Incremental printing of symbolic information – Ink jet – Fluid or fluid source handling means
Reexamination Certificate
2003-04-17
2004-09-07
Shah, Manish (Department: 2853)
Incremental printing of symbolic information
Ink jet
Fluid or fluid source handling means
C347S100000, C347S101000, C347S105000
Reexamination Certificate
active
06786586
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a high-speed ink-jet recording method using so-called plain paper having no extra coating layer with an ink of at least one color containing a pigment as a colorant.
2. Description of the Related Art
The ink-jet recording method has such characteristics that color recording can be conveniently carried out, the consuming energy is small, recording noise is small, and the production cost of printers can be suppressed. Owing to the characteristics, the ink-jet recording method is being widely used in offices, and there are increasing occasions where it is used in combination with an electrophotographic recording apparatus, such as laser printer and duplicators.
A recording medium (recording paper) is used in the ink-jet recording method, for example, so-called plain paper, coated paper for ink-jet recording, glossy paper, a white film and a transparency. Particularly, in the case where the ink-jet printer is used in combination with a laser printer and a duplicator in offices, such occasions are the most frequent that the ink-jet recording is applied to plain paper, which has high compatibility with an electrophotographic recording apparats and is available at low cost. Therefore, it is considerably important in the ink-jet recording method to improve recording suitability to plain paper. However, the following problems arise upon printing on plain paper by the conventional ink-jet recording method.
1. The so-called feathering phenomenon occurs, in which an ink flows along fibers of paper. The feathering phenomenon considerably impairs image quality, particularly characters.
2. In general, so-called plain paper is subjected to sizing (water repellency) on the surface thereof. Therefore, absorption of an ink is delayed to cause intercolor breed (ICB) at a part where different colors are in contact with each other.
3. Because the absorption of an ink is delayed due to sizing (water repellency) on the surface of the paper, the back surface of the document is stained upon stacking after printing.
4. A colorant contained in an ink is difficult to remain on the surface of plain paper, and thus, in particular, the coloring property is insufficient.
Along with the penetration of an ink-jet printer into the business market in recent years, the printing speed of the ink-jet printer is intended to be increased to a level equivalent to a laser printer, but the ink absorption cannot be improved with maintenance of image quality.
In order to solve the problems, in JP-A-10-166713, a cationic sizing agent is used, and the Stöckigt sizing degree of base paper is defined. However, the Stöckigt sizing degree herein is remarkably low as from. 3 to 7 seconds to fail to provide an effect of suppressing irregular penetration of an ink, and thus the feathering phenomenon becomes remarkably conspicuous upon using an ink having high permeability, such as those used for high-speed printing.
In JP-A-2000-94825, high-speed printing and prevention of the feathering phenomenon are simultaneously attained by using a combination of recording paper having a dissociative polyvalent metallic salt coated on the surface of base paper in an amount of from 0.1 to 2.0 g/m
2
and a pigment ink having an acid value of from 30 to 300 mgKOH/g and a surface tension of from 30 to 45 mN/m. However, prevention of the feathering phenomenon and improvement in density can be realized by attaining such an effect that the pigment contained in the ink is aggregated to make coarse grains on the surface of the recording paper irrespective to the species of the metallic salt and the polymer. Therefore, in the case where the coating material coated on the base paper penetrated into the base paper, there is a less effect of aggregating the pigment even though the coated amount is in the defined range to fail to obtain an improving effect of image quality.
SUMMARY OF THE INVENTION
The invention has been developed to solve the problems associated with the conventional art.
The invention is to provide such an ink-jet recording method in that upon carrying out printing at a high speed as equivalent to laser printers by using the so-called plain paper, the optical density and the coloring property of the image are high with less occurrence of intercolor breed and feathering, and the image has high water resistance.
As a result of earnest investigations made by the inventors on the problems, it has been found that the number of coarse particles of a pigment contained in an ink immediately after contacting with the surface of the recording paper is an important factor on image quality. More specifically, it has been found that in the case where the number of the pigment having a particle diameter of 1 &mgr;m or more contained in the ink after contacting the surface of the recording paper is 5 time or more the number of the pigment having a particle diameter of 1 &mgr;m or more contained in the ink before contacting the surface of the recording paper, the pigment dots not flow out along with a vehicle but remains on the surface of the recording paper even at a high absorption rate of the ink, and thus sharp printing can be carried out at a high speed.
The ink-jet recording method of the invention contains, as one aspect, a step of printing on recording paper having base paper mainly containing pulp fibers and a filler by using a pigment ink of at least one color at a scanning speed of a printing head of 25 cm/sec or more and a maximum ink injection amount in a range of from 6 to 30 mL/m
2
, the pigment ink having a surface tension in a range of from 20 to 35 mN/m, and an aggregation degree of a pigment contained in the pigment ink in contact with a surface of the recording paper being 5 or more.
The ink-jet recording method of the invention contains, as another aspect, a step of printing on recoding paper having base paper mainly containing pulp fibers and a filler by using a pigment ink of at least one color at a conveying speed of the paper of 6 cm/sec or more with a printing head being fixed and a maximum ink injection amount in a range of from 6 to 30 mL/m
2
, the pigment ink having a surface tension in a range of from 20 to 35 mN/m, and an aggregation degree of a pigment contained in the pigment ink in contact with a surface of the recording paper being 5 or more.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The invention will be described in detail below.
The ink-jet recording method of the invention in one aspect contains a step of printing on recording paper having base paper mainly containing pulp fibers and a filler by using a pigment ink of at least one color at a scanning speed of a printing head of 25 cm/sec or more and a maximum ink injection amount in a range of from 6 to 30 mL/m
2
. The pigment ink has a surface tension in a range of from 20 to 35 mN/m, and an aggregation degree of a pigment contained in the pigment ink in contact with a surface of the recording paper is 5 or more.
The ink-jet recording method of the invention in another aspect contains a step of printing on recording paper having base paper mainly containing pulp fibers and a filler by using a pigment ink of at least one color at a conveying speed of the paper of 6 cm/sec or more with a printing head being fixed and a maximum ink injection amount in a range of from 6 to 30 mL/m. The pigment ink has a surface tension in a range of from 20 to 35 mN/m, and an aggregation degree of a pigment contained in the pigment ink in contact with a surface of the recording paper is 5 or more.
The recoding paper in the invention will be firstly described.
In the recording paper in the invention, base paper mainly containing pulp fibers and a filler is used. The base paper is formed with such pulp as chemical pulp, e.g., hardwood bleached craft pulp, hardwood non-bleached craft pulp, softwood bleached craft pulp, softwood non-bleached craft pulp, hardwood bleached sulfite pulp, hardwood non-bleached sulfite pulp, softwood bleached sulfite pulp and softwood non-bleached sulfite pulp, and pulp produ
Hosoi Kiyoshi
Koga Chizuru
Ogino Takashi
Fuji 'Xerox Co., Ltd.
Shah Manish
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