JP6131109B2 - Light emitting device and display device - Google Patents

Description

  The present invention relates to a light emitting device, and more particularly to a light emitting device using a phosphor that is excited by receiving light emitted from a light source.

  A light emitting diode (LED) element has excellent characteristics such as low power consumption, long product life, and low environmental load. A light-emitting device using a phosphor that emits fluorescence in response to light emitted from an LED element emits a combination of light emitted from the LED element and light emitted from the phosphor, and thereby emits light from the original LED element. Various different lights (including white light) can be emitted.

  When utilizing the light emitted from the LED element, not only the light but also heat is emitted from the LED element. Depending on the type of phosphor, the quantum efficiency decreases, that is, the brightness decreases due to the heat generated by the LED element. In particular, nanocrystalline phosphors have high emission intensity and excellent color rendering and color reproducibility, but their heat-resistant temperature is lower than conventional phosphors, and their performance is likely to deteriorate due to the influence of heat.

  For example, as shown in FIG. 8A, a technique is known that uses a resin 104 a containing a phosphor that emits desired fluorescence in a package 102 equipped with an LED element 101. In this case, the resin 104a containing the phosphor is greatly affected by the heat generated in the LED element 101.

  Therefore, as shown in FIG. 8B, a remote phosphor in which the phosphor sheet 104 and the LED element 101 are separated from each other so as not to directly affect the phosphor sheet 104 due to the heat generated by the LED element 101. Type white LEDs have been proposed. As described above, an example of using the phosphor as the phosphor sheet 104 is a light emitting diode device described in Patent Document 1. In the light emitting diode device described in Patent Document 1, the phosphor sheet is installed separately from the LED element, and the influence of the phosphor sheet on the heat generated by the LED element is reduced.

  However, when the structure shown in FIG. 8B is combined with the light guide plate 103 shown in FIG. 8C, the fluorescence from the phosphor sheet 104 receiving the excitation light emitted from the LED element 101 is omnidirectional. This causes a problem that most of the fluorescence Em does not enter the light guide plate 103. Thus, for example, as shown in FIG. 8C, it is conceivable to reduce the loss of fluorescence emitted from the phosphor sheet 104 by configuring the light guide plate 103 and the phosphor sheet to contact each other. ing.

JP 2007-0667204 (March 15, 2007) JP 2008-047851 A (released February 28, 2008)

  However, as shown in FIG. 8C, there still remains a problem that most of the fluorescence Em emitted from the phosphor sheet 104 does not enter the light guide plate 103.

  The present invention has been made to solve the above-described problem, and an object of the present invention is to provide a light-emitting device and a display device that can reduce the loss of light when light from the light-emitting portion enters the light guide plate. Is to provide.

In order to solve the above problems, a light-emitting device according to one embodiment of the present invention includes a light-emitting portion that includes a phosphor that emits fluorescence in response to excitation light emitted from an excitation light source;
A light guide plate that is provided farther from the excitation light source than the light emitting unit and guides light including fluorescence from the light emitting unit;
Light emitted from the light emitting unit, provided along the light incident surface that is the surface on which the excitation light is incident in the light emitting unit, and having a light transmitting unit that transmits the excitation light on the light incident surface. A light utilization unit that scatters or reflects a part of light leaking from the light incident surface of the light emitting unit to the excitation light source side and enters the light guide plate.

Further, a light-emitting device according to one embodiment of the present invention includes a light-emitting portion including a phosphor that emits fluorescence in response to excitation light emitted from an excitation light source;
A light guide plate that is provided farther from the excitation light source than the light emitting unit and guides light including fluorescence from the light emitting unit;
Of the light emitted from the light emitting part, the light emitting part has a light transmitting part that is provided along a light incident surface that is a surface on which the excitation light is incident, and that transmits the excitation light on the light incident surface. A light utilization unit that includes a phosphor that emits fluorescence by receiving a part of light leaking from the light incident surface of the light emitting unit to the excitation light source side, and that causes the fluorescence to be incident on the light guide plate. Yes.

  According to one embodiment of the present invention, there is an effect that it is possible to reduce light loss when light from the light emitting unit enters the light guide plate.

It is sectional drawing which shows an example of the principal part structure of the light-emitting device which concerns on Embodiment 1 of this invention. It is a disassembled perspective view which shows the structural example of the light-emitting device which concerns on embodiment of this invention. It is sectional drawing which shows an example of the principal part structure of the light-emitting device which concerns on Embodiment 1 of this invention. It is sectional drawing which shows an example of the principal part structure of the light-emitting device which concerns on Embodiment 2 of this invention. It is a figure for demonstrating the fluorescence loss which may arise in the light-emitting device which concerns on Embodiment 1 of this invention. It is sectional drawing which shows an example of the principal part structure of the light-emitting device which concerns on Embodiment 3 of this invention. It is sectional drawing which shows an example of the principal part structure of the light-emitting device which concerns on Embodiment 4 of this invention. It is sectional drawing which shows the example of schematic structure of the conventional light-emitting device, and the example of schematic structure of the conventional light-emitting device, (a) is a light-emitting device using an LED element, (b) and (c) are LED elements. It is a figure which shows the modification of the used light-emitting device. It is explanatory drawing explaining the fluorescence loss which may arise in the fluorescence which fluorescent substance emits.

  Hereinafter, a schematic configuration of the light emitting device 10 according to the embodiment of the present invention will be described in detail with reference to FIG. In addition, in order to explain the structure of the light-emitting device 10 of the present invention, the shape, size, and comparison of each structure shown in the drawings referred to below including FIG. 2 are simplified and illustrated. The actual embodiment is not accurately shown. In addition, for example, configurations such as wiring and electrodes for applying a voltage are not members closely related to the features of the present invention, and thus illustration and description thereof are omitted.

(Configuration of Light Emitting Device 10)
First, a schematic configuration of the light emitting device 10 will be described with reference to FIG. FIG. 2 is a perspective view showing a configuration example of the light emitting device 10 according to the embodiment of the present invention. The light emitting device 10 includes an LED element 1, a package 2, a light guide plate 3, a phosphor sheet 4, and a light utilization unit 5. In addition, here, although a description will be given by taking as an example a configuration in which the member containing the phosphor that emits light upon receiving the excitation light Ex is the phosphor sheet 4, it is not limited thereto, and the phosphor is contained. The member to be performed may have another shape.

  The LED element 1 is a light emitting element that functions as an excitation light source that emits excitation light Ex. The LED element 1 may be either one having one light emitting point per chip or one having a plurality of light emitting points per chip. The light emitting wavelength of the LED element 1 (excitation light source, blue light emitting element) is, for example, 450 nm (blue), but an LED having a wavelength in the blue region of 420 nm to 490 nm can be selected. Or the light emission wavelength of the LED element 1 should just be suitably selected according to the kind of nanoparticle fluorescent substance (after-mentioned), Therefore It is good also as a wavelength different from blue. In addition, the LED element 1 does not need to be plural and may be singular. Further, the LED element 1 may use another excitation light source such as a laser.

  The package 2 is made of polyphthalamide (PPA) resin having high reflectivity and good adhesion to the sealing resin, or ceramics such as alumina. The LED element 1 is loaded in the package 2. The package loaded with the LED element 1 can be arranged in the x-axis direction and the y-axis direction on the xy plane of FIG. In FIG. 2, only the packages 2 arranged in parallel with the x axis on the foremost side (the most negative side of the y axis) in the figure are shown for the sake of simplicity, and the others are omitted.

  The light guide plate 3 is used for an edge light type backlight of a liquid crystal display, and has a role of making the fluorescence emitted from the phosphor sheet 4 a uniform surface light source. The light guide plate 3 may take in the light emitted from the LED element 1 together with the fluorescence emitted from the phosphor sheet 4. The light guide plate 3 is made of an acrylic resin such as polymethyl methacrylate (PMMA).

  The phosphor sheet 4 emits light upon receiving excitation light Ex emitted from an excitation light source such as a laser or LED, and includes a phosphor that emits light upon receiving the excitation light Ex. Specifically, in the phosphor sheet 4, the phosphor is dispersed inside an acrylic resin as a sealing material. The ratio between the acrylic resin and the phosphor is preferably about 10: 1, but is not limited to this ratio. Further, the phosphor sheet 4 may be a product obtained by pressing and compacting a phosphor. The sealing material is not limited to acrylic resin, and may be silicone resin, so-called organic-inorganic hybrid glass, inorganic glass, or the like. That is, the sealing agent material may be anything as long as it is a transparent resin, glass or the like. An acrylic resin such as polylauryl methacrylate (PLMA) is more preferable as a material for sealing the nanocrystalline phosphor because the nanocrystalline phosphor is easily dispersed.

  Preferable examples of the nanocrystalline phosphor include binary nanocrystalline compound semiconductors composed of II-VI group compound semiconductors and III-V group compound semiconductors. Examples of the II-VI compound semiconductor include CdSe, ZnS, ZnSe, and the like. Examples of the III-V group compound semiconductor include InN, InP, GaN, and the like. Further, a ternary or quaternary compound in which a II-VI group compound or a III-V group compound is combined may be used. The nanocrystalline phosphor has a wavelength controllability of emitted fluorescence, and can be applied to a high color rendering illumination device, a backlight of a display device excellent in color reproducibility, and the like.

  Even if compound semiconductors with the same composition (for example, indium phosphide: InP) are used, the emission color can be changed by the quantum size effect by changing the particle size. One. For example, InP emits red light when the particle size is about 3 to 4 nm.

  Since the nanocrystalline phosphor is based on a semiconductor, it has a short fluorescence lifetime, and can also emit the excitation energy absorbed by the excitation light Ex as fluorescence quickly, and therefore has a feature that it is highly resistant to the high-power excitation light Ex. This is because the emission lifetime of the nanocrystalline phosphor is about 10 nanoseconds, which is five orders of magnitude smaller than that of a normal phosphor material having a rare earth as the emission center.

  As a result, high efficiency can be maintained with respect to strong excitation light Ex, and heat generation from the phosphor is reduced. Therefore, deterioration (discoloration or deformation) of the phosphor due to heat can be suppressed. Thereby, when using the light emitting element with a high light output as a light source, the lifetime reduction of a light-emitting device can be prevented.

  Thus, the phosphor sheet 4 is not limited to a specific type and can be appropriately selected. The phosphor sheet 4 may be fixed to the light guide plate 3 with an acrylic or epoxy adhesive. In addition, it is preferable to select an adhesive close to the refractive index of the light guide plate 3 and the phosphor sheet 4 as an adhesive for adhering the light guide plate 3 and the phosphor sheet 4. Adhesion using a material having a refractive index close to that of the refractive index can reduce the effects of light reflection and refraction at each of the boundaries of the light guide plate 3 / adhesive / phosphor sheet 4, thereby further improving the conductivity. Incidence efficiency of light incident on the optical plate can be improved.

  Another example of the phosphor sheet 4 is an oxynitride-based light emitting part in which blue, green and red phosphors are dispersed in a silicone resin. Here, as an example of an excitation light source that emits the excitation light Ex, a semiconductor light emitting element is a 450 nm (blue) LED (or a so-called “blue” LED having a peak wavelength in a wavelength range of 440 nm to 490 nm or less. Laser). When the phosphor sheet 4 is irradiated with the LED light, for example, white light is generated from the phosphor sheet 4. That is, it can be said that the phosphor sheet 4 is a wavelength conversion material. In this case, the phosphor sheet 4 is a yellow phosphor or a mixture of a green phosphor and a red phosphor. The yellow phosphor is a phosphor that emits light having a peak wavelength in a wavelength range of 560 nm to 590 nm. The green phosphor is a phosphor that emits light having a peak wavelength in a wavelength range of 510 nm or more and 560 nm or less. The red phosphor is a phosphor that emits light having a peak wavelength in a wavelength range of 600 nm to 680 nm. However, the wavelength of the light emitted from the semiconductor light emitting element may be appropriately selected according to the type of the phosphor sheet 4, and therefore may be a wavelength different from the wavelength of the so-called blue light.

The phosphor sheet 4 may be a so-called sialon phosphor. Sialon is a substance in which a part of silicon atoms of silicon nitride (Si ₃ N ₄ ) is replaced with aluminum atoms and a part of nitrogen atoms is replaced with oxygen atoms. The sialon phosphor can be made by dissolving alumina (Al ₂ O ₃ ), silica (SiO ₂ ), rare earth elements and the like in silicon nitride. The phosphor sheet 4 is a YAG yellow phosphor that emits yellow light when excited by blue light, or CaAlSiN ₃ : Eu fluorescence that emits light from orange to red when excited by blue light and has high emission intensity. Or a CASN red phosphor may be used.

  Alternatively, an excitation light source that oscillates 405 nm (blue-violet) laser light may be used. In this case, the phosphor sheet 4 is a yellow phosphor or a mixture of a green phosphor and a red phosphor. Or it is not restricted to the excitation light source which oscillates a 405 nm laser beam, For example, you may use the excitation light source which oscillates a 450 nm laser beam. That is, the wavelength of the laser beam is not limited to a specific wavelength.

  In the following, as shown in FIG. 2, the phosphor sheet 4 has a light incident surface and a light emitting surface that are parallel to the xy plane and face each other, and is a light emitting surface that is a surface farther from the LED element 1. A configuration in which the phosphor sheet 4 and the light guide plate 3 are in contact with each other will be described as an example.

  The light utilization unit 5 has at least a contact surface 5a between the phosphor sheet 4 and receives light which is light from the inside of the phosphor sheet 4 and does not enter the light guide plate 3, and a part of the light. Is incident on the light guide plate 3. That is, the light utilization unit 5 has a surface on which the excitation light Ex is incident on the phosphor sheet 4 out of the light emitted from the phosphor sheet 4, and is from a surface (light incident surface) in contact with the contact surface 5 a. This is a member for utilizing part of the emitted light as light incident on the light guide plate 3. FIG. 2 shows an example in which the light utilization unit 5 has a contact surface 5 a and a contact surface 5 b between the phosphor sheet 4.

  For example, the light utilization unit 5 may include a configuration having light scattering properties such as particles or bubbles that scatter light. Thereby, the light from the phosphor sheet 4 that is not incident on the light guide plate 3 is received and scattered, and a part of the light is incident on the light guide plate 3. In this case, it is desirable that the light utilization unit 5 is configured using PMMA or the same acrylic resin-based polylauryl methacrylate (PLMA). Since the influence of light reflection and refraction at the refractive index boundary with the material of the light guide plate 3 or the phosphor sheet 4 can be reduced as the material for the light utilization part 5, the light incident efficiency to the light guide plate is further improved. Can be made. The light emitting device 10 including the light utilization unit 5 having this configuration will be described in detail later as Embodiments 1 and 2.

  Or the light utilization part 5 may be comprised with reflective materials with high light reflectivity, such as aluminum and silver which permeate | transmit light. Accordingly, the light from the inside of the phosphor sheet 4 that is not incident on the light guide plate 3 may be received and reflected, and a part of the light may be incident on the light guide plate 3. The light emitting device 10 including the light utilization unit 5 having this configuration will be described in detail later as a second embodiment.

  Or the light utilization part 5 may be comprised including the fluorescent substance which receives the light emitted from the fluorescent substance sheet 4, and emits fluorescence. Thereby, the light that is from the inside of the phosphor sheet 4 and does not enter the light guide plate 3 becomes excitation light Ex for the phosphor included in the light utilization unit 5. As a result, fluorescence is emitted from the light utilization unit 5, and part of the fluorescence enters the light guide plate 3. The light emitting device 10 including the light utilization unit 5 having this configuration will be described in detail later as a fourth embodiment.

  In FIG. 2, in order to simplify the description, a contact surface that is in contact with a surface parallel to the xz plane of the phosphor sheet 4 is not illustrated, but the light utilization unit 5 includes the phosphor sheet 4 and the light guide plate 3. It is preferable to be configured to be in contact with all the surfaces of the other phosphor sheet 4 except the surface in contact with it. Thereby, the light utilization part 5 can receive efficiently the light which did not enter into the light-guide plate 3 among the fluorescence of all the directions emitted from the fluorescent substance sheet 4. FIG.

  In the light utilization unit 5, the excitation light Ex incident on the phosphor sheet 4 passes through the light utilization unit 5 at a place where the excitation light Ex emitted from the LED element 1 and incident on the phosphor sheet 4 passes. The light transmission part P is provided so that it may not. The light transmission part P may be a hole provided in the light utilization part 5. Alternatively, the light transmission part P may be provided as a region made of a resin or glass that is not a hole but has a light transmission property and does not reflect or scatter light.

(Embodiment 1)
FIG. 1 is a cross-sectional view of the light-emitting device 10 according to Embodiment 1 of the present invention as viewed in the direction of the arrows along the line AB shown in FIG. For convenience of explanation, members having the same functions as those described in the embodiment are given the same reference numerals, and descriptions thereof are omitted.

  In the present embodiment, the light utilization unit 5 scatters a part of the light from the phosphor sheet 4 that is not incident on the light guide plate 3, and changes the direction of the light, thereby causing the light from the phosphor sheet 4. Part of the light that does not enter the light guide plate 3 is utilized as light incident on the light guide plate 3.

  The light utilization unit 5 includes a light scatterer 51 having a refractive index different from that of the transparent member and causing scattering of incident light in a transparent member such as acrylic resin, silicone, or glass. The light scatterer 51 may be an air bubble formed by confining a solid particle having a size causing Mie scattering or a gas such as air in a transparent member. The Mie scattering is light scattering caused by particles larger than the wavelength of light, and solid particles having a size larger than the wavelength of fluorescence emitted from the phosphor sheet 4 or empty bubbles are converted into light scattering bodies 51. You may apply as That is, since the light utilization part 5 can be made by mixing the light scatterer 51 with transparent resin, this structure can be realized at low cost.

  When the phosphor sheet 4 and the light guide plate 3 are made of an acrylic resin, an acrylic resin is preferable as the material of the transparent member that constitutes the light utilization unit 5. This is because the refractive index difference at the interface between the light utilization part 5 and the phosphor sheet 4 and the interface between the light utilization part 5 and the light guide plate 3 can be reduced, and the light incident efficiency to the light guide plate is improved. It is because it can be made.

  Next, the function which the light utilization part 5 has is demonstrated using FIG. FIG. 3 is a cross-sectional view illustrating an example of a main configuration of the light-emitting device 10 according to Embodiment 1 of the present invention.

  Since the fluorescence Em from the phosphor sheet 4 that has received the excitation light Ex emitted from the LED element 1 is emitted in all directions, most of the fluorescence Em does not enter the light guide plate (see FIG. 7C). Therefore, as shown in FIG. 3, the light scatterer 51 included in the light utilization unit 5 receives and scatters the fluorescent Em from the phosphor sheet 4 that did not originally enter the light guide plate 3. By doing so, the direction of the fluorescence Em is changed. Thereby, a part of fluorescence Em which the light utilization part 5 received can be put in a light-guide plate.

  A light transmission part P is provided in a region through which the excitation light Ex emitted from the LED element 1 passes, and the light transmission part P is configured as a transparent resin or a hole that does not include the light scatterer 51. The reason for this is that if the light scatterer 51 is present in the light utilization part 5 where the excitation light Ex is incident, the excitation light Ex is scattered and interrupted by the light scatterer 51 before entering the phosphor sheet 4. This is because light that returns to the opposite direction to the light guide plate 3 (the negative direction of the z axis) increases.

  In addition, the light transmission part P was provided so that the excitation light Ex inject | emitted from the LED element 1 might reach | attain the fluorescent substance sheet 4, and was shown as a hole through which the excitation light Ex passes here. However, the present invention is not limited to this, and it may be configured so that the excitation light Ex emitted from the LED element 1 can enter the phosphor sheet 4. For example, when the light utilization part 5 is formed of a highly light-transmitting resin or glass, the density of the light scatterer 51 in the light transmissive part P is lowered or the light transmissive part P includes the light scatterer 51. What is necessary is just to comprise with no resin.

  The light utilization part 5 is prepared by first preparing a liquid resin (acrylic, silicone, etc.) in which the light scatterer 51 is mixed in advance, applying it to the phosphor sheet 4, and then ultraviolet light (UV light). Or by applying heat to the liquid resin to cure the applied liquid resin. Therefore, in order to prevent the liquid resin containing the light scatterer 51 from being applied to the portion corresponding to the light transmission part P, the surface of the phosphor sheet 4 corresponding to the light transmission part P can be protected. preferable.

  In order to further reduce the light loss due to reflection and refraction at the respective interfaces of the light guide plate / adhesive / phosphor sheet, and to further increase the light incident efficiency to the light guide plate, It is preferable that the phosphor sheet 4, the light utilization part 5, and the adhesive used for bonding them are configured using materials having refractive indexes close to each other.

[Embodiment 2]
The following describes the second embodiment of the present invention with reference to FIG. For convenience of explanation, members having the same functions as those described in the embodiment are given the same reference numerals, and descriptions thereof are omitted.

  In this embodiment, the light utilization part 5 is comprised, for example with the metal, and reflects the light from the fluorescent substance sheet 4. FIG. As a result, the light from the phosphor sheet 4 that is not incident on the light guide plate 3 is reflected, and a part of the light is incident on the light guide plate 3.

  FIG. 4 is a cross-sectional view illustrating an example of a main configuration of the light-emitting device 10 according to Embodiment 2 of the present invention.

  Since the fluorescence Em from the phosphor sheet 4 receiving the excitation light Ex emitted from the LED element 1 is emitted in all directions, most of the fluorescence Em does not enter the light guide plate 3 (see FIG. 8C).

  In this embodiment, the light utilization part 5 is formed of a material having high light reflectivity (reflecting material), and the fluorescence incident on the contact surfaces 5a and 5b (light reflecting parts, see FIG. 2) from the phosphor sheet 4. Reflects Em and changes the direction of fluorescence Em. Thereby, a part of the fluorescence Em received by the light utilization unit 5 can be made incident on the light guide plate 3 to utilize the fluorescence Em.

  Examples of suitable materials for the light utilization part 5 include metals such as aluminum and silver. Both aluminum and silver are known to reflect light having a wavelength corresponding to visible light from ultraviolet rays, and can reflect fluorescent Em emitted from the phosphor sheet 4 without waste. For example, aluminum has a reflectance of about 90% with respect to light in the wavelength region of 280 nm to 1000 nm, and silver has a reflectance of 98% with respect to light in the wavelength region of 450 nm to 700 nm. That is, the light utilization part 5 is a metal film, and the metal is preferably aluminum or silver.

  That is, the metal film of the light utilization unit 5 reflects and changes the direction of the fluorescence from the phosphor sheet 4 in a direction that is not originally incident on the light guide plate 3, whereby a part of the light is guided to the light guide plate. 3 can be made incident.

  Note that if the metal film is present at a position where the excitation light Ex from the LED element 1 is to enter the phosphor sheet 4, the excitation light Ex is incident on the phosphor sheet 4 because the metal film reflects the excitation light Ex. It is not possible to return to the LED element 1 side. Therefore, a light transmission part P that is a hole through which the excitation light Ex passes may be provided so that the excitation light Ex emitted from the LED element 1 reaches the phosphor sheet 4.

  As a method for producing the light utilization unit 5 according to the present embodiment, a film containing aluminum or silver is formed by resistance heating vapor deposition after masking a metal so that it is not vapor deposited in a region where the excitation light Ex is incident. Good.

[Embodiment 3]
The third embodiment of the present invention will be described below with reference to FIGS. For convenience of explanation, members having the same functions as those described in the embodiment are given the same reference numerals, and descriptions thereof are omitted.

  The phosphor has a feature that it easily absorbs light having a shorter wavelength than the fluorescence Em emitted by itself, and has a property of absorbing the excitation light Ex and emitting light having a wavelength longer than the wavelength of the excitation light Ex as fluorescence. The wavelength of the excitation light Ex that can excite the phosphor is shorter than the wavelength of the fluorescence emitted by the phosphor. That is, the phosphor is characterized in that it absorbs light having a shorter wavelength than the fluorescence emitted by itself and emits fluorescence.

  FIG. 9 is an explanatory diagram for explaining the fluorescence loss that occurs when the excitation light Ex emitted from the LED element 1 is received to emit fluorescence. Here, the LED element 1 is an LED element that emits blue light, and the phosphor sheet 4 includes a phosphor F1 that emits green fluorescence EmG and a phosphor F2 that emits red fluorescence EmR. explain. The excitation light Ex from the LED element 1 is light having a shorter wavelength than the fluorescence EmG emitted from the phosphor F1 and the fluorescence EmR emitted from the phosphor F2. In FIG. 9, the light quantity of each light is expressed by the line width of the arrow.

  As shown in FIG. 9A, the excitation light Ex emitted from the LED element 1 enters the phosphor sheet 4 and exits from the phosphor sheet 4 without hitting both the phosphor F1 and the phosphor F2. In this case, the amount of light emitted from the LED element 1 is blue light emitted from the phosphor sheet 4 with almost no attenuation while passing through the transparent member constituting the phosphor sheet 4.

  As shown in FIGS. 9B and 9C, upon receiving the excitation light Ex, the phosphor F1 emits fluorescence EmG, and the phosphor F2 emits fluorescence EmR. Not all the energy of the excitation light Ex absorbed by the phosphor is used as fluorescence. This is due to the fact that the quantum efficiency of the phosphors F1 and F2 is not 100%. Therefore, a part of the excitation light Ex is consumed as energy that is not used as fluorescence emitted from the phosphor. Furthermore, there is also a light loss (Stokes loss) associated with Stokes' Law that the wavelength of the fluorescence emitted by the phosphor is longer than the wavelength of the excitation light Ex received by the phosphor. This is one of the causes that the fluorescence EmG and EmR become fluorescence with a light amount smaller than the excitation light Ex received by the corresponding phosphor.

  Furthermore, inside the phosphor sheet 4, as shown in FIG. 9D, the phosphor Em2 emitted from the phosphor F1 that has received the excitation light Ex may be received by the phosphor F2 to emit fluorescence EmR. Conceivable. In this case, the fluorescence EmG emitted from the fluorescence F1 that has received the excitation light Ex is absorbed by the phosphor F2 before being emitted from the phosphor sheet 4, so that the fluorescence EmR having a light quantity less than that of the fluorescence EmG. Is emitted. That is, when the phosphor sheet 4 includes a plurality of types of phosphors, the probability that the fluorescence emitted from each phosphor, in particular, the fluorescence having a short wavelength, is absorbed by other types of phosphors increases. , The loss of fluorescence increases. On the other hand, although not shown here, the fluorescence EmR from the phosphor F2 is hardly absorbed by the phosphor F1.

  Next, the fluorescence loss considered when the phosphor sheet 4 of Embodiment 1 includes a plurality of types of phosphors will be described with reference to FIG. FIG. 5 is a diagram for explaining fluorescence loss that may occur in the light emitting device 10 according to the first embodiment.

  The phosphor that has received the excitation light Ex emits fluorescence Em in a wavelength region corresponding to each color at a location near the incident surface on which the excitation light Ex from the excitation light source of the phosphor sheet 4 is incident. In FIG. 5, the fluorescence from the phosphor that emits blue fluorescence is shown as fluorescence EmB, the fluorescence from the phosphor that emits green fluorescence is fluorescence EmG, and the fluorescence from the phosphor that emits red fluorescence is shown as fluorescence EmR. . Note that the fluorescence EmB is not limited to fluorescence emitted from the phosphor included in the phosphor sheet 4, and may be excitation light Ex that passes through the phosphor sheet 4.

  As described above, the fluorescence EmB can be absorbed by a phosphor that emits green fluorescence and a phosphor that emits red fluorescence, and the fluorescence EmG can be absorbed by a phosphor that emits red fluorescence. Therefore, among the fluorescence EmG, EmG, and EmR emitted from the phosphor sheet 4, the fluorescence EmB and EmG having a shorter wavelength may be reduced as compared with the fluorescence EmR. Since the fluorescence EmB may be the excitation light Ex, the emitted light can be increased to compensate for the decrease. On the other hand, the probability that the fluorescent EmG is absorbed inside the phosphor sheet 4 depends on the density of the phosphor contained in the phosphor sheet 4, and a plurality of types of phosphors are contained in the phosphor sheet 4. In this case, this fluorescence loss occurs.

  Therefore, in the present embodiment, as shown in FIG. 6, the phosphor sheet 4 is divided into, for example, a phosphor sheet 4 </ b> R (first light emitting unit) mainly including a phosphor that emits red fluorescence, and fluorescence that emits green fluorescence. The phosphor sheet 4G (second light emitting unit) mainly including the body is arranged so that the excitation light Ex is incident on the phosphor sheet 4R before the phosphor sheet 4G. That is, the phosphor sheet with the longer wavelength of emitted fluorescence is more LED element 1 than the other phosphor sheet so that the excitation light Ex is first incident on the phosphor sheet with the longer emission wavelength of the included phosphor. It is arranged near the position.

  According to this configuration, the fluorescence EmG emitted from the phosphor sheet 4G is incident on the light guide plate 3 without passing through the phosphor sheet 4R, so that the fluorescence loss generated in the fluorescence EmG and the fluorescence EmR incident on the light guide plate is reduced. . The fluorescent EmR passes through the fluorescent sheet 4G and enters the light guide plate 3, but the fluorescent sheet 4G does not absorb the fluorescent EmR. Therefore, the influence of the fluorescence loss of the fluorescence EmG incident on the light guide plate 3 is reduced, and the brightness of the phosphor sheet 4 is improved.

  As shown in FIG. 6, the light emitting device 10 according to the present embodiment includes a light utilization unit 5, and the light utilization unit 5 out of the light emitted from the phosphor sheet 4 </ b> R and the phosphor sheet 4 </ b> G. Light that is not incident on the light is scattered. Thereby, a part of the light is used as light incident on the light guide plate 3.

[Embodiment 4]
The following describes the fourth embodiment of the present invention with reference to FIG. For convenience of explanation, members having the same functions as those described in the embodiment are given the same reference numerals, and descriptions thereof are omitted.

  The light utilization unit 5 of the light emitting device 10 according to the present embodiment is disposed at a position closer to the LED element 1 than the phosphor sheet, and the light utilization unit 5 receives, for example, the fluorescence EmG from the phosphor sheet 4. And a phosphor that emits fluorescence EmR having a wavelength longer than that of fluorescence EmG.

  According to this structure, the light utilization part 5 excites the fluorescent substance which the light utilization part 5 contains fluorescence EmG which does not enter into the light-guide plate 3 among the lights emitted from the phosphor sheet 4R and the phosphor sheet 4G. Use as excitation light Ex. In response to the fluorescence EmG, the light utilization unit 5 emits fluorescence EmR. In this way, part of the fluorescence EmR emitted from the light utilization unit 5 is utilized as light incident on the light guide plate 3.

  In FIG. 7, the light transmission part P, which is a hole through which the excitation light Ex emitted from the LED element 1 passes, is not limited to this, but the excitation light Ex emitted from the LED element 1 is fluorescent. What is necessary is just to be comprised so that it can inject into the body sheet | seat 4. FIG. For example, when the light utilization part 5 is formed of a highly light-transmitting resin or glass or the like, a resin having a low density of the phosphor of the light utilization part 5 in the light transmission part P or a phosphor is used for the light transmission part P. What is necessary is just to comprise with resin which does not contain. Alternatively, as long as the excitation light Ex can enter the phosphor sheet 4 with sufficient light, the light transmission portion P may not be provided specially.

[Summary]
A light emitting device 10 according to aspect 1 of the present invention includes a light emitting unit (phosphor sheet 4) including a phosphor that emits fluorescence Em in response to excitation light Ex emitted from an excitation light source (LED element 1).
A light guide plate 3 that is provided farther from the excitation light source than the light emitting unit and guides light including fluorescence from the light emitting unit;
The light emitting portion is provided along a light incident surface, which is a surface on which the excitation light is incident, and has a light transmission portion P that transmits the excitation light on the light incident surface, and is emitted from the light emitting portion. A light utilization unit 5 that scatters or reflects a part of light leaking from the light incident surface of the light emitting unit to the excitation light source side of the light and enters the light guide plate.

  According to said structure, the light utilization part has a light transmission part which permeate | transmits excitation light, and the excitation light which permeate | transmitted the light transmission part reaches a light emission part. Scattering a part of the light leaked from the light incident surface, which is the surface on which the excitation light is incident on the light emitting portion, to the excitation light source side among the light (primary light) emitted from the light emitting portion that has received the excitation light The incident or reflected light (secondary light) is made incident on the light guide plate. Thereby, the light-emitting device according to the present invention can cause the light including fluorescence directed from the light emitting unit to the excitation light source and including the fluorescence not entering the light guide plate to enter the light guide plate. Therefore, it is possible to reduce light loss when light from the light emitting unit enters the light guide plate.

  In the light emitting device 10 according to aspect 2 of the present invention, in the above aspect 1, the light utilization part may include a light scatterer 51 that scatters light from the light emitting part.

  According to said structure, a light-scattering body scatters a part of light which is light from a light emission part, and does not enter into a light-guide plate, and changes the direction of this light. Thereby, even if the light utilization part is made of a transparent member, the light containing the fluorescence from the light emitting part and not including the fluorescence that enters the light guide plate is utilized as the light incident on the light guide plate. It is possible.

  The light emitting device 10 according to aspect 3 of the present invention may be configured such that, in the above aspect 2, the light scatterer is a particle or air bubble sealed inside.

  According to the above configuration, the fluorescence from the light emitting part is scattered by the particles or air bubbles to change the direction of the fluorescence. Thereby, a light utilization part can be implement | achieved at low cost.

  In the light emitting device 10 according to aspect 4 of the present invention, in the above aspect 1, the light utilization part includes a light reflecting part (contact surfaces 5a and 5b) configured by a reflective material that reflects light from the light emitting part. It may be a configuration.

  According to said structure, the light utilization part is comprised with the reflecting material, and reflects the light from a light emission part. Thereby, it is possible to reflect the light including the fluorescence from the light emitting unit and including the fluorescence that does not enter the light guide plate, and to make a part of the light enter the light guide plate.

  In the light emitting device 10 according to the fifth aspect of the present invention, in the fourth aspect, the light reflecting portion may include aluminum or silver.

  Both aluminum and silver are metals having the property of reflecting light with high efficiency. According to said structure, the optical loss produced between the light which injected into the light reflection part and the reflected light can be reduced.

A light emitting device 10 according to an aspect 6 of the present invention is the light emitting device 10 according to any one of the above aspects 1 to 5, wherein the light emitting unit includes a first light emitting unit and a second light emitting unit.
The first light emitting unit emits fluorescence in response to excitation light emitted from the excitation light source,
The second light emitting unit receives the excitation light emitted from the excitation light source, and emits fluorescence having a wavelength corresponding to a color different from that of the first light emitting unit,
Of the first light-emitting part and the second light-emitting part, the light-emitting part (phosphor sheet 4R) having the longer emission wavelength is closer to the excitation light source than the other light-emitting part (phosphor sheet 4G). The structure arrange | positioned may be sufficient.

  Shorter-wavelength fluorescence has the property of being absorbed in the light-emitting portion that emits longer-wavelength fluorescence. According to said structure, a 1st light emission part and a 2nd light emission part emit the fluorescence of the wavelength corresponding to a mutually different color in response to excitation light, and the light emission part with a longer wavelength of the emitted fluorescence is the other light emission. It is arranged at a position closer to the excitation light source than the part. Thereby, before entering the light guide plate, the fluorescence loss caused by the absorption of the shorter wavelength fluorescence in the other light emitting part can be reduced, so that more fluorescence is emitted from the light emitting part. And a light utilization part can utilize the light containing the fluorescence which does not enter into a light guide plate as light which injects into a light guide plate.

The light-emitting device 10 according to the seventh aspect of the present invention is the light-emitting device 10 according to the sixth aspect, wherein the excitation light source is a blue light-emitting element that emits light in a wavelength region corresponding to blue.
The first light emitting unit (phosphor sheet 4R) receives light from the blue light emitting element and emits red fluorescence,
The second light emitting unit (phosphor sheet 4G) may receive green light and emit green fluorescence.

  According to said structure, a 2nd light emission part receives the light of the said blue light emitting element, emits green fluorescence, and receives the light which does not inject into a light-guide plate among the green fluorescence from a 2nd light emission part. The first light emitting unit emits red fluorescence. Thereby, the green fluorescence from a 2nd light emission part can reduce the fluorescence loss which a 2nd light emission part produces. It can be utilized as light incident on the light guide plate.

A light-emitting device 10 according to an aspect 8 of the present invention includes a light-emitting unit (phosphor sheet 4) including a phosphor that receives excitation light Ex emitted from an excitation light source (LED element 1) and emits fluorescence Em;
A light guide plate 3 that is provided farther from the excitation light source than the light emitting unit and guides light including fluorescence from the light emitting unit;
The light emitting portion is provided along a light incident surface that is a surface on which the excitation light is incident, and has a light transmission portion P that transmits the excitation light on the light incident surface, and is configured to transmit light emitted from the light emitting portion. A light utilization unit 5 including a phosphor that emits fluorescence by receiving a part of light leaked from the light incident surface of the light emitting unit to the excitation light source side, and causes the fluorescence to be incident on the light guide plate. I have.

  According to said structure, the light utilization part has a light transmission part which permeate | transmits excitation light, and the excitation light which permeate | transmitted the light transmission part reaches a light emission part. Of the light (primary light) emitted from the light emitting part that has received the excitation light, a part of the light that leaks from the light incident surface, which is the surface on which the excitation light enters the light emitting part, to the excitation light source side is used. Incident light (secondary light) on the light guide plate. Here, examples of the secondary light include fluorescence emitted by a phosphor included in the light utilization unit that receives light from the light emitting unit. As a result, the light emitting device according to the present invention uses light including fluorescence that goes from the light emitting unit to the excitation light source and that does not enter the light guide plate as light that excites the phosphor included in the light utilization unit. It is possible to make the light from the light utilization part incident on the light guide plate. Therefore, it is possible to reduce light loss when light from the light emitting unit enters the light guide plate.

  In the light emitting device 10 according to aspect 9 of the present invention, in the aspect 8, the light emitting unit emits fluorescence by receiving excitation light emitted from the excitation light source, and the light utilization unit is emitted from the excitation light source. Receiving the excitation light, emits fluorescence in a wavelength range corresponding to a color different from that of the light emitting unit, and the wavelength of the fluorescence emitted by the light utilizing unit of the light emitting unit and the light utilizing unit is determined by the light emitting unit. The structure may be longer than the wavelength of the emitted fluorescence.

  According to said structure, a light emission part receives the said excitation light, emits fluorescence, receives the light which does not inject into a light-guide plate among the fluorescence emitted from this light emission part, and a light utilization part carries out from this light emission part. It emits fluorescence having a longer wavelength than fluorescence. Thereby, it is possible to utilize a part of the fluorescence from the light utilization part as light incident on the light guide plate.

  The light-emitting device 10 according to the tenth aspect of the present invention is the light-emitting device 10 according to any one of the first to ninth aspects, wherein the light utilization unit is configured such that light including fluorescence from the light-emitting unit is directed to the light guide plate. It may be provided so as to be in contact with all surfaces except the light emitting surface that emits light.

  According to said structure, the light utilization part provided with the said light transmissive part in the light-incidence surface is in contact with all surfaces other than the light-projection surface of a light emission part. Thereby, the light utilization part can receive the light of all the directions which do not enter a light guide plate among the fluorescence from a light emission part, and can utilize a part of this light as light which injects into a light guide plate.

  The light emitting device 10 according to the aspect 11 of the present invention may be configured such that the light emitting unit includes at least a nanocrystalline phosphor in any one of the aspects 1 to 10.

  Since the nanocrystalline phosphor has high emission intensity and excellent color rendering and color reproducibility, according to the above configuration, a high color rendering illumination device, a backlight of a display device excellent in color reproducibility, etc. A light emitting device applicable to the above can be realized.

  In addition, a display device having any one of the light emitting devices 10 of the present invention is also included in the scope of the present invention.

The light emitting device 10 according to the present invention can also be expressed as follows. A light emitting device 10 according to the present invention includes a light emitting unit (phosphor sheet 4) including a phosphor that emits fluorescence Em in response to excitation light Ex emitted from an excitation light source (LED element 1),
A light guide plate 3 that is provided farther from the excitation light source than the light emitting unit and guides light including fluorescence from the light emitting unit;
The light emitting portion is provided along a light incident surface, which is a surface on which the excitation light is incident, and has a light transmission portion P that transmits the excitation light on the light incident surface, and is emitted from the light emitting portion. A light utilization unit 5 that is incident on the light guide plate as light using a part of light leaking from the light incident surface of the light emitting unit to the excitation light source side of the light.

  According to said structure, the light utilization part has a light transmission part which permeate | transmits excitation light, and the excitation light which permeate | transmitted the light transmission part reaches a light emission part. Of the light (primary light) emitted from the light emitting part that has received the excitation light, a part of the light that leaks from the light incident surface, which is the surface on which the excitation light enters the light emitting part, to the excitation light source side is used. Incident light (secondary light) on the light guide plate. Here, as secondary light, fluorescent light included in the light utilization unit that receives light from the light emitting unit that is scattered or reflected from a part of the light (primary light) leaked from the light emitting unit to the excitation light source side. And fluorescence emitted by the body. As a result, the light emitting device according to the present invention can utilize light including fluorescence directed from the light emitting unit toward the excitation light source and including fluorescence that does not enter the light guide plate as light incident on the light guide plate. is there. Therefore, it is possible to reduce light loss when light from the light emitting unit enters the light guide plate.

  INDUSTRIAL APPLICABILITY The present invention is used for light emitting devices using LED elements and phosphors, such as backlights for display screens of flat-screen TVs, mobile phones, smartphones, personal computers, various indoor and outdoor lighting, and vehicle headlights. Can do.

1 LED element (excitation light source, blue light-emitting element)
2 Package 3 Light guide plate 4 Phosphor sheet (light emitting part)
4G phosphor sheet (second light emitting part)
4R phosphor sheet (first light emitting part)
5 Light Utilization Unit 10 Light Emitting Device 51 Light Scattering Body Em Fluorescence Ex Excitation Light P Light Transmission Unit

Claims (5)

A light emitting unit including a phosphor that emits fluorescence in response to excitation light emitted from an excitation light source;
A light guide plate that is provided farther from the excitation light source than the light emitting unit and guides light including fluorescence from the light emitting unit;
Light emitted from the light emitting unit, provided along the light incident surface that is the surface on which the excitation light is incident in the light emitting unit, and having a light transmitting unit that transmits the excitation light on the light incident surface. of scatters some of the light leaking from the light incident surface of the light emitting portion to said excitation light source side, or by reflecting, e Bei a light utilization unit to be incident on the light guide plate, a
The light emitting unit includes at least the light incident surface, a light emitting surface facing the light incident surface and the light guide plate, and two side surfaces that connect the light incident surface and the light emitting surface and face each other. ,
The light utilization part is provided along the light incident surface, the first contact surface facing the light incident surface, and the two light emitting portions facing each other via the light emitting portion and the two side surfaces of the light emitting portion, respectively. A second tangent surface,
The two second contact surfaces are in contact with a surface facing the light emitting surface of the light guide plate, and are disposed substantially perpendicular to the facing surface . The light utilization part includes a light scatterer that scatters light from the light emitting part,
The light-emitting device according to claim 1. The light scatterer is a particle or air bubble sealed inside,
The light-emitting device according to claim 2. A light emitting unit including a phosphor that emits fluorescence in response to excitation light emitted from an excitation light source;
A light guide plate that is provided farther from the excitation light source than the light emitting unit and guides light including fluorescence from the light emitting unit;
Of the light emitted from the light emitting part, the light emitting part has a light transmitting part that is provided along a light incident surface that is a surface on which the excitation light is incident, and that transmits the excitation light on the light incident surface. includes a phosphor that emits fluorescence by receiving part of the light leaking from the light incident surface of the light emitting portion to said excitation light source side, and e Bei a light utilization unit for entering the fluorescent light to the light guide plate, a ,
The light emitting unit includes at least the light incident surface, a light emitting surface facing the light incident surface and the light guide plate, and two side surfaces that connect the light incident surface and the light emitting surface and face each other. ,
The light utilization part is provided along the light incident surface, the first contact surface facing the light incident surface, and the two light emitting portions facing each other via the light emitting portion and the two side surfaces of the light emitting portion, respectively. A second tangent surface,
The two second contact surfaces are in contact with a surface facing the light emitting surface of the light guide plate, and are disposed substantially perpendicular to the facing surface . The light-emitting unit emits fluorescence in response to excitation light emitted from the excitation light source,
The light utilization unit receives excitation light emitted from the excitation light source, emits fluorescence in a wavelength region corresponding to a color different from the light emitting unit,
Of the light emitting unit and the light utilization unit, the wavelength of fluorescence emitted by the light utilization unit is longer than the wavelength of fluorescence emitted by the light emission unit.
The light-emitting device according to claim 4.

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