Browse Prior Art Database

THERMOELECTRIC INK JET PRINTHEAD

IP.com Disclosure Number: IPCOM000026112D
Original Publication Date: 1990-Jun-30
Included in the Prior Art Database: 2004-Apr-05
Document File: 4 page(s) / 179K

Publishing Venue

Xerox Disclosure Journal

Abstract

It has been known for many years that reversible thermoelectric effects can be detected in a circuit consisting of junctions of two dissimilar materials having their junctions at different temperatures. The Peltier effect relates to the fact that heat must be exchanged by the junctions with the surroundings if the .unctions are maintained at different temperatures in the presence of a current flowing through the circuit. The amount of heat exchanged with surroundings changes with the change in the direction of the current. Because of this behavior, the junctions can be designed to add or to remove heat from the surrounding.

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XEROX DISCLOSURE JOURNAL

THERMOELECTRIC INK JET Proposed Classification PRINTHEAD US. C1.346/140R Satchidanand Mishra
Narayan V. Deshpande

Int. C1. Gold 15/18

12

16

300'K TC 300'K

TC

FIG. I

A

I

-

-

I

12

12

FlG. 2

XEROX DISCLOSURE JOURNAL - Vol. 15, No. 3 May/June 1990 133

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THERMOELECTRIC INK JET PRINTHEAD(C0nt'd)

Desig nation Material

It has been known for many years that reversible thermoelectric effects can be detected in a circuit consisting of junctions of two dissimilar materials having their junctions at different temperatures. The Peltier effect relates to the fact that heat must be exchanged by the junctions with the surroundings if the
.unctions are maintained at different temperatures in the presence of a current flowing through the circuit. The amount of heat exchanged with surroundings changes with the change in the direction of the current. Because of this behavior, the junctions can be designed to add or to remove heat from the surrounding.

For water based inks generally used in thermal ink jet printheads, it has been established that a temperature of 280°C at the heater surface is required to nucleate a bubble. A Peltier effect printhead may be designed to satisfy this temperature requirement. For this requirement to be met, the hot and cold

, unctions of the Peltier device must reach the following temperatures:

Temp. Range "K

Th = 273 + 280 = 553°K or higher (Cold (Hot Tc = 273 + 27 = 300°K junction) junction)

No single material can effectively cover the entire temperature range for the printhead. However, two or more same type materials can be used in series. Since the hot junction is to be separated from the source and sink connections, both p and n-type semiconductor materials may be utilized. A schematic arrangement of a thermal ink jet heater 10, using four materials, is shown in Figure 1, where tl, t2, t3, and t4 are thicknesses of each material. The heater electrodes 12 and common return 16 may be aluminum and the heater surface 14, which contacts the ink, may be tantalum or nickel. Four typical materials and the temperature range over which the eficiency of the thermoelectric device is high are listed in Table 1 below. The efficiency is characterized by a well known factor called "figure of merit", which is temperature dependent.

I p2

I n2 I PbTe (cast) I 580-440 I

134 XEROX DISCLOSURE JOURNAL - Vol. 15, No. 3 May/June 1990

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THERMOELECTRIC INK JET PRINTHEAD(C0nt'd)

A typical layout of an array of heaters is shown in Figure 2. The desired pixel density puts geometrical constraints on the heater size. At 300 spots/inch resolution, each heater 10 is placed at 85pm intervals. Allowing a minimum of 10pm spacing between heaters, the heater width can change from 55pm to 75pm. The heater surface length can be selected to any desired...