FI121962B - A process for the preparation of a high luminescent phosphor - Google Patents

Description

method for the preparation of a high luminescent phosphor

Field of the Invention

The present invention relates to a process for the production of a phosphor layer.

5 Description of the Related Art

The PbX thin film is traditionally used effectively as a fluorescent agent in electro-absorbent batteries, solar cells, infrared detectors, etc. The method of forming a PbX thin film according to the prior art is illustrated and its problems are illustrated.

Up to now, reaction systems whereby PbS is grown on either a murine coordination compound with a Pb oxidation degree of +2 such as Pb (thd) 2 (thd = 212,6,6-tetramethyl) have been used to grow PbX by atomic layer or chemical gas phase cultivation. -3.5-heptanedione) and Pb (dedtc) 2 (dedtc-diethyl thiocarbamate), or a lead halide such as PbCS2 or PbBr2, by reaction with H2S or H2Se or by decomposition of sulfur (S) Pb (dedtc) 2 (see U.S. Patent No. 5,496,597, issued June 20, 1994).

However, coordination compounds, such as thd, have very heterogeneous and poorly reproducible properties in thin film growth. The disadvantage of halide compounds has been that the halide ions have been present in the thin film or on the surface and adversely affected the process and properties of the device. Thus, the device made from the halide compound has not been good in luminescence. In particular, when Pb (thd) 2 is used in the blue electroluminescent stain, there is? 25 oxygen in the thin film, which is one of the precursor elements and strongly attenuates the luminance ™.

Another conventional method for making a PbS thin film is to react the tetraethyl lead with a block copolymer matrix to form active sites and then lead H2S to active sites. In these 30 cases, nanosilver type PbS is generated. Reaction of the tetraethyl lead with H2S regener2 regenerates the active sites of the polymer used, so the repeated reaction g g increases the size of the PbS cluster. However, this method cannot be used to grow a continuous PbS thin film or a fluorescent thin film,

Another conventional method for obtaining a PbS thin film is to grow a monocrystalline metal oxide or sulfate on a monocrystalline substrate at very low temperature using an organometallic compound (U.S. Pat. No. 4,823,428, filed February 8, 1985). In this process, an alkyl, alkoxyl or halide compound is reacted with oxygen or sulfur in the radical state to increase the sulfide or oxide. Oxygen or 5 sulfur radicals are produced by a light source. However, the main object of this method is to grow the thin film at low temperature by using light as an energy source.

When a transition metal, a rare earth metal, or the like is added to a light-emitting central host material formed by a periodic-order compound of Group I1 and Group VI (hereinafter referred to as II-VI), the metal doped material can be used as a , blue and green visible light. First, the general characteristics of a phosphor and the technique known below for making such a phosphor and its problems will be described.

There are a few possible mechanisms by which fluorescent luminescence is induced. In the case of an electroluminescent device, electrons are first sprayed from the interface between the phosphor layer and the dielectric layer to the phosphor layer, while applying an electric field to the device. The electrons are then accelerated to strike against the light-emitting central ions in the fluorescent material. This shock excites the electrons of the light emitting central ions from the ground state to the upper level. When the electrons of the ions return from the excited state to the baseline state, luminescence is produced, the energy of which corresponds to the difference between the two energy levels. In the field emission display (FED) mode, luminescence is generated by processes in which electrons are accelerated under reduced pressure from the electron tip or electron source to the phosphor layer to thereby excite the sons-5 electrons. The photoluminescence (PL) phenomenon is a case where-

CM

The energy source that excites the light emitting central ions is not the electron but the 9 light or the photon. Fluorescents that produce bright light for such

o

30, used in data display devices. ϊ The electroluminescent instrument has many advantages ^ as one type of display ^ in resistance to environmental influences such as vibration and shock, well

C/O

^ wide operating temperature range, wide viewing angle and short reaction time. Although the red and green light luminances have been very high, the blue light luminance has nevertheless been low. A limitation of prior art devices has therefore been the impossibility of producing a full color product of excellent quality. One reason for this limitation is that, in the energy transfer process, to emit blue light, impurities or undesirable chemical states affect the energy levels of the central blue emitting central ions more than the energy levels of the central and red emitting red and green light, respectively.

In addition, it is necessary to develop high purity red and / or green fluorescent materials together with blue fluorescent materials according to the purpose of the display devices. However, a limitation of prior art has been that it is not possible to produce fluorescent materials. with high luminance and high color purity.

As one general fluorescent thin film in the region of blue electroluminescence, ZnS: Tm (ZnS host material doped with Tm) has been studied for several decades. However, this fluorescent material has an al-15 luminance of less than 1 cd / m2 at an operating frequency of 1 kHz. Blue fluorescent material has been considered the most difficult technical problem in this area because blue fluorescent luminance has been much lower than red and green fluorescent fluids.

Later, the luminance of the phosphor formed by thiogallate compounds such as CaGa2S4 and SrGa2S4 has been approximately 12 cd / m 2 at an operating frequency of 60 Hz. The disadvantages of thiogallate compounds are that this compound cannot be grown by atomic layer cultivation because gallium (Ga) does not have a chemical bonding state suitable for atomic debris cultivation and that the price of Ga source material is very high.

25 E. Nykänen et al., Published in 1992 (Proc. Of the 6th Int. Workshop on Electroluminescence, p. 199) the results of research on a Pb-doped CaS (GaS: Pb) dye. In this disclosure, C \ 1 coordinate compounds having a degree of oxidation of +2, such as Pb (thd) 2, ° Pb (dedtc) 2, and halide compounds, were used as Pb precursors. The power of this electroluminescent O <5 30 sensory device corresponded at most to a luminance of 2.5 cd / m operating frequency | 300 Hz, which is much weaker than the equivalent value of the device manufactured in accordance with the present invention in cm. Ultraviolet light was predominantly emitted at a very low Pb concentration. Ultraviolet light and blue umi-3 senses were simultaneously observed in a condition of less than 1.0 mol%.

Blue luminescence was observed only at a concentration of 1.0-1.5 mol% and the best blue color ClE coordinates were (0.13, 0.17).

4 The results of this study thus showed that the color changed continuously with increasing Pb2 + ion concentration.

Another example is a method of growing CaS fluorescent medium doped with Pb in an electroluminescent medium, wherein CaS is mixed with Pb $ or Pb methyl to form a solid source material and grown on the substrate by electron beam evaporation [D. Poelman et al., J. Phys. D .: Appl. Phys. 30: 445 (1997)]. However, it was reported in that document that the properties of the fluorescent film were very poor and not good for use as a blue fluorescent material because PbS 10 formed clumps. Its luminance value was less than 1 cd / m2 at an operating frequency of 20 kHz. This value corresponds to a very low luminance value, given the general tendency for the luminance value to increase as the operating frequency increases. In particular, this document reported that blue emission was only achievable with a Pb2 + ion concentration of less than 1.0 mol% due to cluster formation.

It has been reported that even the fluorescent agents SrS: Pb, SrSe: Pb and the like gave poor results; namely, the emission wavelength changed with the Pb content and the luminance was very low at room temperature (300 K) [N. Yamashita et al., J. Phys. Soc. Japan 53: 419-426 (1984)].

As described above, prior art PbX thin films cannot be uniformly grown due to unstable reactivity of the precursor. Thus, a limitation of prior art fluorescent materials is that they do not exhibit high luminance and high purity of color. Therefore, the present invention has been developed to overcome the problems of the prior art and to meet those needs.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a process

LO

9, using a liquid Pb precursor selected from liquid tetraaryl lead and alkylaryl lead, which saves costs in terms of material, time and labor.

It is another object of the present invention to provide exporters

C \ J

A? 2 process for producing a fluorescent high luminance and high purity dye.

The present invention relates to a process for making a phosphor layer 35. The method of the invention comprises the steps of forming a host material using a culture reaction of the host material, wherein the host material comprises a group II element (M = Ca, Sr, Zn, Ba or Mg) and a group VI element (X = S or Se); adding a Pb2 + ion to the host material for a light emitting central jet, the step of adding the PbX by reacting H2X (X = S or Se) with a Pb precursor selected from the group consisting of tetra-5 aryl lead and alkylaryl lead, with Pb , 2 to 4.0 mol%, and the growth rate of the PbX thin film is in the range of 0.005 to 0.6 A / cycle.

The disclosure discloses a process for making a PbX (X = S or Se) thin film in which a PbX thin film is formed by reacting a Pb precursor with 10 H2X (X = S or Se). The Pb precursor in this context is an organometallic compound wherein Pb is covalently bonded to an organic functional group. Preferably, the PbX thin well is formed at 150 to 500 ° C by atomic layer growth or chemical gas phase growth. The Pb precursor contains a tetravalent lead compound which is a tetraaryl lead or a tet-rival lead compound having alkyl and aryl groups (i.e. alkyltriaryl lead, diacyldiaryl lead or triacyl aryl lead). The alkyl group may include methyl, ethyl, propyl, isopropyl and cyclohexyl groups. The aryl group may include phenyl and benzyl groups.

In more detail, the PbX thin well has been grown according to prior art using the Pb (II) coordination compound as a Pb precursor. However, in the present description, the PbX thin well is grown by atomic layer growth or chemical gas phase growth using a tetravalent organometallic Pb (IV) compound (e.g., tetra-aryl lead). Thus, the film described had good uniformity with respect to the pack-25 filter due to the precursor stability. In particular, a highly uniform PbX thin well can be provided which is applicable to up to 5 large-size substrates such as a 30.5 cm 2 x 30.5 cm (12 µ x 12 ") substrate.

In the invention, the growth of quantitative PbX was monitored by Rutherford? 30 Backscatter Spectrometry (RBS) analysis. The RBS results showed that the composition of g Pb and S corresponds to an approximate 1: 1 ratio. The X-ray diffraction (XRD) c / j method also confirmed that PbX

C/O

the film had a cubic crystal structure, which is a well known crystal structure. Although the PbX membrane used in the RBS and XRD analyzes was very thin, 35 clear XRD peaks were visible. This confirmed that the grown PbS was highly crystalline.

6

From the point of view of space and convenience of the precursor, the coordination compounds mainly used in the manufacture of PbS and PbO thin films according to the prior art are solid. A tetraalkyl lead gradient which is in a liquid state may also be used to form a non-inventive PbX film. It has the advantage of being easy to inject liquid source material into the device, thus saving source material and manufacturing costs. This Pb precursor is also stable in reactivity; thus providing uniformity of film thickness and reproducibility of processes. It also has the advantage that the Pb precursor used does not contain oxygen, which readily binds Pb.

The disclosure discloses a method for producing a phosphor comprising host material regions for accelerating electrons and light emitting regions containing a central light emitter. The fluorescent film is prepared in this invention through a host material growth reaction and a light emitting region growth reaction. In this case, an organometallic compound containing Pb covalently bonded to an organic functional group as described above is used as a precursor, and the Pb precursor is reacted with hfeSm (X = S or Se) and thus added to the PbX host matrix. In this way, the fabrication of a phosphor by the process of the present invention provides a phosphor having a high luminance and a very pure color.

In the process of making a phosphor by adding PbX to the host material by atomic layer growth using an organometallic Pb precursor, the central light emitting Pb2 + ion can be adjusted to be in PbX grown as a Pb2 + dimer. Thus a high luminance and very pure color is obtained for the fluorescent material regardless of the concentration provided that the 5 Pb concentration range is from 0.2 to 4.0 mol% (this range is much wider than that of the tunneling technique).

In other words, when grown, Compound II-VI, such as CaS, CaSe, 30 SrS, SrSe, ZnS, ZnSe, BaS, BaSe, MgS, MgSe and the like, PbX is added by the method described above and the product can act as a fluorescent. If PbX is then grown predominantly of the dimer type, namely, the Pb precursor is formed as an intermediate of the dimer type on the growth surface to change the dimer type of PbX, σ> can be prepared to have a constant color over a wide concentration range. The growth rate of PbX is 0.005-0.6 Å / cycle.

7

As described in the detailed description of an embodiment of the present invention, to form PbX as a dimer type in the process of the invention, PbX can be formed at 150-500 ° C by atomic layer growth. Increasing the axAÄ host material-5 region film and the b x B Ä light-emitting region film in turn, and repeating these processes N times, thus increases the [N x (a x A + b x B)] A fluorescent thin film. Here, "a" is the number of reaction cycles of the host material, and A is the rate of growth of the host material. "b" is the number of PbX growth reaction cycles, and B is the PbX growth rate. In this case, b x B is preferably from 0.005 to 0.6. An "a" host material growth reaction cycle and a "b" light emitting region growth reaction cycle are performed to form a x A A host-mother region film and b x B A light-emitting region film, respectively, and these processes are repeated N times. In this case, the "b" is preferably not more than 2 when the temperature is above 350 ° C.

With the use of atomic layer cultivation, it has traditionally been known that the precursor should not spontaneously decompose at the reaction temperature without a surface reaction. Therefore, when PbX is grown by atomic layer cultivation according to the prior art, Pb (II) compounds having a higher decomposition temperature than the reaction temperature, such as thd and dedtc-20 coordination compounds and halide compounds, have been used as Pb precursors. However, the description shows that a thin film of excellent growth response and well properties can be grown using the precursor formed by the tetravalent bonded Pb meta-organic compound.

By using as the Pb precursor the tetraethyl lead of the invention, which boils at 198 ° C at atmospheric pressure and partially decomposes above 100 ° C, can be used to grow a very uniform PbS thin film o at a reaction temperature above 300 ° C. The reason is that the tertiary level of lead is partially decomposed to form an intermediate which is the preferred form of the chemical variety for the formation of dimeric type PbS with an oxidation degree of +2.

| In a conventional fluorescent bed process with a Pb2 + ion which is added to the host material. formed by a 1-1-VI compound such as CaS, CaSe, SrS, co

SrSe, ZnS, ZnSe, BaS, BaSe, MgS or MgSe have the same cubic crystal structure as the host material and have the same degree of oxidation as the ion formed by Group II element 35. Thus, the Pb2 + ion is added to the host material and replaced with the host material element without the addition of a charge compensator. The Pb2T-8 ion is in cluster or aggregate form as well as in monomeric form. This is evidenced by the experimental fact that excitation spectra and emission spectra are different in the results of the PL study for the products CaS: Pb2 +, CaSe: Pb2 +, SrS: Pb2 *, SrSe: Pb2 +, etc., other peaks are not superimposed. no specific energy transfer explains the spectra [reference document: S. Asano, N. Yamashita and Y. Nakao, Phys. Stat. Soi. (b) 89, 663 (1978)]. For example, in the case of CaS: Pb2 +, changes in the spectrum with Pb2 + were observed to study the state of the monomer. The Pb2 + monomer emits in the ultraviolet region. The results of the study reported only that the wavelengths were 355 and 364 nm for CaSe: Pb and 371 and 380 nm for CaSe: Pb. The PL peaks also shifted toward longer wavelengths with increasing concentration. However, it was not possible to produce material that selectively emits only at a specific wavelength, irrespective of its concentration.

In the case of CaSe: Pb2 +, the monomer emits at 368 nm and the dimer emits at about 500 nm. Even with SrS: Pb, however, the present invention provides an electroluminescence having a single peak at approximately 500 nm, which is a difference from previous studies.

20 CaS: In the case of Pb-1, the Pb2 + ion has a radius of 1.20 A and

The Ca 2+ ion has a radius of 0.99 Å, and thus there is a gate misalignment of about 20% between the Pb 1 ion and the Ca 2+ ion. Addition of a large amount of Pb to the host material results in a weakening of the crystal structure, whereby the EL- (electroluminescence) and CL (loss-diluminescence) properties are reduced, irrespective of the formation of Pb2 + ionic rhythms. The method of the present invention therefore provides an MX: Pb compound replicator in which the Pb2 + ion is in a specific state and can produce EL or CL emission at a specific wavelength

C \ J

irrespective of the concentration range, which does not impair the crystallinity of the host material. The present invention can improve the luminance and color purity of the luminescent material. The phosphor described may be used as a PL or CL flux.

CL

As described above, the fluorescent material produced by the process of the present invention can also be applied to electro-intensity devices. The structure of such an electroluminescent wavelength includes both the conventional structure and the inverse structure used in the active matrix and the like.

9

Brief Description of the Drawings

The foregoing and other objects and features of the present invention will become apparent from the following description of preferred embodiments, taken in conjunction with the accompanying drawings, in which: Figure 1 is a sectional view showing layers incorporating light emitting central ions added to the phosphor host material;

Fig. 2 schematically illustrates a fission reactor type apparatus as one example of apparatus for atomic layer augmentation of the present invention; Figure 3 is a spectrum showing differences in Pb2 + content

CaS: EL peaks of Pb-solubilizers;

Fig. 4 is a spectrum showing the change in EL peaks as a function of the thickness of the light-emitting central layer of Fig. 1; Fig. 5 shows the structure (a) of an AC-TFELD grown on a transparent substrate and the reverse structure (b) of an opaque substrate, respectively;

Fig. 8 is a luminance-voltage curve showing the luminance of a blue CaS: Pb-electrolytic luminescence device made by the atomic layer cultivation of the present invention;

Figures 7 (a) and 7 (b) are spectra showing the luminance of blue CaS: Pb electroluminescent dyes prepared using Pb (thd) 2 and tetraethyl lead, respectively, as a Pb precursor.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention will be illustrated in detail by the following preferred embodiments with reference to the accompanying drawings.

The Pb2 + ion has a valence electron configuration of 6s2 in baseline. When the ion absorbs energy, the Pb2 + ion electron moves to 6s16p1. When tuned in 30 electrons return from their excited state to baseline, emission occurs. The states of the energy levels are greatly influenced by the states of the ion and the surrounding host material.

This embodiment relates to a process for the production of a blue CaS: Pb-σ> fluorescent material in which most of the Pb2 + ions are selectively in dimer state in the CaS host material suitable for emitting blue luminescence, and thus this fluorescent material can emit luminescence 10 is high and the color purity is good. For comparison, it is known that the luminance of common blue fluorescents decreases as they move near to pure blue. In the case of blue SrS: Cu, Ag fluorescents grown by the magnetron sputtering method, the luminance tended to diminish when doped with the host material to bring the color closer to the pure blue color.

The method for suppressing the phosphor layer simply describes processes for fine-tuning the chemical state of the Pb2 + ion and for increasing the MX: Pb phosphor by adding small amounts of 10 PbX to the MX host materials (here M = Ca. Sr, Ba, Zn or Mg, S or Se). To blend the MX host material with PbX, the MX compound is first grown to a predetermined thickness, then PbX is grown to a predetermined thickness to achieve the desired concentration, and then these processes are repeated. Hereby, the thickness of the once grown MX layer and the thickness of the PbX ~ layer once grown on the MX layer 15 are determined by the desired Pb 2+ ion concentration and growth rates. The basic idea of this kind of growth method is called atomic layer or chemical atomic layer gas phase cultivation.

The process for the preparation of a single phosphor is described below. Most of the Pb2 + ions in the phosphor produced are in the dimeric form of PbS added to CaS.

As shown in Figure 1, when alternating growth of a given thickness of CaS on cycle "a" and growth of a given thickness of PbS on cycle "b" and repeating these processes N times, the thickness T of the CaS: Pb Compound 25 fluorescent layer can be represented by with formula I: 5 T = [(ax A) + (bx B) jx N (I)

(M

LT) ° Herein A and B are the growth rates of CaS and PbS, respectively.

The 2+ 30 Pb ion concentration c is represented by the following mathematical formula li:

CC

Q_ cvj c (mol-%) = (b x B) / [(a xA) + (bx B)] (II)

C/O

The doping with the Pb2 + ion to the desired concentration can be accomplished by controlling the ratio of cycles. The present invention permits the selective growth of Pb2 + ions to emit luminescence from a predominantly dimeric state over a range of excellent crystallinity, unlike in the prior art, where Pb2 + ions in different states may be doped according to the Pb content.

Figure 2 is a schematic representation of a motion wave reactor type apparatus as an example of atomic layer growth in accordance with the present invention.

Atomic Layer Growth is a method that utilizes a surface chemical reaction on a substrate surface. Exemplary processes for growing PbSJ doped II-VI metal sulfide using M precursor (M = Ca, Sr, Zn, Ba or Mg), H 2 S and Pb precursor are described below. Chemical gas phase cultivation can be accomplished by simultaneously injecting all the desired reaction material of the composition or by alternating separate cultures of metal sulfide (MS) and lead sulfide (PbS), in the case of atomic layer cultures, the valves 1-5 shown in Figure 2 are independently or repeatedly controlled sequentially.

1) Valve 1 is opened for injection of M precursor vapor with carrier gas. This allows adsorption of the M precursor reactant on the substrate surface.

2) Valve 2 is opened to inject nitrogen or inert gas. This allows for the removal of non-adsorbed M precursor reactant residues.

3) Valve 3 is opened to inject HaS gas. H2S reacts with the M precursor reactant adsorbed on the substrate surface, thereby increasing the M8 thin film to form one or more volatile by-products.

4) The valve 4 is opened to inject nitrogen or inert gas. This allows for the removal of excess volatile by-product of the reaction between the H 2 S moieties and the M precursor and H 2 S.

^ 5) Processes 1-4 are repeated for a few tens to thousands of 9 cycles.

o

6) The valve 5 is opened to inject the Pb precursor. This will ensure adsorption of the Pb precursor onto the metal sulfide (MS) surface. ^ 7) Nitrogen or inert gas is injected to remove the unabsorbed Pb ~ precursor residue.

a> 8) injecting H28 to react with the Pb precursor adsorbed on the substrate. This causes the PbS thin film to grow and produce volatile by-products.

9) Injecting nitrogen or inert gas to remove one or more volatile by-products of the reaction between H2S and the Pb precursor and H2S.

10) Processes 6-9 may optionally be repeated for two or use-5 cycles.

Because the atomic layer growth process is carried out by the aforementioned processes, it can grow thin films at a growth rate of less than 1 monolayer / cycle and fine-tune the composition of the MS: Pb thin film by controlling the number of cycle repetitions. (Monolayer refers to one layer of a specified compound, such as MX or PbX.) In chemical gas phase cultivation, however, the composition of the thin film can be controlled by controlling the ratio of precursors.

In the prior art, the luminescence colors of the fluorescent materials change with the Pb 2+ ion content in the fluorescent materials. It is contemplated that the Pb2 + ion is in the monomer state at low concentration and that the Pb2 + ion dimer is gradually formed as the Pb2 + ion concentration increases and is present alongside the monomer. It is also contemplated that the Pb 1 'ion cluster is formed above a certain concentration and begins to emit green luminescence. Prior art luminescent luminances are reported to be ~20 due to this cluster. However, the present invention is capable of allowing the Pb2 + ion to be in the dimer state regardless of concentration,

In order to grow Pb ions only in the dimer state, irrespective of their concentration, it is necessary to use a reactant precursor having certain properties. An example is tetraethyl lead which is not according to the invention. This compound is a tetraethyl lead at room temperature but begins to decompose at 100 ° C. It also decomposes readily in a reactor maintained at a reaction temperature of 200 ° C or above. Thereby, Pb2 (C2H5) 6 is formed with high probability of cv ^ (hexaethyldiil lead). Because the Pb-Pb bond is stronger than the Pb-C bond, Pb adsorbs in the dimer state at the surface reaction site.

o 30 This is supported by the fact that the synthesis reaction using tetraethyl lead produces | Pb2 (C2H5) 6 days. Given the ability of Pb ions to aggregate with each other, this reaction should be performed at a low growth rate so as not to adsorb

C/O

to another Pb at the nearest Pb site, for example, at a maximum velocity σ> la 0.2 monolayer / cycle. Doping with Pb can only be done at dimer age if doping is done at the above growth rate. If the propensity for Pb to migrate is higher, the growth rate should be reduced.

13

Once the host material growth reaction has been performed for a few tens to a few thousand cycles, one single PbX growth cycle can also be performed separately between the host material cultures. This allows the intervening Pb 4 'ion dimer not to form clumps nor to aggregate, thereby forming a fluorescent wave that has the ability to emit only dimer-generated luminescence. This phenomenon occurs mainly above a certain temperature, depending on the temperature deviation of the growth medium and the type of precursor used in the reaction.

The precursors having the same reaction properties as the tetraethyl lead used in the above 10 include the tetraalkyl lead of the invention containing a methyl, ethyl, propyl, isopropyl or cyclohexyl group as a alkyl group and a tetraaryl lead according to the invention containing or an aryl group of a benzyl group. Other precursors having similar reaction properties to these compounds may be available for the same use.

In this embodiment, it is described that the Pb 2 'ions are predominantly in the dimer state under special conditions and only one luminescence peak is generated from the dimer state. The present non-embodiment of the invention relates to a CaSiPb electroluminescence device which is capable of emitting highly pure blue luminescence irrespective of the concentration of Pb 4 I ion in a concentration range of 0.6 to 4.0 mol%.

In the process of increasing PbS by reaction of tetraethyl lead with H 2 S after culturing CaS using Ca (thd) 2 (thd = 2,2,8,6-tetramethyl-3,5-heptanedione)! the total Pb2 + ion concentration can be determined by adjusting the repeat ratio, taking into account that the growth rate of PbS at 320 ° C is 0.15 A / cycle and the CaS growth rate is 0.35-0.45 Å / cycle. Since the growth rate of PbS is at most 0.15 A / cycle at up to 400 ° C, the surface coverage per cycle is at most 0.1.

cv ^ This means that no more than one of the ten available ° reaction sites binds with PbS. The formation of aggregates is thus reduced by regulating the number of growth cycles of PbS. | Figure 1 schematically shows a sectional view of a <M MX: Pb thin film grown by such a method.

C/O

The control of the number of a and b cycles of CaS and PbS growth cycles for growth of the phosphor thin film, respectively, allows the presence of Pb2 + - 35 ions in the dimer state regardless of the Pb2 + ion concentration. Table 1 and Figure 3 show that a CaS: Pb fluorescent film 14 according to this embodiment has such properties that it emits a constant luminescence with constant wavelength and color coordinates. Table 1 shows the color coordinates of a fluorescent thin film produced by increasing the Pb2 + ion concentration while maintaining the number of PbS cycles, i.e., the thickness of the 5 PbX shown in Figure 1 at 400 ° C and decreasing the number of CaS cycles.

The color coordinates, with a PbS concentration of about 0.6 mol%, were almost the same as with a concentration of about 2.5 mol%, with little change in luminance. In the table, the value of x is the proportion of red in luminescence and the value of y 10 is the proportion of green in luminescence. The value of z (z = 1 - x - y) corresponds to the proportion of blue color.

table 1

Test results for adjusting Pb2 + content by maintaining the number of PbS cycles and reducing the number of CaS cycles

Pb content CiE-Color coordinate jnnoS -%) ____________________ _________ ...................................... .....

....................................... .......... ™ ............................. X ................. Z .. ..... i JL · -____ "________ Q, 6 _______ 0.15 ________j _ _______ 0.11 ...................___" '"I ^ 0 , 8, ____________ 0.14 ............... 0.10_, "i, o _ 0.15 ___________: o, ii ___________ ______ 1.4 .......... .................................. 0.15 _______ j__________Oio_ 2.0 ______ 0.15 0.11 __2.5] Fig. 3 shows the EL spectra of EL dyes containing phosphor thin films having a Pb2 + ion content of 0.6 mol%, 0.8 mol%, and

CM

^ 1.4 mol%. As shown in Figure 3, the peaks of the spectra occur at almost the same wavelength, although the difference in Pb2 + ion concentrations is more than 2-fold. More specifically, these spectra show one narrow peak, unlike the hours of the 20 hour prior art, which have a few broad, partially overlapping EL cm peaks.

C/O

The results of Table 1 and Figure 3 imply that, according to the method of the present invention, a fluorescent material has been prepared which selectively contains the dimer state of the Pb2 + ion irrespective of Pb2 + concentration, contrary to the prior art, providing blue EL with narrow Pb2 +. concentration range (1 to 1.5 mol%). As the Pb content rises above 4.0 mol%, the crystallinity properties of the host material are reduced and the luminance is greatly reduced.

Figure 4 shows the properties of a fluorescent membrane made by maintaining the number of CaS growth cycles and changing the number of PbS growth cycles, i.e. the thickness of PbS used for CaS doping of the host material. Figure 4b shows the EL spectrum of a CaS: Pb fluorescent material grown at 350 ° C using twice the thickness of PbS relative to a. Curve c is a case where the thickness of PbS is 10 to 3 times that of α. As shown in Figure 4, the greater the PbS thickness, the longer the wavelength position of the peak of the EL spectrum shifts and the wider the peak becomes. The ClE color coordinates also show these results. Table 2 shows the concentration and ClE color coordinates as the number of PbS cultivation cycles changes. The increase of y in the 15 CSE color coordinates indirectly indicates the shift of the peak towards a longer wavelength. In this context, the value of x is the proportion of red and the value of y is the proportion of green. The value of z (z = 1 - x -y) corresponds to the proportion of blue color. This means that the lower the x and y values, the better the purity of the blue color. As shown in Table 2, the growth thickness of PbS 20 influences the luminescence purity of CaS: Pb fluorescent material. If the growth thickness of PbS is even regulated at a state where the Pb content is below 0.1 mol% at a given value, luminescence in the green region is generated.

Table 2

CaS: DIE Color Coordinates of Pb Sitting as a function of PbS growth thickness ^ 25 o .................................. ......................... ............... ........... ...........

Pb concentration ClE-Color coordinate § _____________ (mol%) ..................................... .....................

? ___________________________________________________ X f y £ 0.5 __________________________________ 0.16_1 ................. 0.13 ...................

* _ __1,0 __________________ 0.17 0.19_ £ _____05_ "" "0.16 I______ 0.25 ................:

Si

CD

The results of Figures 3 and 4 and Tables 1 and 2 show that the color coordinates of CaS: Pb-lysing agent are not simply determined by the Pb-16 concentration but also by the state of the Pb2 + ion. These results are in good agreement with the "quantum dot effect", whereby the smaller the semiconductor material particle on the nanometric scale, the larger the forbidden energy belt is, and thus the forbidden energy belt can be controlled through the particle size.

These results demonstrate that the present invention can actually prepare an MX: Pb2 + (M = Ca, Sr, Ba, Zn or Mg; X = S or Se) compound containing a specific form of Pb2 + ion, regardless of the total Pb content . In this embodiment, it was possible to produce a blue CaS: 10 Pb-EL fluorescent material which luminesces at any given wavelength irrespective of Pb content by controlling the PbS growth thickness, i.e., the number of PbS growth cycles at 300-400 ° C.

Because the Pb2 + ion has a valence electron structure of 6s2, it is strongly influenced by the state of the MX ~ host material. The crystalline state of the host material changes with the heating temperature, and the shift in wavelength is thus more or less related to the change in reaction temperature. However, the wavelength displacement rate is not very large compared to the change in growth thickness of PbS.

The results described above are in contrast to the trend in the prior art, whereby the color changes from uit-20 ravioli over blue through green with increasing Pb content.

In the process according to a prior art patent (U.S. Patent 5,314,759), such a green

In order to increase the layer of ZnS: Tb-EL, the atomic layer growth bar having a thickness approximately equal to the light emitting region, including the siliceum emitting central junction, this patent confirms that it is very advantageous for the Tba described above to achieve high luminance bigger. As shown in Table 2, when the growth thickness of the Pb2 + ion is greater in the context of the present invention, the formation of Pb2 + ion groups reduces the color purity of the phosphor. Thus, the present invention demonstrates that a lower growth-g thickness is preferred for sex produced by high luminance blue emission.

The fluorescent material of the present invention, which selectively exhibits only emission by the Pb dimer, cannot be prepared by a physical growth method such as the prior art method of heat treating a powder mixture, a sputter growth method, and a 17 electron beam growth method. It cannot be prepared exclusively by the conventional chemical gas phase cultivation method known in the art. A fluorescent agent capable of predominantly only blue luminescence due to its selective and predominantly dimeric 5 Pb 2+ ions can only be produced by adjusting the PbX growth rate below 1 monolayer / cycle, preferably 0.2 monolayer / cycle, or region 0.005 - 0.6 Ä / cycle.

As described above, it is also very important to control the growth thickness of PbX. As the growth thickness increases, the growth rate of PbX also increases by 10. This means that the coefficient of adhesion of the Pb precursor is higher with PbX than with CaX. Under conditions where the growth temperature is 350 ° C, X-ray diffraction (XRD) results begin to show a peak in metallic Pb and the amount of metallic Pb increases as the growth temperature rises. However, when the growth thickness of PbX is adjusted to a minimum, the peak corresponding to metallic lead is never detected, even above 420 ° C, in which region the peak of the metallic lead is readily visible. This shows that it is very important to keep the growth thickness of PbX low.

The growth rate will vary according to the type of precursor used and the culture reaction system. This is also one of the important variables. When Example 20 was used with Pb (thd) 2 as a Pb precursor for growth of CaS: Pb fluorescent, the growth rate was 10 times higher than for the tetraethyl lead of the invention. In this case, no blue EL fluorescent material with excellent color purity could be obtained and the luminance was also very low.

In another example of adjusting luminescence color through growth rate, ultraviolet light is emitted in the presence of Pb monomer and green luminescence is emitted in the presence of Pb dimer in SrS host material. The experimental results thus imply that when the SrS: Pb phosphor is selectively grown using the Pb2 + ion state,

o

30 selectively produces green fluorescent material which luminesces near At 500 nm. Such a fluorescent is the opposite of known technology, which emits an almost white luminous color.

OO

sens Sensitivity over a wide wavelength range as Pb concentration increases.

σ> The fluorescent material described can be used in an electron fluorescent medium as a high fluorescent material with high color purity and luminance.

18

Figures 5a and 5b show the structure of an AC-TFELD thin-film electroluminescent medium grown on a transparent substrate and an inverse opaque substrate structure.

Figure 5a is one general form of the electroluminescent device according to the invention, and Figure 5b is a typical structure of the active matrix thin-film electroluminescence device according to the invention.

Referring to Figure 5a, the AC-TFELD AC actuator thin film membrane device (AC-TFELD) does not have double insulator structures. A transparent conductive thin film, such as an ITO (indium tin oxide) or ZnO: Al (aluminum doped zinc oxide) film, is formed as a transparent electrode 7 on a transparent substrate 6 such as glass or borosilicate glass. The transparent electrode 7 is then formed with a lower dielectric layer 8. The lower dielectric layer 8 is then formed with a fluorescent thin film 9 containing Pb 2+ light emitting fluxes added by the process of the present invention. The fluorescent film 9 is then formed with an upper dielectric layer 10. A metal electrode 11 such as an Al, Au or W electrode is formed on the upper dielectric layer 10. In this device, therefore, the fluorescent thin film 9 is disposed between the previous and upper dielectric layers 8 and 10. These 2Q dielectric layers allow a strong electric field to be directed to the fluorescent film 9 and also serve to protect the film 9 from the outside environment.

Referring to Figure 5b, the reverse structure of the active matrix thin-film electroluminescence device of the present invention does not form a layer 13 of a refractory metal such as W or Mo on a non-transparent substrate 12 such as silicon or alumina. The metal electrode rod 13 is then formed with a first insulating layer 8.

<M

On the dielectric layer 8, a fluorescent thin film 9 is formed containing the light emitting? 2+ 30 Pb fluxes produced by the process of the present invention. A second insulator is then formed on the phosphor thin film 9 a transparent layer 10 is then formed on the second dielectric layer 10, thereby luminescence is emitted from the fluorescent thin film 9 through the transparent electrode 7.

The process for forming the phosphor thin film 9 is accomplished by atomic layer 35 or chemical gas phase growth using equipment similar to that shown in Figure 2. It is intended for a process for making a thin film of PbX-19 using the reaction of a Pb precursor formed by an organometallic compound with H2X (X = S or Se).

The present invention provides a process for the preparation of a blue fluorescent layer having the high luminance required to produce rich colors in the art formed by an AC-thin film electroluminescent dye (AC-TFELD). As described, a blue active matrix thin-film electroluminescence device may also be prepared. The disclosure also provides a natural color electroluminescent device by applying a fluorescent film 9 to one of three of the three colors of the original fluorescent film. The fluorescent thin film can also be used in the context of the present invention as one of the white fluorescent wells and enables the electroluminescent medium to have natural color luminescence through filtration of white color luminescence.

The thin film of PbS as described may be used for photocopy, infrared detector, etc., and as an electroluminescent device.

In the structure of the electroluminescent device described, the phosphor layer may be formed as a multilayer structure comprising at least two types of thin layers consisting of host materials selected from CaS, SrS, ZnS, BaS and MgS. Because polycrystalline 20 CaS, SrS, ZnS, BaS and MgS thin films all have a cubic structure, especially ZnS, which has excellent crystallinity properties, improves the crystallinity properties of the adjacent well and limits charge overflow. PbS can only be doped with all or some of the layers formed by one type of host material. PbS can also homogenously blend all layers of the host material used.

o In the method described, PbX (X = S or

CVJ

^ Se) thin film by reaction of precursor metal organo-compound using atomic layer growth and atomic layer or chemical gas phase growth techniques as shown in Figure 2, | which uses a compound jet. This method also involves growing a layer of phosphor such as that described above by atomic layer growth or chemical gas phase growth. The fluorescent film is applied to an electroluminescent σ> sensing device.

The description proposes a method for growing a PbX thin well by atomic layer growth or chemical gas phase growth using a reaction of 20 H2X with a Pb precursor containing a tetravalent covalent bond. It can also be used to grow a filler membrane by carrying out processes from II-VI compound semiconductor such as CaS, CaSe, SrS, SrSe, ZnS, ZnSe, BaS, BaSe, Mg8 or 5 MgSe, to grow a host material layer, and processes for growing IV-VI compound such as PbX at certain intervals between the host material layer growth processes. The present invention can also be used to prepare a volatile agent so as to allow the central light-emitting ion, in particular the Pb 2+, to be in a dimeric state within a specifically defined range of conditions.

Various examples of variations and modifications of the method of manufacture of the electro-inensic device exist, although they are not discussed in the detailed description of the present disclosure.

The Pb doped host material polycrystalline thin-film or multilayer thin films are grown by atomic layer cultivation, Pb doped host material can then be selected from Pb doped CaS, SrS, ZnS, BaS, MgS , CaSe, SrSe, ZnSe, BaSe and MgSe. The Pb precursor may include a tetraaryl lead, a tetravalent lead compound having alkyl and aryl groups, etc. The alkyl group may include methyl, ethyl, propyl, isopropyl and cyclohexyl groups and the aryl group and benzyl groups.

The fluorescent agent further comprises a thin film or at least two thin films. The multilayer structure may be a structure formed by increasing the ZnS layer and the CaS: Pb layer at least once. The multilayer structure may also be a structure formed by increasing the SrS: Pb layer and the CaS.Pb layer at least once. The multilayer structure may also be those formed by growth of the ZnS layer, SrS: Pb layer and

<M

^ CaS: Pb layer at least once. The precursor o 30 formed by the organometallic (MO) lead (IV) compound or the organometallic (MO) lead (! S) compound can be used as the Pb precursor in the multilayer structure.

| In the phosphor layer of the multilayer structure, at least one layer cvj may be a polycrystalline CaX (X = S or Se) thin film doped with 0.2-4.0 mol% PbX (X = S or Se). (The amount of Pb in this case corresponds to S 0.1 to 2.0% atomic percent.) At least one layer in the phosphor layer 35 of the multilayer structure may also be a polycrystalline SrX (X = S or Se) thin film 21 doped with 0, 2 to 4.0 mo PbX (X = S or Se). (The amount of Pb in this case corresponds to 0.1 to 2.0% of the atom.)

For example, no effectoluminescence excipients according to the invention were prepared by blending CaS 0.2 to 4.0 mol% with PbS using tetraethyl 5 lead. The luminances (x, y) of the luminances emitted from the devices were 0.12 to 0.19 at x and 0.07 to 0.20 at y. These colors are close to pure blue. Specifically, when the devices were made using the dimer state of the predominantly Pb2 + ion, the luminescence color of the device was in the narrow range (0.14, 0.07) to (0.15, 0.15). corresponding to the maximum EL peak in the wavelength range 440 nm to 450 nm. This value corresponds to the blue color of the ideal cathode ray tube. The maximum luminance was above 1G0cd / m2 at 80 Hz, which was a few to tens of times the equivalent values of prior art devices.

Figure 6 shows a luminance curve of a blue non-invention CaS: Pb electroluminescent device using atomic layer growth at 400 ° C. The results showed that, in these manufacturing ratios, the luminance was 85 cd / m2, with an operating voltage of 25 V higher than the threshold voltage and a maximum luminance higher than that value. The results showed a color purity of 20 us (0.15, 0.10), i.e. close to pure blue. This luminance value is 30 times higher than the result obtained by E. Nykänen in Finland.

The EL spectral data of the CaS: Pb electroluminescence instrument prepared as described was compared with that obtained with the instrument prepared using the thb compound of Pb. These devices were made using the same equipment and the same growth conditions but from different Pb precursors. Figures 7a and 7be show the electroluminescence spectral characteristics of electroluminescence devices prepared using thd compounds.

C \ J

and tetraethyl lead, respectively. As shown in Fig. 7b, the wavelength 9 at the maximum EL peak of the electroluminescent device made using tetraethyl lead is 440 ~ 445 nm and the peak width g has a half height value of less than 60 nm. However, the peaks of the spectrum given by a medium made using Pb (thd) 2 are very broad and

C/O

^ are located in a longer wavelength range.

The present invention can also be applied to the growth of a Pb2 + ions-containing phosphor layer containing other ions as co-dopants added to improve the luminance properties,

Although the present invention has been described only with respect to certain preferred embodiments, other modifications and variations may be made without departing from the spirit and scope of the present invention as set forth in the following claims.

δ

(M

i tn o i o

X

I do not

CL

(M

C/O

r ^ δ σ>

Claims (11)

23 A process for producing a phosphor layer, characterized in that it comprises the steps of forming a host material using a host material growth reaction, wherein the host material comprises a Group II element (M = Ca, Sr, Zn, Ba or Mg) and a Group VI element (X = S or Se); adding Pb2 + - ion to the host material as light-emitting centers, the step of adding the step to form PbX by reacting 10 H2X (X-S or Se) with a Pb precursor selected from tetraaryl oil and alkylaryl lead, whereby the Pb2 content of the phosphor layer is + - 4.0 mol% and the growth rate of the PbX thin film is in the range of 0.005 to 0.8 A / cycle. Process according to Claim 1, characterized in that at least one of the methyl, ethyl, propyl, isopropyl, cyclohexyl, phenyl and benzyl groups is selected as the alkyl group or the aryl group of the tetraaryl lead and the alkylaryl lead. 3. The process of claim 1, wherein the host material is an II-VI compound formed by reacting M-essase with H2X (X = S or Se), Process according to Claim 1, characterized in that the growth reaction and the reaction with the addition of the central light emitting medium are carried out simultaneously and the Pb 2+ ion content is regulated by the ratio of the M precursor content to the Pb precursor content. The process according to claim 1, characterized in that the growth reaction and the reaction with the addition of a central light emitting intermediate are carried out alternately. A method according to claim 5, characterized in that it further comprises the step of forming a fluorescent thin film to a thickness of [N x (A + B)] A, this step being carried out by repeating N times the following steps; (m grow the thin film of the host material region to thickness AA using the host material growth reaction; grow the PbX (X = S or Se) §> thin film to thickness B Ä using a light emitting central addition step. A method according to claim 6, characterized in that the Pb2 + ion concentration is regulated by the ratio of the thickness of the thin film prevailing in the region of the host material to the thickness of the PbX thin film. The process according to claim 6, characterized in that the thickness (B A) of the PbX thin film is in the range of 0.005 to 0.6 Λ. A method according to claim 6, characterized in that the amount of!, A>! host material growth reaction cycles and the number "b" of the light emitting region growth reaction cycles separately with the number of repetitions being N. 10 10, the method of claim 9, wherein the number of light emitting region growth reaction cycles is at most 2, . 11, The method according to claim 1, wherein the growth reaction and the reaction involving the addition of a central light emitting medium are carried out at a temperature in the range of 150 to 500 ° C, δ (M tn oio X en CL (M CO δ σ> 25