JPH07157759A - Production of zinc sulfide fluorescent substance - Google Patents

Abstract

PURPOSE:To obtain the fluorescent substance, suitable for electroluminescence, having a high brightness and luminous efficiency and excellent in electric power saving properties by baking a raw material compound according to a specific method. CONSTITUTION:This method for producing a zinc sulfide fluorescent substance is to divide a baking step into the former and latter stages, reduce the gas flow rate of H2S in the latter stage from that in the former stage, preferably mix the zinc sulfide with 0.3-0.5mol% copper compound and 5-15mol% halogen compound or At compound, then bake the raw material mixture while passing H2S therethrough at 0.005-0.5mol/min gas flow rate based on 1mol zinc sulfide, subsequently carry out the baking while passing the H2S at a gas flow rate of (1/20) to (1/5) based on that in the former stage in baking the raw material mixture at 900-1200 deg.C while passing the H2S gas therethrough and producing the zinc sulfide fluorescent substance composed of a matrix of the zinc sulfide and copper which is an activator and a halogen or Al that is a coactivator. Furthermore, the baking time is preferably 2-4hr as a whole and the baking time in the former stage is preferably regulated to 7-20% based on the whole baking time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a zinc sulfide phosphor, particularly a zinc sulfide phosphor suitable for electroluminescence (EL).

[0002]

2. Description of the Related Art Conventionally, as a phosphor for EL, ZnS: Cu containing zinc sulfide (ZnS) as a base material, copper (Cu) as an activator, and halogen or aluminum (Al) as a co-activator. , Br, ZnS: Cu, Cl, Zn
A zinc sulfide-based phosphor such as S: Cu or Al has been known as a practical phosphor.

This type of EL phosphor comprises a zinc sulfide matrix raw material such as zinc sulfide raw powder, an activator raw material containing Cu, and B
It has been manufactured by mixing co-activator raw materials containing r, Cl, Al, etc. and firing them in a hydrogen sulfide atmosphere. These phosphors are dispersed in a binder having a high dielectric constant such as cyanoethyl cellulose or cyanoethyl saccharose to form a light emitting layer, electrodes are arranged on both sides of the light emitting layer, and at least one of the electrodes is composed of a transparent electrode.
Make an L panel. Such an EL panel is used for a backlight of a liquid crystal display or the like by taking advantage of its thinness and flexibility.

[0004]

However, since the liquid crystal has a low light transmittance, the backlight of the liquid crystal display is required to have the first high brightness, and the OA equipment is driven by the battery. However, conventional EL phosphors have not satisfied these conditions. Therefore, the present invention aims to solve the above problems and provide a phosphor having high brightness, high efficiency, excellent power saving, and suitable for an EL panel.

[0005]

The present invention is a co-activator, and copper, which is an activator for a matrix of zinc sulfide, which is calcined at 900 to 1200 ° C. while aerating hydrogen sulfide into the raw material mixture. In the method for producing a zinc sulfide phosphor for EL containing halogen or aluminum, the amount of aeration of hydrogen sulfide in the latter stage of the firing step is lower than the amount of aeration of hydrogen sulfide in the former stage, and the EL is fired. It is a manufacturing method of a zinc sulfide phosphor for use. The amount of hydrogen sulfide aerated in the latter stage of the firing step can be adjusted by aeration of a mixed gas of hydrogen sulfide and an inert gas or by stopping the aeration of hydrogen sulfide.

[0006]

The present inventor has made earnest studies on the production conditions of the zinc sulfide-based phosphor that has been put into practical use as an EL phosphor, and the hydrogen sulfide aeration amount in the latter stage of the firing step was changed to that of hydrogen sulfide in the former stage. It was found that a ZnS phosphor with high brightness and high efficiency can be obtained by firing with a reduced air flow rate.

That is, the phosphor for EL of the present invention is prepared by mixing a matrix of zinc sulfide with copper as an activator and halogen or aluminum as a co-activator to prepare a phosphor raw material and then aerating hydrogen sulfide. While firing at 900 to 1200 ° C., the amount of hydrogen sulfide aerated in the latter stage of the firing step should be lower than the amount of hydrogen sulfide aerated in the former stage or the firing should be stopped in the latter stage. By suppressing the generation of sulfur defects in the presence of a relatively high concentration of hydrogen sulfide in the first stage of the firing step, and by suppressing the hydrogen sulfide concentration in the second stage to be low, the activator or co-activator in the matrix It is considered that a zinc sulfide phosphor having high luminance, high efficiency, and excellent power saving was manufactured by effectively introducing the above.

In order to specifically manufacture the zinc sulfide phosphor for EL of the present invention, 0.1 to 1.0 mol% of an activator raw material is added to zinc sulfide which is a phosphor base raw material, preferably 0.1%.
Copper compound in the range of 3 to 0.5 mol% and 1 to 20 mol%, preferably 5 to 15 mol% of the co-activator raw material.
Add a halogen or aluminum compound within the range and mix thoroughly. Then, by preliminarily ventilating hydrogen sulfide into a heat-resistant container filled with this mixture, the air in the container is replaced with hydrogen sulfide and then charged into a furnace maintained at a predetermined temperature, and a constant flow rate of hydrogen sulfide gas is supplied. While ventilating
1200 ° C, preferably 1 in the range of 950 to 1100 ° C
Firing is performed for about 5 hours, preferably for 2 to 4 hours.

In the present invention, the calcination step is divided into a front stage and a rear stage, and in the front stage, the amount of hydrogen sulfide gas aerated is 0.001 to 1 mol / min, preferably 0.005 to 0. Adjust to a range of 5 mol%. Further, the firing time in the first stage is somewhat different depending on the flow rate of hydrogen sulfide gas, but is about 5 to 50% of the total firing time, especially 7 to
It is preferable to adjust it within the range of 20% from the viewpoint of the emission brightness and emission efficiency of the phosphor.

In the latter-stage calcination, is it necessary to reduce the flow rate of hydrogen sulfide or to ventilate a mixed gas in which a part of hydrogen sulfide is replaced with an inert gas such as nitrogen or argon while keeping the total amount of gas to be ventilated constant? , Stop ventilation of hydrogen sulfide,
Firing can be performed while passing an inert gas such as argon instead of hydrogen sulfide. Aeration amount of hydrogen sulfide in the latter stage is 1/50 to 1/2 of that in the former stage, preferably 1/2
The range of 0 to 1/5 is preferable.

[0011]

【Example】

(Example 1) 0.5 mol of copper acetate [(CH ₃ COO) ₂ Cu · 2H ₂ O] as a raw material for activator was added to zinc sulfide.
%, Ammonium bromide 10.0m as a raw material for co-activator
ol%, slurried with deionized water and mixed,
It was dried at 120 ° C. for 16 hours. Then this mixture 1k
100 g of hydrogen sulfide was placed in a quartz Tamman furnace to aerate the atmosphere in the furnace at a flow rate of 2 liters / minute to replace the air in the furnace, and then 1000 ° C with the hydrogen sulfide aeration conditions maintained.
The temperature was raised to and firing was started. At 10 minutes after the start of the calcination, the aeration of hydrogen sulfide was stopped, nitrogen with a concentration of 100% was introduced at a flow rate of 0.1 liter / min, and the sulfide was gradually replaced with nitrogen, and calcination was performed at 1000 ° C. The firing was terminated when 2 hours passed after the start of the firing. afterwards,
The fired product was taken out of the furnace, copper that did not form a solid solution in zinc sulfide was separated by etching with a 10 wt% potassium cyanide aqueous solution, washed with water, dried, and sieved to obtain an average particle size of 25.6 μm.
A ZnS: Cu, Br phosphor of m was obtained.

The above phosphor was dispersed in cyanoethyl cellulose, and a thick film was printed on an aluminum electrode as a light emitting layer, and a transparent electrode was formed thereon to fabricate a dispersion type EL device. Electric power of 8.0 mW / cm ² was applied to this device at an alternating current of 1 kHz, and the emission luminance was measured by a luminance meter to obtain the emission efficiency.

Example 2 A mixture 1 of zinc sulfide, copper acetate and ammonium bromide prepared in the same proportions as in Example 1.
100 kg of hydrogen sulfide was introduced into a quartz tanman furnace at a flow rate of 1 liter / min to replace the air in the furnace, and then 1000 with the hydrogen sulfide aeration conditions maintained.
The temperature was raised to ℃ and the firing was started. Aeration of hydrogen sulfide was stopped 10 minutes after the start of firing, and then the firing was continued without venting anything, and the firing was completed 2 hours after the start of the firing. After firing, the fired product was taken out of the furnace while bubbling argon gas at a flow rate of 0.1 liter / min, and treated in the same manner as in Example 1 to obtain ZnS: Cu, Br fluorescence having an average particle size of 24.2 μm. After obtaining the body, a dispersion type EL device was produced in the same manner as in Example 1, and the emission luminance and the emission efficiency thereof were determined.

Example 3 Mixture 1 of zinc sulfide, copper acetate and ammonium bromide prepared in the same proportions as in Example 1.
100 kg of hydrogen sulfide was put into a quartz tanman furnace and aerated with hydrogen sulfide at a flow rate of 0.2 liter / min to replace the air inside the furnace.
The temperature was raised to 00 ° C to start firing. After 10 minutes from the start of firing, the flow rate of hydrogen sulfide was reduced to 20% of that at the start of firing and the firing was continued, and the firing was finished at 2 hours after the start of firing. After firing, the same treatment as in Example 1 was performed to obtain a ZnS: Cu, Br phosphor having an average particle size of 23.9 μm, and a dispersion type EL device was prepared in the same manner as in Example 1.
The luminous brightness and luminous efficiency were determined.

Comparative Example 1 A mixture 1 of zinc sulfide, copper acetate and ammonium bromide prepared in the same proportions as in Example 1.
100 kg of hydrogen sulphide was put into a quartz tanman furnace made of quartz at a flow rate of 1 liter / min to replace the air in the furnace, and then 1000 ° C with the aeration conditions of hydrogen sulphide being kept constant. The temperature was raised to 2 ° C. and baked for 2 hours. After firing, the same treatment as in Example 1 was performed to obtain Z having an average particle size of 21.0 μm.
The nS: Cu, Br phosphor was obtained, a dispersion type EL device was produced in the same manner as in Example 1, and the emission luminance and emission efficiency thereof were determined.

(Comparative Example 2) In Comparative Example 1, nitrogen having a concentration of 100% was supplied instead of hydrogen sulfide, and other conditions were the same as in Comparative Example 1, and Zn having an average particle size of 23.2 μm was used.
After obtaining the S: Cu, Br phosphor, a dispersion-type EL device was prepared in the same manner as in Example 1, and the emission luminance and emission efficiency thereof were determined.

[0017]

[Table 1]

[Evaluation] As is clear from Table 1 which summarizes the results of Examples and Comparative Examples, the phosphor of Comparative Example 2 fired in a nitrogen atmosphere hardly emits EL light and has extremely high emission brightness and emission efficiency. It showed a low value. In addition, Example 1
It can be seen that the phosphors of Nos. 3 to 3 are superior in emission brightness and luminous efficiency by 10 to 20% as compared with Comparative Example 1. Thus, by gradually introducing an inert gas such as nitrogen or argon into hydrogen sulfide from the middle of firing, completely stopping the aeration of hydrogen sulfide, or reducing the aeration amount of hydrogen sulfide, As compared with firing under a constant hydrogen sulfide concentration, it is possible to manufacture a phosphor having excellent emission brightness and emission efficiency.

Further, in the ZnS: Cu, Br phosphor, Cl, I, Al was used instead of the coactivator Br to obtain E.
When a Cu-activated ZnS phosphor for L was manufactured, ZnS:
Similar to the Cu and Br phosphors, they showed high brightness and high luminous efficiency.

[0020]

EFFECTS OF THE INVENTION The present invention can provide an EL phosphor having high brightness and high luminous efficiency by adopting the above-mentioned constitution, and can realize an EL element excellent in power saving. did.

Claims (3)

[Claims] 1. Aeration of hydrogen sulfide into the raw material mixture,
In the method for producing a zinc sulfide phosphor containing copper, which is an activator, in a matrix of zinc sulfide, which is fired at 900 to 1200 ° C., and halogen or aluminum, which is a co-activator, hydrogen sulfide in the latter stage of the firing step. The method for producing a zinc sulfide phosphor, wherein the firing rate is lower than that of hydrogen sulfide in the preceding stage. 2. The method for producing a zinc sulfide phosphor according to claim 1, wherein a mixed gas of hydrogen sulfide and an inert gas is passed in the latter stage of the firing step. 3. The method for producing a zinc sulfide phosphor according to claim 1, wherein, in the latter stage of the firing step, the hydrogen sulfide aeration is stopped and the firing is performed.