Process for production of fluorescent substance

• US 8,877,095 B2
• Filed: 11/07/2013
• Issued: 11/04/2014
• Est. Priority Date: 08/31/2010
• Status: Active Grant

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Matsuda, Naotoshi, Fukuda, Yumi, Kato, Masahiro
• Primary Examiner(s): Koslow, Carol M
• Assistant Examiner(s): EDMONDSON, LYNNE RENEE
• Application Number:
  US14/074,049
• Publication Number:
  US 20140054500A1
• Time in Patent Office: 362 Days
• Field of Search: 252/3.014 F, 252/301.4 R, 252/301.4 F
• US Class Current: 252/301.4F
• CPC Class Codes: C01B 21/0821 Oxynitrides of metals, boron or silicon
• CPC Class Codes: C01B 21/0826 Silicon aluminium oxynitrides, i.e. sialons
• CPC Class Codes: C01P 2002/52 containing elements as dopants
• CPC Class Codes: C01P 2002/72 by d-values or two theta-values, e.g. as X-ray diagram
• CPC Class Codes: C01P 2002/84 by UV- or VIS- data
• CPC Class Codes: C09K 11/7728 containing europium
• CPC Class Codes: C09K 11/77348 Silicon Aluminium Nitrides or Silicon Aluminium Oxynitrides

Abstract

The embodiment provides a process for production of an oxynitride fluorescent substance. In the process, a compound represented by the formula: (Sr,Eu)₂Si₅N₈, silicon nitride and aluminum nitride are mixed and then fired in a nitrogen atmosphere under high pressure.

Claims

1. A process for production of a green light-emitting oxynitride fluorescent substance, comprising:

a first step in which at least a compound containing oxygen and strontium, europium oxide, and silicon powder or silicon nitride are mixed and placed in a firing container made of non-oxide material, and then fired in an atmosphere containing hydrogen and nitrogen to produce an intermediate product comprising strontium, europium, silicon and nitrogen; and

a second step in which said intermediate product obtained in the first step, silicon nitride, silicon powder or a combination thereof and aluminum nitride are mixed and then fired in a nitrogen atmosphere under high pressure,

wherein said oxynitride fluorescent substance has essentially the same crystal structure as Sr₃Al₃Si₁₃O₂N₂₁.

2. The process according to claim 1, wherein said compound containing oxygen and strontium is strontium oxide or strontium hydroxide.

3. The process according to claim 1, wherein said intermediate product contains a component represented by the formula:

(Sr,Eu)₂Si₅N₈.

4. The process according to claim 1, wherein said oxynitride fluorescent substance is a divalent europium-activated phosphor represented by the following formula:

(Sr_1-xEu_x)_aAlSi_bO_cN_d

in which x, a, b, c and d are numbers satisfying the conditions of 0<

x<

1, 0.93<

a<

1.3, 4.0<

b<

5.8, 0.6<

c<

1.0 and 6<

d<

11, respectively.

5. The process according to claim 1, wherein said intermediate product contains strontium, europium and oxygen in such amounts that the ratio by mole of oxygen to the sum of strontium and europium is less than 1.0.

6. The process according to claim 1, wherein said oxynitride fluorescent substance is a divalent europium-activated phosphor.

7. The process according to claim 1, wherein a firing temperature in the second step is 1700°

C. or more.

8. The process according to claim 1, wherein a firing temperature in the first step is in the range of 1300 to 1600°

C.

9. The process according to claim 1, wherein the silicon nitride, silicon powder or a combination thereof contains silicon powder.

10. The process according to claim 9, wherein said silicon powder has a mean particle size ranging from not less than 5 μ

m to less than 150 μ

m.

11. The process according to claim 1, wherein the intermediate product;

silicon nitride, silicon powder or a combination thereof; and

aluminum nitride are pre-fired in an atmosphere containing hydrogen and nitrogen before the firing in the second step.

12. The process according to claim 11, wherein a pre-firing temperature is in the range of 1400 to 1650°

C.