagement steps  19 , the height of the lateral surface of the ink cartridge, provided with the planar surfaces  19   b,  is lower by one step than the upper surface of the cartridge vessel  12 , with the ink cartridge  11  engaging at these steps with a plural number of engagement pieces  23  of the cartridge main  21 .  
      The engagement steps  19  are provided on the lateral surface of the ink cartridge on the inserting side when the ink cartridge is inserted into the mounting unit  22  of the head cartridge  3 . The engagement steps are engaged by the engagement pieces  23  of the mounting unit  22  of the head cartridge  3  to serve as a rotational fulcrum point when the ink cartridge  11  is mounted to the mounting unit  22 .  
      The ink cartridge  11 , designed and constructed as described above, includes a residual ink quantity sensor for detecting the residual quantity of the ink  2  in the ink container  13 , and a discriminating unit for discriminating the ink cartridges  11   y,    11   m,    11   c  and  11   k,  in addition to the above-described components.  
      Next, the head cartridge  3 , having loaded the ink cartridges  11   y,    11   m,    11   c  and  11   k,  in which are accommodated the inks  4  of yellow, magenta, cyan and black, respectively, will now be explained.  
      Referring to  FIGS. 2 and 3 , the head cartridge  3  is made up of the ink cartridge  11  and the cartridge main  21 , as described above. The cartridge main  21  includes mounting units  22   y,    22   m,    22   c  and  22   k,  on which are mounted the ink cartridges  11 . In the following, if these mounting units are referred to collectively, they are simply depicted as mounting units  22 . The cartridge main also includes the engagement pieces  23  and the latch levers  24 , for securing the ink cartridge  11 , a biasing member  25  for biasing the ink cartridge  11  in the takeout direction, a connecting unit  26  connected to the ink supply units  14  so as to be supplied with the ink  2 , an head chip  27  for emitting the ink  2 , and a head cap  28  for protecting the head chip  27 .  
      The upper surface of the mounting unit  22 , on which are mounted the ink cartridges  11 , is formed as a recessed portion used as a receiving/ejecting opening for the ink cartridges  11 . Here, four ink cartridges  11  are accommodated side-by-side in the direction substantially perpendicular to the width-wise direction of the recording paper sheet P, that is, along the running direction of the recording paper sheet P. Since the mounting unit  22  receives the ink cartridges  11 , it is arranged with its longitudinal side extending along the printing width, as are the ink cartridges  11 . The ink cartridge  11  is accommodated and mounted in the cartridge main  21 .  
      The mounting unit  22  is an area within which the ink cartridge  11  is mounted, as shown in  FIG. 2 . The mounting unit  22  includes a mounting unit  22   y,  within which the ink cartridge  11   y  for yellow is mounted, a mounting unit  22   m,  within which the ink cartridge  11   m  for magenta is mounted, a mounting unit  22   c,  within which the ink cartridge  11   c  for cyan is mounted, and a mounting unit  22   k,  within which the ink cartridge  11   k  for black is mounted. These mounting units  22   y,    22   m,    22   c  and  22   k  are delimited from one another by partitions  22   a.    
      In general, the black ink cartridge  11   k  consumes much ink and is formed to a larger thickness to accommodate a larger quantity of the ink  2 . Hence, the black ink cartridge is wider in width than the other ink cartridges  11   y,    11   m  and  11   c,  whilst the mounting unit  22   k  is wider in width than the other mounting units  22   y,    22   m  or  22   c  in keeping with the thickness of the ink cartridge  11   k.    
      In an opening end of the mounting unit  22 , in which is mounted the ink cartridge  11 , the engagement pieces  23  are formed, as shown in  FIG. 3 . These engagement pieces  23  are provided on the longitudinal lateral side of the mounting unit  22  and engaged with the engagement steps  19  of the ink cartridge  11 .  
      The ink cartridge  11  may be mounted on the mounting unit  22  by obliquely introducing it into the mounting unit  22 , with the engagement steps  19  of the ink cartridge  11  as a leading end, and by rotating the side of the ink cartridge  11  not having the engagement steps  19  towards the mounting unit  22 , with the engaging locations of the engagement steps  19  and the engagement pieces  23  as the fulcrum point of rotation. By so doing, the ink cartridge  11  may easily be mounted on the mounting unit  22 .  
      The latch levers  24  are each formed by warping a spring plate, as shown in  FIG. 3 . These latch levers are provided on the opposite lateral surface of the mounting unit  22  with respect to the engagement pieces  23  of the mounting unit  22 , that is, on the opposite longitudinal lateral surface of the mounting unit. Each latch lever  24  has its proximal end mounted as one with the bottom side of the opposite lateral surface of the mounting unit  22 , while having its distal end elastically movable in a direction towards and away from this lateral surface. An engagement recess  24   a  is formed towards the distal end of the latch lever.  
      The latch levers  24  are elastically deformed, at the same time as the ink cartridge  11  is mounted to the mounting unit  22 , with the engagement recesses  24   a  engaging with the retention lugs  18  of the ink cartridge  11  for prohibiting the ink cartridge  11  mounted on the mounting unit  22  from being detached from the mounting unit  22 .  
      The biasing member  25  is formed by bending a spring plate, mounted on a bottom surface towards the lateral side provided with the engagement steps  19  of the ink cartridge  11  for biasing the ink cartridge  11  in a direction of detaching the ink cartridge. The biasing member  25  has an apex point, formed by warping, and is elastically displaced in a direction towards and away from the bottom surface. The biasing member pressures the bottom surface of the ink cartridge  11  at its apex point to bias the ink cartridge  11  in a direction of dismounting the ink cartridge from the mounting unit  22 . The biasing member  25  ejects the ink cartridge  11  from the engagement pieces  23  when the retention lugs  18  are disengaged from engagement recesses  24   a  of the latch lever  24 .  
      The connecting units  26 , connected to the ink supply units  14  of the ink cartridges  11   y,    11   m,    11   c  and  11   k,  when the ink cartridges  11   y,    11   m,    11   c  and  11   k  are mounted in the mounting units  22   y,    22   m,    22   c  and  22   k,  are provided at mid portions in the longitudinal direction of the mounting units  22   y,    22   m,    22   c  and  22   k.  These connecting units  26  prove ink supply ducts for supplying the ink  2  to the head chip  27  provided to the bottom surface of the cartridge main  21  for emitting the ink  2  from the ink supply units  14  of the ink cartridges  11  mounted on the mounting units  22 .  
      Specifically, the connecting units  26  are each provided with an ink reservoir  31 , for holding the ink  2  supplied from the ink cartridge  11 , a sealing member  32  for sealing the ink supply unit  14 , connected to the connecting unit  26 , a filter  33  for removing impurities in the ink  2 , and a valving unit  34  for opening/closing the supply passage to the head chip  27 , as shown in  FIG. 5 .  
      The ink reservoir  31  is a space connecting to the ink supply unit  14  and adapted for storing the ink  2  supplied from the ink cartridge  11 . The sealing member  32  is provided at an upper end of the ink reservoir  3  for hermetically sealing the space between the ink reservoir  31  and the ink supply unit  14  to prohibit the ink  2  from leaking to outside when the ink supply unit  14  is connected to the ink reservoir  31 . The filter  33  removes impurities, such as dust and dirt, mixed into the ink  2  during loading/unloading of the ink cartridge  11 , and is provided downstream of the ink reservoir  31 .  
      Referring to  FIGS. 6A and 6B , the valving unit  34  includes an ink inlet duct  34   a,  supplied with the ink  2  from the ink reservoir  31 , an ink chamber  34   b,  supplied with the ink  2  from the ink inlet duct  34   a,  an ink outlet duct  34   c  for allowing the ink  2  to flow outwards from the ink chamber  34   b,  an opening  34   d  provided in the ink chamber  34   b  in an area between the ink inlet duct  34   a  and the ink outlet duct  34   c,  a valve  34   e  for opening/closing the opening  34   d,  and a biasing member  34   f  for biasing the valve  34   e  in a direction of closing the opening  34   d.  The valving unit  34  also includes a negative pressure adjustment screw  34   g  for adjusting the biasing force of the biasing member  34   f,  a valve shaft  34   h  connected to the valve  34   e,  and a diaphragm  34   i  connected to the valve shaft  34   h.    
      The ink inlet duct  34   a  is a supply duct for connecting to the ink container  13  for supplying the ink  2  in the ink container  13  in the ink cartridge  11  via ink reservoir  31  to the head chip  27 . The ink inlet duct  34   a  is provided for extending from the bottom side of the ink reservoir  31  as far as the ink chamber  34   b.  The ink chamber  34   b  is a substantially rectangular spacing formed as one with the ink inlet duct  34   a,  ink outlet duct  34   c  and with the opening  34   d.  The ink  2  flows from the ink inlet duct  34   a  so as to be discharged via opening  34   d  from the ink outlet duct  34   c.    
      The ink outlet duct  34   c  is an ink supply duct in which the ink  2  is supplied from the ink chamber  34   b  via opening  34   d  and which is connected to the head chip  27 . The ink outlet duct  34   c  is extended from the bottom surface side of the ink chamber  34   b  as far as the head chip  27 .  
      The valve  34   e  is used for closing the opening  34   d  for separating the ink inlet duct  34   a  and the ink outlet duct  34   c  from each other, and is provided in the ink chamber  34   b.  The valve  34   e  is movable vertically under the biasing force of the biasing member  34   f,  the force of restoration of the diaphragm  34   i,  connected to the valve shaft  34   h,  and under the negative pressure of the ink  2  towards the ink outlet duct  34   c.    
      When in the lower position, the vale  34   e  closes the opening  34   d  for separating the ink chamber  34   b  into the ink inlet duct  34   a  and the ink outlet duct  34   c  for interrupting the supply of the ink  2  towards the ink outlet duct  34   c.  When in the upper end position, against the bias of the biasing member  34   f,  the valve  34   e  allows the ink  2  to be supplied to the head chip  27  without interrupting the passage between the ink supply from the ink inlet duct  34   a  and the ink outlet duct  34   c  of the ink chamber  34   b.  Although there is no limitation to the material type of the valve  34   e,  it is formed of, for example, a caoutchouc material, or a so-called elastomeric material.  
      The biasing member  34   f  is, for example, a compression coil spring interconnecting the negative pressure adjustment screw  34   g  and the valve  34   e  between the upper surface of the valve  34   e  and the upper surface of the ink chamber  34   b  for biasing the valve  34   e  under its own biasing force in a direction of closing the opening  34   d  with the valve  34   e.  The negative pressure adjustment screw  34   g  is a screw for adjusting the biasing force of the biasing member  34   f  and the biasing force of the biasing member  34   f  may be adjusted by acting on the negative pressure adjustment screw  34   g.  Hence, with the negative pressure adjustment screw  34   g,  it is possible to adjust the negative pressure of the ink  2  actuating the valve  34   e,  adapted for opening/closing the opening  34   d,  as will be explained subsequently in detail.  
      The valve shaft  34   h  is a shaft interconnecting the valve  34   e  connected at one end and the diaphragm  34   i  connected at the other end for enabling the concerted movements of the valve and the diaphragm  34   i.  The diaphragm is a thin elastic sheet connected to the opposite end of the valve shaft  34   h.  This diaphragm  34   i  has one major surface facing the ink outlet duct  34   c  of the ink chamber  34   b  and the opposite major surface in contact with outside air, and is elastically displaced towards the outside air side or towards the ink outlet duct  34   c  under atmospheric pressure and under the negative pressure of the ink  2 .  
      With the above-described valving unit  34 , the valve  34   e  is pressurized in a direction of closing the opening  34   d  of the ink chamber  34   b  under the force of bias exerted by the biasing member  34   f  and that exerted by the diaphragm  34   i,  as shown in  FIG. 6A . When the ink  2  is emitted from the head chip  27  to raise the negative pressure of the ink  2  in the portion of the ink chamber  34   b  towards the ink outlet duct  34   c,  partitioned by the opening  34   d,  the diaphragm  34   i  is uplifted by the atmospheric pressure, under the negative pressure of the ink  2 , to uplift the valve  34   e,  along with the valve shaft  34   h,  against the biasing force of the biasing member  34   f,  as shown in  FIG. 6B .  
      At this moment, the opening  34   d  between the side of the ink inlet duct  34   a  and the side of the ink outlet duct  34   c  of the ink chamber  34   b  is opened to permit the ink  2  to be supplied from the side of the ink inlet duct  34   a  into the side of the ink outlet duct  34   c.  The negative pressure of the ink  2  is lowered, and the diaphragm  34   i  resumes its original shape, by its own force of restoration, with the valve  34   e  being pulled down, along with the valve shaft  34   h,  under the force of bias of the biasing member  34   f,  for closing the ink chamber  34   b.  With the valving unit  34 , the above-described movements are repeated each time the ink  2  is emitted such that the negative pressure of the ink  2  is raised.  
      With the connecting unit  26 , when the ink  2  in the ink container  13  is supplied into the ink chamber  34   b,  the quantity of the ink  2  in the ink container  13  is decreased, however, at this moment, outside air is introduced from the air inlet duct  16  into the ink cartridge  11 . The air introduced into the ink cartridge  11  is sent to an upper portion of the ink cartridge  11 . This restores the state prior to emission of the ink droplet i from a nozzle  44   a,  which will be explained subsequently, so that a state of equilibrium is reached. The state of equilibrium is set up in a condition in which the ink  2  in the air inlet duct  16  is nearly depleted.  
      The head chip  27  is arranged for extending along the bottom surface of the cartridge main  21 , as shown in  FIG. 5 . A plural number of nozzles  44   a,  as ink emitting ports for emitting ink liquid droplets i, supplied from the connecting units  26 , are arranged in a line, from one color to another, along the width-wise direction of the recording paper sheet P, that is, in the direction indicated by arrow W in  FIG. 5 .  
      The head cap  28  is a cover provided for protecting the head chip  27 , as shown in  FIG. 2 , and is dismounted from the head chip  27  in carrying out the printing operation. The head cap  28  is provided with a groove  28   a,  provided in the opening/closing direction, and a cleaning roll  28   b,  extending longitudinally for sucking excess ink  2  deposited on an emitting surface  27   a  of the head chip  27 .  
      The head cap  28  is opened/closed along this groove  28   a  in the transverse direction of the ink cartridge  11 . At this moment, the cleaning roll  28   b  is rotated, as it abuts against the emitting surface  27   a  of the head chip  27  to suck up any excess ink  2  to clean the emitting surface  27   a  of the head chip  27 . The cleaning roll  28   b  is formed of, for example, a highly hygroscopic material. When the printing apparatus is not in operation for printing, the head cap  28  protects the ink  2  in the head chip  27  against drying.  
      The above-described head cartridge  3  includes a residual ink quantity detecting unit for detecting the residual quantity of the ink in the ink cartridge  11 , and an ink presence/absence detecting unit for detecting the presence/absence of the ink  2 , when the ink supply unit  14  is connected to the connecting unit  26 , as an example, in addition to the above components.  
      Referring to  FIGS. 7 and 8 , the head chip  27  for each color ink  2  includes, from one color to another, a circuit substrate  41 , as a base, a pair of heating resistors  42   a,    42   b,  arranged side-by-side in a direction substantially perpendicular to the running direction of the recording paper sheet P, that is, along the width-wise direction of the recording paper sheet P, a film  43  for preventing leakage of the ink  2 , and a nozzle sheet  44  having many nozzles  44   a  through which the ink  2  is emitted in the form of liquid droplets. The head chip also includes ink liquid chambers  45 , defining a space through which the ink  2  is supplied, and ink flow ducts  46  for supplying the ink  2  to the ink liquid chambers  45 .  
      The circuit substrate  41  is a semiconductor substrate of, for example, silicon, and includes a pair of heating resistors  42   a,    42   b  on its major surface  41   a.  These heating resistors  42   a,    42   b  are connected to an emission controller  63 , as later explained, provided on the circuit substrate  41 . This emission controller  63  is an electronic circuit formed by e.g. a logic IC (integrated circuit) and a driver transistor.  
      The paired heating resistors  42   a,    42   b  are pressure generating devices which are heated by the pulse current supplied from the emission controller  63  to heat the ink  2  in the ink liquid chambers  45  to raise the internal pressure. The ink  2 , heated by these paired heating resistors  42   a,    42   b,  is emitted as liquid droplets via nozzles  44   a  provided in the nozzle sheet  44 , as will be explained subsequently.  
      The film  43  is formed on one major surface  41  a of the circuit substrate  41 . The film  43  is a dry film resist of, for example, the type hardened on light exposure. It is first formed on substantially the entire area of the major surface  41   a  of the circuit substrate  41  and subjected to a photolithographic process for removing unneeded portions. The film is formed for surrounding the paired heating resistors  42   a,    42   b  in recessed portions. The portions of the film  43  surrounding the paired heating resistors  42   a,    42   b  form part of the ink liquid chambers  45 .  
      The nozzle sheet  44  is a sheet-like member, with a thickness on the order of 10 to 15 μm, provided with the nozzles  44   a  for emitting the ink droplets i, and is formed on the surface of the film  43  opposite to the circuit substrate  41 . The nozzles  44   a  are openings of an extremely small diameter of the order of 15 to 18 μm, opened as circular holes in the nozzle sheet  44 . The nozzles  44   a  are arranged facing the paired heating resistors  42   a,    42   b.  The nozzle sheet  44  forms a part of the ink liquid chambers  45 .  
      The ink liquid chambers  45  are each an area surrounded by the circuit substrate  41 , paired heating resistors  42   a,    42   b,  film  43  and the nozzle sheet  44  for storage of the ink  2  supplied from the ink flow duct  46 . Each ink liquid chamber forms a space in which is stored the ink  2  supplied from the ink flow duct  46 . The ink liquid chamber  45  is heated by the paired heating resistors  42   a,    42   b  whereby the inner pressure in the ink liquid chambers  45  is raised.  
      The ink flow duct  46  is connected to the ink outlet duct  34   c  of the connecting unit  26 , and is supplied with the ink  2  from the ink cartridge  11  connected to the connecting unit  26 . The ink flow duct forms a flow passage for delivery of the ink  2  to each ink liquid chamber  45  communicating with the ink flow duct  46 . That is, the ink flow duct  46  communicates with the connecting unit  26 . Hence, the ink  2  supplied from the ink cartridge  11  flows into the ink flow duct  46  so as to be charged into the ink liquid chamber  45 .  
      The aforementioned sole head chip  27  includes 100 to 5000 ink liquid chambers  45  for each color ink cartridge  11  provided with the paired heating resistors  42   a,    42   b.  The paired heating resistors  42   a,    42   b  are provided to each ink liquid chamber  45 . In the head chip  27 , the paired heating resistors  42   a,    42   b  are selected and generate heat under a command from a controller  68  of the printer apparatus  1 . The ink  2  contained in the ink liquid chamber  45 , associated with the heated paired heating resistors  42   a,    42   b,  is emitted as liquid droplets from the nozzle  44   a  associated with the ink liquid chamber  45 .  
      That is, in the head chip  27 , the ink  2  supplied from the ink flow duct  46  coupled to the head chip  27 , is charged into the ink liquid chamber  45 . The pulse current is caused to flow through the paired heating resistors  42   a,    42   b  for a short time, for example, for 1 to 3 μsec, for quickly heating the paired heating resistors  42   a,    42   b,  as a result of which the portion of the ink  2  in contact with the paired heating resistors  42   a,    42   b  is heated to generate ink bubbles in the gaseous phase. Thus, a certain volume of the ink  2  is pressurized by the expansion of the ink air bubbles (ebullition of ink  2 ). Hence, the ink  2  in contact with the nozzle  44   a  is emitted in a quantity equivalent to the volume of the ink  2 , pressurized by the expanded ink air bubbles, so as to be deposited as ink liquid droplet i on the recording paper sheet P.  
      In this head chip  27 , the paired heating resistors  42   a,    42   b  are arranged side-by-side, approximately parallel to each other, in the sole ink liquid chamber  45 , as shown in  FIG. 8 . That is, the paired heating resistors  42   a,    42   b  are provided in the sole ink liquid chamber  45 . In the head chip  27 , a plural number of the paired heating resistors  42   a,    42   b,  arranged parallel to each other, are arranged side-by-side in the direction substantially orthogonal to the running direction of the recording paper sheet P, indicated by arrow C in  FIG. 8 , that is, in the width-wise direction of the recording paper sheet P, as indicated by arrow W in  FIG. 8 . Meanwhile, the location of the nozzle  44   a  is indicated by a chain-dotted line in  FIG. 8 .  
      The paired heating resistors  42   a,    42   b  are each a division in two of a sole resistor, with the length being the same and the width being halved, so that the resistance value of each resistor is approximately doubled. If the resistors of the paired heating resistors  42   a,    42   b  are connected in series, two resistors each having the resistance value doubled, are connected in series, so that the resistance value is four times that prior to division.  
      In order for ebullition of the ink  2  to occur in the ink liquid chamber  45 , the paired heating resistors  42   a,    42   b  need to be heated by applying a constant pulse current to the paired heating resistors  42   a,    42   b,  so that the ink droplets i will be emitted by the energy generated by ebullition. If the resistance value is small, it is necessary to increase the pulse current caused to flow. Since resistance value of the paired heating resistors  42   a,    42   b,  equivalent to a sole resistor divided in two portions, is higher than that of the undivided sole resistor, ebullition may be produced with the pulse current of a small current value.  
      In this manner, in the head chip  27 , the size of e.g. transistors, through which the pulse current is caused to flow, may be reduced to save space. Although the resistance value may further be raised by reducing the thickness of the paired heating resistors  42   a,    42   b,  there is a certain limit imposed on reducing the thickness of the paired heating resistors  42   a,    42   b,  from the perspective of strength or durability and the material selected of the paired heating resistors  42   a,    42   b,.  For this reason, the resistance value of the paired heating resistors  42   a,    42   b  is increased by dividing the sole resistor in two, instead of by reducing their thicknesses.  
      It should be noted that, in emitting the ink in the ink liquid chamber  45  through the nozzle  44   a,  the ink droplet i may be emitted vertically downward from the nozzle  44   a  by driving controlling the paired heating resistors  42   a,    42   b  so that the time until ebullition of the ink in the ink liquid chamber  45  by the paired heating resistors  42   a,    42   b,  that is, the time duration for air bubble generation, will be the same for the paired heating resistors.  
      If time difference is produced in the air bubble generation time duration of the paired heating resistors  42   a,    42   b,  it becomes difficult to generate ink bubbles at about the same time by the paired heating resistors  42   a,    42   b,  with the result that the ink droplets are emitted with an offset towards one of the arraying directions of the paired heating resistors  42   a,    42   b.    
      Specifically, the ink  2  is supplied by the ink flow duct  46 , coupled to the head chip  27 , so that the ink  2  is charged in the ink liquid chamber  45 , as shown in  FIG. 9 . The pulse currents of the same current value are caused to flow approximately simultaneously, so that the paired heating resistors  42   a,    42   b  are heated quickly, as a result of which gaseous ink air bubbles B 1 , B 2  are generated in the portions of the ink  2  contacted with the paired heating resistors  42   a,    42   b.  These ink air bubbles B 1 , B 2  are expanded to pressurize the ink  2  of a preset volume. Hence, in the head chip  27 , the ink  2  of the same volume as the ink  2  pressurized substantially vertically by the ink air bubbles B 1 , B 2  in the portion of the ink contacted with the nozzle  44   a  is emitted substantially vertically from the nozzle  44   a,  as ink liquid droplet i, so as to be deposited on the recording paper sheet P, as shown in  FIG. 10 .  
      In the explanation to follow, it is assumed that the ink air bubbles B 1  and B 2  are formed on the heating resistors  42   a  and  42   b,  respectively.  
      Moreover, with the head chip  27 , ink air bubbles B 1  and B 2  of different sizes are generated in the portions of the ink  2  contacted with the heating resistors  42   a  and  42   b,  by supplying the pulse currents of the different values to the paired heating resistors  42   a,    42   b  approximately simultaneously, as shown in  FIG. 11 . By expansion of these ink air bubbles B 1  and B 2 , the ink  2  of a preset volume is pressurized. Thus, in the head chip  27 , the same volume of the ink  2  as that of the ink  2  pressurized by the ink air bubbles B 1  and B 2  in the ink portion contacted by the nozzle  44   a  is emitted as ink liquid droplet i from the nozzle  44   a,  with an offset towards one with a smaller volume of the ink air bubbles B 1  and B 2 , along the width-wise direction of the recording paper sheet P, as indicated by arrow W in  FIG. 12 , so as to be deposited on the recording paper sheet P, as shown in  FIG. 12 . It may be seen that  FIG. 12  shows that the volume of the ink air bubble B 1 , formed on the heating resistor  42   a,  has become larger than that of the ink air bubble B 2  formed on the heating resistor  42   b.    
      With the above-described head chip  27 , since the ink  2 , containing the surfactant, containing in turn at least the organic compound having the above-mentioned chemical formula 1, is supplied to the ink liquid chamber  45 , there is little risk that bubbles other than the ink air bubbles B 1 , B 2  formed by the paired heating resistors  42   a,    42   b  are generated in the ink  2  in the ink liquid chamber  45 , with the result that it is possible to prohibit an inconvenience that an air bubble generated in the ink in the ink liquid chamber obstructs supply of the ink onto the heating resistor or emission of the ink from the nozzle.  
      With the head chip  27 , since the ink  2  supplied to the ink liquid chamber  45  contains the surfactant, containing in turn at least the organic compound having the above-mentioned chemical formula 1, and the ink  2  exhibits superior wetting performance not only to the recording paper sheet P but also to the inner peripheral surface of the ink liquid chamber  45 , paired heating resistors  42   a,    42   b  or to the nozzle  44   a,  the ink  2  may be supplied promptly to the paired heating resistors  42   a,    42   b  right after emitting the ink liquid droplet i from the nozzle  44   a.  Hence, with the present head chip  27 , the ink  2  may be supplied quickly to the paired heating resistors  42   a,    42   b  each time the ink liquid droplet i is emitted. That is, since the ink  2  is supplied properly at all times into the ink liquid chamber  45 , the ink liquid droplet i may be properly emitted from the nozzle  44   a  even though the ink liquid droplet i is emitted at short emission time intervals.  
      Furthermore, with the present head chip  27 , the ink  2  supplied to the ink liquid chamber  45  contains a surfactant containing in turn at least the organic compound having the above-mentioned chemical formula 1, and the surfactant has the cloud point of approximately 80° C. which is higher than that of the conventional surfactant, there is little risk that the temperature of the ink  2 , heated by the paired heating resistors  42   a,    42   b,  exceeds the cloud point of the surfactant, with the consequence that the ink undergoes changes in physical properties.  
      Thus, with the present head chip  27 , the temperature of the ink  2  in the ink liquid chamber  45  is not liable to exceed the cloud point of the surfactant, and the physical properties of the ink  2  are stabilized, such that wettability of the ink  2  for the inner peripheral surface, paired heating resistors  42   a,    42   b  or the nozzle  44   a  may be maintained, with the result that the ink liquid droplet i may be emitted properly from the nozzle  44   a.    
      The printer main  4 , constituting the printer apparatus  1 , on which is mounted the head cartridge  3 , formed as described above, will now be explained with reference to the drawings.  
      Referring to  FIGS. 1 and 13 , the printer main  4  includes a head cartridge mounting unit  51 , on which is loaded the head cartridge  3 , a head cartridge holding unit  52  for holding and securing the head cartridge  3  to the head cartridge mounting unit  51 , a head cap opening/closing unit  53 , for opening/closing the head cap, and a paper sheet feed/discharge unit  54 , for supplying and discharging the recording paper sheet P. The printer main  4  also includes a paper sheet feed port  55  for supplying the recording paper sheet P to the paper sheet feed/discharge unit  54 , and a paper sheet discharge port  56  for outputting the recording paper sheet P from the paper sheet feed/discharge unit  54 .  
      The head cartridge mounting unit  51  is a recess within which is mounted the head cartridge  3 . The head cartridge  3  is mounted so that, for printing data correctly on the running paper sheet, the emitting surface  27   a  of the head chip  27  will be substantially parallel to the plane of the recording paper sheet P.  
      There are occasions wherein the head cartridge  3  needs to be replaced by e.g. the ink stopping up the head chip  27 . Hence, the head cartridge  3  is a consumable item, although it is not to be exchanged so often as the ink cartridge  11 . Hence, the head cartridge is held by the head cartridge holding unit  52  so as to be dismounted as desired from the head cartridge mounting unit  51 .  
      The head cartridge holding unit  52  is a unit which detachably holds the head cartridge  3  with respect to the head cartridge mounting unit  51 . A knob  52   a  provided to the head cartridge  3  is retained by a biasing member, such as a spring, not shown, provided in a retention opening  52   b  of the printer main  4 . This fits the head cartridge  3  by pressure fit against a reference plane  4   a  provided to the printer main  4 , thereby positioning and fixing the head cartridge  3 .  
      The head cap opening/closing unit  53  includes a driving unit for opening/closing the head cap  28  of the head cartridge  3 . For printing, the head cap  28  is opened for exposing the head chip  27  to the recording paper sheet P and, when the printing has come to a close, the head cap  28  is closed to protect the head chip  27 .  
      The paper sheet feed/discharge unit  54  includes a driving unit for transporting the recording paper sheet P. The driving unit transports the recording paper sheet P, supplied from the paper sheet feed port  55 , to the head chip  27  of the head cartridge  3 , while transporting the printed paper sheet P to the paper sheet discharge port  56  to discharge it to outside the apparatus, as the ink droplets i, emitted from the nozzle  44   a,  remain deposited thereon. The paper sheet feed port  55  is an opening for feeding the recording paper sheet P to the paper sheet feed/discharge unit  54 , and is able to hold a stack of plural recording paper sheets P on e.g. a tray  55   a.  The paper sheet discharge port  56  is an opening via which is discharged the recording paper sheet P on which the ink droplets i have become deposited to finish the printing.  
      A control circuit  61 , controlling the printing by the printer apparatus  1 , constructed as described above, and shown in  FIG. 14 , will now be explained with reference to the drawings.  
      The control circuit  61  includes a printer driver  62 , for driving controlling the units  53  and  54  of the printer main  4 , an emission controller  63  for controlling e.g. the current supplied to the head chip  27  associated with the inks  4  of different colors, and an alerting unit  64  for alerting the residual quantity of the inks  4  of different colors. The control circuit also includes an input/output terminal  65  for inputting/outputting signals for an external device, and a ROM (read-only memory)  66  having recorded e.g. a control program. The control circuit further includes a RAM (random-access memory)  67  transiently storing e.g. a control program for reading out as necessary, and a controller  68  for controlling various parts.  
      The printer driver  62  controls the head cap opening/closing unit for opening/ closing the head cap  28  by actuating a driving motor constituting the head cap opening/closing unit  53  based on the control signal from the controller  68 .  
      The printer driver  62  also actuates a driving motor, constituting the paper sheet feed/discharge unit  54 , based on a control signal from the controller  68 , to feed the recording paper sheet P from the paper sheet feed port  55  of the printer main  4 , to discharge the paper sheet P from the paper sheet discharge port  56 .  
      Referring to  FIG. 15 , the emission controller  63  is an electrical circuit including power sources  71   a,    71   b  for supplying pulse current to the paired heating resistors  42   a,    42   b,  which are resistor elements, switch devices  72   a  to  72   c,  for turning the electrical connection between the paired heating resistors  42   a,    42   b  and the power sources  71   a,    71   b  on or off, and a variable resistor  73  for controlling the pulse currents supplied to the paired heating resistors  42   a,    42   b.  The emission controller also includes switching control circuits  74   a,    74   b  for controlling the switching of the switch devices  72   b  and  72   c,  and a resistance value control circuit  75  for controlling the resistance value of the variable resistor  73 .  
      The power source  71  a is connected to the heating resistor  42   b,  while the power source  71   b  is connected via switch device  72   c  to the variable resistor  73 . Both the power sources supply the pulse current to the electrical circuit. Meanwhile, although the pulse current supplied to the electrical circuit may be supplied from the power sources  71   a,    71   b,  the pulse current may also be directly supplied from for example the controller  68 .  
      The switch device  72   a  is arranged between the paired heating resistor  42   a  and the ground to control the on/off of the emission controller  63  in its entirety. The switch device  72   b  is connected across the paired heating resistors  42   a,    42   b  and the variable resistor  73  to control the pulse current supplied to the paired heating resistors  42   a,    42   b.    
      The switch device  72   c  is arranged between the variable resistor  73  and the power source  71   b  to control the direction of emission of the ink droplet i. These switch devices  72   a  to  72   c  are on/off controlled to control the pulse current supplied to the electrical circuit.  
      The variable resistor  73  varies its own resistance value to change the current value of the pulse current supplied to the heating resistor  42   a.  That is, the current value of the pulse current, supplied to the heating resistor  42   a,  is determined by the magnitude of the resistance of the variable resistor  73 .  
      The switching control circuit  74   a  changes over the on/off of the switch device  72   b  to connect the variable resistor  73  to the paired heating resistors  42   a,    42   b  or turns off the variable resistor  73  and the paired heating resistors  42   a,    42   b.  The switching control circuit  74   b  changes over the on/off of the switch device  72   c  to change over the on/off of the electrical connection across the power source  71   b  and the electrical circuit.  
      The resistance value control circuit  75  controls the magnitude of the resistance value of the variable resistor  73  to adjust the value of the pulse current supplied to the heating resistor  42   a.    
      If, in the above-described emission controller  63 , the switch device  72   b  is turned off, with there being no electrical connection across the variable resistor  73  and the paired heating resistors  42   a,    42   b,  and the switch device  72   a  is turned on, the pulse current is supplied from the power source  71   a  to the series-connected paired heating resistors  42   a,    42   b.  At this moment, no current flows through the variable resistor  73 . If the resistance values of the paired heating resistors  42   a,    42   b  are approximately equal to each other, the heat values generated by the paired heating resistors  42   a,    42   b  when the pulse current is supplied thereto, is approximately equal to each other.  
      In this case, the heat values generated in the paired heating resistors  42   a,    42   b  in the head chip  27  become approximately equal to each other, and the time duration of air bubbles, that is, the air bubble generation timing, become approximately equal to each other. Since the air bubbles of approximately the same volume are generated on the paired heating resistors  42   a,    42   b,  the angle of emission of the ink  2  is approximately orthogonal to the major surface of the recording paper sheet P, with the ink droplet i being emitted substantially directly downwards from the nozzle  44   a.    
      In the emission controller  63 , shown in  FIG. 15 , in case the switch device  72   b  has turned on the electrical connection between the paired heating resistors  42   a,    42   b  and the variable resistor  73 , the switch device  72   a  is turned on, and the switch device  72   c  is connected to the ground, the ink droplet i, emitted from the head chip  27 , is emitted as the emitting direction is offset towards the heating resistor  42   a  along the width-wise direction W of the recording paper sheet P, as shown in  FIG. 16B . That is, since the switch device  72   c  is connected to the ground, the current value of the pulse current supplied to the heating resistor  42   a  becomes smaller in proportion to the resistance value of the variable resistor  73 . Since the ink air bubbles B 1  and B 2  are formed on the paired heating resistors  42   a,    42   b,  respectively, as the volume of the ink air bubble B 1  has become smaller than that of the ink air bubble B 2 , the ink liquid droplet i is emitted obliquely from the nozzle  44   a  as the angle of emission of the ink  2  is offset towards the heating resistor  42   a.    
      In this emission controller  63 , the current value of the pulse current, supplied to the heating resistor  42   b  is unchanged, while the current value of the pulse current supplied to the heating resistor  42   a  is changed. In this case, if the resistance value of the variable resistor  73  is high, the current flowing to the ground from the power source  71   a  through the switching device  72   c  becomes small, with the result that the amount of decrease of the pulse current supplied from the power source  71   a  to the heating resistor  42   a  is small. Hence, the difference of the pulse currents supplied to the paired heating resistors  42   a,    42   b  becomes smaller, with the difference in the heat values generated by the paired heating resistors  42   a,    42   b  becoming smaller and with the angle of emission of the ink liquid droplet i from the nozzle  44   a,  with the emitting surface  27   a  as reference, becoming larger. That is, the larger the resistance value of the variable resistor  73 , the closer on the side of the heating resistor  42   a  becomes the point of deposition of the ink liquid droplet i to the point of deposition D for the ink liquid droplet i emitted substantially directly downward from the nozzle  44   a.  If conversely the resistance value of the variable resistor  73  is low, the current flowing to the ground from the power source  71   a  through the switching device  72   c  becomes larger, such that the amount of decrease of the pulse current supplied from the power source  71   a  to the heating resistor  42   a  is increased. Hence, the difference of the pulse currents supplied to the paired heating resistors  42   a,    42   b  becomes larger, with the difference in the heat values generated by the paired heating resistors  42   a,    42   b  becoming smaller and with the angle of emission of the ink liquid droplet i from the nozzle  44   a,  with the emitting surface  27   a  as reference, becoming smaller. That is, the smaller the resistance value of the variable resistor  73 , the remoter on the side of the heating resistor  42   a  becomes the point of deposition of the ink liquid droplet i to the point of deposition D for the ink liquid droplet i emitted substantially directly downward from the nozzle  44   a.    
      If, in the emission controller  63 , shown in  FIG. 15 , the switching device  72   b  has turned on the connection between the paired heating resistors  42   a,    42   b  and the variable resistor  73 , the switching device  72   a  is turned on and the switching device  72   c  is connected to the power source  71   b,  the ink liquid droplet i, emitted from the head chip  27 , is emitted as its direction of emission has been changed towards the heating resistor  42   b  along the width-wise direction of the recording paper sheet P shown in  FIG. 16C . That is, since the switching device  72   c  is connected to the power source  71   b,  the current value of the pulse current supplied to the heating resistor  42   a  becomes larger in proportion to the resistance value of the variable resistor  73 , and hence the ink air bubbles B 1  and B 2  are formed on the paired heating resistors  42   a,    42   b  as the ink air bubble B 2  has become smaller in volume than the ink air bubble B 1 . Hence, the ink liquid droplet i is emitted substantially obliquely from the nozzle  44   a  as the angle of emission of the ink  2  is offset towards the heating resistor  42   b.  In the head chip  27 , the heating state of the paired heating resistors  42   a,    42   b  is reversed from that in case the switching device  72   c  is connected to the ground. If, in this case, the resistance value of the variable resistor  73  is high, the pulse current supplied to the heating resistor  42   a  from the power source  71   b,  in addition to the current supplied from the power source  71   a,  becomes smaller, so that the difference of the pulse currents supplied to the paired heating resistors  42   a,    42   b  becomes smaller, with the difference in the heating values between the paired heating resistors  42   a,    42   b  also becoming smaller. Hence, the angle of emission of the ink liquid droplet i from the nozzle  44   a,  with the emitting surface  27   a  as a reference, becomes larger. That is, the higher the resistance of the variable resistor  73 , the closer becomes the point of deposition of the ink liquid droplet i on the side of the heating resistor  42   b  to the point of deposition D for the ink liquid droplet i emitted substantially vertically downward from the nozzle  44   a.    
      If, on the other hand, the resistance value of the variable resistor  73  is low, the pulse current supplied to the heating resistor  42   a  from the power source  71   b,  in addition to the current supplied from the power source  71   a,  becomes larger, so that the difference of the pulse currents supplied to the paired heating resistors  42   a,    42   b  becomes larger, with the difference in the heating values between the paired heating resistors  42   a,    42   b  also becoming larger. Hence, the angle of emission of the ink liquid droplet i from the nozzle  44   a,  with the emitting surface  27   a  as a reference, becomes smaller. That is, the lower the resistance of the variable resistor  73 , the remoter becomes the point of deposition of the ink liquid droplet i on the side of the heating resistor  42   b  to the point of deposition D for the ink liquid droplet i emitted substantially vertically downward from the nozzle  44   a.    
      Thus, with the emission controller  63 , the switching devices  72   a  to  72   c  may be changed over and the resistance value of the variable resistor  73  may also be changed to change the direction of emission of the ink liquid droplet i from the nozzle  44   a  along the arraying direction of the paired heating resistors  42   a,    42   b,  that is, along the width-wise direction of the recording paper sheet P.  
      In the foregoing, the current value supplied to the heating resistor  42   a  is adjusted by controlling the resistance value of the variable resistor  73 . However, this is not limitative of the present invention. For example, the power source  71   a  may be connected to the heating resistor  42   a  to vary the current value supplied to the heating resistor  42   b.    
      The alerting unit  64 , shown in  FIG. 14 , is a display means, such as LCD (liquid crystal display), and demonstrates the information, such as printing conditions, printing states or the residual ink quantities. The alerting unit  64  may, for example, be voice outputting means, such as a loudspeaker, in which case the information of, for example, the printing conditions, printing states or the residual ink quantities, is output by voice. Meanwhile, the alerting unit  64  may own both the display means and the voice outputting means. The alerting may also be made using a monitor or a loudspeaker of an information processing system  69 .  
      The input/output terminal  65  sends the above information, such as printing conditions, printing states or the residual ink quantities, to for example the external information processing system  69  over an interface. The input/output terminal  65  is also supplied with a control signal for outputting the above information, such as printing conditions, printing states or the residual ink quantities, or with e.g. printing data from e.g. the external information processing system  69 . The information processing system  69  is an electronic apparatus, such as, for example, a personal computer or a PDA (Personal Digital Assistance).  
      The input/output terminal  65 , connected to for example the information processing system  69 , may use, for example, a serial interface or a parallel interface, as interface, and is conformant to existing standards, specifically, the standards for USB (Universal Serial Bus), RS (Recommended Standard) 232C or IEEE (Institute of Electrical and Electronic Engineers) 1394.  
      The input/output terminal  65  may be configured to perform data communication with the information processing system  69  in accordance with a wired or wireless communication system. The relevant wireless communication standards may include IEEE802.11a, 802.11b and 802.11g.  
      Between the input/output terminal  65  and the information processing system  69  may be interposed a network, such as the Internet. In this case, the input/output terminal  65  is connected to for example LAN (Local Area Network), ISDN (Integrated Services Digital Network), xDSL (Digital Subscriber Line), FTHP (Fiber to The Home), CATV (Community Antenna Television) or BS (Broadcasting Satellite). Data communication is carried out in accordance with various protocols, such as TCP/IP (Transmission Control Protocol/Internet Protocol).  
      A ROM  66  is a memory, such as EP-ROM (Erasable Programmable Read-Only Memory), having stored therein a variety of programs for processing carried out by the controller  68 . The programs stored in the ROM may be loaded on the RAM  67  by the controller  68 . The RAM  67  stores the programs, read out by the controller  68  from the ROM  66 , and the various states of the printer apparatus.  
      The controller  68  controls various components, based on for example the printing data, supplied from the input/output terminal  65 , or on data on the residual quantity of the ink  2 , entered from the head cartridge  3 . The control programs for controlling various components, based on for example the control signal as entered, are read out from the ROM  66 , under control by the controller  68 , and stored in the RAM  67 , and various components are controlled or processed based on the processing program.  
      That is, the controller  68  controls the emission controller  63 , based on for example the processing program, so that the current value difference of the pulse current flowing through the heating resistor  42   a  from that flowing through the heating resistor  42   b  will be within ±10%, such as not to produce variations in the emitting directions of the ink droplets i emitted from the nozzles  44   a.    
      In the above-described control circuit  61 , the processing programs are stored in the ROM  66 . However, the processing programs do not have to be stored in the ROM  66 , and a variety of recording mediums, such as optical discs, magnetic disc, magneto-optical discs or IC cards, having the processing programs stored therein, may also be used. The control circuit  61  is arranged so that it is connected to a drive for driving various recording mediums, either directly or via information processing system  69 , to read out processing programs from these recording mediums.  
      The printing operation of the printing apparatus  1 , arranged as described above, will now be explained with reference to the flowchart shown in  FIG. 19 . Meanwhile, the present printing operations are carried out by arithmetic processing on a CPU (Central Processing Unit), not shown, provided in the controller  68 , based on a processing program stored in storage means, such as ROM  66 .  
      Initially, a user operates an operating panel, provided to the printer main  4 , and issues a command to the printer apparatus  1  to carry out the printing operations. The controller  68  then verifies, in a step S 1 , whether or not ink cartridges  11  of preset colors have been mounted to the respective mounting units  22 .  
      If the ink cartridges  11  of preset colors have been adequately mounted to all of the mounting units  22 , the controller  68  proceeds to a step S 2 . In case the ink cartridges  11  of preset colors have not been adequately mounted on the mounting unit  11 , the controller  68  proceeds to a step S 4  to inhibit the printing.  
      The controller  68  in the step S 2  verifies whether or not the quantity of the ink  2  in the connecting unit  26  is lesser than a preset value, that is, whether or not the ink  2  has become depleted. In case it is found that the ink  2  has become depleted, that effect is alerted in the alerting unit  64 . The printing operation is then inhibited in the step S 4 . If conversely the quantity of the ink  2  in the connecting unit  26  is in excess of a preset value, that is, if the ink  2  has been charged, the printing operation is allowed in a step S 3 .  
      In effecting the printing, the controller  68  performs driving control of the driving units  53  and  54  by the printer controller  62  to cause movement of the recording paper sheet P to a printing enabling position. Specifically, the controller  68  drives a driving motor of the head cap opening/closing unit  53  to cause movement of the head cap  28  towards the tray  55   a  with respect to the head cartridge  3  to expose the nozzles  44   a  of the head chip  27 , as shown in  FIG. 20 .  
      The controller  68  drives a driving motor, forming the paper sheet feed/discharge unit  54 , to cause the running of the recording paper sheet P. Specifically, the controller  68  controls the paper sheet feed/discharge unit  54  so that a recording paper sheet P is pulled out from the tray  55   a  by the paper sheet feed roll  81  and sent to the inverting roll  83  by a pair of separating rolls  82   a,    82   b,  rotating in opposite directions, the recording paper sheet P is then sent to a transporting belt  84 , and the recording paper sheet P, transported to the transporting belt  84 , is retained at a preset position by a retention means  85  to determine the position of deposition of the ink  2 .  
      When the controller  68  has verified that the recording paper sheet P has been retained in the printing position, the controller  68  controls the emission controller  63  for emitting the ink droplets i towards the recording paper sheet P from the nozzles  44   a  of the head chip  27 . Specifically, the controller controls the emission controller  63  so that, in case the ink droplet i is to be emitted substantially vertically downward from the nozzle  44   a,  the current values of the pulse currents supplied to the paired heating resistors  42   a,    42   b  will be approximately equal to each other, as shown in  FIG. 16A . If, in emitting the ink from the nozzle  44   a,  the direction of the ink emission is varied so that the ink will be emitted offset towards the heating resistor  42   a,  the controller  68  controls the emission controller  63  so that the current value of the pulse current supplied to the heating resistor  42   a  will be smaller than that of the pulse current supplied to the heating resistor  42   b,  as shown in  FIG. 16B . I, in emitting the ink from the nozzle  44   a,  the ink is to be emitted offset towards the heating resistor  42   b,  the controller  68  controls the emission controller  63  so that the current value of the pulse current supplied to the heating resistor  42   a  will be larger than that of the pulse current supplied to the heating resistor  42   b,  as shown in  FIG. 16C .  
      Thus, in case the ink droplet i has been emitted from the nozzle  44   a,  the same quantity of the ink  2  as the emitted quantity of the ink droplets i is quickly replenished from the ink flow duct  46  into the ink chamber  45  to restore the original state, as shown in  FIG. 6B .  
      When the ink droplet i is emitted from the head chip  27 , and the negative pressure of the ink  2  in the portion of the ink chamber  34  located towards the ink outlet duct  34   c,  that is, towards the opening  34   d,  is raised, the diaphragm  34   i  is uplifted by atmospheric pressure, under the negative pressure of the ink  2 . This uplifts the valve  34   e,  which has so far closed the opening  34   d  of the ink chamber  34   b  by the biasing force of the biasing member  34   f  and that of the diaphragm  34   i,  against the biasing force of the biasing member  34   f,  along with the valve shaft  34   h,  as shown in  FIG. 6A . At this moment, the opening  34   d  between the side of the ink inlet duct  34   a  and the side of the ink outlet duct  34   c  of the ink chamber  34   b  is opened, so that the ink  2  is supplied from the side of the ink inlet duct  34   a  to the side of the ink outlet duct  34   c.  The ink  2  is replenished in the ink flow duct  46  of the head chip  27 . The negative pressure of the ink  2  is lowered and the diaphragm  34   i  is restored to its original shape, by its force of restoration. The valve  34   e  is pulled down, along with the valve shaft  34   h,  by the biasing force of the biasing member  34   f,  such as to close the ink chamber  34   b.  In the valving unit  34 , the above-described sequence of operations is repeated when the negative pressure of the ink  2  is raised each time the ink droplet i is emitted.  
      In this manner, the letters/characters or images, which are in keeping with the printing data, are sequentially printed on the recording paper sheet P which is being run by the paper sheet feed/discharge unit  54 . On completion of the printing, the recording paper sheet P is discharged via paper sheet discharge port  56  by the paper sheet feed/discharge unit  54 .  
      In the above-described printer apparatus  1 , the ink  2 , at least containing a surfactant, in turn containing the organic compound represented by the above chemical formula 1, is contained in the ink cartridge  11 , this ink  2  being emitted as ink liquid droplet i via nozzle  44   a  onto the recording paper sheet P. Since the ink  2  exhibits superior wettability for the recording paper sheet P and promptly penetrates into the bulk of the recording paper sheet P along the direction of its thickness, printing may be made to high image quality without causing bleeding at the point of deposition of the ink liquid droplet i. Specifically, even in case plain paper sheets, such as copy paper sheets, bond paper sheets or report paper sheets, are used as the recording paper sheet P, it is possible to suppress the deposited ink liquid droplet i from becoming bled along the fibers of the plain paper sheets.  
      In the printer apparatus  1  of the present invention, the ink  2  exhibiting superior wettability for the recording paper sheet P is emitted from the nozzle  44   a  as ink liquid droplets i for printing on the recording paper sheet P, and hence the ink liquid droplet i deposited seeps quickly into the bulk of the recording paper sheet P so as to be there dried in situ. As a result, even if the printed portion of the recording paper sheet is scrubbed directly after printing, there is no risk of the point of deposition of the ink liquid droplet i becoming blurred to degrade the image quality.  
      With the present printing apparatus  1 , in which the ink  2 , at least containing the surfactant, containing in turn the organic compound represented by the above chemical formula 1, is contained in the ink cartridge  11 , and in which this ink  2  is supplied into the ink liquid chamber  45 , it is possible to prevent bubbles, other than the ink air bubbles B 1  or B 2 , from being generated in the ink  2  in the ink liquid chamber  45 . Thus, with the present printer apparatus  1 , there is no fear that bubbles generated in the ink in the ink liquid chamber interfering with supply of the ink onto the heating resistors or with emission of the ink from the nozzle, thus assuring proper emission of the ink liquid droplet i from the nozzle  44   a.    
      In the printer apparatus  1  of the present invention, the ink  2  supplied to the ink liquid chamber  45  exhibits superior wettability not only for the recording paper sheet P but also for the inner peripheral surface of the ink liquid chamber  45 , paired heating resistors  42   a,    42   b  or the nozzle  44   a.  Hence, the ink  2  may promptly be supplied from the nozzle  44   a  onto the paired heating resistors  42   a,    42   b.  Thus, with the present printer apparatus  1 , the ink  2  can be quickly supplied to the paired heating resistors  42   a,    42   b  each time the ink liquid droplet i is emitted from the nozzle  44   a,  so that, even when ink liquid droplets i are emitted at short emitting intervals, these ink liquid droplets i may be properly emitted from the nozzle. That is, with the present printer apparatus  1 , the ink  2  can be adequately emitted via nozzle  44   a  at each opportunity for emission, even if the printing speed is raised, thus assuring printing to high image quality.  
      In the printer apparatus  1  of the instant embodiment, the ink  2 , accommodated in the ink cartridge  11 , at least contains the surfactant, in turn containing the organic compound represented by the above chemical formula 1. This surfactant has a cloud point as high as 80° C. which is higher than that of the conventional surfactant. Consequently, there is no fear that, when the ink  2  is heated by the paired heating resistors  42   a,    42   b,  the ink  2  is heated to a temperature higher than the cloud point of the surfactant, thus possibly affecting the physical properties of the ink. Hence, with this printer apparatus  1 , the temperature of the ink  2 , supplied from the ink cartridge  11  and contained in the ink liquid chamber  45 , scarcely exceeds the cloud point of the surfactant, with the ink  2  exhibiting stabilized physical properties. Consequently, the ink  2  may retain its wettability for the inner peripheral surface of the ink liquid chamber  45 , paired heating resistors  42   a,    42   b  or the nozzle  44   a,  such that the ink liquid droplets i may properly be emitted via nozzle  44   a.    
      In the foregoing, the head chip  27 , in which a pair of the heating resistors  42   a,    42   b  are arrayed along the transverse direction of the recording paper sheet P, has been taken as an example for explanation. However, this is not limitative of the present invention. The present invention may be applied to the head chips  91 ,  101  and  111 , shown in  FIGS. 19A  to  19 C, provided that the direction of emission of the ink liquid droplets i is controlled by varying the current values of the pulse currents supplied to the plural pressure generating devices.  
      Meanwhile, in the head chip  91 , paired heating resistors  92   a,    92   b  are juxtaposed along the traveling direction of the recording paper sheet P. In the head chip  101 , three heating resistors  103   a,    103   b  and  103   c  are arranged in the ink liquid chamber  102  and, in the head chip  111 , four heating resistors  113   a,    113   b,    113   c  and  113   d  are arranged in the ink liquid chamber  112 .  
      In  FIGS. 19A  to  19 C, the positions of the nozzles  93 ,  104  and  114  in the head chips  91 ,  101  and  111  are indicated by dotted lines. In the head chips  101 ,  111 , the heating resistors  103   c,    113   c,  provided on the ink flow duct side, are provided for preventing the situation in which the pressure for emitting the ink liquid droplet i via nozzles  104 ,  114  becomes higher on the ink flow duct side than on the sidewall side when the ink air bubbles generated in the ink liquid chambers  102 ,  112  have been broken, with the ink liquid droplet i being then emitted in a direction of supplying the ink  2  from the ink flow duct, that is, in a direction substantially opposite to the direction of arrow F in  FIGS. 19A  to  19 C.  
      In the foregoing, the head chip  27 , provided with a plural number of paired heating resistors  42   a,    42   b,  has been taken as an example for explanation. However, the present invention is not limited to this configuration and may also be applied to a configuration in which only one heating resistor  122  is provided facing a nozzle  123 , as in the case of the head chip  121  shown for example in  FIG. 20 . In this case, the head chip  121  emits the ink liquid droplet i from the nozzle  123  only in a vertically downward direction, that is, in a direction approximately normal to the recording paper sheet P. In  FIG. 20 , the position of the nozzle  123  in the head chip  121  is again indicated by a dotted line.  
      In the foregoing, a printer apparatus  1  in which the head cartridge  3  is detachably mounted to the printer main  4  and the ink cartridge  11  is detachably mounted to the head cartridge  3  is taken as an example for explanation. However, the present invention may also be applied to a printer apparatus in which the printer main  4  is unified to the head cartridge  3 .  
      In the above embodiment, an electro-thermal conversion system of emitting the ink  2 , heated by the paired heating resistors  42   a,    42   b,  is used. The present invention is not limited to this embodiment and an electro-mechanical conversion system of emitting the ink electro-mechanically by an electro-mechanical conversion element, such as a piezo-electric device or piezo-device, may also be used.  
      Furthermore, in the above embodiment, the line printer apparatus  1  is taken as an example for explanation. However, the present invention is not limited to this embodiment and may also be applied to a serial ink jet printer apparatus in which an ink head is moved in a direction approximately normal to the traveling direction of the recording paper sheet P. In this case, at least a plural number of pressure generating devices are provided to a head chip of the serial ink jet printer apparatus.  
      In the following, actually prepared samples of the ink, as the recording liquid of the present invention, will now be explained.  
      &lt;Sample 1&gt; 
      In a sample 1, 3 parts by weight of C.I. Acid Yellow 23, as a dye which proves a coloring agent, 76.95 parts by weight of water, as a solvent, 10 parts by weight of ethylene glycol, as another solvent, 10 parts by weight of diethylene glycol, as a further solvent, and 0.05 part by weight of a surfactant, containing an organic compound, represented by the chemical formula 1 where the amount of addition of ethylene oxide (k+1) was set to 1 and the amount of addition of propylene oxide (m+n) was set to 3, were mixed together to prepare an ink precursor.  
      As the surfactant, containing the organic compound, represented by the chemical formula 1:  
                 
 
 where k+1=1˜10 and m+n=2˜30, 
 
 a product manufactured by NIKKOH CHEMICALS Co. Ltd. under a trade name of NEXCOAT was used, provided, however, that the amounts of addition of propylene oxide and ethylene oxide were changed as described above. 
 
      The ink precursor, thus prepared, was heated to 60° C. and agitated for four hours. The ink precursor, thus agitated, was forcibly filtered, as the precursor was passed under pressure application through a membrane filter, with a mesh size of 0.8 μm, manufactured by ADVANTEC Inc., for preparing the ink.  
      &lt;Sample 2&gt; 
      In a sample 2, 3 parts by weight of C.I. Direct Yellow 86, as a dye which proves a coloring agent, 76 parts by weight of water, as a solvent, 10 parts by weight of diethylene glycol, as another solvent, 10 parts by weight of glycerin, as a further solvent, and 1 part by weight of a surfactant, containing an organic compound, similar to the compound used in the sample 1, and which is represented by the chemical formula 1, where the amount of addition of ethylene oxide (k+1) was set to 1 and the amount of addition of propylene oxide (m+n) was set to 4, were mixed together to prepare an ink precursor. The ink was prepared in the same way as in sample 1, except using the so prepared ink precursor.  
      &lt;Sample 3&gt; 
      In a sample 3, 2 parts by weight of C.I. Acid Red 52, as a dye which proves a coloring agent, 70 parts by weight of water, as a solvent, 10 parts by weight of triethylene glycol, as another solvent, 5 parts by weight of triethylene monobutyl ether, as a further solvent, 10 parts by weight of glycerin, as a further solvent, and 3 parts by weight of a surfactant, containing an organic compound, similar to the compound used in the sample 1, and which is represented by the chemical formula 1, where the amount of addition of ethylene oxide (k+1) was set to 1 and the amount of addition of propylene oxide (m+n) was set to 5, were mixed together to prepare an ink precursor. The ink was prepared in the same way as in sample 1, except using the so prepared ink precursor.  
      &lt;Sample 4&gt; 
      In a sample 4, 3 parts by weight of C.I. Direct Blue 199, as a dye which proves a coloring agent, 81 parts by weight of water, as a solvent, 5 parts by weight of 1,2-propane diol, as another solvent, 5 parts by weight of diethylene glycol, as a further solvent, 5 parts by weight of 2-pyrrolidone, as a further solvent, and 1 part by weight of a surfactant, containing an organic compound, similar to the compound used in the sample 1, and which is represented by the chemical formula 1, where the amount of addition of ethylene oxide (k+1) was set to 2 and the amount of addition of propylene oxide (m+n) was set to 6, were mixed together to prepare an ink precursor. The ink was prepared in the same way as in sample 1, except using the so prepared ink precursor.  
      &lt;Sample 5&gt; 
      In a sample 5, 4 parts by weight of C.I. Direct Black 154, as a dye which proves a coloring agent, 70.5 parts by weight of water, as a solvent, 5 parts by weight of ethylene glycol, as another solvent, 10 parts by weight of glycerin, as a further solvent, 0.5 part by weight of triethanolamine, as a further solvent, and 5 parts by weight of a surfactant, containing an organic compound, similar to the compound used in the sample 1, and which is represented by the chemical formula 1, where the amount of addition of ethylene oxide (k+1) was set to 4 and the amount of addition of propylene oxide (m+n) was set to 9, were mixed together to prepare an ink precursor. The ink was prepared in the same way as in sample 1, except using the so prepared ink precursor.  
      &lt;Sample 6&gt; 
      In a sample 6, 3 parts by weight of C.I. Direct Blue 87, as a dye which proves a coloring agent, 75.5 parts by weight of water, as a solvent, 5 parts by weight of 1,3-butane diol, as another solvent, 10 parts by weight of triethylene glycol, as a further solvent, 5 parts by weight of glycerin, as a further solvent, 1 part by weight of a surfactant, containing an organic compound, similar to the compound used in sample 1, and which is represented by the chemical formula 1, where the amount of addition of ethylene oxide (k+1) was set to 1 and the amount of addition of propylene oxide (m+n) was set to 4, and 0.5 part by weight of a surfactant containing an organic compound represented by the chemical formula 2:  
                 
 
 where o+p is an integer not less than two, 
 
 were mixed together to prepare an ink precursor. It is noted that the amount of addition of ethylene oxide (o+p) in the above chemical formula 2 was set to 2. The ink was prepared in the same way as in sample 1, except using this ink precursor. 
 
 &lt;Sample 7&gt;
 
      In a sample 7, 5 parts by weight of C.I. Direct Black 168, as a dye which proves a coloring agent, 64.5 parts by weight of water, as a solvent, 10 parts by weight of triethylene glycol, as another solvent, 20 parts by weight of glycerin, as a further solvent, and 0.5 part by weight of a surfactant, containing an organic compound, similar to the compound used in the sample 1, and which is represented by the chemical formula 1, where the amount of addition of ethylene oxide (k+1) was set to 1 and the amount of addition of propylene oxide (m+n) was set to 3, were mixed together to prepare an ink precursor. The ink was prepared in the same way as in sample 1, except using the so prepared ink precursor.  
      &lt;Sample 8&gt; 
      In a sample 8, 4 parts by weight of C.I. Direct Blue 199, as a dye which proves a coloring agent, 65 parts by weight of water, as a solvent, 10 parts by weight of ethylene glycol, as another solvent, 10 parts by weight of diethylene glycol, as a further solvent, 10 parts by weight of triethylene glycol, as a further solvent, and 1 part by weight of polyoxyethylene nonylphenylether, manufactured by NIKKOH CHEMICALS Co. Ltd. under the trade name of NP10, as a surfactant, were mixed together to prepare an ink precursor. The ink was prepared in the same way as in sample 1, except using the so prepared ink precursor.  
      &lt;Sample 9&gt; 
      In a sample 9, 3 parts by weight of C.I. Direct Blue 168, as a dye which proves a coloring agent, 76.9 parts by weight of water, as a solvent, 5 parts by weight of 1,2-propanediol, as another solvent, 5 parts by weight of 2-pyrrolidone, as a further solvent, 10 parts by weight of glycerin, as a further solvent, and 0.1 part by weight of polyoxyethylene nonylphenylether, manufactured by NIKKOH CHEMICALS Co. Ltd. under the trade name of NP7.5, as a surfactant, were mixed together to prepare an ink precursor. The ink was prepared in the same way as in sample 1, except using the so prepared ink precursor.  
      &lt;Sample 10&gt; 
      In a sample 10, 3 parts by weight of C.I. Acid Red 52, as a dye which proves a coloring agent, 71 parts by weight of water, as a solvent, 10 parts by weight of monobutyl triethylene glycol, as another solvent, 5 parts by weight of 2-pyrrolidone, as a further solvent, 10 parts by weight of glycerin, as a further solvent, and 1 part by weight of polyoxyethylene tridecyl alcohol ether, manufactured by NIPPON YUSHI Co. Ltd. under the trade name of DispanolTOC, as a surfactant, were mixed together to prepare an ink precursor. The ink was prepared in the same way as in sample 1, except using the so prepared ink precursor.  
      &lt;Sample 11&gt; 
      In a sample 11, 3 parts by weight of C.I. Direct Yellow 132, as a dye which proves a coloring agent, 74.5 parts by weight of water, as a solvent, 10 parts by weight of diethylene glycol, as another solvent, 10 parts by weight of tetraethylene glycol, as a further solvent, 0.5 part by weight of triethanolamine, as a further solvent, and 2 parts by weight of polyoxyethylene oleyl ether, manufactured by NIPPON YUSHI Co. Ltd. under the trade name of NonionE-215, as a surfactant, were mixed together to prepare an ink precursor. The ink was prepared in the same way as in sample 1, except using the so prepared ink precursor.  
      &lt;Sample 12&gt; 
      In a sample 12, 3 parts by weight of C.I. Acid Red 289, as a dye which proves a coloring agent, 52 parts by weight of water, as a solvent, 10 parts by weight of ethylene glycol, as another solvent, 20 parts by weight of diethylene glycol, as a further solvent, 10 part by weight of glycerin, as a further solvent, and 5 part by weight of polyoxyethylene nonyl phenyl ether, manufactured by NIKKOH CHEMICALS Co. Ltd. under the trade name of NP7.5, as a surfactant, were mixed together to prepare an ink precursor. The ink was prepared in the same way as in sample 1, except using the so prepared ink precursor.  
      &lt;Sample 13&gt; 
      In a sample 13, 4 parts by weight of C.I. Direct Black 154, as a dye which proves a coloring agent, 75.95 parts by weight of water, as a solvent, 5 parts by weight of ethylene glycol, as another solvent, 5 parts by weight of diethylene glycol, as a further solvent, 10 part by weight of glycerin, as a further solvent, and 0.05 part by weight of polyoxyethylene alkyl ether, manufactured by NIKKOH CHEMICALS Co. Ltd. under the trade name of BT9, as a surfactant, were mixed together to prepare an ink precursor. The ink was prepared in the same way as in sample 1, except using the so prepared ink precursor.  
      Of the inks of the samples 1 to 13, prepared as described above, the surface tension and the viscosity were measured. The surface tension was measured using an automatic surface tensimeter, manufactured by KYOWA KAIMEN KAGAKU-SHA under a trade name of CBVP-Z, whilst the viscosity was measured using a viscometer manufactured by KYOWA KAIMEN KAGAKU-SHA under a trade name of VM-100A.  
      The measured results of the surface tension and viscosity of the samples 1 to 13 are shown in Table 1 below.  
                           TABLE 1                                   Surface Tension (mN/m)   Viscosity (mPas)                                                        Sample 1   45.4   3.66           Sample 2   32.9   2.14           Sample 3   33.2   3.23           Sample 4   32.2   2.01           Sample 5   38.0   3.46           Sample 6   30.6   2.55           Sample 7   35.7   8.9           Sample 8   32.1   3.48           Sample 9   36.3   2.50           Sample 10   31.5   3.03           Sample 11   40.5   2.92           sample 12   31.2   6.55           Sample 13   47.3   2.33                      
 
      It is seen from the results shown in Table 1 that, with the samples 1 to 13, the values of surface tension are in a range between 30 mN/m and 47 mN/m, while those of the viscosity are in a range between 2 mPas and 9 mPas, there being no marked difference among the values of the surface tension and among the values of the viscosity.  
      Using an ink jet printer, with a nozzle diameter of 20 μm and a resistance value of the heating resistors of 135Ω, having a head chip with 24 nozzles, printing of alphabetical letters and all-over printing were carried out on PPC paper sheets manufactured by XEROX Inc., regenerated paper sheets, manufactured by HONSHUU SEISKH C.Ltd., and on bond paper sheets, manufactured by MEAD Inc., by driving the head chip with a driving voltage of I IV, and evaluation was made of the quality of printed letters, ink fixing performance and frequency response. The all-over printing was carried out by daubing preset areas of the printing paper sheets used.  
      The results of evaluation of the quality of printed letters, ink fixing performance and frequency response of the samples 1 to 13 are indicated in the Table 2 below.  
                               TABLE 2                                              Evaluation of           Evaluation of   Evaluation   Frequency Response                                         Printing Quality   of Ink Fixing   1 kHz   3 kHz   10 kHz                                                 Sample 1   ◯   ◯   ⊚   ⊚   ◯       Sample 2   ◯   ⊚   ⊚   ⊚   ⊚       Sample 3   ◯   ⊚   ⊚   ⊚   ⊚       Sample 4   ◯   ⊚   ⊚   ⊚   ⊚       Sample 5   ◯   ◯   ⊚   ⊚   ◯       Sample 6   ◯   ⊚   ⊚   ⊚   ⊚       Sample 7   ◯   ◯   ⊚   ◯   ◯       Sample 8   Δ   Δ   Δ   X   X       Sample 9   Δ   Δ   Δ   X   X       Sample 10   X   Δ   X   X   X       Sample 11   X   X   X   X   X       Sample 12   X   ◯   Δ   X   X       Sample 13   X   X   Δ   X   X                  
 
      The printing quality for alphabetical letters was evaluated by visually inspecting the letters printed on the above three sorts of paper sheets. In the above Table 2, a symbol ◯ indicates that no bleeding is observed in the evaluation of the quality of printed letters. A symbol Δ indicates that, while bleeding is observed, letters can be recognized. A symbol × indicates that bleeding is so severe that printed letters are hardly recognizable.  
      The ink fixing was evaluated by scrubbing the letters, printed on the PPC paper sheets, manufactured by XEROX Inc., with an emery paper sheet manufactured by TOYO KAGAKU SANGYO-SHA (trade name: No.5C). For evaluation, the scrubbed part was visually checked as to whether or not the printed letters were blurred.  
      As for evaluation of ink fixing in Table 2, a mark ⊚ indicates that blurring occurred in five seconds, a mark ◯ indicates that blurring occurred in ten seconds, a mark Δ indicates that blurring occurred in fifteen seconds, and a mark × indicates that blurring occurred in thirty seconds. As for evaluation of frequency response, letter printing and all-over printing were carried out on the above three sorts of the printing paper sheets, with the frequency of the driving voltage set to 1 kHz, 3 kHz and 10 kHz, and the possible presence of blurred zones or unprinted zones where no ink liquid droplet i was deposited (so-called open zones) was checked for evaluation.  
      In the evaluation of frequency response in Table 2, a mark ⊚ indicates that there are observed blurring or open spots in neither the letter printing nor all-over printing, a mark ◯ indicates that blurring is observed in only the all-over printing, a mark Δ indicates that blurring and open spots are seen in only all-over printing, and a mark × indicates that blurring and open spots are seen in both the letter printing and all-over printing.  
      If the head chip is supplied with the driving voltage of the frequency of 1 kHz, the head chip is driven at an ink emitting interval such that ink liquid droplets are emitted at a rate of say 1000 times per second. If the head chip is supplied with the driving voltage of the frequency of 3 kHz or with the driving voltage of the frequency of 10 kHz, the head chip is driven at an ink emitting interval such that ink liquid droplets are emitted at a rate of say 3000 times per second or at an ink emitting interval such that ink liquid droplets are emitted at a rate of say 10000 times per second, respectively.  
      It is seen from the results of evaluation shown in Table 2 that, as compared to the samples 8 to 13 not containing surfactants containing organic compound shown by the chemical formula 1, the samples 1 to 7 are not different significantly as to surface tension or viscosity, while being superior to the samples 8 to 13 as to the quality of printed letters, ink fixing and frequency response.  
      The samples 1 to 7, each containing surfactant at least containing organic compounds represented by the chemical formula 1, exhibit the high degree of wettability with respect to respective paper sheets, such as PPC paper sheets, regenerated paper sheets or bond paper sheets. That is, the inks of these samples are penetrated quickly in the direction along the thickness of the recording paper sheet to present an appearance as if the ink has been dried. Consequently, with the samples 1 to 7, high-quality letter printing or all-over printing free of bleeding or blurring may be achieved.  
      Moreover, the samples 1 to 7 exhibit superior wettability not only for recording paper sheets but also for the head chip, such that the ink may be supplied promptly on the heating resistor the instant the ink liquid droplet i is emitted from the nozzle. Hence, the ink liquid droplet i may properly be emitted from the nozzle, each time the ink liquid droplet is to be emitted, even if the emission interval is reduced, with the result that high-quality letter printing or all-over printing may be achieved in a manner free from blurring or open spots.  
      The samples 8 to 13, not containing the surfactant having an organic compound shown by the chemical formula 1, are inferior to the samples 1 to 7 in wettability with respect to the recording paper sheet P. Thus, the ink liquid droplet on deposition on the recording paper sheet is not dried quickly, and is susceptible to bleeding or blurring, thereby lowering the printing quality.  
      On the other hand, the samples 8 to 13 are inferior to the samples 1 to 7 as to wettability with respect to the head chip, such that the ink cannot be delivered quickly to the heating resistor after emitting the ink liquid droplet i from the nozzle. Thus, with these samples 8 to 13, the shorter the interval for ink emission, that is, the higher the frequency of the driving voltage, the more difficult it becomes to emit the ink liquid droplet from the nozzle, each time the ink liquid droplet is to be emitted from the nozzle. Hence, blurred or open spots are produced to lower the printing quality.  
      It is seen from above that, for preparing the ink with high printing quality as well as excellent ink fixing properties and frequency response, it is crucial that the surfactant, at least containing the organic compound having the chemical formula 1, shall be contained in the ink.  
      The present invention is not limited to the embodiments explained above with reference to the drawings and a variety of changes or substitutions by equivalents may be attempted by those skilled in the art without departing from the scope of the invention as defined in the appended claims.