Optical element, method for manufacturing same, and light-emitting device

Abstract

The present application relates to an optical element (10) having a first large face through which light enters the optical element (10) and a second large face through which light exits the optical element (10), the optical element (10) comprising: a first region (E1) consisting of a transparent material having a first refractive index (N1), and a second region (E2) consisting of a transparent material having a second refractive index (N2), the second region (E2) consists of at least 50% of an opaque material having a second refractive index (N2) and at most 50% of a reflective or white scattering material, the first refractive index (N1) being greater than the second refractive index (N2). The first region (E1) is arranged such that light irradiated onto the first large surface of the optical element (10) enters the optical element (10) at least partially through the light entry surface of the first region (E1) or onto the reflective or white-scattering second region (E2), and a) propagates or is completely reflected in the first region (E1) and then is re-coupled out at the light exit surface, or b) refracted from the first region (E1) to the adjacent second region (E2) and absorbed in this region, or reflected or scattered by the reflective or white scattering material of the second region (E2). As a result, with respect to light irradiated onto the optical element (10), light exiting from the second large surface of the optical element (10) is restricted in the propagation direction thereof, and at least a portion of the light irradiated onto the second region (E2) is reflected or scattered.

Description

Technical Field

[0001] In recent years, great progress has been made in extending the viewing angle of LCDs. However, in some cases, the large viewing area of ​​a display can often be a disadvantage. More and more information (for example, banking data or other personal and sensitive data) is available on mobile devices such as laptops and tablets. Therefore, people need to control who can see this sensitive data. They may choose a wide viewing angle (for example, to view travel photos or advertisements) to share the information on the screen with others. On the other hand, they need a narrow viewing angle when they want to process the information on the display privately.

[0002] The same problem exists in vehicle architectures, where the driver cannot be distracted by screen content (e.g., entertainment programs) when the engine is on, while passengers want to watch the content while driving. Therefore, a display screen that can switch between two display modes is required. Background Art

[0003] Additional films based on micro shutters have been used in mobile display devices to achieve visual data protection. However, the additional film is not controllable or switchable and can only be applied and removed by hand. When not needed, the additional film must be removed separately for display. In addition, another major disadvantage of using such shutter films is that there will be a certain amount of light loss.

[0004] US6765550B2 describes such a privacy barrier based on micro shutters, which has the disadvantages of requiring mechanical removal or installation of filters and loss of light in protection mode.

[0005] US5993940A describes a method for using a film, wherein small prism strips are evenly arranged on the surface of the film to achieve an anti-peeping mode, but the development and production costs are quite high.

[0006] In WO 2012 / 033583 A1, the switching between the free mode and the confined mode is controlled by liquid crystals between so-called “color” layers, which results in light losses and is also quite costly.

[0007] US2012 / 0235891A1 describes a rather complex screen backlight. Figure 115 not only use multiple light guides, but also other complex optical elements, such as micro lens elements 40 and prism structures 50, which can convert the light of the rear lighting into the light of the front lighting. This is expensive and complicated, and will also cause light loss. According to the variation described in FIG. 17 of US2012 / 0235891A1, both light sources 4R and 18 produce light with a narrow light angle, and the light of the rear light source 18 must first be complexly converted into light with a large light angle. As mentioned above, this complex conversion will greatly reduce the brightness.

[0008] JP2007-155783A utilizes a special optical surface 19 that is complex to calculate and manufacture, so that the light is deflected to different narrow or wide areas according to the angle of incidence of the light. The structure is similar to a Fresnel lens. In addition, there are some interfering edges that deflect the light in undesirable directions. Therefore, it is uncertain whether it can achieve meaningful light distribution.

[0009] US2013 / 0308185A1 describes a special stepped light guide that emits light from different directions onto a large surface, depending on which narrow side of the light guide is illuminated, which in combination with a transmissive image display device (e.g., a liquid crystal display) can produce a screen that can be switched between a free viewing mode and a restricted viewing mode. Disadvantages include: the restricted viewing effect can only be used for the left / right side or the top / bottom side, but not for the left / right / top / bottom side at the same time, which is necessary in some payment processes. In addition, even in the restricted viewing mode, residual light can still be seen from the obstructed viewing angle.

[0010] WO2015 / 121398A1 describes a screen with two operating modes, in which scattering particles present in the volume of the corresponding light guide are essentially used to achieve the switching of the operating modes. However, scattering particles made of polymers generally have the disadvantage of emitting light from two large surfaces, so that about half of the useful light is emitted in the wrong direction, that is, towards the backlight, and these lights cannot be recycled to a sufficient extent due to structural reasons. In addition, in some cases, especially at high concentrations, scattering particles made of polymers in the light guide volume can cause a scattering effect, thereby reducing the anti-peeping effect in the protected mode.

[0011] WO2022 / 078942A1 and DE102020008062A1 each disclose an optical element that can structure the penetrating light in its propagation direction. The disadvantage is that the light absorbed by the opaque area will completely lose the light balance.

[0012] DE102021120469B3 describes an optical element for selectively limiting the propagation direction of light based on electrophoretic particles. The disadvantage is that the switching time of the working mode takes several seconds.

[0013] WO2021 / 032735A1 and DE102020007974B3 both disclose an optical element with variable transmittance. They are also limited by relatively long switching times based on electrophoretic particle motion or electrowetting. In addition, light recycling is not possible on opal particles.

[0014] The above methods and devices generally have the following disadvantages: significantly reducing the brightness of the basic screen, and / or requiring complex and expensive optical elements to achieve mode switching, and / or only providing limited privacy protection, and / or reducing the resolution in the free viewing mode, and / or only having a narrow viewing area, the brightness drops sharply within the angular spectrum, and the brightness of the image seen by the viewer is very uneven.

[0015] Furthermore, great efforts are made to avoid reflections (e.g., on windshields) by limiting the emission angle. The disadvantages of using commercially available shutter filters are, on the one hand, light losses and, on the other hand, the triangular distribution of light with respect to angle, which often results in an uneven image for the viewer. Summary of the invention

[0016] The purpose of the present application is to develop a planar extended optical element which is able to affect the incident light explicitly in the direction of propagation of the incident light. The implementation cost of the optical element is low and it can be universally compatible with different types of screens. In this way, the resolution of the screen is not substantially reduced, or the reduction is substantially negligible. In addition, the optical element is in principle able to achieve a top-hat light distribution. That is, exemplarily, within an angular region of at least 7 degrees around the peak emission direction, the brightness reduction does not exceed 35%, or the brightness distribution with respect to the angle is as close to a rectangle as possible. In addition, a special requirement for the optical element is to increase the effective light transmittance compared to the prior art.

[0017] The present application achieves the above-mentioned purpose through a planarly extended optical element. The optical element has a first large surface from which light enters the optical element and a second large surface from which light leaves the optical element. On the one hand, the optical element includes a plurality of first regions E1, which are at least composed of a transparent material having a first refractive index N1; on the other hand, the optical element includes a plurality of second regions E2, which are composed of at least 50% of an opaque material having a second refractive index N2 and at most 50% (but at least 5% or 10%) of a reflective or white scattering material. A plurality of first regions E1 and a plurality of second regions E2 are alternately arranged on the surface of the optical element in a one-dimensional sequence or a two-dimensional sequence. Preferably, the sequence is periodic, but not necessarily periodic in dimension. In addition, within the entire wavelength range visible to the human eye, the first refractive index N1 is greater than the second refractive index N2. In a plurality of second regions E2, the opaque material is mainly arranged in the direction of the second large surface of the optical element. Viewed from a cross-sectional direction perpendicular to the second large surface of the optical element, the plurality of first regions E1 and the plurality of second regions E2 are trapezoidal, and at least partially parabolic and / or stepped.

[0018] In this way, it is possible to achieve that light incident on the first large surface (light incident side) of the optical element at least partially enters the optical element through the light incident surfaces of multiple first regions E1, or illuminates the reflective or white scattering second region E2, and according to the incident angle of the light, the polarization of the light, and / or the ratio of the first refractive index N1 and the second refractive index N2, a) propagates unimpeded in the first region E1 or is completely reflected, and then is recoupled out at the light exit surface in the corresponding first region E1, or b) is completely or partially refracted from the first region E1 to the adjacent second region E2, and is absorbed due to the opaque material of the second region E2, or is reflected or scattered due to the reflective or white scattering material of the second region E2.

[0019] Therefore, relative to the light incident on the optical element on the first large surface, the light emitted from the second large surface of the optical element is limited in its propagation direction. In addition, at least a portion of the light incident on the optical element in the second area E2 on the first large surface of the optical element is reflected or scattered, and generally at least 25% of the incident light is reflected or (backward) scattered.

[0020] Therefore, according to the present application, when observed along the cross-sectional direction perpendicular to the second largest face of the optical element, the first area E1 and the second area E2 are trapezoidal, at least partially parabolic and / or stepped. The propagation direction of light emitted from the optical element can be targeted by the first area E1 and the second area E2 having these shapes. Depending on the specific design, the light forms a strong focus or a weak focus on the plane. In addition, the peak offset is achieved by the inclination of the boundary surface between the first area E1 and the second area E2 of the parallelogram cross section. The advantage of the trapezoidal shape is that the angular distribution can be better focused, thereby further improving lateral privacy protection. Particularly preferred is the first area E1 of a trapezoidal cross section, whose width on the second largest face (light exit side) is greater than the width on the first largest face (light incident side), and it is particularly preferred to be substantially an isosceles trapezoid.

[0021] Due to technical limitations in actual production, the above-mentioned trapezoidal, at least partially parabolic and / or stepped shapes can usually only be approximately realized, and therefore also include shapes that are relatively deviated due to technical reasons. A design that is at least partially parabolic may be desired, but it may also be caused by technical limitations in manufacturing. For example, when the trapezoidal shape cannot be accurately manufactured, a parabolic shape may be partially presented. However, this does not affect the effect of the present invention. In addition, illustratively, when observed in a cross-sectional direction perpendicular to the second large face, the trapezoidal, parabolic and / or stepped shapes may appear alternately.

[0022] The trapezoidal shape can also be designed to be asymmetrical to achieve an offset in the brightness distribution relative to the normal.

[0023] As an alternative to a trapezoidal geometry with straight edges, the side surfaces of the boundary surface between the transparent first region E1 and the absorptive second region E2 can be designed with rounded corners. This has two advantages: on the one hand, it simplifies the molding process during the manufacture of the optical element; on the other hand, the additional focusing effect can increase the effective transmittance and limit the propagation direction of the light.

[0024] Opaque materials do not necessarily need to have 100% opacity, but should strive for higher opacity as much as possible. Based on the desired brightness distribution with respect to the transmission curve, the opacity required for a specific application scenario can be determined through ray tracing simulation.

[0025] Due to the difference between the first refractive index N1 and the second refractive index N2, before the light entering the second region E2 is absorbed, it will be refracted and deviate from the normal more significantly, which usually helps to enhance the absorption effect.

[0026] In addition, due to the difference in refractive index between the first area E1 and the second area E2 (the difference between the first refractive index N1 and the second refractive index N2), when light passes through the optical element, a different angular spectrum is generated than when there is no such refractive index difference, because part of the light is reflected back to the first area E1 by total reflection and continues to be used for light balancing. Therefore, the optical element is basically able to achieve a top-hat light distribution. This means that, as mentioned at the beginning, the brightness distribution varies with angle (for example, the angle in the horizontal direction from a standing or sitting observer) and is as close to a rectangular shape as possible. Depending on the specific design, the brightness within an angular range of at least 7 degrees around the peak emission direction can drop by no more than 35%, or even no more than 25%. In addition, due to the presence of reflective or white scattering materials, good efficiency can be achieved.

[0027] Furthermore, the optical element may further include a substrate S and / or a cover layer D, between or on which the first region E1 and the second region E2 are arranged.

[0028] Of the light incident on the first large surface of the optical element, the reflected or scattered portion (especially at the second area E2) should generally account for at least 20% to 25% or more, and can be recycled in the light source below. Through the focusing effect of the above structure of the optical element, the efficiency of recycling light can also be increased by up to 3 times.

[0029] Therefore, the material with reflection or white scattering effect in the second area E2 on the first large surface of the optical element reflects at least part of the incident light to its starting point. In this case, at least part of the reflection can be specular reflection or diffuse reflection.

[0030] Exemplarily, in the second area E2, the ratio of opaque material to reflective or white scattering material may be: a) 50 / 50, b) 60 / 40, c) 70 / 30, e) 80 / 20, f) 75 / 25 (preferred), or g) 90 / 10. Other solutions are also feasible and included in the scope of the present invention.

[0031] To simplify the manufacturing process, the above-mentioned reflective or white scattering material can be composed of a transparent material with a second refractive index N2, or a transparent material suitable for a filling process and having a refractive index less than or greater than the second refractive index N2, and the material is doped with reflective and / or white scattering particles, so as to achieve a reflective or white scattering effect as a whole. For example, the material in the second area E2 can be achieved by dispersing nano or micro particles in a transparent paint to form a mixture.

[0032] For example, particles of TiO2 or SiO2, powder / paint mixtures or similar filler materials can be used, which can also be deposited by silver, aluminum or chromium, or coated with a solvent, which then evaporates to form a reflective metal layer. In addition, scattering or reflection effects can also be generated by targeted evaporation or sputtering of the boundary area between the first area E1 and the second area E2, for example, using aluminum, chromium or other metal or dielectric layers. In addition, similar to the use of paint, the corresponding material can also be introduced into the second area E2 in the form of a solution, but the solvent is evaporated, for example, by heating, etc., and the required material remains in the structure accordingly.

[0033] Exemplarily, the opaque material may be composed of a transparent material having a second refractive index N2, wherein the material is doped with absorptive particles, thereby producing an overall opaque effect.

[0034] It is therefore conceivable that the opaque material consists of a paint or a polymer into which graphite particles with a particle size of less than 500 nanometers, black carbon nanoparticles with a particle size of less than 200 nanometers, Fe(II,III)O particles, MnFe2O4 particles, a dye or a dye mixture are mixed as absorbent particles.

[0035] The mass fraction of absorbent particles should be at most 75%. For graphite particles, the mass fraction should only be between 5% and 30% (inclusive). For Fe(II,III)O particles, the preferred mass fraction is between 10% and 75% (inclusive).

[0036] The refractive index difference between the first refractive index N1 and the second refractive index N2 should be less than 0.15, but should not exceed 0.2 at most.

[0037] Furthermore, advantageously, when observing the parallel projection perpendicular to the optical element 10, the first area E1 and the second area E2 are arranged alternately in strips on the surface of the optical element. The "periodically alternating" first area E1 and second area E2 does not mean that they must always have the same width and / or height, but means that the first area E1 and the second area E2 always appear alternately. However, their sizes can vary. Therefore, the light propagation direction perpendicular to the strip-shaped area will be limited, while the light propagation direction parallel to the strip-shaped area will not be affected.

[0038] In contrast, in other embodiments, the first area E1 is distributed on the surface of the optical element in a dot, circular, elliptical, rectangular, hexagonal or other two-dimensional shape when observed in a parallel projection perpendicular to the optical element, while the shape of the second area E2 is complementary thereto. Therefore, the light propagation direction is restricted in at least two planes perpendicular to the surface of the optical element. In practice, the effect of such an optical element is usually to focus the light propagation direction of the transmitted light at every angle close to or parallel to the vertical center line of the optical element. In this case, "close" means that the angle (depending on the specific design) from the vertical center line or parallel line is less than 25° or 30°.

[0039] Other shapes of the first region E1 and the second region E2 are also possible. For maintaining the function of the present invention, it is important that the first region E1 and the second region E2 directly adjoin each other optically, so that a sudden change in the light refractive index is achieved without air gaps as far as possible.

[0040] In addition, a lens structure L, preferably a convex lens structure, is disposed on the light exiting side of at least a portion of the first area E1 (preferably, on all the first areas E1), so as to further focus the light passing through the optical element.

[0041] For special application scenarios, it is advantageous to form at least one first region E1 on the optical element, and when observed in a parallel projection perpendicular to the optical element, the minimum size of the at least one first region E1 is at least twenty times the minimum size of all the second regions E2 when observed in a parallel projection perpendicular to the optical element. Therefore, within the at least one first region E1 (except for its edge, loss and parallel offset), relative to the light incident on the light incident side of the optical element, the light emitted from the light exit side of the optical element has no propagation direction restriction.

[0042] In addition, in addition to the first region E1 and the second region E2, other regions E3, E4, ... can also be formed. Such other regions have parameters different from those of the first region E1 and the second region E2 in terms of shape and / or refractive index, so that the light passing through these other regions E3, E4, ... and emerging from the optical element is subject to different restrictions in the propagation direction than in the first region E1.

[0043] The present invention also includes a method for manufacturing the above optical element, wherein the optical element includes a plurality of first regions E1 and a plurality of second regions E2, wherein the plurality of first regions E1 and the plurality of second regions E2 are alternately arranged on a surface of the optical element 10 in a one-dimensional sequence or a two-dimensional sequence. The method includes the following steps:

[0044] A plurality of first regions E1 are formed on the substrate S using a transparent material having a first refractive index N1, for example, by a nanoimprinting process (for example, roll-to-roll UV nanoimprinting), so that a gap is formed between any two of the plurality of first regions E1;

[0045] Partially (but not completely) filling the gap with an opaque material having a second refractive index N2 so that the gap is filled to at least 50% of its height, thereby partially forming a plurality of second regions E2; this may be achieved by one or more filling steps;

[0046] The gap is further filled with diffuse or specular reflective material to completely form the second area E2, wherein at most 50% of the height of the second area E2 is constituted by the diffuse or specular reflective material; the material used here does not need to be 100% opaque, and usually at least 25% opacity is sufficient.

[0047] Optionally, as a final step, the method further comprises: sealing the first regions E1 and the second regions E2 on a side facing away from the substrate by coating a paint and / or a covering layer.

[0048] In principle, it is also possible to use any material instead of the diffuse or specular reflective material, but it is necessary to coat the boundary surface between the first area E1 and the second area E2 with one or more diffuse or specular reflective materials.

[0049] Alternatively, a thin film (as a cover layer) can be laminated using an optically clear adhesive (OCA) for sealing to protect the structure from mechanical stress and environmental conditions.

[0050] In addition, it is possible to laminate a so-called dual brightness enhancement film (DBEF) TM , Dual Brightness Enhancement Film), for example, by 3M TM This film not only acts as a protective layer, but also improves the effective transmittance by polarization recycling. When the transmission polarization direction is perpendicular to the main propagation direction of the first region E1, the light focusing is further improved because the optical function of the structure is sensitive to polarization.

[0051] The incident angle of light or (same meaning) rays incident on the first region E1 is the geometrical incident direction, in particular the direction vector of the light. The direction vector describes the horizontal and vertical incident angles of the light relative to the light incident surface (also called "lower surface") of the first region E1, and is very important for the further propagation of the light in each such first region E1 or at the boundary surface with the second region E2, compared with the polarization state of the light.

[0052] In order to clarify the physical concepts, it is emphasized here again that the term "refractive index" can refer to the first refractive index N1 or the second refractive index N2 for a specific wavelength (such as 580 nanometers), or it can refer to the entire dispersion curve within the visible wavelength range of the human eye. In the case of the dispersion curve, the refractive index difference refers to the difference between the two corresponding refractive indices at any selected wavelength λ within the visible wavelength range.

[0053] If present, the substrate and / or the cover layer may optionally consist of the same material as the first area E1 .

[0054] Furthermore, it is advantageous to arrange a polarizer (optionally, a reflective polarizer) below and / or above the optical element to optimize the effect. By controlling the polarization state through the polarizer, the utilization efficiency of the refractive index conversion can be improved. In addition, by utilizing the p-polarization state of the incident or outgoing light, the Fresnel reflection can be effectively reduced, that is, the restriction of the light propagation direction can be optimized.

[0055] Generally speaking, for all optical elements, the roughness Ra of the boundary surface between the first region E1 having the first refractive index N1 and the second region E2 having the second refractive index N2 should be less than or equal to 400 nanometers, preferably less than 100 nanometers, and particularly preferably less than 40 nanometers.

[0056] The present invention is particularly important when the above optical element is applied in combination with a display unit (e.g., an LCD panel, an OLED, a microLED, or a display unit based on other display technologies with a pixel structure) or with an illumination device for a transmissive display unit (e.g., an LCD panel). In the latter case, the optical element will be directly integrated into the illumination device for a transmissive display unit (e.g., an LCD panel). The illumination device can continue to function as a directional backlight and can be exemplarily applied in the embodiments described in WO2015 / 121398A1 or WO2019 / 002496A1 of the applicant.

[0057] Optionally, in the case where the optical element according to the present invention is arranged in front of the display unit along the viewing direction, an optical device is also configured on the display unit, which mainly focuses the light emitted by each pixel of the display device onto the surface opposite to the first area E1. Exemplarily, this can be achieved by a microlens array or a cylindrical lens, which has a period that is roughly the same as the pixel width (or pixel height). Ideally, the period of the first area E1 should be consistent with the period of the pixel width or height. In this way, a particularly high transmission efficiency of the optical element can be achieved.

[0058] The various embodiments of the present invention described above can also be implemented directly on a self-luminous display unit. Among them, it is particularly suitable for an OLED panel, which will be described in more detail below. Of course, other types of self-luminous displays are also feasible.

[0059] Exemplarily, it can be realized as follows: the first region E1 made of the material with the first refractive index N1 is directly disposed on the light emitting region of the OLED pixel, and the second region E2 complementary to the first region E1 is disposed on the non-light emitting region of the OLED panel.

[0060] For a specific embodiment, the present invention can also be extended to insert a transparent material with a refractive index N3 between all regions of materials with a first refractive index N1 and a second refractive index N2, wherein N1>N3>N2.

[0061] Basically, as long as the above parameters vary within a specific range, the performance of the present invention can be maintained.

[0062] It is to be understood that the features mentioned above as well as those yet to be explained below can be used not only in the given combination but also in other combinations or alone without departing from the scope of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] The present invention will be described in detail below using embodiments in conjunction with the accompanying drawings, which also disclose the essential technical features of the present invention. It should be particularly noted that these embodiments are only for illustrative purposes, and their contents should not be interpreted as limiting the scope of protection. For example, the description of an embodiment comprising multiple elements or components should not be interpreted as all of these elements or components being necessary for implementation. On the contrary, other embodiments may be implemented by using alternative elements or components, reducing the number of elements, or adding additional elements. Unless otherwise specified, elements or components in different embodiments may be combined with each other. Modifications and variations described in one embodiment may also be applicable to other embodiments. To avoid repetition, the same or corresponding elements in different drawings are represented by the same figure marks and will not be described one by one. Among them:

[0064] Figure 1 is a schematic cross-sectional view of an optical element in the prior art;

[0065] Figure 2 is a schematic cross-sectional view of an optical element in the first embodiment;

[0066] Figure 3 is a schematic cross-sectional view of an optical element in a second embodiment;

[0067] Figure 3a is based on Figure 3 A schematic cross-sectional view of an optical element of a second embodiment of the present invention; and

[0068] Figure 4 is a schematic cross-sectional view of an LCD screen which includes the optical element of the first embodiment in addition to a backlight. DETAILED DESCRIPTION

[0069] The accompanying drawings are not drawn to scale and are only schematic diagrams. In addition, for the sake of clarity, only a small number of light rays are generally shown, but in fact there are a large number of light rays.

[0070] Figure 1 A cross-sectional view of an optical element in the prior art is shown. It can be seen that although the incident light A (from below) can pass through the optical element with the desired deflection through area A1, the incident light B is absorbed by area A2. Since light B (according to the ratio of the lower surface of area A1 and the lower surface of area A2) is absorbed to a greater extent when the light hits the optical element (more precisely, area A2), the light efficiency of such optical elements in the prior art is severely limited.

[0071] In contrast, Figure 2 A schematic cross-sectional view of an optical element in a first embodiment of the present invention is shown. The planar-extended optical element 10 has a first large surface (also called a light incident surface), from which light enters the optical element 10; and a second large surface (also called a light exit surface), from which light leaves the optical element 10. The optical element 10 includes: a plurality of first regions E1 and a plurality of second regions E2, wherein the first regions E1 are at least composed of a transparent material having a first refractive index N1, and the second regions E2 are composed of at least 50% of an opaque material having a second refractive index N2 and at most 50% of a reflective or white scattering material. Figure 2 In the example shown, about 80% of opaque material and about 20% of white scattering material are used. The first area E1 and the second area E2 are arranged alternately in one or two dimensions (preferably periodic, but not necessarily periodic in size) on the surface of the optical element 10. In the entire wavelength range visible to the human eye, the first refractive index N1 is greater than the second refractive index N2. In the second area E2, the opaque material is mainly arranged in the direction of the second large face of the optical element 10, so the reflective or white scattering material is mainly arranged in the direction of the first large face. When observed along a cross-sectional direction perpendicular to the second large face of the optical element 10, the first area E1 and the second area E2 are trapezoidal, at least partially parabolic and / or stepped.

[0072] This ensures that the light incident on the first major surface (i.e., the light incident surface) of the optical element 10 enters the optical element 10 at least partially through the light incident surface of the first region E1, or is incident on the second region E2 that reflects or scatters white light. Depending on the incident angle of the light, the polarization of the light, and the ratio of the first refractive index N1 to the second refractive index N2, a) after propagating unobstructed or being completely reflected within the first region E1, it is re-coupled out at the light exit surface of the corresponding first region E1 (as shown by ray A), or b) it is completely or partially refracted from the first region E1 into the adjacent second region E2, and here, it is absorbed due to the opaque material of the second region E2, or is reflected or scattered due to the reflective or white-scattering material of the second region E2.

[0073] Therefore, with respect to the light rays incident on the first major surface of the optical element 10, the light rays incident on the second major surface of the optical element 10 are restricted in their propagation direction; in addition, at least a part of the light rays incident on the first major surface of the optical element 10 and incident on the second region E2 is also reflected or scattered (exemplarily, see Figure 2 ray B in). According to a specific embodiment, at least 25% of the incident light is reflected or (backward) scattered.

[0074] Preferably, it further includes a cover layer D and a substrate S, both of which have a first refractive index N1, or their refractive indices only deviate slightly from the first refractive index N1, that is, the deviation is less than 0.02.

[0075] Exemplarily, the dimensions and parameters of the optical element are listed below: The width of the first region E1 in the direction of its light incident surface towards the first major surface is D1, and this width is generally smaller than the width D2 of the second region in its light incident surface. For example, the width D1 can be between 10 microns and 70 microns, preferably 25 microns, while the width D2 increases by about 5 microns to 20 microns. Exemplarily, when D1 is 25 microns, D2 is 30 microns. The total height of the first region E1 and the second region E2 can be between 50 microns and 250 microns respectively, preferably 125 microns. The boundary surface between the first region E1 and the second region E2 forms an angle slightly deviating from 0° with the normal line perpendicular to the light incident surfaces of these regions (arranged parallel to each other), for example, between 3° and 12°, preferably 5.5°, where the first region E1 gradually widens towards its light exit surface or the second boundary surface of the optical element. In this configuration, the first refractive index N1 can take values between 1.44 and 1.7, and the second refractive index N2 can take values between 1.35 and 1.6, and always satisfy N2 < N1. For example, N1 can be 1.56 and N2 can be 1.45.

[0076] External factors (eg, pixel width, pixel shape, pixel height, the type of display in which the optical element 10 is used, requirements for propagation direction restriction, and possibly other parameters) may influence the selection of the above dimensions.

[0077] Due to the difference between the first refractive index N1 and the second refractive index N2, the light entering the second region E2 will be refracted and deviate more strongly from the normal before being absorbed in the second region E2, which generally helps to enhance the absorption effect.

[0078] The portion of light incident on the first large surface of the optical element 10 (especially in the second area E2) that is reflected or scattered should generally account for at least 20% to 25% or more, and the light source that can be arranged below it (not in the second area E2) Figure 2 ) is recycled, for example, Figure 4 The backlight 20 shown. Through the focusing effect of the optical element structure, the efficiency of recycling light can also be increased by up to 3 times.

[0079] Therefore, the material having a reflective or white scattering effect in the second area E2 on the first large surface of the optical element 10 reflects at least a portion of the incident light back to its starting point. This reflection can be specular reflection or diffuse reflection.

[0080] Exemplarily, such a reflective or white scattering material may be composed of a transparent material (e.g., paint or other polymer material having a second refractive index N2), in which reflective and / or white scattering particles are doped, so as to achieve a reflective or white scattering effect as a whole. For example, the material located in the second area E2 may be obtained by dispersing nano or micro particles in a transparent paint. Other embodiments are also feasible.

[0081] For example, particles of TiO2 or SiO2, powder / paint mixtures or similar filler materials can be used, which can also be deposited by silver, aluminum or chromium, or coated with a solvent, which then evaporates to form a reflective metal layer. In addition, scattering or reflection effects can also be generated by targeted evaporation or sputtering of the boundary area between the first area E1 and the second area E2, for example, using aluminum, chromium or other metal or dielectric layers. In addition, similar to the use of paint, the corresponding material can also be introduced into the second area E2 in the form of a solution, but the solvent is evaporated, for example, by heating, etc., and the required material remains in the structure accordingly.

[0082] Exemplarily, the opaque material may be composed of a transparent material having a second refractive index N2, such as polymethyl methacrylate (PMMA), polycarbonate, or a polymer generally having a second refractive index N2. The material is doped with absorbent particles, thereby producing an overall opaque effect.

[0083] It is therefore conceivable that the opaque material consists of a paint or a polymer into which graphite particles with a particle size of less than 500 nanometers, black carbon nanoparticles with a particle size of less than 200 nanometers, Fe(II,III)O particles, MnFe2O4 particles, a dye or a dye mixture are mixed as absorbent particles.

[0084] The mass fraction of absorbent particles should be at most 75%. For graphite particles, the mass fraction should only be between 5% and 30% (inclusive). For Fe(II,III)O particles, the preferred mass fraction is between 10% and 75% (inclusive).

[0085] Furthermore, advantageously, when observing the parallel projection perpendicular to the optical element 10, the first area E1 and the second area E2 are arranged alternately in strips on the surface of the optical element, and each area has a plurality of first areas E1 and a plurality of second areas E2. The "periodically alternating" first area E1 and second area E2 does not mean that they must always have the same width and / or height, but means that the first area E1 and the second area E2 always appear alternately. However, their sizes may vary. Therefore, the light propagation direction perpendicular to the strip-shaped area will be limited, while the light propagation direction parallel to the strip-shaped area will not be affected.

[0086] In other embodiments, when viewed along a cross-sectional direction perpendicular to the upper surface of the optical element 10 , the first region E1 and / or the second region E2 is trapezoidal or at least partially parabolic. Figure 2 An exemplary trapezoidal shape is shown, while Figure 3 An exemplary parabolic shape of the optical element 10 in the second embodiment is shown in cross-section, with the dashed lines indicating deviations of the parabolic shape from a trapezoidal shape. Figure 3a The at least partially parabolic shape of the first region E1 and / or the second region E2 when viewed along a cross-sectional direction perpendicular to the upper surface of the optical element 10 is more clearly shown.

[0087] By designing the shape of the first area E1 and the second area E2, the propagation direction of the light emitted from the optical element can be specifically controlled: according to the specific embodiment, the light will be more or less focused on the surface. The "focusing" here does not mean focusing to a focus through the lens optics, but refers to the strong or weak diffusion of the light emitted from the second large surface.

[0088] If the side surface of the boundary surface between the first area E1 and the second area E2 is designed as described above to have Figure 3 and Figure 3aThe parabolic rounded corners shown have two advantages: on the one hand, the molding process in the manufacturing process of the optical element 10 is simplified; on the other hand, the additional focusing effect improves the effective transmittance and optimizes the limitation of the light propagation direction. Figure 2 and Figure 4 As shown, Figure 3 and Figure 3a Light ray B, which is not drawn in the figure, is also reflected.

[0089] In general, it can be determined that the technical solution based on the trapezoidal or parabolic shape can achieve the desired light focusing effect. For example, in combination with the reflective coating on the light incident surface of the optical element 10, an effective transmittance of more than 100% can be achieved, that is, the brightness of the light emitted from the first area E1 is higher than the brightness of the light incident to the first area E1.

[0090] Furthermore, the present invention is also compatible with layers known in the prior art, such as 3M TM DBEF TM (Dual Brightness Enhancement Film), so-called "wire grid" polarizers, and most Brightness Enhancement Films (BEF, Brightness Enhancement Film, prismatic layers). The effective transmittance can be further increased by using such layers. For example, the above exemplary dimensions and parameters can theoretically achieve a 2x brightness gain, which is in addition to the "gain" obtained by DBEF or BEF, and can achieve a "top hat" distribution over a horizontal viewing angle range (+ / -200 from the observer's perspective).

[0091] A method for manufacturing the above optical element 10, the optical element 10 comprises a first region E1 and a second region E2, wherein the first region E1 and the second region E2 are alternately arranged in a one-dimensional sequence or a two-dimensional sequence on the surface of the optical element 10. The method comprises the following steps:

[0092] A transparent material having a first refractive index N1 is used on a substrate S (for the substrate S, see Figure 2 , exemplarily, the substrate S is made of glass or polymer) and the first regions E1 are formed on the substrate, so that a gap is formed between any two first regions E1;

[0093] partially (but not completely) filling the gap with an opaque material having a second refractive index N2 so that the gap is filled to at least 50% of its height, thereby partially forming the second area E2; this may be achieved by one or more filling steps;

[0094] The gap is further filled with a diffusely reflective or specularly reflective material to completely form the second region E2, wherein at most 50% of the height of the second region E2 is constituted by the diffusely reflective or specularly reflective material.

[0095] An optional final step includes: applying a paint or a cover layer D (for the cover layer D, see Figure 2 ) to seal the first region E1 and the second region E2 on the side facing away from the substrate. Preferably, but not necessarily, the cover layer D has the same first refractive index N1 as the substrate S.

[0096] The incident angle of the light entering the first region E1 refers to the geometric incident direction, in particular, the direction vector describing the horizontal incident angle and the vertical incident angle of the light incident on the light incident surface (also referred to as the "lower surface") of the first region E1. In addition to the polarization state of the light, the incident angle is crucial to the propagation of the light in the first region E1 and at the interface with the second region E2.

[0097] For example, when the wavelength is 550 nanometers, the refractive index may be N1=1.6 and N2=1.5. In order to clarify the physical concept, it should be noted here that "refractive index" may refer to the first refractive index N1 or the second refractive index N2 for a specific wavelength (such as 580 nanometers), or may refer to the entire dispersion curve within the visible wavelength range of the human eye. In the case of a dispersion curve, the refractive index difference refers to the difference between two corresponding refractive indices at any selected wavelength λ within the visible wavelength range.

[0098] Generally speaking, for all optical elements 10 , the roughness Ra of the boundary surface between the first region E1 and the second region E2 should be less than or equal to 400 nanometers, preferably less than 100 nanometers, and particularly preferably less than 40 nanometers.

[0099] The present invention is particularly important when the optical element 10 is applied in combination with a display unit (e.g., an LCD panel, an OLED, a microLED, or a display unit based on other display technologies having a pixel structure) or with an illumination device for a transmissive display unit (e.g., an LCD panel). In the latter case, the optical element 10 will be directly integrated into the illumination device for the transmissive display unit 30 (e.g., an LCD panel).

[0100] to this end, Figure 4A schematic cross-sectional view of an LCD screen is shown, which includes, in addition to a backlight 20, the optical element 10 of the first embodiment and an LCD panel 30. This structure is basically applicable to all types of backlights 20, in particular edge lighting (edge ​​lit) and direct lighting (local dimming or matrix LED). In addition to the LCD panel 30, other types of backlit display devices can also be used. Exemplary light rays A and AB are shown here, although there are actually a large number of different light rays. Light ray A passes through the optical element 10 as described above, and then passes through the LCD panel 30. Light ray B is reflected back to the backlight 20, and at least most of it is recycled in the backlight 20, that is, after passing through different layers, the corresponding light returns to the optical element 10 again, which is the reason for its improved efficiency relative to the prior art.

[0101] In this variation, a "DBEF" layer can also be back laminated to the LCD panel 30 to further improve efficiency. The DBEF layer allows polarization recycling, i.e. polarization light that does not match the incident side polarizer is mostly reflected by the DBEF layer and can mostly be recycled.

[0102] The lighting device with optical elements can also be used permanently as a directional backlight and can therefore, for example, be used according to the embodiments of WO2015 / 121398A1 or WO2019 / 002496A1 of the applicant to realize a device that can switch between at least two different brightness distributions, for example, for the illumination of an LCD panel that can be operated in a free viewing mode and in a protected viewing mode.

[0103] The various aforementioned embodiments of the present invention may also be implemented directly on a self-luminous display unit. An OLED panel is particularly suitable, as will be described in detail below. However, other types of self-luminous displays are also feasible.

[0104] For example, this can be achieved in the following manner: a first region E1 of a material having a first refractive index N1 is directly applied or arranged on the light-emitting region of the OLED pixel. A second region E2 having a structure complementary to the first region E1 is applied or arranged on the non-light-emitting region of the OLED panel. In this way, a structure with particularly high light efficiency can be achieved without reducing the resolution of the OLED.

[0105] The invention solves the proposed task: The described planar extended optical element can clearly influence the propagation direction of the incident light. The optical element is low-cost and can be used universally with various types of screens, in particular, without significantly reducing the resolution of the screen. In addition, the optical element can achieve a "top hat" light distribution. At the same time, the optical element improves the effective light transmission efficiency compared to the prior art. By using the optical element in the screen, the diffusion of light can be effectively limited according to the embodiment, the light propagation direction is more concentrated or focused, and thus a privacy effect is achieved.

[0106] The advantages of the present invention are manifold. The above effects are achieved by a single optical element, and the element does not necessarily need to have a special surface structure. In addition, a "top hat" distribution is preferably achieved on the outgoing light, and an arbitrarily high privacy contrast can be achieved in theoretical simulations. When the optical element of the present invention is applied to the backlight of an LCD panel, high lighting density and good light recycling can be achieved. In addition, light propagation limitation in two planes (for example, left / right and up / down at the same time) can be achieved by only one optical element.

[0107] The invention described above can be used in combination with a display device, and is suitable for applications where confidential data needs to be displayed and / or entered, for example, PIN entry or data display at an ATM or payment terminal, password entry or e-mail reading on a mobile device. The invention can also be used in passenger cars, for example, when the driver should not see certain image content of the passengers (such as entertainment programs). In addition, the optical element of the invention can also be used for other technical and commercial purposes. For example, for light orientation in dark field illumination of microscopes, and for light shaping in general for lighting lamps (such as car lights), and for measurement technology.

[0108] Reference numerals

[0109] 10 Optical Components

[0110] 20 Backlight

[0111] 30 LCD Panel

[0112] A. Light

[0113] A1 Area

[0114] A2 Area

[0115] B Ray

[0116] D Covering

[0117] D1 Width of the first region

[0118] D2 The width of the second area

[0119] E1 First Area

[0120] E2 Second Area

[0121] S substrate

Claims

1. A planar extended optical element (10), having a first large surface through which light enters the optical element (10) and a second large surface through which light leaves the optical element (10), the optical element comprising: A plurality of first regions (E1), at least composed of a transparent material having a first refractive index (N1); as well as A plurality of second regions (E2), composed of at least 50% of an opaque material having a second refractive index (N2) and at most 50% of a reflective or white scattering material, wherein the plurality of first regions (E1) and the plurality of second regions (E2) are alternately arranged on the surface of the optical element (10) in a one-dimensional sequence or a two-dimensional sequence, within the entire wavelength range visible to the human eye, the first refractive index (N1) is greater than the second refractive index (N2), and in the plurality of second regions, the opaque material is mainly arranged in the direction of the second large surface of the optical element (10), Wherein, when observed from a cross-sectional direction perpendicular to the second large surface of the optical element (10), the plurality of first regions (E1) and the plurality of second regions (E2) are trapezoidal, at least partially parabolic, and / or at least partially stepped, so that light irradiated onto the first large surface of the optical element (10) at least partially enters the optical element (10) through the light incident surface of the first region (E1) or irradiates the reflective or white scattering second region (E2), and according to the incident angle of the light, the polarization of the light, and the ratio of the first refractive index (N1) to the second refractive index (N2), a) after unimpeded propagation or total reflection in the first region (E1), the light is coupled out again at the light exit surface in the first region (E1), or b) is completely or partially refracted from said first area (E1) to said adjacent second area (E2) and there absorbed by said opaque material of said second area (E2) or reflected or scattered by said reflective or white scattering material of said second area (E2), so that, relative to the light irradiated onto the first large surface of the optical element (10), the light leaving from the second large surface of the optical element (10) is limited in its propagation direction, At least a portion of the light incident on the first large surface of the optical element (10) and irradiating the second area (E2) is reflected or scattered.

2. The optical element (10) according to claim 1, characterized in that The opaque material is composed of a transparent material having the second refractive index (N2), wherein the transparent material is mixed with absorptive particles to achieve an opaque effect.

3. The optical element (10) according to claim 1 or 2, characterized in that: The opaque material is composed of a paint or a polymer doped with graphite particles with a particle size of less than 500 nanometers, black carbon nanoparticles with a particle size of less than 200 nanometers, Fe(II,III)O particles, MnFe2O4 particles, dyes, or dye mixtures as absorbent particles.

4. The optical element (10) according to any one of claims 1 to 3, characterized in that: The reflective or white scattering material is composed of a transparent material doped with reflective and / or white scattering particles to achieve a reflective or white scattering effect as a whole.

5. The optical element (10) according to any one of claims 1 to 4, characterized in that The refractive index difference between the first refractive index (N1) and the second refractive index is less than 0.

2.

6. The optical element (10) according to any one of claims 1 to 5, characterized in that When observing a parallel projection perpendicular to the optical element (10), the first area (E1) and the second area (E2) are alternately arranged in a strip shape on the surface of the optical element (10).

7. The optical element (10) according to any one of claims 1 to 5, characterized in that When observing a parallel projection perpendicular to the optical element (10), the first area (E1) is distributed on the surface of the optical element (10) in a dot shape, a circle, an ellipse, a rectangle or a hexagon, and the second area (E2) is complementary to the shape thereof.

8. A method for manufacturing an optical element (10) according to any one of the preceding claims, wherein the optical element comprises a plurality of first regions (E1) and a plurality of second regions (E2), wherein the plurality of first regions (E1) and the plurality of second regions (E2) are alternately arranged in a one-dimensional sequence or a two-dimensional sequence on a surface of the optical element (10), the manufacturing method comprising the following steps: Forming the plurality of first regions (E1) on a substrate (S) using a transparent material having a first refractive index (N1), wherein a gap exists between any two adjacent first regions (E1); Partially filling the gap with an opaque material having a second refractive index (N2) so that the gap is filled to at least 50% of its height to partially form the plurality of second regions (E2); The gaps are further filled with diffuse or specular reflective material to completely form the plurality of second regions (E2).

9. The method according to claim 8, further comprising: As a final step, a paint or coating is applied to the first regions and the second regions on the side facing away from the substrate (S) to seal the first regions and the second regions.

10. A light emitting device for a transmission screen, comprising: a backlight (20), and The optical element (10) according to any one of claims 1 to 8, wherein the propagation direction of the light emitted by the light emitting device is limited due to the optical effect of the optical element (10).

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