US3514325A - Electrosensitive recording article and method of making the same - Google Patents

Description

May 26, 1970 D. R. DAVIS F-TAL 3, 1

ELECTROSENSITIVE RECORDING ARTICLE AND METHOD OF MAKING THE SAME Filed NOV. 1'7, 1966 INVENTORS DALE R. DAVIS ROBERT W. Kl NGSTON ATTO R NEY United States Patent US. Cl. 117-217 4 Claims ABSTRACT OF THE DISCLOSURE An improved electrosensitive recording medium and method of making the same provides a matrix of conductive particles in a cross-linked binder disposed on a conductive backing layer for improved resistance to surface abrasion by a surface-contacting writing electrode.

This invention relates to an improved electrosensitive recording medium which responds to low voltage and low power writing signals, and to the method of making the same.

It is an object of the present invention to provide an improved electrosensitive recording medium which provides contrasting marks or records in response to applied writing signals and which includes an electrosensitive surface coating that resists abrasion and mechanical scraping at elevated recording temperatures by the recording electrode of recording apparatus.

It is another object of the present invention to provide a method for making an improved electrosensitive recording medium.

In accordance with the method and means of the pres- 3,514,325 Patented May 26, 1970 The thickness of the layer 13 as measured by its resistance per square should be within this range so that low voltage writing signals applied through narrow electrodes in contact with the surface of the recording medium may attain a sufiiciently high current density to vaporize the aluminum in the contacted area, thereby exposing the backing material in the regions through which writing signal flowed. Lower resistances per square (i.e. thicker films) require considerably higher power to vaporize the aluminum layer in the contacted region and higher resistances per square (i.e. thinner films) require higher writing voltages (typically above 60 to 100 volts) to provide sufficient power to vaporize the aluminum layer Thus, since the limits are not precise, the term approximately as used herein is intended to cover values of resistance per square which are as much as an order of magnitude away from the expressed limits but which are useful with higher power, high voltage writing signals. Thus if sufiiciently transparent backing material 11 is used, a recording 15 on the present medium may serve as an optically-transmissive master in inexpensive reproduction or electrooptical reading of the recording medium.

The surface coating 17 is prepared according to one embodiment of the present invention as follows: 300 grams of conductive zinc oxide (New Jersey Zinc Co. grade 013 or 016) and 400 grams of tetrahydrofuran or methylethylketone are combined with 100 grams of an organic polymer such as Eponol 55B40 (Shell Chemical Co.) and 15 grams of polyisocyanate cross-linking agent such as Mondur CB-6O (Mobay Chemical Co.). Other useful combinations of binder materials and crosslinking agents (some being aided by a catalyst) are described in Shell Chemical Co., Plastics and Resins Division, Technical Bulletin SC:6451 and in the following ent invention, a thin layer of aluminum is deposited on table:

Wei ht Ratio Percent cross-linker Disper- C r of Zinc Oxide Cross-linker (by weight Percent s ion pot to Binder Binder Agent of Binder) Catalyst Cat. life Time Temp. F.)

41 Eponol 551340 1 Toltuene diisocyanmole percent...-. None 0 3 hrs 7 days 72 do. 15 mole percent d0 0 4 hrs do 72 Uformite 9 MX61 50 wt. percent -.do. 0 4 days. 24 hrs. 200 do 20 wt percent d0 0 5days 24hrs 200 do do I 50 wt. percent p-Tgi uene sulfonic 1 3 days 2 hr 200 30 4: 20 wt. percent 200 4: 50 wt. percent. 250 4; 54 do do 0 2 4:1. CYMEL 4 245-8 10, 30, 50, wt. percent. p-Ttilclllene sulfonic 1 2-3 days. 200

ac 4:1 -do 1 Mondur B 03450.... 30, 60 Wt. percen N e 0 1, 2 days. lgifiiays 1;?

rs. an Vitel B PE200 do a 10-50 wt. percent .-do--- 0 4 days. 3 wks 72 3:1; Butvar 76 7 Uformite MX61 20 wt. percent 0 6 days 24 hrs 200 1 Shell Chemical Co. 1 Robin and Haas Co. a Union Carbide. 4 American Cyanamid. 5 Mobay Chemical Co. Goodyear Rubber & Chemical Co. 1 Shawinigan Resins backing material to form a conductive layer having a selected resistance per square unit area. A surface coating including zinc oxide in a conductive matrix which is bonded together in a cross-linked polymer binder is provided on the conductive layer to form a recording medium which produces contrasting marks in response to applied writing signals.

These and other objects of the invention will be apparent from a reading of this specification and an inspection of the accompanying drawing which shows electrosensitive medium and recording apparatus according to the present invention.

In the drawing, there is shown an electrosensitive recording medium 9 which may be prepared according to one embodiment of the present invention as follows: Aluminum is vacuum deposited or sputtered onto a suitable backing material 11 such as paper or plastic film using well known methods to form a thin conductive layer 13 having a resistance ranging from approximately one ohm to approximately one hundred ohms per square.

The ingredients selected for the surface coating are then finely ground and dispersed in a ball mill operating for several hours. The agitated mixture forms a dispersion which is then deposited on the aluminum layer 13 by suitable means such as reverse roll coating to a dry weight of about three pounds per one thousand square feet. The volatile fluids are then driven oif in a drying oven leaving the conductive particles and binder in the surface coating 17 about .5 mil thick on the aluminum layer 13. The coated medium is then baked typically at about 200 F. for four hours to produce the cross-linking reaction. The binder in the resulting conductive matrix thus includes a three-dimensionally cross-linked polymer which provides a firm bond to the aluminum layer that does not exhibit viscous flow at elevated temperatures and hence that resists-mechanical scraping and abrasion at the elevated temperatures encountered during recording. This has the advantage over conventional uncrosslinked binders that the residue from the recorded regions is a mere powdery substance which does not accumulate around the recording electrode that contacts the surface of the recording medium. Heretofore, the conventional uncross-linked surface coatings of electrosensitive recording media have exhibited substantial viscous flow at the elevated temperatures encountered during recording. There, the surface-contacting recording electrode scrapes 01f the softened binder which thus accumulates around the electrode as gummy globules that build up and interfere with the electrode contact.

Therefore, the improved electrosensitive recording medium of the present invention is capable of producing a contrasting mark in region thereof through which electrical recording signal flows without producing substantial amounts of gummy rubble or objectionable residue that can build up around the surface-contacting recording electrode.

We claim:

1. An electrosensitive recording medium which prior to recording contrasting records therein in response to applied electric writing signals, comprises:

a metal conductive layer on an insulating substrate;

and

a conductive coating matrix on the surface said conductive layer which is capable of directly producing a contrasting record at elevated temperatures associated with electrographic recording thereon, the coating matrix including conductive particles in a binder which ,is the reaction product of an organic polymer that is capable of forming molecular cross links and a molecular cross-linking agent that is capable of interacting with said organic polymer to form molecular cross links and which includes crosslinked molecules, whereby the cross-linked binder prevents substantial viscous flow of the binder at elevated temperatures associated with electrographic recording thereon.

2. An electrosensitive recording medium as in claim 1 wherein said conductive particles include particles of zinc oxide which are dispersed throughout said matrix.

3. The method of producing an electrosensitive recording medium comprising the steps, performed prior to electrosensitive recording thereon, of:

forming a surface coating on a conductive hacking by depositing thereon a fluid dispersion comprising conductive particles, an organic binder that is capable References Cited UNITED STATES PATENTS 3,207,601 9/1965 Giaimo 96-15 3,411,948 11/1968 Reis 117-217 ALFRED L. LETVITT, Primary Examiner C. K. WEIFFENBACH, Assistant Examiner US. Cl. X.'R. 96--1.8; 117-218

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