EP0171420B1

EP0171420B1 - Electrical circuits and components

Info

Publication number: EP0171420B1
Application number: EP85900937A
Authority: EP
Inventors: William P. Harper; Michael S. Lunt
Original assignee: Rogers Corp
Current assignee: Rogers Corp
Priority date: 1984-02-06
Filing date: 1985-02-04
Publication date: 1990-12-12
Also published as: DE3580877D1; IT8567111A0; JPH0766855B2; CA1227522A; EP0171420A1; IT1182413B; WO1985003596A1; JPS61501177A; EP0171420A4

Abstract

It is discovered that a liquid dispersion of polymer powder particles, predominantly of polyvinylidene fluoride, simultaneously: (a) can suspend electrical property additives, such as crystalline, hard, dense particles of generally spherical shape, uniformly in desired concentrations; (b) while containing a useful concentration of any of a wide range of such particles, can be deposited by high shear transfer to a substrate in accurately controllable thickness and contour; (c) when so deposited can be fused into a continuous uniform film which has low absorptivity, e.g., of moisture, and acts as a barrier film; (d) where desired, can, as one layer, be fused with other such layers, containing other electrical property additives, to form a monolithic electrical component; and, (e) in general, can meet all requirements for the making of any useful electrical circuit components, including electroluminescent lamps, by printing and coating techniques with a high degree of accuracy and controllability.

Description

The invention relates to

an electroluminescent lamp according to the first parts of Claims 1 and 2, resp.,
a method of forming electrical circuit component means according to the first part of Claim 11,
an electrical conductor according to the first part of Claim 20,
an electrical semiconductor according to the first part of Claim 21,
an electrical resistor according to the first part of Claim 22 and
a capacitive dielectric according to the first part of Claim 23, resp.

Electroluminescent lamps typically are formed of a phosphor-particle-containing layer disposed between corresponding electrodes adapted to apply an excitation potential to the phosphor particles, at least one of the electrode layers being semi-transparent to light emitted by the phosphors.
The phosphor-containing layer is provided with a barrier against moisture penetration to prevent premature deterioration of the phosphors, and permanent adherence between adjacent layers is sought to avoid delamination, e.g. under constant flexing or changes in temperature, particularly where the layers are of materials having different physical properties as this can also lead to premature failure in prior art electroluminescent lamps.
In the past, it has been recognized that deposit of fluids, as by printing with polymeric inks having electrical properties, would have a number of advantages to the manufacture of electrical components, including speed and accuracy of manufacture, low cost, small product dimensions, etc. Limitations of known inks and coating fluids as well as limitations in their manner of use, however, have limited the applicability of the techniques and the realizable electrical performance characteristics. In particular, high shear stress mass transfer techniques, such as screen printing and doctor blade coating, have not found wide use for products other than simple conductors.
There have been numerous and apparently conflicting requirements for such techniques that have stood in the way. Because nonuniformity of particle distribution can result in non-uniform electrical performance, thers is a need for any such fluid composition to hold the electrically active particles in uniform suspension and inhibit their settling prior to use and during the deposition and drying process. The very high density of some electrically active additives as compared to typical pigments, and their general spherical shape increases this demand.
It is important for any practical fluid composition to have a high percentage of polymeric binder, generally of the order of 50% by weight, in order to achieve a substantial dried coating thickness in each application. Thickness is usually needed to achieve the desired electrical properties as well as mechanical strength and abrasion resistance.
There is further a need for such composition to be highly thixotropic, i.e., have high "false body", so that while it is able to suspend the high density additive particles, it yet can have temporary lower viscosity under shear (i.e., be capable of "shear thinning"), to enable clean, accurate transfer of the fluid composition to the substrate. Such accuracy of formation is important because uniformity of thickness determines uniformity of electrical properties.
There are further requirements that such composition permits use of volatiles that have relatively low evaporation rates at ambient temperatures in order to achieve constant viscosity during an extended coating or printing run during which the ink is exposed to the atmosphere. Changes in viscosity and concentration can alter the characteristics of the deposit.
There are still further requirements that any composition and its method of application be compatible with substrates to which it is applied and to material that may be subsequently applied to it so that no damage is done to the various components of the circuit during manufacture or use.
In the case of circuit components with additives susceptible to deterioration in the presence of moisture, such as phosphor particles for an electroluminescent lamp, there are further stringent requirements related to the protection of those particles.
These and other requirements would present themselves as obstacles to anyone who would seek to broaden the use of fluid transfer techniques for the formation of electrical components and circuits and to lamps.
According to the invention it has been discovered that a liquid dispersion of powder particles comprised of polyvinylidene fluoride (PVDF) simultaneously:

a) can suspend uniformly in desired concentrations any of a wide variety of electrical property additives, including crystalline, hard, dense particles that are generally spherical in shape,
b) while containing a useful concentration of such particles, can be deposited by high shear transfer to a substrate in accurately controllable thickness and contour,
c) when so deposited can be fused into a continuous, uniform barrier film, the film itself having low absorptivity, e.g., of moisture,
d) where desired, can, as one layer, be fused with other such layers, containing other electrical property additives, to form a monolithic electrical component and
e) in general, can meet all requirements for the making of many useful electrical circuit components, including electroluminescent lamps, especially those with additives harmed, e.g., by the presence of moisture, by printing and coating with a high degree of accuracy and controllability.

The discovery can be employed to form products that are highly resistant to ambient heat and moisture and other conditions of use. Despite markedly different electrical properties between layers, the PVDF binding polymer is found to be capable of a controllable degree of interlayer penetration during fusing, which on the one hand is sufficient to provide monolithic properties, enabling, e.g. repeated bending without delamination, while on the other hand is sufficiently limited to avoid adverse mixing effects between different electrical additives in adjacent layers. PVDF can be employed as the binder with additive particles having widely different physical properties in adjacent layers, while the overall multilayer deposit exhibits the same coefficient of expansion, the same reaction to moisture, and a common processing temperature throughout. Thus, each layer can be made under optimum conditions without harm to other layers and the entire system will respond uniformly to conditions of use.
Remarkable results have been obtained by the simple techniques of silk screen printing and doctor blade coating of successive layers. Of special important, it has been discovered that circuit components that contain light-emitting phosphors and covering layers can be made which have unusual moisture resistance, light emissivity and durability. The moisture sensitivity of phosphors makes this a particularly important discovery.
While in certain cases homologs with substantially similar properties may be employed, it is found that a polymer powder consisting essentially of the homopolymer of PVDF produces electrical components and layers of outstanding properties and, being also commercially available, this polymer is presently preferred.
The invention consists spec. of an electroluminescent lamp (EL) having one or more superposed thin layers of a suspension of polymer solid dispersed in a liquid phase, the predominant constituent of the polymer in the lamp being polyvinylidene fluoride (PVDF) in substantially non-cross-linked state.
To fuse the layers, substantially without cross-linking occurring, results in the realization of important properties not found in a cross-linked system, e.g., as taught by US-A-4417 174 (Kamijo et aI.) according to the first part of present Claim 1, teaching an electroluminescent cell having, as a binder, a cross-linked "fluorine rubber", formed by copolymerization of vinylidene fluoride with propylene hexafluoride, in the presence of a vulcanizing agent (col. 2, 1.30-34); by definition, vulcanization is "a chemical reaction of sulfur (or other vulcanization agent) with rubber or plastic to cause cross-linking of the polymer chains; it increases strength and resiliency of the polymer" (McGraw-Hill Dictionary of Scientific and Technical Terms, 3d Ed. (1984)).
The difference between the invention and Kamijo et al. is thus not merely one of substitution of materials, i.e., of a portion of PVDF for propylene hexafluoride (which is, in any case, nowhere taught or suggested by the prior art), but is an important difference of structure, i.e., between a substantially noncross-linked homopolymer and a cross-linked rubber.
Incidentally, US―A―3 850 631 (Tamai), teaches the use of PVDF homopolymer in forming an electrophotographic imaging (!) member. There is, however, no suggestion in either state of the art document of substituting PVDF homopolymer for the copolymerized rubber of US-A-4 417 174 (Kamijo et al.).
The method of the invention consists of forming components, e.g., of an electroluminescent lamp, by depositing on a substrate and drying, without cross-linking,
a succession of superposed thin layers of a suspension of polymer solid dispersed in a liquid phase, the predominant constituent of the polymer being polyvinylidene fluoride (PVDF).
The method further includes heating in a manner to fuse the polymer continuously throughout the extent of the layer, and between layers, without cross-linking, to form a monolithic unit.
The method claims concern forming components in a manner to fuse the polymer continuously within the layer, and to fuse the layers, without cross-linking occurring.
A plurality of ways of carrying out the invention is described in detail below with reference to drawings, namely:

Figure 1 a perspective view in section of an electroluminescent lamp formed according to the invention;
Figure 2 a side section view of the lamp taken at the line 2-2 of Figure 1;
Figure 3 is side section view of a portion of side the lamp indicated in of Figure 1, enlarged as viewed through a microscope.

We first describe, in Examples A through D, examples of selected electrical circuit components formed as thin layers and then describe, in Example E, a complete electrical circuit, in this case an electroluminescent lamp, formed of a superposed series of the layers as described in Examples A through D.

Examples

Example A-Dielectric insulating layer

To prepare the dielectric composition, 10 g of a PVDF dispersion of 45% by weight, polyvinylidene fluoride (PVDF) in a liquid phase believed to be primarily carbitol acetate (diethyl glycol monoethyl ether) were measured out. This dispersion was obtained commercially from Pennwalt Corporation under the tradename "Kynar Type 202". As the electrical property-imparting additive, 18.2 g of barium titanate particles (BT206 supplied by Fuji Titanium, having a particle size of less than about 5 pm) were mixed into the PVDF dispersion. An additional amount of carbitol acetate (4.65 g) was added to the composition to maintain the level of solids and the viscosity of the composition at a proper level to maintain uniform dispersion of the additive particles while preserving the desired transfer performance. It was observed after mixing that the composition was thick and creamy and that the additive particles remained generally uniformly suspended in the dispersion without significant settling during the time required to prepare the example. This is due, at least in part, to the number of solid PVDF particles (typically less than about 5 pm in diameter) present in the composition.
A substrate was selected for its resistance to the carrier fluid employed and for its ability to withstand the extreme temperatures of treatment, e.g., up to 260°C (500°F), as described below, in this case, a flexible PVDF film. The composition was poured onto a 320 mesh polyester screen positioned 0.37 cm (0.145 inch) above the substrate. Due to its high apparent viscosity, the composition remained on the screen without leaking through until the sequeegee was passed over the screen exerting shear stress on the fluid composition causing it to shear-thin due to its thixotropic character and pass through the screen to be printed, forming a thin layer on the substrate below. The deposited layer was subjected to drying for 2-1/ 2min at 79°C (175°F) to drive off a portion of the liquid phase, and was then subjected to heating to 260°C (500°F) (above the initial melting point of the PVDF) and was maintained at that temperature for 45 s. This heating drove off remaining liquid phase and also fused the PVDF into a continuous smooth film on the substrate.
The resulting thickness of the dried polymeric layer was 8.9x10-4 cm (0.35 mil (3.5x10^-4 inch)).
A second layer of the composition as described was screen-printed over the first layer on the substrate. The substrate now coated with both layers was again subjected to heating as above. This second heating step caused the separately applied PVDF layers to fuse together. The final product was a monolithic dielectric unit having a thickness of 1.8x10-³ cm (0.7 mil) with no apparent interface between the layers of polymer, nor with the substrate, as determined by examination of a cross-section under microscope. The particles of the additive were found to be uniformly distributed throughout the deposit.
The monolithic unit was determined to have a dielectric constant of about 30.

Example B-Light emitting phosphor layer

To prepare the composition, 18.2 g of a phosphor additive, zinc sulfide crystals (type #723 from GTE Sylvania, smoothly rounded crystals having particle size of about 15 to 35 pm) were introduced to 10 g of the PVDF dispersion used in Example A. It was again observed after mixing that despite the smooth shape and relatively high density of the phosphor crystals, the additive particles remained uniformly suspended in the dispersion during the remainder of the process without significant settling.
The composition was screen printed onto a substrate, in this case a rigid sheet of polyepoxide, standard printed circuit board material, though a 280 mesh polyester screen positioned 0.37 cm (0.145 inch) above the substrate to form a thin layer. The deposited layer was subjected to the two stage drying and fusing procedure described in Example A to fuse the PVDF into a continuous smooth film on the substrate with the phosphor crystals uniformly distributed throughout.
The resulting thickness of the dried polymeric layer was 3.Ox10-3 cm (1.2 mils (1.2x10-³ inch)).
The deposited film was tested UV and found to be uniformly photoluminescent, without significant light or dark spots.

Example C-Semi-transparent conductive front lamp electrode

To prepare this conductive composition, 13.64 g of indium oxide particles (from Indium Corporation of America, of 325 mesh particle size) were added to 10 g of the PVDF dispersion used in Example A. An additional amount of carbitol acetate (4.72 g) was added to lower the viscosity slightly to enhance the transfer properties. It was again observed after mixing that the additive particles remained uniformly suspended in the dispersion during the remainder of the process without significant settling.
The composition was screen printed onto a substrate, in this case, a polyamide film, e.g., Kapton supplied by E.I. duPont, through a 280 mesh polyester screen positioned 1.3 cm (0.5 inch) above the substrate to form a thin layer. The deposited layer was subjected to the two stage drying and fusing procedure described in Example A to fuse the PVDF into a continuous smooth film on the substrate with the particles of indium oxide uniformly distributed throughout.
The resulting thickness of the dried polymeric layer was 1.3x10-³ cm (0.5 mil (0.5x10-³ inch)).
The deposited film was tested and found to have conductivity of 10 ohm-cm, and to be light transmissive to a substantial degree due to the light transmissivity of the semi-conductor indium oxide particles and of the matrix material.

Example D-Conductive buss

To prepare this conductive composition, 15.76 g of silver flake (from Metz Metallurgical Corporation, of 325 mesh #6 particle size) were added to 10 g of the PVDF dispersion used in the examples above. The particles remained uniformly suspended in the dispersion during the remainder of the process without significant settling.
The composition was screen printed onto a suitable substrate through a 320 mesh polyester screen positioned 0.38 cm (0.15 inch) above the substrate to form a thin layer. The deposited layer was subjected to the two stage drying and fusing procedure described in Example A to fuse the PVDF into a continuous smooth film on the substrate with the silver flake uniformly distributed throughout.
The resulting thickness of the dried polymeric layer was 2.5x10-³ cm (1.0 mil (1.Ox10-³ inch)).
The deposited film was tested and found to have conductivity of 10-³ ohm-cm.
In the following example we manufactured a complete electroluminescent lamp 10, comprised of a deposit of superposed thin polymeric layers as described above having different characteristic electrical properties, as described with reference to the drawings.

Example E

Referring to Figure 1, the substrate 12 used in this lamp configuration was flexible aluminum foil (10.7x10-³ cm (4.2 mils)) cut in pieces of size suitable for handling, e.g. 5.1 cm (2 inches) by 7.6^-cm (3 inches). The foil was cleaned with xylene solvent.
A coating composition for forming dielectric layer 14 upon the substrate 12, in this case to act as an insulator between the substrate/electrode 12 and the overlying light-emitting phosphor layer 16 (described below), was prepared as described in Example A and coated in two layers upon the substrate.
A coating composition for forming the light emitting phosphor layer 16 was prepared as described in Example B. The composition was superposed by screen printing over the underlying insulator layer 14 and the substrate with its coatings 14 and 16 was subjected to the heating conditions described.
Subjecting the layers to temperatures above the melting temperature of the PVDF material caused the PVDF to fuse throughout the newly applied layer and between the layers to form a monolithic unit upon the substrate, as shown enlarged as under a microscope in Figure 3. However, the interpenetration of the material of the adjacent layers having different electrical properties was limited by the process conditions to less than about 5% of the thickness of the thicker of the adjacent layers, i.e., to less than about 1.5x 10-⁴ cm (0.06 mil) so that the different electrical property-imparting additive particles remained stratified within the monolithic unit as well as remaining uniformly distributed throughout their respective layers.
The coating composition for forming the semi-transparent top electrode 18 was prepared as described in Example C. The composition was superposed by screen printing upon the light-emitting phosphor layer 16. The substrate with the multiple layers coated thereupon was again heated to above the PVDF melting temperature to cause the semi-transparent upper electrode layer to fuse throughout and to fuse with the underlying light-emitting layer to form a monolithic unit. The indium oxide, though typically characterized as a semiconductor, serves as a conductor here, and its transparency enhances the light transmissitivity of the deposited layer.
The coating composition for forming the conductive buss 20 was prepared as described in Example D and was screen printed upon semi-transparent upper electrode 18 as a thin narrow bar extending along one edge of the electrode layer, for the purpose of distributing current via relatively short paths to the upper electrode.
This construction with connecting wires 34, 36 (Figure 1) and a power source 38, forms a functional electroluminescent lamp 10. Electricity is applied to the lamp via the wires and is distributed by the buss layer 20 to the front electrode 18 to excite the phosphor crystals in the underlying layer 16, which causes them to emit tight.
Due, however, to the damaging effect of, e.g., moisture on phosphor layer 16, it is desirable to add a protective and insulative layer 22 about the exposed surfaces of the layers of the lamp to seal to the peripheral surface of the substrate 12. This layer 22 is also formed according to the invention, as follows.
The PVDF dispersion employed in Example A, devoid of electrical-property additives, is screen printed over the exposed surfaces of the lamp 10 through a 180 mesh polyester screen. The lamp was dried for 2 min at 79°C (175°F) and heated for 45 s at 260°C (500°F). The coating and heating procedure was performed twice to provide a total dried film thickness of protective-insulative layer 22 of 2.5x10-³ (1.0 mils). (By using PVDF as the binder material in this and all the underlying layers, each layer has the same processing requirements and restrictions. Thus the upper layers, and the protective coating, may be fully treated without damage to underlying layers, as might be the case if other different binder systems were employed).
The final heating step results in an electroluminescent lamp 10 of cross-section as shown magnified in Figure 3. The polymeric material that was superposed in layers upon flexible substrate 12 has fused within the layers and between the layers to form a monolithic unit about 8.6x10-³ cm (3.4 mils) thick that flexes with the substrate. As all the layers are formed of the same polymeric material, all the layers of the monolithic unit have common thermal expansion characteristics, hence temperature changes during testing did not cause delamination. Also, due to the continuously film-like nature of each layer due to the fusing of its constituent particles of PVDF and the interpenetration of the polymeric material in adjacent layers, including the protective layer 22 covering the top and exposed side surfaces, the lamp was highly resistant to moisture during high humidity testing, and the phosphor crystals did not appear to deteriorate prematurely, as would occur if moisture had penetrated to the crystals in the phosphor layer.
In the following examples, the physical properties of compositions useful according to the invention, prior to the addition of additives, were evaluated.

Viscosity

To determine the approximate range of viscosity prior to addition of additives over which the compositions of the invention are useful, two compositions were prepared using isophorone as the liquid phase and polyvinylidene fluoride (PVDF) powder (461 powder, supplied by Pennwalt), which is substantially insoluble in isophorone, i.e., it is estimated that substantially less than about 5% solvation occurs. The physical properties of the new compositions were adjusted by addition of PVDF powder or isophorone until the first composition (Composition A) had thickness or body at close to the lower end of the range useful for screen printing, and the second composition (Composition B) had body at close to the high end of the useful range.
The weight proportions of the compositions and the resultant viscosities are as shown in Table A.
The viscosity of the compositions was measured using a Brookfield Viscosity Meter, Model LVF, at the #6 (low shear) setting. Composition A was tested using a #3 spindle at a multiplication factor of 200x and gave an average reading of 88.5. Composition B was tested using a #4 spindle at a multiplication factor of 2000x and gave an average reading that appeared well in excess of the maximum reading of 100.
The viscosity of the commercially available Kynar 202 PVDF dispersion (Composition X) was tested on the same equipment and registered a viscosity of approximately 40 Pa s (40,000 cps). (It is noted that while the weight percentage of PVDF solids is lower in the commercial product than in either of the test compositions, a different solvent is employed in the commercial system, so strict interpolation is not possible).
To demonstrate the shear thinning characteristic of the composition, a standard coating composition, in this case a dielectric composition prepared as in Example 1, was subjected to further testing. The viscosity of the coating composition was tested in a Brookfield Viscosity Meter, Model LVF, as described above, with a #4 spindle operated at four selected, different speed settings, the speed of the spindle of course being directly proportional to the shear between the spindle and the composition. As shown in Table B, the viscosity of the composition decreased dramatically with increased shear.

Solids range

The weight % solids of PVDF will vary depending upon the nature of the carrier fluids employed, and upon the physical properties of the additive, e.g., upon particle surface area (particle shape, spherical or otherwise, as well as particle size) and particle density. The range of PVDF solids present in the overall coating composition can range between about 50%, by weight, down to about 15% by weight. The preferred range is between about 25 and 45%, by weight.

Obher embodiments

Numerous other embodiments are within the following claims, as will be obvious to one skilled in the art.
The protective layer 22 of the electroluminescent lamp may be applied as preformed film of polyvinylidene fluoride under pressure of 875 KPa (125 pounds per square inch), and the lamp heated at 177°C (350°F) for 1 min and then cooled while still under pressure. Each separate layer applied may have a dry thickness of as much as 0.02 cm (.010 inch), although thickness in the range between about 7.6x10^-3 cm (.003 inch) to 0.25x 10-³ cm (.0001 inch) is typically preferred. The protective layer may be applied as preformed film of one or more other materials compatible with the lamp structure, which alone or in combination provide adequate protection against penetration of substances detrimental to performance of the underlying lamp.
As mentioned, the composition may be applied by screen printing, or by various of the doctor blade coating techniques, e.g. knife over roll or knife over table. The shear-imparting conditions of screen printing may also be varied, e.g. the squeegee may be advanced along the screen at rates between about 5 (2) and 500 cm (200 inches) per min, and the size of the screen orifices may range between about 3.6x10-³ (1.4) and 17.8x10^-3 cm (7 mils) on a side.
Materials which consist essentially of homopolymers of PVDF are preferred. However, other materials may be blended with PVDF, e.g. for improving surface printability, for improving processability during manufacturing, or for improving surface bonding. An example of one material miscible in a blend with PVDF is polymethyl methacrylate (PMMA), e.g., employed at 1 to 15% by weight of PVDF, preferably 5 to 10% by weight. Also, other materials may be employed in place of PVDF.
The guiding criteria for selection are low moisture absorptivity, ability of particles to fuse at elevated temperature to form a continuous moisture barrier film, and, when applied to flexible substrate, flexibility and strength. The general physical and mechanical properties of PVDF (in homopolymer form) appear in Table C.
The liquid phase of the composition may be selected from the group of materials categorized in the literature as "latent solvents" for PVDF, i.e, those with enough affinity for PVDF to solvate the polymer at elevated temperature, but in which at room temperature PVDF is not substantially soluble, i.e., less than about 5%. These include: methyl isobutyl ketone (MIBK), butyl acetate, cyclohexanone, diacetone alcohol, diisobutyl ketone, butyrolactone, tetraethyl urea, isophorone, triethyl phosphate, carbitol acetate, propylene carbonate, and dimethyl phthalate.
Where additional solvation is desired, a limited amount of "active" solvent which can, in greater concentrations, dissolve PVDF at room temperature, e.g., acetone, tetrahydrofuran (THF), methyl ethyl ketone (MEK), dimethyl formamide (DMF), dimethyl acetamide (DMAC), tetramethyl urea and trimethyl phosphate, may be added to the carrier. Such limited amounts are believed to act principally in the manner of a surfactant serving to link between the PVDF polymer particles and the predominant liquid phase, thus to stabilize the PVDF powder dispersion.
As will also be obvious to a person skilled in the art, the viscosity and weight % of PVDF solids in the coating composition may also be adjusted, e.g. to provide the desired viscosity, suspendability and transfer characteristic to allow the composition to be useful with additive particles of widely different physical and electrical characteristics.
The additives mentioned above are employed merely by way of example, and it will be obvious to a person skilled in the art that other additives alone or in combination, or other proportions of the additives mentioned may be employed according to the invention. For example, for forming resistors, semiconductors and conductors, suitable additives may be selected on the basis of bulk resistivity or bulk density, or on the basis of other criteria such as cost. The bulk resistivities and bulk densities of examples of materials useful as additives are shown in Table D.
Of course many other suitable materials are available, e.g., alloys of the listed metals or others may in some cases be employed in forming a conductor; salts rendered stably semiconductive by the addition of donor or acceptor dopands may in some case be employed in forming a semiconductor; and glass (fiber, shot or beads) or clay may in some cases be employed for electrical resistance.
Similarly, additives useful as insulators or as capacitors may be selected on the basis of dielectric constant of the material as used in the composition, or, again, on the basis of density or other factors. For example, materials resulting in a composition having a dielectric constant above 15 are useful for forming capacitive dielectrics. Use of additives according to the invention provides a composite layer with electrical characteristics significantly different in degree from that of PVDF above. Examples of materials with sufficiently high dielectric constant are shown in Table E for comparison with PVDF.
Additive particles suitable for use in formation of an electroluminescent lamp include zinc sulfide crystals with deliberately induced impurities ("dopants"), e.g., of copper or magnesium. Representative materials are sold by GTE, Chemical and Metallurgical Division, Towanda, Pennsylvania, under the trade designations type 723 green, type 727 green, and type 813 blue-green.

Claims

1. An electroluminescent lamp comprising a phosphor-particle-containing layer comprising a layer of polymer, disposed between corresponding electrodes adapted to apply an excitation potential to said phosphor particles, the upper electrode being light transmissive to radiation from said particles, characterized by said thin layer of polymer having polyvinylidene fluoride (PVDF) in substantially non- cross-linked state as the predominant constituent, containing a uniform dispersion of phosphor, being the product of the steps of depositing a fluid dispersion of particles of said polymer and phosphor upon a substrate followed by drying, and having said polymer in a fused, substantially non-cross-linked state continuously throughout the extent of said layer.

2. An electroluminescent lamp comprising a phosphor-particle-containing layer disposed between corresponding electrodes adapted to apply an excitation potential to said phosphor particles, the upper electrode being light transmissive to radiation from said particles, characterized by said upper electrode comprising a thin layer of polymer having polyvinylidene fluoride (PVDF) in substantially non-cross-linked state as the predominant constituent, containing a uniform dispersion of additional particles that are substantially more electrically conductive than said polymer, being the product of the steps of depositing a fluid dispersion of particles of said polymer and said additional particles upon a phosphor-containing layer followed by drying, and having said polymer in a fused, substantially non-cross-linked state continuously thoughout the extent of said layer.

3. An electroluminescent lamp of Claims 1 and 2, characterized by said polymer of said layers being fused together forming a monolithic unit.

4. Lamp of any preceding claim, characterized in that said polymer consists essentially of the homopolymer of polyvinylidene fluoride.

5. Lamp of any of Claims 2-4, characterized in that said electrically conductive particles are transparent, semi-conductive particles.

6. Lamp of any of Claims 3-5, characterized by a further light-transmitting outer layer devoid of any of the additional particles, and lying over and being fused with the layer therebelow, forming part of said monolithic unit.

7. Lamp of any of Claims 1-5, characterized in that said layers are deposits by high-shear transfer.

8. Lamp of Claim 7, characterized in that said deposits are of predetermined, printed form.

9. Lamp of any of Claims 1,3―5, characterized in that said substrate and said layer thereon comprise a flexible unit.

10. Lamp of any preceding claim, characterized in that each of said layers has a thickness in the range of 0.008-0.0003 cm.

11. A method of forming electrical circuit component means, specifically successive components of an electroluminescent lamp, characterized by depositing on a substrate, and drying, without cross-linking, a succession of superposed thin layers of a suspension of polymer solid dispersed in a liquid phase and having polyvinylidene fluoride (PVDF) as the predominant constituent, said liquid suspension for at least one of said layers containing a uniform dispersion of particles selected from the group consisting of substances having dielectric, resistive and conductive values substantially different from the respective values of said polymer, heating in a manner to fuse said polymer continuously throughout the extent of said layer and between said layers, without cross-linking, to form a monolithic unit.

12. Method of Claim 11, characterized in that each layer, preceding the application of the next, is heated sufficiently to fuse said polymer particles to form a continuous film-like layer.

13. Method of Claim 11 or 12, characterized in that said liquid phase contains a predominant constituent substantially without solubility for said polymer under the conditions of its deposit.

14. Method of any of Claims 11-13, characterized in that said liquid phase is predominantly formed from one or more members selected from the group consisting of methyl isobutyl ketone (MIBK), butyl acetate, cyclohexanone, diacetone alcohol, diisobutyl ketone, butyrolactone, tetraethyl urea, isophorone, triethyl phosphate, carbitol acetate, propylene carbonate, dimethyl phthalate.

15. Method of Claim 13 or 14, characterized in that said liquid phase contains a minor amount of active solvent selected to promote the suspension of said polymer particles in said liquid phase without substantially dissolving said polymer.

16. Method of Claim 15, characterized by a minor amount of one or more members selected from the group consisting of acetone, tetrahydrofuran (THF), methyl ethyl ketone (MEK), dimethyl formamide (DMF), dimethyl acetamide (DMAC), tetramethyl urea, trimethyl phosphate.

17. Method of any of Claims 11-16, characterized in that said liquid dispersion exhibits a substantial reduction in viscosity under high-shear stress, and said layer is deposited by high-shear transfer.

18. Method of Claim 16, characterized in that said layer is deposited by silk screen printing.

19. Method of Claim 16, characterized in that said layer is deposited by blade coating.

20. Electrical conductor formed by a method of any of Claims 11-19, characterized by a volume resistivity in the range of 10^-2―10^-5 Ohm-cm.

21. Electrical semiconductor formed by a method of any of Claims 11-19, characterized by a volume resistivity in the range of 10^-1―10³ Ohm-cm.

22. Electrical resistor formed by a method of any of Claims 11-19, characterized by a volume resistivity in the range of 1-10⁶ Ohm-cm.

23. Capacitive dielectric formed by a method of any of Claims 11-19, characterized by a dielectric constant above 15.