JP2021508179A - Porous micron-sized particles for controlling light scattering - Google Patents

Abstract

This application describes systems and methods for adjusting light scattering in an optically functional porous layer of an LED. The layer contains a non-absorbent material structure with multiple submicron pores and a polymeric substrate. The non-absorbent material forms multiple micron-sized porous particles dispersed throughout the layer or mesh slab, and are the multiple submicron pores located within each micron-sized porous particle? , Or to form an interconnected network of submicron holes in the mesh slab. Polymer substrates such as high refractive index silicone fill multiple submicron pores and form interfaces between the materials. The difference in refractive index between the materials allows light scattering to occur at the interface of the materials. Light scattering can be reduced as a function of temperature, creating a system for adjusting light scattering when the LED is off and on.

Description

Light emitting diodes can be used as white light sources in a variety of applications such as flash light sources and filament lamps for mobile phone cameras. Such LEDs are sometimes referred to herein as white LEDs.

The white LED may appear to emit white light from the observer's point of view when the LED is on. However, these LEDs may actually consist of a light emitting semiconductor structure that emits non-white light and a wavelength conversion structure that makes the non-white light appear white to the observer. For example, a white LED may be formed from a blue emitting semiconductor structure covered with a yellow emitting phosphor layer. The blue light photons emitted by the luminescent semiconductor structure can either pass through the yellow emitting phosphor layer as blue photons or be converted into yellow photons by the yellow emitting phosphor layer. The combination of blue and yellow photons that are ultimately emitted by the LED makes the light emitted by the LED appear white to the observer.

LEDs can also be used over a range of dimtone settings. However, for example, an LED that appears to emit colder light at a higher dim tone setting may appear to emit colder light at a lower dim tone setting. Similarly, for example, an LED that appears to emit warmer light at a lower dim tone setting may appear to emit warmer light at a higher dim tone setting.

An optically functional porous structure for use in an LED, and a method of making such an optically functional porous structure, are described herein. The optically functional porous structure includes a non-absorbent material structure, which may be a dielectric structure containing a plurality of submicron pores and a polymeric substrate [matrix]. The non-absorbent material structure itself may be composed of a plurality of micron-sized porous particles. Furthermore, at the first temperature, the refractive index of the non-absorbent material structure is different from the refractive index of the polymer substrate, and the difference in the refractive index between the refractive index of the non-absorbent material structure and the refractive index of the polymer substrate is optically different. A plurality of submicron pores in a porous structure functioning as a function are configured to have a light scattering ability at a first temperature. Since the index of refraction difference between the index of refraction of the non-absorbent material structure and the index of refraction of the polymer substrate decreases with temperature changes, the light scattering capacity of multiple submicron pores also decreases with these corresponding temperature changes. It changes with.

FIG. 5 is an exemplary light emitting device (LED) diagram comprising a light emitting semiconductor structure and a white material layer in the off state.

FIG. 5 is an exemplary off-state white layer composed of micron-sized porous particles with interconnected submicron pores filled with a polymer substrate.

FIG. 6 is a diagram of another exemplary off-state white layer composed of mesh slabs with interconnected submicron pores filled with a polymer substrate.

FIG. 5 is a scanning electron micrograph of a cross section of micron-sized porous glass bead particles containing submicron pores with silicon injected into the submicron pores.

FIG. 5 is a diagram (photograph) of a drop-casted silicone layer at 25 ° C with the addition of micron-sized porous particles 25-45 μm in diameter, including submicron pores.

FIG. 6 is a diagram (photograph) of a drop cast silicone layer at 200 ° C. with the addition of micron-sized porous particles 25-45 μm in diameter, including submicron pores.

A graphical representation of light transmission in a 4 nm to 150 μm layer of high refractive index silicone containing 25 wt% porous silica particles of size 50 μm with an effective pore size of 100 nm, as a function of temperature.

FIG. 3 is a microscopic image of micron-sized porous particles filled with silicone and containing air voids.

A graphical representation of the shift in color points of light generated from a 1202 COB chip light source where the drive current leads are shifted from 10 mAmp to 400 mAmp, the 1202 COB light source is an interconnected submicron pore filled with a polymer substrate. It is covered with a cover layer containing micron-sized porous particles.

It is a flow chart of the method of adjusting light scattering by using the porous structure which functions optically.

White LEDs may appear to emit white light when turned on, but such LEDs may appear to be the color of the wavelength conversion material when turned off. For example, a white LED containing a fluorescent layer that emits yellow light may appear yellow or green to the observer when turned off, such as when viewed on a store shelf. Nevertheless, the average consumer may expect products containing white LEDs to appear white even when off. For example, a person who goes into a store to buy a white light bulb usually expects the white light bulb to actually look white, and if the light bulb looks yellow or green, considers the light bulb to be defective. There can be. The same can be said for mobile phone consumers, who may expect the camera flash to appear white. Such products would be more likely to sell to consumers if the LEDs look as white as they are on when the LEDs are off.

It may be preferable to change the color point of the LED light. For example, when the LED lights are dimmed, users may prefer to observe warmer colors with these lower dim tone settings. Conversely, when the LED light is bright, users may prefer to observe cooler colors. Increasing the drive current leads to an increase in temperature, which results in a change in color spots when changes in light scattering correlate with changes in temperature. This is partly emitted from the LED by changing the relative amount of scattered blue light to the amount of scattered red light, for example because blue light scatters light more strongly than red light. This is because the perceived color point of light may change.

For LEDs in the off state White, non-fluorescent, inert material granules to provide a white appearance in the off state or to provide a warmer color when the lighting is dimmed. Has been used. These granules are often submicron sized granules. This is because particles of this size can function as particularly effective light scattering elements. Examples of such materials include titanium dioxide (TiO ₂ ) and zirconium oxide (ZrO ₂ ). Submicron-sized particles of these materials are mixed with a transparent material such as silicone and applied onto a non-white LED surface to make it appear whiter to the observer, for example with the LED off. Can be done. However, such granules of white, non-fluorescent, inert material may remain white while the device is on, resulting in some scattering of light emitted from the LED when the device is on. , May reduce the lumen output of the LED.

In these examples, the magnitude of light scattering in either state depends on the concentration of submicron particles in the optically functional layer and the difference in refractive index between the submicron particles and the transparent material. With respect to the former, increasing the concentration of submicron particles can increase light scattering in the off state. However, as the concentration of these particles increases, this can result in a decrease in the lumen output of the LED in the on state. In addition, there may be problems with the processing of the material. For example, as the viscosity of a mixture increases with increasing concentration of submicron particles, mixing of materials becomes more difficult. Another problem is that the final layer can be too brittle due to the high particle addition.

Regarding the difference in refractive index between the refractive index of the submicron particles and the refractive index of the transparent layer, the difference must be large enough so that sufficient light scattering from the submicron particles can occur. On the contrary, the index of refraction difference should not be too large so that light scattering does not occur at all temperatures within the possible range of use. For example, if the index of refraction of the transparent layer is very high compared to the index of refraction of the submicron particles, the decrease in the index of refraction of the transparent layer may not be sufficiently close to the index of refraction of the submicron particles. Light scattering will occur over all temperatures within.

The temperature of the LED may rise in the on state compared to the off state, and the increase in light scattering may reduce the lumen output of the LED, so that light scattering occurs as the temperature rises. Ideally, it should be reduced. As mentioned above, the most commonly used scattered particle is TiO ₂ . However, _{the refractive index of TiO 2} is high, while the refractive index of silicone, which is a commonly used transparent layer material, is low, and the difference in refractive index between the two is greater than 0.5. Using this combination of materials, an increase in temperature can result in a _{larger index of refraction difference between TiO 2} and silicone, which can further increase light scattering in the on state. Therefore, it may be more preferable to use scattered particles having a lower refractive index with respect to the transparent material.

An example of such a particle is MgF ₂ with a refractive index of 1.37. Its refractive index is smaller than, but close to, that of high-refractive-index silicone, which can have a refractive index of 1.55. However, since the index of refraction difference between the two materials is only 0.16, a much higher concentration of MgF ₂ is required to achieve sufficient light scattering in the off state, as described above. It can cause problems in the processing of materials.

The embodiments described herein provide a white LED that may appear white to the observer in both the LED on and off states, yet may reduce or eliminate scattering in the LED on state. Thereby, the product containing such an LED is aesthetically pleasing to the observer without affecting the quality of the LED itself or the structure of its material. In the embodiments described herein, the color dots shift to warmer colors at lower dim tone settings, while the color dots shift to colder colors at higher dim tone settings. It can also provide adjustable LED light. Such embodiments may rely on the difference in refractive index between the refractive index of the transparent material, which may be a polymeric substrate, and the refractive index of a non-absorbent material, which may be a dielectric material. ..

In certain embodiments, the non-absorbent material structure itself may consist of micron-sized porous particles dispersed throughout an optically functional layer, the micron-sized porous particles being within the particles themselves. Includes a network of interconnected submicron pores. In certain embodiments, the non-absorbent material structure may instead consist of a mesh slab of porous dielectric material that itself contains a network of submicron pores. In each case, the submicron pores are filled with a polymer substrate, forming an interface between the polymer substrate and the non-absorbent material in the form of submicron pores. This is a property disclosed herein in combination with different temperatures of the LED in the on-to-off state or low intensity vs. high intensity (the index of refraction of the materials described herein can vary as a function of temperature). Relied on to form LEDs with.

In some embodiments, the index of refraction of the polymer substrate is greater than the index of refraction of the non-absorbent material structure in the LED off state, allowing a light scattering effect to occur at the interface between the two materials. However, in the LED-on state, as the temperature rises, the refractive index of the polymer substrate decreases, and the refractive index difference between the non-absorbent material that outlines the shape of the submicron pores and the polymer substrate that fills the submicron pores. As a result, light scattering by the non-absorbent material to the submicron pore interface is reduced or eliminated. These features scatter light at lower temperatures, such as room temperature, when the LED is off and appear white, and do not scatter, or at least scatter, light when the LED is on at higher temperatures. It can provide LED light that reduces the amount of light (which can lead to increased output of LED light).

These refractive index properties can also provide LEDs whose intensity changes alter light scattering. For example, if the LED intensity is high, the temperature may rise and light scattering may decrease accordingly. This may allow changing the color point setting of the LED light. For example, blue light, which contributes to the tone of colder light that is scattered more strongly than red light, may be more affected by these changes in temperature and light scattering capacity. In this case, as a result of the temperature rise that can reduce light scattering, more blue light will be detected, which can cause a shift of the color point to a cooler color. Conversely, when the LED intensity is low, the temperature may drop and light scattering may increase accordingly. In this example, as a result of lower temperature and increased light scattering, less blue light is detected and the color spots may shift to warmer colors.

In some embodiments, the index of refraction of the non-absorbent material is greater than the index of refraction of the polymer substrate, and an increase in temperature reduces light scattering. This can impair changing the color point setting of the LED light. This embodiment can be used, for example, to prevent or minimize unwanted color shifts that would normally occur as the temperature rises. Color changes can be reduced by increasing light scattering as the temperature rises. This embodiment can also be used to shift the color point to a warmer color as the temperature increases.

In certain embodiments, the non-absorbent material structure itself may consist of a plurality of micron-sized porous particles containing a network of submicron pores dispersed throughout. Alternatively, the non-absorbent material structure may consist of a mesh slab of a porous dielectric material that itself contains a submicron pore network. In each of these embodiments, the submicron pores are filled with a polymer substrate, forming an interface between the polymer substrate and the non-absorbent material structure, which is approximately in the form of submicron pores.

In each of these embodiments, the index of refraction of the polymer substrate is greater than the index of refraction of the non-absorbent material structure in the LED off state, allowing a light scattering effect to occur at the interface between the two materials. However, in the LED-on state, as the temperature rises, the refractive index of the polymer substrate decreases, and the refractive index difference between the non-absorbent material that outlines the shape of the submicron pores and the polymer substrate that fills the submicron pores. As a result, light scattering by the submicron pore-dielectric surface interface is reduced or eliminated. These same unique properties of the material also allow for changes in the color point setting of the LED light. For example, at low brightness, the LED light may shift towards warmer tones, and at higher brightness, the LED light may shift towards colder tones.

The index of refraction of non-absorbent materials can also decrease with increasing temperature, but the change in index of refraction between the first and second temperatures is the polymer at the first and second temperatures. Low compared to changes in the refractive index of the substrate. Solid materials, such as non-absorbent materials, have a much lower coefficient of expansion than, for example, silicone, and thus have a much smaller change in index of refraction as a function of temperature. Therefore, changes in temperature have a greater effect on the refractive index of the polymer substrate than on non-absorbent materials. Further details regarding the polymeric substrate and the non-absorbent material are described below and are shown in FIG.

Furthermore, with respect to the difference in refractive index between the two materials, the difference between the refractive indexes of each material must be minimal in order to achieve sufficient light scattering in the off state. Notably, this minimum can be influenced by factors such as the concentration of light-scattering particles in the optically functional layer. For example, if the difference in index of refraction between materials is smaller, the higher concentration of light-scattering particles compensates for the relatively small difference in index of refraction between materials, and the equivalent of light-scattering particles at lower concentrations. It can help to achieve a larger level of light scattering than at a different index of refraction. However, there is a limit to the concentration of particles that can be put into the layer without compensating for its shape. Conversely, in order to sufficiently reduce light scattering in the on state, the difference between the refractive indexes of each material can be only a maximum value. If the index of refraction difference between the two materials is too large to be sufficiently reduced within any reasonable temperature change, then a functionally effective reduction in light scattering cannot occur in the on state.

In some embodiments, the difference in refractive index between the refractive index of the non-absorbent material and the refractive index of the polymeric substrate is 0.3 or less. In some embodiments, the difference in refractive index between the refractive index of the non-absorbent material and the refractive index of the polymeric substrate is 0.2 or less. According to one embodiment, the difference in refractive index between the refractive index of the non-absorbent material and the refractive index of the polymeric substrate is less than or equal to 0.1. In one exemplary embodiment, the difference in refractive index between the refractive index of the non-absorbent material and the refractive index of the polymeric substrate is 0.07.

A feature described herein is to provide an LED that scatters light at room temperature when the LED is off, appears white, and reduces the amount of scattered light when the LED is on. Other embodiments, such as color point adjustment, rely on the same principles described herein for the difference in index of refraction and the change in index of refraction as a function of temperature.

FIG. 1A shows an exemplary light emitting device (LED) 100 that includes a light emitting semiconductor structure 115, a wavelength conversion material 110, and a white material in the off state. The off-state white material may be an optically functional porous structure 105 containing multiple micron-sized porous particles or mesh slabs containing submicron pores. The contacts 120 and 125 may be coupled to the light emitting semiconductor structure 115, either directly or via other structures such as submounts, for electrical connection to the circuit board or other board or device. In embodiments, contacts 120 and 125 may be electrically isolated from each other by gaps 127, which may be filled with a dielectric material. The contacts or interconnects 120 and 125 may be, for example, solder, stud bumps, or gold layers. An optically functional porous structure 105 containing multiple micron-sized porous particles or mesh slabs, including submicron pores, is in contact with the LED.

In certain embodiments, the light emitting semiconductor structure 115 emits blue light. In such embodiments, the wavelength conversion material 110 may include, for example, a yellow emission wavelength conversion material, or a green and red emission wavelength conversion material, which emits light emitted by the respective phosphors. Produces white light when combined with the blue light emitted by 115. In another embodiment, the light emitting semiconductor structure 115 emits UV light. In such embodiments, the wavelength conversion material 110 may include, for example, blue and yellow wavelength conversion materials or blue, green and red wavelength conversion materials. Wavelength conversion materials that emit light of other colors may be added to adjust the spectrum of light emitted from the LED 100. In certain embodiments, the color spots of the LED 100 may be shifted based on the properties of the optically functional porous structure 105 described herein.

FIG. 1B is an enlarged view of an embodiment of an optically functional porous structure 105, wherein the optically functional porous structure 105 contains a plurality of micron-sized porous particles 150. A network of submicron pores 165 (shown in FIG. 2) is dispersed throughout each micron-sized porous particle 150, and the pores are filled with polymer substrate 180 (shown in white) in this figure. ing. The plurality of submicron pores 165 form an interconnected network surrounded by a non-absorbent material 160 (shown in white). In certain embodiments, the micron-sized porous particles 150 may be micron-sized porous glass bead particles. In one exemplary embodiment, the micron-sized porous particles 150 may be micron-sized porous silica particles. In one embodiment, the micron-sized porous particles 150 are micron-sized porous magnesium fluoride particles.

FIG. 1C is an enlarged view of an embodiment of an optically functional porous structure 105, wherein the optically functional porous structure 105 is a non-absorbent material having a plurality of submicron pores (not shown). It contains a mesh slab formed of 160, and the pores are filled with polymer substrate 180 in this figure. In this embodiment, an interconnected network of polymer substrates 180 is formed across the mesh slab and is the interface between the polymer substrate 180 and the non-absorbent material 160 of the mesh slab surrounding it (interface in FIG. 2). Similar to 170).

FIG. 2 is a scanning electron micrograph showing a cross section of an exemplary micron-sized porous particle 150. Submicron pores 165 are dispersed through the micron-sized porous particles 150. The submicron pores 165 are surrounded by a non-absorbent material 160 structure to form an interconnected network within the micron-sized porous particles 150. In this embodiment, the submicron pores 165 are filled with a polymer substrate 180. Light that encounters micron-sized porous particles 150, including submicron pores 165, is multiple scattered. Transmission is not excluded, but only part of the light that would otherwise pass through a completely transparent structure. In certain embodiments, the micron-sized porous particles 150 may be micron-sized porous glass bead particles.

In certain embodiments, the polymer substrate 180 is any optically functional material, including silicone; heat and light resistant substrates such as optical grade silicone substrates; or sol-gel materials, organically modified ceramics. It may be any other suitable material, such as (ormocer), or a polysilisan-based substrate. In certain exemplary embodiments, the polymer substrate 180 may be a high refractive index silicone. Non-limiting examples of silicones can include phenylated silicones (ie, methylphenyl), and silicones filled with high refractive index nanoparticles.

According to certain embodiments, the refractive index of the polymer substrate 180 may be greater than the refractive index of the micron-sized porous particles 150 or the non-absorbent material 160 of the mesh slab network. In certain embodiments, the index of refraction of the polymer substrate 180 may be less than the index of refraction of the micron-sized porous particles 150 or the non-absorbent material 160 of the mesh slab network. In certain embodiments, the polymeric substrate is a silicone having a refractive index in the range of at least 1.4-1.7 at room temperature. In certain embodiments, the polymeric substrate is a silicone having a refractive index in the range of at least 1.46 to 1.56 at room temperature. In certain embodiments, the silicone has a refractive index in the range of at least 1.50 to 1.56 at room temperature. In certain embodiments, the index of refraction of the polymer substrate 180 can decrease with increasing temperature. In certain embodiments, the index of refraction of the silicone may decrease at elevated temperatures and can range from at least 1.46 to temperatures below the disclosed upper limit temperature for the index of refraction at room temperature. In certain embodiments, the refractive index of the polymer substrate is reduced by 0.1 or less at elevated temperatures compared to the refractive index of the polymer substrate at room temperature.

As mentioned above, not only the index of refraction of the material at room temperature, but also the coefficient of expansion of the material influences which material should be selected for each layer. For example, a solid material, eg, a non-absorbent material 160 in its final state, has a much lower coefficient of expansion than, for example, silicone, and thus has a much smaller change in index of refraction as a function of temperature. Thus, changes in temperature have a greater effect on the refractive index of the polymer substrate 180 than in the non-absorbent material 160 in the embodiments described herein.

In certain embodiments, the micron-sized porous particles 150 are glass formed from any material, including porous silica particles, or any other suitable material having a refractive index less than that of the polymer substrate 180. It may contain bead particles. In one exemplary embodiment, the micron-sized porous particles 150 may be porous silica. A non-limiting example of micron-sized porous particles 150 of non-glass beads is micron-sized porous magnesium fluoride particles.

The lower limit diameter of the micron-sized porous particles 150 must be large enough to have a sufficient amount of material containing submicron pores 165 so that sufficient levels of light scattering can be achieved. .. Conversely, the upper diameter of the micron-sized porous particles 150 must be small enough to keep the optically functional layer as thin as possible. In certain embodiments, the micron-sized porous particles 150 can have a diameter greater than the thickness of the optically functional layer. In certain embodiments, the micron-sized porous particles 150 can have diameters in the range of 3 μm to 700 μm. In certain embodiments, the micron-sized porous particles 150 can have diameters in the range of 3 μm to 150 μm. In certain embodiments, the micron-sized porous particles 150 can have diameters in the range of 50 μm to 150 μm. In certain embodiments, the micron-sized porous particles 150 can have diameters in the range of 3 μm to 50 μm. In certain embodiments, the micron-sized porous particles 150 can have diameters in the range of 10 μm to 50 μm. In certain embodiments, the micron-sized porous particles 150 can have diameters in the range of 10 μm to 100 μm. In certain exemplary embodiments, the micron-sized porous particles 150 may have a diameter of 50 μm. In particular, the strongest effect can be observed with the largest particles, but the thickness of the optical functional layer 105 must also be considered.

With respect to the packing density of the micron-sized porous particles 150 in the optically functional layer, as much as possible in the thinnest possible layer (the preferred layer thickness can be 50 μm, up to 100 μm, up to 200 μm, or more). It is preferably as large as possible so that more scattering can be obtained. In one embodiment, the random filling limit for monodisperse spheres is 64 vol%. When a bimodal distribution is used, the voids between the micron-sized porous particles 150 may be filled with the smaller size micron-sized porous particles 150, with a maximum filling rate of, for example 70% or Increase up to 80%. In embodiments where the micron-sized porous particles 150 used are not monodisperse or completely monodisperse, a packing volume fraction between 40% and 55% is reached. Lower packing densities are possible, but it may also require a reduction in the off-state whitening effect and an increase in layer thickness.

In certain embodiments, the size of the submicron pores 165 of the micron-sized porous particles 150 can have diameters in the range of 50-400 nm. In one exemplary embodiment, the submicron pore 165 has a diameter of 200 nm. In some embodiments, the submicron pores 165 have a diameter of 100 nm.

In certain embodiments, the volume occupied by the sub-micron pore 165 is in the range of about 0.6cm ³ /g~1.5cm ³ / g with respect to grams of micron-sized porous particles 150. In some embodiments, the volume occupied by the sub-micron pore 165 is in the range of about 0.8cm ³ /g~1.2cm ³ / g with respect to the porous particles 150 micron size. In one exemplary embodiment, the volume occupied by the submicron pores 165 is about 0.9 cm ³ / g for micron-sized porous particles 150. The volume occupied by the submicron pores 165 in the optically functional porous structure 105 is at least the materials used and their respective properties, the micron-sized porous required for optimal light scattering at room temperature. Depending on the number of particles 150 and the integrity of the optically functional porous structure 105, it may vary outside the given range.

In certain embodiments, depending on the pore size, surface area to pore volume can be about 10m ² / g~40m ² / g. The surface area relative to the pore volume occupied by the submicron pores 165 in the optically functional porous structure 105 is at least the materials used and their respective properties, the micron size required for optimal light scattering at room temperature. Depending on the number of the porous particles 150 of the, and the integrity of the optically functional porous structure 105, it may vary outside the given range.

In the example where the porous non-absorbent material 160 forms a mesh slab, the non-absorbent material 160 (shown in FIG. 1C), the material has a refractive index lower than that of the porous silica particles or polymer substrate 180. It may be formed from any material, including any other suitable material having. For applications in LEDs, the non-absorbent material 160 should be stable at high luminous flux, temperature, and humidity. In certain embodiments, inorganic materials are preferred. In certain exemplary embodiments, the mesh slab of the porous non-absorbent material 160 may be formed from porous silica.

Figures 3A and 3B show optics consisting of a mixture of silicone as polymer substrate 180 (also shown in Figures 1B and 2) and porous silica as micron-sized porous particles 150 (also shown in Figures 1B and 2). It is a microscopic image of a droplet of a porous structure 105 that functions effectively. The mixture was prepared by combining the solvent, silicone, and porous silica together to form droplets. After mixing, the solvent was evaporated and the droplets were cured at 150 ° C to form the optically functional material 105. Micron-sized porous silica particles are dispersed throughout each droplet of optically functional material 105, and the submicron pores 165 of the micron-sized porous silica particles (shown in FIG. 2) Filled with silicone.

The image in Figure 3A represents a droplet sample at 25 ° C. Porous silica particles are represented by a plurality of small particles within the droplet itself. At this temperature, the silicone-added porous silica particles are due, at least in part, due to the difference in refractive index between the porous silica and the silicone that fills the submicron pores 165 (shown in FIG. 2). , Scatters white light.

The image in Figure 3B represents a droplet sample at 200 ° C. At this temperature, the silicone-added porous silica particles scatter less white light than the silicone-added porous silica particles observed at 25 ° C. This is due, at least in part, to the reduction of the index of refraction difference between the index of refraction of porous silica and the index of refraction of silicone at high temperatures.

In one embodiment, the effect of using a silicone having a refractive index different from that of other silicones is evaluated while keeping the temperature constant. Micron-sized porous particles 150 consisting of porous silica beads with a diameter of 25 μm to 40 μm and an average submicron pore size of about 200 nm are dispersed in silicone with a refractive index of 1.56 and scatter light at 25 ° C. An optically functional layer having a thickness of 200 μm having a porous structure was formed. When silicone with a refractive index of 1.46, which is close to the refractive index of porous silica, was substituted, there was no detectable light scattering at 25 ° C. (Data not shown.) This effect can be attributed, at least in part, to a reduction in the index of refraction difference between the materials, where the index of refraction difference between the materials was almost zero.

FIG. 4 shows an optically functional porous structure 105 (shown in FIGS. 1A, 1B, and 1C) containing 25% by weight of porous silica beads having a diameter of 50 μm as micron-sized porous particles 150. Show a quantitative evaluation of ability. Submicron pores 165 (shown in FIG. 2) of porous silica beads with an effective pore size of 100 nm are filled with high refractive index silicone as the polymer substrate 180 (shown in FIGS. 1B and 2) and are a function of temperature. Scatter light as. Direct transmission of light with a wavelength of 450 nm and an intensity of 10 W / cm ² is transmitted at various temperatures through a layer of optically functional porous structure 105 containing micron-sized porous silica beads throughout. Will be done. The intensity of transmitted light detected at each temperature is measured. In one embodiment, the laser spot on the layer is 1.3 mm in diameter and the detection of light is through the use of an integrating sphere with a 5 mm aperture located about 2 cm behind the layer, aligned with the 450 nm laser. It is done.

The percentage of light that has passed through the layer at the first temperature (ie, 30 ° C) is 0.75%. This intensity is determined and normalized to itself to be 1.0 units as shown in Figure 4. The intensity of the transmitted light detected at the second temperature is determined, which is normalized to the intensity of the light detected at the first temperature. The intensity of transmitted light is measured at each subsequent temperature at which the layer is exposed and normalized to the intensity of transmitted light detected at the first temperature. As shown in FIG. 4, the intensity of the light transmitted through the layer increases as the temperature rises, and the intensity of the transmitted light when the layer is exposed to 200 ° C is exposed to 30 ° C. It is 30 times as high as the intensity of the transmitted light. Even at temperatures below 200 ° C, the intensity of transmitted light increases as the temperature rises above 70 ° C to 80 ° C. For example, at 130 ° C, the intensity of transmitted light passing through the layer is about 10 times higher than the intensity of light transmitted at 30 ° C in this embodiment.

Apart from the change in index of refraction, it is often observed that air voids are present inside the micron-sized porous particles 150. FIG. 5 is an optical microscope image showing the presence of air voids 185 (indicated by the thicker arrow) within the micron-sized porous particles 150. These are visible under the microscope as internal structures within the micron-sized porous particles 150.

The air void 185 also contributes to the scattering of light from the optically functional layer 105 made of the materials described herein. Air voids 185 may form as a result of incomplete filling of the submicron pores 165 with the polymer substrate 180 (ie, silicone), for example, curing of the silicone inside the submicron pores 165 and subsequent cooling. It can also be formed at the time of. When the silicone cures at high temperatures (ie, 150 ° C), it expands considerably due to its high coefficient of expansion. As the temperature drops, the silicone shrinks again, and inadequately crosslinked silicone may be injected back into the micron-sized porous particles 150, and the silicone in the micron-sized porous particles 150. Can be stressed and exhibit local detachment or cohesive failure. When the layer is reheated, for example by switching on the LED, the silicone expands again, filling the air void 185 completely or partially and the air void disappearing. The net effect is to increase the switching amplitude of the light output between the samples at two different temperatures.

As mentioned above, the submicron pores formed from the micron-sized porous particles 150 with submicron pores 165, or the non-absorbent material 160 described herein for whiteness in the off state, The mesh slab having may be used for other purposes. For example, color point control, filament lamps, switchable lenses.

Regarding color point control, a color point shift can be observed as the temperature rises. For example, increasing the drive current leads can raise the temperature of the LED, thereby shifting the color point of the LED light to a cooler light color. Conversely, reducing the drive current reed lowers the temperature, which can shift the color point of the LED light to a warmer color. This is because, at least in part, each color of light has a different ability to scatter light. For example, since blue light is scattered more strongly than red light, light scattering decreases as the temperature rises in the aforementioned layers, and relatively more blue light is emitted. In this embodiment, the color spots shift to cooler white light. Conversely, as the temperature decreases, light scattering increases and relatively less blue light is emitted. In this embodiment, the color spots shift to warmer white light.

In one embodiment, porous silica as micron-sized porous particles 150 (shown in FIGS. 1B and 2) dispersed in silicone as polymer substrate 180 (shown in FIGS. 1B and 2). The containing layer was deposited on a 1202 COB chip. This chip is a light source that provides bright light and can be used in place of LED light sources. The 1202 COB chip write, including the additional layers described herein, was exposed to a 10 mAmp drive current lead associated with a temperature of approximately 25 ° C. Increasing the drive current lead to 400 mAmp caused a corresponding temperature rise to 85 ° C. As shown in FIG. 6, a shift of color points occurred along the u'axis, which mainly represents the color of red light. More red light was detected at 25 ° C and less red light was detected at 85 ° C.

Figure 6 also shows a relatively smaller shift along the v'axis, which primarily represents the green light color, when the drive current leads are shifted from 10 mAmp to 400 mAmp. However, not only is the magnitude of the shift along the v'axis smaller than the magnitude of the shift along the u'axis, but also the extent to which changes in green light detection affect warmer light pairs and colder light. The equivalent shift in red light detection is much less than the degree to which it affects warmer light pairs and colder light.

Although not shown in this figure, the degree of shift from more red light to less red light, corresponding to the shift from warmer to colder light, was dispersed in the silicone. A micron-sized porous particle layer containing porous silica is significantly increased when placed on the 1202 COB chip light.

FIG. 7 is a flow diagram 700 of a method of adjusting light scattering using an optically functional porous structure 105 containing a plurality of submicron pores 165 (shown in FIGS. 1B and 2). In certain embodiments, the method 700 has submicron pores 165 (shown in FIG. 2) formed within the non-absorbent material 160 (shown in FIGS. 1B, 1C, and 2) and polymer substrate 180 (shown in FIG. 2). Includes step 705 to fill in (shown in 2). In each case, the submicron pores 165 are filled with the polymer substrate 180 to form an interface 170 (shown in FIG. 2) between the polymer substrate 180 and the non-absorbent material 160 in the form of the submicron pores 165. Examples of the properties and characteristics of non-absorbent material 160, micron-sized porous particles 150, mesh slab networks, multiple submicron pores 165, and polymer substrate 180 are described above. Based on the properties and structure of the material, light scattering can be adjusted using a non-absorbent material structure 160 containing submicron size pores 165 filled with the polymeric substrate 180 described herein. ..

Once the submicron pores 165 are filled with the polymer substrate 180 (705), the optically functional porous structure 105 is exposed to light at a first temperature (710). Due to the intrinsic properties and tissue structure of the optically functional porous layer 105, including the refractive index difference between the non-absorbent material 160 and the polymer substrate that fills the submicron pores 165, at the first temperature Light scattering occurs.

To adjust or change the relative amount of light scattering in response to exposure to light, the temperature is changed (715) and the optically functional porous structure 105 is exposed to light at a second temperature (720). .. Since the difference in refractive index between the non-absorbent material 160 and the polymer substrate that fills the submicron pores 165 changes as a function of temperature, the amount of light scattering that occurs at the second temperature changes.

In certain embodiments, the refractive index of the polymer substrate 180 decreases with increasing temperature. This reduces light scattering as long as the index of refraction of the polymer substrate 180 is greater than the index of refraction of the non-absorbent material 160. In one embodiment, SiO ₂ is a non-absorbent material 160 that forms micron-sized porous particles 150, and silicone is used as a polymer substrate 180 that fills submicron pores 165 (shown in FIG. 2). To. In this example, the index of refraction of silicone is lower than the index of refraction of _{SiO 2 , so the difference in index of refraction between the index of Refraction of SiO 2 and} the index of refraction of silicone increases with increasing temperature, causing light scattering. It leads to an increase. In one embodiment, the polymer substrate 180 is polydimethylsiloxane (PDMS), which is a low index silicone.

In certain embodiments, the light is further regulated beyond the index difference through the presence of air voids 185 (shown in FIG. 5) in the micron-sized porous particles 150, as described herein. Can be As the temperature rises, the silicone cures and has a high coefficient of expansion and therefore expands considerably. As the temperature drops, the silicone shrinks again and air voids 185 may form if insufficient crosslinked silicone may be reinjected into the micron-sized porous particles 150, micron-sized. The remaining silicone in the porous particles 150 is stressed and may exhibit local exfoliation or cohesive failure. This can contribute to the scattering of light from the layers made of the materials described herein, in addition to the difference in refractive index between the materials within the micron-sized porous particles 150. When the layer is reheated, for example by switching on the LED, the silicone expands again and fills the air void 185 completely or partially. The net effect is an increase in switching swing.

In certain embodiments, an optically functional porous structure 105 is used to shift the color point of the LED light during operation when the LED light is on, as described herein. You may. This can happen when the first temperature of the LED changes to the second temperature. At the second temperature of the LED (the second temperature is greater than the first temperature), light scattering may be reduced, in which case, for example, red light is proportional to blue light scattering. Allows for a greater reduction. In this case, the LED color point shifts to colder white light as more blue light is emitted.

In certain embodiments, this method may be used in other applications, such as filament lamps and switchable lenses. This method may be used in applications where an increase in temperature increases the difference in refractive index between materials and increases light scattering.

Having described the embodiments in detail, one of ordinary skill in the art will appreciate that the embodiments described herein may be modified without departing from the spirit of the concept of the present invention. Therefore, the scope of the invention is not intended to be limited to the particular embodiments illustrated and described.

Claims (15)

With a light emitting semiconductor device that emits primary light during operation;
With a wavelength conversion structure arranged on the light emitting semiconductor structure and configured to absorb at least a part of the primary light and respond to emit secondary light having a wavelength longer than that of the primary light;
Arranged on the wavelength conversion structure on the opposite side of the light emitting semiconductor device, formed from a material substantially transparent to the primary and secondary light, having a first refractive index, submicron pores. With a porous structure including;
It has a polymer that fills the submicron pores in the porous structure and has a second refractive index different from the first refractive index at 25 ° C.
Luminescent device. The light emission according to claim 1, wherein in the operation of the light emitting device, the secondary light and optionally a part of the primary light pass through the porous structure to form an optical output from the light emitting device. device. The light emitting device according to claim 2, wherein the light output looks white to a human observer. At 25 ° C., when the light emitting device is off, the polymer forms an optical scattering interface with the porous structure, and the porous structure is under external illumination of white light. The light emitting device according to claim 1, wherein the structure is made to appear white to a human observer. The light emitting device according to claim 1, wherein the second refractive index is larger than the first refractive index. The light emitting device according to claim 1, wherein the first refractive index is larger than the second refractive index. The polymer forms an optical scattering interface with the porous structure that scatters primary and secondary light;
The magnitude of the difference between the first refractive index and the second refractive index decreases as the temperature of the porous structure rises during the operation of the light emitting device;
As a result, during the operation of the light emitting device, as the temperature of the porous structure rises, the scattering of the primary light and the secondary light by the scattering interface decreases.
The light emitting device according to claim 1. During operation of the light emitting device, secondary light and optionally a portion of the primary light pass through the porous structure to form a light output from the light emitting device;
The light output looks white to a human observer;
As the temperature of the porous structure rises during the operation of the light emitting device, the color point of the light output shifts to a colder color.
The light emitting device according to claim 6. The polymer forms an optical scattering interface with the porous structure that scatters primary and secondary light;
The magnitude of the difference between the first index of refraction and the second index of refraction increases as the temperature of the porous structure rises during the operation of the light emitting device;
As a result, during the operation of the light emitting device, as the temperature of the porous structure rises, the scattering of the primary light and the secondary light by the scattering interface increases.
The light emitting device according to claim 1. The light emitting device according to claim 1, wherein the porous structure includes micron-sized particles including the submicron pores. The light emitting device according to claim 1, wherein the porous structure includes a mesh slab of a porous dielectric material containing the pores. During operation of the light emitting device, secondary light and optionally a portion of the primary light pass through the porous structure to form a light output from the light emitting device;
The light output looks white to a human observer;
At 25 ° C. with the light emitting device off, the polymer forms an optical scattering interface with the porous structure, and the porous structure is under external illumination of white light. Make the structure appear white to human observers,
The light emitting device according to claim 1. The second refractive index is larger than the first refractive index;
The polymer forms an optical scattering interface with the porous structure that scatters primary and secondary light;
The magnitude of the difference between the first refractive index and the second refractive index decreases as the temperature of the porous structure rises during the operation of the light emitting device;
As a result, during the operation of the light emitting device, as the temperature of the porous structure rises, the scattering of the primary light and the secondary light by the scattering interface decreases.
The light emitting device according to claim 12. The light emitting device according to claim 13, wherein the color point of the light output shifts to a colder color as the temperature of the porous structure rises during the operation of the light emitting device. The second refractive index is smaller than the first refractive index;
The polymer forms an optical scattering interface with the porous structure that scatters primary and secondary light;
The magnitude of the difference between the first index of refraction and the second index of refraction increases as the temperature of the porous structure rises during the operation of the light emitting device;
As a result, during the operation of the light emitting device, as the temperature of the porous structure rises, the scattering of the primary light and the secondary light by the scattering interface increases.
The light emitting device according to claim 12.

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