Incremental printing of symbolic information – Ink jet – Fluid or fluid source handling means
Reexamination Certificate
1994-01-19
2002-06-11
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Fluid or fluid source handling means
Reexamination Certificate
active
06402314
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a coating material for coating on the surface of a recording medium used in the inkjet recording method, and more particularly to an inkjet recording apparatus for recording ink on a recording medium coated with such coating material.
The inkjet recording method is a method of recording information where small drops of ink are generated and applied onto a recording medium, such as paper, and all or a portion of the ink is adhered on the recording medium by means of the ink discharge method, such as a sucking system by electrostatic power, a system in which mechanical vibration or displacement is given to the ink with piezoelectric elements, and a system utilizing pressure where the pressure is generated by heating the ink to form bubbles. The inkjet recording method is associated with high speed and high quality multi-color recording.
In the inkjet recording method, in order to avoid an inferior recording quality due to bleeding and/or flowing of adhered ink on the recording medium, a specialized recording medium is used. For example, the recording medium is a specially coated paper on which a layer of inorganic pigment is coated which provides a larger amount of water absorption and color constituent absorption contained in the ink. Alternatively, the recording medium has a special film on which the surface is specially processed for ink-flow resistivity.
In the foregoing prior art recording medium, there exists a problem that without such specialized and limited type of recording medium, a higher quality of recording is not maintained in the inkjet recording method. That is, when users who handle the prior art inkjet recorders misuse the recording medium, they encounter problems in that they fail to achieve high quality recording because of bleeding of the ink and in that fatal contamination occurs within the printing mechanism and the recorder because of flowing of the ink.
Moreover, the high cost of the recording medium because of special processing and/or special materials required poses another problem.
In the inkjet recording method, where the ink is particularized into droplets and discharged from nozzles of a recording head onto the recording medium such as a recording paper, etc., and characters, drawings, etc., are printed on the recording medium, it is required that the particularized ink droplets to be discharged from nozzles of the recording head should be about 30 &mgr;m in diameter with homogeneity in size and shape, and that such ink droplets be discharged onto the recording medium constantly and regularly to form an image with a dot array of ink drops. But in order to satisfy the foregoing fundamental functional requisites during practical usage, the inkjet recording apparatus should be free from such problems peculiar to the inkjet recorder as, for example, clogging at orifices of nozzles due to caking of the ink, change in viscosity of the ink due to change in atmospheric temperature and humidity, deterioration of the quality of the ink with age in longer term stock, and evaporation of ink solvent at the ink supply system. Therefore, the selection and design of the ink for the inkjet recorder should be optimized, taking with integrity into account, for example, the recording head, the ink supply system, the recording media, and the head driving condition.
Under the foregoing conditions, two kinds of inks, water base and oil base ink, according to solvent classification, are in use for the inkjet recorders for output devices and for computers and office automation equipment. The main characteristics of water base and oil base ink are as follows: the water base ink has higher stability in discharge due to stronger surface tension and has, therefore, higher selectivity and chemical stability in/with materials for an ink tank and other components for the ink supply systems which have direct contact with the ink. The oil base ink has higher selectivity in and better fixability on the recording media such as a paper and better water resistant property after the recording. However, a vital feature considered in selecting the type of ink is the safety to the human body as a result of its flammable and odor characteristics. For this reason, a water base ink has been widely used.
Since water base ink is discharged through a very fine orifice (approximately 20-50 &mgr;m in diameter) which is formed as a hole on the recording head nozzle, its principle components are water soluble dye, such as direct dye and acid dye, different from the printing ink in general use, and water which is the principle solvent. Additional components, such as miscellaneous additive(s), if necessary, may be added. The percentage of water in the water base ink, in practical use, is approximately 80% and the ink discharged through the nozzle of the recording head is fixed to the recording medium through a drying process, usually air drying.
Since the water base ink applied during prior art inkjet recording usually has a high percentage of water, most of the duration time from its discharge through the recording head nozzle until anchoring to the recording medium is for evaporation of the water as the principal component. Atmospheric temperature and humidity affects, of course, the duration of the evaporation and it depends sometimes on the types (and materials) of the recording medium. The length of the duration of evaporation, in turn, reflects directly on the duration time of the image production and quality of image on the recording medium. A plain paper is commonly used as the recording medium. When plain paper is used as the recording medium according to the common usage, a longer duration of time is needed for absorption and drying of the ink.
Since humidity on parts of the plain paper spreads over the surface thereof due to delay in absorption and drying, bleeding, waving, wrinkling, etc., on the paper remarkably increase on the plain paper and blotting is apt to occur due to friction between a feeding roller and the undried ink which is undergoing the drying process. Therefore, an inferior quality image results on the plain paper in prior art inkjet recording.
SUMMARY OF THE INVENTION
An object of the present invention is to obtain high quality images during inkjet recording without regard to the type of recording medium used, and to provide an inkjet recorder free from contamination, e.g., inside of the recorder due to flow of the recording ink.
Another object of the present invention relates to an economical coating material for the recording medium for the purpose of inkjet recording with higher quality without regard to the type of recording medium used.
Yet another object of the present invention relates to obtaining high speed and high quality fixing of the ink with stability on the recording medium by shortening the drying time of the ink during inkjet recording by evaporating or drying water which is brought to the recording medium through the discharged ink, as well water which is excessively contained in and/or adhered to the recording medium at the time of inkjet recording.
In order to solve the problems in the conventional art, the inkjet recorder of the present invention provides coating means which coats the coating material upon the recording medium before the recording ink is recorded on the recording medium, the inkjet recorder recording an image on the recording medium by discharging the recording ink according to a recording signal.
Moreover, the coating material according to the present invention, which is coated on the recording medium before the ink is recorded on the recording medium, comprises polyvinyl alcohol which is saponified partially and has a degree of saponification of 60% to 97.5%, or polyvinyl alcohol which is saponified completely having a degree of saponification of 97.5% or more.
The composition formula of polyvinyl alcohol is:
This product is made chemically through hydrolysis of polyvinyl acetate of which composition formula is:
A portion or all of the COOR group in the polyvinyl acetate tha
Ikeno Hiroshige
Sato Katsuhiko
Sato Tatsuru
Shiraishi Masayoshi
Adams & Wilks
Barlow John
Huffman Julian D.
Seiko Instruments Inc.
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