JP2003211640A - Method and apparatus for inkjet recording, and ink set - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for obtaining highly fine images by carrying out recording by solving the problem named as 'overflow' that images are blurred because ink is late in penetrating to be absorbed in a recording medium, and further shortening a fixing time. <P>SOLUTION: Imaging is carried out by forming adjacent pixels of the same color through application of ink drops having different surface tensions, the same color and the same concentration to the recording medium in a sequence from a lower surface tension. Moreover, next ink drops for forming a pixel adjacent to a prior pixel are applied before the prior pixel by ink drops adhering to the recording medium is fixed, thereby uniting the ink between the ink drops. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording apparatus to which a full multi system having a nozzle array corresponding to a print width can be preferably applied and image formation using the same, and more specifically, to an ink jet recording apparatus having the same color and the same density. The present invention relates to an inkjet recording apparatus having at least two inkjet heads that discharge the above, an image forming method, and an ink set used for these.

[0002]

2. Description of the Related Art An ink jet head having nozzles arranged at a high density and having nozzles corresponding to a recording width (recording medium width) is generally called a full-multi type ink jet and can print at an ultrahigh speed.

[0003]

In the full-multi type ink jet, since the ink is applied to the recording medium in a short time, the penetration and absorption of the ink into the recording medium cannot be made in time.
There is a problem that a phenomenon called "overflow" occurs and the image is blurred.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems and to provide a method for recording without causing "overflow" and further shortening the fixing time.

Another object of the present invention is to provide an ink jet recording apparatus and an ink set used in such an image forming method.

[0006]

An image forming method according to an embodiment of the present invention which can achieve the above object is to form an image by applying ink as droplets to a recording medium to form pixels. In the image forming method, the method further comprises the step of forming adjacent pixels of the same color by applying ink droplets of the same color and the same concentration having different surface tensions to the recording medium in ascending order of surface tension.

An ink jet recording apparatus according to an embodiment of the present invention which can achieve the above object is
In an inkjet device having a recording head having an ejection unit that ejects ink, a first ejection unit that ejects the ink having the lower surface tension of two types of ink having different surface tensions and having the same density and the same concentration; The surface tension of one or more of the combination with the second ejection unit that ejects the ink of higher ink, the ink droplets ejected from the first ejection unit, and the ink droplets ejected from the second ejection unit. And a control unit that controls the pixels formed from these ink droplets to be adjacent to each other in the ascending order.

Further, an ink set according to an embodiment of the present invention which can achieve the above object is an ink set having a plurality of inks for at least one color, in which surface tension is applied to a plurality of inks of the same color and the same density. It is characterized by containing two or more of different inks.

Further, an ink jet recording apparatus according to another embodiment of the present invention which can achieve the above object is to form adjacent pixels before the pixels formed by the ink droplets previously attached to the recording medium are fixed. Control means for applying the next ink droplet and mixing the ink between these ink droplets.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION An ink having a low surface tension has good wettability with a recording medium and has a fast penetration. In addition, when ink is applied to a pixel adjacent to a pixel formed by ink having a low surface tension, even if the surface tension of this ink is high, the ink having a low surface tension previously recorded is affected by the ink contacting the adjacent pixel. Penetration is faster and fixing time is shorter as a whole.

If the surface tension of the succeeding ink is also lowered, the fixing time becomes shorter, but the penetrating force is too strong, so that feathering and strike-through occur and the image quality deteriorates. By lowering the surface tension of the preceding ink and increasing the surface tension of the subsequent ink, it is possible to maintain a short fixing time and a sufficiently high image quality.

It is preferable that the preceding ink droplet and the succeeding ink droplet for recording the adjacent pixels have the same color.
Here, the ink of the same color is one in which the difference in color cannot be visually recognized, and can be defined based on the color difference, for example. Depending on the input image, only one ink may be recorded, but if the tint is different at this time, the uniformity of the image will be impaired. In general, the human eye does not know the difference if the color difference ΔE = √ (a ^{* 2} + b ^{* 2} + L ^{* 2} ) is 1 or less, and even if it is about 2 to 3, almost no difference is found. The color difference between these two inks is preferably 3 or less, more preferably 2 or less, still more preferably 1 or less.

The difference between the preceding ink droplet having a high surface tension and the following ink droplet having a low surface tension is 0.1 to 20 d.
It can be selected from the range of yn / cm.

This method is suitable for the case where shortening the fixing time is an important issue, for example, for printing a large amount of recording on plain paper at an ultrahigh speed.

Further, it is preferable that a reaction such as aggregation does not occur when the two types of ink are mixed. This is because it is desirable that the two inks mix and penetrate quickly when they come into contact with each other.

The contact between the two kinds of ink requires contact as a liquid. This requires that subsequent ink droplets land before the preceding ink droplets have yet settled.
The fixing time of the preceding ink is the volume of the ink, the surface tension of the ink, the viscosity, the wettability with the recording material, the porosity of the recording material,
Determined by physical properties such as pore size and roughness. It suffices that the subsequent ink lands before the fixing time determined in this way. The landing timing of the subsequent ink is determined by the distance between the head that ejects the preceding ink and the head that ejects the subsequent ink, the relative movement speed of the head and the recording material, and the time difference between the ejection timing of the preceding ink and the ejection timing of the subsequent ink. The preceding ink droplets and the succeeding ink droplets may contact as liquid even if only a part thereof, and the landing centers of the preceding ink droplet and the succeeding ink droplet do not have to coincide.

The recording medium suitable for forming an image by attaching the above ink is plain paper, high-quality exclusive paper, glossy paper,
A glossy film, a postcard or the like can be used.

[0018]

EXAMPLES An example of the ink set recording apparatus of the present invention suitable for recording using the above-described ink set of the present invention will be described below.

FIG. 1 is a front view showing an outline of an ink jet head unit included in an ink jet recording apparatus according to an embodiment of the present invention. A plurality of long inkjet print head units 1-1 to 1-4 are used as a medium 1-5.
It is arranged across the entire width of. Each head unit ejects black (K), cyan (C), magenta (M), and yellow (Y) ink, respectively. A control signal or the like is sent to the print head via a flexible cable (not shown). Plain paper, high-quality special paper, glossy paper,
The printing material 1-5 such as a glossy film and a postcard is nipped by a conveyance roller discharge roller and the like (not shown), and is fed in the arrow direction (main scanning direction) in accordance with the driving of the conveyance motor.

FIG. 2 is a schematic view of a two-row head unit that can be used in at least one of the ink jet head units shown in FIG. This two-row head unit consists of two rows of nozzles (ejection ports) that eject ink of the same color,
An ink supply tube (not shown) is connected to each of them, and inks of the same color, the same concentration and different surface tensions are supplied.

A heating element (electrical / thermal energy converter) that generates thermal energy for ink ejection is provided inside the ink ejection port (liquid path) constituting the nozzle rows 2-1 and 2-2. ing. An image can be formed by driving these heating elements based on a recording signal to cause ink droplets to fly and adhere onto the printing material. In the present invention, the ink having a low surface tension is used for the nozzle row 2-1 and the ink having a high surface tension is used for the nozzle row 2-2, and the ink is ejected from the ejection port of the nozzle row 2-1 for the first pixel. And the pixels of the same color adjacent thereto are formed in the nozzle row 2
-2 are ejected from the ejection port so that the two pixels are adjacent to each other. In the head shown in FIG. 2, the nozzles in the nozzle row 2-1 are displaced so that the nozzles in the nozzle row 2-2 are positioned between the two nozzles in the nozzle row 2-1 (the straight line formed by the nozzles in the nozzle row 2-1 and the nozzles in the nozzle row 2-2 is With the arrangement having (which does not coincide with the main scanning direction), it is easier to form adjacent pixels.

This recording device incorporates control means for forming adjacent pixels of the same color. This control means can be configured using a known control means. At that time, all or part of the ink droplets initially applied remain on the recording medium and are not fixed, and adjacent pixels are formed by ink droplets of the same color and the same density. It is preferable to control so as to mix and form adjacent pixels. By such an ink drop attachment process, it is possible to effectively prevent the phenomenon that ink overflows from a predetermined pixel area,
Further, it is possible to shorten the fixing time while preventing feathering and strike-through.

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded.

The ink recorded in advance was prepared by the usual method with the following composition (mass basis). 1,5-Pentanediol 8.3% Trimethylolpropane 8.0% 2-Pyrrolidone 6.4% Ammonium gluconate 2.0% Coloring material 4.4% Ion-exchanged water The following coloring materials were used. . Black: Projet Fast Black 2 (Zene
CA company) Yellow: Projet Fast Yellow 2 (Zene
CA company) Magenta: Projet Fast Magenta 2 (Zene
CA) Cyan: Projet Fast Cyan 2 (Zenec)
Company a) The surface tension of these inks was 26 to 29 dyn / cm as a result of measurement with a Wilhelmy surface tensiometer.

Further, the ink to be recorded subsequently was adjusted with the following composition (based on mass). Glycerin 5.0% Ethylene glycol 5.0% Urea 5.0% Isopropyl alcohol 5.0% Sodium gluconate 2.0% Coloring material 4.4% Ion-exchanged water The remaining coloring material is the ink recorded before. The same one was used.

The surface tension of these inks was measured by the same method as the above-mentioned ink, and was found to be 46 to 49 dyn / cm.
Met.

Using the ink obtained as described above,
Recorded.

As a result of carrying out such recording, there was no overflow of the image portion formed by the two types of ink, and recording with good fixability was achieved.

[0029]

As described above, according to the present invention,
It is possible to perform recording while keeping the image quality relatively high while giving priority to the fixing time.

[Brief description of drawings]

FIG. 1 is a front view showing an outline of an inkjet recording apparatus according to an embodiment of the present invention.

FIG. 2 is a detailed view of one head unit.

[Explanation of symbols]

1-1, 1-2, 1-3, 1-4 Inkjet head unit 1-5 Medium 2-1 2-2 Nozzle row

Claims (5)

[Claims] 1. An image forming method for forming an image by applying ink as a droplet to a recording medium to form a pixel, wherein the ink droplets of the same color and the same concentration having different surface tensions are recorded in order of increasing surface tension. An image forming method comprising the step of forming adjacent pixels of the same color by applying to a medium. 2. Mixing of ink between these ink droplets by applying the next ink droplet for forming a pixel adjacent to the pixel before the pixel formed by the ink droplets attached to the recording medium is fixed. The image forming method according to claim 1, wherein 3. An ink jet device having a recording head provided with an ejecting section for ejecting ink, wherein first ink ejecting ink having a lower surface tension of two kinds of ink having different surface tensions and having the same density and the same density. Part and one or more combinations of the second ejection portion that ejects ink having a higher surface tension, ink droplets ejected from the first ejection portion, and ink droplets ejected from the second ejection portion. And a control means that controls the pixels formed from these ink droplets to be adjacent to each other by applying the above-mentioned to the recording medium in order from the lowest surface tension. 4. The ink droplet is mixed between these ink droplets by applying the next ink droplet for forming a pixel adjacent to the pixel before the pixel is fixed by the ink droplet adhered to the recording medium. The ink jet recording apparatus according to claim 3, wherein the ink jet recording apparatus is controlled to generate 5. The image according to claim 1, wherein in an ink set having a plurality of inks for at least one color, a plurality of inks of the same color and the same density include two or more inks having different surface tensions. An ink set characterized by being used in a forming method.