TW201830733A - Light emitting device - Google Patents

Abstract

Provided is a light emitting device which is capable of improving the extraction efficiency for excitation light, thereby being capable of enhancing the luminous efficiency. This light emitting device is characterized by comprising a wavelength conversion member 3 which is obtained by dispersing phosphor particles 8 in a glass matrix 7, a light source 2 which irradiates the wavelength conversion member 3 with excitation light, and an adhesive layer 4 which is arranged between the wavelength conversion member 3 and the light source 2. This light emitting device is also characterized in that the difference between the refractive index of the glass matrix 7 and the refractive index of the adhesive layer 4 is 0.1 or less.

Description

Illuminating device

The present invention relates to a light-emitting device using an excitation light source such as an LED (Light Emitting Diode) or an LD (Laser Diode).

In recent years, as a next-generation light source that replaces a fluorescent lamp or an incandescent lamp, a light-emitting device using an excitation light source such as an LED or an LD has been attracting attention. As an example of such a next-generation light source, a light-emitting device in which an LED that emits blue light and a wavelength conversion member that absorbs a part of light from the LED and converts it into yellow light are known in the art. The illuminating device emits white light which is a combination of the blue light emitted from the LED and the yellow light emitted from the wavelength converting member. As the wavelength converting member, those conventionally used for dispersing inorganic phosphor powder in a resin matrix have been used. However, in the case of using the wavelength conversion member, there is a problem that the deterioration of the resin due to light from the LED causes the luminance of the light-emitting device to be easily lowered. In particular, there is a problem that the mold resin is deteriorated due to heat generated by the LED or short-wavelength (blue to ultraviolet) light of high energy, causing discoloration or deformation. Therefore, a wavelength conversion member including a completely inorganic solid in which a phosphor is dispersed and fixed in a glass matrix instead of a resin has been proposed (see, for example, Patent Documents 2 and 3). This wavelength conversion member is characterized in that the glass to be a base material is less likely to be deteriorated by heat of the LED or the irradiation light, and it is difficult to cause discoloration or deformation. [Prior Art Document] [Patent Document 1] Japanese Patent Laid-Open Publication No. 2000-208815 (Patent Document 2) Japanese Patent Laid-Open Publication No. JP-A No. 2003-258308 (Patent Document 3) Japanese Patent Laid-Open No. 2007-016171 Bulletin

[Problems to be Solved by the Invention] When a flip-chip type LED or the like is used as a light source, there is a case where an adhesive layer is disposed between the light source and the wavelength conversion member and fixed. The excitation light from the light source is incident on the wavelength conversion member through the adhesive layer. The excitation light is converted into fluorescence by the phosphor contained in the wavelength conversion member, and is emitted from the surface opposite to the light source of the wavelength conversion member together with the excitation light without wavelength conversion. Here, when the refractive index difference between the wavelength conversion member and the air layer on the light exit side is large, light reflection occurs at the interface between the two, and the light extraction efficiency is liable to lower. Therefore, in order to reduce the difference in refractive index between the wavelength converting member and the air layer, it is considered to lower the refractive index of the wavelength converting member. However, there is a case where the light extraction efficiency is not necessarily improved even if only the refractive index of the wavelength converting member is lowered. This fact suggests that the light extraction efficiency is also related to the cause of the difference in refractive index between the wavelength converting member and the air layer. However, in order to optimize the light extraction efficiency of the light-emitting device, the relationship between the refractive indices of the members constituting the light-emitting device has not been sufficiently studied. It is an object of the present invention to provide a light-emitting device which can improve the extraction efficiency of excitation light and improve the light-emitting efficiency. [Means for Solving the Problems] The light-emitting device of the present invention includes a wavelength conversion member in which phosphor particles are dispersed in a glass matrix, a light source that emits excitation light to the wavelength conversion member, and a wavelength conversion member and a light source. The adhesive layer is interposed and the difference in refractive index between the glass substrate and the adhesive layer is 0.1 or less. The refractive index of the glass substrate is preferably 1.6 or less. The subsequent layer is preferably composed of an anthrone resin. The refractive index of the glass substrate is preferably 1.48 or more. Preferably, a reflection layer is provided around the wavelength conversion member, the light source, and the adhesive layer. In this case, the reflective layer is preferably composed of a resin composition or a glass ceramic. [Effect of the Invention] According to the present invention, the extraction efficiency of the excitation light can be improved to improve the luminous efficiency.

Hereinafter, preferred embodiments will be described. However, the following embodiments are merely illustrative, and the present invention is not limited to the following embodiments. In the drawings, members having substantially the same function may be referred to by the same reference numerals. Fig. 1 is a schematic cross-sectional view showing a light-emitting device according to an embodiment of the present invention. Fig. 2 is a schematic plan view showing a light-emitting device according to an embodiment of the present invention. As shown in FIG. 1, the light-emitting device 1 of the present embodiment includes a wavelength conversion member 3, a light source 2 that emits excitation light to the wavelength conversion member 3, and an adhesive layer 4 that is provided between the wavelength conversion member 3 and the light source 2. As shown in FIGS. 1 and 2, in the present embodiment, the light source 2 is provided on the substrate 5. Further, a reflective layer 6 is disposed around the wavelength conversion member 3, the light source 2, and the adhesive layer 4. By arranging the reflective layer 6, the excitation light and the fluorescent light can be reflected to suppress light leakage to the outside, and the light extraction efficiency can be improved. Fig. 3 is a schematic cross-sectional view showing an enlarged wavelength conversion member in a light-emitting device according to an embodiment of the present invention. As shown in FIG. 3, the wavelength conversion member 3 is constituted by dispersing the phosphor particles 8 in the glass substrate 7. As the light source 2, an LED, an LD, or the like can be used. In the case where an LED wafer is used as the light source 2, the LED wafer can be flip-chip mounted. As the flip chip type LED, for example, a sapphire layer is provided on the light-emitting layer. The sapphire layer is disposed on the exit side of the excitation light. An adhesive layer 4 is provided on the light source 2. A wavelength converting member 3 is provided on the adhesive layer 4. The excitation light emitted from the light source 2 is incident on the wavelength conversion member 3 through the adhesive layer 4. The phosphor particles 8 are excited by the excitation light incident on the wavelength conversion member 3, and the fluorescence is emitted from the phosphor particles 8. The synthesized light emitted from the phosphor particles 8 and the excitation light that has passed through the wavelength conversion member 3 is emitted from the wavelength conversion member 3. Further, as described above, in order to improve the light extraction efficiency of the light-emitting device, there is a case where the light extraction efficiency is not necessarily improved even if only the refractive index of the wavelength conversion member is lowered. It is also shown in the test data below. According to the results of investigations by the inventors of the present invention, it has been found that the difference in refractive index between the glass substrate constituting the wavelength converting member and the adhesive layer affects the light extraction efficiency. Specifically, in the present embodiment, the difference in refractive index between the glass substrate 7 of the wavelength conversion member 3 and the adhesive layer 4 is set to 0.1 or less. Thereby, it is possible to suppress the reflection of the excitation light at the interface between the wavelength conversion member 3 and the adhesive layer 4, and it is possible to improve the extraction efficiency of the excitation light and improve the luminous efficiency. Examples of the adhesive constituting the adhesive layer 4 include an anthrone resin type, an epoxy resin type, an ethylene resin type, and an acrylic resin type. The difference in refractive index (nd) between the glass substrate 7 and the adhesive layer 4 is preferably 0.08 or less, more preferably 0.07 or less, and still more preferably 0.04 or less. The refractive index of the subsequent agent layer 4 is preferably in the range of 1.38 to 1.60, more preferably in the range of 1.40 to 1.58. The refractive index of the glass substrate 7 is preferably in the range of 1.48 to 1.60, more preferably in the range of 1.50 to 1.58. The glass substrate 7 can be used as a dispersion medium of the phosphor particles 8 such as an inorganic phosphor, and is not particularly limited as long as it has a refractive index within the above range. For example, a borosilicate type glass, a phosphate type glass, a tin phosphate type glass, a bismuth silicate type glass, etc. can be used. Examples of the borosilicate-based glass include 30 to 85% of SiO ₂ , 0 to 30% of Al ₂ O ₃ , 0 to 50% of B ₂ O ₃ , and 0 to 10% of Li. ₂ O + Na ₂ O + K ₂ O, and 0 to 50% of MgO + CaO + SrO + BaO. Examples of the tin phosphate-based glass include 30 to 90% of SnO and 1 to 70% of P ₂ O ₅ in terms of mol%. The softening point of the glass substrate 7 is preferably in the range of from 250 ° C to 1000 ° C, more preferably in the range of from 300 ° C to 950 ° C, still more preferably in the range of from 500 ° C to 900 ° C. If the softening point of the glass substrate 7 is too low, there is a case where the mechanical strength or chemical durability of the wavelength converting member 3 is lowered. Further, since the heat resistance of the glass substrate 7 itself is lowered, there is a case where softening deformation occurs due to heat generated from the phosphor particles 8. On the other hand, when the softening point of the glass substrate 7 is too high, there is a case where the phosphor particles 8 are deteriorated due to the heating step at the time of production, and the light-emitting intensity of the wavelength conversion member 3 is lowered. Further, the glass substrate 7 is preferably an alkali-free glass. Thereby, the deactivation of the phosphor particles 8 can be suppressed. Further, from the viewpoint of improving the chemical stability and mechanical strength of the wavelength conversion member 3, the softening point of the glass substrate 7 is preferably 500 ° C or higher, 600 ° C or higher, 700 ° C or higher, 800 ° C or higher, especially 850 ° C. the above. As such a glass, a borosilicate type glass is mentioned. However, when the softening point of the glass substrate 7 becomes high, the baking temperature also rises, and the manufacturing cost tends to become high. Therefore, from the viewpoint of producing the wavelength conversion member 3 at a low price, the softening point of the glass substrate 7 is preferably 550 ° C or lower, 530 ° C or lower, 500 ° C or lower, 480 ° C or lower, or particularly 460 ° C or lower. Examples of such a glass include tin phosphate-based glass and silicate-based glass. The phosphor particles 8 are not particularly limited as long as they emit fluorescence by the incidence of the excitation light. Specific examples of the phosphor particles 8 include, for example, an oxide phosphor, a nitride phosphor, an oxynitride phosphor, a chloride phosphor, a ruthenium chloride phosphor, and a sulfide fluorite. One of a light body, an oxysulfide phosphor, a halide phosphor, a chalcogenide phosphor, an aluminate phosphor, a halophosphorus chloride phosphor, and a garnet compound phosphor The above. In the case where blue light is used as the excitation light, for example, a phosphor which emits green light, yellow light or red light in the form of fluorescence can be used. The content of the phosphor particles 8 in the glass substrate 7 is preferably in the range of 1 to 70% by volume, more preferably in the range of 1.5 to 50% by volume, still more preferably in the range of 2 to 30% by volume. When the content of the phosphor particles 8 is too small, the light-emitting intensity of the wavelength conversion member 3 may be insufficient. On the other hand, if the content of the phosphor particles 8 is too large, there is a case where the desired luminescent color cannot be obtained. Further, there is a case where the mechanical strength of the wavelength conversion member 3 is lowered. In the present embodiment, as the substrate 5, for example, white LTCC (Low Temperature Co-fired Ceramics) which can efficiently reflect light emitted from the light source 2 is used. Specific examples thereof include a sintered body of an inorganic powder such as alumina, titania or cerium oxide and a glass powder. Alternatively, a ceramic substrate such as alumina or aluminum nitride can be used. In the present embodiment, a resin composition or a glass ceramic can be used as the reflective layer 6. As the resin composition, a mixture of a resin and a ceramic powder or a glass powder can be used. Examples of the glass ceramics include LTCC (Low Temperature Co-fired Ceramics) and the like. As the material of the glass ceramic, a mixed powder of glass powder and ceramic powder or a crystalline glass powder can be used. As the glass powder, SiO ₂ -B ₃ O ₃ -based glass, SiO ₂ -RO-based glass (R represents an alkaline earth metal), SiO ₂ -Al ₂ O ₃ -based glass, SiO ₂ -ZnO-based glass, or SiO ₂ -R can be used. ₂ O-based glass (R represents an alkali metal) or SiO ₂ -TiO ₂ -based glass. These glass powders may be used singly or in combination of plural kinds. As the ceramic powder, alumina, zirconia, titania or the like can be used. These ceramic powders may be used singly or in combination of plural kinds. Fig. 4 is a view showing the relationship between the refractive index of the matrix of the wavelength converting member and the light beam. Specifically, it is a light beam emitted from a light-emitting device which is formed by combining an adhesive layer 4 formed by using an fluorenone resin having a refractive index (nd) of 1.54 as an adhesive and a wavelength conversion member 3 having a material having a different refractive index as a substrate, The relationship with the refractive index of the matrix of the wavelength converting member 3. The light source 2 is an LED that emits excitation light having a wavelength of 445 nm. The phosphor particles 8 are YAG (Yttrium Aluminum Garnet). The substrates A to K are as follows. A: low refractive index fluorenone resin B: molten cerium oxide C: basic borosilicate glass D: basic borosilicate glass E: basic borosilicate glass F: alkaline earth citrate glass G: bismuth citrate Glass H: barium borate glass I: barium titanate titanium glass J: barium zinc borate glass K: barium borate glass is a refraction of the light beam (lm) from each of the light-emitting devices using the above-mentioned respective substrates A to K and each substrate The rate (nd) is shown in Table 1. [Table 1] Fig. 4 is a graph showing the light beam (lm) shown in Table 1 and the refractive index (nd) of the substrate. In Fig. 4, the position of the refractive index (nd) of the adhesive layer is indicated by a broken line. As is clear from Table 1 and Figure 4, a higher beam can be obtained when the difference between the refractive index of the substrate and the refractive index of the adhesive layer is 0.1 or less. Further, it has been found that when the refractive index of the matrix is close to the refractive index of air (≒1.0), the beam value is decreased in the low refractive index region as compared with the vicinity of the refractive index 1.5. Therefore, according to the present invention, it is found that a high luminous intensity can be obtained by setting the difference in refractive index between the glass substrate and the adhesive layer to 0.1 or less. Further, it has been found that by setting the difference between the refractive indices of the glass substrate and the adhesive layer to 0.08 or less, a higher luminous intensity can be obtained, and by setting it to 0.07 or less, a higher luminous intensity can be obtained.

1‧‧‧Lighting device

2‧‧‧Light source

3‧‧‧wavelength conversion member

4‧‧‧ adhesive layer

5‧‧‧Substrate

6‧‧‧reflective layer

7‧‧‧ glass substrate

8‧‧‧Silver particles

Fig. 1 is a schematic cross-sectional view showing a light-emitting device according to an embodiment of the present invention. Fig. 2 is a schematic plan view showing a light-emitting device according to an embodiment of the present invention. Fig. 3 is a schematic cross-sectional view showing an enlarged wavelength conversion member in a light-emitting device according to an embodiment of the present invention. Fig. 4 is a view showing the relationship between the refractive index of the matrix of the wavelength converting member and the light beam.

Claims (6)

A light-emitting device comprising: a wavelength conversion member in which a phosphor particle is dispersed in a glass matrix; a light source that emits excitation light to the wavelength conversion member; and an adhesive layer provided between the wavelength conversion member and the light source, Further, the difference between the refractive indices of the glass substrate and the adhesive layer is 0.1 or less. The light-emitting device of claim 1, wherein the glass substrate has a refractive index of 1.6 or less. The light-emitting device of claim 1 or 2, wherein the above-mentioned adhesive layer is composed of an anthrone resin. The light-emitting device according to any one of claims 1 to 3, wherein the glass substrate has a refractive index of 1.48 or more. The light-emitting device according to any one of claims 1 to 4, wherein a reflection layer is provided around the wavelength conversion member, the light source, and the adhesive layer. The light-emitting device according to any one of claims 1 to 5, wherein the reflective layer is composed of a resin composition or a glass ceramic.