KR20070018943A - Improved thick film dielectric structure for thick dielectric electroluminescent display - Google Patents

Abstract

Providing an improved smoothing layer applied over the thick film dielectric layer forming the composite, wherein the improved smoothing layer substantially reduces surface defect density in the base thick film dielectric layer, and improvements are achieved by mixing the surfactant in the smoothing layer, The addition of a surfactant to the deposition solution forming the smoothing layer facilitates the wetting of the lower thick film dielectric layer, thereby reducing the holes / holes (herein referred to as 'defects') present in the thick film dielectric layer, resulting in improved dielectric structure and An electroluminescent display having such a structure can be achieved.

Thick Film Dielectric Layer, Smooth Layer, Surface Defect Density, Surfactant, Holes, Electroluminescent Display

Description

IMPROVED THICK FILM DIELECTRIC STRUCTURE FOR THICK DIELECTRIC ELECTROLUMINESCENT DISPLAY}

The present invention relates generally to thick film dielectric layer electroluminescent displays. More specifically, the present invention relates to improved novel dielectric structures, methods for their manufacture, and electroluminescent displays having such structures.

Thick film dielectric layer electroluminescent displays are typically fabricated on ceramics, glass ceramics, glass or other heat resistant substrates, as well as excellent resistance to dielectric breakdown compared to thin film electroluminescent (TFEL) displays fabricated on glass substrates. Provides a reduced operating voltage. The method of manufacturing a display first involves the deposition of a set of row electrodes on a substrate. A thick film dielectric layer is then deposited followed by a thin film structure to sandwich one or more phosphor thin films and a set of optically transparent column electrodes between the one or more thin film dielectric layers. The entire structure is then covered with a sealing layer to protect the thick and thin film structures from degradation due to moisture or other air pollution.

Composite thick film dielectric layers used in such displays have a high dielectric constant while allowing the use of relatively thick dielectric layers in the display without a significant increase in display operating voltage. Since the dielectric yield strength of these materials is relatively low, relatively thick dielectric layers of typically about 10 micrometers or more are used to prevent dielectric breakdown during display operation. Typically, thick film dielectric layers comprise sintered perovskite piezoelectric or ferroelectric materials such as lead magnesium titanate-zirconate (PMN-PT) or lead magnesium niobate having thousands of dielectric constants. Thinner layers of harmonious piezoelectric or ferroelectric materials such as lead zirconate tartanate (PZT) applied using metal organic deposition (MOD) or solgel techniques to smooth the thick film surface for deposition of thin film phosphor structures There may be.

Applicant's U.S. Patent No. 5,432,015, which is hereby incorporated by reference in its entirety, discloses a thin film dielectric layer composite structure for use in electroluminescent displays. The thick film layer is sintered at a high temperature on a suitable substrate to which thin film gold electrodes are applied, particularly high enough that the pores remaining at the top of the layer can be filled by an overlapping layer deposited using sol-gel or MOD technology. Sintered thick film density is achieved. However, the overlap layer does not completely fill the pores of the sintered material. This is because the volume is significantly reduced when the sol-gel or MOD precursors are fired to form piezoelectric or ferroelectric materials.

Applicant's PCT patent application WO 00/70917, which is incorporated herein by reference in its entirety, discloses an isostatic pressing process where the deposited thick film dielectric layer material is mechanically compressed using an isostatic pressing process before sintering and have. This serves to increase the density of the thick film material and also to reduce the pores, so that when the overlapping layer is coated, the dielectric constant and dielectric strength of the layer can be increased. The dielectric breakdown is associated with irregular defects in the dielectric layer and the probability of yield increases with increasing display area. Thus, layers with higher nominal dielectric strengths are desired to be used for large displays to eliminate this tendency.

Applicant's International Patent Application PCT CA02 / 01932, which is hereby incorporated by reference in its entirety, discloses modified thick film paste formulations used to make thick film dielectric layers. This modified thick film dielectric layer may be sintered at temperatures as low as 650 ° C. to facilitate the use of glass substrates. However, this modified thick film dielectric layer still has pores.

It is therefore desirable to provide an improved dielectric structure that exhibits a few defects (ie, holes or holes) that essentially act as sites for dielectric breakdown and undesired reactions between thick film dielectric layers and phosphor layers that reduce display life. Provide conduits for

Summary of the Invention

The present invention is an improved smoothing layer applied on a thick film dielectric layer forming a composite. The improved smoothing layer substantially reduces the surface defect density in the base thick film dielectric layer. Improvement is achieved by mixing the surfactant in the smooth layer. Adding surfactants to the deposition solution forming the smooth layer facilitates wetting the lower thick film dielectric layer, thereby reducing the holes / holes (herein referred to as 'defects') present in the thick film dielectric layer.

The present invention also achieves improved dielectric structures and electroluminescent displays having such structures.

According to one aspect of the present invention, in a smooth layer for use as a thick film dielectric layer, the smooth layer is prepared by adding a surfactant to a metal organic solution or sol gel substantially applied to the thick film dielectric layer. In various aspects this applied smooth layer is sintered (baked) at a suitable temperature to form a piezoelectric or ferroelectric material. In another aspect the piezoelectric or ferroelectric material is lead zirconate titanate (PZT).

According to another aspect of the invention, the smoothing layer is lead zirconate titanate (PZT) comprising a surfactant.

According to another aspect of the present invention, in a sintered synthetic thick film dielectric structure for an electroluminescent display,

The thick film dielectric layer has a PZT smoothing layer, and the smoothing layer is provided with a high dielectric constant material having a high dielectric constant material having a region density of pit defects of about 100 defects or less per square millimeter. In other aspects, a PZT smoothing layer is applied to the metal organic solution or sol gel comprising lead acetate, titanium alkoxide, zirconium alkoxide and solvent, which is substantially applied onto the post film dielectric layer and then sintered at temperatures up to about 850 ° C. It is made by adding a surfactant.

According to another aspect of the present invention, in a sintered synthetic thick film dielectric structure for an electroluminescent display,

A lower thick film dielectric layer and an upper smooth layer,

The smoothing layer reduces defects in the lower thick film dielectric layer, and the smoothing layer is substantially applied to the thick film dielectric layer and is manufactured by adding a surfactant to the sintered metal organic solution or sol gel. Is provided.

According to another aspect of the invention, in a sintered synthetic thick film dielectric structure for an electroluminescent display, the following components:

(a) an underlayer of a thick film dielectric layer composition comprising at least one of lead magnesium niobate (PMN), lead magnesium niobate titanate (PMN-PT), lead titanate and lead oxide; Glass frit compositions comprising lead oxide, boron oxide, boron oxide and silicon dioxide;

(b) a top smooth layer comprising at least one layer of lead zirconate titanate (PZT), wherein the at least one layer immediately adjacent to (a) has no more than about 100 defects per square millimeter A sintered synthetic thick film dielectric structure is provided for an electroluminescent display characterized by having a region density of.

According to another aspect of the present invention, in the method for producing a composite thick film dielectric structure for an electroluminescent display,

Superimposing the thick dielectric layer with a smooth organic layer coated as a metal organic solution or sol gel comprising a surfactant;

A method of manufacturing a sintered synthetic thick film dielectric structure for an electroluminescent display is provided, comprising sintering at a temperature of up to about 850 ° C.

In other aspects of the invention, additional smoothing layers that do not include a surfactant may be superimposed on the synthetic thick film dielectric structure and sintered. In other aspects the superposition of the smoothing layer may be performed by metal organic deposition (MOD) or solgel techniques.

According to another aspect of the present invention, in an electroluminescent display,

Board;

A synthetic thick film dielectric structure provided on the substrate; And

Phosphor Compositions Provided on the Synthetic Thick Film Dielectric Structure

There is provided an electroluminescent display comprising a. In various aspects, the composite thick film dielectric structure is provided with an electroluminescent display comprising a smooth layer having an area density of pit defects of less than about 100 defects per square millimeter.

Other features and advantages of the invention will be apparent from the following detailed description. However, it will be understood by those skilled in the art that the detailed description and specific examples showing the embodiments of the present invention are merely illustrative, and various modifications and changes can be made without departing from the spirit and scope of the present invention.

[Brief Description of Drawings]

1 is a schematic plan view of an electroluminescent test pixel;

2 is a cross-sectional view of a thick film electroluminescent device showing the positions of the thick film dielectric layer and the smoothing layer of the present invention;

3 is a micrograph of the surface of a smoothing layer on a thick film dielectric layer formed using the method of the present invention;

4 is a micrograph of the surface of a smoothing layer on a thick film dielectric layer formed using a conventional method;

5 shows the area density of surface defects in a thick film dielectric layer made by the method of the present invention and by a conventional method;

FIG. 6 is a top view of the panel with a diagonal of 43 centimeters representing the sample area of FIG.

Detailed description of the invention

EXAMPLE

The present invention is an improved dielectric structure for use in electroluminescent displays. The improved dielectric structure includes a bottom thick film dielectric layer overlaid with a novel smooth layer. This new smooth layer has smaller pit defects than previously attempted smooth layers.

The thick film dielectric layer is typically baked after screen printing to be suitable for phosphor deposition and then superimposed into a smooth layer. However, the smooth layer previously manufactured and used on most of the thick film surface does not adequately fill abnormally many holes or holes in the thick film dielectric layer, leaving a certain number of holes in the thick film dielectric layer. The area density of these holes can be reduced to fewer abnormally large holes by improving the thick film dielectric layer, but this is difficult and time consuming, and requires expensive polishing of the particles in the thick film paste used to make the thick film layer. The high homogeneity of the thick film pastes prepared from these and / or the sintering of the thick film dielectric layers requires isostatic pressing of the thick film layers at extreme high pressures requiring very large and expensive equipment.

The present invention overcomes these problems by incorporating a suitable surfactant in the metal organic solution forming the smoothing layer used to overlap the thick film dielectric layer. This is an inexpensive improved method for achieving the result of reducing the area density of holes or holes. The surfactant substantially improves the penetration and interaction of the smoothing layer superimposed as a MOD solution or solgel on the thick film dielectric layer to effectively remove the majority of the holes / holes. The surfactant not only modifies the surface tension between the coated film and the substrate it is coated on, but also sinters at high temperatures (ie, without damaging the high dielectric constant of the smooth layer or reducing the high dielectric strength that the smooth layer imposes on the entire thick film dielectric layer). And high temperature chemistry that occurs when firing.

It is known that surfactants can also be used in cured polymer layers (US Pat. Nos. 5,306,756, 5,874,516, 5,891,825, 6,406,803 and 6,613,455). Surfactants are also used with certain low dielectric constant ceramics (US Patent Application No. 2003/0219906) and in thick film pastes to facilitate their deposition in high resolution patterns to define electrical circuits. (US Patent Application No. 2003/02111406), but they have not been used in smooth layers for high dielectric thick film compositions as well as use to correct defects in smooth layers used in conjunction with high dielectric thick film compositions. Also did not try.

The improved smooth layer of the present invention can be coated by providing a sol solution on the thick film dielectric layer using a MOD process that greatly reduces the defect density on the surface of the final synthetic thick film dielectric layer. Alternatively, the sol solution may be coated using sol gel techniques known to the skilled person. The solgel or MOD layer can be matched with a piezoelectric smoothing layer, such as lead zirconate titanate (PZT) smoothing layer as described in Applicant's WO 00/70917 and PCT CA02 / 01932, which is hereby incorporated by reference in its entirety. Or a high dielectric constant material that is a ferroelectric material. Briefly, if a PZT smoothing layer is desired, the MOD solution includes lead acetate, titanium alkoxides and zirconium alkoxides in suitable solvents. Surfactants are also added to this mixture. The action of the MOD solution used to deposit the smooth layer is significantly different for glass substrates than for the previously disclosed alumina substrates. This difference is due to the different thick film firing temperatures, some of which are used for different substrate materials. The optimum MOD solution viscosity is different for different substrate materials.

The smoothing layer formed from the MOD solution layer may comprise a material other than PZT. A requirement for smooth layer materials is that they must be chemically and physically compatible with the thick film dielectric layer so that the layers combined have the required smoothness, dielectric strength and dielectric constant. Other suitable smoothing layer materials may be selected from, for example, lead lanthanum zirconate titanate, preferably titanate, k-strontium titanate, barium tantalate and tantalum oxide.

Surfactants for use in the smooth layer may be blended at high temperatures to form a smooth layer without substantially damaging the high dielectric constant of the smooth layer itself or reducing the high dielectric strength imparted to the entire thick film composite thick film. Any surfactant may be selected. Surfactants are non-phosphorus in many aspects and should be easily miscible with MOD solvent, which is ethylene glycol. The surfactant should be completely decomposed to leave no solid residues in the smooth layer when calcined at about 500 ° C. Suitable nonionic surfactants for use in the present invention include: Sufinol ™ 61, Dimethyl Lexinol, Sufinol ™ 420, ethoxylated acetylenic diols, Triton ™ X-100, p-3 octylenoxy polyethyl Alcohols and mixtures thereof and the like, but are not limited to these. Cationic surfactants are also suitable for use and reduce defect density to some extent but are not as preferred as nonionic surfactants. Suitable cationic properties include, but are not limited to, empos ™ PS-200, alkyl ether phosphates, cetyltrimethylammonium bromide and mixtures thereof, and the like. In aspects of the invention Sufinol ™ 61 is used. The amount of surfactant for use in the MOD solution for the smooth layer is in the range of 0.1-5% by weight, preferably in the range of 1.0-2.0% by weight. It will be understood by those skilled in the art that the range of surfactant may be an auxiliary range between 0.1-5% by weight.

The composition of the thick film paste used to form the thick film dielectric layer comprises lead magnesium niobate (PMN), lead magnesium niobate-titanate (PMN-PT), Lead titanate, and one or more perovskite forming precursor powders selected from barium titanate and any lead oxide. It also includes glass frit compositions comprising lead oxide, boron oxide and silicon oxide and has a melting temperature of less than about 550 ° C., and also uses solvents, polymer binders to hold the deposited film together before sintering and selected deposition methods. And a vehicle comprising any viscosity and surface tension modifier to allow film deposition and thickness non-uniformity of the required thickness. Deposition methods can be, but are not limited to, screen printing, stenciling and roll coating. The optimum viscosity for the deposition depends on the deposition method chosen.

In accordance with non-limiting embodiments of the invention, the perovskite forming precursor powder may be included in the thick film dielectric composition in different proportions. Most of its phase is preferably PMN or PMT-PT and is present between about 85% and 95% by weight of the total thick film dielectric layer composition. The remaining perovskite forming precursor powder may be present in the following weight percentages: up to about 10% of barium titanate, up to about 8% lead oxide, and up to about 15% lead titanate. The glycol composition comprises lead oxide, boron oxide (B 2 O 5), and silicide oxide (SiO 2) at approximately the following weight percent, i.e., about 87-94 wt% of lead oxide, about 6-9 wt% of boron oxide, and about silitone dioxide It may also be present as a predetermined homogenized or mixed powder up to 6% by weight. Lead oxide, boron oxide, and silicon dioxide powder form a solid solution of about 550 ° C. or more. The total weight of the glass frit composition may be about 1-8% by weight of PMN or PMT-PTd.

The particle size of the perovskite forming precursor powder and the glass fleet composition is such that the particle size of about 20-30% of the barium titanate powder should be about 50-100 nanometers and in many aspects is properly dispersed in the sintered thick film dielectric layer. It may be less than about 1 micron on average, or greater than about 0.2 micron, except that it must be up to about 50 nanometers to ensure.

The transporter is formulated to provide adequate deposition properties and does not significantly affect the properties of the sintered thick film dielectric layer if the components burn or volatilize off when they are heated before the deposited films are sintered. However, the properties of the transporter are important in achieving deposition of defect-free layers at the milling time of the paste to reduce the size of the particles in the paste. The viscosity of the paste as well as the solid-liquid ratio of the paste are important parameters in determining the optimum paste for defect printing or deposition. The optimum viscosity and solid-liquid fraction are different for deposition on glass material substrates than for deposition on ceramic substrates because of their micro-roughness differences.

According to an embodiment of the present invention, a surfactant is deposited by first depositing and then sintering a PMN or PMN-PT based paste so that the improved dielectric structure of the present invention forms a thick film, followed by a metal organic deposition (MOD) process. It is prepared by coating a smooth PZT layer comprising a. The composition of this structure near the junction with the substrate is mainly derived from the first deposited PMN or PMN-PT layer and the composition near its top surface is mainly PZT. In the area between them these two materials react to mix to form a synthetic structure. The dielectric yield strength of the dielectric layer is related to the detailed chemical and physical structure of the layer. Genetic yields typically start with defects or abnormalities in the membrane. Since the probability of genetic yielding depends on the number of defects present, it is part of the display. It may also be influenced by the nature of the dielectric layer, the distribution of stresses within the layer and the environment, in particular the level of moisture to which the display containing the dielectric layer is subjected. An aspect of the present invention is to reduce the density of defects in the dielectric layer by the use of a smoothing layer mixed with a surfactant.

In formulating the thick film dielectric layer components of the dielectric layer, there are a number of considerations to be removed. Because the sintering temperature is low, the holes in the sintered layer increase because there is more to complete the sintering process. The present invention is directed to a dielectric structure with or without minimum defects such as holes, holes, cracks and voids having an acceptable low pyrochlore content to achieve appropriate dielectric breakdown strengths and high dielectric constants, respectively. It is possible to achieve. This is achieved by appropriate selection of the chemical composition and physical properties of the thick film paste used to form the chemical composition and physical properties of the thick film portion of the synthetic dielectric layer and the surfactant MOD solution for the smooth layer.

The mechanical integrity of an electroluminescent device constructed using the present invention depends on the physical properties of the substrate, in particular the coefficient of thermal expansion of the substrate. The coefficient of thermal expansion should be in the range of about 4 × 10 ⁻⁶ and 10 × 10 ⁻⁶ / ° C. and in some aspects in the range of about 5.5 × 10 ⁻⁶ and 10 × 10 ⁻⁶ / ° C. If the coefficient of thermal expansion of the substrate material is too low than that of the composite thick film dielectric layer, it may crack.

The dielectric structure is incorporated in an electroluminescent display and provided on a substrate in such a display, specifically a glass or glass / ceramic or ceramic substrate, which may include lead magnesium niobate, lead titanate, and / or barium titanate Is provided. The invention is particularly applicable to dielectric structures comprising lead magnesium niobate coated and heat treated using a MOD solution with a surfactant to form a smooth coating layer comprising lead zirconium titanate.

In representative silicon of the present invention, the dielectric structure for an electroluminescent display is formed by printing, compressing and sintering a paste containing a high dielectric constant dielectric powder thereon into at least one smooth layer of high dielectric constant material formed by a deposition process thereon. After superposition, a thick film dielectric layer formed by firing a metal organic solution (MOD) as exemplified in PCT patent application WO00 / 70917, which is hereby incorporated by reference in its entirety. Here, the MOD solution is a thick film when the organometallic precursor compound necessary to form the smoothing layer dissolved in a suitable solvent and the MOD solution and the superimposed MOD layer are heated and calcined to form a composite layer having a smoothing layer substantially free of pores A surfactant is included to reduce the interfacial surface tension between the MOD solution and the sintered thick film dielectric layer to facilitate substantially interpenetration of the dielectric layer composition.

According to another silicon of the present invention, a dielectric structure for an electroluminescent display is constructed on a rigid substrate having a smooth layer having an area density of pit defects on the upper surface of about 100 defects or less per square millimeter. Pit defects are defined as holes or depressions whose surface is greater than 0.5 micrometers in depth.

According to another embodiment of the present invention, a dielectric structure for an electroluminescent display comprises at least one of a high dielectric constant material formed by printing, compressing and sintering a paste containing a high dielectric constant dielectric powder thereon by a deposition process thereon. And a magnesium lead niobate thick film dielectric layer formed by firing a metal organic solution (MOD) after superimposing with a smooth layer. Here, the MOD solution facilitates substantially interpenetration of the thick film dielectric layer material when the organometallic precursor compound and MOD solution and its superimposed MOD layer are heated and calcined to form a smooth layer comprising lead zirconate-titanate. Surfactant to reduce the interfacial surface tension between the MOD solution and the sintered thick film dielectric layer.

According to another embodiment of the present invention, a dielectric structure for an electroluminescent display is formed of lead zirconate-titanate formed by a deposition process upon printing, compacting and sintering a paste containing a high dielectric constant dielectric powder. And a magnesium lead niobate thick film dielectric layer formed by firing a metal organic solution (MOD) after overlapping with at least one smooth layer. Here, the MOD solution includes an organometallic precursor compound necessary to form a smooth layer and a surfactant for lowering the interfacial surface tension between the MOD solution and the sintered thick film dielectric layer.

According to another embodiment, the electroluminescent dielectric structure for the display is a high dielectric constant paste for printing, compressing and sintering containing dielectric powder, and then, the above formula formed by the deposition process _{PbZr x Ti 1 - x O 3} ( Here, after superposition with a smooth layer of lead zirconate-titanate having 0.5 ≦ x ≦ 0.55), lead acetate trihydrate, methoxyethanol, zirconium propoxide, titanium propoxide, ethylene glycol and surfinol 61 And a magnesium lead niobate thick film dielectric layer formed by firing a MOD solution comprising a surfactant comprising ™.

One or more smoothing layers may be superimposed on a thick film dielectric layer deposited on the substrate. In some aspects the smoothing layer immediately adjacent to the thick film dielectric layer comprises a surfactant. Subsequent smoothing layers do not require a surfactant. The total thickness of the smooth layer applied to the thick film dielectric layer composition is up to about 1500 nm (within a range as understood by the skilled person) after sintering. Smooth layers are applied to achieve the desired surface smoothness, defined as surface mitigation, when there are no individual pit defects of less than 0.5 micrometers along the surface of the composite dielectric layer combined in the order of display pixel size. Can be. The number and thickness of layers needed to achieve the required smoothness depend on the thickness, porosity and surface roughness of the lower thick film layer, as will be understood by the skilled person. The improved smooth layer and improved dielectric structure of the present invention are for use in electroluminescent displays, such as those exemplified in Applicant's US Pat. No. 5,432,015, which is incorporated herein by reference in its entirety.

The foregoing description has generally described the present invention. Reference is made to the specific embodiments as follows for a more complete understanding. These examples are illustrative only and are not intended to limit the scope of the invention. It will be understood that equivalent modifications and substitutions are possible in light of the circumstances. Although specific terminology is used herein, such terminology is for the purpose of description and not of limitation.

Example

Example  One

Referring to the schematic diagrams of Figs. 1 and 2, a PP8C glass substrate in which a gold low electrode set 2 and a thick film dielectric layer 3 for an electroluminescent display of 43 cm diagonal are available from Nippon Electric Glass Co., Osaka, Japan ( It is composed in 1) phase. The deposition method of the row electrode set and the thick film dielectric layer is similar to those disclosed in US Patent Application Serial No. 09 / 326,777 in combination with the methods disclosed herein. The gold electrode layer is deposited on the substrate prior to the deposition of the thick film dielectric layer. The thick film dielectric layer is formed sequentially in two deposition processes, each layer printing the thick film paste, then drying the printed layer, densifying the printed layer using isostatic pressing, and finally sintering the densified layer. It consists of doing. The densification process is performed using cold isostatic pressing as taught in US patent application Ser. No. 09 / 540,288, which is incorporated herein by reference in its entirety. Sintering is carried out in air in a belt furnace at a maximum temperature of 700 ° C. The total transfer time through the belt furnace was 75 minutes. Thick film pastes include 600 g of PMN, 18 g of lead oxide, 20 g of lead titanate and 20 g of barium titanate from Ferrosa, Niagara Falls, New York, USA, all having a typical particle diameter of about 1 micrometer and having a diameter of about 50 nanometers. Paste-formed powdered precursor materials were added with the addition of 6 g of barium titanate, available from Albuquerque, NM, USA, having a particle size. Precursor materials were obtained from 293 g of a solution of alpha terpinol, 5 g of acetone, 4 g of Empos ™ PS-220 from Witco Inc. of Houston, Texas and Ferro Electric Materials of Hyde Park Boulevard 4511, Niagara Falls, NY, USA 15 g of CF 7589 glass flits were mixed in a slurry consisting of 4 g of mixed di-n-butyl phthalate added for about 2 hours until the fleet particle size was reduced to about 1 micrometer. Upon addition of the precursor materials, the final slurry was further mixed for an additional 2 hours and then passed through a 10 micron filter to filter the large particles. Mixing was performed using a zirconia 3 mm ball mill to minimize contamination. The viscosity was adjusted to a viscosity between 30 and 5000 centipoise by addition of a carrier consisting of 1-3% ethyl cellulose in alpha-terpineol to the filtered slurry. The average size (D50) of the particles measured by the microtrack particle size analyzer in the mixed slurry was 0.63 micrometers.

Subsequent to the deposition of the thick film layer, a smooth layer 4 as shown in FIG. 2 was deposited using a MOD solution prepared as follows. 850 g of methoxyethanol was added to 562 g of lead acetate trihydrate, and the mixture was stirred on a hot plate to dissolve lead acetate. The solution was distilled off to remove 200 milliliters of liquid and cooled to 90 ° C. 322 g zirconium propoxide was then added to aid dissolution and 167 g titanium propoxide was added. The final solution was distilled off to remove 540 milliliters of liquid from the solution. Subsequently 256 g of anhydride ethylene glycol and 23 g of Sufinol ™ 61 surfactant were added to the solution via channel. The solution was then cooled to ambient temperature and then filtered. The viscosity of the solution was measured using a drop ball viscometer and found to be 25 cetipoise. The light absorption of the solution was in the range of 0.05-0.2% at 400 nanometers using Ultrospec 1000 UV / visible spectrophotometer. Moisture content was determined to be 0.5-1.2% using Karl Fischer analysis. The MOD solution was stored in argon until spun onto the thick film dielectric layer described previously using a spin rate of 350 rpm. The coated substrate was then calcined in a belt furnace under air at a maximum temperature of 700 ° C. for 75 minutes. After firing a second MOD solution was prepared using a MOD solution similar to that used for the first layer but without the addition of surfactant. The viscosity of this solution was adjusted to 9 cps and then spin coated onto the first MOD layer to form the finished dielectric structure. The combined thickness of the two MOD inducing layers was about 1500 nanometers.

The surface of the finished composition dielectric layer was tested under a microscope. Photomicrographs of the surface are shown in FIG. Only defects in the form of small amounts of pits or depressions in the surface were observed by micrographs. The area density of the pit defect was about 50 defects per square millimeter. Analysis of a very small portion of the same area of the surface using a scanning electron microscope reveals that only about 10% of these defects are pits penetrating through the MOD-induced smooth layer into the lower thick film layer, with the remaining 90% being 0.5 micrometers. Recesses in a smooth layer having the following normal depth.

Example  2

A dielectric structure was constructed on the substrate as described in Example 1. However, instead of the MOD solution for the first MOD layer described in Example 1, a MOD solution having a viscosity of 15-40 centipoise was added without adding a surfactant.

The surface of the finished composition dielectric layer was examined under a microscope. The photomicrograph of the surface is shown in FIG. The area density of the pit defects was about 3500 defects per square centimeter. The surface of the MOD layer was found in the micrographs with a large amount of defects (pits and depressions) as compared to the surface shown in FIG. 3, and the MOD solution described in Example 1 significantly reduced the number of surface defects. The usability of the surfactant containing these was shown. FIG. 5 shows the prior art without the use of a surfactant in the MOD solution used to use the smoothing layer, compared to the number of defects for several cross sections of the same thick film dielectric layer in the same region produced by the method of the present invention. The histogram of the number of defects for various 0.15 square millimeter cross sections of the thick film dielectric layer produced by the method is shown. The cross sections were selected from the harmonious region of the thick film deposited on the 43 centimeter diagonal substrates of Examples 1 and 2. The approximate location of the regions selected for the panels prepared with and without the addition of surfactant to the MOD solution is shown in FIG. The positions numbered in FIG. 6 correspond to the positions indexed on the horizontal side of FIG. As can be seen from the data, the defect density was reduced by about 5 factors when using the method of the present invention.

It has also been found that the variability in defect density at different locations on the substrate has been substantially reduced and the surface quality is uniform compared to what can be achieved by the prior art methods.

While the preferred embodiments of the present invention have been described in detail so far, those skilled in the art will appreciate that many modifications and variations are possible without departing from the scope of the appended claims and the spirit of the invention.

Claims (41)

In the smooth layer for use as a thick film dielectric layer, And said smooth layer comprises a high dielectric constant material having a region density of pit defects of less than about 100 defects per square millimeter. The method of claim 1, And said high dielectric constant material is a piezoelectric or ferroelectric material. The method of claim 2, The piezoelectric or ferroelectric material is lead zirconate titanate (PZT). Sintered dielectric structure for an electroluminescent display. The method according to any one of claims 1 to 3, And said smooth layer is prepared by adding a surfactant to a sol gel or metal organic solution of an organometallic precursor compound substantially sintered on said thick film dielectric layer. The method of claim 4, wherein The surfactant is added to the metal organic solution, sintered dielectric structure for an electroluminescent display. The method of claim 5, And said surfactant is provided as about 0.1 to about 5 weight percent of said metal organic solution. The method of claim 6, And said surfactant is provided as about 1.0 to about 2 weight percent of said metal organic solution. The method of claim 2, And said piezoelectric or ferroelectric material smoothing layer comprises at least one of lead lanthanum zirconate titanate, barium titanate, barium strontium titanate, barium tantalate and tantalum oxide. The method according to any one of claims 4 to 7, And said surfactant is selected from the group consisting of nonionic surfactants and cationic surfactants. The method of claim 9, The nonionic surfactants include Surfynol ™ 61, dimethyl hexynol, Surfinol ™ 420, ethoxylated acetylenic diols, Triton ™ X-100, and p-tertiary octaphenoxy polyethyl. Sintered dielectric structure for an electroluminescent display, characterized in that it is selected from the group consisting of alcohols and mixtures thereof. The method of claim 10, And said nonionic surfactant is Surfinol ™ 61. Sintered dielectric structure for electroluminescent display. The method of claim 9, The cationic surfactant is selected from the group consisting of Emphos ™ PS-200, alkyl ether phosphate, cetyltrimethyl ammonium bromide and mixtures thereof. The method of claim 4, wherein And said smooth layer is sintered at temperatures up to about 850 [deg.] C. The method of claim 1, And said smoothing layer is provided on said thick film dielectric layer as two or more layers having a total thickness of up to about 1500 nm. Sintered Synthetic Thick Film Dielectric Structure for Electroluminescent Display, Thick film dielectric layer and A smooth layer on the thick film dielectric layer, And said smooth layer comprises a high dielectric constant material having a region density of pit defects of less than about 100 defects per square millimeter. The method of claim 15, The high dielectric constant material is a sintered composite thick film dielectric structure for electroluminescent display, characterized in that the piezoelectric or ferroelectric material. The method of claim 16, Sintered composite thick film dielectric structure for an electroluminescent display, wherein the piezoelectric or ferroelectric material is lead zirconate titanate (PZT). The method according to any one of claims 15 to 17, The smooth layer is sintered synthetic thick film dielectric structure for an electroluminescent display, characterized in that it is selected from the group consisting of lead lanthanum zirconate titanate, barium titanate, barium strontium titanate, barium tantalate and tantalum oxide. . The method of claim 15, And the smoothing layer is prepared by adding a surfactant to a sol gel or metal organic solution of an organometallic precursor compound substantially sintered on the thick film dielectric layer. The method of claim 19, The surfactant is provided as about 0.1- about 5% by weight of the metal organic solution. Sintered synthetic thick film dielectric structure for an electroluminescent display. The method of claim 20, And said surfactant is provided as about 1.0 to about 2 weight percent of said metal organic solution. The method according to any one of claims 19 to 21, The surfactant is selected from the group consisting of nonionic surfactants and cationic surfactants. Sintered synthetic thick film dielectric structure for an electroluminescent display. The method of claim 22, The nonionic surfactant consists of Surfinol ™ 61, dimethyl hexynol, Sufinol ™ 420, ethoxylated acetylenic diols, Triton ™ X-100, p-tertiary octyphenoxy polyethyl alcohol and mixtures thereof. Sintered composite thick film dielectric structure for an electroluminescent display, characterized in that it is selected from the group consisting of: The method of claim 22, Wherein said nonionic surfactant is SUFINOL ™ 61. Sintered synthetic thick film dielectric structure for an electroluminescent display. The method of claim 22, Wherein said cationic surfactant is selected from the group consisting of empos ™ PS-200, alkyl ether phosphates, cetyltrimethylammonium bromide and mixtures thereof. The method according to any one of claims 15 to 25, And said smoothing layer is provided on said thick film dielectric layer as two or more layers having a total thickness of up to about 1500 nm. The method of claim 26, And said smooth layer not immediately adjacent said thick film dielectric layer is prepared in a sol-gel or metal organic solution of an organometallic precursor compound to which no surfactant is added, sintered synthetic thick film dielectric structure for an electroluminescent display. The method according to any one of claims 15 to 27, The thick film dielectric layer comprises the following components: (a) one or more of lead magnesium niobate (PMN), lead magnesium niobate titanate (PMN-PT), lead titanate and lead oxide; (b) glass frit compositions comprising lead oxide, boron oxide, boron oxide and silicon oxide; (c) solvent; And (d) polymer binder Sintered composite thick film dielectric structure for an electroluminescent display, characterized in that formed from a sintered composite from a paste comprising a. The method of claim 28, The sintering temperature is up to about 850 ℃ sintered composite thick film dielectric structure for an electroluminescent display. Sintered Synthetic Thick Film Dielectric Structure for Electroluminescent Display, (a) one or more of lead magnesium niobate (PMN), lead magnesium niobate titanate (PMN-PT), lead titanate, barium titanate and lead oxide; And a glass frit composition comprising lead oxide, boron oxide, boron oxide, and silicon oxide; an underlayer of a thick film dielectric layer composition comprising; And (b) a top smooth layer comprising at least one lead zirconate titanate (PZT) layer, And said at least one layer immediately adjacent said (a) has an area density of pit defects of less than about 100 defects per square millimeter. The method of claim 30, The smooth layer is formed by adding a surfactant to the sol gel or metal organic solution of the organometallic precursor compound sintered synthetic thick film dielectric structure for an electroluminescent display. The method of claim 31, wherein The surfactant is selected from the group consisting of nonionic surfactants and cationic surfactants. Sintered synthetic thick film dielectric structure for an electroluminescent display. 33. The method of claim 32, The nonionic surfactant consists of Surfinol ™ 61, dimethyl hexynol, Sufinol ™ 420, ethoxylated acetylenic diols, Triton ™ X-100, p-tertiary octyphenoxy polyethyl alcohol and mixtures thereof. Sintered composite thick film dielectric structure for an electroluminescent display, characterized in that it is selected from the group consisting of: The method of claim 33, wherein Wherein said nonionic surfactant is SUFINOL ™ 61. Sintered synthetic thick film dielectric structure for an electroluminescent display. 33. The method of claim 32, Wherein said cationic surfactant is selected from the group consisting of empos ™ PS-200, alkyl ether phosphates, cetyltrimethylammonium bromide and mixtures thereof. A method for producing a synthetic thick film dielectric structure for an electroluminescent display, Superimposing the thick film dielectric layer with a metal organic solution comprising a surfactant to form a smooth layer of high dielectric constant material; Sintering at a temperature of up to about 850 ℃ Synthetic thick film dielectric structure manufacturing method for an electroluminescent display comprising a. The method of claim 36, And said metal organic solution comprises lead acetate, titanium alkoxide and zirconium alkoxide in a suitable solvent. The method of claim 36 or 37, Wherein said high dielectric constant material is lead zirconate-titanate (PZT). The method according to any one of claims 36, 37 or 38, Wherein said smooth layer has an area density of pit defects of less than about 100 defects per square millimeter. In electroluminescent displays, A substrate; 36. An electroluminescent display comprising on said substrate a synthetic thick film dielectric structure as claimed in any of claims 15-35. The method of claim 40, Wherein said composite thick film dielectric structure comprises a smooth layer having an area density of pit defects of about 100 defects or less per square millimeter.

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