JP2009144073A - Phosphor, inorganic electroluminescent display element, backlight, and manufacturing method for them - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a phosphor allowing direct current drive at a low voltage and manufacture with high efficiency, an inorganic EL display element, a backlight, and manufacturing methods for them. <P>SOLUTION: The phosphor contains CuS 13 (or SrS) and has ZnS particles 11 (or SrS particles) each coated with a CuS layer 12 on the surface as a luminescent material. The phosphor is constructed of ZnS, which is coated with the CuS layer on the surface and contains needle-shaped Cus inside, for example, when a firing process is carried out following a kneading process after CuS is added to the ZnS particles containing CuS. The phosphor is used as a luminescent layer of the inorganic EL display element. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a phosphor, an inorganic EL display element, a backlight, and a method for producing them.

As a method for manufacturing a phosphor, for example, Patent Document 1 discloses that at least a material selected from the group consisting of Zn, Be, Mg, Ca, Sr, and Ba is used when producing a phosphor for electroluminescence (EL). A technology that uniformly disperses a material composed of carbon that becomes a conductive layer in a phosphor by mechanically alloying a material composed of a metal powder mainly composed of one kind of metal and carbon. Is disclosed. According to this, an EL phosphor capable of suppressing the leakage phenomenon and emitting light in a short wavelength region with high intensity and continuously EL can be obtained. It is described that even a phosphor can provide an EL phosphor capable of EL emission of short-wavelength visible light or ultraviolet light by efficiently generating electrolytic concentration.
JP 2007-056123 A

As described above, in the method for manufacturing a phosphor according to Patent Document 1, a material composed of metal powder and carbon is mechanically alloyed and alloyed. Thus, when alloying is performed by mechanical alloying, the material metal must use powder, and after the alloying process, there are a variety of processes, such as a sulfurization process, a pulverization process, a heat treatment process, and an inert material addition process. It is necessary to go through complicated processes.

  Moreover, since the phosphor according to the conventional manufacturing method has low conductivity, it is difficult for a display element using the phosphor to cope with low-voltage DC driving.

  The present invention has been made in view of such various points. The object of the present invention is to provide a phosphor, an inorganic EL display element, a backlight, and those capable of being driven at a low voltage by a direct current and having good production efficiency. It is to provide a manufacturing method.

  The phosphor according to the present invention is characterized by comprising ZnS particles containing CuS and having a surface coated with a CuS layer as a light emitting material.

  The phosphor according to the present invention is characterized in that it contains CuS and has SrS particles whose surface is coated with a CuS layer as a luminescent material.

  The phosphor production method according to the present invention is characterized in that CuS is added to a CuS-containing ZnS particle, kneaded, and then fired to coat the surface of the ZnS particle with a CuS layer.

  The phosphor production method according to the present invention is characterized in that CuS is added to and kneaded with SrS particles containing CuS, and then the surface of the SrS particles is coated with a CuS layer by firing.

  As an EL phosphor, the most common ZnS: Cu, Cl phosphor has a large number of twins (stacking faults) formed inside the phosphor. Twins are generated in the growth stage of ZnS particles by phosphor firing, and are called growth twins. In the phosphor, a highly conductive CuS-based compound is present in a needle shape along the twin interface. When a voltage is applied to such a phosphor, electric field concentration occurs at both ends of the needle-like conductive compound, and the phosphor matrix, ZnS, is excited. When the excitation energy at this time moves to various levels in the phosphor, the phosphor emits light.

  According to the configuration of the phosphor according to the present invention, since the surface of the ZnS particle is further coated with the CuS layer, the number of light emitting portions is larger than that of many twins in the phosphor. For this reason, it is possible to emit light at a voltage lower than that of a conventional phosphor.

  In addition, since the conventional phosphor has low conductivity, it cannot emit light in a DC electric field. However, according to the configuration of the phosphor according to the present invention, the conductivity is improved by the coating with the CuS layer, and in the DC electric field. Light can be emitted by applying voltage.

  Furthermore, the phosphor according to the present invention can be manufactured by a simple manufacturing method without requiring various complicated processes associated with alloying processing by mechanical alloying. For this reason, manufacturing efficiency becomes favorable.

  In addition, the phosphor according to the present invention has good production efficiency and can emit light at a lower voltage than conventional phosphors based on the same principle, even if the base is SrS instead of ZnS. The light can be emitted by applying a voltage in a DC electric field.

  According to the present invention, it is possible to provide a phosphor, an inorganic EL display element, a backlight, and a method for manufacturing them, which can be driven at a low voltage and have good manufacturing efficiency.

  Hereinafter, the structure of a phosphor, an inorganic EL display element, and a backlight according to an embodiment of the present invention, and a manufacturing method thereof will be described in detail with reference to the drawings. The present invention is not limited to the following embodiment.

(Embodiment 1)
(Configuration of phosphor)
In FIG. 1, the schematic diagram of the luminescent particle 10 which comprises the fluorescent substance which concerns on embodiment of this invention is shown. In FIG. 2, the schematic diagram of the luminescent particle 20 which comprises the conventional fluorescent substance as a comparison object is shown.

  The light emitting particle 10 is made of ZnS 11 which is a base of a ZnS: Cu, Cl phosphor, and its surface is coated with a CuS layer 12. The luminescent particle 10 contains acicular CuS13 inside. Since the ZnS-CuS heterojunction is formed at both tips A of the needle-like CuS 13, light emission is concentrated at both tips A of the needle-like CuS 13 inside the luminescent particle 10. Further, since the luminescent particle 10 includes the CuS layer 12 on the surface of the ZnS 11, a ZnS—CuS heterojunction is generated in a wide range at these interfaces. For this reason, the luminescent particles 10 can emit light over a wide range even on the surface B thereof.

  On the other hand, the light emitting particles 20 constituting the conventional phosphor shown in FIG. 2 are not coated with a CuS layer on the surface, and the light emitting portions are only both ends A of the needle-like CuS 23 inside the ZnS 21. . For this reason, luminous efficiency is low compared with the luminescent particles 10 according to the embodiment of the present invention.

(Phosphor production method)
Next, a method for manufacturing a phosphor according to an embodiment of the present invention will be described. First, ZnS: Cu, Cl is prepared as a phosphor material, and CuS is added thereto.

  Next, about 100 g of the above ZnS: Cu, Cl to which CuS is added and about 20 g of CuS are weighed on a medicine-wrapping paper or the like.

  Subsequently, these are put in, for example, an alumina automatic mortar and mixed (kneading stirring) for about 300 seconds to form a kneaded product of ZnS: Cu, Cl and CuS.

  Next, the kneaded product is transferred to a crucible and covered. Here, the crucible is covered in order to suppress oxidation of the kneaded material.

  Next, the kneaded product is transferred and the crucible covered with lid is moved into the electric furnace, and the electric furnace is heated from room temperature to 400 ° C. Subsequently, after holding the electric furnace at 400 ° C. for about 60 minutes, the electric furnace is turned off and lowered to room temperature. By firing the kneaded material in this way, the surface is coated with the CuS layer 12, and the luminescent particles 10 made of ZnS11 containing acicular CuS13 therein are produced. Next, a phosphor having a desired form is produced using the luminescent particles 10.

(Embodiment 2)
Next, the phosphor according to Embodiment 2 of the present invention will be described. The phosphor according to Embodiment 2 of the present invention is composed of the luminescent particles 30 shown in FIG.

  The luminescent particles 30 are composed of SrS31, which is a matrix of SrS: Cu, Cl phosphor, and the surface is coated with a CuS layer 32. The luminescent particle 30 contains acicular CuS33 inside. Since SrS—CuS heterojunction is formed at both ends of the needle-like CuS 33, light emission is concentrated at both ends A of the needle-like CuS 33 inside the luminescent particle 30. Moreover, since the light emitting particle 30 includes the CuS layer 32 on the surface of the SrS 31, SrS—CuS heterojunction is generated in a wide range at these interfaces. For this reason, the luminescent particles 30 can emit light over a wide range even on the surface B thereof.

  Further, the phosphor manufacturing method according to Embodiment 2 of the present invention differs from the manufacturing method shown in Embodiment 1 described above only in that SrS: Cu, Cl is prepared as a phosphor material, and otherwise the same. It is comprised by the process of.

(Embodiment 3)
(Configuration of inorganic EL display element 40)
Next, the configuration of the inorganic EL display element 40 using the phosphor manufactured in the first or second embodiment will be described. FIG. 4 is a cross-sectional view of the inorganic EL display element 40 according to the embodiment of the present invention.

  The inorganic EL display element 40 includes a substrate 41, a transparent conductive film 42 formed on the substrate 41, a light emitting layer 43 (phosphor) formed on the transparent conductive film 42, and a conductor 44 formed on the light emitting layer 43. And an electrode extraction portion 45 formed on the transparent conductive film 42 and an electrode extraction portion 46 formed on the conductor 44. Moreover, in FIG. 4, the light emission display surface of the inorganic EL display element 40 is a lower side.

  The substrate 41 is formed using an insulating transparent base material such as glass or resin. As the glass substrate, for example, # 1737 material manufactured by Corning, etc. is preferable because of less thermal deformation. If the drying temperature is about 120 ° C., an inexpensive soda material may be used.

The transparent conductive film 42 is composed of tin oxide, zinc oxide, ITO (Indium Tin Oxide), which is a compound of indium oxide and tin oxide, and IZO (Indium Zinc Oxide), which is a compound of indium oxide and zinc oxide. ing. In particular, ITO and IZO are preferable as a transparent conductive film material because they are excellent in transparency to visible light and have good conductivity. Further, the sheet resistance of the transparent conductive film 42 is suitably about 0.2 mΩ / cm ² .

  The light emitting layer 43 includes the light emitting particles 10 produced in Embodiment 1 or the light emitting particles 30 produced in Embodiment 2. The light-emitting layer 43 including the light-emitting particles 10 or the light-emitting particles 30 is shaped by containing an organic binder or the like.

  The conductor 44 is made of a conductive material such as carbon, silver, or aluminum. The conductor 44 need not be transparent, but of course may be configured using the above-described transparent conductive material such as ITO or IZO. The conductor 44 preferably has a thickness of about 10 μm. This is because when the thickness is 10 μm or more, the possibility of cracking increases due to a difference in expansion coefficient from the light emitting layer 43 when drying in an oven or the like. In particular, when the substrate 41 is formed of not a glass base material but a PET (polyethylene terephthalate) base material or the like, the expansion coefficient is large and the possibility of occurrence of cracks becomes higher. Note that the conductor 44 is a back-side electrode disposed opposite to the light-emitting display surface with respect to the light-emitting layer 43, and thus does not need to be transparent.

  The electrode lead portions 45 and 46 are formed on the transparent conductive film 42 and the conductor 44, respectively, and are made of a conductive material such as carbon, silver, copper, or aluminum. The electrode extraction portions 45 and 46 may be formed by directly attaching a copper foil tape or the like on the transparent conductive film 42 and the conductor 44, respectively. Alternatively, a silver paste or the like may be directly formed on the transparent conductive film 42 and the conductor 44, respectively. Further, carbon ink or the like may be applied directly on the transparent conductive film 42 and the conductor 44 to form them. Among these, on the transparent conductive film 42, it is more preferable to form the electrode extraction part 45 by performing a silver paste from an adhesive point. Moreover, it is preferable from the point of suppression of light emission unevenness to form the electrode extraction part 46 on the conductor 44 by using a copper foil tape or the like and pasting it so as to correspond to the entire circumference of the lower light emitting layer 43.

  The inorganic EL display element 40 is a direct current drive type as shown in FIG. Here, since the DC power supply has polarity, the transparent conductive film 42 side (light emitting surface side) is connected to the plus (+) terminal, and the conductor 44 side (back side) is connected to the minus (−) terminal.

(Manufacturing method of inorganic EL display element 40)
Next, a method for manufacturing the inorganic EL display element 40 using the phosphor manufactured in the first or second embodiment will be described.

  First, a substrate 41 on which a transparent conductive film 42 (film thickness of about 200 nm) such as ITO is formed is prepared. The substrate 41 is made of a glass base material or the like.

  Next, an organic binder or the like is mixed into the luminescent particles 10 and 30 (cooled to room temperature) prepared in Embodiment 1 or 2 to prepare a luminescent particle-containing printing ink paste. At this time, it is preferable to use a cyano compound as the organic binder. Moreover, it is preferable that a mixing | blending is set as light emitting particle: organic binder = 1: 1.6 by weight ratio.

  Then, the light emitting layer 43 is produced by printing the light emitting particle containing printing ink paste on the transparent conductive film 42 using a printing machine. At this time, preferably, three-layer overprinting (total film thickness of about 45 μm) is performed using a screen mesh or the like. At this time, after each printing, the processed substrate is completely dried in the oven each time, and then the next printing is started. Drying is preferably performed at 190 ° C. for about 10 minutes each time. Here, 190 ° C. is a temperature for completely removing unnecessary organic binder components from the processing substrate.

  Next, the conductor 44 is formed on the light emitting layer 43 by performing, for example, silver paste. The conductor 44 is preferably formed to a thickness of about 10 μm.

  Subsequently, the electrode extraction part 45 is formed in the peripheral part on the transparent conductive film 42 with a silver paste.

  Subsequently, a copper foil tape or the like is directly attached onto the conductor 44 so as to correspond to the entire circumference of the lower light emitting layer 43 to form the electrode extraction portion 46. Thus, the inorganic EL display element 40 is completed.

(Embodiment 4)
(Configuration of the backlight 50)
Next, the configuration of the backlight 50 using the phosphor produced in the first or second embodiment will be described. FIG. 5 shows a cross-sectional view of a display device 51 including a backlight 50 according to an embodiment of the present invention.

  The display device 51 includes a display panel 52 that includes first and second substrates 53 and 54, and a backlight 50 that is disposed on the back side of the display panel 52 and functions as a light source of the display panel 52.

  The backlight 50 includes the phosphor manufactured in the above-described embodiment 1 or 2 as a light emitting layer, and if necessary, a lens sheet is disposed on the surface in contact with the display panel. (Illustrated).

(Manufacturing method of the backlight 50)
A phosphor is manufactured as in Embodiment 1 or 2 described above, and if necessary, a lens sheet is disposed on the surface in contact with the display panel. Next, these are sequentially laminated in a separately prepared integrated plastic case. Thus, the backlight 50 is manufactured.

(Function and effect)
The phosphor according to Embodiment 1 of the present invention is characterized in that it contains CuS13 and has ZnS particles 11 whose surface is coated with a CuS layer 12 as a light emitting material.

  According to such a configuration, not only light is emitted from both ends A of the needle-like CuS-based compound 13 in the phosphor, but the surface of the ZnS particle 11 is coated with the CuS layer 12, so Even on the surface B, many light emitting portions are generated. For this reason, it is possible to emit light at a voltage lower than that of a conventional phosphor.

  Further, according to the configuration of the phosphor according to the first embodiment, the conductivity is improved by the coating with the CuS layer 12, and light can be emitted by applying a voltage in a DC electric field.

  Furthermore, the phosphor according to the first embodiment can be manufactured by a simple manufacturing method without requiring various complicated processes associated with alloying processing by mechanical alloying. For this reason, manufacturing efficiency becomes favorable.

  The phosphor according to Embodiment 2 of the present invention is characterized in that the phosphor according to Embodiment 1 described above is characterized in that it contains CuS33 and the surface thereof is provided with SrS particles 31 coated with a CuS layer 32 as a light emitting material. Has the same effect as.

  An inorganic EL display element 40 according to Embodiment 3 of the present invention is characterized in that the phosphor according to Embodiment 1 or 2 is provided in the light emitting layer 43. For this reason, the inorganic EL display element 40 can emit light at a lower voltage than the conventional one. Moreover, it can be made to light-emit by the voltage application in a direct current electric field, and also manufacturing efficiency becomes favorable.

  A backlight 50 according to Embodiment 4 of the present invention is characterized in that the phosphor according to Embodiment 1 or 2 is provided in a light emitting layer.

  Here, inorganic EL is used as various display light sources (backlights) such as a liquid crystal display device and a signboard, and these emit light by applying a voltage mainly in an alternating electric field. For example, when it is used as a light source for a liquid crystal display unit of a mobile phone or the like, the main body is a direct current.

  On the other hand, the backlight 50 according to Embodiment 4 of the present invention includes the phosphor according to Embodiment 1 or 2 in the light emitting layer, and thus can be driven with direct current. Therefore, it is not necessary to mount an expensive inverter circuit, and the manufacturing cost is good. Further, since the space necessary for mounting the inverter circuit can be omitted, there is a merit in terms of weight and design.

  As described above, the present invention is useful for phosphors, inorganic EL display elements, backlights, and methods for producing them.

FIG. 3 is a schematic diagram of light emitting particles constituting the phosphor according to Embodiment 1. It is a schematic diagram of the luminescent particle which comprises the conventional fluorescent substance. FIG. 4 is a schematic diagram of light emitting particles that constitute a phosphor according to Embodiment 2. 6 is a cross-sectional view of an inorganic EL display element according to Embodiment 3. FIG. It is sectional drawing of the display apparatus provided with the backlight which concerns on Embodiment 4.

Explanation of symbols

10, 30 Luminescent particles
11 ZnS particles
12 CuS layer
13, 33 CuS (CuS compound)
31 SrS particles
32 CuS layer
40 Inorganic EL display elements
41 Substrate
42 Transparent conductive film
43 Light emitting layer
44 Conductor
45, 46 Electrode extraction part
50 Backlight

Claims (8)

  A phosphor comprising ZnS particles containing CuS and having a surface coated with a CuS layer as a light emitting material.   A phosphor comprising SrS particles containing CuS and having a surface coated with a CuS layer as a light emitting material.   An inorganic EL display device comprising the phosphor according to claim 1 or 2 in a light emitting layer.   A backlight comprising the phosphor according to claim 1 in a light emitting layer.   A method for producing a phosphor, in which CuS is added to a ZnS particle containing CuS, kneaded, and then fired to coat the surface of the ZnS particle with a CuS layer.   A method for producing a phosphor in which CuS is added to and kneaded with SrS particles containing CuS, and then the surface of the SrS particles is coated with a CuS layer by firing.   A method for manufacturing an inorganic EL display element, wherein a light emitting layer is formed using the phosphor according to claim 5. The manufacturing method of the backlight which forms a light emitting layer using the fluorescent substance described in Claim 5 or 6.

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