TWI757521B - Wavelength conversion member and light-emitting device - Google Patents

Abstract

The present invention provides a wavelength conversion member with high light extraction efficiency and excellent luminous intensity, and a light-emitting device using the same. The wavelength conversion member of the present invention is characterized in that it is a plate-shaped wavelength conversion member 1 containing a phosphor, and has a light incident surface 1a and a light exit surface 1b on the opposite side of the light incident surface 1a, for converting light Ra _in is 0.01-0.05 μm, and Ra _out −Ra _in is 0.01-0.2 μm when the surface roughness of the incident surface 1 a is Ra _in and the surface roughness of the light exit surface 1 b is Ra _out .

Description

Wavelength conversion member and light-emitting device

The present invention relates to a wavelength conversion member for converting the wavelength of light emitted by a light emitting diode (LED: Light Emitting Diode) or a laser diode (LD: Laser Diode) into other wavelengths, and a light-emitting device using the same .

In recent years, as a next-generation light source that replaces fluorescent lamps or incandescent lamps, the industry has been paying more and more attention to light-emitting devices using LEDs or LDs. As an example of such a next-generation light source, a light-emitting device is disclosed that combines an LED that emits blue light and a wavelength converting member that absorbs a part of the light from the LED and converts it into yellow light. The light-emitting device emits a composite light of blue light emitted from the LED and yellow light emitted from the wavelength conversion member, that is, white light. In Patent Document 1, as an example of the wavelength conversion member, a wavelength conversion member in which an inorganic phosphor powder is dispersed in a glass matrix is proposed. [Prior Art Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2003-258308

[Problems to be Solved by Invention]

The above-mentioned wavelength conversion member has a problem that the light extraction efficiency is poor and sufficient luminous intensity cannot be obtained.

Therefore, an object of the present invention is to provide a wavelength conversion member with high light extraction efficiency and excellent luminous intensity, and a light-emitting device using the same. [Technical means to solve problems]

The inventors of the present invention have made intensive studies and found that by limiting the surface roughness of the light incident surface and the light exit surface of the wavelength conversion member to a specific range, the light extraction efficiency can be improved, and a wavelength conversion member with excellent luminous intensity can be obtained.

That is, the wavelength conversion member of the present invention is characterized in that it is a plate-shaped wavelength conversion member including a phosphor, and has a light incident surface and a light exit surface on the opposite side of the light incident surface, and is characterized in that the light is incident on the light incident surface. When the surface roughness of the surface is Ra _in and the surface roughness of the light exit surface is Ra _out , Ra _in is 0.01 to 0.05 μm, and Ra _out −Ra _in is 0.01 to 0.2 μm.

In the wavelength conversion member of the present invention, the surface roughness Ra _out of the light exit surface is preferably 0.06 μm or more. In this way, the light extraction efficiency can be further improved.

The wavelength conversion member of the present invention is preferably formed by dispersing phosphor powder in a glass matrix.

The wavelength conversion member of the present invention preferably has a thickness of 0.01 to 1 mm.

The light-emitting device of the present invention is characterized by including the wavelength conversion member described above, and a light-emitting element for irradiating excitation light to the wavelength conversion member.

In the light-emitting device of the present invention, the light-incidence surface of the wavelength conversion member and the light-emitting element are preferably bonded by an adhesive layer.

In the light-emitting device of the present invention, a reflection layer is preferably disposed around the wavelength conversion member and the light-emitting element. [Effect of invention]

According to the present invention, a wavelength conversion member having high light extraction efficiency and excellent luminous intensity, and a light emitting device using the same can be provided.

Hereinafter, preferred embodiments will be described. However, the following embodiments are merely examples, and the present invention is not limited to the following embodiments. In addition, in each drawing, the member which has substantially the same function may be referred to by the same code|symbol.

FIG. 1 is a schematic cross-sectional view showing a wavelength conversion member according to an embodiment of the present invention. The wavelength conversion member 1 has a rectangular plate shape, for example. The wavelength conversion member 1 includes a phosphor, and has a light incident surface 1a and a light exit surface 1b on the opposite side of the light incident surface 1a. The excitation light that excites the phosphor contained in the wavelength conversion member 1 is used as the incident light L _in from the light incident surface 1 a of the wavelength conversion member 1 . The incident light L _in is converted into fluorescent light by wavelength conversion by a phosphor. The combined light of the fluorescent light and the incident light L _in without wavelength conversion is emitted from the light emitting surface 1b as outgoing light L _out . For example, when the incident light L _in is blue light and the fluorescent light is yellow light, white light, which is a composite light of blue light and yellow light, is emitted as L _out .

In the case where the surface roughness of the light incident surface 1a of the wavelength conversion member 1 is Ra _in and the surface roughness of the light exit surface 1b is Ra _out , Ra _in satisfies 0.01 to 0.05 μm, and Ra _out −Ra _in satisfies 0.01 to 0.2 μm. Thereby, the light extraction efficiency can be improved. The reason for this is presumed as follows. By making the surface roughness Ra _in of the light incident surface 1a relatively small, the incident light _Lin is less likely to be scattered on the surface of the light incident surface 1a, and the incidence efficiency into the wavelength conversion member 1 is improved. The reason for this is considered to be that the incident light Lin is generally light emitted from LEDs or LDs, and therefore has high straightness (alignment) and a large ratio to light _in the vertical direction to the light incident surface 1a. On the other hand, by making the surface roughness Ra _out of the light exit surface 1b relatively larger than Ra _in , the light extraction efficiency of the outgoing light L _out can be improved. Since the wavelength conversion member 1 is basically a light scatterer, incident light L _in or fluorescent light is scattered inside the wavelength conversion member 1 and aligned in all directions. Therefore, if the surface roughness Ra _out of the light exit surface 1b is small, the light component exceeding the critical angle increases, and the light extraction efficiency tends to decrease. Therefore, by increasing the surface roughness Ra _out of the light exit surface 1b, the effect of suppressing light reflection with respect to scattered light can be enhanced.

If Ra _in is too large, the incident light _Lin is scattered on the surface of the light incident surface 1a, and the incidence efficiency into the inside of the long conversion member 1 tends to decrease. As a result, the light extraction efficiency of the wavelength conversion member decreases, and the luminous intensity tends to decrease. On the other hand, if Ra _in is too small, the anchoring effect is not easily obtained when bonding with a light-emitting element (described below), and the bonding strength tends to decrease. Furthermore, if the wavelength conversion member 1 is partially peeled off from the light-emitting element due to the decrease _in the adhesion strength, an air layer with a low refractive index is formed between the wavelength conversion member 1 and the light-emitting element, so that the incidence efficiency of the incident light Lin increases. Tendency to decrease significantly. The preferred range of Ra _in is 0.015-0.045 μm.

If Ra _out −Ra _in is too small, the outgoing light L _out is likely to be reflected on the light outgoing surface 1 b, and the light extraction efficiency is likely to decrease. On the other hand, if Ra _out −Ra _in is too large, the scattering of the outgoing light L _out on the light outgoing surface 1 b increases, and on the contrary, the light extraction efficiency tends to decrease. The preferable range of Ra _out -Ra _in is 0.02-0.18 μm, and the more preferable range is 0.05-0.17 μm.

Furthermore, Ra _out is preferably 0.06 μm or more, 0.07 μm or more, especially 0.08 μm or more, and preferably 0.25 μm or less, 0.23 μm or less, especially 0.22 μm or less. If Ra _out is too small, the outgoing light L _out is likely to be reflected on the light outgoing surface 1b, and the light extraction efficiency is likely to decrease. On the other hand, if Ra _out is too large, the scattering of the outgoing light L _out on the light outgoing surface 1b increases, and the light extraction efficiency tends to decrease.

The wavelength conversion member 1 includes, for example, a phosphor glass containing a glass matrix and phosphor powder dispersed in the glass matrix.

The glass matrix is not particularly limited as long as it can be used as a dispersion medium for phosphor powders such as inorganic phosphors. For example, borosilicate-based glass, phosphate-based glass, tin-phosphate-based glass, bismuth-based glass, tellurite-based glass, and the like can be used. Examples of borosilicate glass include 30 to 85% by mass of SiO ₂ , 0 to 30% of Al ₂ O ₃ , 0 to 50% of B ₂ O ₃ , and Li ₂ O+Na ₂ O+K ₂ O 0 to 0% by mass. 10%, and MgO+CaO+SrO+BaO 0-50%. As a tin phosphate type glass, what contains SnO 30-90% and _{P2O5 1-70} % in molar % is mentioned. As the tellurite glass, 50% or more of TeO ₂ , 0 to 45% of ZnO, and 0 to 50% of RO (R is at least one selected from Ca, Sr, and Ba) are included in mol %. , and La ₂ O ₃ +Gd ₂ O ₃ +Y ₂ O ₃ 0 to 50%.

The softening point of the glass matrix is preferably within the range of 250°C to 1000°C, more preferably 300°C to 950°C, and still more preferably 500°C to 900°C. If the softening point of the glass matrix is too low, there is a case where the mechanical strength or chemical durability of the wavelength conversion member 1 is lowered. In addition, since the heat resistance of the glass substrate itself is low, there is a possibility of softening and deformation due to heat generated from the phosphor. On the other hand, if the softening point of the glass matrix is too high, there is a case where a firing step is included in the manufacture, and there is a case where the luminous intensity of the wavelength conversion member 1 is lowered due to the deterioration of the phosphor. Moreover, when the softening point of a glass matrix becomes high, the baking temperature also becomes high, and there exists a tendency for manufacturing cost to become high as a result. Furthermore, from the viewpoint of improving the chemical stability and mechanical strength of the wavelength conversion member 1, the softening point of the glass matrix is preferably 500°C or higher, 600°C or higher, 700°C or higher, 800°C or higher, particularly 850°C or higher. . As such glass, borosilicate glass is mentioned. On the other hand, the softening point of the glass matrix is preferably 550°C or lower, 530°C or lower, 500°C or lower, 480°C or lower, particularly 460°C or lower, from the viewpoint of inexpensively producing the wavelength conversion member 1 . Examples of such glass include tin phosphate-based glass, bismuthate-based glass, and tellurite-based glass.

The fluorescent substance is not particularly limited as long as it emits fluorescent light upon incidence of excitation light. Specific examples of the phosphors include, for example, oxide phosphors, nitride phosphors, oxynitride phosphors, chloride phosphors, oxychloride phosphors, and sulfide phosphors. One or more of phosphors, oxysulfide phosphors, halide phosphors, chalcogenide phosphors, aluminate phosphors, halophosphoric acid chloride phosphors, and garnet-based compound phosphors, etc. . When blue light is used as the excitation light, for example, a phosphor that emits green light, yellow light, or red light in the form of fluorescent light can be used.

The average particle size of the phosphor powder is preferably 1 μm to 50 μm, more preferably 5 μm to 25 μm. When the average particle size of the phosphor powder is too small, the luminous intensity may decrease. On the other hand, if the average particle size of the phosphor powder is too large, the emission color may become uneven.

The content of the phosphor powder in the wavelength conversion member 1 is preferably 1 vol% or more, 1.5 vol% or more, especially 2 vol%, and preferably 70 vol% or less, 50 vol% or less, and 30 vol% or less. If the content of the phosphor powder is too small, the thickness of the wavelength conversion member 1 must be thick in order to obtain the desired luminescent color. As a result, the internal scattering of the wavelength conversion member 1 may increase, resulting in a decrease in light extraction efficiency. On the other hand, if the content of the phosphor powder is too large, the thickness of the wavelength conversion member 1 must be made thin in order to obtain a desired luminescent color, and thus the mechanical strength of the wavelength conversion member 1 may decrease.

The thickness of the wavelength conversion member 1 is preferably 0.01 mm or more, 0.03 mm or more, 0.05 mm or more, 0.075 mm or more, especially 0.08 mm or more, and preferably 1 mm or less, 0.5 mm or less, 0.35 mm or less, 0.3 mm or less , 0.25 mm or less, 0.15 mm or less, especially 0.12 mm or less. If the thickness of the wavelength conversion member 1 is too thick, scattering or absorption of light in the wavelength conversion member 1 may become too large, resulting in a decrease in light extraction efficiency. If the thickness of the wavelength conversion member 1 is too thin, it may be difficult to obtain sufficient luminous intensity. Moreover, the mechanical strength of the wavelength conversion member 1 may become insufficient.

The refractive index (nd) of the wavelength conversion member 1 is preferably 1.40 or more, 1.45 or more, and 1.50 or more, and more preferably 1.90 or less, 1.80 or less, and 1.70 or less. If the refractive index of the wavelength conversion member 1 is too high, the difference in refractive index between the wavelength conversion member 1 and the medium on the light exit side (for example, the air layer (nd=1.0)) becomes large, which is likely to occur on the light exit surface 1b. Total reflection, resulting in a situation where the light extraction efficiency is reduced. If the refractive index of the wavelength conversion member 1 is too low, the difference in refractive index with a light-emitting element (for example, a flip-chip LED. The output surface is sapphire, nd=1.76) becomes large. Therefore, even when an adhesive layer is provided between the wavelength conversion member 1 and the light-emitting element and the difference in refractive index is adjusted by the adhesive layer, there is a difference in refractive index between the light-emitting element and the adhesive layer and/or the adhesive layer. The difference in refractive index with the wavelength conversion member 1 increases, and the light extraction efficiency at each interface decreases.

An anti-reflection film may also be provided on the light exit surface 1 b of the wavelength conversion member 1 . In this way, when fluorescent light or excitation light is emitted from the light exit surface 1b, the reduction of the light extraction efficiency caused by the difference in refractive index between the wavelength conversion member 1 and the air can be suppressed. As the antireflection film, a single-layer or multi-layer dielectric film including SiO ₂ , Al ₂ O ₃ , TiO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ and the like can be exemplified.

An anti-reflection film may also be provided on the light incident surface 1 a of the wavelength conversion member 1 . In this way, when excitation light is incident on the wavelength conversion member 1 , the reduction in the excitation light incidence efficiency due to the difference in refractive index between the adhesive layer and the wavelength conversion member 1 can be suppressed.

Furthermore, when the wavelength conversion member 1 includes fluorescent glass, the antireflection film is usually designed in consideration of the refractive index of the glass matrix in the wavelength conversion member 1 . Here, if the phosphor powder is exposed on the light exit surface 1b of the wavelength conversion member 1, since the refractive index of the phosphor powder is relatively high, the anti-reflection film formed on the phosphor powder portion is not suitable. Due to the film design, there is a risk that a sufficient anti-reflection function cannot be obtained. Therefore, it is preferable to provide a glass layer (a glass layer not containing phosphor powder) on the light exit surface 1b of the wavelength conversion member 1 so as to cover the exposed phosphor powder. In this way, the refractive index of the light exit surface 1b of the wavelength conversion member 1 becomes uniform, and the effect obtained by the antireflection film can be enhanced. Furthermore, it is preferable that the glass layer for enhancing the anti-reflection effect is also provided on the light incident surface 1a of the wavelength conversion member 1 as described above.

The glass that constitutes the glass layer is preferably the same glass that constitutes the glass matrix in the elongated conversion member 1 . In this way, the difference in refractive index between the glass matrix and the glass layer in the wavelength conversion member 1 disappears, and light reflection loss at the two interfaces can be suppressed. Furthermore, when the glass layer is provided, it is preferable that the surface roughness of the surface of the glass layer satisfies the range of the above-mentioned surface roughness Ra _out . The thickness of the glass layer is preferably 0.003-0.1 mm, 0.005-0.03 mm, especially 0.01-0.02 mm. If the thickness of the glass layer is too small, there is a possibility that the exposed phosphor powder cannot be sufficiently covered. On the other hand, if the thickness of the glass layer is too large, excitation light or fluorescent light may be absorbed, resulting in a decrease in luminous efficiency.

Furthermore, the wavelength conversion member 1 may be made of not only phosphor glass, but also ceramics such as YAG (Yttrium Aluminum Garnet) ceramics, or phosphor powder dispersed in resin.

The wavelength conversion member 1 can be produced as follows. First, a plate-shaped wavelength conversion member precursor is produced. The wavelength conversion member precursor can be produced, for example, by cutting a sintered body of a mixture of phosphor powder and glass powder. Next, the wavelength conversion member 1 is obtained by polishing the two principal surfaces of the wavelength conversion member precursor, that is, the light incident surface and the light output surface so as to obtain a desired surface roughness. Here, the surface roughness of the both main surfaces of the wavelength conversion member 1 is adjusted by appropriately selecting the polishing pad or the abrasive grains. The two main surfaces of the precursor of the wavelength conversion member can be polished at the same time, or they can be polished one by one in sequence (polishing the light incident surface and then polishing the light exit surface, or polishing the light exit surface and then polishing the light incident surface) . For example, a method of grinding the light incident surface with a single-side grinder after rough grinding of both sides of the wavelength conversion member 1 with a double-side grinder; or a method of using a single-side grinder to convert wavelengths with different abrasive The method of polishing the light incident surface and the light exit surface of the member 1 in sequence one by one.

FIG. 2 is a schematic cross-sectional view showing a light-emitting device according to an embodiment of the present invention. The light-emitting device 10 is formed by bonding the wavelength conversion member 1 and the light-emitting element 2 with the adhesive layer 3 . In this embodiment, the light-emitting element 2 is provided on the substrate 4 . Moreover, the reflection layer 5 is arrange|positioned around the wavelength conversion member 1, the light emitting element 2, and the adhesive agent layer 3. By disposing the reflective layer 5, the excitation light and the fluorescent light can be suppressed from being reflected and leaked to the outside, and the light extraction efficiency can be improved. The light-emitting element 2 has substantially the same shape and area as the wavelength conversion member 1 in plan view. However, the wavelength conversion member 1 and the light emitting element 2 may have different shapes and areas. For example, one wavelength conversion member 1 is attached to a plurality of light-emitting elements 2 arranged in parallel so as to cover the plurality of light-emitting elements 2 .

As the light-emitting element 2, for example, a light source such as an LED light source or an LD light source that emits blue light can be used. As an adhesive agent which comprises the adhesive agent layer 3, a silicone resin type, an epoxy resin type, a vinyl type resin type, an acrylic resin type, etc. are mentioned, for example. The adhesive constituting the adhesive layer 3 preferably has a refractive index close to that of the wavelength conversion member 1 . In this way, the excitation light emitted from the light-emitting element 2 can be efficiently incident on the wavelength conversion member 1 . As the substrate 4 , for example, white LTCC (Low Temperature Co-fired Ceramics) that can efficiently reflect the light emitted from the light-emitting element 2 can be used. Specifically, sintered bodies of inorganic powders such as alumina, titania, and niobium oxide and glass powders can be mentioned. Alternatively, a ceramic substrate such as alumina or aluminum nitride may be used. As the reflection layer 5, a resin composition or glass ceramics can be used. As the resin composition, a mixture of resin and ceramic powder or glass powder can be used. As glass ceramics, LTCC etc. are mentioned. As the material of the glass ceramics, a mixed powder of glass powder and ceramic powder, or a crystalline glass powder can be used. [Example]

Hereinafter, the wavelength conversion member of the present invention will be described in detail by way of examples, but the present invention is not limited to the following examples.

Table 1 shows Examples 1 and 2 and Comparative Examples 1 to 3.

[Table 1]

YAG phosphor powder (average particle size D ₅₀ : 15 μm) was mixed with borosilicate glass powder (average particle size D ₅₀ : 2 μm, softening point 850° C.) to obtain a mixed powder. The content of the YAG phosphor powder in the mixed powder was set to 8.3% by volume. A sintered body is obtained by press-molding the mixed powder with a mold, and calcining in the vicinity of the softening point. By cutting the obtained sintered body, a wavelength conversion member precursor having a plate shape of 30 mm×30 mm×0.3 mm was obtained. Using a single-sided grinder, the wavelength conversion member precursor was polished by changing abrasive grains surface by surface so that the light incident surface and the light exit surface had specific surface roughnesses, thereby producing a wavelength conversion member. The obtained wavelength conversion member was cut into an outer dimension of 1 mm×1 mm to obtain a small piece of wavelength conversion member.

The beam value was measured for the wavelength converting member of the obtained platelet in the following manner. The surface of the LED chip with an excitation wavelength of 450 nm is coated with a silicone resin, followed by the wavelength conversion member of the small chip, and the outer periphery of the LED chip and the wavelength conversion member of the small chip is coated with a highly reflective silicone resin to obtain a sample for measurement. . The light emitted from the light exit surface of the wavelength conversion member of the chip is captured into the interior of the integrating sphere, and then the light is introduced into a beam splitter calibrated by a standard light source to measure the energy distribution pattern of the light. The beam value is calculated from the obtained energy distribution pattern. In addition, the beam value of Table 1 is represented by the relative value which set the beam value of Example 1 as 1.

As shown in Table 1, the relative beam values of the wavelength conversion members of Examples 1 and 2 were 0.99 or more, while the relative beam values of the wavelength conversion members of Comparative Examples 1 to 3 were inferior to 0.95 or less.

1‧‧‧Wavelength converting member 1a‧‧‧Light incident surface 1b‧‧‧Light exit surface 2‧‧‧Light-emitting element 3‧‧‧Adhesive layer 4‧‧‧Substrate 5‧‧‧Reflecting layer 10‧‧‧Light device

FIG. 1 is a schematic cross-sectional view showing a wavelength conversion member according to an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view showing a light-emitting device according to an embodiment of the present invention.

Claims (8)

A wavelength conversion member is characterized in that: it is a plate-shaped wavelength conversion member containing a phosphor, and has a light incident surface and a light exit surface opposite to the light incident surface, wherein the light incident surface is When the surface roughness is set to Ra _in and the surface roughness of the light exit surface is set to Ra _out , Ra _in is 0.01 to 0.05 μm, and Ra _out −Ra _in is 0.01 to 0.2 μm. The wavelength conversion member according to claim 1, wherein the surface roughness Ra _out of the light exit surface is 0.06 μm or more. As claimed in claim 1, the wavelength conversion member is formed by dispersing phosphor powder in a glass matrix. As claimed in claim 2, the wavelength conversion member is formed by dispersing phosphor powder in a glass matrix. The wavelength conversion member according to any one of claims 1 to 4, whose thickness is 0.01-1 mm. A light-emitting device comprising: the wavelength conversion member according to any one of claims 1 to 5, and a light-emitting element for irradiating the wavelength conversion member with excitation light. The light-emitting device according to claim 6, wherein the light-incidence surface of the wavelength conversion member and the light-emitting element are bonded to each other by an adhesive layer. The light-emitting device according to claim 6 or 7, wherein a reflection layer is arranged around the wavelength conversion member and the light-emitting element.

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