JP2007238815A - Phosphor for light emitting device and light emitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a phosphor for a light emitting device such as a LED lamp with a high luminous intensity. <P>SOLUTION: The phosphor for the light emitting device is a blue phosphor which essentially comprises a Ce- and Na-activated thiogallate phosphor substantially represented by the formula: BaGa<SB>2</SB>S<SB>4</SB>:Ce, Na and emits a blue light when excited by an ultraviolet radiation (particularly a near-ultraviolet ray at a wavelength of 370-410 nm). The light emitting device is equipped with a light emitting element that emits an ultraviolet radiation and a light emitting part containing the phosphor for the light emitting device. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a phosphor for a light emitting device and a light emitting device such as an LED lamp using the phosphor.

  In recent years, technologies corresponding to environmental protection such as lead-free have expanded worldwide, and accordingly, a light source (lamp) for illumination is also a light emitting diode that emits white light from a fluorescent lamp containing Hg ( The LED (Light Emitting Diode) lamp is shifting.

  In general lighting applications, white LED lamps with high color rendering properties are required. Further, a white LED lamp capable of expanding the color reproduction range is required as a backlight of the LCD. In order to meet these demands, a near-ultraviolet (long-wavelength ultraviolet) LED chip and a blue or green LED chip instead of a white LED lamp combining a blue LED chip and a yellow or orange-emitting yellow phosphor. In addition, a white LED lamp of a system combining a three-color mixed phosphor of red and red (hereinafter referred to as RGB phosphor) has been developed.

  However, this type of white LED lamp has a problem that its luminous efficiency is lower than an LED lamp in which a blue light emitting LED chip and a yellow phosphor are combined. In order to increase the light emission efficiency, it is necessary to improve the light emission efficiency of the LED chip. However, a phosphor having a higher light emission efficiency is required in the region of the light emission wavelength of the LED chip of 370 to 410 nm.

  Recently, the use of phosphate phosphors and aluminate phosphors has been studied as phosphors having high luminous efficiency, but sufficient brightness has not been obtained.

  In addition, it includes an LED that emits ultraviolet light, a europium activated halophosphate phosphor or a europium activated aluminate phosphor as a blue light emitting component, a europium and manganese activated aluminate phosphor as a green light emitting component, a red light emitting component For example, white LED lamps using europium and samarium activated lanthanum oxysulfide phosphors have been proposed. (For example, see Patent Document 1)

However, although the LED lamp including such a phosphor has high color rendering properties and uniformity of light emission, it is not fully satisfactory in terms of luminance.
JP 2000-73052 A

  The present invention has been made to solve such a problem, and an object of the present invention is to provide a phosphor for a light emitting device having high emission luminance. Another object of the present invention is to provide a light emitting device such as a white LED lamp with high emission brightness by using such a phosphor.

The phosphor for a light-emitting device of the present invention is mainly composed of a thiogallate phosphor substantially activated by cerium (Ce) and sodium (Na) substantially represented by the chemical formula: BaGa ₂ S ₄ : Ce, Na. It is a blue phosphor that emits blue light when excited by radiation.

  The light-emitting device of the present invention includes a light-emitting element that emits ultraviolet rays and a light-emitting portion that includes the above-described phosphor for a light-emitting device of the present invention.

  The phosphor for light-emitting device of the present invention is mainly composed of Ce and Na-activated thiogallate phosphors and has a wide absorption band over a wavelength range of 350 to 420 nm. Converts and emits bright blue light. Therefore, by using this phosphor, it is possible to realize a light emitting device such as an LED lamp with high emission luminance.

  Hereinafter, modes for carrying out the present invention will be described.

In the first embodiment of the present invention, cerium (Ce) and sodium (Na) are used as an activator and a coactivator, respectively, and barium (Ba) belonging to group II of the periodic table and gallium belonging to group III (Ga ) And sulfur (S) belonging to group VI. More specifically, it is mainly composed of cerium and sodium-activated barium thiogallate having a composition substantially represented by the chemical formula: BaGa ₂ S ₄ : Ce, Na, and is composed of ultraviolet rays (for example, near wavelengths of 370 to 410 nm). It is a blue phosphor that emits blue light when excited by the radiation of ultraviolet rays.

In the phosphor of the first embodiment, Ce is a first activator (main activator) that forms a light emission center, and has a high transition probability, so that the light emission efficiency is high. Ce, which is the main activator, is preferably contained in the range of 0.1 to 5.0 mol% with respect to barium thiogallate (BaGa ₂ S ₄ ) which is the base material of the phosphor. A more preferable Ce content is 0.5 to 2.0 mol%. If the Ce content is out of this range, the light emission luminance and light emission chromaticity are lowered, which is not preferable.

Na is called a coactivator and compensates charge of Ce activated to barium thiogallate (SrGa ₂ S ₄ ). The content ratio of Na is preferably in the range of 2 to 5 mol% with respect to barium thithiogallate which is a phosphor matrix.

  The cerium and sodium activated barium thiogallate phosphors according to the first embodiment of the present invention can be produced, for example, by the method shown below.

That is, a phosphor raw material containing an element constituting the phosphor base material and an activator (main activator and coactivator) or a compound containing the element is obtained with a desired composition (BaGa ₂ S ₄ : Ce, Na) is weighed, and sodium carbonate is added as a flux if necessary, and these are mixed in a dry process. Specifically, a predetermined amount of barium sulfide and gallium sulfide are mixed, and an appropriate amount of activator and flux are added to obtain a phosphor material. Instead of barium sulfide, an acidic barium raw material such as barium sulfate may be used. As the activator, cerium sulfide or cerium oxalate can be used, and as the coactivator, sodium carbonate, sodium chloride or the like can be used.

  Subsequently, such a phosphor raw material is filled in a heat-resistant container such as an alumina crucible together with appropriate amounts of sulfur and activated carbon. In addition and mixing of sulfur, it is preferable to mix a slightly larger amount than the phosphor raw material using a blender or the like, fill the mixed material in a heat-resistant container, and then cover the surface with sulfur. This is fired in a sulfide atmosphere such as a hydrogen sulfide atmosphere, a sulfur vapor atmosphere, or a reducing atmosphere (for example, an atmosphere of 3 to 5% hydrogen-remaining nitrogen).

Firing conditions are important in controlling the crystal structure of the phosphor matrix (BaGa ₂ S ₄ ). The firing temperature is preferably in the range of 700 to 1100 ° C. Although the firing time depends on the set firing temperature, it is preferably 60 to 180 minutes, and after firing, it is preferably cooled in the same atmosphere as firing. Thereafter, the obtained fired product is washed with ion-exchanged water and dried, followed by sieving to remove coarse particles as necessary, thereby activating cerium and sodium activated barium thiogallate (BaGa ₂ S). ₄ : Ce, Na) phosphor can be obtained.

  The cerium and sodium activated barium thiogallate phosphor according to the first embodiment can be synthesized using metal gallium and barium sulfide or barium sulfate as starting materials. Firing can be performed under the firing conditions (temperature and time) described above.

  Further, the phosphor raw material can be fired using a rotary heating furnace as shown below. That is, the above-described phosphor raw material is put into a rotating tubular heating furnace that is arranged so as to be inclined with respect to the horizontal direction, and continuously passed. Then, the phosphor material is rapidly heated to a predetermined firing temperature in the heating furnace, and the furnace is moved from the upper side to the lower side while rolling according to the rotation of the heating furnace. In this way, the phosphor material is heated and fired for a necessary and sufficient time. Thereafter, the fired product is continuously discharged from the heating furnace, and the discharged fired product is rapidly cooled.

  In such a firing step, the inside of the tubular heating furnace and the cooling part of the fired product discharged from the heating furnace are preferably maintained in an oxygen-free state from which oxygen has been removed. It is desirable to maintain in an inert gas atmosphere such as argon or nitrogen, a reducing gas atmosphere containing hydrogen, or a hydrogen sulfide atmosphere.

  According to such a firing method, since the phosphor material is rapidly heated while rolling in the process of moving in the heating furnace, uniform heat is applied to the phosphor material in an oxygen-free state and in a hydrogen sulfide atmosphere. As a result of energy being added, firing can be completed in a shorter time compared to a conventional firing method using a crucible. Therefore, a phosphor having a small particle diameter can be obtained without causing a decrease in luminance. Further, since aggregation of the phosphor particles can be suppressed, there is no need to further pulverize after firing. Therefore, phosphor deterioration due to repeated pulverization steps can be suppressed. Furthermore, since the phosphor material is heated and fired while rolling in the heating furnace, phosphor particles having a uniform particle size and a shape close to a sphere can be obtained.

  The cerium- and sodium-activated barium thiogallate phosphor of the first embodiment thus obtained is a phosphor that emits blue light when excited by radiation of long-wavelength ultraviolet light (near ultraviolet light) having a wavelength of 370 to 410 nm. Therefore, high luminance can be obtained. Therefore, by using this phosphor as the blue phosphor, a light emitting device such as an LED lamp with high emission luminance can be realized.

  Next, an LED lamp (a blue LED lamp and a white LED lamp) having a light emitting unit including the blue phosphor according to the first embodiment will be described.

FIG. 1 is a cross-sectional view schematically showing a configuration of an LED lamp according to a second embodiment. In FIG. 1, reference numeral 1 denotes a frame (lead frame) having a cup, and an ultraviolet light emitting type LED chip 2 is mounted on the cup of the frame 1. As the ultraviolet light emitting type LED, any existing one including In _x Ga _1-x N can be used, but those emitting near ultraviolet rays having an emission peak wavelength of 370 to 410 nm are preferable.

  And the back surface electrode of this LED chip 2 is electrically connected to the electrode terminal 1a of one flame | frame. Further, the upper surface electrode of the LED chip 2 is connected to the electrode terminal 1b of the other frame through the bonding wire 3. The cup in which the LED chip 2 is arranged is filled with a resin (for example, acrylic resin, epoxy resin, silicone resin, polyimide resin, etc.) containing the blue phosphor of the first embodiment, and the phosphor-containing layer 4 Further, a transparent resin sealing layer 5 such as an acrylic resin, an epoxy resin, a silicone resin, or a polyimide resin is formed on the outer side.

  To manufacture the LED lamp of such an embodiment, an acrylic resin, an epoxy resin, a silicone resin, a polyimide resin, or the like obtained by diluting a predetermined amount of a blue phosphor with an organic solvent such as acetone or toluene. The liquid mixed in the transparent resin is dropped onto the LED chip 2 using, for example, a dispenser and applied. Next, after the coating layer is dried and cured, the transparent resin sealing layer 5 is formed thereon by a method such as attaching a cap formed of a transparent resin such as an epoxy resin, thereby completing the LED lamp.

In the LED lamp of the second embodiment manufactured as described above, the applied electric energy is converted into long wavelength ultraviolet light (near ultraviolet light) having a wavelength of 370 to 410 nm by the LED chip 2, and the near ultraviolet light is converted into a phosphor. The blue phosphor of the first embodiment contained in the containing layer 4 is converted into light having a longer wavelength, and blue light is emitted. Since the blue phosphor is mainly composed of Ce and Na-activated barium thiogallate substantially represented by the chemical formula: BaGa ₂ S ₄ : Ce, Na, and has a wide absorption band over a wavelength of 350 to 420 nm, Luminous blue light is emitted.

In the LED lamp of the embodiment, the phosphor-containing layer 4 which is a light-emitting portion, together with the blue phosphor of the first embodiment, is excited by near-ultraviolet radiation and emits yellow light or orange light. By containing the white LED lamp can be obtained. Here, as the yellow to orange light-emitting phosphor, for example, a YAG phosphor such as RE ₃ (Al, Ga) ₅ O ₁₂ : Ce phosphor (RE represents at least one selected from Y, Gd, and La). Silicate phosphors such as AE ₂ SiO ₄ : Eu phosphor (AE is an alkaline earth element such as Sr, Ba, Ca, etc.). In such an LED lamp, white light is emitted by a mixture of blue light emitted from the blue phosphor and yellow light or orange light emitted from the yellow phosphor.

Further, the blue phosphor of the first embodiment, the green phosphor that emits green light when excited by near ultraviolet radiation, and the red phosphor that emits red light when excited by near ultraviolet radiation are converted into white light. The white LED lamp can be obtained by configuring the phosphor-containing layer 4 using the phosphor for BGR white LED mixed at a predetermined ratio so as to obtain the above. Here, as the green phosphor, for example, an aluminate phosphor such as a (Ba, Mg) Al ₁₀ O ₁₇ : Eu, Mn phosphor can be used. As the red phosphor, an oxysulfide phosphor such as a La ₂ O ₂ S: Eu phosphor can be used. In such an LED lamp, white light is emitted by a mixture of blue light emitted from the blue phosphor, green light emitted from the green phosphor, and red light emitted from the red phosphor.

  Hereinafter, specific examples of the present invention will be described.

Example 1 (blue LED lamp)
A raw material containing an element constituting the phosphor base material and an activator or a compound containing the element has the following composition (BaGa ₂ S ₄ : Ce content ratio: 0.6 mol%, Na content ratio: 5.0 mol% ), And excess sodium carbonate was added as a flux and mixed well. Appropriate amounts of sulfur and activated carbon were added to the obtained phosphor material, filled in a quartz crucible, and fired in a hydrogen sulfide atmosphere. The firing conditions were 850 ° C. × 60 minutes, and the obtained fired product was further fired under the conditions of 1050 ° C. × 60 minutes.

Then, the obtained fired product was washed with water, dried, and further sieved to obtain Ce and Na-activated barium thiogallate phosphor (BaGa ₂ S ₄ : Ce, Na).

  Next, using the phosphor thus obtained, a blue LED lamp shown in FIG. 1 was produced as follows. That is, an ultraviolet light emitting type LED chip having a light emission peak at a wavelength of 380 to 390 nm obtained by mixing the above-described Ce and Na-activated barium thiogallate phosphor in a mixed liquid of an epoxy resin and an acid anhydride curing agent. After dropping by using a dispenser on (0.4 mm square) to cure the epoxy resin, a hemispherical transparent epoxy resin cap was coated thereon.

As Comparative Example 1, a blue LED lamp was produced in the same manner as in Example 1 except that BaMgAl ₁₀ O ₁₇ : Eu phosphor was used as a blue light-emitting phosphor.

Next, the light emission luminance and light emission chromaticity of the blue LED lamps obtained in Example 1 and Comparative Example 1 were measured. And the light emission luminance was calculated | required as a relative value when the light emission luminance of the LED lamp of the comparative example 1 was made into 100%. Table 1 shows the measurement results of emission luminance and emission chromaticity.

  As is apparent from Table 1, the LED lamp obtained in Example 1 has a significantly improved luminance of blue light emission compared to the LED lamp obtained in Comparative Example 1, and has a sufficiently good emission color. Have a degree.

Example 2 (white LED lamp)
The Ce and Na-activated barium thiogallate phosphor (BaGa ₂ S ₄ : Ce, Na) prepared in Example 1 was used as a blue phosphor and mixed with the following green phosphor and red phosphor so as to be white. did.
BaMgAl ₁₀ O ₁₇ : Eu, Mn phosphor red phosphor; La ₂ O ₂ S: Eu phosphor

  This phosphor for BGR white LED is mixed with a mixed liquid of an epoxy resin and an acid anhydride curing agent, and the liquid is an ultraviolet light emitting LED chip having a light emission peak at a wavelength of 380 to 390 nm (0.4 mm square). The epoxy resin was dropped by using a dispenser to cure the epoxy resin, and then a hemispherical transparent epoxy resin cap was coated thereon.

As Comparative Example 2, a white LED lamp was produced in the same manner as in Example 2 except that BaMgAl ₁₀ O ₁₇ : Eu phosphor was used as the blue phosphor.

Next, the light emission luminance of the white LED lamps obtained in Example 2 and Comparative Example 2 was measured. And the light emission luminance was calculated | required as a relative value when the light emission luminance of the LED lamp of the comparative example 2 was set to 100%. The measurement results are shown in Table 2.

  As is clear from Table 2, the white LED lamp obtained in Example 2 has improved white light emission brightness as compared with the white LED lamp obtained in Comparative Example 2.

  According to the phosphor for a light emitting device of the present invention, high-intensity blue light is emitted by excitation of ultraviolet rays (for example, near ultraviolet rays having a wavelength of 370 to 410 nm). Therefore, by using this phosphor, it is possible to realize a light emitting device such as an LED lamp with high emission luminance.

It is sectional drawing which shows schematically the LED lamp which is the 2nd Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Frame, 2 ... LED chip, 3 ... Bonding wire, 4 ... Phosphor containing layer, 5 ... Transparent resin sealing layer.

Claims (5)

Chemical formula: BaGa ₂ S ₄ : Ce, Na
A thiogallate phosphor activated by cerium (Ce) and sodium (Na) substantially represented by the formula (1), which is a blue phosphor that emits blue light when excited by ultraviolet radiation. Phosphor for light emitting device.   The phosphor for a light-emitting device according to claim 1, wherein the ultraviolet light is near ultraviolet light having a wavelength of 370 to 410 nm.   A light emitting device comprising: a light emitting element that emits ultraviolet light; and a light emitting portion including the phosphor for a light emitting device according to claim 1.   The light emitting element includes a light emitting diode (LED) chip that emits near ultraviolet rays having a wavelength of 370 to 410 nm, and the light emitting portion is excited by the phosphor for a light emitting device according to claim 1 and the radiation of the near ultraviolet rays. 4. The light emitting device according to claim 3, further comprising yellow phosphors that emit yellow light or orange light, and emits white light.   The light emitting element includes a light emitting diode (LED) chip that emits near ultraviolet rays having a wavelength of 370 to 410 nm, and the light emitting portion is excited by the phosphor for a light emitting device according to claim 1 and the radiation of the near ultraviolet rays. 4. A light emitting device according to claim 3, further comprising a green phosphor that emits green light and a red phosphor that emits red light when excited by the near-ultraviolet radiation, and emits white light. .

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