JP2003321702A - Alloy fine powder, electrically conductive paste obtained by using the same and electroluminescence element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide alloy fine powder with which the backing temperature of electrically conductive paste is reduced since it can be melted and integrated at a low temperature, thus damage to an organic electroluminescence layer can be reduced, and a back electrode having sufficient heat resistance and durability can be formed after backing, to provide electrically conductive paste obtained by using the same, and to provide an EL element obtained by using the electrically conductive paste. <P>SOLUTION: The alloy fine powder is formed of an alloy having a melting point of ≤250°C, and the particle diameter thereof is controlled to ≤300 nm. The electrically conductive paste contains the alloy fine powder in a ratio of 50 to 98 wt.% to the total content of the solid components. The EL element is obtained by applying the electrically conductive paste so as to be a film shape, thereafter backing the same at a temperature higher than the melting temperature of the alloy fine powder and also lower than the heat resisting temperature of a light emitting layer, and forming a back electrode. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alloy fine powder used for a conductive paste, a conductive paste using the same, and an electroluminescent element (hereinafter referred to as "EL element") having a back electrode formed using this conductive paste. ) And is related to.

[0002]

2. Description of the Related Art In general, an EL element is formed by forming a thin film transparent electrode (anode) on a transparent substrate such as a glass plate, laminating a light emitting layer having an electroluminescence function on the transparent electrode, and then forming the light emitting layer on the transparent electrode. Further, the back electrode (cathode) is often formed by stacking. Of these, as the light emitting layer, recently, a light emitting material, a fluorescent dye, an electron transporting material, a hole transporting material or the like is dispersed in a binder resin, or a polymer having a hole transporting property is used as the binder resin. So-called organic, single-layer or multi-layer light emitting layers are becoming popular.

The back electrode is generally formed of a vacuum deposited film of metal or alloy. However, since the step of forming the back electrode by a so-called vacuum process such as a vacuum deposition method is usually performed in a batch method, there is a problem that productivity is low and cost is high.

[0004]

Therefore, the inventor has applied a conductive paste containing fine particles of a metal or an alloy forming a back electrode and a binder in a film form on the light emitting layer and then baking it. It was studied to form the back electrode by burning and removing the binder and melting and integrating a large number of fine powders. However, the heat resistance of the light emitting layer, which is required from the glass transition temperature, melting temperature, and thermal decomposition temperature of the binder resin forming the organic light emitting layer, or the thermal decomposition temperature of the light emitting material and other components dispersed in the binder resin. The temperature is generally 200 ° C
Is less than. Therefore, the organic light emitting layer is weak against heat.

On the other hand, considering that electrons are smoothly injected into the organic light emitting layer as the cathode, the back electrode needs to be formed of a metal or an alloy having a work function as small as possible. The melting point of the or alloy is usually higher than the heat resistant temperature of the organic light emitting layer described above. In addition, considering that a large number of fine powders are sufficiently melted and integrated to form a back electrode having good conductivity that is uniform and sufficiently follows the surface shape of the light emitting layer, the baking temperature of the conductive paste is considered. Needs to be set to a temperature higher than the melting point of the above metal or alloy.

Therefore, when the back electrode is formed by baking the conductive paste on the organic light emitting layer, there is a problem that the light emitting layer is deteriorated due to the high temperature during the baking. ,Have difficulty. Therefore, the inventor has found that the melting point of the alloy is 200 ° C. or less, including fine powder formed of In simple substance having a low work function of 156.6 ° C. and a low work function, or a low melting point metal such as In or Sn. It was examined to reduce the baking temperature of the conductive paste and reduce the damage to the organic light emitting layer by using a fine powder of a low melting point alloy whose composition was adjusted so that

However, the back electrode formed by baking a metal or alloy having a low melting point naturally has a problem that the heat resistance is not sufficient. In particular, the back electrode formed of In alone or the back electrode formed of a low melting point alloy containing In, Sn, etc., after the above layers are laminated and formed,
In addition to being easily melted due to the thermal history after element formation, such as when the entire element is passivated at a temperature lower than the heat-resistant temperature of the light emitting layer, In and Sn are precipitated in whiskers when resolidifying after melting. However, there is a problem that the light emitting layer is easily damaged or a short circuit is easily generated between the light emitting layer and the transparent electrode.

[0008] Further, although In alone is easily oxidized in a relatively short period of time, and the oxide of In has conductivity, its work function is not within the numerical range suitable for the cathode, and it is used as a back electrode by oxidation. There is also a problem that the durability of the back electrode becomes insufficient because it does not function. A main object of the present invention is to melt and integrate at a low temperature like fine powders having a low melting point such as those made of the above simple substance of In, so that it is possible to lower the baking temperature of the conductive paste. A new alloy fine powder that can reduce the damage to the organic light-emitting layer and, after baking, can form a back electrode having sufficient heat resistance and durability as compared with the above low melting point one. To provide.

Another object of the present invention is to provide an electroconductive paste using the above alloy fine powder, and an EL element in which a back electrode is formed using this electroconductive paste.

[0010]

MEANS FOR SOLVING THE PROBLEMS AND EFFECTS OF THE INVENTION When the particle size of fine metal powder is reduced to a range of several hundreds nm or less,
It is known that the so-called Kubo effect is that the thermodynamic properties such as specific heat and magnetic susceptibility of the fine powder as a group are remarkably different from those of ordinary macro-sized metals. Focusing on this Kubo effect, the inventor studied that the melting temperature as a group of the fine particles formed by the alloy is made finer to lower the melting temperature than the melting point of the alloy itself.

As a result, when the grain size of the alloy fine powder formed of the alloy having a melting point of 300 ° C. or lower is reduced to 300 nm or less, (1) the melting temperature of the alloy fine powder as a group is changed by the Kubo effect. , The above-mentioned heat-resistant temperature of the organic light-emitting layer is lowered, and accordingly, the baking temperature of the conductive paste is lowered to the same or lower than the above heat-resistant temperature to reduce damage to the organic light-emitting layer during baking. What you can do (2) Since the back electrode after melting and integrating by baking returns to the metal of the original macro size and shows the melting point of the alloy itself that formed fine powder,
By selecting the type of the alloy, it is possible to form a back electrode having excellent heat resistance that does not melt due to the thermal history after the element is formed, and basically, the alloy is easily oxidized like In simple substance, The inventors have found that the durability of the back electrode can be improved because the function as the back electrode is not lost, and the present invention has been completed.

Therefore, the invention according to claim 1 is made of an alloy having a melting point of 300 ° C. or less and a grain size of 300 nm.
It is an alloy fine powder characterized by the following. In order to form the back electrode having excellent heat resistance and durability, the melting point of the alloy forming the fine powder may be higher than the heat resistant temperature of the organic light emitting layer, and particularly 200 ° C. or higher. preferable. As described above, the heat-resistant temperature of the organic light-emitting layer is often less than 200 ° C., and the EL element is not treated or used at a higher temperature than that. If the temperature is higher than or equal to ℃, the back electrode formed by baking may melt due to the thermal history after element formation, or the metal contained in the alloy may precipitate as whiskers when resolidifying after melting. Absent.

Therefore, the invention according to claim 2 is the fine alloy powder according to claim 1, characterized in that it is formed of an alloy having a melting point of 200 ° C. or higher. The degree of decrease in melting temperature of the alloy fine powder due to the Kubo effect described above increases as the particle size decreases. That is, the melting temperature tends to decrease. However, it is not easy to manufacture a fine powder having a particle size of less than 10 μm. Further, even if it can be produced, the melting temperature becomes too low and it easily aggregates, so that it is not easy to handle and is not practical.
Considering that the fine alloy powder is uniformly dispersed in the conductive paste without melting or agglomerating in a normal working environment to form a back electrode having good characteristics, its particle size is Is preferably 10 nm or more.

Therefore, the invention according to claim 3 is the alloy fine powder according to claim 1, characterized in that the grain size is 10 nm or more. The alloy fine powder may be produced by various methods. However, by reducing the two or more kinds of ions with a reducing agent in a solution containing ions of two or more kinds of metal elements constituting the alloy, The alloy fine powders formed by the reduction precipitation method in which they are simultaneously precipitated have uniform individual particle sizes and a sharp particle size distribution. This is because the reduction reaction proceeds uniformly in the solution.

Therefore, the above alloy fine powder can be more uniformly melted during baking, and a large number of alloy fine powders can be sufficiently melted and integrated to form a uniform and light emitting layer surface. It is possible to form a back electrode having good conductivity that sufficiently follows the shape. Therefore, in the invention according to claim 4, in a solution containing ions of two or more kinds of metal elements constituting the alloy, the two or more kinds of ions are
The fine alloy powder according to claim 1, wherein the fine alloy powder is formed by reducing with a reducing agent to simultaneously precipitate.

As the reducing agent used in the above-mentioned reduction precipitation method,
Trivalent titanium compounds are preferred. When a trivalent titanium compound such as titanium trichloride is used as the reducing agent, titanium ions are hardly consumed during the reduction and precipitation of the metal elements that compose the alloy (along with the ions of the metal elements that compose the alloy). Since it does not precipitate a large amount), there is an advantage that the solution after the alloy fine powder is deposited and formed can be regenerated by electrolytic regeneration to be regenerated into a state that can be used for producing the alloy fine powder.

Therefore, the invention according to claim 5 is the alloy fine powder according to claim 4, characterized in that a trivalent titanium compound is used as a reducing agent. A conductive paste using the above alloy fine powder contains the alloy fine powder and a binder such as a resin as a solid content as in the conventional case. In such a conductive paste, it is preferable to increase the ratio of the binder fine powder and the ratio of the alloy fine powder in order to form a uniform back electrode having good conductivity by baking at a lower temperature for a shorter time. . That is, it is preferable that the proportion of the fine alloy powder in the total solid content is 50% by weight or more.

However, if the proportion of the binder is too small, the film forming property of the conductive paste may be deteriorated, which may rather make it impossible to form a uniform back electrode. It is preferable that the ratio of the alloy fine powder to 98% by weight or less. Therefore, the invention according to claim 6 includes the alloy fine powder according to claim 1 as a solid content and a proportion of the alloy fine powder in the total solid content of 50 to 98% by weight. Is a conductive paste.

When a back electrode is laminated on the organic light emitting layer using the above conductive paste to form an EL device,
After applying the conductive paste onto the light emitting layer, baking is performed at a temperature not lower than the melting temperature of the fine alloy powder reduced to the heat resistant temperature of the light emitting layer or lower by the Kubo effect and lower than the heat resistant temperature of the light emitting layer. Then, while reducing the damage to the organic light-emitting layer, the fine alloy powder is melted well, and a large number of fine powders are sufficiently melted and integrated, so that the surface shape of the light-emitting layer is uniform. It is possible to form a back electrode that follows and has good conductivity.

Therefore, in the invention according to claim 7, the conductive paste according to claim 6 is applied in a film form on the organic light emitting layer, and the temperature is not less than the melting temperature of the fine alloy powder and not more than the heat resistant temperature of the light emitting layer. The EL element is characterized in that the back electrode is formed by baking at a temperature. Incidentally, JP-A-2001-2003
Claim 1 of Japanese Patent Publication No. 05 comprises two or more kinds of metals,
It discloses an alloy fine powder having a particle size of 1 to 100 nm. However, the alloy fine powder produced here is, as is clear from the description of claim 2 and thereafter of the publication, an alloy having a soft magnetic property to be used for an electromagnetic wave shield, specifically Fe-such as permalloy. Fine powders of Ni alloys that are used for other purposes and are not described at all.

In the first place, the melting temperature of the Fe-Ni alloy is extremely high, for example, 1445 ° C. in the case of permalloy (20Fe-80Ni), and both Fe and Ni have a high work function. It cannot be used as a back electrode formed on the light emitting layer.
Moreover, in the above-mentioned publication, when the grain size of the alloy fine powder formed of an alloy having a melting point of 300 ° C. or less is 300 nm or less,
The Kubo effect can lower the melting temperature, and the back electrode after baking returns to the melting point of the original alloy to improve the heat resistance. I haven't.

Therefore, the invention described in the above publication does not disclose or suggest the present invention.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below. [Alloy Fine Powder] As described above, the alloy fine powder of the present invention is formed of an alloy having a melting point of 300 ° C. or less, and has a particle size of 30.
It is characterized in that the thickness is 0 nm or less. The melting point of the alloy is 30
Limiting the temperature to 0 ° C. or lower is that for a high melting point alloy having a melting point higher than 300 ° C., the melting temperature of the alloy fine powder can be adjusted to that of the organic light emitting layer even if the particle size is adjusted to an appropriate range of 300 nm or less. This is because it cannot be lowered below the heat resistant temperature. In order to lower the melting temperature of the alloy fine powder to the heat resistant temperature of the organic light emitting layer or lower by the Kubo effect, it is necessary to set the melting point of the alloy, which is the starting point, to 300 ° C. or lower.

As described above, the melting point of the alloy may be higher than the heat-resistant temperature of the organic light emitting layer, particularly 200 ° C., in order to form a back electrode having excellent durability.
The above is preferable. The metal element forming the alloy is not limited to this, but for example, Ag (melting point 961.
93 ° C., work function 4.26 eV, Au (melting point 106
4.4 ° C., work function 5.1 eV), Al (melting point 660.
4 ° C., work function 4.28 eV), Bi (melting point 271.3
C, work function 4.34 eV), Ca (melting point 839 C, work function 2.9 eV), Cu (melting point 1083.4 C, work function 4.65 eV), Ga (melting point 29.78 C, work function 4.3 eV). ), In (melting point 156.6 ° C., work function 4.09 eV), K (melting point 63.65 ° C., work function 2.
28 eV), Li (melting point 180.5 ° C., work function 2.9)
3 eV), Mg (melting point 648.8 ° C., work function 3.66)
eV), Na (melting point 97.81 ° C, work function 2.36e)
V), Pb (melting point 327.5 ° C., work function 4.25e
V), Sn (melting point 231.97 ° C., work function 4.42e)
V), Zn (melting point 419.6 ° C., work function 3.63e
V), and the like.

The alloy is formed by selecting at least two kinds of metal elements from the above. The criteria for selection are as follows. Since the work function of the alloy is a value close to the smallest value among the work functions of the metal elements forming the alloy, at least one of the metal elements is close to the value of the work function of the target alloy. Select a metal element with a low work function. Select a combination of metal elements whose melting point is not lower than the heat resistant temperature of the element and not higher than 300 ° C. as described above. In the combination of metal elements that can satisfy the above two criteria, the content ratio of each metal element is set in order to achieve the work function and melting point of the target alloy.

A specific example of the combination of the metal elements forming the alloy is not limited to this, but is, for example, 92In.
-8Ag alloy (melting point 210 ° C, work function 4.1 eV),
96.5Sn-3.5Ag alloy (melting point 221 ° C, work function 4.2eV), 96.5Sn-3Ag-0.5Cu alloy (melting point 217 ° C, work function 4.2eV), 99.3S
n-0.7Cu alloy (melting point 227 ° C, work function 4.2e
V) etc. can be mentioned.

The particle size of the fine alloy powder is 3 as described above.
It is set to 00 nm or less. Then, due to the Kubo effect, the melting temperature of the alloy fine powder as a group is lowered below the heat-resistant temperature of the organic light-emitting layer of the EL element, and the baking temperature of the conductive paste is accordingly reduced to the same or lower than the heat-resistant temperature. Can reduce the damage to the organic light emitting layer during baking. As described above, the smaller the particle size of the alloy fine powder, the more
The melting temperature can be lowered, but the particle size is 10
If it is less than nm, it is difficult to manufacture. This is because even if a very fine powder of less than 10 nm is generated in the initial stage of the process of producing an alloy fine powder by a reduction precipitation method described later, a plurality of fine powders are immediately aggregated and integrated to form a fine powder. This is because the alloy fine powder having a larger particle size is generated from the core of the growth of Al.

Even if an alloy fine powder having a particle size of less than 10 nm can be produced, the alloy fine powder having such a small particle size has a remarkably low melting temperature of several tens of degrees Celsius or less and is easily aggregated. . Therefore, when the conductive paste is produced, it is necessary to prevent the alloy fine powder from being fused and the like even while being melted, and thus it is not easy to handle and not practical. Therefore, the particle size of the alloy fine powder is preferably 10 nm or more.

Considering that the baking temperature of the conductive paste is lowered to further improve the effect of reducing the damage to the organic light emitting layer and the handling of the alloy fine powder is facilitated, the grain size of the alloy fine powder is considered. Even within the above range, the diameter is preferably about 70 to 120 nm. In the present invention, the particle size of the alloy fine powder is defined by the value measured using the scanning electron microscope. Specifically, a scanning electron micrograph of the alloy fine powder was taken, and the actual size was 1.8 μm × 2.4 μm.
The particle diameters of all the alloy fine powders falling within the rectangular range are measured, and the average value is used as the particle diameter of the alloy fine powders.

The fine alloy powder can be produced by the reduction precipitation method as described above. In the reduction precipitation method, first, a reducing agent, for example, a trivalent titanium compound such as titanium trichloride, and a complexing agent, for example, trisodium citrate, are dissolved in a solution (hereinafter referred to as a “reducing agent solution”). PH is adjusted to 9 to 10 by adding ammonia water or the like. As a result, the trivalent titanium ion forms a coordination compound by combining with the complexing agent, and the activation energy when oxidizing Ti (III) to Ti (IV) becomes low and the reduction potential becomes high. .
Specifically, the potential difference between Ti (III) and Ti (IV) exceeds 1V. This value is Ag among the metallic elements exemplified above,
Of Au, Bi, Cu, In, Pb, Sn, and Zn,
The value is remarkably higher than the reduction potential from a predetermined valence ion to a metal state (zero valence). Therefore, the ions of these metal elements can be efficiently reduced and precipitated.

Next, to the above reducing agent solution, a solution containing ions of two or more kinds of metal elements constituting, for example, the above-mentioned In-Ag alloy is added. Then Ti (III)
Acts as a reducing agent, and when it itself oxidizes to Ti (IV), it is possible to produce fine alloy powder by reducing ions of the above-mentioned two or more metal elements and precipitating them in the liquid at the same time. it can. The fine alloy powder produced by the reduction precipitation method has a uniform grain size and a sharp grain size distribution. this is,
This is because the reduction reaction proceeds uniformly in the system.

In order to adjust the grain size of the fine alloy powder in the reduction precipitation method, reaction conditions such as reaction time, reaction temperature and stirring speed may be specified. In the reduction precipitation method,
In order to control the composition of the alloy forming the alloy fine powder,
The reduction potential of the reducing agent solution may be adjusted by adjusting the concentration of the ions of the metal elements constituting the alloy contained in the solution, or by changing the type and addition amount of the complexing agent. As the complexing agent, in addition to trisodium citrate, sodium tartrate, tartaric acid, sodium gluconate, sodium acetate, ethylenediaminetetraacetic acid, sodium thiosulfate and the like can be mentioned.

The reducing agent solution after depositing the alloy fine powder can be repeatedly used for production of the alloy fine powder by the reduction precipitation method by performing electrolytic regeneration.
That is, by applying a voltage such as by putting the reducing agent solution after the alloy fine powder is deposited in the electrolytic cell, Ti (IV)
If it is reduced to Ti (III), it can be used again as a reducing agent solution for electrolytic deposition. This is because titanium ions are hardly consumed during electrolytic deposition, that is, a large amount of titanium ions are not deposited together with the metal element to be deposited.

Of the above-exemplified metallic elements, Ag and A
Metal elements other than u, Bi, Cu, In, Pb, Sn, and Zn, that is, Al, Ca, Ga, K, Li,
Mg, Na and the like cannot be deposited by a reduction deposition method using a trivalent titanium compound as a reducing agent. Therefore, when forming alloy fine powder from an alloy containing these metal elements, it is necessary to manufacture it by another method. As the method, for example, a metal that cannot be deposited by the reduction precipitation method by a vapor phase coating method or the like on the surface of a fine powder having a particle size of less than 300 nm that is previously formed of a metal that can be deposited by the reduction precipitation method. And the like. In such a method, since the original fine powder has a small particle diameter, the metal coated on the surface can be diffused inside the fine powder to be alloyed by, for example, heat treatment.

[Conductive paste] The conductive paste of the present invention contains the above alloy fine powder and a binder such as resin as a solid content, and the ratio of the alloy fine powder to the total solid content is 50 to 98. It is defined as% by weight. The reason why the ratio of the fine alloy powder is limited to the above range is as described above. In addition to improving the film forming property of the conductive paste, in consideration of forming a uniform back electrode having good conductivity by baking at a lower temperature for a shorter time, the alloy fine powder accounts for the total solid content. Even within the above range, the proportion is preferably 80 to 95% by weight.

As the binder, any of various conventionally known compounds having film-forming properties and adhesive properties can be used. Examples of such a binder include a thermoplastic resin, a curable resin, a liquid curable resin, and the like, and particularly preferably, an acrylic resin, an epoxy resin, a fluorine resin, a phenol resin, or the like can be given. The conductive paste is produced by dispersing alloy fine powder and a binder in a suitable solvent. Further, the solvent may be omitted by using a liquid binder such as a liquid curable resin.

[EL Element] In the EL element of the present invention, the above-mentioned conductive paste is applied in a film form on the organic light emitting layer, and the temperature is not lower than the melting temperature of the alloy fine powder and not higher than the heat resistant temperature of the light emitting layer. The back electrode is formed by baking. Various coating methods such as a bar coating method, a spray coating method and a roll coating method can be adopted as a method for applying the conductive paste in a film form on the organic light emitting layer, as well as a screen printing method and an intaglio offset printing method. It is also possible to employ various printing methods such as. According to the printing method, the back electrode can be patterned.

The baking temperature of the conductive paste must be above the melting temperature of the alloy fine powder and below the heat resistant temperature of the light emitting layer as described above. At a baking temperature within this range, when the conductive paste applied in a film form on the organic light emitting layer is baked, a large number of fine powders are sufficiently melted and integrated while reducing damage to the light emitting layer. It is possible to form a back electrode that is uniform and sufficiently follows the surface shape of the light emitting layer and has good conductivity.

Moreover, since the formed back electrode has the melting point of the alloy, which is higher than the melting temperature of the alloy fine particles, it is excellent in heat resistance so that it will not be melted due to the heat history after the element is formed. Since it does not easily oxidize like a simple substance and loses its function as a back electrode, it has excellent durability. The EL element after the formation of the back electrode is subjected to passivation treatment as in the conventional case and then used.

The layers other than the back electrode, which form the EL element, can be constructed in the same manner as in the prior art. For example, in an EL device having a structure in which a thin film transparent electrode (anode) is formed on a transparent substrate, and an organic light emitting layer having an electroluminescence function and a back electrode are laminated in this order on the transparent substrate, the transparent substrate is Alternatively, a glass plate or a transparent plastic plate can be used.

Examples of the thin film transparent electrode include indium oxide, tin oxide, ITO (indium tin composite oxide), IXO [In ₂ O ₃ (ZnO) m hexagonal layered compound] and the like. These transparent electrodes can be formed by a reactive ion plating method, a reactive sputtering method, a plasma CVD method, or the like. As described above, as the organic light emitting layer, a light emitting material, a fluorescent dye, an electron transporting material, a hole transporting material, or the like is dispersed in the binder resin, or the binder resin has a hole transporting property. There may be mentioned a single-layer or multi-layer light emitting layer using a polymer.

The alloy fine powder and the conductive paste of the present invention are not limited to the formation of the back electrode of the above EL element, and are required to have a low baking temperature and high heat resistance and durability after baking. It can be used for various purposes.

[0043]

Example (Preparation of fine alloy powder) Example 1 80 g of titanium trichloride and sodium citrate dihydrate 9
After dissolving 1.5g in deionized water, the liquid temperature is adjusted to 3
The pH was adjusted to 9 by adding aqueous ammonia while maintaining the temperature at 5 ° C to obtain about 900 ml of the reducing agent solution.

Indium (III) chloride tetrahydrate [I
and nCl ₃ · 4H ₂ O] 10.8 g, silver chloride (AgCl), or the
A solution containing In and Ag ions was obtained by adding 0.46 g and 10 ml of hydrochloric acid to ion-exchanged water and dissolving them.
0 ml was prepared. Then, this solution is added to the above reducing agent solution, and ion-exchanged water is further added to make the total amount 1
It was adjusted to 1 liter and the reaction was carried out with stirring while maintaining the liquid temperature at 35 ° C. Also, after starting the reaction, p
The reaction was carried out while adjusting H to 9, and when 5 minutes had elapsed from the start of the reaction, the solid content precipitated in the liquid was immediately filtered off, washed with water and dried to obtain a fine powder.

When the composition of the obtained fine powder was measured by ICP emission spectrometry, it was confirmed to be a 92In-8Ag alloy (melting point 210 ° C, work function 4.1eV). Further, when the above alloy fine powder was observed by a scanning electron microscope, it was confirmed that the particle diameters thereof were almost uniform. In addition, the particle size of all alloy fine powders whose actual dimensions are in the rectangular range of 1.8 μm × 2.4 μm, which are photographed by the scanning electron microscope, are measured, and the average value is obtained. It was 100 nm.

Further, the melting temperature of the fine alloy powder was measured by the TMA method and found to be 185 ° C. Comparative Example 1 14.3 g of silver chloride (AgCl) and 10 ml of hydrochloric acid were added to ion-exchanged water and dissolved to prepare 50 ml of a solution containing Ag ions. Then, this solution was added to the same reducing agent solution used in Example 1, and ion-exchanged water was further added to adjust the total amount to 1 liter, and the reaction was performed while stirring and maintaining the liquid temperature at 35 ° C. I went. After the start of the reaction, the reaction was performed while adjusting the pH to 9 with aqueous ammonia, and when 5 minutes had elapsed from the start of the reaction, the solid content precipitated in the liquid was immediately filtered off, washed with water and dried. A fine powder of Ag was obtained.

When the obtained fine powder was observed with a scanning electron microscope, it was confirmed that the particle diameters thereof were almost uniform. Also, the particle diameters of all the fine powders whose actual dimensions are in the rectangular range of 1.8 μm × 2.4 μm, which were photographed by the scanning electron microscope, were measured, and the average value was calculated. It was 100 nm. Further, the melting temperature of the fine powder was measured by the TMA method and found to be 475 ° C.

Comparative Example 2 Indium (III) chloride tetrahydrate [InCl ₃ .4H ₂ O]
9.4g, silver chloride (AgCl) 1.2g, 10ml
By adding the hydrochloric acid and the ion-exchanged water to dissolve,
50 ml of a solution containing n and Ag ions was prepared. Then, this solution was added to the same reducing agent solution used in Example 1, and ion-exchanged water was further added to adjust the total amount to 1 liter, and the reaction was performed while stirring and maintaining the liquid temperature at 35 ° C. I went. After the start of the reaction, the reaction is performed while adjusting the pH to 9 with aqueous ammonia, and when 5 minutes have elapsed from the start of the reaction, the solid content precipitated in the solution is immediately filtered off, washed with water and dried. A fine powder was obtained.

When the composition of the obtained fine powder was measured by ICP emission spectrometry, it was confirmed to be an 80In-20Ag alloy (melting point: 350 ° C., work function: 4.1 eV). Further, when the above alloy fine powder was observed by a scanning electron microscope, it was confirmed that the particle diameters thereof were almost uniform. In addition, the grain size of all alloy fine powders whose actual dimensions fall within the rectangular range of 1.8 μm × 2.4 μm, which were photographed by the scanning electron microscope, were measured, and the average value was calculated. It was 100 nm.

Further, the melting temperature of the fine alloy powder was measured by the TMA method and found to be 320 ° C. Comparative Example 3 Indium (III) chloride tetrahydrate [InCl ₃ .4H ₂ O]
50 ml of a solution containing In ions by adding 11.7 g and 10 ml of hydrochloric acid to ion-exchanged water and dissolving
Was prepared.

Then, this solution was added to the same reducing agent solution used in Example 1, and ion-exchanged water was further added to adjust the total amount to 1 liter, and the liquid temperature was maintained at 35 ° C. with stirring. The reaction was carried out. After the start of the reaction, the reaction was performed while adjusting the pH to 9 with aqueous ammonia, and when 5 minutes had elapsed from the start of the reaction, the solid content precipitated in the liquid was immediately filtered off, washed with water and dried. In
Of fine powder was obtained. When the obtained fine powder was observed with a scanning electron microscope, it was confirmed that the particle diameters were almost uniform. In addition, by actually measuring the particle diameters of all the alloy fine powders, which are photographed by a scanning electron microscope and have actual dimensions within a rectangular range of 1.8 μm × 2.4 μm,
The average value was 100 nm.

Further, the melting temperature of the fine powder was measured by the TMA method and found to be 130 ° C. The above results are summarized in Table 1.

[0053]

[Table 1]

From the table, 92In- having a melting point of 210 ° C.
It is made of 8Ag alloy and its grain size is 100n.
The fine alloy powder of Example 1 having m is due to the Kubo effect,
The melting temperature could be lowered to 185 ° C.
However, the fine powder of Comparative Example 1 formed of Ag alone having a melting point of 962 ° C. and 80In− having a melting point of 350 ° C.
The fine alloy powder of Comparative Example 2 formed of a 20Ag alloy has a melting temperature of 200 ° C. even if the particle size is 100 nm.
It was not possible to reduce to below. Further, the fine powder of Comparative Example 3 formed of In alone having a melting point of 156.6 ° C. had a melting temperature too low by setting the particle size to 100 nm.

Example 2 8.7 g of tin (II) chloride dihydrate [SnCl ₂ .2H ₂ O]
By adding 0.2 g of silver chloride (AgCl) and 10 ml of hydrochloric acid to ion-exchanged water and dissolving them, Sn and Ag
50 ml of a solution containing the ions of was prepared. Then, this solution was added to the same reducing agent solution used in Example 1, and ion-exchanged water was further added to adjust the total amount to 1 liter, and the reaction was performed while stirring and maintaining the liquid temperature at 35 ° C. I went. After starting the reaction, adjust the pH to 9 with aqueous ammonia.
The reaction was carried out while adjusting the above, and when 5 minutes had passed from the start of the reaction, the solid content precipitated in the liquid was immediately filtered off, washed with water and dried to obtain a fine powder.

The composition of the resulting fine powder was measured by ICP emission spectrometry, which was 96.5Sn-3.5Ag.
It was confirmed to be an alloy (melting point 221 ° C., work function 4.2 eV). Further, when the above alloy fine powder was observed by a scanning electron microscope, it was confirmed that the particle diameters thereof were almost uniform. In addition, the particle size of all alloy fine powders whose actual dimensions are in the rectangular range of 1.8 μm × 2.4 μm, which are photographed by the scanning electron microscope, are measured, and the average value is obtained. It was 100 nm.

Further, the melting temperature of the fine alloy powder was measured by the TMA method and found to be 190 ° C. Comparative Example 4 Tin (II) chloride dihydrate [SnCl ₂ .2H ₂ O] 7.2 g
By adding 1.1 g of silver chloride (AgCl) and 10 ml of hydrochloric acid to ion-exchanged water to dissolve Sn and Ag.
50 ml of a solution containing the ions of was prepared.

Then, this solution was added to the same reducing agent solution used in Example 1, and ion-exchanged water was further added to adjust the total amount to 1 liter, and the liquid temperature was maintained at 35 ° C. with stirring. The reaction was carried out. After the start of the reaction, the reaction was performed while adjusting the pH to 9 with aqueous ammonia, and when 5 minutes had elapsed from the start of the reaction, the solid content precipitated in the liquid was immediately filtered off, washed with water and dried. A fine powder was obtained. When the composition of the obtained fine powder was measured by ICP emission spectrometry, it was confirmed to be an 80Sn-20Ag alloy (melting point 390 ° C, work function 4.1eV).

When the above alloy fine powder was observed with a scanning electron microscope, it was confirmed that the particle diameters thereof were almost uniform. In addition, the particle size of all alloy fine powders whose actual dimensions are in the rectangular range of 1.8 μm × 2.4 μm, which are photographed by the scanning electron microscope, are measured, and the average value is obtained. It was 100 nm. Furthermore, the melting temperature of the alloy fine powder was measured by the TMA method and found to be 360 ° C.

Comparative Example 5 Tin (II) chloride dihydrate [SnCl ₂ .2H ₂ O] 9.0 g
Then, 10 ml of hydrochloric acid and 10 ml of hydrochloric acid were added to and dissolved in ion-exchanged water to prepare 50 ml of a solution containing Sn ions. Then, this solution was added to the same reducing agent solution used in Example 1, ion-exchanged water was further added to adjust the total amount to 1 liter, and the liquid temperature was adjusted to 35 ° C. under stirring.
The reaction was carried out while maintaining After the start of the reaction, the reaction was performed while adjusting the pH to 9 with aqueous ammonia, and when 5 minutes had elapsed from the start of the reaction, the solid content precipitated in the liquid was immediately filtered off, washed with water and dried. Fine powder of Sn was obtained.

When the obtained fine powder was observed with a scanning electron microscope, it was confirmed that the particle diameters were almost uniform. In addition, the particle size of all alloy fine powders whose actual dimensions are in the rectangular range of 1.8 μm × 2.4 μm, which are photographed by the scanning electron microscope, are measured, and the average value is obtained. It was 100 nm. Furthermore, when the melting temperature of the fine powder was measured by the TMA method, it was 21
It was 0 ° C.

The above results are summarized in Table 2 together with the results of Comparative Example 1.

[0063]

[Table 2]

From the table, 96.5S having a melting point of 221 ° C.
The alloy fine powder of Example 2, which was formed of an n-3.5Ag alloy and had a particle size of 100 nm, could have its melting temperature lowered to 190 ° C. due to the Kubo effect. However, the fine powder of Comparative Example 1 formed of Ag alone having a melting point of 962 ° C. and the melting point of 390 ° C. 8
In all of the fine alloy powders of Comparative Example 4 formed of 0Sn-20Ag alloy, the melting temperature could not be lowered to 200 ° C. or lower even if the particle size was 100 nm. Further, the fine powder of Comparative Example 5 formed of Sn alone had a melting temperature of 200 even though the melting point of Sn was 232 ° C.
It could not be lowered to below ℃. Further, the fine powder of Comparative Example 5 had a large work function value because it was formed of Sn alone.

Example 3 8.7 g of tin (II) chloride dihydrate [SnCl ₂ .2H ₂ O]
And 0.17 g of silver chloride (AgCl), 0.034 g of copper (II) chloride dihydrate [CuCl ₂ .2H ₂ O], and 10 ml of
By adding the hydrochloric acid and the ion-exchanged water to dissolve,
50 ml of a solution containing n, Ag, and Cu ions was prepared. Then, this solution was added to the same reducing agent solution used in Example 1, ion-exchanged water was further added to adjust the total amount to 1 liter, and the liquid temperature was adjusted to 35 ° C. under stirring.
The reaction was carried out while maintaining After the start of the reaction, the reaction was performed while adjusting the pH to 9 with aqueous ammonia, and when 5 minutes had elapsed from the start of the reaction, the solid content precipitated in the liquid was immediately filtered off, washed with water and dried. A fine powder was obtained.

The composition of the resulting fine powder was measured by ICP emission spectrometry, which was 96.5Sn-3Ag-.
0.5Cu alloy (melting point 217 ° C, work function 4.2eV)
Was confirmed. Further, when the above alloy fine powder was observed by a scanning electron microscope, it was confirmed that the particle diameters thereof were almost uniform. In addition, the actual size of the image taken by the scanning electron microscope is 1.8 μm ×
The particle diameters of all the alloy fine powders falling within the 2.4 μm rectangular range were measured, and the average value was calculated to be 100 nm.
Met.

Further, the melting temperature of the fine alloy powder was measured by the TMA method and found to be 185 ° C. Example 4 9.0 g of tin (II) chloride dihydrate [SnCl ₂ .2H ₂ O]
And copper (II) chloride dihydrate [CuCl ₂ .2H ₂ O] 0.0
A solution containing Sn and Cu ions 50m by adding 48g and 10ml hydrochloric acid to ion-exchanged water and dissolving
1 was prepared.

Then, this solution was added to the same reducing agent solution used in Example 1, ion-exchanged water was further added to adjust the total amount to 1 liter, and the liquid temperature was maintained at 35 ° C. with stirring. The reaction was carried out. After the start of the reaction, the reaction was performed while adjusting the pH to 9 with aqueous ammonia, and when 5 minutes had elapsed from the start of the reaction, the solid content precipitated in the liquid was immediately filtered off, washed with water and dried. A fine powder was obtained. When the composition of the obtained fine powder was measured by ICP emission spectrometry, it was confirmed to be a 99.3Sn-0.7Cu alloy (melting point 227 ° C, work function 4.2eV).

When the above alloy fine powder was observed with a scanning electron microscope, it was confirmed that the particle diameters thereof were almost uniform. In addition, the particle size of all alloy fine powders whose actual dimensions are in the rectangular range of 1.8 μm × 2.4 μm, which are photographed by the scanning electron microscope, are measured, and the average value is obtained. It was 100 nm. Further, the melting temperature of the alloy fine powder was measured by the TMA method and found to be 195 ° C.

The above results are summarized in Table 3.

[0071]

[Table 3]

From the table, Sn-Ag-Cu alloy and Sn-C
It was confirmed that the melting temperature of the fine alloy powder can be lowered to 200 ° C. or lower by adjusting the melting point and the particle size of the u alloy as well. (Preparation of Conductive Paste) 95 parts by weight of the fine powder produced in each of the above Examples and Comparative Examples and 5 parts by weight of ethyl cellulose as a binder were dispersed in α-terpineol as a solvent to obtain a solid content concentration. Of 55% by weight and the proportion of fine powder in the solid content was 95% by weight.

(Formation of Back Electrode) As a model of an EL element, a glass substrate having an ITO transparent conductive film formed on one surface was prepared.
A 1 μm-thick layer made of polyphenylene vinylidene (PPV) as a polymer having a hole-transporting property and forming an organic light-emitting layer was formed on the transparent conductive film. Next, the conductive paste prepared above is applied onto the PPV layer and baked at 200 ° C. to a thickness of 5 μm.
After forming the back electrode of m, the whole was heated to 170 ° C. for passivation treatment.

Then, the film was cut in the thickness direction and its cross section was observed with a scanning electron microscope.
It was confirmed that in the back electrode formed by using the alloy fine powder, the alloy fine powder was sufficiently melted, integrated and uniformed, and sufficiently followed the surface shape of the PPV layer. . Further, the PPV layer was not damaged by thermal history. On the other hand, the back electrode formed using the fine powders of Comparative Examples 1, 2, 4 and 5 in which the melting temperature of the fine powders was higher than the baking temperature, the melting and integration of the fine powders was insufficient and the back electrode was porous. It was found that they had a structure or did not sufficiently follow the surface shape of the PPV layer.

Further, the back electrode formed by using the fine powder of Comparative Example 3 made of In simple substance, during passivation,
Whisker-like precipitation of In was observed, which indicates that In melted and then resolidified. Then, damage such as the deposited whiskers piercing the PPV layer was observed.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H05B 33/26 H05B 33/26 Z // C22C 13/00 C22C 13/00 (72) Inventor Yoshie Tani Osaka 1-3-3 Shimaya, Konohana-ku, Osaka (72) Inventor Shinji Inazawa 1-3-1 Shimaya, Konohana-ku, Osaka (72) Invented by Sumitomo Electric Industries, Ltd. Toshihiro Sakamoto 1-3 Shimaya 1-chome, Konohana-ku, Osaka City F-term inside Sumitomo Electric Industries, Ltd. (reference) 3K007 AB14 AB18 CA01 CA05 CB01 CC00 DB03 FA01 FA03 4K017 BA01 BA10 BB02 BB05 DA01 EJ01 FB07 4K018 AA40 BA20 BD04 KA33 5G301 DA02 DD01 DE10

Claims (7)

[Claims] 1. A fine alloy powder characterized by being formed of an alloy having a melting point of 300 ° C. or less and having a particle size of 300 nm or less. 2. The fine alloy powder according to claim 1, which is formed of an alloy having a melting point of 200 ° C. or higher. 3. The fine alloy powder according to claim 1, which has a particle size of 10 nm or more. 4. A solution formed by simultaneously precipitating two or more kinds of ions in a solution containing ions of two or more kinds of metal elements constituting an alloy by reducing the two or more kinds of ions with a reducing agent. The alloy fine powder according to Item 1. 5. The fine alloy powder according to claim 4, wherein a trivalent titanium compound is used as the reducing agent. 6. A conductive material comprising the alloy fine powder according to claim 1 as a solid content and a proportion of the alloy fine powder in the total solid content of 50 to 98% by weight. paste. 7. The conductive paste according to claim 6 is applied in a film form on an organic light emitting layer, and at a melting temperature of alloy fine powder or higher,
An electroluminescent element characterized in that the back electrode is formed by baking at a temperature not higher than the heat resistant temperature of the light emitting layer.