JPH0762341A - Fluorescencer and its production - Google Patents

Abstract

PURPOSE:To improve the luminance of an EL panel having a luminous layer containing a dispersed fluorescencer. CONSTITUTION:A fluorescencer is produced by a process comprising a primary firing step wherein a mixture comprising zinc sulfide, a copper compound and a halogen compound is fired at a temperature as high as 1020-1200 deg.C to form a powdery intermediate comprising hexagonal crystals and a secondary firing step wherein the intermediate is fired at a temperature as low as 500-800 deg.C to allow part of the intermediate to effect transition to cubic crystals and the segregation of copper to thereby form a conductive layer and to form a mixture of hexagonal crystals and cubic crystals in a ratio of 0.1-0.5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phosphor and a method for manufacturing the same, and more particularly to a phosphor used for a light emitting layer of a dispersion type electroluminescent device and a method for manufacturing the phosphor by two-step firing.

[0002]

2. Description of the Related Art As shown in FIGS. 3 and 4, an organic dispersion type electroluminescent lamp 1 [hereinafter referred to as an EL panel] used as a backlight of a liquid crystal display panel has a back electrode 2, a reflective insulating layer 3 and the like. , A moisture absorption film 7 made of polyamide resin or the like is disposed above and below the electroluminescence device 6 formed by sequentially stacking the light emitting layer 4 and the transparent electrode 5, and the entire electroluminescence device 6 including the moisture absorption film 7 is made of a fluorine-based material. It is formed by hermetically sealing with an outer cover film 8 made of resin or the like, and leading the leads 9 and 10 from the back electrode 2 and the transparent electrode 5 through a sealing portion of the outer cover film 8.

The light emitting layer 4 is formed by dispersing a phosphor 12 such as zinc sulfide activated by copper in an organic binder 11 as shown in FIG. 5, and is adhered to the reflective insulating layer 3 by the organic binder 11. ing. In this EL panel 1, by applying a high voltage from the leads 9 and 10 between the back electrode 2 and the transparent electrode 5, the phosphor 12 of the light emitting layer 4 sandwiched between the electrodes 2 and 5 is caused to emit light, and the desired result is obtained. It is driven with the emission brightness of.

The phosphor 12 is obtained by firing a mixture containing zinc sulfide as a base material and copper as an activator and a co-activator such as a halogen compound.

As a method for producing the phosphor 12, an appropriate amount of copper sulfate [activator] is added to fine powder of zinc sulfide [matrix] which is a light emitting base material, and after drying treatment, MgCl ₂ or NaCl is added. Etc. [co-activator] is added in an appropriate amount,
Zinc sulfide crystals are grown by performing first-stage high temperature firing [hereinafter referred to as primary firing] at a temperature of about 00 ° C. for about 3 to 5 hours. Then, the intermediate product obtained by the primary firing is subjected to a second low temperature firing [hereinafter, referred to as secondary firing] at a temperature of about 600 to 800 ° C. for about 3 hours to finally give There is obtained a phosphor 12 in which particles of zinc sulfide are doped with copper [JP-A-61-2].
96085, JP-A-1-204991].

[0006]

By the way, the phosphor 12 used in the light emitting layer 4 emits light by applying an electric field between the back electrode 2 and the transparent electrode 5 which sandwich the light emitting layer 4 as described above. Therefore, in order to make the phosphor 12 easily emit light by this electric field, it is necessary to form a local conductive layer in order to locally form a high electric field region in the particle.

In order to increase the brightness of the light-emitting layer 4, the applicant of the present invention causes zinc sulfide having a hexagonal crystal structure to undergo a crystal transition to a cubic crystal by firing, and copper is segregated in the particles of the zinc sulfide to conduct electricity. A method of manufacturing the phosphor 12 in which a layer is formed has been previously proposed [JP-A-4-236293].

However, in recent years, there has been a demand for further higher brightness of the light emitting layer, and at present, the light emission brightness of the previously proposed phosphor is insufficient. Therefore, an object of the present invention is to provide a phosphor capable of achieving higher brightness and a method for manufacturing the same, in order to meet the above-mentioned demand.

[0009]

Means for Solving the Problems As a technical means for achieving the above object, the present invention provides a hexagonal crystal having a mixture obtained by adding a copper compound and a halogen compound to zinc sulfide at a high temperature. A primary calcination step of obtaining a powdery intermediate product consisting of, and a part of the crystal structure of the intermediate product,
By firing at a low temperature, a crystal transition to a cubic crystal form is made to segregate copper to form a conductive layer, and a hexagonal crystal and a cubic crystal have a hexagonal crystal ratio of 0.1 to 0.1. It is characterized by including a secondary firing step of mixing so as to be 0.5.

The firing temperature in the primary firing step is set to 1024 to 1200 ° C., and the firing temperature in the secondary firing step is set to 600 to 800 ° C.

The phosphor according to the present invention has a crystal structure in which hexagonal crystals and cubic crystals are mixed, and the ratio of hexagonal crystals is 0.1 to 0.5. It is characterized in that it is composed.

[0012]

In the present invention, an intermediate product having a hexagonal crystal structure is formed by the primary firing, and a part of the crystal structure of the intermediate product is crystallized to the cubic type by the secondary firing to segregate copper. And a conductive layer is formed, and the ratio of hexagonal crystal is set to 0.1.
By setting it to 0.5, it is possible to realize a phosphor that forms a high-luminance light emitting layer.

[0013]

EXAMPLE An example of the phosphor according to the present invention and a method for manufacturing the same will be described with reference to FIGS. 1 (a), 1 (b) and 2.

In the method of the present invention, first, zinc sulfide [matrix]
To this, 0.08 to 0.2 mol% of a copper compound copper sulfate [activator] and 10 to 20 mol% of a halogen compound of MgCl ₂ [co-activator] were added. The mixture is primarily fired in a crucible made of alumina or the like.

This primary firing is carried out at a high temperature of about 1020 to 1200 ° C. for 3 to 5 hours, whereby crystals of zinc sulfide are grown to have a grain size of 10 to 40 μm and a crystal structure of almost 100% hexagonal type. To obtain the intermediate product.

Next, this intermediate product is secondarily fired.
The secondary firing is 2 to 5 at a low temperature of about 600 to 800 ° C.
This is carried out for a time, whereby a part of the crystal structure of the intermediate product is crystallized from the above-mentioned hexagonal type to cubic type.
By this crystal transition from the hexagonal type to the cubic type, copper is segregated at the boundary portion between the hexagonal type crystal and the cubic type crystal to form a conductive layer. As a result, the phosphor 12 having a composition in which hexagonal crystal and cubic crystal are mixed is obtained.

In the crystal structure of the phosphor 12 in which the conductive layer is formed by the crystal transition from the hexagonal type to the cubic type, the ratio of the hexagonal type crystal to the cubic type crystal is the same as that in the primary firing and the secondary firing. It can be controlled by the conditions of the subsequent firing, and the present inventor examined the ratio of the hexagonal type crystals to the cubic type crystals based on the temperature conditions of the primary firing and the secondary firing. As a result, FIGS. 1A and 1B show the measurement results of the hexagonal crystal ratio H of the phosphor with respect to the primary and secondary firing temperatures in%. The hexagonal crystal ratio H is calculated from the X-ray intensity of the phosphor 12 obtained by X-ray diffraction using the following formula.

Ihex (10.0) / Ihex (00.2) + cub (111) =
1.78H / (4-3H)

I: X-ray intensity, H: Hexagonal ratio

The measurement conditions are as follows: target: Cu Kα
line

Tube voltage: 40 kV

Tube current: 40 mA

First, FIG. 3A shows the case where the primary firing temperature [indicated by a white circle in the figure] is the same at 1100 ° C. and the secondary firing temperature [indicated by a black circle in the figure] is set in several stages. The hexagonal ratio in the crystal structure of the intermediate product is 1 due to the primary firing.
It was 00% because the hexagonal crystal ratio in the crystal structure of the phosphor 12 was 70% when the secondary firing temperature was 550 ° C.
%, 40% at 600 ° C, several% at 700 ° C, 3 at 800 ° C
It became 0%. Also, in the figure (b), the primary firing temperature [white circle] is set in several stages, and the secondary firing temperature [black circle] is 700.
The case is the same at ° C. Although the hexagonal crystal ratio in the crystal structure of the intermediate product was almost 100% by the primary firing, the hexagonal crystal ratio in the crystal structure of the phosphor 12 was 50% at the primary firing temperature of 1020 ° C. by the secondary firing. 1040 ° C
Of 30% at 1100 ° C. and 30% at 1120 ° C.

Based on this result, the present inventor dispersed the above-mentioned phosphors 12 having various hexagonal crystal ratios in the organic binder 11 to form the light emitting layer 4, and used the light emitting layer 4 for EL. The luminance characteristics of panel 1 were examined. As a result, FIG. 2 shows the relationship between the relative luminance and the hexagonal-cubic crystal ratio when the EL panel 1 was driven at 150 V and 1 kHz. In the figure, it became clear that a desired high brightness could be obtained when the ratio of hexagonal crystals was 10 to 50%. The ratio of hexagonal crystals is 10% or less, 50
% Or more, the formation of the conductive layer of the phosphor becomes insufficient,
High brightness cannot be obtained.

[0025]

According to the present invention, an intermediate product having a hexagonal crystal structure is formed by primary firing, and a part of the crystal structure of the intermediate product is transformed into a cubic crystal by secondary firing. Then, copper is segregated to form a conductive layer, and the ratio of hexagonal crystal is set to 0.1 to 0.5, whereby a phosphor for forming a light-emitting layer with high brightness can be realized and high quality can be achieved. Products can be provided.

[Brief description of drawings]

1 is intended to illustrate an embodiment of the method of the invention,
(A) and (b) are relationship diagrams showing the measurement results of the hexagonal crystal ratio of the phosphor with respect to the primary and secondary firing temperatures.

FIG. 2 is a relational diagram showing relative luminance with respect to a hexagonal-cubic crystal ratio for EL panels using phosphors having various hexagonal crystal ratios in FIG.

FIG. 3 is a cross-sectional view showing a specific structural example of an EL panel.

FIG. 4 is a plan view of the EL panel of FIG.

5 is a partially enlarged cross-sectional view showing a light emitting layer of the EL panel of FIG.

[Explanation of symbols]

 12 Phosphor

Claims (3)

[Claims] 1. A primary firing step of obtaining a powdery intermediate product consisting of hexagonal type crystals by firing a mixture obtained by adding a copper compound and a halogen compound to zinc sulfide at a high temperature,
A part of the crystal structure of the intermediate product is baked at a low temperature to form a conductive layer by segregating copper by crystallizing the crystal transition to a cubic crystal type, and a hexagonal crystal and a cubic crystal. And a secondary firing step in which a hexagonal crystal is mixed such that the ratio of the crystals is 0.1 to 0.5. 2. The firing temperature in the primary firing step is 1
The method for producing a phosphor according to claim 1, wherein the firing temperature is set to 020 to 1200 ° C., and the firing temperature in the secondary firing step is set to 600 to 800 ° C. 3. 3. A crystal structure having a mixture of hexagonal and cubic crystals, wherein the ratio of hexagonal crystals is 0.1.
A phosphor having a composition of about 0.5.