JP2002324671A - El phosphor and el element using same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide EL phosphor with little deterioration in brightness with which a dense coating layer can be formed and an EL element using the same, for one used for a display part, illumination of an operating part or the like of electronic equipment. SOLUTION: After phosphor particles 14A are continuously exposed to metal vapor to form a metal thin film on the surface, they are continuously exposed to ozone or oxygen plasma atmosphere to convert the metal thin film into a transparent metal oxide thin film, and form a coating layer 14B on the surface of the phosphor particles 14A, whereby, a dense coating layer can be formed, hence, an EL phosphor 14 with little deterioration in brightness.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an EL phosphor used for illumination of a display section and an operation section of various electronic devices, and an EL device using the same.

[0002]

2. Description of the Related Art In recent years, with the diversification of various electronic devices, there has been an increasing number of electronic devices equipped with a backlight for lighting behind a display panel or LCD so that a display unit can be identified and operated even in darkness. EL elements are increasingly used for backlights.

FIG. 4 shows such a conventional EL element.
This will be described with reference to FIG.

FIG. 4 is a cross-sectional view of a conventional EL device. In FIG. 4, reference numeral 1 denotes a light-transmissive base material such as polyethylene terephthalate. A light transmitting electrode layer 2 made of tin is formed.

[0005] Further, on this, a luminescent layer 5 in which an EL phosphor 4 serving as a base material for light emission is dispersed in a synthetic resin 3, a dielectric layer 6 in which barium titanate or the like is dispersed in the synthetic resin, A back electrode layer 7 of silver or carbon resin connected to the dielectric layer 6 and an insulating layer 8 of epoxy resin, polyester resin or the like are sequentially formed by printing to form an EL element.

The EL phosphor 4 in the luminous body layer 5 has a surface of the phosphor particles 4A obtained by doping zinc sulfide into copper or the like so as to prevent the luminance from being deteriorated by moisture. It is formed by covering with a coating layer 4B on which metal nitride such as metal oxide or aluminum nitride is deposited.

In the above arrangement, when an EL element is mounted on an electronic device and an AC voltage is applied between the light transmitting electrode layer 2 and the back electrode layer 7 of the EL element from a circuit (not shown) of the electronic device, The EL phosphor 4 of the light emitting layer 5 emits light, and this light illuminates the display panel, LCD, or the like of the electronic device from behind, so that the display unit and the operation unit can be clearly identified even when the surroundings are dark. Was something.

[0008]

However, in the above-mentioned conventional EL device, the coating layer 4B of the EL phosphor 4 in the light emitting layer 5 is formed by depositing a metal oxide or a metal nitride. Further, there is a problem that the denseness of the coating layer 4B is rough, the bonding between the particles is insufficient, and the luminance is easily deteriorated under high temperature and high humidity.

An object of the present invention is to solve such a conventional problem, and an object of the present invention is to provide an EL phosphor having less deterioration in luminance even under high temperature and high humidity and an EL element using the same.

[0010]

To achieve the above object, the present invention has the following arrangement.

According to the first aspect of the present invention, after the fluorescent particles are continuously exposed to a metal vapor to form a metal thin film on the surface, the metal thin film is continuously exposed to an ozone or oxygen plasma atmosphere. Into a transparent metal oxide thin film,
An EL phosphor is formed by forming a coating layer on the surface of the fluorescent particles, and the volume of the coated particles expands due to the oxidation treatment after the formation of the metal thin film, and a dense coating layer with many bonds between the particles is formed. Since it can be formed, it has an effect that an EL phosphor with less deterioration in luminance can be obtained.

According to a second aspect of the present invention, in the first aspect, a plurality of coating layers are formed.
Providing a plurality of dense coating layers has an effect that the EL phosphor can be further reduced in luminance degradation.

According to a third aspect of the present invention, in the second aspect of the present invention, the coating layers having different refractive indexes are alternately formed, and the light emitted from the fluorescent particles is hardly reflected on the coating layer and is transmitted. It has the effect that an EL phosphor with good properties can be obtained.

According to a fourth aspect of the present invention, in the second aspect of the present invention, at least one of the coating layers is formed of a solid acid, and ions eluted from the fluorescent particles in high humidity are removed. The capture of the solid acid has the effect of maintaining the insulating properties of the luminous body layer in high humidity and of obtaining an EL luminous body in which the synthetic resin is carbonized, which is less likely to generate so-called black spots.

According to a fifth aspect of the present invention, in the first aspect of the present invention, the coating layer is formed at an ambient temperature of 350 ° C. or less, and a decrease in luminance of the fluorescent particles due to thermal deterioration during the formation of the coating layer is prevented. Has the effect of being able to.

According to a sixth aspect of the present invention, a light-transmitting electrode layer, a light-emitting layer in which the EL phosphor of the first aspect is dispersed in a synthetic resin, and a back electrode layer are provided on a light-transmitting substrate. The EL element is formed by being stacked, and has an effect that an EL element with less luminance degradation can be realized.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to FIGS.

The same components as those described in the section of the related art are denoted by the same reference numerals, and detailed description thereof will be omitted.

(Embodiment 1) Using Embodiment 1,
The invention of the first and sixth aspects of the present invention will be particularly described.

FIG. 1 shows E according to a first embodiment of the present invention.
FIG. 1 is a cross-sectional view of an EL element using an L phosphor, in which 1 is a light-transmitting substrate such as polyethylene terephthalate or a polyimide film, and a sputtering method, an electron beam method, or indium oxide is formed on the entire upper surface thereof. The light transmitting electrode layer 2 is formed by printing a synthetic resin in which tin or the like is dispersed.

Then, a high dielectric synthetic resin 13 such as a fluoro rubber or a cyano resin is added to the base material E as a base material for light emission.
The phosphor layer 15 in which the L phosphor 14 is dispersed, the dielectric layer 6 in which a high dielectric inorganic filler such as barium titanate is dispersed in a high dielectric synthetic resin, and the dielectric layer 6 are connected. A back electrode layer 7 of silver or carbon resin and an insulating layer 8 of epoxy resin, polyester resin or the like are sequentially superposed and printed to form an EL element.

The EL phosphor 14 in the light emitting layer 15
Is formed by covering the surface of fluorescent particles 14A obtained by doping zinc sulfide into copper or the like with a coating layer 14B in order to prevent deterioration in luminance due to moisture.

In the above configuration, when the EL element is mounted on an electronic device and an AC voltage is applied between the light transmitting electrode layer 2 and the back electrode layer 7 of the EL element from a circuit (not shown) of the electronic device, The EL phosphor 14 of the light emitting layer 15 emits light, and this light illuminates the display panel, LCD, or the like of the electronic device from behind, so that the display unit and the operation unit can be clearly identified even when the surroundings are dark. .

Next, a method of manufacturing the above-described EL phosphor 14 will be described.

FIG. 2 is a process diagram of a method for manufacturing an EL phosphor. In FIG. 2, reference numeral 21A denotes a vacuum chamber in which a metal vapor 22 such as aluminum, titanium, or silicon vaporized from a metal deposition source is supplied from the left. Introduced into the vacuum chamber 21A together with the inert gas 23 such as argon gas.

Then, when the bulb 24A is opened from the upper inlet, the fluorescent particles 14A are charged and dropped continuously little by little, the fluorescent particles 14A are exposed to the metal vapor 22,
A metal thin film is formed on the surface.

Since this metal thin film is a metal particle which has not been oxidized yet, the particles are easily bonded to each other even at a relatively low temperature as compared with a case where an oxidized metal oxide is deposited, and the fluorescent particles 14A are densely formed. Can be covered.

The fluorescent particles 14A have a plurality of coating layers 1
In the case of forming 4B, the valve 24B is opened, the valve 24C is closed, and the fluorescent particles 14A on which the metal thin film is formed are transferred upward by the transfer tube 25A and dropped again into the vacuum chamber 21A. A metal thin film having a predetermined thickness is formed by repeating the process several times.

Next, the valve 24C is opened, and the valve 24B is opened.
Is closed, the fluorescent particles 14A on which the metal thin film is formed by the transfer tube 25B are supplied with oxygen gas 26 from the left side,
This is transferred above the vacuum chamber 21B, which has been turned into plasma by the plasma device 27.

Then, when the fluorescent particles 14A are continuously dropped little by little from above the vacuum chamber 21B, they are exposed to the plasma gasified oxygen gas 26 atmosphere to oxidize the metal thin film and convert it into a transparent metal oxide thin film. And coating layer 1
4B is formed.

At this time, the volume of each coated particle covering the fluorescent particles 14A expands due to the conversion from the metal thin film to the metal oxide thin film by the oxidation treatment, so that the particles are further bonded to each other, Gaps are reduced,
A dense covering layer 14B is formed.

When the metal thin film formed on the fluorescent particles 14A is thick, the valve 24D is opened, the valve 24E is closed, and the transfer pipe 25 is closed in order to complete the oxidation.
The fluorescent particles 14A are transferred upward by C and dropped again into the vacuum chamber 21B, and this is repeated until the metal thin film is completely oxidized.

Finally, the EL phosphor 14 in which the coating layer 14B having the predetermined thickness is formed on the phosphor particles 14A is released from the outlet by releasing the vacuum and opening the valve 24F.

As described above, according to the present embodiment, after the fluorescent particles 14A are continuously exposed to metal vapor to form a metal thin film on the surface, they are continuously exposed to an ozone or oxygen plasma atmosphere, and Is converted into a transparent metal oxide thin film, and a coating layer 14B is formed on the surface of the fluorescent particles 14A, so that a dense coating layer can be formed with a large number of bonds between the particles, so that the EL phosphor is less reduced in luminance. And an El element using the same.

(Embodiment 2) Using Embodiment 2,
The invention of the present invention will be described below.

The same components as those in the first embodiment are denoted by the same reference numerals, and detailed description is omitted.

FIG. 3 shows E according to a second embodiment of the present invention.
FIG. 14 is a partial cross-sectional view of the L phosphor, in which 14A is a phosphor particle obtained by doping zinc sulfide into copper or the like as in Embodiment 1, and a surface of the phosphor particle 14A has a plurality of layers. The coating layers 14B and 14C are alternately formed.

Next, a specific method of manufacturing an EL device using such an EL phosphor 14 and its characteristics will be described.

First, indium tin oxide was sputtered to a thickness of 30 nm on a substrate 1 of a polyethylene terephthalate film having a thickness of 125 μm to form a light-transmitting electrode layer 2, and then the following printing was performed by successively overlapping. .

On the light-transmitting electrode layer 2, 100% by weight of fluoro rubber (Viton A manufactured by DuPont) as a synthetic resin 13 dissolved in 2 ethoxyethoxyethanol was added.
After stirring and mixing 00 g of the phosphor 14, it was printed on a 200 mesh stainless screen having a predetermined pattern,
It dried at 30 degreeC for 30 minutes, and the light emitting body layer 15 was formed.

The phosphor 14 is formed by using a method similar to that of the first embodiment, using aluminum as a metal thin film for the fluorescent particles 14A (SP-500 manufactured by Toshiba Corporation) and forming a coating layer of aluminum oxide. No. 14B having a film thickness of 20 to 520 nm, and No. 14B shown in (Table 1). Four types of 3-6 were produced.

In the same manner, one thickness is set to 50 nm.
No. 3, in which silica having a refractive index of 1.46 was used three times and titanium oxide having a refractive index of 2.2 was used twice, and a silica coating layer 14B was formed on the outermost peripheral side with a total thickness of 250 nm. 7, and silica three times, antimony pentoxide as a solid acid three times,
No. 3 in which a coating layer 14B of antimony pentoxide was formed on the outermost peripheral side with a total thickness of 300 nm. 8 was also made.

Further, for comparison, N
o. No. 1 in which aluminum oxide was deposited to form a coating layer. Phosphor 2 (CJ43 manufactured by OSRAM Sylvania)
0) was also produced.

Next, on each of the light emitting layers 15, 22% by weight of fluoro rubber (Viton A manufactured by DuPont) dissolved in 2 ethoxyethoxyethanol was mixed with barium titanate powder (BT-05 manufactured by Sakai Chemical Co., Ltd.). The dielectric paste in which 78% by weight was dispersed was printed on a 100-mesh stainless screen having a predetermined pattern, and dried under the same conditions as the light-emitting layer 15 to form the dielectric layer 6.

Subsequently, a carbon paste (DW-250H manufactured by Toyobo Co., Ltd.) was printed on a 200-mesh stainless screen having a predetermined pattern, and dried at 155 ° C. for 30 minutes to form a back electrode layer 7.

Finally, an insulating resist (XB-804 manufactured by Fujikura Kasei Co., Ltd.) was printed on a 200-mesh stainless screen having a predetermined pattern and dried at 155 ° C. for 30 minutes to form an insulating layer 8.

[0047]

[Table 1]

No. manufactured as described above. EL of 1-8
For the device, as shown in (Table 1), 100V400
The initial luminance at 10 Hz (Cd / m ² ) was measured after standing for one day after fabrication,
After continuous lighting at 0 V and 400 Hz for 1000 hours, the luminance was measured 30 minutes after being taken out of the bath, and a luminance retention ratio indicating a change in luminance in high humidity was compared and evaluated.

As a result, as apparent from (Table 1),
No. with no coating layer No. 1 or No. 1 in which an already oxidized metal oxide was deposited. No. 2 which was oxidized after forming the metal thin film, as compared with No. 2. In Nos. 3 to 6, the luminance retention rate increases as the thickness of the coating layer increases, that is, the change in luminance under high humidity decreases.

In the case of No. 1 in which coating layers having different refractive indexes were alternately formed. Sample No. 7 had an initial luminance almost equal to that without the coating layer, and good transmittance was obtained.

Further, No. 1 in which one layer of the coating layer was formed of a solid acid. In No. 8, in addition to the luminance retention rate of the initial luminance, ions were eluted from the fluorescent particles in high humidity, and the occurrence of so-called black spots, in which the synthetic resin was carbonized due to impaired insulation, could be prevented.

As described above, according to the present embodiment, by forming a plurality of coating layers, the coating layer becomes more dense and an EL phosphor with less luminance deterioration can be obtained.

By alternately forming the coating layers having different refractive indexes, light generated by the fluorescent particles is hardly reflected on the coating layer, and an EL phosphor having good transmittance can be obtained.

Furthermore, by forming at least one of the plurality of coating layers with a solid acid such as antimony pentoxide or zirconium oxide, the insulating properties of the luminous layer in high humidity are maintained, and black spots are hardly generated. An EL phosphor can be obtained.

The surface of the fluorescent particles 14A is covered with a coating layer 14B.
Temperature when forming C and 14C is 350 ° C. or less,
By forming the coating layer at this temperature, preferably at 0 to 200 ° C., it is possible to prevent a decrease in the brightness of the fluorescent particles 14 </ b> A due to thermal degradation during the formation of the coating layer.

In the above description, a method of continuously dropping the fluorescent particles 14A in the vacuum chamber 21A and forming a metal thin film on the surface by vapor deposition has been described. However, the fluorescent particles 14A are stirred by a stirrer or the like. The present invention can be practiced by performing vapor deposition or oxidation while forming, or forming a metal thin film by sputtering or plating instead of vapor deposition.

[0057]

As described above, according to the present invention, it is possible to form a dense coating layer, and it is possible to obtain an EL phosphor having little luminance deterioration and an EL element using the same. can get.

[Brief description of the drawings]

FIG. 1 is a sectional view of an EL device according to a first embodiment of the present invention.

FIG. 2 is a process diagram of the manufacturing method.

FIG. 3 is a partial cross-sectional view of an EL phosphor according to a second embodiment of the present invention.

FIG. 4 is a cross-sectional view of a conventional EL element.

[Explanation of symbols]

 Reference Signs List 1 base material 2 light-transmitting electrode layer 6 dielectric layer 7 back electrode layer 8 insulating layer 13 synthetic resin 14 EL phosphor 14A fluorescent particle 14B, 14C coating layer 15 light emitting layer 21A, 21B vacuum chamber 22 metal vapor 23 inert Gas 24A, 24B, 24C, 24D Valve 25A, 25B, 25C Transfer pipe 26 Oxygen gas 27 Plasma device

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) H05B 33/20 H05B 33/20 F term (reference) 3K007 AB11 AB13 AB18 CA06 CB01 DA04 DA05 DB02 DC01 EA02 EA03 EA04 EB04 FA01 4H001 CA01 CC02 CC04 CC05 CC06 XA16 XA30 YA29 4K029 AA22 BA03 BA17 BA35 BB02 BC07 BD00 CA01 EA08 GA02

Claims (6)

[Claims] 1. A method comprising the steps of: (a) forming a thin metal film on a surface by continuously exposing the fluorescent particles to a metal vapor; Alternatively, an EL phosphor formed by exposing the metal thin film to a transparent metal oxide thin film by exposing to an oxygen plasma atmosphere. 2. The EL phosphor according to claim 1, wherein a plurality of coating layers are formed. 3. The EL phosphor according to claim 2, wherein coating layers having different refractive indexes are alternately formed. 4. The EL phosphor according to claim 2, wherein at least one of the coating layers is formed of a solid acid. 5. The EL phosphor according to claim 1, wherein the coating layer is formed at an ambient temperature of 350 ° C. or lower. 6. A light transmitting electrode layer on a light transmitting substrate,
An EL element formed by laminating a light-emitting layer in which the EL phosphor according to claim 1 is dispersed in a synthetic resin and a back electrode layer.