JP5034653B2 - Light emitting device using ceramic composite for light conversion - Google Patents

Description

  The present invention relates to a light-emitting device such as a light-emitting diode that can be used for a display, illumination, backlight light source, and the like, and more specifically, light emission using a ceramic composite for light conversion that is a light conversion member that obtains fluorescence using irradiated light. Relates to the device.

In recent years, research and development of white light emitting devices using a blue light emitting element as a light source have been actively conducted. In particular, white light-emitting diodes using blue light-emitting diodes are light in weight, do not use mercury, and have a long lifetime, so that demand is expected to increase rapidly in the future. The most commonly used method for converting blue light of a blue light emitting element into white light is to obtain a pseudo white color by mixing yellow having a complementary color relationship with blue. For example, as described in Patent Document 1, a coating layer made of a resin such as epoxy containing a phosphor that absorbs part of blue light and emits yellow light is formed on the front surface of a light emitting diode that emits blue light. A white light emitting diode can be formed by providing a mold layer or the like that mixes blue light of the light source and yellow light from the phosphor. As the phosphor, YAG (Y ₃ Al ₅ O ₁₂ ) powder activated with cerium is used.

  In addition, the applicant of the present application previously has a structure in which at least two or more oxide phases are continuously and three-dimensionally entangled with each other, and at least one of the oxide phases is a crystal that emits fluorescence. It discloses that a ceramic composite for light conversion comprising a solidified body as a phase is used for light conversion (Patent Document 2).

JP 2000-208815 A WO04-065324 pamphlet

  The performance of such white light emitting diodes has been improved year by year, and their application fields have been greatly expanded from conventional backlights for mobile phones to display backlights and lighting devices. Along with this, various demands have been made for the light distribution of white light emitting diodes, and for example, backlights are required to have an anisotropic light distribution of narrow and wide light. There is also a demand for higher output.

  However, in the structure of white light emitting diodes generally used at present, represented by Patent Document 1, the light from the light emitting elements is scattered by the phosphor powder, so the directivity is weakened, and the anisotropic light distribution In order to obtain this, it is necessary to add a member such as a reflector. For this reason, the structure becomes complicated, and the cost increases due to an increase in the number of parts and processes.

  In addition, the resin required when using phosphor powder is inferior in heat resistance compared to metals and ceramics, so it is likely to cause a decrease in transmittance due to heat transformation from the light emitting element, and the bottleneck to increasing the output of white light emitting diodes. It has become.

  The light conversion member disclosed in Patent Document 2 solves the above problems to a certain extent, but it is desirable to further increase the output of the white light emitting diode and to increase or adjust the directivity.

  An object of the present invention is to provide a light emitting device that can easily obtain different light distribution properties and is extremely suitable for high output at low cost.

  The present inventor has found that the light emission can be increased (the light emission rate is high) by changing the surface texture of the light conversion ceramic composite, and the surface texture on the light output surface of the ceramic composite for light conversion is high. The present invention has been completed by finding that the above-mentioned problems can be solved by configuring it to include different parts. That is, the present invention is as follows.

  (1) In a light emitting device composed of a light emitting element and a ceramic composite for light conversion, the ceramic composite for light conversion has a structure in which at least two oxide phases are continuously and three-dimensionally entangled with each other. In addition, at least one of the oxide phases is formed of a solidified body that is a crystal phase that emits fluorescence, and includes a portion having a different surface texture on a light emitting surface of the ceramic composite for light conversion, and a portion having a different surface texture. A light emitting device having a light emission rate different by 2% or more.

  (2) The light-emitting device according to (1) above, wherein a difference in arithmetic average surface roughness (Ra) between portions having different surface textures is 0.1 μm or more.

  (3) The light-emitting device according to (1) above, wherein the surface texture is surface unevenness, and the uneven step is different by 0.5 μm or more.

  (4) The light-emitting device according to (3) above, wherein the surface irregularities are irregularities for each oxide phase constituting the ceramic composite.

  (5) The ceramic composite for light conversion has a light incident surface, a first light emitting surface, and a second light emitting surface other than the first light emitting surface, and the first light emitting surface; The light emitting device according to any one of (1) to (4), wherein the second light emitting surface has a different surface texture and a different light emitting rate from the light emitting element by 2% or more.

  (6) The light emitting device according to (5), wherein the first light emission surface is opposed to the light incident surface.

  (7) The light-emitting device according to any one of (1) to (6), wherein the light-emitting surface includes a portion where the surface texture of the light exit surface gradually changes.

  (8) The light-emitting device is a backlight, the light-converting ceramic composite has a plate shape having a main surface, and light is incident from the lateral direction on the side surface of the light-converting ceramic composite from the light-emitting element, It is a backlight emitted from the main surface of the plate of the ceramic composite for light conversion, the surface texture gradually changes as the distance from the light incident site in the main surface of the light composite ceramic composite for light emission, 6. The light emitting device according to any one of (1) to (5) above, wherein the amount of light emitted from the main surface is made equal.

  (9) The light-emitting device according to any one of (1) to (8), wherein the ceramic composite for light conversion includes at least a Y element, an Al element, and a Ce element as composition components. .

  (10) The light-emitting device according to any one of (1) to (9), wherein the light-emitting element is a light-emitting diode.

  (11) The above (1) to (1), wherein the ceramic composite for light conversion emits fluorescence having a peak at a wavelength of 530 to 580 nm, and the light emitting element emits light having a peak at a wavelength of 400 nm to 520 nm. 10. The light emitting device according to any one of 10).

  The light-emitting device of the present invention can easily obtain different required light distribution properties by adjusting the surface texture of the ceramic composite for light conversion to be optimal in each part. Since light emission (light emission) in a desired direction can be increased, light emission efficiency as a light emitting element can also be increased. For this reason, there is no need for special parts for controlling the light distribution, and an increase in cost can be avoided. Furthermore, since the ceramic composite for light conversion is excellent in heat resistance and itself is a bulk body, a resin is not necessarily required for the configuration of the white light emitting device. For this reason, the light distribution of the light emitting device can be easily controlled, and a white light emitting device that is extremely suitable for high output and does not require a heat-sensitive resin can be provided at low cost.

  Hereinafter, the present invention will be described in detail.

  The light-emitting device of the present invention is a device composed of a light-converting ceramic composite and a light-emitting element, and irradiates light from the light-emitting element to the light-converting ceramic composite and transmits the light transmitted through the light-converting ceramic composite and Further, the present invention is characterized in that the light from the light emitting element uses fluorescence whose wavelength is converted by the ceramic composite for light conversion.

  FIG. 1 is a schematic cross-sectional view showing an embodiment of a light emitting device of the present invention. This ceramic composite 2 for light conversion is a solidified body having a structure in which at least two oxide phases are continuously and three-dimensionally entangled with each other, and at least one of these oxide phases is fluorescent. It is a crystal phase that emits. The ceramic composite 2 for light conversion in FIG. 1 is a rectangular parallelepiped, but the bottom surface faces the light emitting element 1 and is attached to the attachment member 5 of the apparatus main body, and the five surfaces 2b, 2c, 2d other than the bottom surface 2a are external. To form a light emitting surface (light emitting surface). A part of the light from the light emitting element 1 is converted into fluorescence in the ceramic composite 2 for light conversion, and these lights are emitted together from the ceramic composite for light conversion. The light distribution of the light emitting device can be controlled by changing the surface texture of the portions 2b, 2c, 2d and the like that emit light of the ceramic composite for light conversion depending on the site. The light extraction efficiency when light is emitted from the ceramic composite for light conversion differs depending on the surface condition. Therefore, the light extraction efficiency is high and the light emission is strong, and the light extraction efficiency is poor. The light distribution of the light emitting device can be controlled by combining with a portion having weak emission. In FIG. 1, 3 is a lead wire, 4 is a lead electrode, and 5 is a fixing member.

  The ceramic composite for light conversion of the present invention is characterized by having a portion having a high light extraction efficiency and a portion having a low light extraction efficiency due to the different surface texture. In the present invention, the surface texture refers to a fine shape or fine structure of the surface that changes the light emission rate, such as surface roughness and surface irregularities. When the surface is a mirror surface, light that is going to exit through the mirror surface from the inside of the composite ceramic with a high refractive index is incident on the mirror surface at a critical angle or more determined by the refractive index of the composite ceramic and the external refractive index. Total reflection, but if the surface is roughened or surface irregularities exist, the light that faces the surface is an angle greater than the critical angle with respect to the virtual mirror surface (the virtual surface that is considered to be a mirror surface ignoring the rough surface and irregularities) Can be incident locally at less than the critical angle due to the texture of the surface, and as a result, the light emission rate from the composite ceramics is the surface texture (large surface roughness, large uneven step, etc. ) Was found to increase in response to

  The composite ceramic of the present invention has a part having a different surface texture. The purpose is to change the light emission rate and change the orientation depending on the part. In the light-emitting device of the present invention, the portion where the surface texture of the composite ceramics is different is not limited, but can provide a difference of at least 2% in the light emission rate from the light-emitting element. Here, the light output rate is a comparison of the output rate in the same area. The difference is preferably at least 3%, more preferably at least 5%. In some cases, it is possible to make a difference of 10% or more.

  In the present invention, the part having a different surface texture of the composite ceramic has, for example, a different surface roughness, preferably an arithmetic average surface roughness (Ra) of at least 0.1 μm, more preferably 0.3 μm or more, and even 0. .5 μm or more, further 0.7 μm or more, particularly 1.0 μm or more. Other than surface roughness, as surface texture that changes the light extraction efficiency, unevenness can be formed on the surface, where unevenness includes, for example, unevenness formed by patterning using photolithography, etc. Concavities and convexities can be raised by providing a level difference for each type of oxide phase forming the ceramic composite for light conversion more simply. In the case of the latter unevenness, the height difference of the unevenness differs depending on the part, and preferably the difference in height difference is 0.5 μm, more preferably 1 μm, and further 3 μm or more. In the case where a step is provided for each type of oxide phase forming the ceramic composite, the size of the unevenness is not limited because it is the size of each oxide phase, but is typically about 1 to 20 μm. When the unevenness is formed by patterning using photolithography or the like, the dimensions can be the same, but in this case, it may be as small as 1 μm or less.

  For example, when it is desired to extract light upward in FIG. 1, the upper surface (top surface) 2 b is roughened, and the other surface 2 c and the like are mirror-finished to increase the emission intensity from the upper surface 2 b. By reducing the light emission intensity from the surfaces 2c, 2d, etc., the light emission efficiency in the upward direction as a whole can be increased.

  The portion that changes the surface texture (for example, surface roughness) of the portion that emits light of the ceramic composite for light conversion of the present invention does not have to be a single surface unit, and the surface texture can be changed depending on the portion in one surface. it can. For example, the central region of the upper surface (top surface) 2b in FIG. 1 can be roughened and the surrounding region surrounding the central region can be a mirror surface. Alternatively, the surface texture (surface roughness) may be changed to a spotted pattern.

  Furthermore, the surface texture of the portion that changes the surface texture of the portion that emits and emits light of the ceramic composite for light conversion of the present invention does not need to be constant. The surface texture of one surface may change gradually, and the light emission efficiency may change between a certain part of the surface and another part. In particular, referring to FIG. 2, light L enters the light emitting surface 20b of the light scatterer 20 for the backlight from the lateral direction 20A toward the opposite direction 20B, and is guided through the light scatterer 20 to emit light. When light is emitted (emitted) from the surface 20b to the liquid crystal layer or the like, the surface texture (for example, surface roughness) of the light emitting surface 20b gradually increases from the side surface 20A toward the opposite side surface 20B. Even when the light intensity becomes weaker as the light travels, the light emission (emission) intensity of the light emitting surface 20b can be made uniform.

  The light extraction efficiency is relative to the light distribution, so it is difficult to define the absolute value. The ceramic composite for light conversion has a refractive index higher than that of air. When light travels from a material having a high refractive index to a material having a low refractive index, the light is transmitted (refracted), reflected, and scattered at the interface. A surface texture with good light extraction efficiency is a case where transmission / scattering is dominant, for example, a surface with unevenness, a surface with a rough surface, and the like. A surface texture with poor light extraction efficiency is a case where reflection is dominant, for example, a mirror surface or the like.

  The ceramic composite for light conversion according to the present invention is characterized by having a portion with high light extraction efficiency and a portion with low light extraction efficiency. Typically, the surface roughness can be made different depending on the part, but other than the surface roughness, as a surface texture that changes the light extraction efficiency, for example, it is possible to form unevenness on the surface first. Stated.

The oxide phase constituting the ceramic composite for light conversion varies depending on the composition component and the production conditions of the solidified body and is not particularly limited. However, when the composition component contains at least Y element, Al element and Ce element, Al ₂ O ₃ (sapphire) phase, (Y, Ce) ₃ Al ₅ O ₁₂ phase, and the like, and at least two such oxide phases are included. At least two phases of the respective oxide phases have a structure in which they are continuously and three-dimensionally entangled with each other. Some oxide phases may be present in a granular form in an intertwined structure formed by other oxide phases. In any case, there is no boundary layer such as amorphous at the boundary between the phases, and the oxide phases are in direct contact with each other. For this reason, there is little loss of light in the ceramic composite for light conversion, and the light transmittance is also high.

The crystal phase that emits fluorescence also varies depending on the composition components and the production conditions of the solidified body and is not particularly limited. However, when the composition components include at least Y element, Al element, and Ce element, the oxide phase (Y, Ce) ₃ Examples thereof include an Al ₅ O ₁₂ phase, and at least one crystal phase that emits such fluorescence is included. These oxide phases including a crystalline phase that emits fluorescence take a structure that is continuously and three-dimensionally entangled with each other. As a whole, each oxide phase is uniformly distributed in the ceramic composite for light conversion. And uniform fluorescence with no bias.

The combination of the Al ₂ O ₃ phase and the (Y, Ce) ₃ Al ₅ O ₁₂ phase can easily obtain a structure in which both are continuously and three-dimensionally entangled with each other. The (Y, Ce) ₃ Al ₅ O ₁₂ phase emits fluorescence having a peak wavelength of 530 to 560 nm with excitation light of 400 to 520 nm, and is therefore suitable as a light conversion member for a white light emitting device. Therefore, it is preferable that at least a Y element, an Al element, and a Ce element are included as a composition component. In addition, when a Gd element is included, a (Y, Gd, Ce) ₃ Al ₅ O ₁₂ phase is generated as a phosphor phase, and fluorescence having a longer peak wavelength of 540 to 580 nm can be emitted.

  The solidified body constituting the ceramic composite for light conversion of the present invention is produced by solidifying a raw material oxide after melting. For example, it is possible to obtain a solidified body by a simple method of cooling and condensing a melt charged in a crucible held at a predetermined temperature while controlling the cooling temperature, but the most preferable one is produced by a unidirectional solidification method. It is. This is because the crystal phase contained by the unidirectional solidification grows continuously in a single crystal state, and the attenuation of light in the member decreases.

  The solidified body composing the ceramic composite for light conversion of the present invention has previously been disclosed in Japanese Patent Application Laid-Open Nos. Hei 7-149597 and Hei Hei, except that at least one oxide phase is a crystal phase that emits fluorescence. JP-A-7-187893, JP-A-8-81257, JP-A-8-253389, JP-A-8-253390, JP-A-9-67194, and corresponding US applications (US Pat. 569,547, 5,484,752, and 5,902,963), etc., and the production disclosed in these applications (patents). It can be manufactured by the method. The disclosures of these applications or patents are hereby incorporated by reference.

  A white light-emitting device that is an embodiment of the light-emitting device of the present invention includes a light-emitting element that emits light having a peak at a wavelength of 400 nm to 520 nm and the light conversion that emits fluorescence having a peak wavelength of 530 to 580 nm by light emitted from the light-emitting element. It consists of ceramic composites. The light from the light emitting element is incident on the ceramic composite for light conversion that has been adjusted in the fluorescence peak wavelength so that white color is obtained according to the wavelength. Fluorescence from the crystal phase that emits fluorescence excited by it and incident light that has passed through the crystal phase that does not emit fluorescence are mixed homogeneously by a structure in which the oxide phase is continuously and three-dimensionally intertwined. As a result, white light with small color unevenness can be obtained.

  The color tone of the light emitting device of the present invention can be easily controlled by the thickness of the ceramic composite for light conversion.

  The ceramic composite for light conversion used in the light emitting device of the present invention is produced in an appropriate shape and surface state such as a plate shape by a processing method such as cutting, grinding, polishing, and etching. This ceramic composite for light conversion can be used alone as a member, does not require an encapsulating resin, and is not deteriorated by heat or light, so it can be used in combination with high-power purple-blue light emitting elements. Thus, the output of the light emitting device can be increased.

  Examples of the light-emitting element used in the light-emitting device of the present invention include a light-emitting diode element and an element that generates laser light. However, the light-emitting diode element is preferable because it is small and inexpensive.

  According to the present invention, it is possible to easily control the light distribution of the light emitting device without adding any special parts. In addition, a light-emitting device can be formed without using a resin that is weak against heat and light. Therefore, it is possible to provide a white light emitting device that has anisotropic light distribution and is extremely suitable for high output without deterioration due to heat or light at low cost.

  Hereinafter, the present invention will be described in more detail with specific examples.

Example 1
α-Al ₂ O ₃ powder (purity 99.99%) is 0.82 mol in terms of AlO _3/2 , Y ₂ O ₃ powder (purity 99.9%) is 0.175 mol in terms of YO _3/2 , CeO ₂ powder (purity 99.9%) was weighed to 0.005 mol. These powders were wet mixed in ethanol by a ball mill for 16 hours, and then ethanol was removed using an evaporator to obtain a raw material powder. The raw material powder was pre-melted in a vacuum furnace and used as a raw material for unidirectional solidification.

Next, this raw material was directly charged into a molybdenum crucible and set in a unidirectional solidification apparatus, and the raw material was melted under a pressure of 1.33 × 10 ⁻³ Pa (10 ⁻⁵ Torr). Next, in the same atmosphere, the crucible is lowered at a speed of 20 mm / hour, and three oxide phases of Al ₂ O ₃ (sapphire) phase, (Y, Ce) ₃ Al ₅ O ₁₂ phase, and CeAl ₁₁ O ₁₈ phase are used. A solidified body was obtained.

FIG. 3 shows a cross-sectional structure perpendicular to the solidification direction of the solidified body. The black part of A is the Al ₂ O ₃ (sapphire) phase, the white part of B is the (Y, Ce) ₃ Al ₅ O ₁₂ phase, and the slightly gray part of C is the CeAl ₁₁ O ₁₈ phase. It can be seen that each oxide phase has a structure that is continuously and three-dimensionally entangled with each other. The structure is composed of a portion having a fine size and a slightly larger portion surrounding the portion, but it can be seen macroscopically that the (Y, Ce) ₃ Al ₅ O ₁₂ phase is uniformly distributed. For this reason, uniform fluorescence can be obtained.

  A disk-shaped sample of φ16 mm × 0.2 mm was cut out from the obtained solidified body, and the fluorescence characteristics were evaluated with a solid quantum efficiency measuring apparatus manufactured by JASCO Corporation. Correction was performed using a sub-standard light source to determine the true spectrum. The fluorescence spectrum is shown in FIG. A broad fluorescence spectrum having a peak wavelength at 547 nm was obtained by excitation light having a wavelength of 460 nm.

  A cube of 2 mm × 2 mm × 2 mm is cut out from the obtained solidified body, and among the six surfaces, two opposed surfaces are rough surfaces with a surface roughness Ra = 1.5 μm, and the remaining four surfaces are surface roughness Ra. A ceramic composite for light conversion having a mirror surface of 0.03 μm and a different surface state was produced. The obtained ceramic composite for light conversion and a light emitting element having a wavelength of 463 nm were arranged as shown in FIG. 5 to obtain a light emitting device. That is, the bottom surface 2a of the light conversion ceramic composite 2 is opposed to the light emitting element 1, the bottom of the light conversion ceramic composite 2 is fixed by the fixing member 5, and the top surface 2b is fixed in the light traveling direction ( (0 ° direction), side surfaces 2c, 2d, 2e, and the like were defined as light emitting surfaces (light emitting surfaces) perpendicular to the light traveling direction (90 °). At this time, the upper surface of the ceramic composite for light conversion was a surface with Ra = 1.5 μm, and the side surface was a surface with Ra = 0.03 μm. The light intensity at this time was measured in the 0 ° direction (upper surface direction) and 90 ° direction (side surface direction). When the light intensity in the 0 ° direction of the light emitting device using the ceramic composite for light conversion in which all of the six surfaces having the same shape and the surface roughness Ra = 1.5 μm are rough surfaces, which will be described later, is 1.0, this embodiment is implemented. The light intensity in the example is 1.2 in the 0 ° direction and 0.8 in the 90 ° direction, and it can be seen that light distribution with suppressed light emission to the side surface is obtained.

(Comparative Example 1)
From the solidified body produced by the same method as in Example 1, a ceramic composite for light conversion having a 2 mm × 2 mm × 2 mm cube with all surfaces having a surface roughness Ra = 1.5 μm was produced. A light emitting device similar to that in Example 1 was constructed, and the light intensity was measured in the 0 ° direction (upper surface direction) and 90 ° direction (side surface direction). The obtained light intensity is 1.0 in both the 0 ° direction and the 90 ° direction, indicating that the light distribution has no anisotropy.

(Examples 2 and 3)
A rectangular parallelepiped of 2 mm × 2 mm × 0.2 mm is cut out from the solidified body obtained in Example 1, and among the six surfaces, two opposing main surfaces (2 mm × 2 mm surfaces) are used as mirror surfaces, and the remaining four side surfaces are formed. The ceramic composite for light conversion of Example 2 having a rough surface with a surface roughness Ra = 1.5 μm, and the light conversion of Example 3 having a rough surface with a surface roughness Ra = 1.5 μm on all six surfaces. A ceramic composite was prepared. In these ceramic composites for light conversion, the lower half of the main surface was masked with a light-impermeable material as shown in FIG.

  And as shown in FIG.6 and FIG.7, the light of wavelength 463nm was entered from the lower surface of the rectangular parallelepiped, and the radiation state was observed. FIG. 7 is an observation photograph thereof. In FIG. 7A, the main surface of Example 2 is a mirror surface, and in FIG. 7B, the main surface of Example 3 is a rough surface. The light emitted in the case of the rough surface in FIG. 7B is brighter (the emission intensity is higher) than the mirror surface in FIG. In both of FIGS. 7A and 7B, the emission intensity is high at a portion close to the mask (portion near the incident surface), and the emission intensity decreases as the distance from the mask increases. It is observed that the light emission intensity of the top surface (upper part of the figure) opposite to the light incident surface is higher than the corresponding light emission intensity of FIG. In FIG. 7 (b), more light is emitted on the main surface, whereas in FIG. 7 (a), radiation on the main surface is increased as a result of suppression of radiation on the main surface. is there.

Example 4
A cube of 2 mm × 2 mm × 2 mm was cut out from the solidified body produced by the same method as in Example 1, and among the six surfaces, the two opposing surfaces had a checkered pattern with an uneven height difference of 3.5 μm and a width of 2 μm. Ceramic composites for light conversion having different surface states, in which the uneven surface and the remaining four surfaces are surfaces having a height difference of 0.1 μm, were produced. The checkered uneven surface was formed by pattern etching using photolithography. A light emitting device similar to that of Example 1 was constructed, and the upper surface of the ceramic composite for light conversion was an uneven surface with a height difference of 3.5 μm, and the side surface was a surface with a height difference of 0.1 μm. The light intensity at this time was measured in the 0 ° direction (upper surface direction) and 90 ° direction (side surface direction). Assuming that the light intensity in the 0 ° direction of the light emitting device of Comparative Example 1 is 1.0, the light intensity of this example is 1.15 in the 0 ° direction and 0.8 in the 90 ° direction. Similarly, it can be seen that light distribution in which light emission to the side surface is suppressed is obtained.

(Example 5)
A sample having a plate shape of 2 mm × 2 mm × 0.15 mm and a mirror surface with a surface roughness of 2 mm × 2 mm Ra = 0.04 μm was prepared from the solidified body obtained in Example 1, and sulfuric acid: phosphoric acid A heat treatment was performed at 200 ° C. for 1 h in a mixed acid of 1: 1 (volume ratio) to obtain a ceramic composite for light conversion whose surface is an uneven surface having a different height for each oxide phase. A cross section of the surface of the obtained ceramic composite for light conversion is shown in FIG. The black part is the Al ₂ O ₃ (sapphire) phase, the white part is the (Y, Ce) ₃ Al ₅ O ₁₂ phase, and the (Y, Ce) ₃ Al ₅ O ₁₂ phase is about 7 μm lower than the Al ₂ O ₃ phase. An uneven surface is formed.

Excitation light having a wavelength of 463 nm was incident on the obtained ceramic composite for light conversion, and the light emitted on the opposite side was collected using an integrating sphere, and the integrated value (total radiant flux) of all the emitted light was obtained. . The total radiant flux combining the transmitted excitation light and fluorescence is 109 in Example 5 when the comparative example with the same thickness and no irregularities on the surface is 100, and the surface of the ceramic composite for light conversion has a height for each oxide phase. It can be seen that by making the concavo-convex surfaces having different values, more light can be extracted and the light extraction efficiency is excellent.
Therefore, by making such a concavo-convex surface as a specific emission surface, it is possible to achieve a higher light emission rate at the specific emission surface than at other emission surfaces.

It is typical sectional drawing which shows one Embodiment of the light-emitting device of this invention. It is typical sectional drawing which shows another embodiment which applies the light-emitting device of this invention to backlights, such as a liquid crystal. It is a microscope picture of Example 1 which shows an example of the structure | tissue structure of the ceramic composite for light conversion of this invention. It is a fluorescence spectrum figure of Example 1 which shows an example of the fluorescence characteristic of the ceramic composite for light conversion of this invention. FIG. 3 is a schematic cross-sectional view of a light emitting device created for evaluating Example 1. It is a schematic diagram explaining the mode of experiment of Example 2,3. 4 is a photograph showing light emission states of Examples 2 and 3. FIG. 6 is a photomicrograph showing a cross section of the surface of the ceramic composite for light conversion obtained in Example 5.

Explanation of symbols

1 Light-emitting element (light-emitting diode element)
2 Ceramic composite for light conversion 2a Bottom surface of light-emitting ceramic composite (light emitting element facing surface)
2b Top surface of ceramic composite for light conversion 2c, 2d, 2e Side surface of ceramic composite for light conversion 3 Lead wire 4 Lead electrode 5 Fixing member

Claims (9)

In a light emitting device comprising a light emitting element and a ceramic composite for light conversion, the ceramic composite for light conversion has a structure in which at least two oxide phases are continuously and three-dimensionally entangled with each other, At least one of the oxide phases is composed of a solidified body that is a crystal phase that emits fluorescence, and the ceramic composite for light conversion is other than the light incident surface, the first light emitting surface, and the first light emitting surface. The first light emitting surface and the second light emitting surface have different surface textures, and the arithmetic average surface roughness ( A light emitting device characterized in that the difference in Ra) is 0.1 μm or more, and the light emission efficiency of the first light emission surface and the second light emission surface is different by 2% or more.   The light emitting device according to claim 1, wherein the surface texture is surface unevenness, and the uneven step is different by 0.5 μm or more. The light emitting device according to claim 2 , wherein the surface irregularities are irregularities for each oxide phase constituting the ceramic composite. The light emitting device according to any one of claims 1 to 3, wherein the first light emitting surface is opposed to the light incident surface. Characterized in that it comprises a portion in which the surface texture of the light emitting surface varies progressively, the light emitting device according to any one of claims 1-4. The light emitting device is a backlight, and the ceramic composite for light conversion has a plate shape having a main surface, and light is incident from the light emitting element on the side surface of the ceramic composite for light conversion from the lateral direction. The backlight is emitted from the main surface of the ceramic composite plate, and the surface texture gradually changes as the distance from the light incident site increases in the main surface from which the light is emitted from the ceramic composite for light conversion. The light emitting device according to any one of claims 1 to 3 and 5, characterized in that the amount of emitted light is equalized. The light conversion ceramic composites, at least Y element as a composition component, characterized in that it comprises Al element and Ce element, light emitting device according to any one of claims 1-6. Wherein the light emitting element is a light emitting diode, light-emitting device according to any one of claims 1-7. Fluoresces said light conversion ceramic composites having a peak wavelength 530～580Nm, the light emitting device is characterized in that it emits light having a peak at a wavelength of 400 nm to 520 nm, any one of the claims 1-8 The light emitting device according to item.