Method of forming image and apparatus of the same

Abstract: In ink-jet printing, in order to improve fixation without using a means such as a heater, etc. even in the case of using an ink with a slow penetration speed, black ink discharged from one head (101Bk) is made to be relatively low penetrative, while a processing solution, which is discharged from the other head (101S) and insolubilize dye of the above black ink, is made to be relatively high penetrative. When characters, etc. are printed on recording paper (103), the black ink and the processing solution thus coalesce on the recording paper (103), and the penetrability of the mixed solution becomes a given level or higher, and this permits to accelerate the penetration and fixation.

Description: This invention relates to a method for forming an image and an apparatus for forming the same, and for example to fixing technology in a case of forming an image by using ink and a processing solution to insolubilize the ink. In ink-jet printing technology for performing printing by using solution such as this kind of ink, etc., fixation of the ink after printing is one of important subjects. If the fixation is poor, there is a fear of inconvenience in handling printed matters output from a printer or a fear of staining overlying other printed matters when they are stacked for being put into storage. As a means for improving such fixing, an accelerator to evaporate solvent such as water content in the ink, etc. by using a heating means such as a heater or the like is known. The use of such a heating means permits an across-the-board or better improvement in fixation of ink with any penetrable speed from a high penetrability to a low penetrability. However, in an arrangement of using a heater, a total power consumption of a printer becomes relatively high. Especially, when the higher speed printing is aimed at, the shorter time is required for fixing and the more heat quantity has to be supplied, and this results also in a specially large power consumption. Further, heating by heater is performed to a printing medium during feeding or conveyance, but if the heater is arranged along the conveyance path, a printer is upsized the more and this is not always a suitable arrangement from a down-sizing point of view for the equipment. As opposed to this, it is also known that an ink with a high penetrability is used and fixation of the ink itself is thereby improved. The embodiments of the present invention seek to solve at least one of the following problems. Namely, they are : to provide a new image-forming technology, to improve fixation without using a means such as a heater, etc. even when an ink with a slow penetrability is used, and to rapidly fix an ink containing a color material such as black, etc. while achieving a high optical density. EP-A-0767224 proposes an ink composition for link jet recording comprising a colourant, an alginate, a liquid wetting agent, a penetrant, and water, in which the liquid wetting agent contains at least 8% by weight of the total ink composition of glycerine. The penetrant may be a surface active agent, such as an alkyl substituted acetylene glycol having ethylene oxide insertions in the hydroxyl groups. One example is 2,4,7,9-tetramethyl-5-decyne-4,7-diol. The surface active agent may be present in a concentration of not less than the critical micelle concentration. The colourant may be a dye containing a carboxylic acid group or carboxylate group, either singly or in combination with a dye and/or pigment free of carboxylic acid or carboxylate group. EP-A-0583096 discloses a water based ink for ink jet recording containing a surfactant in an amount lower than the critical micelle concentration of the surfactant in the ink but higher than the critical micelle concentration of the surfactant in purified water. The surfactant may be 2,4,7,9-tetramethyl-5-decyne-4,7-diol with ethylene oxide additions to the hydroxyl groups (trade name: Acetylenol EH). The inks may contain dyes or pigments. In both EP-A-0767224 and EP-A-0583096, the surface active agent is stated to increase the penetration ability of the ink. It is known, e.g. from EP-A-0791470 and EP-A-0726157, to print, one on top of the other, a drop of ink and a drop of a processing liquid for making the colouring material of the ink insoluble or coherent. According to the present invention there are provided methods of forming an image as set out in claims 1, 4 and 6, and image forming apparatuses as set out in claims 21, 24 and 26. Optional features are set out in the remaining claims. According to the above arrangement, a critical micelle concentration, a surface tension, and Ka value, which represent a penetrability of a droplet formed on the surface of the printing medium by the coalescing of different plural droplets such as those of ink, processing solution, etc., have predetermined values or differ therefrom in the direction of higher penetrability. Therefore, even if some of the individual droplets have a low penetrability, the penetration of the joined (coalesced) droplets is accelerated. Thus, even if ink of a low penetrability is used for improving optical density value (OD value) or suppressing feathering, the coalesced mixture has a high penetrability and the fixation is not inhibited. There now follows a description of embodiments of the invention in conjunction with the accompanying drawings. Fig. 1 is a chart showing a relationship between a concentration of acetylenol contained in an ink, etc. and a fixing time to a printing medium such as the ink, etc.; Fig. 2 is a chart showing a relationship between a content rate of acetylenol and Ka-value representing a penetration speed; Fig. 3A and 3B are characteristic curves showing relationships between a penetration quantity and a lapse of time; Fig. 4 is a chart showing a relationship between a content rate of acetylenol and surface tension; Fig. 5 is a cross-sectional view showing a schematic arrangement of an ink-jet printer related to an embodiment in accordance with the present invention; Fig. 6 is a block diagram showing an example of a control system arrangement of the above-mentioned ink-jet printer; Fig. 7 is a cross-sectional view showing a schematic arrangement of an ink-jet printer related to another embodiment in accordance with the present invention; and Fig. 8 is a perspective illustration showing an arrangement of an ink-jet printer related to further embodiment in accordance with the present invention. The embodiments in accordance with the present invention have been obtained as the results of the experiments or analyses by the inventor of the present invention. When printing was carried out in a black (Bk) ink on a sheet of ordinary paper and the behavior was observed, an ink with a slow penetration almost kept staying in a state of droplet on the paper in spite of the lapse of time, however, as soon as printing had been done in droplet with a high penetrability superimposed on the former printing, the two kinds of solution mixed together, and penetrated in the paper within a relatively short time. Various solutions with high penetrabilities were provided by admixing various concentrations of nonionic surface-active agent such an ethylenoxide-2,4,7,9-tetramethyl-5-decyne-4,7-diol (hereinafter also called "acetylenol" (brand name) manufactured by Kawaken Fine, Chemical Co., Ltd.), and these solutions were printed on to BK ink solid printed image, and fixing time was measured. In this case, when analysis was made by varying a discharge volume of Bk ink and that of high penetrability solution printed over it, then, the fixing time was about the same as that for discharging the result of pre-mixing Bk ink and a high penetrability solution in the same volumes as were discharged separately in the above. Namely, it is presumed that when they were discharged separately, the two kinds of the solutions were mixed immediately and changed into one solution which had a uniform and approximately the same penetrability as a previously formed mixture of them, and this penetrated the paper. Here, a further study showed as shown in Fig. 1 that when mixed solutions of various concentrations of acetylenol were added onto paper A with relatively poor fixation and paper B with relatively good fixation, fixation is steeply speeded up at a concentration of 0.7% or higher which is the critical micell concentration of water, as illustrated by a solid line and a broken line. In this case, paper A had a fixing time of about 1 second or less, while paper B had 0.5 seconds or less. Namely, the inventor of the present invention has originated a new idea of forming an image not by one droplet image forming but by different plural droplets forming a compound ink on a printing medium. Namely, this is a method of image forming in which the concentration of a surface active agent in the compound ink droplets is equal to a critical micell concentration to pure water or higher. Furthermore, the inventor of the present invention takes notice of ink in ink-jet printing technology wherein one dot is generally formed from a plurality of ink droplets and intends to positively make use of this method to control the penetrability of a mixed solution compounded and finally obtained. As being obvious from the above, an embodiment of the present invention is to use a plurality of different kinds of solutions, to mix them on a printing medium, and to make the mixed solution have a predetermined penetrability or higher. In more detail, each of a plurality of the above-mentioned solutions to be mixed may basically, have arbitrary penetrability and has only to reveal a predetermined penetrability or higher when they are compounded into one mixed solution. For example, some kinds of the solutions to be mixed may have the above predetermined penetrability or lower one, and the other kinds of the solutions may reveal the above predetermined penetrability or higher one. Here, concerning "kind" of a solution in this specification, it is defined as being "different kind" when components or, more widely, characteristics are different from each other. For example, processing solution to insolubilize an ink and its color material, pigment ink and dye ink among inks, further, ink containing dispersing agent (hereinafter called "pigment ink with dispersing agent"), and self-dispersing type ink containing no dispersing agent (hereinafter called "ink without dispersing agent", respectively, may comprise each solution to be mixed in accordance with this embodiment. Further, different color inks and inks containing different components may comprise the above-mentioned solutions to be mixed, respectively. Furthermore, an ink containing pigment and less component ratio of dye, and reversely, an ink containing dye and a less component ratio of pigment may also comprise each of the above-mentioned solutions to be mixed ; respectively. Penetrability mentioned in this specification will briefly be described in the following. When penetrability is expressed by an ink volume per m 2 , it is known that a penetration amount of ink (a unit : ml/m 2 = µm) can be expressed by Bristow's formula as shown below. [Formula 1 :] V = Vr + Ka(t-tw) 1/2 wherein, Lt > tw Immediately after droplets of ink have landed on a surface of a printing medium, the droplets of ink are mostly absorbed in rugged part on the surface (rugged part on the surface of the printing medium), and little is permeated into the printing medium. This penetration time is expressed by tw (a wet time) and an absorption volume in the rugged part is expressed by Vr. When the lapse of time after deposition of the droplets of the ink exceeds tw, penetration volume is increased in proportion to the square root of the additional time (t - tw). Ka is a proportional factor of this increment and shows a value according to a penetration speed. Fig. 2 shows values of the proportional factor Ka to content ratios of acetylenol in an ink obtained by experiments. Ka values were measured by using a solution dynamic penetrability measuring device S (made by Toyo Seiki Seisakusho) in accordance with Bristow method. In these experiments, PB paper of Canon Co., Ltd., who is the applicant of the present invention, was used as a printing medium (recording paper). This PB paper is usable not only for a copier or a laser beam printer (LBP) using an electro-photographic method, but also for printing using an ink-jet recording method. Further, a similar result could be obtained also to PPC paper, an electro-photographic paper of Canon Co., Ltd. Fig. 2 shows a curve on which Ka values are increasing (ordinate of axis) with increasing content rates (axis of abscissa). The proportional factor Ka is determined by the content percentage of acetylenol. Consequently, a penetration speed of ink substantially depends on a content rate of acetylenol. Further, the line segments crossing the curve and in parallel with the ordinate of axis show ranges of dispersions of the measurement results. Fig. 3 shows a characteristic curves of a relationship between penetration quantity of ink and penetration speed and shows results of the experiments on a recording paper of 64g/m 2 weight, about 80 µm thickness and about 50% percentage of voids. In Fig. 3A, the abscissa represents square root of the lapse of time t (msec 1/2 ), and in Fig. 3B, the abscissa represents the lapse of time t (msec). Further, in both figures, the ordinate represents penetration amount (µm), and curves are in the case of 0%, 0.35% and 1% acetylenol content, respectively. As being obvious from both figures, the more the acetylenol content is, the more becomes the penetration amount of ink for a given lapse of time, namely, the higher the penetrability is. In the graphics shown in Fig. 3, such an tendency can be seen that the higher the content of acetylenol is, the shorter the wet time tw becomes, and also, the higher the content rate of acetylenol is, the higher the penetrability is, even during the time before reaching tw. In the case of an ink containing no acetylenol (content rate is 0%), the ink is a low or poor permeable ink. Further, in the case that acetylenol is mixed in a rate of 1% content, the ink has a property of permeating into recording paper in a short time and has property as a high permeable ink which will be specified later. And, the ink mixed with 0.35% content of acetylenol has a property of an intermediate, semi-permeable ink between the two. Ka value (ml/m 2 ·msec 1/2 ) Acetylenol content (%) Surface tension (dyne/cm) Poor permeable ink less the 1.0 less than 0.2 40 or larger Semi-permeable ink 1.0 or more but less than 5.0 0.2 or more but less than 0.7 35 or larger but smaller than 40 High-permeable ink 5.0 or more 0.7 or more smaller than 35 The above-mentioned table 1 shows Ka values, acetylenol contents (%), and surface tensions (dyne/cm) to "poor permeable ink", "semi-permeable ink", and "high permeable ink" , respectively. The higher Ka value is, the higher the penetrability of each ink to recording paper as a printing medium becomes. Namely, the smaller the surface tension is, the higher the penetrability is. The Ka values in Table 1 were, as described above, obtained from the measurements by using a solution dynamic penetrability test device S (made by Toyo Seiki Seisakusho) in accordance with Bristow method. In the experiments, said PB paper of Canon Co., Ltd. was used as recording paper. Further, similar results could be obtained on PPC paper of said Canon Co., Ltd. Here, the ink specified as "high permeable ink" has 0.7 % or more content of acetylenol and this is in the range of penetrability in which the excellent result could be obtained as described above. Here, it is known that as a condition for containing a surface active agent in a solution, there is a critical micell concentration (hereinafter also called " CMC ") of the surface active agent for the solution. This critical micell concentration is the concentration at which, when the concentration of a surface active agent solution is increasing, tens of molecules suddenly associate with each other to form a micell. Acetylenol contained in the above-described ink for preparing penetrability is a kind of surface active agent, and a critical micell concentration exists for acetylenol according to the solution. Fig. 4 is a characteristic curve showing a relationship with surface tension when the content rate of acetylenol to water was varied. Since there is no reduction in the surface tension once micells are formed, it is apparent from the figure that the critical micell concentration of acetylenol to pure water is about 0.7%. And, comparing the CMC shown by the figure with the above Table 1, it is apparent that the "high penetrable ink" contains acetylenol at its CMC to pure water or higher. Based on the above definition of penetrability, etc., several embodiments in accordance with the present invention will be described below. Embodiment 1 This embodiment is to perform printing by using an ink containing a predetermined color material such as dye or pigment, etc. and a processing solution to make this color material insoluble. Namely, by discharging the above-mentioned ink first and then discharging the processing solution onto it, a coalescent mixed solution is formed on a printing medium, and the concentration of the surface active agent in the solution is the CMC of the surface active agent to pure water or higher. Thus, a high OD value is obtained as a result of the printing, and further, a high speed fixing is achieved. Moreover, in the case of the above, it is also possible to suppress feathering and print sharper dot edges by making the penetrability of ink itself lower while maintaining the concentration of the above surface-active agent in the coalescent mixed solution. Further, when black (Bk) dye or Bk pigment is used for a color material of the above-mentioned ink, it becomes possible to print characters, etc. with less feathering, high OD value, and excellent printing quality. Moreover, regarding the pigment ink and dye ink in the above explanation, as described above, a minority component of dye or pigment, respectively, may be contained in the respective pigment ink or dye ink. This is the same with the other embodiments which will be described below. From this view point, an ink containing only dye and an ink partly containing pigment in the dye are defined as "an ink mainly with dye ", while an ink containing only pigment and an ink partly containing dye in the pigment are defined as " an ink mainly with pigment." Embodiment 2 In this embodiment, two kinds of ink such as dye ink and pigment ink are prepared, and by making them coalescent on a printing medium and then adding a processing solution thereon, a mixture of three kinds of solutions is obtained. The concentration of the surface active agent in this mixed solution is arranged to be the CMC of the surface active agent to water or higher. According to this embodiment, as the above-described embodiment 1, it becomes possible to suppress feathering and print with high OD, while achieving a high speed fixing, and furthermore, it is possible to produce an effect that a respective problem arising with pigment ink or with dye ink can be solved or reduced when both pigment ink and dye ink, and a processing solution, are used for printing. Namely, when only pigment ink and processing solution are used, a relatively strong cohesive force of the pigment generated by a reaction with the processing solution may cause cracks or the like to occur in the fixed color agent. However, in the case of this embodiment, high viscosity reactant of the dye being reacted with the processing solution at the same time fills the cracks so that they are not visible. On the other hand, when only dye ink and processing solution are used, it is possible to improve OD value by keeping the reactants of the processing solution and the dye remaining relatively on the outer layer of the printing medium, however, an increases in OD value is not expectable in many cases depending on the characteristic of the dye itself. In the case of this embodiment, however, the inventor of the present invention has confirmed an effect that OD value becomes higher, presumably by an action, such as that the dye reactants, reacted with the processing solution, incorporate cohesive substances to become relatively large particles, and thus, more particles of pigment remain on the outer layer of the printing medium. Moreover, regarding order of putting dye ink and pigment ink, any order produces the effect described above. Embodiment 3 In this embodiment, an ink, containing both dye and pigment, and a processing solution are made coalescent on a printing medium, and the concentration of the surface active agent of the coalescent mixture is the CMC of the surface active agent to water or higher. In this case, it is possible to produce the same effect as that in the embodiment 2 described above, wherein the dye ink and the pigment ink were output individually. Embodiment 4 This embodiment replaces the pigment ink in the above embodiment 2 with an ink without dispersing agent. In this case, in addition to the effect common to the embodiments in accordance with the present invention and the effect in the embodiment 2 described above, it becomes possible to suppress "seepage" of fine reacted particles of cohesive substances that are generated when an ink without dispersing agent and a processing solution are used. In the case of this embodiment, the applicant of the present invention assumes that this is because the high viscosity substances of the simultaneously reacted dye absorb the above-mentioned particles to suppress the "seepage". Embodiment 5 This embodiment corresponds to a case wherein an ink mixed with dye and pigment beforehand does not contain dispersing agent for the pigment in the embodiment 3. In this case, an effect similar to that in the embodiment 4 can be obtained. Embodiment 6 This embodiment relates to the order of outputting ink and processing solution, and combinations of each ink and processing solution are applicable to this embodiment. For example, when printing is performed by using three droplets of dye ink, ink without dispersing agent, and processing solution, the inks or the processing solution are output in order of dye ink, processing solution, and ink without dispersing agent, or in order of ink without dispersing agent, processing solution, and dye ink. Namely, the processing solution is added between the two inks, and they are mixed on the printing medium to make the concentration of the surface active agent in their mixed solution become the CMC of the surface active agent or higher. In this case, it becomes possible to perform high quality printing with relatively high OD value and suppressed feathering. The following are the descriptions of detailed examples of the image-forming apparatus to which the above embodiments are applicable. Example 1 Fig. 5 is a cross sectional view showing schematic configuration of a full line type printer relating to the example 1. This printer 1 adopts an ink-jet printing system to perform printing by discharging or ejecting ink or processing solution from a plurality of full line type printing heads arranged at predetermined positions along a conveying or feeding direction of a recording medium as a printing medium, and operates by being controlled by the control circuit in Fig. 6 which will be described later. Each of the printing heads 101Bk, 101S, 101C, 101M, and 101Y of a head group 101g has about 7200 ink discharging portions or nozzles arrayed in the width direction (perpendicular to this figure) of the recording paper conveyed in the direction of arrow A in the figure, and can operate printing on a recording paper up to the size A3. These heads make use of thermal energy to generate bubbles in the ink, etc. and discharge the ink or the processing solution by the pressure of the bubbles. The recording paper 103 is conveyed in the direction of arrow A by means of a pair of resist rollers 114 driyen by a conveyor or feed motor, and is guided by a pair of guide plates 115 and is conveyed onto a conveyor belt 111 after registration of the tip edge of the paper. The endless conveyor belt 111 is borne by two rollers 112, 113, and a vertical deviation on the upper part of the belt is restricted by a platen 104. The roller 113 is driven to rotate and the recording paper 103 is thereby conveyed. Moreover, the recording paper 103 is held on the conveyor belt 111 by means of electrostatically. The roller 113 is driven to rotate in the direction of conveying the recording paper in the direction of the arrow A. The recording paper 103 printed thereon by the printing head group 101g is ejected onto a storage tray 116. Each head of the recording head group 101g comprised of the black dye ink head 101Bk, the processing solution head 101S for discharging the processing solution, each color ink head (a cyan head 101C, a magenta head 101M, and a yellow head 101Y) is arranged along the conveying direction A of the recording paper 103 as shown in the figure. Here, the discharging nozzle of the black dye ink head 101Bk has a discharging amount of 30pl, and that of each of the other heads has a discharging amount of 15pl. It becomes possible to print black characters and colored images by discharging each color of ink and the processing solution from the respective printing heads. Fig. 6 is a block diagram showing a control configuration of the full line type printer 1 illustrated in Fig. 5 A system controller 201 has a micro processor, a ROM for storing a control program executed in this printing apparatus, a RAM used as a work area when the micro processor operates processing, etc., and executes the control of the entire printing apparatus. A motor 204 is controlled in the driving via a driver 202, and rotates the roller 113 shown in Fig. 5 to convey the recording paper. A host computer 206 transfers information to be printed to the printer 1 in accordance with this example, and controls its printing operation. A receiving buffer 207 temporarily stores data from the host computer 206 to keep them therein until a system controller 201 reads the data. A frame memory 208 is a memory for expanding printing data into image data, and has an enough size of memory for printing. This example is described assuming that the frame memory 208 has a memory capacity permitting to store data for a sheet of recording paper, however, the present invention is not to be restricted by a capacity of the frame memory. Buffers 209S, 209P are for temporarily storing data to be printed, and their memory capacities are variable depending on the number of the nozzles of the printing heads. A printing control part 210 is for properly controlling drives of the printing heads according to the instructions from the system controller 201, and controls a driving frequency, the number of printing data, etc., and also creates data for making the processing solution to be discharged. A driver 211 drives a head part 212S which is the printing head 101S for discharging the processing solution and a head part 212P including the printing heads 101Bk, 101C, 101M, 101Y for discharging each ink, and is controlled according to signal from the printing control part 201. In the above configuration, the printing data are transferred from the host computer 206 to the receiving buffer 207 for being temporarily stored therein. Next, the stored printing data are read by the system controller 201 and expanded to the buffers 209S, 209P. Further, it is possible to detect paper-jamming, ink-exhaustion, paper-out, etc. by means of each detection signal from abnormality detection sensors. The printing control part 210 creates data for the processing solution for discharging it, based on the image data expanded to the buffers 209S, 209P, and controls printing actions of each printing head based on the printing data in each buffer 209S, 209P and the data for the processing solution. In this example, a low penetration speed ink, namely, poor permeable ink shown in Table 1, is used for the black dye ink to be discharged from the head 101Bk, and each high penetration speed processing solution and ink, namely, the high penetrability ink shown in Table 1 is used for each of the processing solution, cyan ink, magenta ink and yellow ink discharged from the heads 1025, 101C, 101M, 101Y. Compositions of the processing solutions and each ink used in this example are as the following. Here, the contents shown below are indicated by pts. wt. [processing solution] Glycerin 7 pts. wt. Diethylene glycol 5 pts. wt. Acetylenol EH 2.1 pts. wt. (made by Kawaken Fine Chemical Co., Ltd.) Poly-allylamine 4 pts. wt. (molecular weight: 1500 or less, mean molecular weight: about 1000) acetic acid 4 pts. wt. Benzalkonium chloride 0.5 pts. wt. Tri-ethylene glycol mono-butyl ether 3 pts. wt. Water Remainder [Yellow (Y) ink] C. I. Direct yellow 86 3 pts. wt. Glycerin 5 pts. wt. Diethylene glycol 5 pts. wt. Acetylenol EH 1 pts. wt. (made by Kawaken Fine Chemical Co., Ltd.) Water Remainder [Magenta (M) ink] C. I. Acid red 3 pts. wt. Glycerin 5 pts. wt. Diethylene glycol 5 pts. wt. Acetylenol EH 1 pts. wt. (made by Kawaken Fine Chemical Co., Ltd.) Water Remainder [Cyan (C) ink] C. I. Direct Blue 199 3 pts. wt. Glycerin 5 pts. wt. Diethylene glycol 5 pts. wt. Acetylenol EH 1 pts. wt. (made by Kawaken Fine Chemical Co., Ltd.) Water Remainder [Black (Bk) dye ink] Food Black 2 4 pts. wt. Glycerin 7.5 pts. wt. Diethylene glycol 7.5 pts. wt. Urea 7.5 pts. wt. Water Remainder In the example, the nozzles of each printing head are arrayed at a concentration of 600dpi (dots per inch), and further, operates printing at a concentration of 600dpi in the direction of the recording paper conveyance. Thus, the dot concentration of an image, etc. printed in accordance with this example is 600dpi in both row and column directions. Further, since the discharging frequency of each head is 4 kHz, the conveyance speed of the recording paper is about 170 mm/sec. Moreover, a distance Di (refer to Fig. 5) between the black dye ink head 101Bk and the processing solution head 101S is 40 mm, therefore, it takes about 0.24 sec from discharging of the black dye ink on a position until discharging of the processing solution on the position. In the above configuration, 30 pl of dye Bk ink is discharged from the head 101Bk, and then 15 pl of the processing solution is discharged from the head 101S, to form one black dot. In this case, since the antecedently discharged dye ink is a poor permeable ink, it penetrates little into the recording paper and about 45 pl of the mixed solution is formed when the processing solution is deposited onto the antecedently landed ink. In this case, the acetylenol contents (wt. %) of the Bk ink and the processing solution before mixing are 0% and 2.1% respectively, while the content (wt. %) of acetylenol, surface active agent of the mixed solution, becomes 0.7%. Thus, the above mixed solution becomes a high penetrability ink, which is fixed quickly. Further, the mixed solution has then about 5.0 (ml/m 2 ·msec 1/2 ) of Ka value and about 33 dyne/cm of surface active tension. When 100% duty printing, what is called " solid printing ", was performed, the fixing time was about 1 second after discharging of the processing solution. Example 2 This example is different from the above example 1 in the point that a pigment ink Bk without dispersing agent is discharged from the head 101 Bk shown in Fig. 5. In this example, discharging amount per one nozzle of the head 101 Bk is 30 pl as in the above example 1, and discharging amount of the processing solution is also 15 pl as in the above. However, each acetylenol content of the Bk ink and the processing solution is 0.2 % and 1.7 %, respectively. Thus, the acetylenol content becomes 0.7 % when they are mixed on the recording paper, and this mixed solution shows a high penetrability and is fixed quickly. Also in this example, a printing method similar to the above was employed for fixing time measurement, and similarly, one second was obtained for the fixing time. The above-mentioned pigment Bk ink without dispersing agent is as the following. For a pigment used for this example, a self-dispersion type pigment is used, in which at least a kind of anionic group is bonded to carbon black surface directly or via other atomic group, but for a color material, a self-dispersion type carbon black is used, to which at least a kind of hydrophilic group is bonded directly or via other atomic group. This results in eliminating the need for dispersing agent to disperse carbon black required for conventional ink. For the use in this example, ionized self-dispersing type carbon black is desirable, and anionically electrified one is suitable. In the case of anionically electrified carbon black, for example, -COOM, -SO 3 M, -PO 3 HM, -PO 3 M 2 , SO 2 NH 2 , -SO 2 NHCOR, etc. can be mentioned as a hydrophilic group bonded to the surface (wherein M in the formulae represents hydrogen atom, alkaline metal, ammonium or organic ammonium, and R represents an alkyl group with 1 to 12 carbon atoms, a phenyl group which is allowed to have substituent, or a naphthyl group which is allowed to have substituent). In this example, especially among the above groups, such carbon black is preferably used, as is bonded with -COOM or -SO 3 M on the surface of the carbon black and is anionically electrified. Also, for " M " of the above-mentioned hydrophilic groups, for example, lithium, sodium, potassium, etc. can be mention as an alkaline metal, and for organic ammonium, mono-, di- or tri-methyl ammonium, mono-, di- or tri-ethyl ammonium, mono-, di- or tri-methanol ammonium, etc. can be mentioned. As a method of obtaining anionically electrified carbon black, namely, a method of introducing -COONa onto the surface of carbon black, for example, such a method can be mentioned as carbon black is treated with sodium hypochlorite by oxidation, however, it is obvious that the present invention is not to be restricted by this method. Pigment Bk ink has the following composition. [Black Bk pigment ink] Pigment dispersing solution 50 pts. wt. Glycerin 7 pts. wt. Tri-ethylene glycol 7 pts. wt. Acetylenol 0.2 pts. wt. (made by Kawaken Fine Chemical Co., Ltd.) Water Remainder The above-mentioned pigment dispersing solution is as follows. [Pigment dispersing solution] At 5 °C, 1.58g anthranilic acid was added into a solution in which 5g concentrated hydrochloric acid is dissolved in 5.3g water. This solution was always kept at 10 °C or less, by being stirred in an ice bath, and another solution dissolving 1.78g sodium nitrite added to 8.7 g water was added to that solution. Further, after 15 minutes stirring, 20g carbon black, of which oil absorption is 120ml/100g DBP and a surface area is 320 m 2 /g, was added to the former solution in a mixed state. And then, the mixture was stirred for another 15 minutes. The obtained slurry was filtered by Toyo Filter Paper No. (made by Advantis, Ltd.), and after the pigment particles were sufficiently rinsed and dried in an oven at 110 °C, water was added to the pigment for making 10 wt. % pigment aqueous solution. By this method, a pigment dispersing solution was obtained as expressed by the formula below, in which anionically electrified self-dispersed type carbon black bonded to hidrophilic group via phenyl group is dispersed on the surface. Example 3 In this example, two heads are used with Bk ink, and are configured to discharge dye ink and pigment ink, respectively. Fig. 7 is a schematic sectional view showing a printing apparatus relating to this example. A head 101Bk1 discharges 15 pl dye Bk ink per each nozzle, and a head 101Bk2 discharges 15 pl pigment Bk ink per each nozzle. Also, a processing solution head 101S discharges 15 pl processing solution per each nozzle. And, these dye Bk ink, pigment Bk ink, and processing solution contain 0 %, 0.2 %, and 1.9 % acetylenol, respectively. According to the above composition, when a dot of Bk ink is formed in printing, the above-mentioned dye Bk ink pigment Bk ink, and processing solution are made coalescent on the recording paper 103, and as a result, the acetylenol content of the mixed solution becomes 0.7 %, and the mixed solution becomes highly penetrative. Example 4 In this example, the order of discharging the pigment ink and dye ink is reversed compared with the above example 3. Namely, in Fig 7, the head 101Bk1 discharges pigment ink, and the head 101BK2 discharges dye ink. In this case also, an effect similar to that from the above example 3 can be achieved. Example 5 In this example, one head is provided for Bk ink as shown in Fig. 5, and this head discharges a mixed ink of dye Bk ink and pigment Bk ink. The discharging amount of this head is 30 pl containing 0.1 % acetylenol, while 15 pl processing solution is discharged as in each example described above but 1.9 % acetylenol is contained. Thus, acetylenol content of a mixed solution of the mixed Bk ink and the processing solution becomes 0.7 %. This mixed Bk ink has the following composition. [Mixed Bk ink] Pigment dispersing solution 25 pts. wt. Food black 2 2 pts. wt. Glycerin 6 pts. wt. Tri-ethylene glycol 5 pts. wt. Acetylenol EH 0.1 pts. wt. ( made by Kawaken Fine Chemical Co., Ltd. ) Water Remainder According to this example, an effect similar to that from the above- described examples 3 and 4 can be achieved. Example 6 In this example, Bk ink is provided with two heads, one of which discharges jet 15 pl dye ink per each nozzle and the other discharges 15 pl pigment ink per each nozzle, respectively, and processing solution is also provided with two heads, of which each discharges 8 pl processing solution per each nozzle. By this configuration, discharging is carried out in order of dye Bk ink, pigment Bk ink, processing solution, and processing solution and they form a coalescent solution. Here, acetylenol contents of each solution are 0 %, 0.2 %, 0.2 %, and 3.6 % in the above discharging order, and as a result, an acetylenol content of the coalescent solution becomes 0.7 %. Thus, high fixation can be achieved. In addition to this, in this example, the later in the discharging order a solution is, the higher penetrability the solution has. Therefore, it is possible to coalesce the drops of the earlier discharged solution and the later discharged solution before penetration of the earlier discharged solution, and this coalescence can make the penetrability of the mixed solution higher. Further Examples In each example described above, the compositions of Bk ink to improve its fixation have been described as preferred embodiments of the present invention. However, application of the present invention is not to be restricted by the above. For example, in a case of mixing processing solutions with color inks regarding each color ink, or intermixing light and dark inks regarding a same color, the present invention is applicable thereto. For example, when color printing is performed by using Y, M, and C inks, Y-ink, of which an improvement in concentration is not so much desired, is made as a high permeable ink while other inks are made as poor permeable inks, and thus, it is thereby possible to provide the mixture with a predetermined acetylenol content when they are mixed. Moreover, in the above examples 1 and 2, dye ink or pigment ink was made to be discharged 30 pl from one head per each nozzle, however, the same effect can be also obtained if two heads discharge 15 pl of the ink per nozzle respectively. Moreover, in the above examples, pigment ink without dispersing agent has been described, however, it is obvious that pigment ink with dispersing agent may also be used. Further, each of the dye ink and the pigment ink may partly contain pigment and dye of less composition rate to the other, respectively. Further, in each example of the above, the configuration may be such as a high penetrative processing solution is discharged before Bk ink is further discharged. Further, applicability of the present invention is not to be restricted to a full line type printer as shown in each example of the above, but the invention is applicable to a serial type printer as shown in Fig. 8. Fig. 8 is a schematic drawing showing the constitution of a serial type printer 5 relating to an example of the present invention. Namely, it is obvious that a printing apparatus, wherein dye ink and pigment ink are mixed on a printing medium before they are reacted with a processing solution, is applicable not only to the above-described full line type but also to the serial type apparatus. Here the same components as shown in Fig. 5 or Fig. 7 are marked with the same codes for omitting the detail description about them. Further, two Bk ink heads are provided in the configuration shown in the figure. Recording paper 103 as a printing medium is inserted from a paper feeding part 105 and ejected via printing part 126. In this example, widely used inexpensive ordinary paper is used as recording paper 103. In the printing part 126, a carriage 107 is arranged to mount printing heads 101Bk1, 102Bk2, 101S, 101C, 101M, and 101Y and move back and forth along a guide rail 109 by means of a driving force of an unshown motor. The printing head 101Bk1 discharges black pigment ink, and the printing head 102Bk2 discharges black dye ink. The printing heads 101S, 101C, 101M, and 101Y discharge processing solution, cyan ink, magenta ink, yellow ink, respectively, and are driven in this order to discharge ink or processing solution on a sheet of the recording paper 103. Moreover, the black pigment ink is an ink without dispersing agent. To each head, ink or processing solution is supplied from each tank 108Bk1, 108Bk2, 108S, 108C, 108M and 108Y, respectively. In discharging state, a driving signal is supplied to an electro-thermal transducer of heater disposed at each nozzle of each head, and then thermal energy acts on ink or processing solution to generate a bubble therein, thereby ink or processing solution is discharged by the pressure of the bubble. Each head has 64 discharging portions or nozzles arrayed at 360 dpi in the direction substantially the same as the conveying direction of the recording paper 103, that is, the nozzles are arrayed in the direction perpendicular to the scanning direction of each head. Here, discharging amount per one nozzle is 23 pl. In the above arrangement, each head is arranged at 1/2 inch intervals, and has a printing concentration of 720 dpi in the scanning direction and a discharging frequency of 7.2 kHz. Further, in each example of the above, discharging system of each head makes use of thermal energy to discharge ink or processing solution, however, the present invention does not restrict this applicability but, for example, a system using piezo-element may be applicable. Furthermore, in each example of the above, it is assumed that basically, the later in the discharging order a solution is, the higher penetrability the ink or processing solution has, so that the earlier discharged ink penetrates little into recording paper before the following ink is discharged. However, for example, when a high penetrability ink is adopted for Y-ink as described above and color printing is performed by discharging this ink precedently, Y-ink penetrates into the paper to some extent before the following ink, etc. are discharged. Therefore, in such a case, a discharging rate and discharging intervals of Y-ink discharged at the same time have only to be determined so that acetylenol content becomes a percentage showing the predetermined high penetrability described above to the total solution volume at the time when the succeeding ink is discharged and mixed. As being apparent from the above descriptions, according to the present invention, a plurality of different droplets of ink, processing solution, etc. coalesce into one droplet and its critical micell concentration, surface tension, and Ka value, which represent the penetrability of the droplet, becomes a predetermined value of high penetrability or higher, therefore, the penetration is accelerated as a droplet after coalescence even if not all the component droplets have high penetrability. Thus, even if low penetrative ink, etc. are used to improve OD value and suppress feathering, a high penetrability can be obtained after coalescence and fixation is not inhibited. Consequently, it is possible to achieve high fixation without using a means like a heater, etc. and improve printing quality. The present invention has been described in detail with respect to various embodiments, and it will now be apparent from the foregoing to those skilled in the art that changes and modifications may be made.

Claims: A method of forming an image comprising depositing a plurality of drops on a printing medium, so that at least two of the deposited drops coalesce on the surface of the printing medium into a coalesced drop, characterised in that , amongst the deposited drops which coalesce into one coalesced drop, at least one of the deposited drops has a concentration of a surface-active agent in it of less than the critical micelle concentration of said surface-active agent in pure water and at least one other of the deposited drops has a concentration of a surface-active agent in it of not less than the critical micelle concentration of said surface-active agent in pure water, and the coalesced drop has a concentration of a surface-active agent in it of not less than the critical micelle concentration of said surface-active agent in pure water. A method according to claim 1 in which the said at least one of the deposited drops comprises a drop in which the concentration of the surface-active agent is zero. A method according to claim 1 or claim 2 in which the surface-active agent is ethylene oxide-2,4,7,9-tetramethyl-5-decyne-4,7-diol, (acetylenol) and the said coalesced drop has not less then 0.7% by weight of the surface-active agent. A method of forming an image comprising depositing a plurality of drops on a printing medium, so that at least two of the deposited drops coalesce on the surface of the printing medium into a coalesced drop, characterised in that , amongst the deposited drops which coalesce into one coalesced drop, at least one of the deposited drops has a surface tension of not less than 35 dyne per cm and at least one other of the deposited drops has a surface tension of less than 35 dyne per cm, and the coalesced drop has a surface tension of less than 35 dyne per cm. A method according to claim 4 in which the surface tension of the coalesced drop is about 25 dyne per cm. A method of forming an image comprising depositing a plurality of drops on a printing medium, so that at least two of the deposited drops coalesce on the surface of the printing medium into a coalesced drop, characterised in that , amongst the deposited drops which coalesce into one coalesced drop, at least one of the deposited drops has a Ka value of less than 5 ml/(m 2 .ms ½ ) and at least one other of the deposited drops has a Ka value of not less than 5 ml/(m 2 .ms ½ ), and the coalesced drop has a Ka value of not less than 5 ml/(m 2 .ms ½ ), where Ka is a value representing the penetration speed of the drop, and is defined as (V-V r )/(t-t w ) ½ in which V is the penetration volume in ml per square metre of the printing medium surface, t is elapsed time, and V r is the volume (in ml/m 2 ) absorbed in the rugged part of the surface during a wet time t w . A method according to any one of the preceding claims in which said at least one of the deposited drops and the said at least one other of the deposited drops both comprise an ink drop containing colouring material. A method according to any one of claims 1 to 6 in which the said at least two deposited drops which coalesce on the surface of the printing medium comprise an ink drop containing colouring material and a drop of processing solution for rendering the colouring material of the ink drop insoluble or cohesive. A method according to claim 8 in which the said at least one of the deposited drops comprises the said ink drop, and the said at least one other of the deposited drops comprises the said drop of processing solution. A method according to claim 8 or claim 9 in which the said ink drop is deposited on the surface of the printing medium before the said drop of processing liquid. A method according to any one of claims 1 to 9 in which the said at least one of the deposited drops is deposited on the surface of the printing medium before the said at least one other of the deposited drops. A method according to claim 8 or claim 9 in which at least three deposited drops coalesce on the surface of the printing medium into the said coalesced drop, the said at least three drops comprising the said ink drop, the said drop of processing liquid, and a further ink drop. A method according to claim 12 in which the first said ink drop is deposited on the surface of the printing medium before the drop of processing liquid, and the said further ink drop is deposited on the surface of the printing medium after the drop of processing liquid. A method according to claim 12 in which the first said ink drop and the said further ink drop are both deposited on the surface of the printing medium before the drop of processing liquid. A method according to any one of claims 12 to 14 in which the said at least one of the deposited drops comprises both said ink drops and the said at least one other of the deposited drops comprises the said drop of processing liquid. A method according to any one of claims 7 to 15 in which the ink drop, or one of the ink drops, is a dye ink drop which mainly contains dye as the colouring material. A method according to any one of claims 7 to 15 in which the ink drop, or one of the ink drops, is a pigment ink drop which mainly contains pigment as the colouring material. A method according to any one of claims 7 and 12 to 15 in which one of the said ink drops is a dye ink drop mainly containing dye as the colouring material and the other of the said ink drops is a pigment ink drop mainly containing pigment as the colouring material. A method according to claim 17 or claim 18 in which the pigment ink drop contains a dispersing agent for the pigment. A method according to claim 17 or claim 18 in which the pigment ink drop contains self-dispersing pigment. Image forming apparatus comprising drop depositing means for depositing drops of a plurality of different liquids on a printing medium, and liquid containing means (108) for supplying the different liquids to the drop depositing means, in which the drop depositing means is arranged to deposit a plurality of drops on the printing medium so that at least two of the deposited drops coalesce on the surface of the printing medium into a coalesced drop, characterised in that , amongst the deposited drops which coalesce into one coalesced drop, at least one of the déposited drops has a concentration of a surface-active agent in it of less than the critical micelle concentration of said surface-active agent in pure water and at least one other of the deposited drops has a concentration of a surface-active agent in it of not less than the critical micelle concentration of said surface-active agent in pure water, and the coalesced drop has a concentration of a surface-active agent in it of not less than the critical micelle concentration of said surface-active agent in pure water. Apparatus according to claim 21 in which the said at least one of the deposited drops comprises a drop in which the concentration of the surface-active agent is zero. Apparatus according to claim 21 or claim 22 in which the surface-active agent is ethylene oxide-2,4,7,9-tetramethyl-5-decyne-4,7-diol, (acetylenol) and the said coalesced drop has not less then 0.7% by weight of the surface-active agent. Image forming apparatus comprising drop depositing means for depositing drops of a plurality of different liquids on a printing medium, and liquid containing means (108) for supplying the different liquids to the drop depositing means, in which the drop depositing means is arranged to deposit a plurality of drops on the printing medium so that at least two of the deposited drops coalesce on the surface of the printing medium into a coalesced drop, characterised in that , amongst the deposited drops which coalesce into one coalesced drop, at least one of the deposited drops has a surface tension of not less than 35 dyne per cm and at least one other of the deposited drops has a surface tension of less than 35 dyne per cm, and the coalesced drop has a surface tension of less than 35 dyne per cm. Apparatus according to claim 24 in which the surface tension of the coalesced drop is about 25 dyne per cm. Image forming apparatus comprising drop depositing means for depositing drops of a plurality of different liquids on a printing medium, and liquid containing means (108) for supplying the different liquids to the drop depositing means, in which the drop depositing means is arranged to deposit a plurality of drops on the printing medium so that at least two of the deposited drops coalesce on the surface of the printing medium into a coalesced drop, characterised in that , amongst the deposited drops which coalesce into one coalesced drop, at least one of the deposited drops has a Ka value of less than 5 ml/(m 2 .ms ½ ) and at least one other of the deposited drops has a Ka value of not less than 5 ml/(m 2 .ms ½ ), and the coalesced drop has a Ka value of not less than 5 ml/(m 2 .ms ½ ), where Ka is a value representing the penetration speed of the drop, and is defined as (V-V r )/(t-t w ) ½ in which V is the penetration volume in ml per square metre of the printing medium surface, t is elapsed time, and V r is the volume (in ml/m 2 ) absorbed in the rugged part of the surface during a wet time t w . Apparatus according to any one of claims 21 to 26 in which said at least one of the deposited drops and the said at least one other of the deposited drops both comprise an ink drop containing colouring material. Apparatus according to any one of claims 21 to 26 in which the said at least two deposited drops which coalesce on the surface of the printing medium comprise an ink drop containing colouring material and a drop of processing solution for rendering the colouring material of the ink drop insoluble or cohesive. Apparatus according to claim 28 in which the said at least one of the deposited drops comprises the said ink drop, and the said at least one other of the deposited drops comprises the said drop of processing solution. Apparatus according to claim 28 or claim 29 in which the drop depositing means is arranged to deposit the said ink drop on the surface of the printing medium before the said drop of processing liquid. Apparatus according to any one of claims 21 to 29 in which the drop depositing means is arranged to deposit the said at least one of the deposited drops on the surface of the printing medium before the said at least one other of the deposited drops. Apparatus according to claim 28 or claim 29 in which the drop depositing means is arranged to deposit a plurality of drops on the printing medium so that at least three deposited drops coalesce on the surface of the printing medium into the said coalesced drop, the said at least three drops comprising the said ink drop, the said drop of processing liquid, and a further ink drop. Apparatus according to claim 32 in which the drop depositing means is arranged to deposit the first said ink drop on the surface of the printing medium before the drop of processing liquid, and to deposit the said further ink drop on the surface of the printing medium after the drop of processing liquid. Apparatus according to claim 32 in which the drop depositing means is arranged to deposit both the first said ink drop and the said further ink drop on the surface of the printing medium before the drop of processing liquid. Apparatus according to any one of claims 32 to 34 in which the said at least one of the deposited drops comprises both said ink drops and the said at least one other of the deposited drops comprises the said drop of processing liquid. Apparatus according to any one of claims 27 to 35 in which the ink drop, or one of the ink drops, is a dye ink drop which mainly contains dye or the colouring material. Apparatus according to any one of claims 27 to 35 in which the ink drop, or one of the ink drops, is a pigment ink drop which mainly contains pigment as the colouring material. Apparatus according to any one of claims, 27 and 32 to 35 in which one of the said ink drops is a dye ink drop mainly containing dye as the colouring material and the other of the said ink drops is a pigment ink drop mainly containing pigment as the colouring material. Apparatus according to claim 37 or claim 38 in which the pigment ink drop contains a dispersing agent for the pigment. Apparatus according to claim 37 or claim 38 in which the pigment ink drop contains self-dispersing pigment.

Inventors: KOITABASHI NORIBUMI, KOITABASHI, NORIBUMI, Koitabashi, Noribumi, Canon Kabushiki Kaisha
Applicants: CANON KK, CANON KABUSHIKI KAISHA
Application year: 1998
Main classification: C09D11
IPC codes: B41J2, B41M5, C09D11