JP5137395B2 - Light emitting device - Google Patents

Description

  INDUSTRIAL APPLICABILITY The present invention is suitably used for a light-emitting device that converts the wavelength of light emitted from a light-emitting element such as an LED (Light Emitting Diode) and extracts it to the outside, in particular, a backlight power source for an electronic display, a fluorescent lamp, and the like. The present invention relates to a light emitting device.

  A light emitting element made of a semiconductor material (hereinafter sometimes referred to as “LED chip”) is small in size, has high power efficiency, and vividly develops color. LED chips have excellent characteristics such as long product life, strong on / off lighting repeatability, and low power consumption, so they are expected to be applied to backlight sources such as liquid crystals and lighting sources such as fluorescent lamps. Has been.

  The application of the LED chip to the light emitting device is that the wavelength of part of the light of the LED chip is converted with a phosphor, and the wavelength-converted light and the light of the LED that is not wavelength-converted are mixed and emitted, thereby It has already been manufactured as a light emitting device that emits a color different from that of light.

Specifically, in order to emit white light, a light emitting device in which a wavelength conversion layer containing a phosphor is provided on the surface of an LED chip has been proposed. For example, in a light emitting device in which a wavelength conversion layer including a YAG phosphor represented by a composition formula of (Y, Gd) ₃ (Al, Ga) ₅ O ₁₂ is formed on a blue LED chip using an nGaN-based material, Since blue light is emitted from the LED chip and a part of the blue light is changed to yellow light in the wavelength conversion layer, a light emitting device in which blue and yellow light are mixed and white is proposed (see Patent Document 1). ).

  In this light emitting device, when light emitted from the light emitting element is irradiated onto the phosphor, the phosphor is excited to emit visible light, and this visible light is used as an output. However, when the brightness of the light emitting element is changed, the light quantity ratio between blue and yellow changes, so that there is a problem that the color tone of white changes and the color rendering property is inferior.

Therefore, in order to solve such a problem, a purple LED chip having a peak of 400 nm or less is used as the light emitting element in the structure, and the wavelength conversion layer has a structure in which three kinds of phosphors are mixed in a polymer resin. It has been proposed that violet light is converted into red, green, and blue wavelengths to emit white light (see Patent Document 2). Thereby, a color rendering property can be improved.
JP 11-261114 A JP 2002-314142 A

However, the light emitting device described in Patent Document 2 has a problem that the efficiency of white light cannot be improved because the luminous efficiency of the phosphor in the ultraviolet region near the excitation light of 400 nm is low. In particular, since the luminous efficiency of a red component phosphor (for example, Y ₂ O ₃ S: Eu) is significantly lower than that of other phosphors, it is necessary to increase the content of the red component phosphor. There was a problem that the efficiency of the system could not be improved.

  An object of the present invention is to improve the light emission efficiency of a light emitting device including a wavelength conversion layer.

  As a result of intensive studies to solve the above-mentioned problems, the present inventor has excited a plurality of phosphors contained in the wavelength conversion layer only by excitation light from the light emitting element and does not emit fluorescence, but phosphors It has been found that the luminous efficiency of the phosphor can be remarkably improved by using a combination of a plurality of phosphors so that the fluorescent light emitted from the light source is also excited and emits fluorescence. .

  That is, the light emitting device of the present invention has the following configuration.

A base plate, a light emitting element that emits excitation light that is mounted on the substrate, and a wavelength conversion layer in which the excitation light formed so as to cover the light-emitting element comprising a phosphor that converts the visible light And the phosphor is composed of (Sr, Ca, Ba, Mg) ₁₀ (PO ₄ ) ₆ Cl ₂ : Eu and (Sr, Ba) ₂ SiO ₄ : Eu. A combination of the first phosphor configured and Ba ₃ MgSi ₂ O ₈ : Eu, Mn, the first phosphor and Sr ₅ Al ₂ (O, S) ₈ : Eu and SrOSi ₂ N ₂ O combining the first phosphor and the _{Sr 5 Al 2 (O, S} ) 8: Eu and CaSiAlN _3: combination of Eu, the light-emitting device according to claim any der Rukoto of.

According to the present invention , high conversion efficiency can be achieved.

  The light emitting device of the present invention will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view showing an embodiment of a light emitting device of the present invention. According to FIG. 1, the light emitting device of the present invention is formed so as to cover the light emitting element 3 on the substrate 2, the light emitting element 3 provided on the substrate 2, the substrate 2 on which the electrode 1 is formed. One wavelength conversion layer 4 and a reflecting member 6 that reflects light are provided.

  The wavelength conversion layer 4 contains, for example, a phosphor 5a emitting fluorescence from 430 nm to 490 nm, a phosphor 5b emitting fluorescence from 520 nm to 570 nm, and a phosphor 5c emitting fluorescence from 600 nm to 650 nm in a transparent matrix. . The wavelength of the light emitted from the light emitting element 3 that is a light source is converted, and output light including the light having the converted wavelength is output.

In such a light-emitting device, the phosphor is composed of (Sr, Ca, Ba, Mg) ₁₀ (PO ₄ ) ₆ Cl ₂ : Eu and (Sr, Ba) ₂ SiO ₄ : Eu first fluorescence. Body and Ba ₃ MgSi ₂ O ₈ : Eu, Mn, the first phosphor and Sr ₅ Al ₂ (O, S) ₈ : Eu and SrOSi ₂ N ₂ O, the first fluorescence body and _{Sr 5 Al 2 (O, S} ) 8: Eu and CaSiAlN _3: combination of Eu, either der Rukoto that is significant. Hereinafter, Ba ₃ MgSi ₂ O ₈ : Eu, Mn and Sr ₅ Al ₂ (O, S) ₈ : Eu will be referred to as a second phosphor, and SrOSi ₂ N ₂ O and CaSiAlN ₃ : Eu will be referred to as a _third phosphor . Sometimes referred to as a phosphor.

  That is, it is important to combine phosphors that convert light from the light emitting element with those that convert the output light of other phosphors to different wavelengths.

  The output light of the phosphor is preferably blue, yellow, and red light from the viewpoint of improving color rendering.

  In such a combination, the red phosphor 5c has a function with the second phosphor.

  By performing the combination as described above, not only the excitation light of the light emitting element but also the visible light emitted from the phosphor is excited, so that the number of photons emitted to the outside increases, so that the efficiency can be improved. In other words, the light around 400 nm emitted from the light emitting element has low excitation efficiency and low emitted fluorescence intensity, but can also absorb a wide range of light including fluorescence of other phosphors. It is possible to compensate for the disadvantage of the conventional phosphor that the excitation efficiency at around 400 nm is low.

Blue phosphor is excited by the longitudinal 400nm light, that Hassu fluorescence 490nm from _{430nm (Sr, Ca, Ba,} Mg) 10 (PO 4) 6 Cl 2: E u is preferably used.

The yellow phosphor is excited by light having a wavelength of around 400 nm and (Sr, Ba) ₂ SiO ₄ : E u that emits fluorescence of 520 nm to 570 nm is used.

Red phosphor is excited by the longitudinal 400nm light, even the is used fluoresces 650nm from 600 nm.

  It is important to use a second phosphor that further converts the output light from the first phosphor that converts light at around 400 nm, even if the light at around 400 nm has low conversion efficiency. That's it.

Therefore, _Ba and the _{3 MgSi 2 O 8: Eu,} Mn and _{Sr 5 Al 2 (O, S} ) 8: Eu are preferred, they are the ability to convert light of 430~470nm the red light Ru excellent Tei.

  For example, a red phosphor that is a second phosphor excellent in the ability to convert light of 430 to 470 nm into red light, and red fluorescence that is excited by light of around 400 nm and emits fluorescence of 600 nm to 650 nm. In this case, a red phosphor that is excited by light of around 400 nm and emits fluorescence of 600 nm to 650 nm becomes the third phosphor.

  In this way, by converting light of different wavelengths to light of close wavelengths, for example, even in the case of most phosphors having a lower conversion efficiency than other colors, such as red, red light Can be output a lot.

  In particular, when the difference between the peak wavelength of the second output light and the third output light is within 70 nm, more light with a specific wavelength can be output.

  The average particle diameter of the phosphors 5a, 5b, and 5c is 0.1 to 50 μm, preferably 0.1 to 20 μm, and more preferably 1 to 20 μm. When the average particle diameter is larger than 50 μm, the light transmittance of the wavelength conversion layer is remarkably lowered, so that the light emitted by the phosphor is not emitted from the wavelength conversion layer, and as a result, the light emission efficiency of the light emitting device is remarkably lowered. .

  The wavelength converter 4 contains phosphors 5a, 5b, and 5c in a transparent matrix. The phosphors 5 are directly excited by the light emitted from the light emitting element 3, respectively, and generate visible light as converted light. The converted light converted by the phosphor 5 in the wavelength converter 4 is synthesized and extracted as output light.

  The thickness of the wavelength converter 4 is 0.1 to 5.0 mm, preferably 0.2 to 1 mm, from the viewpoint of conversion efficiency. If the thickness is within this range, the wavelength conversion efficiency by the phosphor 5 can be improved, and the converted light can be suppressed from being absorbed by other phosphors. As a result, the light emitted from the light emitting element 3 can be converted into visible light with high efficiency, and the converted visible light can be transmitted to the outside with high efficiency.

  The peak wavelength of the output light converted in the wavelength converter 4 is preferably 400 to 750 nm, particularly 450 to 650 nm. Thereby, the emission wavelength can be covered in a wide range, and the color rendering can be improved.

  Since the wavelength converter 4 can uniformly disperse and carry the phosphor 5 and can suppress light deterioration of the phosphor 5, it is formed by being dispersed in a transparent matrix such as a polymer resin or a glass material. Is preferred. As a glass material such as a polymer resin film or a sol-gel glass thin film, a material having high transparency and durability that is not easily discolored by heating or light is desirable.

  The material of the polymer resin film is not particularly limited. For example, epoxy resin, silicone resin, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polystyrene, polycarbonate, polyethersulfone, cellulose acetate, polyarylate, Derivatives of these materials are used. In particular, it is preferable to have excellent light transmittance in a wavelength region of 350 nm or more. In addition to such transparency, a silicone resin is more preferably used from the viewpoint of heat resistance.

  Examples of the glass material include silica, titania, zirconia, and composite materials thereof. Each of the phosphors 5 is formed in a glass material by dispersing it alone. Compared to a polymer resin film, it has a high durability against light, particularly ultraviolet light, and further has a high durability against heat, so that the product life can be extended. In addition, since the glass material can improve stability, a light-emitting device with excellent reliability can be realized.

  The wavelength converter 4 can be formed by a coating method using a glass material such as a sol-gel glass film or a polymer resin film. Although it will not be limited if it is a general coating method, the application | coating by a dispenser is preferable. For example, it can be manufactured by mixing the phosphor 5 with a liquid uncured resin, a glass material, or a resin and a glass material plasticized with a solvent. As the uncured resin, for example, a silicone resin can be used. These resins may be of a type that is cured by mixing two liquids, or a type that is cured by one liquid. The body 5 may be kneaded, or the phosphor 5 may be kneaded in one of the liquids. In addition, as a resin made plastic with a solvent, for example, an acrylic resin can be used.

  The cured wavelength converter 4 can be obtained by forming into a film shape by using a coating method such as a dispenser in an uncured state, or pouring into a predetermined mold and hardening. As a method of curing the resin and the glass material, there are a method of using heat energy and light energy, and a method of volatilizing the solvent.

  The wavelength converter and light-emitting device of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic cross-sectional view showing an embodiment of a light emitting device of the present invention. The light-emitting device of the present invention includes a light-emitting element 3 made of a compound semiconductor that emits excitation light, an electrode 1 that is electrically connected to the light-emitting element and connected to the outside, and a wavelength that converts the wavelength of the excitation light. A converter 4 is provided on the substrate 2. The wavelength converter 4 includes phosphors 5 dispersed in a transparent matrix, converts the wavelength of light emitted from the light emitting element 3 as a light source, and outputs output light including the light whose wavelength has been converted. . In addition, the light-emitting device of FIG.

  The electrode 1 has a function as a conductive path for electrically connecting the light emitting element 3 and is connected to the light emitting element 3 with a conductive bonding material. As the electrode 1, for example, a metallized layer containing metal powder such as W, Mo, Cu, or Ag can be used. When the substrate 2 is made of ceramics, the electrode 1 is formed by firing a metal paste made of tungsten (W), molybdenum (Mo) -manganese (Mn), or the like on the upper surface of the substrate 2 at a high temperature. , Lead terminals made of copper (Cu), iron (Fe) -nickel (Ni) alloy or the like are molded and fixed inside the substrate 2.

  Since the substrate 2 is required to have excellent thermal conductivity and high total reflectance, for example, a polymer resin in which metal oxide fine particles are dispersed is suitably used in addition to a ceramic material such as alumina or nitrogen aluminum. It is done.

  The light-emitting element 3 uses a light-emitting element including a semiconductor material that emits light having a center wavelength of 370 to 420 nm because phosphors can be efficiently excited. Thereby, it is possible to increase the intensity of the output light and obtain a lighting device with higher emission intensity.

The light-emitting element 3 preferably emits the above-mentioned center wavelength, but having a structure (not shown) having a light-emitting layer made of a semiconductor material on the surface of the light-emitting element substrate has a high external quantum efficiency. preferable. Examples of such semiconductor materials include various semiconductors such as ZnSe and nitride semiconductors (GaN, etc.), but the type of the semiconductor material is not particularly limited as long as the emission wavelength is in the above wavelength range. A stacked structure including a light-emitting layer made of a semiconductor material may be formed over a light-emitting element substrate using a crystal growth method such as a metal organic chemical vapor deposition method (MOCVD method) or a molecular beam epitaxial growth method. In order to form a nitride semiconductor with good crystallinity with high productivity, for example, when a light emitting layer made of a nitride semiconductor is formed on the surface of the light emitting element substrate, sapphire, spinel, SiC, Si, ZnO, ZrB ₂ , GaN In addition, materials such as quartz are preferably used.

  Reflective members 6 that reflect light are provided on the side surfaces of the light emitting element 3 and the wavelength converter 4 as necessary, and the light escaping to the side surfaces can be reflected forward to increase the intensity of the output light. Examples of the material of the reflecting member 6 include aluminum (Al), nickel (Ni), silver (Ag), chromium (Cr), titanium (Ti), copper (Cu), gold (Au), iron (Fe), and these. These laminated structures and alloys, ceramics such as alumina ceramics, or resins such as epoxy resins can be used.

  The light emitting device of the present invention is obtained by installing a wavelength converter 4 on a light emitting element 3 as shown in FIG. As a method of installing the wavelength converter 4 on the light emitting element 3, it is possible to install the cured sheet-like wavelength converter 4 on the light emitting element 3, and a liquid uncured material is applied on the light emitting element 3 It is also possible to harden and install after installation.

  The phosphor shown in Table 1 was dispersed and mixed in a silicone resin having a dimethyl silicone skeleton to prepare a phosphor-containing resin paste. The phosphor-containing resin paste was prepared by adding 20 parts by weight of the phosphor to 100 parts by weight of the silicone resin.

  The obtained phosphor-containing resin paste was applied and formed on a smooth substrate with a dispenser, and this was heated on a hot plate at 80 ° C. for 5 minutes to prepare a temporarily cured film. Subsequently, this was placed in a dryer at 150 ° C. for 30 hours to produce a wavelength conversion layer.

And the wavelength conversion layer was arrange | positioned so that the light emitting element installed on the board | substrate might be covered, the light-emitting device was produced, and it supplied with electricity to the light emitting element, and measured luminous efficiency. The results are shown in Table 1. Note that the peak of the excitation wavelength of the used light emitting element is 395 nm, and the half width is 15 nm. In Table 1, sample No. 3, 4 and 6-8 are reference samples.

  In the light emitting device of the present invention, high luminous efficiency was achieved.

It is sectional drawing of the light-emitting device using the fluorescent substance of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Electrode 2 ... Substrate 3 ... Light emitting element 4 ... Wavelength conversion layer 5 ... Phosphor 5a ... Blue phosphor 5b ... Green phosphor 5c ... Yellow phosphor 6 ... reflective member 40 ... wavelength conversion layer 50 ... wavelength conversion layer

Claims (1)

A substrate, a light emitting element that emits excitation light mounted on the substrate, and a wavelength conversion layer that contains a phosphor that converts the excitation light so as to cover the light emitting element into visible light. In the light emitting device using the visible light as output light, the phosphor is
A first phosphor composed of (Sr, Ca, Ba, Mg) ₁₀ (PO ₄ ) ₆ Cl ₂ : Eu and (Sr, Ba) ₂ SiO ₄ : Eu and Ba ₃ MgSi ₂ O ₈ : Eu, Mn In combination with
Combination of the first phosphor and Sr ₅ Al ₂ (O, S) ₈ : Eu and SrOSi ₂ N ₂ O, the first phosphor and Sr ₅ Al ₂ (O, S) ₈ : Eu and CaSiAlN _3: combination of Eu, the light-emitting device according to claim any der Rukoto of.

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