RU2809352C1 - Pixel structure for electronic display and electronic device containing such display - Google Patents

Abstract

FIELD: pixel structures.

SUBSTANCE: invention relates to a pixel structure for an electronic display, the pixel structure comprising at least one light-emitting diode (LED) emitter and at least one wavelength conversion unit disposed on a substrate. The result is achieved in that the pixel structure (1) contains a substrate (3), at least one LED emitter (4) located on the substrate (3), and at least one wavelength conversion unit (5) located on the substrate (3) next to the LED emitter (4). The LED emitter (4) is configured to emit emission radiation (R1), wherein the emission radiation (R1) is within the emission wavelength range and is emitted in one or more emission directions (D2, …, Dn) within the main emission plane (P1). The wavelength conversion unit (5) is configured to convert emission radiation (R1) into converted radiation (R2) within a converted wavelength range, wherein the converted wavelength range is different from the emission wavelength range. The converted radiation (R2) propagates from the wavelength conversion unit in a main conversion direction (D1) perpendicular to the plane of the main radiation (P1), wherein the main conversion direction (D1) is, for example, towards the user of an electronic device having an electronic display with at least one such pixel structure. Each pixel structure may contain six LED emitters (4), wherein the first pair of LED emitters (4) is operatively connected to the first wavelength conversion block (5), the second pair of LED emitters (4) is operatively connected to the second wavelength conversion block (5) and the third pair of LED emitters, each LED emitter of the third pair emits emission radiation directly in the main conversion direction (D1) or is operatively connected to the radiation dispersion unit 6 or the additional wavelength conversion unit 5.

EFFECT: increasing the luminous efficiency of the pixel structure of an electronic display.

26 cl, 21 dwg

Description

FIELD OF TECHNOLOGY TO WHICH THE INVENTION RELATES

The disclosure relates to a pixel structure for an electronic display, the pixel structure comprising at least one light-emitting diode (LED) emitter and at least one wavelength conversion unit disposed on a substrate. The disclosure also relates to an electronic device comprising an electronic display having a user interface surface and at least one such pixel structure.

BACKGROUND OF THE ART

Micro light-emitting diodes, known as Micro-LED, mLED or uLED, are used in displays for mobile devices such as smartphones, TVs, PCs, tablets, smart glasses, wearables and many other consumer and industrial devices. Micro-LED (micro-LED) typically consists of a large number of small LED emitters and a promising future display technology with many potential advantages, such as high brightness and contrast, high energy efficiency, wide color gamut, form factor flexibility, and various feature integrations.

Micro-LED display technology mainly uses one of two circuits: direct emission circuit or color conversion circuit.

In a direct emission design, each individual LED emitter emits radiation in the red, green or blue spectral range. Such direct-emitting solutions are very expensive to produce because each pixel structure requires one red light emitter, one green light emitter and one blue light emitter, so a display with a resolution of about 8 million pixels would require about 24 million LED emitters .

The color conversion circuit uses only LED emitters that emit radiation, for example, in the blue spectral range. LED emitter chips are usually based on the GaN (gallium nitride) material system. Blue-to-red and blue-to-green conversion blocks are located on top of the corresponding LED pixels and are used to convert blue spectral range radiation from some LED emitters into red spectral range radiation or green spectral range radiation, respectively. Compared to the direct emitting circuit, the color conversion circuit is simpler and cheaper to manufacture since only one type of LED emitter is required.

Radiation in the blue spectral range is partially absorbed by the conversion unit, and the absorption decreases exponentially to the first order. Ideally, the conversion unit should absorb almost all blue light to maintain high energy efficiency and minimize blue leakage from the conversion units.

In addition, the conversion unit must have area dimensions similar to those of the LED emitter. The height of the conversion block is preferably larger to form small pillars on top of the small sized LED emitters. This facilitates the propagation of blue spectral range radiation through the conversion unit over a greater distance and, therefore, facilitates absorption.

However, in practice, the conversion material must have a thickness of one or several hundred microns in order to absorb most of the blue spectral range radiation. This gives a very large aspect ratio of 100 µm: 3 µm or more between the LED emitter and the conversion unit, which is not easily achieved using microstructuring techniques. Another problem is that the green or red spectral range radiation must also pass through the conversion unit and may also be slightly absorbed by the conversion unit material (self-absorption). This reduces the efficiency of the device.

In addition, such multilayer structures have poor heat dissipation because heat from the conversion unit must penetrate through the underlying LED emitter chip. This further heats the LED emitter chip and shortens the life of the pixel structure. The stacking also makes it difficult to integrate other functional optical elements such as lenses.

SUMMARY OF THE INVENTION

The goal is to provide an improved micro-LED pixel structure. The above and other objectives are achieved through the use of independent clause(s) features. Additional forms of implementation are obvious from the dependent claims, description and figures.

According to a first aspect, a pixel structure is provided for an electronic display, wherein the pixel structure comprises a substrate, at least one LED emitter disposed on the substrate, wherein the LED emitter is configured to emit emissive radiation, wherein the emissive radiation is within a wavelength range of the emission and emitted in one or more radiation directions within the main emission plane, at least one wavelength conversion unit located on a substrate adjacent to the LED emitter, wherein the wavelength conversion unit is configured to convert the emitted radiation into converted radiation, the converted radiation of the located within the converted wavelength range and propagating from the wavelength conversion unit in the main conversion direction perpendicular to the main emission plane, wherein the converted wavelength range differs from the emission wavelength range.

This arrangement allows for a pixel structure with a significantly reduced height due to the fact that the conversion units are located adjacent to the LED emitters, rather than being stacked on top of the LED emitters. This type of distribution improves the heat dissipation of the structure, which in turn increases the service life of the pixel structure. In addition, since the conversion radiation travels substantially perpendicular to the emitted radiation, the risk of emitted radiation, for example, in the blue spectral range, leaking in the direction of the conversion radiation and therefore affecting the conversion radiation, for example, in the red spectral range or the green spectral range, is significantly reduced . Also, higher efficiency is achieved due to the direct propagation of converted radiation from the conversion unit, without interaction and reabsorption of the converted radiation by other conversion units.

In a possible embodiment of the first aspect, the main emission plane is parallel to the main plane of the substrate, the LED emitter(s) and the wavelength conversion unit(s) are distributed in the main emission plane.

In yet another possible embodiment of the first aspect, the wavelength range of the emission is one of the blue spectral range or the ultraviolet spectral range, and when the pixel structure includes at least two LED emitters, the LED emitters are configured to emit radiation having the same wavelength. By using only one type of LED emitter, manufacturing the pixel structure becomes much easier and cheaper due to having only one main component instead of, for example, three different and equally important main components.

In yet another possible embodiment of the first aspect, the pixel structure includes at least two wavelength conversion units, each wavelength conversion unit configured to convert emitted radiation in a wavelength range of the emitted radiation into converted radiation in one of a plurality of different converted wavelength ranges, providing conversion of emitted radiation of the same wavelength into converted radiation in any several different wavelength ranges.

In yet another possible embodiment of the first aspect, the at least one first wavelength conversion unit is configured to convert the emitted radiation into a first converted radiation within the first converted wavelength range, and

at least one second wavelength conversion unit is configured to convert the emitted radiation into a second converted radiation located in a second converted wavelength range, wherein the second converted wavelength range is at least partially different from the first converted wavelength range. This allows a single pixel structure to emit radiation in several different wavelength ranges simultaneously and in the same direction,

In yet another possible embodiment of the first aspect, the first converted wavelength range is within the red spectral range and the second converted wavelength range is within the green spectral range, facilitating the creation of a commonly used RGB pixel structure.

In yet another possible embodiment of the first aspect, the LED emitter is configured to emit emission radiation only in the main emission plane, or emission radiation or at least one portion of the emission radiation that is emitted in the main emission plane by the LED emitter is converted into converted radiation in wavelength conversion block. This allows the pixel structure to have as low a height as possible, the height visible in the main conversion direction, which in turn increases the freedom to place the LED emitter at any suitable location within the electronic device, while also freeing up space for other components.

In another possible embodiment of the first aspect, when the pixel structure includes at least two LED emitters, at least one of the LED emitters is configured to emit emissive radiation in the main conversion direction, which allows, for example, to emit emissive radiation in the blue spectral range directly to the user interface without conversion or redirection.

In yet another possible embodiment of the first aspect, the pixel structure further comprises at least one radiation dispersion unit located on a substrate adjacent to the LED emitter, wherein the diffusion unit is configured to redirect emission radiation propagating in the main emission plane to the main conversion direction, allowing part of the emission radiation to be redirected, providing more freedom regarding the placement of the LED emitter inside the electronic device.

In yet another possible embodiment of the first aspect, the wavelength conversion unit comprises a wavelength conversion material, the wavelength conversion material preferably comprising a matrix material and wavelength conversion particles distributed in the matrix material.

In another possible form of implementation of the first aspect, the wavelength conversion particles are quantum dots or phosphorus material.

In yet another possible embodiment of the first aspect, the wavelength conversion unit comprises at least one barrier extending along the periphery of the wavelength conversion unit in a primary conversion direction, wherein the barrier is configured to extend through an absorption path of the wavelength conversion unit, an absorption path extending in the main emission plane, emission radiation propagating along the absorption path, and the conversion of emission radiation into converted radiation occurring simultaneously with propagation. The barrier allows individual pixel structures to be distributed in smaller pitches because the barrier helps reduce or even avoid optical crosstalk between adjacent pixel structures, even if they are located close to each other. In addition, the barrier can serve as a support surface for reflectors used to redirect radiation.

In yet another possible embodiment of the first aspect, the pixel structure further comprises at least one wall reflector located on the surface of the barrier extending at least partially in the main conversion direction, wherein the wall reflector is configured to redirect emission radiation propagating along the absorption path, so that the absorption path of the wavelength conversion unit is within the main emission plane, allowing as much emission radiation as possible to be absorbed and therefore converted by the wavelength conversion unit.

In yet another possible form of implementation of the first aspect, the pixel structure includes at least one bottom reflector located between the wavelength conversion unit and the substrate, wherein the bottom reflector extends at least partially parallel to the main emission plane and is configured to redirect the converted radiation propagating internally wavelength conversion unit in the main conversion direction, which helps to increase the efficiency of the output radiation.

In yet another possible embodiment of the first aspect, at least one of the wall reflector and the bottom reflector extends at an angle to the primary conversion direction, allowing emission radiation and/or converted radiation to be redirected toward a more useful direction when it hits the reflector.

In yet another possible form of implementation of the first aspect, the wavelength conversion unit includes a waveguide structure configured to guide emission radiation as it propagates within the wavelength conversion unit, allowing the wavelength conversion unit to be adapted to the form factor of the electronic device as well as surrounding components.

In yet another possible embodiment of the first aspect, the wavelength conversion unit is configured such that at least one surface of the wavelength conversion unit extends at an angle to a major plane of the substrate, with the surface facing away from the substrate and the surface extending adjacent to the substrate. This solution helps prevent total internal reflection from occurring since the angle can be adjusted to ensure that as much of the converted radiation as possible is propagated in the primary conversion direction out of the wavelength conversion unit.

In yet another possible embodiment of the first aspect, one of the wavelength conversion unit and the substrate tapers as it extends along the main emission plane or the main plane of the substrate, allowing the surface of the wavelength conversion unit to be tilted by the simplest means possible.

In yet another possible embodiment of the first aspect, the pixel further comprises at least one optical functional element located on a surface of the wavelength conversion block facing away from the substrate, wherein the optical functional element is one of the elements located on top of the surface of the wavelength conversion block waves and is an integral part of the surface of the wavelength conversion block.

In yet another possible embodiment of the first aspect, the optical functional element is at least one of a refractive lens and a diffractive lens, for example improving the focusing of the converted radiation.

In yet another possible embodiment of the first aspect, the optical functional element is a surface structure, preferably one of surface gratings, rough surfaces, surface coatings or micropillars, increasing the output efficiency of the pixel structure.

In yet another possible embodiment of the first aspect, several of a plurality of LED emitters are operatively coupled to a single wavelength conversion unit, wherein the LED emitters are configured to simultaneously and independently emit emission radiation to the wavelength conversion unit. This provides redundancy that gives better results and also ensures that if one of the LED emitters fails, the pixel structure will still function as intended without any dark areas.

In yet another possible form of implementation of the first aspect, the pixel structure comprises

six LED emitters, wherein the first pair of LED emitters is operatively connected to the first wavelength conversion unit, wherein the first wavelength conversion unit is configured to convert emission radiation from the first pair of LED emitters into the first converted radiation,

a second pair of LED emitters is operatively coupled to a second wavelength conversion unit, the second wavelength conversion unit is configured to convert emission radiation from the second pair of LED emitters into a second converted radiation, and optionally, each LED emitter of the third pair of LED emitters is operatively coupled to one unit radiation scattering or one additional wavelength conversion unit, wherein the additional wavelength conversion units are configured to convert the emission radiation of the third pair of LED emitters into the third converted radiation. This provides a pixel structure capable of emitting radiation at three wavelengths simultaneously and redundantly.

In yet another possible embodiment of the first aspect, the pixel structure further comprises a control arrangement for adjusting the overall output of the converted radiation, wherein the control comprises pulse width modulation and adjustment of the drive current of the LED emitter(s). The control layout allows, for example, the built-in redundancy to be used appropriately, for example to control pairs of LED emitters so that they either provide the best result, or so that one LED emitter compensates for the failure of the other LED emitter of the pair.

According to a second aspect, there is provided an electronic device comprising an electronic display having a user interface surface and at least one pixel structure as described above. The pixel structure is configured to emit emission radiation of one emission wavelength in multiple emission directions within a main emission plane, wherein the main emission plane extends parallel to the user interface surface to convert at least a portion of the emission radiation into at least a converted emission radiation one converted wavelength, wherein the converted wavelength differs from the emission wavelength,

and direct the converted radiation in the main conversion direction perpendicular to the main emission plane and the user interface surface.

This pixel structure has a significantly reduced height, leaving free space inside the electronic device for other components or providing additional freedom to the device form factor. In addition, the electronic display will have an increased service life due to improved heat dissipation of the pixel structures. In addition, since the fill factor of the pixel structure in the lateral directions, i.e., in directions inside the main emission plane, is low for many electronic devices, this structure leaves a lot of free space for placing conversion units, while still providing a sufficient degree of freedom for additional components or structural improvements.

In a possible embodiment of the second aspect, the electronic device comprises a plurality of identical pixel structures, wherein the pixel structures are distributed in a primary emission plane in the form of a two-dimensional pattern, the two-dimensional pattern comprising rows of pixel structures and columns of pixel structures, the rows extending in parallel and intersecting the columns at perpendicular angles, wherein the number of pixel structures in a separate line does not depend on the number of pixel structures in the adjacent line, and

the number of pixel structures in a particular column is independent of the number of pixel structures in an adjacent column, the distribution of pixel structures allows the number of pixel structures in the region containing the 2D pattern to be maximized when needed, and a simpler structure when maximization is not needed.

In yet another possible form of implementing the second aspect, a plurality of pixel structures are distributed with a first step in a two-dimensional pattern such that at least the first emissive direction of an individual pixel structure matches the corresponding first emission direction of an adjacent pixel structure, sufficient for, for example, long-range display.

In yet another possible form of implementing the second aspect, a plurality of pixel structures are distributed with a second pitch in a two-dimensional pattern such that at least the first emissive emission direction of an individual pixel structure does not coincide with the corresponding first emission direction of an adjacent pixel structure, allowing the number of pixel structures to be maximized in an area containing a two-dimensional pattern, which is necessary, for example, for a near-view display.

In yet another possible form of implementing the second aspect, the pixel structures are separated by a first step, and the pixel structures match in at least one of the column direction and the row direction, such that the absorption path(s) of the wavelength conversion block(s) of the individual pixel structure coincides with the corresponding by(s) absorption of adjacent pixel structure.

In yet another possible form of implementing the second aspect, the pixel structures are separated by a second step, and each pixel structure is rotated through an angle in the main emission plane, such that the absorption path(s) of the wavelength conversion block(s) of the individual pixel structure do not coincide with the corresponding (and) by(s) absorption of adjacent pixel structure, wherein the misalignment represents a lateral displacement and/or angular displacement of the orientation of each pixel structure.

In yet another possible embodiment of the second aspect, pixel structures in a particular row are offset in the column direction relative to pixel structures in an adjacent row, and/or pixel structures in a particular column are offset in the row direction relative to pixel structures in an adjacent column.

In yet another possible form of implementation of the second aspect, the absorption path length is fixed, the length is 10-500 µm, preferably <20 µm, and the second pitch is 20-150 µm, preferably 30-80 µm, in display applications configured such that the distance between the user's eye and the user interface surface (2a) is <1 m, and the second pitch is ≥70 µm, preferably ≥100 µm, in display applications configured such that the corresponding distance between the user's eye and the user interface surface (2a) is ≥ 0.5 m.

In yet another possible form of implementation of the second aspect, the converted radiation is propagated in the main conversion direction, towards the surface of the user interface, without applying radiation filtering, which reduces the number of components required, the space required for the pixel structure, as well as the number of error sources.

These and other aspects will be apparent from the embodiments described below.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following detailed portion of the present disclosure, aspects, embodiments and implementations will be explained in more detail with reference to exemplary embodiments shown in the drawings, in which:

Fig. 1a and 1b show a side and top view of a prior art pixel structure;

FIGS. 2a and 2b show a side and top view of a pixel structure in accordance with an embodiment of the present invention;

FIGS. 3a and 3b show top and side views of a pixel structure in accordance with an embodiment of the present invention;

Fig. 4 to 9 show partial cross-sections of pixel structures in accordance with various embodiments of the present invention;

Fig. 10 shows a schematic side view of an electronic device containing pixel structures in accordance with embodiments of the present invention;

Fig. 11-18 show schematic plan views of a distribution of pixel structures for an electronic display.

DETAILED DESCRIPTION

Fig. 1a and 1b show side and top views of a color conversion pixel structure in accordance with the prior art. Several LED emitters 4 emit emission radiation R1, for example in the blue spectral range, in the direction D1. Conversion units 5 located on top of the LED emitters 4 absorb the emission radiation R1, convert it into converted radiation R2 and then emit the converted radiation R2 also in the direction D1.

In fig. 2a and 2b are side and top views of one embodiment of a color conversion pixel structure in accordance with the present invention. Fig. 3a-9 show additional embodiments of color conversion pixel structures. These color conversion pixel structures are to be used in the electronic display 2, the display comprising any desired number of identical pixel structures.

The pixel structure 1 contains, as shown in FIG. 2a, a substrate 3 configured to carry at least one LED emitter 4 and at least one wavelength conversion unit 5 located on the substrate 3 adjacent to the LED emitter 4. LED emitter 4, wavelength conversion unit 5 and additional components, mentioned below can be connected to the substrate 3 by soldering, adhesive or nanowires. The substrate 3 may comprise one complete substrate or a plurality of matching partial substrates and extends at least partially within one main substrate plane P2. The substrate 3 may have a partially stepped configuration, but each pixel structure 1 is located in one common plane, so that all of its radiation emitting and radiation converting components coincide along the main emission plane P1. The main emission plane P1 runs parallel to the main plane P2 of the substrate 3, as shown in FIG. 2a, and the LED emitters 4 and wavelength conversion units 5 are distributed in the main emission plane P1. With such a distribution, the wavelength conversion unit 5 may have a height in the main conversion direction D1 of 10 to 100 µm, while the length/width of the wavelength conversion unit 5 may be more than 100 µm, even more than 1000 µm.

One or more LED emitters 4 are arranged on the substrate 3 such that each LED emitter 4 can emit emissive radiation R1 within the main emission plane P1, i.e. from the side through the LED emitter side. The emission light R1 emitted by the LED emitter 4 may be emitted only in the first emission direction D2 or in a plurality of emission directions D2,..., Dn covering part or all of a 360° area around the LED emitter 4. The emission light R1 is also known as pump light.

All of the emission radiation R1 emitted by the plurality of LED emitters 4 is within the same emission wavelength range. The emission wavelength range may be the blue spectral range or the ultraviolet spectral range.

Each wavelength conversion unit 5 is configured to convert emission radiation R1 into converted radiation R2. The converted emission R2 is within a converted wavelength range that is at least partially, preferably completely different from the emission wavelength range. Various wavelength conversion units 5 can convert emission radiation R1 into converted radiation R2 within different ranges of converted radiation, R21, R22. The pixel structure 1 may comprise a plurality of wavelength conversion units 5, each wavelength conversion unit 5 configured to convert emission radiation R1 into converted radiation R2 within one of the plurality of converted wavelength ranges.

In one embodiment, the pixel structure 1 comprises at least one first wavelength conversion unit 5 configured to convert emission radiation R1 into first converted radiation R21 within a first converted wavelength range, such as the red spectral range, and at least one second unit The wavelength conversion 5 is configured to convert the emission radiation R1 into a second converted radiation R22 in a second converted wavelength range, for example, a green spectral range.

In another embodiment, the pixel structure 1 contains wavelength conversion units 5 that convert emission radiation R1 into red converted radiation R21, green converted radiation R22, and yellow converted radiation R23 (not shown). Pixel structure 1 may contain any number of wavelength conversion blocks 5, converting emission radiation R1 into radiation in any number of desired spectral ranges R2, R21, R22, R23, ..., R2n.

The converted radiation R2 propagates from the wavelength conversion unit 5 in the main conversion direction D1 extending substantially perpendicular to the main emission plane P1, that is, through the upper surface of the wavelength conversion unit 5. In other words, the converted radiation R2 propagates in a direction from the substrate 3, for example, to the user interface surface 2a of the electronic device 13 contained in the electronic display 2.

In one embodiment shown in FIG. 4, at least one of the LED emitters 4 is configured to emit emission radiation R1 directly in the main conversion direction D1, i.e. emission radiation R1 retains its direction and wavelength when propagating in the main direction of D1 transformation.

In additional embodiments shown in FIGS. 5-7, the LED emitter(s) 4 are configured to emit emission radiation R1 only in the main emission plane (P1), i.e. not directly in the main conversion direction D1, but laterally on at least one side or all sides of the LED emitter 4 to the wavelength conversion unit 5 or to multiple conversion units 5. The wavelength conversion units 5 can be configured to convert only the emission radiation R1 or parts of the emission radiation R1 that are emitted from one side or all sides of the LED emitter 4 into converted radiation R2.

In yet another embodiment, the pixel structure 1 includes at least one radiation scattering unit 6, as shown in FIG. 5. The radiation dispersion block 6 is located on the substrate 3 adjacent to the LED emitter 4, similar to the layout of the wavelength conversion blocks 5. The dispersion unit 6 is configured to redirect the emission radiation R1, propagating in the main emission plane P1, to the main direction of transformation D1 without conversion, i.e. without changing the wavelength of emission radiation R1. The scattering unit 6 may comprise a polymeric matrix material, such as polymethyl methacrylate (PMMA), with scattering particles distributed within the matrix material. The scattering particles scatter the incoming emission radiation R1 in all directions, and preferably the radiation R1 is directed towards the bottom of the scattering unit 6, i.e. to the substrate 3 is easily redirected to the top of the diffusion unit 6 using, for example, a reflector such as the lower reflector 9 described below. The diffusion block 6 may have a height in the main conversion direction D1 of about 10 to 100 µm, while the length/width of the diffusion block 6 may be more than 100 µm, even more than 1000 µm. Generally, the number of scattering particles is large enough to allow the scattering unit 6 to have a relatively small height.

Each wavelength conversion unit 5 contains a wavelength conversion material. The wavelength conversion material may be a matrix material comprising wavelength conversion particles distributed within the matrix material. The wavelength conversion particles can be quantum dots or phosphorus material.

As shown in FIG. 6, the wavelength conversion unit 5 may include at least one barrier 7 extending along the periphery of the wavelength conversion unit 5 in the main conversion direction D1. The barrier 7 may extend along at least one long edge of the wavelength conversion block 5 (not shown), along one short end of the wavelength conversion block 5, as shown in FIG. 6, or around the long edges and short end of the wavelength conversion block 5 such that the walls of the wavelength conversion block 5 are covered by the barrier 7 in the main conversion direction D1, as shown at least in FIG. 11 and 15. The barrier 7 can be integrated between adjacent pixel structures 1 using nanoimprint technology with a polymer layer or using photolithography of a photosensitive polymer material such as benzocyclobutene (BCB).

The barrier 7 is configured to pass through the absorption path A of the wavelength conversion block 5. The absorption path A passes in the main emission plane P1 in the wavelength conversion block 5. When the emission radiation R1 propagates in the wavelength conversion unit 5, it propagates and is also absorbed along the absorption path A. Absorption and, therefore, conversion of emission radiation R1 into converted radiation R2 occurs simultaneously with propagation, as indicated in Fig. 4 to 9. As the R1 emission propagates along absorption path A, the intensity of the R1 emission decreases, usually exponentially.

The barrier 7 reduces optical crosstalk occurring between adjacent pixel structures 1 and allows the absorption path A of the wavelength conversion unit 5 to pass through at least one wall reflector 8.

In one embodiment, shown in FIG. 6, at least one wall reflector 8 is located on the barrier 7, preferably on a surface of the barrier 7 extending at least partially in the main transformation direction D1. The wall reflector 8 is configured to redirect the emission radiation R1, which propagates along the absorption path A, so that the absorption path A of the wavelength conversion unit 5 passes within the main emission plane P1. This folding of absorption path A, which can be up to 180º from the original emission direction D2,...,Dn, is shown in Fig. eleven.

As shown in FIG. 4-9, at least one lower reflector 9 can be located between the wavelength conversion unit 5 and the substrate 3, preferably on top of the surface of the substrate 3 on which the LED emitters 4 and the wavelength conversion unit 5 are distributed. The lower reflector 9 runs at least partially parallel to the main emission plane P1 and is configured to redirect the converted radiation R2, which propagates inside the wavelength conversion unit 5 in almost all directions, to the main conversion direction D1. For example, the converted radiation R2 directed to the lower part of the wavelength conversion unit 5, that is, to the substrate 3, is easily redirected to the upper part of the wavelength conversion unit 5.

The wall reflector 8 and/or the bottom reflector 9 may extend at an angle to the main transformation direction D1. The wall reflector 8 may extend at an angle that is not perpendicular to the main emission plane P1 such that the emission radiation R1 incident on the wall reflector 8 is directed towards the substrate 3 and preferably towards the bottom reflector 9, or the user interface surface 2. Bottom reflector 9 may run parallel to the main emission plane P1 so as to reflect the emission radiation R1 propagating towards the substrate 3, or it may extend at an angle to the main emission plane P1 so that the reflection of the emission radiation R1 propagating towards the substrate 3 can be directed at a specific, predetermined direction. The wall reflector 8 and/or the bottom reflector 9 may have a reflective surface, preferably a metal layer. The metal layer may be a layer of sputtered aluminum, in which case the wall reflector 8 and/or the bottom reflector 9 also prevent optical crosstalk between adjacent pixel structures.

Accordingly, the wavelength conversion unit 5 may be configured such that at least one surface 5a, 5b of the wavelength conversion unit extends at an angle α to the main plane P2 of the substrate 3, with the surface 5a facing away from the substrate 3 and the surface 5b, passes adjacent to the substrate 3. At least one of the surfaces 5a, 5b of the wavelength conversion unit passes at an angle α due to the fact that the wavelength conversion unit 5, the substrate 3 or both are wedge-shaped, i.e. narrow as they pass along the main emission plane P1 or the main plane P2 of the substrate. FIG. 7 shows an embodiment in which only the surface 5a of the wavelength conversion unit extends at an angle α to the main plane P2 of the substrate 3 due to the narrowing of the wavelength conversion unit 5 itself. Both surfaces 5a, 5b of the wavelength conversion unit may extend at an angle α to the main plane P2 of the substrate 3. Moreover, the surface 5a of the wavelength conversion unit may extend at an angle α1, and the surface 5b of the wavelength conversion unit may extend at an angle α2. Due to the higher refractive index of the matrix material of the wavelength conversion unit compared to the surrounding air, only the converted radiation R2 incident on the surface 5a, 5b of the wavelength conversion unit at an angle less than the critical angle for total internal reflection leaves the conversion unit 5 wavelength, while the other converted radiation R2 will be reflected from the surface 5a, 5b of the wavelength conversion unit and remain inside the wavelength conversion unit 5. By adopting the above-mentioned tapered wedge shape, the radiation output efficiency is improved since the radiation trapped inside the wavelength conversion unit 5 will ultimately hit the surface 5a, 5b of the wavelength conversion unit at a smaller angle upon reflection.

As shown in FIG. 12, the wavelength conversion unit 5 may include a waveguide structure 10 configured to guide emission radiation R1 as it propagates within the wavelength conversion unit 5. The waveguide structure may have any suitable shape, such as curved as in FIG. 12 or helical (not shown).

The pixel structure 1 may further comprise at least one optical functional element 11 located on the surface 5a of the wavelength conversion unit facing away from the substrate 3, as shown in FIG. 8 and 9. The optical function element 11 may be located on top of the wavelength conversion unit surface 5a, as shown in FIG. 9, or integrated with the surface 5a of the wavelength conversion unit, as shown in FIG. 8.

The optical functional element 11 shown in FIG. 9 may be at least one of a refractive lens and a diffractive lens used for focusing the converted radiation R2, for example.

Instead, the optical functional element 11 may be a surface structure, preferably one of a surface array, as shown in FIG. 8, of a surface roughness, a surface coating, or a micropillar. The grating increases the output efficiency of the converted radiation R2 by controlling the converted radiation R2.

As shown in FIG. 2b, multiple LED emitters 4 may be operatively coupled to a single wavelength conversion unit 5 and configured to both simultaneously and independently emit emission radiation R1 to the wavelength conversion unit 5. This provides redundancy that gives better output and also ensures that if one of the LED emitters 4 fails, the pixel structure 1 will still function as intended without any dark areas.

As shown in FIG. 10, the control arrangement 12 is designed to regulate the total output of the converted radiation R2, R21, R22, and the control contains pulse-width modulation and adjustment of the excitation current of the LED emitters 4.

In one embodiment, the converted radiation R2, R21, R22 propagates in the main conversion direction D2 to the user interface surface 2a without applying radiation filtering.

The pixel structure 1 may contain at least three LED emitters 4, with at least one first wavelength conversion unit 5 operatively connected to the first LED emitter 4, and at least one second wavelength conversion unit 5 operatively connected to the second LED emitter 4. As shown in FIG. 2b, the pixel structure 1 may include six LED emitters 4, the first pair of LED emitters 4 being operatively connected to the first wavelength conversion unit 5, and the second pair of LED emitters 4 being operatively connected to the second wavelength conversion unit 5. The first wavelength conversion unit 5 is preferably configured to convert the emission radiation R1 from the first pair of LED emitters 4 into the first converted radiation R2, and the second wavelength conversion unit 5 is preferably configured to convert the emission radiation R1 from the second pair of LED emitters 4 into the second converted radiation R2 .

As also shown in FIG. 2b, each LED emitter 4 of the third pair of LED emitters 4 may be operatively connected to one radiation diffusion unit 6 or one additional wavelength conversion unit 5 each. When the emission radiation R1 is within the ultraviolet spectral range, the third pair of LED emitters 4 are preferably operably connected to one additional wavelength conversion unit 5 each, wherein the additional wavelength conversion units 5 are configured to convert the emission radiation R1 within the ultraviolet spectral range from the third pair LED emitters 4 to the third converted radiation R3, for example, in the blue spectral range (not shown). Instead, when the emission radiation R1 is in the blue spectral range, the third pair of LED emitters 4 are preferably operatively connected to one radiation diffusion unit 6 each. Each LED emitter 4 may be operatively connected to one wavelength conversion unit 5, optionally the connection comprising an anode contact layer for each LED emitter, for example, a metal contact layer shown as the bottom layer in FIG. 3b, and the substrate 3 contains a cathode layer. The metal contact layer supplies current to the LED emitter and prevents unwanted emission radiation from R1 towards the bottom of the LED emitter and therefore onto the substrate 3.

In fig. 10 shows an electronic device 13 comprising an electronic display 2 having a user interface surface 2a and at least one pixel structure 1. The pixel structure 1 is configured to emit emission radiation R1 with one emission wavelength in multiple emission directions D2,...,Dn in within the main emission plane P1, as indicated in Fig. 2b, to convert at least a portion of the emission radiation R1 into converted radiation R2, R21, R22 with at least one converted wavelength and direct the converted radiation R2, R21, R22 in the main conversion direction D1, perpendicular to the main emission plane P1 and the surface 2a user interface. The main emission plane P1 extends substantially parallel to the user interface surface 2a. The pixel structure 1 is configured to convert emission radiation into at least one, preferably several, converted wavelengths, the different converted wavelengths being different from each other and from the emission wavelength.

As shown in FIG. 11-18, the electronic device 13 may include a plurality of identical pixel structures 1, wherein the pixel structures 1 are distributed in the main emission plane P1 in the form of a two-dimensional pattern. The two-dimensional pattern contains rows of pixel structures 1 and columns of pixel structures 1, with the rows running parallel and intersecting the columns at perpendicular angles. The number of pixel structures 1 in a single row is independent of the number of pixel structures 1 in an adjacent row, as shown in FIG. 17, which alternately shows one and two pixel structures 1 in each row, and FIG. 18, which alternately shows two and three pixel structures 1 in each row. Accordingly, the number of pixel structures 1 in a particular column is independent of the number of pixel structures 1 in an adjacent column, as shown in FIG. 17, which alternately shows two and three pixel structures 1 in each column, and FIG. 18, which shows alternately one and two pixel structures 1 in each column. This distribution of pixel structures 1 allows the number of pixel structures 1 in the area containing the two-dimensional pattern to be maximized.

As shown in FIG. 13, a plurality of pixel structures 1 may be distributed with a first step in a two-dimensional pattern such that at least a first emission direction D2 of an emission light R1 in an individual pixel structure 1 matches the corresponding first emission direction D2 of an adjacent pixel structure 1. As also shown in fig. 13, the second, third and fourth emission directions D3, D4 and D5 may also coincide with the corresponding second, third and fourth emission directions D3, D4 and D5 of the adjacent pixel structure 1. In other words, the pixel structures 1 may be arranged in a two-dimensional rectangular grid pattern template, and the number of pixel structures is 1 in a row, the number of pixel structures is 1 in a column, the distances between rows and the distances between columns are constant. The pitch is the distance between the center points of adjacent pixel structures 1. This type of matching arrangement is suitable when the absorption path length A is small compared to the pitch.

As shown in FIG. 11, 12 and 14 to 18, the plurality of pixel structures 1 may instead be distributed with a second pitch in a two-dimensional pattern such that at least the first emission direction D2 of the emitted radiation R1 of the individual pixel structure 1 does not coincide with the corresponding first emission direction D2 adjacent pixel structure 1. Preferably, the non-coinciding emission directions run in parallel, so that all pixel structures 1 do not coincide by the same amount and in the same direction, for example, due to rotation in the main emission plane P1 with respect to the column and row pattern.

Regardless of possible rotation, the pixel structures 1 can be arranged such that their center points coincide in both directions of the two-dimensional pattern, as shown in FIG. 11, 12 and 15. The pixel structures 1 can also be arranged such that their center points coincide in one direction of the two-dimensional pattern, but are offset in the other direction, as shown in FIG. 14 and 16. As shown in Fig. 17 and 18, the pixel structures 1 may also be arranged such that their center points do not coincide in both directions of the two-dimensional pattern. A rotated, non-matching arrangement is suitable when the absorption path length A is large compared to the pitch.

The non-coincidence allows the absorption path length A of each such pixel structure 1 having one or more non-coinciding emission directions to be traversed. Because the emission directions do not coincide or extend along the same rows or columns, but instead within the free regions between such rows and columns, the length of each absorption path A is less limited by the length of adjacent absorption paths A. Consequently, the size of the absorption path A may exceed, for example, the external size of the wavelength conversion unit 5 in the main emission plane P1, i.e. the length of the absorption path A may be greater than the length or rather the width of the wavelength conversion unit 5 that passes inside. For example, FIG. 11 shows an embodiment in which the absorption path A is folded in half at opposite ends of the wavelength conversion unit 5, and FIG. 12 shows an embodiment in which the absorption path A is bent.

Fig. 14-18 show embodiments in which the pitch between adjacent pixel structures 1 has been reduced. In FIG. 15, the pitch is similar to the absorption path length A, so that it cannot correspond to two adjacent absorption paths on a straight line between pixels. Therefore, the emission direction of each pixel structure 1 is rotated with respect to the pattern of the pixel structures 1 such that the absorption path A of one pixel structure 1 is adjacent to the absorption path A of the adjacent pixel structure 1 without overlap. Thus, the pitch between pixel structures 1 is maximally used for absorption path A. The absorption path A must be long enough to provide high color conversion efficiency and high absorption of emission radiation R1, in particular in the blue spectral range.

Fig. 14 shows an embodiment in which the first emission direction D2 and the second emission direction D3 of the individual pixel structure 1 do not coincide to show a lateral displacement with the corresponding first emission direction D2 and the second emission direction D3 of the adjacent pixel structure, while the third and fourth emission direction the directions D4, D5 are the same because the required absorption path length is shorter for the emission from D4 and D5.

Fig. 15 and 16 show embodiments in which the first emission direction D2, the second emission direction D3, the third emission direction D4 and the fourth emission direction D5 of the individual pixel structure 1 do not coincide with the corresponding emission directions D2, D3, D4, D5 of the adjacent pixel structure, so that the two-dimensional pattern contains one or more interconnected parallelograms.

Fig. 17 and 18 show embodiments in which the first emission direction D2, the second emission direction D3, the third emission direction D4 and the fourth emission direction D5 of the individual pixel structure 1 are not aligned to have a lateral offset with the corresponding emission directions D2, D3, D4, D5 adjacent pixel structure and such that the two-dimensional pattern contains a honeycomb pattern of distributed pixel structures 1.

As mentioned above, the pixel structures 1 can be located in the first step, i.e. separated by him. In this case, the pixel structures 1 coincide in at least one of the column direction and the row direction, so that the absorption path(s) A of the wavelength conversion unit(s) 5 of the individual pixel structure 1 coincide with the corresponding absorption path(s) A neighboring pixel structure.

As mentioned above, the pixel structures 1 can be arranged in a two-dimensional array. Each pixel structure 1 may occupy an area of identical size and/or have the same absorption path length A as the other pixel structures 1. The absorption length may be 10-500 μm, preferably <20 μm. The pitch of the pixel structures 1 in the two-dimensional array may be 20-150 µm, preferably 30-80 µm, in display applications configured such that the distance between the user's eye and the user interface surface 2a is <1 m, i.e. for close-view displays, such as on smartphones. Accordingly, the second pitch may be ≥70 μm, preferably ≥100 μm, in display applications configured such that the corresponding distance between the user's eye and the user interface surface 2a is ≥0.5 m, i.e. for long-distance displays such as those found on televisions.

A plurality of pixel structures 1 distributed with a second pitch may be rotated by an angle β in the main emission plane P1, as shown in FIG. 11, 12, 15, 16 and 18, so that the absorption paths A of the wavelength conversion units 5 of the individual pixel structure 1 are not the same as the corresponding absorption paths A of the adjacent pixel structure.

In addition, the pixel structures 1 in a particular row may be offset in the columnar direction relative to the pixel structures 1 in an adjacent row, as shown in FIG. 14, 16 and 17. Accordingly, the pixel structures 1 in a particular column may be offset in the row direction relative to the pixel structures 1 in an adjacent column, as shown in FIG. 18.

Various aspects and implementations have been described herein in connection with various embodiments. However, other variations of the disclosed embodiments may be understood and implemented by those skilled in the art through practice of the claimed subject matter from a study of the drawings, disclosure, and appended claims. In the claims, the word “comprising” does not exclude other elements or steps, and the singular indefinite article does not exclude the plural. One processor or other unit can perform the functions of several elements specified in the claims. The mere fact that certain measures are specified in mutually different dependent claims does not mean that a combination of these measurable quantities cannot be used to advantage. The computer program may be stored/distributed on a suitable medium, such as an optical storage medium or solid state media provided with or as part of other equipment, but may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunications systems.

The designations used in the claims should not be construed as limiting the scope. Unless otherwise noted, the drawings are intended to be read (e.g., shading, arrangement of parts, proportion, extent, etc.) in conjunction with the description and should be considered part of the entire written description of this disclosure. The terms “horizontal”, “vertical”, “left”, “right”, “up” and “down” used in the description, as well as adjectives and adverbial derivatives from them (for example, “horizontal”, “right”, “up” etc.), simply indicate the orientation of the structure being illustrated when a particular figure in the drawing is facing the reader. Likewise, the terms "in" and "out" usually refer to the orientation of a surface relative to its axis of extension or axis of rotation, as appropriate.

Claims (46)

1. A pixel structure (1) for an electronic display (2), wherein said pixel structure (1) comprises - backing (3), - at least one LED emitter (4) located on the substrate (3), said LED emitter (4) is configured to emit emission radiation (R1), said emission radiation (R1) is within the emission wavelength range and is emitted in one or more emission directions D2, ..., Dn) within the main emission plane (P1), - at least one wavelength conversion unit (5), located on the substrate (3) next to the LED emitter (4), wherein the wavelength conversion unit (5) is configured to convert emission radiation (R1) into converted radiation (R2) , said converted radiation (R2) is within the converted wavelength range and propagates from the wavelength conversion block (5) in the main conversion direction (D1), perpendicular to the main emission plane (P1), said converted wavelength range is different from said emission wavelength range. 2. The pixel structure (1) according to claim 1, wherein said emission wavelength range is one of the blue spectral range or the ultraviolet spectral range, and Moreover, when the pixel structure (1) contains at least two LED emitters (4), said LED emitters (4) are configured to emit radiation having the same wavelength. 3. Pixel structure (1) according to claim 1 or 2, containing at least two wavelength conversion blocks (5), each wavelength conversion block (5) configured to convert emission radiation (R1) in the emission wavelength range into converted radiation (R2) within one of many different converted wavelength ranges. 4. Pixel structure (1) according to claim 3, in which at least one first wavelength conversion block (5) is configured to convert the emission radiation (R1) into the first converted radiation (R21) located within the first converted length range waves, and at least one second wavelength conversion unit (5) is configured to convert the emission radiation (R1) into a second converted radiation (R22) located within the second converted wavelength range, wherein the second converted wavelength range is at least partially different from the first converted wavelength range. 5. The pixel structure (1) according to claim 4, wherein the first converted wavelength range is within the red spectral range, and the second converted wavelength range is within the green spectral range. 6. The pixel structure (1) according to any of the previous paragraphs, in which the LED emitter (4) is configured to emit emissive radiation (R1) only in the main emissive plane (P1), or wherein the emission radiation (R1) or at least part of the emission radiation (R1), which is emitted in the main emission plane (P1) by the said LED emitter (4), is converted into converted radiation (R2) in the length conversion block (5) waves. 7. Pixel structure (1) according to any one of claims. 1-5, in which, when the pixel structure (1) contains at least two LED emitters (4), at least one of the LED emitters (4) is configured to emit emissive radiation (R1) in the main conversion direction (D1) . 8. Pixel structure (1) according to any of the previous paragraphs, additionally containing at least one radiation dispersion unit (6), located on the substrate (3) next to the LED emitter (4), and the dispersion unit (6) is configured to redirection of emission radiation (R1), propagating in the main emission plane (P1), in the main direction (D1) of transformation. 9. The pixel structure (1) according to any one of the previous paragraphs, wherein the wavelength conversion unit (5) contains a wavelength conversion material, the wavelength conversion material preferably comprising a matrix material and wavelength conversion particles distributed in the matrix material. 10. The pixel structure (1) according to claim 9, wherein the wavelength conversion particles are quantum dots or phosphorus material. 11. The pixel structure (1) according to any of the previous paragraphs, in which the wavelength conversion unit (5) contains at least one barrier (7) extending along the periphery of the wavelength conversion unit (5) in the main conversion direction (D1), said barrier (7) is configured to expand the absorption path (A) of the wavelength conversion block (5), and the absorption path (A) passes in the main emission plane (P1), and the emission radiation (R1) propagates along the absorption path (A) And said conversion of emission radiation (R1) into converted radiation (R2) occurs simultaneously with said propagation. 12. The pixel structure (1) according to claim 11, further comprising at least one wall reflector (8) located on the surface of the barrier (7) extending at least partially in the main transformation direction (D1), said wall reflector (8) is configured to redirect emission radiation (R1) propagating along the absorption path (A), so that the absorption path (A) of the wavelength conversion unit (5) passes within said main emission plane (P1). 13. Pixel structure (1) according to any of the previous paragraphs, additionally containing at least one lower reflector (9) located between the wavelength conversion unit (5) and the substrate (3), said lower reflector (9) runs at least partially parallel to the main emission plane (P1) and is configured to redirect the converted radiation (R2) propagating in the wavelength conversion block (4) to the main conversion direction (D1). 14. The pixel structure (1) according to claim 13, wherein the wavelength conversion unit (5) comprises a waveguide structure (10) configured to guide emission radiation (R1) as it propagates within the wavelength conversion unit (5). 15. The pixel structure (1) according to any of the previous paragraphs, in which the wavelength conversion unit (5) is configured such that at least one surface (5a, 5b) of the wavelength conversion unit extends at an angle (a) to the main plane ( P2) of the substrate (3), wherein said surface (5a) faces away from the substrate (3) and said surface (5b) extends adjacent to the substrate (3). 16. The pixel structure (1) according to claim 15, wherein one of the wavelength conversion unit (5) and the substrate (3) tapers as it passes along the main emission plane (P1) or the main plane (P2) of the substrate. 17. The pixel structure (1) according to any of the previous paragraphs, further comprising at least one optical functional element (11) located on the surface (5a) of the wavelength conversion unit facing away from the substrate (3), wherein the optical functional element (11) is one of the wavelength conversion unit located on top of the surface (5a) and integrated with the wavelength conversion unit surface (5a). 18. The pixel structure (1) according to claim 17, wherein the optical functional element (11) is at least one of a refractive lens and a diffractive lens. 19. Pixel structure (1) according to claim 17, wherein the optical functional element (11) is a surface structure, preferably one of surface gratings, surface roughness, surface coating or micropillars. 20. Pixel structure (1) according to any of the previous paragraphs, in which several of the LED emitters (4) are operatively connected to one wavelength conversion unit (5), and the LED emitters (4) are configured to emit emission radiation (R1) as simultaneously and independently into the wavelength conversion block (5). 21. The pixel structure (1) according to any of the previous paragraphs, further comprising a control arrangement (12) for regulating the total output of the converted radiation (R2, R21, R22), said control comprising pulse-width modulation and control of the excitation current of said LED(s). emitter(s) (4). 22. An electronic display device (13), comprising an electronic display (2) having a user interface surface (2a) and at least one pixel structure (1) according to any one of claims. 1-21, wherein the pixel structure (1) is configured to allow emission of emission radiation (R1) with one emission wavelength in several emission directions (D2, ..., Dn) within the main emission plane (P1), while the main emission the plane (P1) runs parallel to said user interface surface (2a), convert at least a portion of the emission radiation (R1) into converted radiation (R2, R21, R22) of at least one converted wavelength, wherein said converted wavelength is different from the emission wavelength, and direct the converted radiation (R2, R21, R22) in the main conversion direction (D1) perpendicular to the main emission plane (P1) and the user interface surface (2a). 23. The electronic display device (13) according to claim 22, comprising a plurality of identical pixel structures (1), said pixel structures (1) being distributed in a main emission plane (P1) in the form of a two-dimensional pattern, said two-dimensional pattern comprises rows of pixel structures (1) and columns of pixel structures (1), said rows running parallel and intersecting said columns at perpendicular angles, the number of pixel structures (1) in a single row is independent of the number of pixel structures (1) in the adjacent row, and the number of pixel structures (1) in a separate column does not depend on the number of pixel structures (1) in the adjacent column, said distribution of pixel structures (1) allows to maximize the number of pixel structures (1) in the area containing said two-dimensional pattern. 24. The electronic display device (13) according to claim 23, wherein said plurality of pixel structures (1) are distributed with a first step in said two-dimensional pattern such that at least the first emission direction (D2) of the emission radiation (R1) of an individual pixel structure (1) coincides with the corresponding first emission direction (D2) of the adjacent pixel structure (1). 25. The electronic display device (13) according to claim 23, wherein said plurality of pixel structures (1) are distributed with a second pitch in said two-dimensional pattern such that at least the first emission direction (D2) of the emission radiation (R1) of an individual pixel structure (1) does not coincide with the corresponding first emission direction (D2) of the adjacent pixel structure (1), wherein said mismatch represents a lateral displacement and/or angular displacement of the orientation of each pixel structure (1). 26. Electronic display device (13) according to claims. 24 and 25, in which, with a fixed length of said absorption path (A), the length is 10-500 µm, preferably <20 µm, and wherein said second pitch is 20-150 µm, preferably 30-80 µm, in display applications configured such that the distance between the user's eye and the user interface surface (2a) is < 1 m, and said second pitch is ≥70 μm, preferably ≥100 μm, in display applications configured such that the corresponding distance between the user's eye and said user interface surface (2a) is ≥0.5 m.