Incremental printing of symbolic information – Ink jet – Fluid or fluid source handling means
Reexamination Certificate
2001-12-11
2003-06-03
Nguyen, Lamson (Department: 2853)
Incremental printing of symbolic information
Ink jet
Fluid or fluid source handling means
C347S096000, C347S098000, C347S101000, C106S031600
Reexamination Certificate
active
06572227
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ink-jet recording method, in which an image is recorded by ejecting an ink from a nozzle, and an apparatus for ink-jet recording.
2. Description of the Related Art
The fundamental of the ink-jet recording method is that a liquid or molten solid ink is ejected from a nozzle, a slit or a porous film to carry out recording on a recording material, such as paper, cloth or a film. The ink-jet recording method has such advantages that an apparatus therefor is small and inexpensive and is excellent in quietness, and monochrome printers for black color and full color printers are widely available on commercial base. Among these, a so-called piezo ink-jet method using a piezoelectric device and a thermal ink-jet method carrying out recording by forming droplets by acting thermal energy have large number of advantages, such as high speed printing and high resolution.
An ink used in the ink-jet recording apparatus is demanded to have the following characteristics:
(1) A uniform image having high resolution and high density can be obtained on paper without causing bleeding and fogging.
(2) Clogging due to drying of the ink does not occur at a tip end of the nozzle, and the ejection responsiveness and the ejection stability are good at all times.
(3) The drying property of the ink in the form of an image is high.
(4) The resulting image is excellent in durability.
(5) The long-term storage stability is high.
The drying property of the ink on a recording material is being important associated with speeding up of the ink-jet recording system. In order to realize the drying property, for example, Japanese Patent Laid-Open No. 116522/1994 discloses an ink containing a pigment, a water soluble resin and an acetylene glycol series surfactant, and Japanese Patent Laid-Open No. 287837/1998 discloses an ink containing a self-dispersible pigment and an acetylene glycol series surfactant. These techniques realize excellent dry property by adding to an ink a substance imparting permeability to paper.
However, in the case where the permeability imparting substance is added to an ink, blue occurs at an edge part of a letter, a line and a solid image, and thus sufficient image quality is difficult to be obtained. Furthermore, a large amount of a colorant is permeated in paper to cause such a problem that the optical density of the image is reduced.
In order to prevent the reduction of the optical density of the image, it can be easily expected to increase the concentration of the colorant in the ink. However, in the case where the colorant concentration in the ink is increased, and a dye is used as the colorant, sufficient performance cannot be obtained for water resistance and light resistance although a high optical density can be obtained. In the case where a pigment excellent in light resistance and water resistance is used as the colorant, such problems occur that (1) clogging is liable to occur with the ink at the tip end of the nozzle of the ink-jet recording apparatus, and (2) the optical density is widely fluctuated depending on the species of paper, and there are some kinds of paper that suffer large decrease in density. Therefore, it is practically difficult to use as an ink for the ink-jet recording method.
The reasons of the problems are considered as follows. With respect to the problem (1), because the pigment is insoluble in water, the dispersion stability of the pigment in the ink is liable to be broken when water in the ink is evaporated at the tip end of the nozzle, whereby the ink is liable to clog the tip end of the nozzle. With respect to the problem (2), because species and amount of a surface additive and the state of entanglement of fibers are largely different depending on the kind of paper, the colorant does not remain on the surface of the paper but is excessively penetrated into the paper in some cases depending on the combination of the aggregation rate and the aggregated state of the pigment in the ink the paper with the paper characteristics. The fluctuation in density among the kinds of paper is peculiar in the case where a pigment is used as the colorant, but an ink using a dye as the colorant does not cause severe problems in fluctuation of density although the problems described in the foregoing occur. It is considered that this is because in the case of the dye ink, the colorant itself dyes the surface of paper.
SUMMARY OF THE INVENTION
Therefore, the invention is to provide an ink-jet recording method and an apparatus for ink-jet recording in that bleeding at an edge part does not occur, sufficient water resistance and light resistance are attained, an image that is excellent in fixing property and has small fluctuation in optical density depending on paper can be obtained, and by using an ink for ink-jet recording that is difficult to cause clogging due to drying of the ink for ink-jet recording at a tip end of a nozzle, various characteristics that are demanded in a resulting recorded image are balanced on a higher level.
As a result of various earnest investigations by the inventors, it has been found that according to an ink-jet recording method using an ink for ink-jet recording that satisfies the characteristics described later, such an image can be obtained that is excellent in drying property on plain paper, has a sufficient optical density on plain paper, exhibits less fluctuation in optical density depending on paper, has sufficient water resistance and light resistance, causes less blue at edge parts of a line, a letter and a solid image, and is excellent in fixing property. Thus, the invention has been completed.
The invention relates to, as one aspect, an ink-jet recording method using an ink for ink-jet recording containing at least, as essential components, a pigment self-dispersible in water, a water soluble organic solvent and water, and carrying out printing with an amount of the ink of 20 ng or less per one droplet, the ink for ink-jet recording satisfying the following conditions (a) to (c):
(a) a dynamic contact angle upon dropping 4 &mgr;L of the ink for ink-jet recording on plain paper is about 60° or less after one second from dropping;
(b) a volume average particle diameter mv of dispersed particles of the pigment in the ink for ink-jet recording is about from 150 nm to 250 nm; and
(c) in the dispersed particles of the pigment in the ink for ink-jet recording, number of particles having a particle diameter of from 0.5 &mgr;m to 5 &mgr;m is about from 25×10
4
to 2,000×10
4
per microlitter, and a number of particles having a particle diameter of 5 &mgr;m or more is about 100 per microlitter or less.
In the ink-jet recording method of the invention, it is possible that the dynamic contact angle upon dropping 4 &mgr;L of the ink for ink-jet recording on plain paper is about 50° or less after one second from dropping.
In the ink-jet recording method of the invention, it is possible that a concentration of the pigment in the ink for ink-jet recording is about from 3% to 20% by mass.
In the ink-jet recording method of the invention, it is possible that a ratio of the volume average particle diameter mv to a number average particle diameter mn (mv/mn) of the dispersed particles of the pigment in the ink for ink-jet recording is about 3.2 or less.
In the ink-jet recording method of the invention, it is possible that printing of droplets of the ink is carried out at a driving frequency of about 15 KHz or more.
In the ink-jet recording method of the invention, it is possible that the ink for ink-jet recording further contains a nonionic surfactant.
In the ink-jet recording method of the invention, it is possible that the ink for ink-jet recording further contains a dye.
The invention relates to, as another aspect, an apparatus for ink-jet recording containing a transporting unit for transporting a recording material, an ink-jet recording head recording an image on the recording material transported by the transporting unit by ejecting an ink at an am
Suzuki Atsushi
Yamashita Kunichi
Yui Toshitake
Fuji Zerox Co., Ltd.
McCormick Paulding & Huber LLP
Nguyen Lamson
Shah Manish
LandOfFree
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