US 4,977,416 A · Integrated thick film electrostatic writing head

Abstract

An improved electrographic writing head employs interleaved arrays of writing nibs and small geometry, high impedance, thick film resistors and semiconductor driver circuits fabricated on separate glass epoxy substrates disposed in adjacent back to back relation. The writing head achieves significant savings in manufacturing costs by using low cost printed circuit and thick film technology. Power consumption may be reduced by more than half over prior art devices due to the high impedance of each thick film pull up resistor coupled with an associated writing nib. A ground plane is disposed between the adjacent substrates and between adjacent arrays of writing nibs. The ground plane prevents electrical interaction between the substrates and prevents the formation of parasitic nib-to-nib capacitance by shunting parasitic capacitance currents to ground. The ground plane thus reduces the possibility of flaring and substantially eliminates inadvertent writing by adjacent nibs.

Claims10

Dependent claims

A thick film electrographic writing head for recording information on a recording medium comprising:

a first planar insulating substrate having an array of writing electrodes at an edge thereof, each electrode having a nib end for placing a charge corresponding to a dot of information on a dielectric recording medium which is passed in close proximity thereto;
a second planar substrate disposed in adjacent back-to-back relation with said first substrate and having a second array of writing electrodes disposed at an edge thereof adjacent said first of writing electrodes such that said first and second arrays of writing electrodes of said corresponding first and second substrates are offset one dot width apart in the plane of said substrates and are offset two dot widths in a direction perpendicular to the plane of said substrates;
a plurality of thick film resistor means formed on said first and second substrates, each resistor means coupled to a corresponding writing electrode for substantially reducing discharge current of stray capacitances;
a plurality of switch means for selectively charging a corresponding writing electrode when said switch is in a first state, each switch means coupled with a corresponding one of said thick film resistor means;
a plurality of high impedance, thick film pull-up resistors formed on said first and second substrates, each pull-up resistor coupled between a high voltage line and a corresponding one of said plurality of switch means for controlling the charging current applied to each writing nib;
shielding means disposed between said first and second substrates for connecting writing electrodes to ground.

3 more elements

Dependencies are inferred from the claim text.

Integrated thick film electrostatic writing head

Life of this patent

Integrated thick film electrostatic writing head

Life of this patent

Abstract

Claims10