Education and demonstration – Means for demonstrating apparatus – product – or surface... – Chalkboard or equivalent means having easily erasable surface
Reexamination Certificate
2001-01-25
2003-07-01
Banks, Derris H. (Department: 3712)
Education and demonstration
Means for demonstrating apparatus, product, or surface...
Chalkboard or equivalent means having easily erasable surface
C428S402000
Reexamination Certificate
active
06585523
ABSTRACT:
TECHNICAL FILED OF THE INVENTION
The present invention relates to a magnetic material-inverting display panel which forms a display by inverting magnetic display material with a magnet and erasing the display by inverting the materials with a magnet from the same side. More precisely, it relates to a magnetic material-inverting display panel wherein a magnetic display material having magnetic poles of opposite signs tinged with different colors by placing an opaque thin metal layer on one surface and making the color of another surface different from that of the thin metal layer of one surface.
BACKGROUND OF THE INVENTION
In a prior magnetic display panel, fine particles of a magnetic material are dispersed into a dispersion. A display was formed by migrating the magnetic particles to a surface of the panel at which a magnet is operated. The display was erased through precipitation of the magnetic particles by operating a magnet from the opposite surface. This type of the magnetic display panel had a drawback that the apparatus becomes complex and large since erasure of a display should be carried out from backside of the panel. In addition, when said magnetic particles were migrated to the display panel, it was difficult to erase only unnecessary part of the display.
Furthermore, Japanese Patent Publication No. 59-32796/1984, which is incorporated herein by reference, proposes a magnetic display panel which realizes a display by inverting display magnetic particles. The panel uses a liquid dispersion dispersed with magnetic particles having a residual magnetic moment of 0.2 to 10 emu/g and a coercive force of not less than 500 oersteds, and having a yield value of not less than 5.0 N/m
2
.
SUMMARY OF THE INVENTION
The panel, however, had suffered from problems of a low contrast and an unclearness owing to insufficient inversion even when a display was formed by inverting magnetic particles or the display was erased.
The purpose of the present invention is to provide a magnetic material-inverting display panel which improves clearness of a display and its erasure of the panel, the display being formed by inverting magnetic display material. In particular, a liquid dispersion in a display panel has a yield value and contains a magnetic display material in fine particle form having magnetic poles of opposite signs tinged with different colors by providing an opaque thin metal layer on at least one surface and making the color of another surface different from that of the thin metal layer of the one surface, the dispersion also includes a dispersion medium and a thickener as other main components and is supported by a support. A ratio between the inner volume V of the support supporting the liquid dispersion and the volume W of the magnetic display material in fine particle form is W/V×100=1 to 17%. Total area of S-pole-surfaces or N-pole-surfaces of the magnetic display material in fine particle form to be dispersed in a liquid dispersion of the panel is from 60% to 1500% of the display surface area of the display panel.
PREFERRED EMBODIMENTS OF THE INVENTION
The magnetic display material to be used in the present invention is a magnetic material having magnetic poles of opposite signs tinged with different colors by placing an opaque thin metal layer on one surface and making the color of another surface different from that of the thin metal layer of one surface. The magnetic material is inverted by the action of magnetism to form a display. For example, when the display surface of the panel is swept with S-pole of a writing magnet, N-pole surfaces of the magnetic material is arranged at the panel surface to make it N-pole color. Upon writing the surface with N-pole of the magnetic pen, the magnetic material is inverted and S-pole surface appears to form a display of the color. When the panel is again swept with S-pole of the magnetic pen, the materials are inverted and the display disappears, whereby display having a color of the metal and a color of the magnetic material is obtained.
In the present invention, the ratio between the inner volume V of the support supporting the liquid dispersion and the volume W of the magnetic display material in fine particle form should preferably be W/V×100=1% to 17%. When the ratio is smaller than 1%, a display tends to be unclear owing to the small amount of the display material, and, when the ratio exceeds 17%, smooth inversion tends to be difficult owing to mutual interference of the display material at the inversion. The same volume ratio is preferred in the cases where the magnetic display material is conteined in a honeycomb cell or a capsule. The ratio between the inner volume V of a unit cell or a unit capsule and the volume W of the magnetic display material therein should also preferably be W/V×100=1% to 17%.
Furthermore, in the present invention, the total surface area of S-poles or N-poles of the magnetic display material should be from 60% to 1500% of the display surface area of the display panel for realizing a clear display.
The display surface area of the display panel means the area of the flat surface for displaying as a display panel containing a liquid dispersion in which the magnetic display material is dispersed.
The present inventors have discovered that one of the reasons of unclear display of the earlier magnetic material-inverting display panel is improperness of the surface area of S-poles or N-poles of the magnetic material for displaying relative to the display surface area of the panel. Another reason is insufficient inversion of the magnetic material.
When the surface area of S-poles or N-poles of the magnetic material for displaying is smaller than 60% of the display surface area of the panel, the displayed color tends to be pale and color difference between the displayed color and the color of the background support tends to be small, so that the contrast becomes low and the resulting display becomes unclear.
On the other hand, when the surface area exceeds 1500%, owing to too much degree of mutual interference of magnetic material, the inversion tends to be difficult to result in occurrence of an uninverted material, a material showing boundary surface between the S-pole and the N-pole, and the like, so that the resulting display has a mixed color thereof and a clear display cannot be formed.
The liquid dispersion in which the magnetic display material is dispersed must have a specific yield value and viscosity. The yield value is necessary for properly dispersing the magnetic display material in the liquid dispersion, inverting it properly by magnetism, and preventing their precipitation. The viscosity is required for inverting only the part exposed to magnetism when the display panel is exposed to magnetism. Namely, it is preferred that the liquid dispersion has a yield value of 0.15 to 7.5 N/m
2
and a viscosity of 3 to 350 mPa·s. As a thickner for imparting a yield value, an inorganic substance such as AEROSIL can be used. Inorganic thickners, however, have drawbacks that the viscosity and the yield value change with a lapse of time. To the contrary, an organic thickner selected from fatty acid bisamides, hydrogenated castor oil, and amides of N-acylamino acids is preferable owing to advantages that they impart a yield value, and the viscosity and the yield value hardly change with a lapse of time.
In the case that the liquid dispersion has a yield value and a viscosity of out of the ranges of 0.15 to 7.5 N/m
2
and 3 to 350 mPa·s respectively, although the yield value and the viscosity are still acceptable, stability in maintenance of the formed display tends to be deteriorated and, owing to assembly of surrounding magnetic material at writing with a magnetic pen, distribution of the magnetic material tends to be inhomogeneous, so that the color of periphery of a display formed through inversion and the color of background of the display formed by an uninverted magnetic material at the surrounding part of the display tends to change. As a result, the display tend
Ikeda Masahiko
Misawa Hideki
Tokunaga Masami
Yokoyama Takeo
Banks Derris H.
Kabushiki Kaisha Pilot
Miller Bena B.
LandOfFree
Magnetic material-inverting display panel does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Magnetic material-inverting display panel, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Magnetic material-inverting display panel will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3023872