Photocopying – Using microcapsules
Reexamination Certificate
1999-09-29
2001-12-11
Adams, Russell (Department: 2851)
Photocopying
Using microcapsules
C355S401000, C355S402000, C355S405000, C430S091000, C430S096000, C430S106100, C430S138000, C430S151000, C430S170000, C359S296000, C345S107000
Reexamination Certificate
active
06330054
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for forming an image on a recording medium based on the use of microcapsules including chargeable particles which are movable in a dispersion medium in accordance with an applied electric field. The present invention also relates to an image-forming apparatus for forming an image on the recording medium as described above.
2. Description of the Related Art
A variety of display systems have been hitherto known for displaying, for example, images and character information to effect visualization, including, for example, the CRT (Cathode Ray Tube) system as well as the liquid crystal system, the plasma light emission system, and the EL (electroluminescence) system.
In recent years, various electronic devices have been miniaturized in accordance with the rapid progress of the semiconductor technology. Accordingly, the display device is also required to realize, for example, a small size, a light weight, a low driving voltage, a small amount of electric power consumption, and a thin flat panel.
In response to the demand as described above, a variety of types of flat panel type electronic display devices have been suggested and practically used, including, for example, those of the light emission type represented by PDP (Plasma Display Panel) and those of the light-receiving type represented by LCD (Liquid Crystal Display). Especially, in recent years, the reflective type LCD has been vigorously studied in view of the fact that it consumes a small amount of electric power.
The reflective type LCD has, for example, the following merits. That is, it is possible to realize, for example, a small size, a light weight, a low driving voltage, a small amount of electric power consumption, and a thin flat panel. Further, the reflective type LCD easily conforms to the eye under an ordinary light source in the same manner as in printed matters, and it has a display quality involving no influence of external light.
However, even when the reflective type LCD is constructed by combining a guest-host liquid crystal with a TFT panel, it is merely possible theoretically to obtain an image having a reflectance of 66% and a contrast ratio of 5:1.
Such an image extremely resembles an image of newspaper having a reflectance of 57% and a contrast ratio of 5:1, and it is far from an image quality possessed by a calendar and an output image obtained by a laser printer having a reflectance of 80% and a contrast ratio of 21:1. A problem arises in that such an image is difficult to be seen.
Further, LCD has no memory function. For this reason, the image display cannot be maintained when the control electric field is cut off. It is necessary to continuously apply the stimulation such as an electric field to the display surface from the outside during the period in which the image is displayed. Therefore, LCD involves the problem in that it is difficult to be used, and it is disadvantageous in an economical viewpoint.
A first object of the present invention is to provide an image-forming method and an image-forming apparatus which has memory effect and excellent reflectance and contrast ratio.
A second object of the present invention is to provide an image-forming method and an image-forming apparatus which make it possible to avoid the decrease in recording density and the blur and realize appropriate rewriting when the recording information is rewritten on a recording medium including microcapsules.
SUMMARY OF THE INVENTION
According to a first aspect of the present invention, there is provided an image-forming method for forming an image on a recording medium including microcapsules containing chargeable particles dispersed in a dispersion medium in the microcapsules, the method comprising the steps of:
applying, to the recording medium, energy for dispersing the chargeable particles in the dispersion medium in the microcapsules before forming the image; and
applying, to the recording medium, a control electric field having a polarity corresponding to recording information to electrophorese the chargeable particles in a predetermined direction in the microcapsules so that the image is formed thereby.
A recording medium is known, which is based on the use of microcapsules including chargeable particles dispersed in a dispersion medium in the microcapsules. A control electric field is applied in a specified direction to the microcapsules to electrophorese the chargeable particles in the specified direction. Accordingly, image information can be recorded (formed) on the recording medium. The chargeable particles are still localized at predetermined positions in the microcapsule even when the control electric field is cut off. Therefore, the recording medium has the so-called memory effect.
The present inventors have found out the following problem. That is, if there is a certain degree of time interval after the image information is recorded on the recording medium until the next recording (rewriting) is performed, then the chargeable particles in the microcapsule adhere to the wall surface of the microcapsule, or the chargeable particles cause mutual adhesion. As a result, the recording (display) density is lowered and any halation or blur occurs on the screen on which the next recording is performed.
According to the method of the present invention, the energy such as electric field is applied to the microcapsules of the recording medium before a new image is formed on the recording medium on which the image information has been once formed, i.e., before the image is rewritten. By doing so, the chargeable particles are separated from the wall surfaces of the microcapsules and from the other chargeable particles to enable the chargeable particles to perform free electrophoresis. Accordingly, the chargeable particles can be dispersed in the dispersion medium in the microcapsules. The response performance is improved with respect to the control electric field which is used when the image is rewritten. Further, the recording (display) density is increased, and the blur is reduced as well.
The energy may be energy necessary to freely electrophorese the chargeable particles localized in the microcapsules by means of the control electric field. The energy may be heat, electromagnetic wave, magnetic field, electric field, or ultrasonic wave. When the magnetic field, for example, an alternating magnetic field is used as the energy, magnetic fine particles may be contained in the chargeable particles.
In order to enhance the dispersion performance of the chargeable particles, it is desirable to use an alternating electric field as the electric field applied to the microcapsules. The voltage waveform for applying the alternating electric field may be a waveform selected from the group consisting of a rectangular wave, a sine wave, and a triangular wave. Especially, it is desirable to use the rectangular wave.
The recording medium may include a flexible sheet for coating the microcapsules thereon, and the chargeable particles may include particles to be positively charged in the dispersion medium and particles to be negatively charged in the dispersion medium. The chargeable particles may be composed of white particles and black particles. Alternatively, the chargeable particles may be composed of a group of color particles of the three primary colors.
According to a second aspect of the present invention, there is provided an image-forming apparatus for forming an image on a recording medium including microcapsules containing chargeable particles dispersed in a dispersion medium in the microcapsules, the apparatus comprising:
an alternating electric field-applying unit for applying an alternating electric field to the microcapsules; and
a control electric field-applying unit for applying, to the microcapsules, a control electric field having a polarity corresponding to recording information.
The alternating electric field-applying unit of the image-forming apparatus according to the present invention makes it possible to all
Adams Russell
Brother Kogyo Kabushiki Kaisha
Brown Khaled
Oliff & Berridg,e PLC
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