US 6,284,352 B1Granted

Ferrofluidic electric paper

AssigneeXerox Corporation

InventorsDavid Kalman Biegelsen, Warren Bruce Jackson

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Abstract

A low cost, reusable electric paper that uses ferrofluidic colored fluids and an external magnetic writing instrument. The paper can be formed from laminated rolls of polymeric media that are roller die cut, inked, aligned, bonded and cut to an appropriate size. The paper is formed from layers that define a hidden reservoir and a visible reservoir for each of an array of print cells that form a grid on the paper. A ferrofluidic coloring fluid is permanently contained within the paper and can move from the hidden reservoir to the visible reservoir. The size of the cells define the resolution of the paper. Initially, the paper appears white. However, after passing a writing instrument, such as a stylus, over desired print cells, these cells switch from a first hidden bistable state to a second visible bistable state. In the second visible bistable state, the ferrofluidic coloring fluid forms a desired image in a desired color or colors.

Claims32

Dependent claims

A bistable electric paper, comprising:

a base substrate layer;
a transparent cover layer;
and
an intermediate layer defining an array of print cells, each print cell including a first completely hidden reservoir adjacent the base substrate layer, a second visible reservoir adjacent the transparent cover layer and visible through the transparent cover layer, a passageway defined between the first completely hidden reservoir and the second visible reservoir shaped to prevent viewing of the completely hidden reservoir when looking through the transparent cover layer, and a ferrofluidic coloring fluid contained in one of the first completely hidden reservoir and the second visible reservoir,
wherein a size of the passageway and at least one of a surface tension and a viscosity of the ferrofluidic coloring fluid are selected such that the ferrofluidic coloring fluid does not flow through the passageway absent an external magnetic driving force, but upon application of an external magnetic driving force near one of the base substrate layer and the cover layer, the ferrofluidic coloring fluid from each desired print cell is pulled by the external magnetic force from a farther one of the first hidden reservoir and the second visible reservoir through the passageway and into a nearer one of the first hidden reservoir and the second visible reservoir to form a desired viewable image in the electric paper.

2 more elements

A method of writing using a bistable electric paper having a base substrate layer, a transparent cover layer, and an intermediate layer defining an array of print cells, each print cell including a first completely hidden reservoir adjacent the base substrate layer, a second visible reservoir adjacent the transparent cover layer and visible through the transparent cover layer, a passageway defined between the first completely hidden reservoir and the second visible reservoir, and a ferrofluidic coloring fluid contained in one of the first completely hidden reservoir and the second visible reservoir, wherein a size of the passageway and at least one of a surface tension and a viscosity of the ferrofluidic coloring fluid are selected such that the ferrofluidic coloring fluid does not flow through the passageway absent an external magnetic driving force, but upon application of an external magnetic driving force near one of the base substrate layer and the cover layer, the ferrofluidic coloring fluid from each desired print cell is pulled by the external magnetic driving force from a farther one of the first completely hidden reservoir and the second visible reservoir through the passageway and into a nearer one of the first completely hidden reservoir and the second visible reservoir, comprising the steps of:

passing a magnetic writing instrument over at least one of the base substrate layer and the transparent cover layer;
and
selectively applying an external magnetic driving force to the electric paper during the step of passing to cause the ferrofluidic fluid in predetermined ones of the print cells to be pulled by the external magnetic driving force from a farther one of the first completely hidden reservoir and the second visible reservoir through the passageway and into a nearer one of the first completely hidden reservoir and the second visible reservoir to form a visible image through the transparent cover layer,
wherein the visible image remains even upon removal of the magnetic force.

1 more element

A method for fabricating an electric paper, comprising the steps of:

providing a base substrate layer;
providing a transparent cover layer;
die cutting and laminating intermediate layers to adjacent layers, including the base substrate layer and the transparent cover layer, to define an array of print cells, each print cell including a first hidden reservoir adjacent the base substrate layer, a second visible reservoir adjacent the transparent cover layer, and a passageway defined between the hidden reservoir and the visible reservoir;
filling one of the hidden reservoir and the visible reservoir for each print cell with a ferrofluidic coloring fluid having a predetermined surface tension and viscosity;
and
sealing the print cells,
wherein a size of the passageway is selected based on at least one of the surface tension and the viscosity of the ferrofluidic coloring fluid such that the ferrofluidic coloring fluid does not flow through the passageway absent an external magnetic driving force, but upon application of an external magnetic driving force near one of the base substrate layer and the cover layer, the ferrofluidic coloring fluid from each desired print cell is pulled by the external magnetic force from a farther one of the first hidden reservoir and the second visible reservoir through the passageway and into a nearer one of the first hidden reservoir and the second visible reservoir to form a desired viewable image in the electric paper.

4 more elements

Dependencies are inferred from the claim text.