CN105375329A - Wavelength conversion unit, preparation method thereof, related wavelength conversion sheet and light emitting device - Google Patents

Abstract

The invention belongs to the technical field of display and lighting, and discloses a wavelength conversion unit with a core-shell structure and a preparation method thereof, wherein the core layer of the core-shell structure is a heat-conducting fiber filament, and the shell layer contains fluorescent powder. The invention also discloses a wavelength conversion sheet formed by arranging and bonding the above-mentioned wavelength conversion units and a light-emitting device containing the wavelength conversion sheet. Since the wavelength conversion unit of the present invention adopts a specific core-shell structure, when the excitation light is incident on the wavelength conversion unit, it can directly irradiate the fluorescent powder without being blocked by the heat-conducting fiber filament. At the same time, the heat generated by the excitation of the fluorescent powder can be directly and rapidly conducted along the heat-conducting fiber filaments of the core layer and dissipated to the outside, thereby improving the overall heat dissipation of the wavelength conversion unit.

Description

Wavelength conversion unit and its preparation method, related wavelength conversion sheet and light-emitting device

technical field

The invention relates to the technical field of display and illumination, in particular to a wavelength conversion unit and a preparation method thereof, a wavelength conversion sheet and a light-emitting device prepared therefrom.

Background technique

With the development of display and lighting technology, the original LED or halogen bulb as a light source is increasingly unable to meet the high power and high brightness requirements of display and lighting. Visible light of various colors can be obtained by using excitation light emitted by a solid-state light source such as LD (Laser Diode, laser diode) to excite wavelength conversion materials, and this technology is increasingly used in lighting and display. This technology has the advantages of high efficiency, low energy consumption, low cost, and long life, and is an ideal alternative to existing white or monochromatic light sources.

The wavelength conversion device in the prior art usually uses silica gel or epoxy resin as a filler to encapsulate powdered wavelength conversion materials (such as fluorescent powder) into layers. The silica gel/resin phosphor layer has poor heat resistance, and under the irradiation of high-power excitation light, the silica gel/resin is easy to age and deform, resulting in a decrease in its light transmittance, which seriously affects the service life of the wavelength conversion device. Therefore, some researchers proposed to use inorganic fillers (such as glass powder) instead of silica gel/resin, and encapsulate the wavelength conversion material into layers through the sintering process. The wavelength conversion device obtained by this method has good heat resistance and can withstand high-power excitation light irradiation. No change.

However, the thermal conductivity of inorganic fillers is poor, and the heat generated by the wavelength conversion material under the irradiation of excitation light is difficult to quickly conduct to the surface of the wavelength conversion device through the inorganic filler and dissipate, resulting in heat accumulation around the wavelength conversion material and temperature rise. High, but the luminous efficiency of the wavelength conversion material decreases at high temperature, which in turn reduces the efficiency of the wavelength conversion device.

Due to the above-mentioned defects of various wavelength conversion devices, people are striving to find a material with good thermal stability and high thermal conductivity as a filler for encapsulating the wavelength conversion material. However, such materials with both thermal stability and thermal conductivity often have low light transmittance, which prevents the excitation light from reaching the wavelength conversion material. Therefore, a structural unit that combines materials with both thermal stability and thermal conductivity with wavelength conversion materials needs to be developed urgently.

Contents of the invention

In view of the above defects in the prior art, the present invention provides a wavelength conversion unit on the one hand, the wavelength conversion unit is a tubular fluorescent fiber with a core-shell structure, wherein the core layer of the core-shell structure is a heat-conducting fiber filament, and the core-shell structure The shell layer contains phosphor.

In a preferred embodiment of the present invention, the thermal conductivity of the thermally conductive fiber is greater than or equal to 80 W/mK. Preference is given to monofilaments or multifilaments. It is preferably one or more selected from boron nitride fiber filaments, aluminum nitride fiber filaments, carbon nanotubes or carbon nanowires. The diameter of the thermally conductive fiber filament is 1-30 μm, preferably 5-20 μm.

In a preferred embodiment of the invention, the shell layer has a thickness of less than 5 μm, preferably less than 1 μm.

In a preferred embodiment of the present invention, the structural formula of the phosphor is (Y _1-a Ln _a ) ₃ (Al _1-b Ga _b ) ₅ O ₁₂ :Ce or (Ca _1-ab Sr _a Ba _b )AlSiN ₃ : Eu, where 0≤a≤1, 0≤b≤1, Ln is lanthanide.

Another aspect of the present invention provides a method for preparing the wavelength conversion unit of the present invention, comprising:

Step 1: providing the above-mentioned heat-conducting fiber filament;

Step 2: providing wavelength conversion material precursor slurry, placing the thermally conductive fiber filament in the wavelength conversion material precursor slurry, and depositing the wavelength conversion material precursor on the surface of the thermally conductive fiber filament;

Step 3: Sintering the heat-conducting fiber filaments whose surface is covered with the precursor of the wavelength conversion material to obtain a wavelength conversion unit with a core-shell structure.

Another aspect of the present invention provides a wavelength conversion sheet, which is composed of the wavelength conversion unit described in the present invention, and the wavelength conversion sheet includes one wavelength conversion unit or a combination of multiple wavelength conversion units.

In a preferred embodiment of the present invention, the wavelength conversion sheet of the present invention further includes an adhesive for wrapping the wavelength conversion unit into a layer, and the adhesive may be an organic adhesive or an inorganic adhesive.

In a preferred embodiment of the present invention, the wavelength conversion units in the wavelength conversion sheet of the present invention are arranged in grids or stripes in the wavelength conversion sheet.

In a preferred embodiment of the present invention, the wavelength conversion sheet of the present invention further includes at least one wavelength conversion unit connecting its two surfaces.

Another aspect of the present invention provides a light-emitting device, which includes an excitation light source, and further includes the wavelength conversion sheet of the present invention.

Compared with the prior art, the present invention has the following beneficial effects:

The wavelength conversion unit of the present invention is a tubular fluorescent fiber unit with a core-shell structure, wherein the core layer of the core-shell structure is composed of heat-conducting fiber filaments, and the shell layer of the core-shell structure is composed of fluorescent powder. When the excitation light is incident on the wavelength conversion unit, it can be directly irradiated on the phosphor without being blocked by the heat-conducting fiber; at the same time, the heat generated by the excitation of the phosphor can be directly conducted and dissipated rapidly along the heat-conducting fiber of the nuclear layer to the outside world, thereby improving overall heat dissipation.

Description of drawings

Fig. 1 is a schematic diagram of the structure of the wavelength conversion sheet of the present invention.

1: Wavelength conversion film;

2: wavelength conversion unit;

3: Phosphor powder film shell;

4: Thermally conductive fiber core layer.

FIG. 2 is a schematic structural view of a wavelength conversion sheet composed of wavelength conversion units arranged in grid form according to the present invention.

FIG. 3 is a schematic structural view of a wavelength conversion sheet composed of wavelength conversion units arranged in stripes according to the present invention.

detailed description

The present invention will be described in further detail below in conjunction with the accompanying drawings, but it is not intended to limit the present invention.

Embodiment 1 The structure and working principle of the wavelength conversion sheet of the present invention

As shown in FIG. 1 , the wavelength conversion sheet 1 includes a wavelength conversion unit 2 , the wavelength conversion unit 2 is a core-shell structure, which includes a phosphor film shell layer 3 and a heat-conducting fiber filament core layer 4 .

The excitation light emitted by the excitation light source is incident on the wavelength conversion sheet 1, and then irradiates on the wavelength conversion unit 2. The wavelength conversion unit 2 has a core-shell structure, wherein the shell layer 3 is composed of phosphor powder, and the core layer 4 is composed of heat-conducting fiber filaments. After the phosphor powder in the shell layer 3 is irradiated by the excitation light, it absorbs the excitation light and emits the received light, and releases heat at the same time, and then the heat is conducted and dissipated through the heat-conducting fiber filaments of the core layer 4 . The heat-conducting fiber filaments form a heat-conducting network in the wavelength conversion sheet 1. Compared with the prior art, the heat is transmitted to the surface of the wavelength conversion sheet through the packaging material and then dissipated, which greatly improves the thermal conductivity of the wavelength conversion sheet.

In this embodiment, the thermal conductivity of the heat-conducting fiber directly affects the heat dissipation effect of the wavelength conversion sheet of the present invention. To achieve an ideal heat dissipation effect, the heat-conducting fiber needs to have a higher thermal conductivity to prevent heat from radiating near the wavelength conversion material. accumulation. Preferably, the thermal conductivity of the thermally conductive fiber filament of the core layer 4 is greater than or equal to 80W/mK, and the material corresponding to this thermal conductivity can be a nitride ceramic material such as boron nitride or aluminum nitride, or carbon nanotube or carbon nanometer In addition, the thermally conductive fiber filament can also be a combination of the above materials.

In this embodiment, the heat-conducting fiber cannot be too thin, otherwise it will be difficult to prepare a phosphor shell layer on its surface to form a core-shell structure, and the smaller the diameter of the heat-conducting fiber, the greater its thermal resistance along the direction of heat propagation; At the same time, the thermally conductive fiber filaments should not be too thick, otherwise it will block the incident light and hinder the propagation of the excitation light in the wavelength conversion sheet, so that the part of the wavelength conversion sheet far away from the incident position of the excitation light cannot be irradiated by the excitation light, resulting in wavelength The luminous efficiency of the conversion sheet decreases. Preferably, the diameter of the thermally conductive fiber in this embodiment is 1-30 μm. Under this parameter, the conditions for preparing the core-shell structure and low thermal resistance can be met, and the luminous efficiency of the wavelength conversion sheet can be guaranteed. More preferably, the diameter of the thermally conductive fiber filament is 5-20 μm.

In this embodiment, the thermally conductive fiber is a monofilament. In the wavelength conversion unit 2 with a single heat-conducting fiber as the core layer 4, the thermal resistance in the process of the heat generated by the wavelength conversion material dissipating to the outside only includes the material thermal resistance of the single heat-conducting fiber and the interface between the shell layer 3 and the core layer 4 Thermal resistance, so the monofilament has the advantage of good thermal conductivity as a thermally conductive fiber. In other cases, for example, when it is difficult to obtain monofilaments with a large enough diameter, the thermally conductive filaments may also be multifilaments, that is, a clustered structure of multiple monofilaments. The multi-filament structure can not only make up for the defect that the diameter of the single fiber is not large enough, but also enhance the mechanical strength of the heat-conducting fiber. However, compared with monofilaments, multifilaments increase the interfacial thermal resistance between individual filaments, and the preparation is more complicated. In addition, for some materials, such as carbon nanotubes, it is easy to produce a multi-fiber structure during the preparation process, and it can be directly used as a heat-conducting fiber.

The shell layer 3 is a fluorescent powder layer, and the fluorescent powder has the characteristic of absorbing excitation light of a certain wavelength and emitting light with a peak wavelength greater than that of the excitation light. In this embodiment, the phosphor is preferably a structural formula such as (Y _1-a Ln _a ) ₃ (Al _1-b Ga _b ) ₅ O ₁₂ :Ce or (Ca _1-ab Sr _a Ba _b )AlSiN ₃ :Eu The fluorescent powder shown, wherein 0≤a≤1, 0≤b≤1, Ln is a lanthanide. Specifically, the phosphor can be a garnet-based phosphor material (Y _1-a Ln _a ) ₃ (Al _1-b Ga _b ) ₅ O ₁₂ :Ce, or a nitride (Ca _1-ab Sr _a Ba _b )AlSiN ₃ :Eu which absorbs blue light with a peak wavelength of 420nm to 470nm and emits red light with a peak wavelength of 610nm to 660nm .

For the phosphor layer of the shell layer 3, the excitation depth of the excitation light is limited, and the absorption depth of the excitation light by the phosphor layer only occurs in the surface layer less than 1 μm, while the phosphor layer in the inner layer has a smaller effect on the light emission. Therefore, in this embodiment, preferably, the thickness of the shell layer 3 is less than 5 μm, and further preferably, the thickness of the shell layer 3 is less than 1 μm.

Embodiment 2 Preparation of wavelength conversion sheet of the present invention

The wavelength conversion sheet shown in Example 1 is prepared using the method shown in this example, which specifically includes the following steps:

Step 1: Preparation of thermally conductive fiber filaments.

In this embodiment, the heat-conducting fiber can be selected from existing aluminum nitride fiber, boron nitride fiber or carbon nanotubes in the market, or can be prepared by electrospinning. For the boron nitride fiber, the boron oxide fiber is first prepared by electrospinning, and then nitrided to obtain the boron nitride fiber.

Step 2: Preparation of thermally conductive fiber filaments deposited on the surface to form a film.

In this embodiment, the wavelength conversion material precursor slurry is provided, and the thermally conductive fiber filament is placed in the wavelength conversion material precursor slurry, so that the wavelength conversion material precursor is deposited on the surface of the thermally conductive fiber filament to form a film.

Specifically, in this embodiment, the thermally conductive fiber filaments are placed in a mixed sol of Y(NO ₃ ) ₃ , Al(NO ₃ ) ₃ and Ce(NO ₃ ) ₃ , stirred evenly, and the pH value is controlled to make the shell layer The precursor is deposited on the surface of the BN fiber to form a film, wherein YAG phosphor can be obtained by mixing and sintering Y(NO ₃ ) ₃ , Al(NO ₃ ) ₃ and Ce(NO ₃ ) ₃ . The mixed sol can also choose other phosphor raw material sols, for example, the sol containing the structural formula (Y _1-a Ln _a ) ₃ (Al _1-b Ga _b ) ₅ O ₁₂ :Ce or (Ca _1-ab Sr _a Ba _b ) AlSiN ₃ : raw material of Eu phosphor, and the corresponding phosphor can be obtained by sintering these raw materials.

Step 3: Preparation of the wavelength conversion unit.

In this embodiment, the thermally conductive fiber filaments whose surface is covered with the precursor of the wavelength conversion unit are sintered to obtain a wavelength conversion unit with a core-shell structure.

Specifically, the sintering temperature is the temperature at which the raw material of the phosphor powder in the above step 2 is sintered into the phosphor powder. During the sintering process, the heat-conducting fiber filaments of the core layer remain unchanged, and the wavelength conversion material precursor of the shell layer is sintered into a wavelength conversion material, thereby obtaining a core-shell structure in which the shell layer is a wavelength conversion material and the core layer is a heat-conducting fiber filament. wavelength conversion unit.

Step 4: Preparation of the wavelength conversion sheet.

In this embodiment, the wavelength conversion unit is mixed with an adhesive, and the adhesive wraps the wavelength conversion unit into a layer to obtain a wavelength conversion sheet. The adhesive can be an organic adhesive such as silica gel or epoxy resin, or an inorganic adhesive such as glass powder. Among them, in the embodiment using inorganic adhesive, it also includes the process of sintering the mixed wavelength conversion unit and inorganic adhesive to form a layer, wherein the softening temperature of the inorganic adhesive used is lower than that of the wavelength conversion unit in step 3. the sintering temperature.

Example 3 Preparation of a wavelength conversion sheet composed of grid-like or stripe-like wavelength conversion units

In the wavelength conversion sheet shown in FIG. 2 , the wavelength conversion units are arranged in a grid in the wavelength conversion sheet, and the wavelength conversion sheet includes a continuous wavelength conversion unit or a plurality of discontinuous wavelength conversion units. A continuous wavelength conversion unit has only one continuous heat conduction channel, and the temperature in the heat conduction channel is uniformly distributed, which makes the temperature distribution of the entire wavelength conversion sheet uniform, thereby avoiding the defect of uneven thermal expansion inside the wavelength conversion sheet; multiple discontinuous wavelengths The conversion unit increases the heat conduction channel to make the heat conduction faster, which is beneficial to the improvement of the heat dissipation effect of the wavelength conversion sheet. The shown wavelength conversion sheet includes at least one wavelength conversion unit connected to the two surfaces of the wavelength conversion sheet. This structure can quickly diffuse heat to the surface of the wavelength conversion sheet, and at the same time reduce the temperature difference between the two surfaces of the wavelength conversion sheet. Protect one surface from overheating. During the preparation process, the wavelength conversion unit can be mixed with an adhesive, so that the adhesive wraps the wavelength conversion unit into layers to obtain a wavelength conversion sheet.

The wavelength conversion sheet shown in FIG. 3 is a modified embodiment of the wavelength conversion sheet shown in FIG. 2 , wherein the wavelength conversion units are arranged in stripes in the wavelength conversion sheet.

The present invention also provides a light-emitting device, which includes an excitation light source and a wavelength conversion sheet, wherein the wavelength conversion sheet may have the structures and functions of the above-mentioned embodiments. The light-emitting device can be applied to a projection system, such as a liquid crystal display (LCD, Liquid Crystal Display) or a digital light path processor (DLP, Digital Light Processor) projector; it can also be applied to a lighting system, such as an automobile lighting lamp; it can also be applied to the field of 3D display technology middle.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention within.

Claims (13)

1. a wavelength conversion unit, is characterized in that, described wavelength conversion unit is the tubular fluorescent fiber of nucleocapsid structure, and the stratum nucleare of wherein said nucleocapsid structure is heat conducting fiber silk, and the shell of described nucleocapsid structure comprises fluorescent material.

2. wavelength conversion unit according to claim 1, is characterized in that, the thermal conductivity of described heat conducting fiber silk is more than or equal to 80W/mK.

3. wavelength conversion unit according to claim 1, is characterized in that, described heat conducting fiber silk is monofilament or multifilament.

4. wavelength conversion unit according to claim 3, is characterized in that, described heat conducting fiber silk be selected from boron nitride fiber silk, aluminium nitride fibres silk, carbon nano-tube or carbon nanocoils one or more.

5. wavelength conversion unit according to claim 3, is characterized in that, the diameter of described heat conducting fiber silk is 1 ~ 30 μm, is preferably 5 ~ 20 μm.

6. wavelength conversion unit according to claim 1, is characterized in that, the thickness of described shell is less than 5 μm, is preferably less than 1 μm.

7. wavelength conversion unit according to claim 1, is characterized in that, the structural formula of described fluorescent material is (Y _1-aln _a) ₃(Al _1-bga _b) ₅o ₁₂: Ce or (Ca _1-a-bsr _aba _b) AlSiN ₃: Eu, wherein 0≤a≤1,0≤b≤1, Ln is lanthanide series.

8. prepare the method as the wavelength conversion unit in claim 1-7 as described in any one, comprising:

Step one: heat conducting fiber silk is provided;

Step 2: provide material for transformation of wave length precursor pulp, is placed in described material for transformation of wave length precursor pulp by described heat conducting fiber silk, makes described material for transformation of wave length presoma in described heat conducting fiber silk surface deposition film forming;

Step 3: the heat conducting fiber silk sintering described surface coverage material for transformation of wave length presoma, obtains the wavelength conversion unit of nucleocapsid structure.

9. a wavelength conversion sheet, is made up of such as the wavelength conversion unit in claim 1-7 as described in any one, and described wavelength conversion sheet comprises the combination of a wavelength conversion unit or multiple wavelength conversion unit.

10. wavelength conversion sheet according to claim 9, is characterized in that, also comprises bonding agent, and for described wavelength conversion unit is wrapped up stratification, described bonding agent is organic adhesive or inorganic adhesive.

11. wavelength conversion sheets according to claim 9, is characterized in that, described wavelength conversion unit is the arrangement in latticed arrangement or in striated in described wavelength conversion sheet.

12. wavelength conversion sheets according to claim 9 or 10, is characterized in that, at least comprise one and connect the surperficial wavelength conversion unit of two of described wavelength conversion sheet.

13. 1 kinds of light-emitting devices, comprise an excitation source, also comprise as the wavelength conversion sheet in claim 9-12 as described in any one.