CA1296220C

CA1296220C - Ink-jet recording process

Info

Publication number: CA1296220C
Application number: CA000555298A
Authority: CA
Inventors: Kazuo Iwata; Osamu Nishiwaki; Shinichi Tochihara
Original assignee: Canon Inc
Current assignee: Canon Inc
Priority date: 1986-12-24
Filing date: 1987-12-23
Publication date: 1992-02-25
Anticipated expiration: 2009-02-25
Also published as: EP0272936A3; US4931810A; EP0272936A2; EP0272936B1; DE3789765T2; DE3789765D1

Abstract

ABSTRACT OF THE DISCLOSURE
There is disclosed ink-jet recording process for carrying out a recording by adhering ink droplets on a recording medium, wherein the recording is carried out under the condition that the ink is adhered in an amount ranging between 3.0 x 105 pl/cm2 and 3.0 x 106 pl/cm2 in solid image recording when the recording is carried out with a recording density of 10 dots/mm x 10 dots/mm or more.

Description

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The present invention relates to an ink-jet recording process for recording information such as images, letters and symbols on paper, light-transmissive recording medium or the like with use of an ink-jet recording apparatus.

Ink-jet recording has been hitherto known as a superior recording method suitable for a wide range of recording media. Much research and development has been directed to ink-jet recording apparatus, recording processes and recording mediums.

In ink-jet recording apparatus hitherto developed and made commercially available, it has been difficult to obtain;

i) a recorded image having a high optical density (or OD);

.
ii) a recorded image of good print quality and free from any feathering on the peripheral parts of letters or images, and ~2~

iii) a good drying time characteristic;
unless recording mediums are used developed for exclusive use in ink-jet recording, known as ink-jet recording paper or ink-jet recording transparency films.

The above requirements i) to iii) can not be simultaneously satisfied when recording is carried out on recording media such as conventional paper including elactro-photographic recording paper (PPC paper), letter paper, bond paper, post cards, writing paper, envelopes, report paper, etc. which are generally used in offices, homes, etc. and conventional transparent films (OHP films), using known ink-jet recording apparatus. Even when an ink-jet recording paper is used, there is the disadvantage such that recording can not be performed on both sides of the paper, since most ink-jet recording paper is one-side coated paper, and thus the print quality and the drying time characteristic may deteriorate if recording is carried out on the uncoated side.

Various developments have been proposed for the ~ purpose of obtaining recorded images;
i) which are not restricted as to choice of recording surface (or are not restricted as to choice of materials such as paper or ~ilms, or as to use of the reverse side ~2~62Z~

thereof);
ii) which have a high optical density (OD);
iii) which provide good print quality free from feathering; and iv) which have a good drying time characteristic.
One such process in which recording is carried out using a strongly alkaline ink of about pH 13 is described in Japanese Laid-Open Patent Application No. 102970/1982, and in another such process, recording is carried out using an ink-jet re~ording apparatus of a continuous type, such as the charge-controlled type.

In the first process mentioned above, the ink is so strongly alkaline as to be dangerous to handle, and, although good printing can be performed on acid sized paper employing resin or the like, both drying time and print quality may be greatly lowered on neutral paper employing an alkyl ketone dimer or the like, and stri~e-through tends to occur probably because of high permeability of the ink into the paper.

Although the second process mentioned above can achieve a recording of relatively high density, there is a limit to the precision of the nozzles from which ink is ejected, and thus fine ink droplets can be stably ejected only with difficulty. As a result, unless the recording ,~

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density is controlled to not substantially more than about 9.5 dots/mm (240 dots/inch), the drying time characteristic may deteriorate (i.e., the recording surface may be soiled when smeared with fingers) and the irregular spreading of dots called "feathering" may occur, because of an overly large amount of the ink to be fixed on the recording surface. This causes lowered print quality, i.e., a recorded image having unsharp peripheral parts.

With a recording density of about 9.5 dots/mm, it is impossible to carry out sharp printing of closely spaced chinese characters (such as " ~ "), and sometimes difficult to perform smooth and natural reproduction of oblique and curved lines such as "/", " ~ " or "o ", every dot being apparent to visual observation, giving recorded images of conspicuous jaggedness and low quality.

~ Accordingly, an object of the present invention is to provide an ink-jet recording process better capable of meeting the requirements that lt i) is non-critical in choice of recording surface (or is non-critical in choice of materials such as paper or films and of the side of the material which is used);
ii) achieves a high optical density (OD);
iii) provides good print quality free from feathering;

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and iv) achieves a good drying time characteristic;

A further object of the present invention is to provide an ink-jet recording process which c~n smGothly and naturally reprsduce a complicated chinese charact~r or oblique or curved lines in an image.

The present invention provides an ink-jet recording process comprising the steps of ejecting ink droplets; and adhering said ink droplets on a recording medium at a recording density of at least lO0 dots/mm2, in an amount ranging between 3.0x105 and 3.0xlO6 pl/cm2.

In an embodiment of the present invention, there is provided an ink-jet recording process comprising the steps of ejecting ink droplets; and adhering said ink droplets on a recording medium at a recording density of at least 196 dots/mm2, in an amount ranging between l.OxlO6 and 2.0 x lO6pl/cm2.

: In a further embodiment of the present invention, there is provided an ink-jet recording process comprising the steps of selecting an ink conta1ning l to 45% by weight of an organic solvent having a boiling point of at least l50' C: ejecting droplets of said ink; and adhering said 12~622~

ink droplets on a recording medium at a recording density of at least 100 dots/mm2 in an amount ranging between 3.0xlOs and 3.0x106 pl/cm2.

In a still further embodiment of the present invention, there is provided an ink-jet recording process comprising the steps of selecting an ink containing 1 to 45% by weight of an organic solvent having a boiling point of at least 150; ejecting droplets of said inX; and adhering said ink droplets on a recording medium at a recording density of at least 196 dots/mm2 in an amount ranging between l.Ox106 and 2.0x106 pl/cm2.

In a still further embodiment of the present invention, there is provided an ink-jet recording process comprising the steps of ejecting droplets of inks of different colors; and adhering said ink droplets on a recording medium at a recording density of at least 100 dots/mm2 in an amount ranging ~etween 3.0xlOs and 3.0x106 pl/cm2 .

A still further embodiment of the present invention consists of an ink-jet recording system comprising a recording head for ejecting droplets of ink toward a recording medium, wherein the amount of ink adhered on the recording medium from the recording head is ~Z~6~Z2~1 within the range of 3.0 x 105 to 3.0 x 106 pl/cm2 when recording is performed at a recording density of at least 100 dots/mm2.

A first feature of the present invention is to use S an ink-jet recording apparatus with a recording density of at least 10 dots/mm x 10 dots/mm (length x width). The present inventors have researched and studied the relationship between recording density and appearance of the printed image and have found that curved and oblique lines appear smooth and natural if the recording density is at least 10 dots/mm x 10 dots/mm or more.

If recording density is as low as about ~ dots/mm x 8 dots/mm or less, it was found that the size of each dot is so large that any abnormality such as white-spotting, color non-uniformity or density non-uniformity tends to become conspicuous when mis-direction of ink ejection has occurred for some reason (for example, because of dust on the nozzles).

In contrast, it was also found that with a recording density of 10 dots/mm x 10 dots/mm or more, each dot is originally so small that such abnormalities are barely noticeable. Only a very narrow streak (white-spotting), non-uniformity in color or non-uniformity in .

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density was produced even when misdirection of ejection occurred.

Where recording was carried out with a recording density of about 4 to 8 dots/mm x 4 to 8 dots/mm and using ink droplets of large size, it was further found that ink droplets impinge on the recording surface before ink droplets previously adhered can permeate into the recording face when the succeeding ink droplets immediately follow previous ink droplets, so that the ink is splashed around the dots where the dots are overlapped, thus soiling the recording surface.

Again by contrast, recording can be satisfactorily performed when recording density is in the range of 10 dots/mm x 10 dots/mm or more, preferably in the range of from 10 dots/mm x 10 dots/mm to 24 dots/mm x 24 dots/mm, and more preferably in the range of from 14 dots/mm x 14 dots/mm to 24 dots/mm x 24 dots/mm.

Su~h recording can also be satisfactorily performed when employing a multi-nozzle on-demand system.
In a multinozzle system, a plurality of nozzles are used for forming one image and ad~acent dots are substantially simultaneously applied in printing.

129~220 A second feature of the present invention is the amount of the ink to be adhered on the recording face. The objects of the present invention are simultaneously addressed by controlling within a given range the amount of the ink adhered on the recording face.

If too little ink is adhered, insufficient colorant is present on the recording surface with the disadvantage that the optical density (OD) of the recorded image decreases, providing unsharp recorded images giving the impression that they are faint as a whole.

If a concentration of the dye in the ink is increased to 10% by weight or more for the purpose of solving this problem, a sufficient value for OD can be attained, but, in recording apparatus having multi-nozzles, a nozzle or nozzles not in use for recording may become clogged with the ink, resulting in inoperability in practical purposes.
.

If on the other hand the ink is adhered on the recording face in a greater amount, the drying time characteristic tends to deteriorate severely as shown below, even if the colorant is contained in the ink in a decreased amount.

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For example;
i) under the high humidiky conditions, as in damp weather, drying time is increased because the recording medium has absorbed moisture and also medium components in the ink may be more slowly evaporated from the surface of the recording medium.

ii~ under low temperature conditions as in winter, drying time is increased because medium components in the ink may be more slowly evaporated.

iii) where recording is performed on paper which is heavily sized to prevent feathering, it takes a long time for ink to permeate into the paper, so drying is slower.

When the ink is adhered on the recording face in a greaker amount and also the colorant is contained in a greater amount, the recorded images may be badly soiled if they are smeared with sweaty finqers or the like.

The present inventors have studied under varied conditions the optimum amount of ink to be adhered on the recording surface. As a result, they found that the recording should preferably be carried out such that the ~`

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amount ranges preferably be~ween 3.0 x 105 pl/cm2 and 3.0 x 106 pl/cm2, more preferably between 5.0 x 105 pl/cm2 and 2.5 x 106 pl/cm2, and most preferably between 1.0 x 106 pl/cm2 and 2.0 x 106 pl/cm2, when recording solid images, and thus reached the present invention.

Where color-mixed areas are formed on a recording medium with use of two or more inks of different colors, aæ in a color printer, recording is still preferably carried out using an amount of the ink in the ranges described above.

For example, where a yellow area is formed on the recording medium by use of yellow ink and a green area is formed by overlapping cyan ink on the yellow ink, it follows that ink is adhered on the recording medium in an amount twice that used in the case of a monochrome image.
The amount of the ink to be adhered at the color mixed areas should still be controlled within the range described above.

In inks used in tha present invention, any conventional dyes and colorants can be used as coloring materials, and any kind and amount thereof may be selected depending on the purposes they are used for. Such dyes should be selected taking into account their tendency to ~2~ 2~

clog nozzles and so forth.

As for concentration of the colorant, it is preferably used in the range of 0.5 to 10.0% by weight, preferably in the range of 1.0 to 5.0~ by weight, and more preferably in the range of 1.0 to 3.0% by weight based on the total amount of the ink, taking account of the optical density (OD) required in the recorded images.

A liquid medium for dissolving or dispersing the colorant may be any aqueous system in which water and water-soluble organic solvents such as glycols and glycol ethers are used in combination, or non-aqueous systems containing aromatic, aliphatic, ester or ether type water-insoluble organic solvents.

For considerations of safety, small, strike-through paper, etc., aqueous systems are preferred.

The present inventors have further studied the use of organic solvents in the ink. They found that better results can be obtained when the ink contains 1 to 45% by weight of an organic solvent having a boiling point of 150 C or more.

If an organic solvent having a boiling point of :~LZ~2;2~

150C or more, among the organic solvents contained in the ink, is present in an amount more than 45% by weight, it tends to take a long time for the solvent to be evaporated from the recording surface or for the solvent to permeate into the recording surface; in other words, the drying ~ime characteristic deteriorates.

It was also confirmed that, where the organic solvent has a boiling point of 300 C or more, and if it is contained in the ink in an amount of 10%
by weight or more, the drying time characteristic tends to deteriorate and also the ink tends to permeate slowly into the recording medium, even when the remaining part of the solvent is constituted only of a solvent having a boiling point of 150 C or less such as water, alcohol and aliphatic hydrocarbons, so that it may sometimes occur that the "whiskers" called feathering are likely to appear in the printed image when the ink permeates, making it impossible to o~tain images having a good print quality.

The content of organic solvent having a boiling point of 150 C or more is preferably in the range of from 1 to 30% by weight, still more preferably in the range of from 1 to 25% by weight, and most preferably in the range of from 5 to ~0% by weight. In the case of an organic solvent having a boiling point of 300 C or more, its ,~

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content is preferably in the range of 5~ by weight or less.

When using an organic solvent having a boiling point of 150 C or more, it is conventional wisdom that the drying ~ime characteristic is improved as the solvent content is reduced. In fact it sometimes occurs that the drying time characteristic deteriorates if the solvent is contained in an overly small amount. Thus, it should be present in an amount of ~% by weight or more, preferably 5% by weight or more.

The recording medium used may be any coated or uncoated paper, but particularly effective for the present invention is a paper having a basis weight in the range of from 45 to 200 g/m2 .

The amount of ink to be adhered (in pl/cm2), as used in the present invention, can be readily determined either by 1) measuring the decrease, after solid image recording, of ink in an ink tank connected to the print head nozzles, and determining the area o~ the solid image recording produced; and 2) measuring the amount of ink ejec~ed from one nozzle by a single actuating signal, and the recording density in dots per unit area.

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The present invention will be described below in greater detail with reference to Examples and Comparative Examples.

Example 1 Ink prepared as having the following composition.
C.I.Direct Black 62 3.0 wt.~
Ethanol (b.p. 78C) 0.5 wt.%
Ethylene glycol (b.p. 197C)20.0 wt.%
Diethylene glycol (b.p. 245C)5.0 wt.%
Water 71.5 wt.%

Using this ink and also using an ink-jet recording apparatus having a multi-nozzle on-demand type head having 48 nozzles, ink-jet recording was performed at a recording density of 14.2 dots/mm x 14.2 dots/mm (360 dots/inch x 360 dots/inch) on the five kinds of paper (A) to (E) shown below in solid image recording mode such that the volume of ink ejected from one nozzle by one signal was 58 pl; in other words, the ink was adhered on the recording face in an amount of 1.2 x 106 pl/cm2.

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-15a-As a result, the resulting recorded images had an average optical density (OD~ of 1.2.

The drying time (the shortest time before the recorded images are not soiled if they are smeared with filter paper) under 80% RUI at 15C was also found to be 52 seconds in an average value; and the drying time under 55 RH at 20C averaged 41 s~conds.

The appearance of recorded images were evaluated overall by 10 panelists in respect of optical density, gradation, presence of feathering, and reproducibility of an image in an oblique~line part and a curved line part thereof. The five rank evaluation (5: very good .... 1:
very poor) was 4.2 in an average value, showing a good result.

Ink-jet recording was also performad according to the process of the present invention on a transparent ~2~2~

l film comprising a polyester film coated with a mixture of polyvinyl alcohol and polyvinyl pyrrolidone. As a result, there were obtained good recorded images.
Paper for recorded image evaluation:
(A): Canon Paper NP-DRY (available from Canon Inc,;
PPC paper) (B): Xerox 4024 DP (available from Xerox Corp.; PPC
paper) (C): Hammermill Bond (available from Hammermill paper Corp.; bond paper) (D): Gilbert Bond (available from Mead Corp.; bond paper) (E): New OK (available from Oji Paper Co., Ltd.;
wood free paper) Examples_2 to 9 Using the inks having the composition as shown below in (2) to (9), recordings were performed in the same manner as in Example 1 but under the conditions as shown in Table 1. As a result, there were obtained good results in all as shown in Table 2.
(2):
C.I. ~ood Black 2 1.4 wt.%
C.I. Direct Yellow 86 0.1 wt.%
Diethylene glycol 8.0 wt.%
n-Propyl alcohol (b.p. 97C~ 5.0 wt.%
Water 8S.5 wt.%

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1 (3):
C.I. Acid Black 52 2.5 wt.%
Glycerol (b.p. 290C) 17.5 wt.~
Ethylene glycol 5.0 wt.
5 Methanol (b-p. 64.5C) 4.0 wt.%
Water 71 . O wt . %
( 4 ) :
C.I. Direct Blue 199 2.0 wt.%
Diethylene glycol 15.0 wt.%
lO n-Butanol (b.p. 118C) , 1.0 wt.%
Water 82.0 wt.%
(5):
C.I. Direct Black 154 . 2.0 wt.~
Thiodiethanol (b.p. 282C) 14.0 wt.%
15 Glycerol 6.0 wt.%
~thanol 4.0 wt.%
Water ~4.0 wt.
(6):
C.I. Acid Red 8 5.0 wt.%
Polyethylene glycol 200 (b.p.> 300C) 3.0 wt.%
~thylene glycol 30.0 wt.%
Water 62.0 wt.%
( ~ ) :
C.I. Food Black 2 1.4 wt.%
C.I. Direct Yellow 86 0.1 wt.%
Glycerol 10.0 wt.
Thiodiethanol 10.0 wt.%

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Water 78.5 wt.%
(8):
C.I. Solvent Black 29 1.0 wt.%
Benzyl alcohol (b.p. 205C) 20.0 wt.%
Methyl cellosolve (b.p. 125C) 10.0 wt.%
Ethanol 69.0 wt.%
(9):
C.I. Food Black 2 2.6 wt.%
C.I. Direct Red 227 0.2 wt.%
C.I. Direct Yellow 86 0.2 wt.%
Diethylene glycol 11.0 wt.%
Ethylene glycol 5.0 wt.%
Ethanol 3.0 wt.%
Water 78.0 wt.%

Exam~les 10 and 11 Using in~ having the same composition as in Example 9, recording was performed in the same manner as in Example 1 but under the conditions as shown in Table 1.
As a result, good results were obtained as shown in Table 2.

Exam~le 12 Prepared were ink (Y) and ink (C) of the ,~

~96220 ~,b following composition.
Ink (Y):
C.I. Direct Yellow 86 1.5 wt.
Diethylene glycol 20.0 wt.%
Ethanol 5.0 wt.~
Water 73.5 wt.%
Ink (C) C.I. Direct Blue 199 2.5 wt.%
Diethylene glycol 20.0 wt.
Ethanol 5.0 wt.~
Water 72.5 wt.%

Using ink (Y) and ink (C) and also using an ink jet recording apparatus having two multi-nozzle on-demand type heads each having 256 nozzles ink jet recording for green images was performed at a recording density of 15.7 dots/mm x 15.7 dots/mm (400 dots/inch x 400 dots/inch) on the five kinds of paper (A) to (E) shown in example 1 by making a print in an overlapping fashion in the solid image recording mode such that the volume of ink ejected from each nozzle in each head responsive to each signal was 35 pl; in other words, the ink was adhered on the recording face in an amount of 1.7 x 106 pl/cm2.

As a result, the resulting recorded images had an average optical den~ity (OD) of 1.3.

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-19a-The drying time under 80% RH at 15C was also found to be 47 seconds; and under 55% RH at 20C, 32 seconds; both are average values.

The overall evaluation score was 4.2, showing good results.

~296220 Comparative Examples l and 2 Using ink having the following composition, recording was carried out in the same manner as in Example 1 but under the conditions as shown in Table 1. Results obtained are shown in Table 2.

C.I. Food Black 2 1.9 wt.%
C.I. Direct Yellow 860.1 wt.%
Glycerol 15.0 wt.%
Triethylene glycol (b.p. 288 C) 8.0 wt.%
Water 75.0 wt.%

Comparative Examples 3_and 4 Using ink having the following composition, recording was carried out in the same manner as in Example 1 but under the conditions as shown in Table 1. The results obtained are shown in Table 2.

C.I. Food Black 2 2.9 wt.%
C.I. Direct Yellow 860.1 wt.%
Ethylene glycol 5.0 wt.%
Diethylene glycol10.0 wt.%
Ethanol 2.0 wt.%
Water 70.0 wt.%
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1 Table l , _ _ . _ .. _ . _ . . . . _ *2 *3 Noz- Ink Amount of Recording density zle vol- ink adher-dots/mm2 (DPI)*1 num- ume ed _ _ ber ~xamples:
211.8 x 11.8 (300 x 300)50 51 7.1 x 105 315.7 x 15.7 (400 x 400)128 15 3.Y x 105 418.9 x 18.g (480 x 480)64 45 1.6 x 106 514.2 x 14.2 [360 x 360)48 88 1.~ x 106 611.3 x 11.3 (288 x 288)36 195 2.5 x 106 711.8 x 23.6 (300 x 600)50 78 2.2 x 106 811.8 x 11.8 (300 x 300)50 204 2.8 x 106 915.7 x 15.7 (400 x 400)256 44 1.1 x 106 1014.2 x 14.2 (360 x 360)64 67 1.3 x 106 1118.9 x 18.9 (480 x 480)128 35 1.4 x 106 Comparative Examples:
19.4 x 9.4 (240 x 240) 32 120 1.1 ~ 1~6 214.2 x 14.2 (360 x 360)48 203 4.1 x 106 315.~ x 15.7 (400 x 400)i~8 11 2.7 x 105 47.1 x 7.1 (180 x 1~0) 24 102 5.1 x 105 __ *1: DPI = Dots/inch 12~6Z;;~() l *2: The volume of ink ejected from one nozzle according to one signal.
*3: The amount oP ink adhered in solid image recording.

Table 2 optical Dry time ~sec) Overall density15C, 80%RH20C, 55%RHevaluation (OD~
10 Examples:
2 1.1 37 24 4.1 3 0.9 31 20 3.9 4 1.2 31 26 4.3 1.3 45 36 4.4 6 1.6 54 44 4.0 7 1.4 42 30 4.1 8 0.9 <5 <5 4.0 9 1.4 35 20 4.4 1.5 27 15 ~.3 : 20 11 1.5 33 26 4.5 : Co~parative Examplee:
1 0.8 : 50 41 3.1 :
2 1.6 143 115 2.4 3: 0.5 37 22 1.9 4 0.7 73 46 2.1 ~ .

~29~iz~o I As described above, the present invention can obtain good images superior in ink fixing performancè
and optical density of images, and also free from any feathering, even when ordinary paper is used in high density recording.

Claims

1. An ink-jet recording process comprising the steps of:
ejecting ink droplets; and adhering said ink droplets on a recording medium at a recording density of at least 100 dots/mm2, in an amount ranging between 3.0x105 and 3.0x106 pl/cm2.

2. The ink-jet recording process of claim 1, wherein said recording process is carried out by a multi-nozzle on-demand system.

3. The ink-jet recording process of claim 1, wherein said recording density is at most 576 dots/mm2.

4. The ink-jet recording process of claim 2, wherein said recording density is at least 196 dots/mm2.

5. The ink-jet recording process of claim 1, wherein said ink is adhered in an amount ranging between 5.0x105pl/cm2 and 2.5x106pl/cm2.

6. The ink-jet recording process of claim 1, wherein said ink is adhered in an amount ranging between 1.0x106pl/cm2 and 2.0x106pl/cm2.

7. The ink-jet recording process of claim 1, wherein said ink contains a colorant in the range of 0.5 to 10% by weight.

8. The ink-jet recording process of claim 1, wherein said recording medium is a sheet of paper having a basis weight ranging between 45 and 200 g/m2.

9. An ink-jet recording process comprising the steps of:
ejecting ink droplets; and adhering said ink droplets on a recording medium at a recording density of at least 196 dots/mm2 in an amount ranging between 1.0x106 and 2.0x106pl/cm2.

10. The ink-jet recording process of claim 9, wherein said recording process is carried out by a multi-nozzle on-demand system.

11. The ink-jet recording process of claim 9, wherein said recording density is at most 576 dots/mm2.

12. The ink-jet recording process of claim 9, wherein said ink contains a colorant in the range of 0.5 to 10% by weight.

13. The ink-jet recording process of claim 9, wherein said recording medium is a sheet of paper having a basis weight ranging between 45 and 200 g/m2.

14. An ink-jet recording process comprising the steps of:
selecting an ink containing 1 to 45% by weight of an organic solvent having a boiling point of at least 150°C.;
ejecting droplets of said ink; and adhering said ink droplets on a recording medium at a recording density of at least 100 dots/mm2 in an amount ranging between 3.0x105 and 3.0x106 pl/cm2.

15. The ink-jet recording process of claim 14, wherein said recording process is carried out by a multi-nozzle system.

16. The ink-jet recording process of claim 14, wherein said recording density is at most 576 dots/mm2.

17. The ink-jet recording process of claim 15, wherein said recording density is at least 196 dots/mm2.

18. The ink-jet recording process of claim 14, wherein said ink is adhered in an amount ranging between 5.0x105 pl/cm2 and 2.5x106 pl/cm2.

19. The ink jet recording process of claim 14, wherein said ink is adhered in an amount ranging between 1.0x106 pl/cm2 and 2.0x106 pl/cm2.

20. The ink-jet recording process of claim 14, wherein said ink contains a colorant in the range of 0.5 to 10% by weight.

21. The ink-jet recording process of claim 14, wherein said recording medium is a sheet of paper having a basis weight ranging between 45 and 200 g/m2.

22. An ink-jet recording process comprising the steps of:
selecting an ink containing 1 to 45% by weight of an organic solvent having a boiling point of at least 150°C.;
ejecting droplets of said ink; and adhering said ink droplets on a recording medium at a recording density of at least 196 dots/mm2 in an amount ranging between 1.0x106 and 2.0x106 pl/cm2.

23. The ink-jet recording process of claim 22, wherein said recording process is carried out by a multi-nozzle system.

24. The ink-jet recording process of claim 22, wherein said recording density is at most 576 dots/mm2.

25. The ink-jet recording process of claim 22 wherein said ink contains a colorant in the range of 0.5 to 10% by weight.

26. The ink-jet recording process of claim 22, wherein said recording medium is a sheet of paper having a basis weight ranging between 45 and 200 g/m2.

27. The ink-jet recording process of claim 25, wherein said recording process is carried out by an on-demand system.

28. The ink-jet recording process of claim 21, wherein said recording process is carried out by an on-demand system.

29. An ink-jet recording process for forming a color image with inks of different colors, which comprises the steps of:
ejecting droplets of said inks of different colors; and adhering said ink droplets on a recording medium at a recording density of at least 100 dots/mm2 in an amount ranging between 3.0x105 and 3.0x106 pl/cm2.

30. The ink-jet process of claim 29, wherein said recording process is carried out by a multi-nozzle on-demand system.

31. The ink-jet process of claim 30, wherein said recording density is at most 576 dots/mm2.

32. The ink-jet process of claim 31, wherein said recording density is at least 196 dots/mm2.

33. The ink-jet recording process of claim 29, wherein said inks are adhered in an amount ranging between 5.0x105 and 2.5x106 pl/cm2.

34. The ink-jet recording process of claim 32, wherein said inks are adhered in an amount ranging between 1.0x106 and 2.0x106 pl/cm2.

35. The ink-Jet recording process of claim 30, wherein said inks each contain a colorant in the range of 0.5 to 10% by weight.

36. The ink-jet recording process of claim 35, wherein said recording medium is a sheet oF paper having a basis weight ranging between 45 and 200 g/m2.

37. An ink-jet recording system comprising a recording head for ejecting droplets of ink toward a recording medium, wherein the amount of ink adhered on the recording medium from the recording head is controlled within the range of 3.0x105 to 3.0x106 pl/cm2 when recording is performed at a recording density of at least 100 dots/mm2.

38. An ink-jet recording system according to claim 37, wherein said head has at least 36 nozzles.

39. An ink-jet recording system according to claim 37, wherein the at least 36 nozzles eject the same color ink.

40. An ink-jet recording system according to claim 37, wherein said head has at most 256 nozzles.

41. An ink-jet recording system according to claim 37, wherein the at most 256 nozzles eject the same color ink.

42. An ink-jet recording system according to claim 37, wherein the amount of ink adhered on the recording medium is within the range of 5.0x105 to 2.5x106 pl/cm2.

43. An ink-jet recording system according to claim 37, wherein the amount of ink adhered on the recording medium is within the range of 1.0x105 to 2.0x106 pl/cm2.