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

Abstract

The present application relates to an optical element (10) having a first large surface that is incident on the optical element (10) and a second large surface that is emitted from the optical element (10), wherein the optical element (10) includes a plurality of first regions (E1) made of a transparent material having at least a first refractive index (N1); and a plurality of second regions (E2) made of an opaque material having at least 50% of a second refractive index (N2) and at most 50% of a reflective material or white scattering material, wherein the first refractive index (N1) is greater than the second refractive index (N2), and the optical element (10) At least a portion of the light irradiated onto the first large surface of the optical element (10) enters the optical element (10) through the light incident surface of the first region (E1), or is irradiated onto the second region (E2) which is reflected or white-scattered, and a) propagates without obstruction or is perfectly reflected within the first region (E1) and is then recombined at the light exit surface in the first region (E1), or b) is refracted from the first region (E1) to the adjacent second region (E2) and absorbed in that region, or is reflected or scattered by the reflective or white-scattering material of the second region (E2). As a result, with respect to the light irradiated onto the optical element (10), the light away from the second large surface of the optical element (10) is restricted to its direction of propagation, 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, significant progress has been made in expanding the viewing angle of LCDs. However, in some cases, a very wide viewing area for the screen often becomes a disadvantage. More and more information (e.g., bank data or other personal and sensitive data) can be obtained from mobile devices such as notebook computers and tablet computers. Therefore, it is necessary to control who can view this sensitive data. To share the information on the screen with others, a wide viewing angle (e.g., viewing travel photos or advertisements) can be selected. Also, when the information on the screen is to be treated as private, it is necessary to narrow the viewing angle.

[0002] The same problem exists in vehicle structures. When the engine is on, the driver cannot pay attention to the screen content (e.g., entertainment programs), but passengers want to view these contents while driving. Therefore, a screen that can switch between two display modes is required.

Background Art

[0003] Additional films using microlouvers have already been used in mobile display devices to achieve visual data protection. However, such additional films are not controllable or switchable, and can only be manually pasted and removed. When not needed, this additional film also needs to be peeled off and displayed separately. Another major drawback of using such a louver film is that there is a certain light loss.

[0004] US6765550 B2 describes a peeping prevention barrier using such microlouvers. Its drawbacks are that the filter needs to be mechanically removed and attached, and there is light loss in the protection mode.

[0005] US5993940 A describes the use of the film, which has small prism strips uniformly arranged on its surface to achieve an anti-peeping mode, but the development and production costs are quite high.

[0006] In the WO2012 / 033583 A1, switching between free mode and restricted mode is done by liquid crystal control between the so-called "color" layers, which leads to light loss and significantly increases costs.

[0007] US2012 / 0235891 A1 describes a very complex screen backlight. According to Figures 1 and 15, not only are multiple light guides used, but other complex optical elements such as microlens elements 40 and prism structures 50 can also be used to convert rear illumination light to front illumination light. This is expensive, complex, and causes light loss. According to the modification shown in Figure 17 of US2012 / 0235891 A1, both light sources 4R and 18 produce light with a narrow emission angle, and the light from the rear light source 18 is first converted to light with a wide emission angle in a complex manner. As mentioned above, such a complex conversion greatly reduces brightness.

[0008] JP2007-155783 A utilizes a special optical surface 19, which is complex to calculate and manufacture, to deflect light to different narrow or wide regions depending on the angle of incidence. This structure is similar to a Fresnel lens. However, depending on the interference edge, the light may be deflected in an undesirable direction. Therefore, it is unclear whether a significant light distribution can be achieved.

[0009] US2013 / 0308185 A1 describes a special stepped light guide that, when combined with a transmissive image display device (e.g., a liquid crystal display), can produce a screen that can switch between a free-view mode and a restricted-view mode. Its drawbacks include the fact that the restricted visual effect can only be used on the left / right or upper / lower side, and not simultaneously on the left / right / upper / lower side, which is necessary in certain payment processes. Also, even in the restricted-view mode, residual light can be seen from the obscured field of view.

[0010] WO2015 / 121398 A1 describes a screen having two operating modes, where scattering particles present within the volume of each light guide effectively enable the switching of operating modes. However, scattering particles made of polymer generally have the disadvantage of emitting light from two large surfaces, resulting in approximately half of the useful light being directed in the wrong direction, i.e., towards the backlight, and this light is not recycled to a structurally sufficient extent. In addition, in some cases, especially at high densities, the scattering particles made of polymer in the light guide volume produce a scattering effect, reducing the anti-peeping effect in protective mode.

[0011] WO2022 / 078942 A1 and DE102020008062 A1 disclose optical elements capable of structuring transmitted light in its propagation direction, respectively. The drawback is that light absorbed in the opaque region completely loses its optical balance.

[0012] DE102021120469 B3 describes an optical element that selectively restricts the direction of light propagation based on electrophoretic particles. Its drawback is that switching between operating modes takes several seconds.

[0013] WO2021 / 032735 A1 and DE102020007974 B3 both disclose optical elements with variable transmittance. However, there are limitations due to the movement of electrophoretic particles and the relatively long switching time based on electrowetting. Furthermore, optical recovery was not possible with opal particles.

[0014] The above methods and apparatus generally have the disadvantages of significantly reducing the brightness of the basic screen, and / or requiring complex and expensive optical elements to achieve mode switching, and / or providing only limited privacy protection, and / or reducing the resolution in free viewing mode, and / or having only a narrow viewing area, with brightness dropping sharply within the angular spectral range and the brightness of the image seen by the viewer being very uneven. Furthermore, the use of emission angle limiting methods is increasing efforts to avoid reflections (e.g., reflections from the windshield). The drawback of using commercially common louver filters is that while there is some light loss, the light distribution with respect to angle exhibits a triangular shape, which results in the observer seeing an uneven image. [Overview of the project]

[0015] The objective of this invention is to develop a planar optical element that can clearly influence the propagation direction of incident light. This optical element has low implementation costs and can generally be used with different types of screens. Thus, the screen resolution is hardly reduced, or if reduced, is almost negligible. Furthermore, this optical element can, in principle, achieve a top-hat light distribution. That is, for example, in an angular region of at least 7 degrees centered on the peak radiation direction, the luminance reduction does not exceed 35%, or the angular luminance distribution is as close to a rectangle as possible. Additionally, this optical element is required to have improved effective light transmittance compared to conventional technology.

[0016] The present invention achieves the above objective by an optical element that extends in a planar manner. The optical element comprises a first large surface into 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 made of a transparent material having at least a first refractive index N1; on the other hand, the optical element includes a plurality of second regions E2 made of an opaque material having at least 50% a second refractive index N2 and at most 50% (but at least 5% or 10%) a reflective material or a white scattering material. The plurality of first regions E1 and the plurality of second regions E2 are arranged alternately on the surface of the optical element in a one-dimensional or two-dimensional order. Preferably, this order is periodic, but not necessarily dimensionally periodic. Also, 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 plurality of second regions E2, the opaque material is arranged mainly in the direction of the second large surface of the optical element. When viewed from a direction perpendicular to the cross-section of the second large surface of the optical element, 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.

[0017] As a result, at least a portion of the light incident on the first large surface (incident side) of the optical element is incident on the optical element from multiple incident surfaces of the first region E1, or irradiated onto the reflected or white-scattered second region E2, so that, depending on the angle of incidence of the light, the polarization of the light, and / or the ratio of the first refractive index (N1) to the second refractive index (N2), a) the light propagates or is totally reflected through the first region E1 without any problems and is then recombined at the light output surface in the corresponding first region E1, and b) the light is completely or partially refracted from the first region E1 to the adjacent second region E2 and absorbed by the opaque material of the second region E2, or reflected or scattered by the reflective material or white-scattering material of the second region E2.

[0018] Therefore, with respect to light incident on the optical element from the first large surface, the light emitted from the second large surface of the optical element is restricted to its propagation direction. In addition, at least a portion of the light incident on the optical element in the second region 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.

[0019] Accordingly, according to this application, when viewed from a cross-sectional direction perpendicular to the second large surface of the optical element, the first region E1 and the second region E2 exhibit a trapezoidal, at least partially parabolic, and / or stepped shape. The first region E1 and the second region E2 having these shapes can appropriately influence the propagation direction of light emitted from the optical element. Depending on the specific design, the light forms a strong or weak focus on the plane. Furthermore, peak shift is achieved by the inclination of the interface between the first region E1 and the second region E2, which have parallelogram cross-sections. The advantage of the trapezoidal shape is that the angular distribution can be focused better, further improving the prevention of side-viewing. In particular, the first region E1 of the trapezoidal cross-section is preferred in which the width of the second large surface (light emission side) is greater than the width of the first large surface (light incidence side), and is especially preferred to be approximately isosceles trapezoidal.

[0020] In actual production, due to technical limitations, the above-mentioned trapezoidal, at least partially parabolic, and / or stepped trapezoidal shapes can usually only be realized approximately, and therefore include relatively deviated shapes due to technical reasons. The design of at least partially parabolic shapes may be desired, but may also be due to technical limitations in manufacturing; for example, if a trapezoidal shape cannot be manufactured accurately, it may exhibit a partially parabolic shape. However, this does not affect the effect of the present invention. Also, exemplary, when viewed from a cross-sectional direction perpendicular to the second larger surface, trapezoidal, parabolic, and / or stepped shapes may appear alternately. The trapezoidal shape may be designed asymmetrically to achieve a shift in the luminance distribution relative to the normal. Instead of a linear trapezoidal shape, the sides of the interface between the transparent first region E1 and the absorbing second region E2 may be rounded. This has two advantages: it simplifies the molding process during the manufacturing of the optical element, while the additional focusing effect can improve the effective transmittance and restrict the direction of light propagation.

[0021] Opaque materials do not necessarily need to have 100% opacity, but the highest possible opacity should be desired. Based on the desired luminance distribution with respect to the transmission curve, the opacity required for a particular application scene can be determined by optical tracing simulation. Due to the difference between the first refractive index N1 and the second refractive index N2, light incident on the second region E2 is refracted before it is absorbed, causing it to deviate more significantly from the normal. This enhances the absorption effect.

[0022] Furthermore, due to the refractive index difference between the first region E1 and the second region E2 (the difference between the first refractive index N1 and the second refractive index N2), some of the light is re-reflected back to the first region E1 by total internal reflection and continues to be used for light balance. As a result, when light passes through the optical element, a different angular spectrum is generated compared to when there is no refractive index difference. Therefore, the optical element can basically achieve a top-hat light distribution. This means that, as explained at the beginning, the change in luminance distribution with respect to angle (for example, the horizontal angle from a standing or sitting observer) is as close to a rectangle as possible. Depending on the specific design, the luminance within an angular range of at least 7 degrees around the peak radiation direction can be reduced by 35% or less, and even by 25% or less. In addition, good efficiency can be achieved through the presence of reflection and white scattering materials.

[0023] The optical element may further include a substrate S and / or a cover layer D arranged to sandwich the first region E1 and the second region E2.

[0024] Of the light incident on the first large surface of the optical element, the portion that is reflected or scattered (especially the second region E2) usually needs to account for at least 20% to 25% or more, and for example, it can be recycled by the lower light source. The focusing effect of the above configuration of the optical element can also increase the efficiency of light recovery by up to three times.

[0025] Therefore, the material having a reflection or white scattering effect in the second region E2 located on the first large surface of the optical element reflects at least a part of the incident light from its origin. In this case, at least a part of the reflection may be specular reflection or diffuse reflection. Exemplarily, in the second region E2, the ratio of the opaque material to the reflective material or the white scattering material may be a) 50 / 50, b) 60 / 40, c) 70 / 30, e) 80 / 20, f) 75 / 25 (preferably, g) 90 / 10. Other means are also possible and are included within the scope of the present invention.

[0026] To simplify the manufacturing process, the above reflective or white scattering material may be composed of a transparent material having a second refractive index N2, applied to the filling process, and composed of a transparent material having a refractive index smaller or larger than the second refractive index N2, and the material is doped with reflective and / or white scattering particles to achieve an overall reflective or white scattering effect. The material of the second region E2 can be realized, for example, by dispersing nano-particles or micro-particles in a transparent lacquer to form a mixture.

[0027] As particles, for example, particles such as TiO2 and SiO2, fillers such as powder-lacquer mixtures can be considered, or silver, aluminum, chromium, etc. can be vapor-deposited, a solvent can be applied, and the solvent can be evaporated to form a reflective metal layer. Also, a scattering or reflection effect can be generated by directionally vapor-depositing or sputtering the boundary region between the first region E1 and the second region E2, for example, using aluminum, chromium, or other metal or dielectric layers. Also, similar to the lacquer, the corresponding material can be introduced into the second region E2 as a solution, but at this time, the solvent is evaporated, and for example, by means of heating or the like, the necessary material remains in the corresponding structure.

[0028] Exemplarily, the opaque material is composed of a transparent material having a second refractive index N2, and by doping the material with absorbent particles, an overall opaque effect is produced.

[0029] Therefore, the opaque material can be considered to be composed of a lacquer or polymer mixed with absorbent particles such as graphite particles having a particle size of less than 500 nm, black carbon nanoparticles having a particle size of less than 200 nm, Fe(II,III)O particles, MnFe-attached O-attached particles, dyes or dye mixtures. The mass fraction of the absorbent particles is at most 75%. The graphite particles are preferably 5% to 30% by mass. The preferred mass fraction of the Fe(II,III)O particles is 10% to 75%.

[0030] 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.

[0031] Furthermore, it is preferable that the first region E1 and the second region E2 are arranged alternately in a stripe pattern on the surface of the optical element (10) when viewed in a parallel projection perpendicular to the optical element. The first region E1 and the second region E2, which alternate periodically, do not necessarily have to always have the same width and / or height; it simply means that the first region E1 and the second region E2 always appear alternately. However, their size is variable. For this reason, the direction of light propagation perpendicular to the stripe region is restricted, while the direction of light propagation parallel to the stripe region is unaffected.

[0032] In contrast, in other embodiments, the first region E1 is distributed on the surface of the optical element in a point-like, circular, elliptical, rectangular, hexagonal, or other two-dimensional shape when viewed in a parallel projection perpendicular to the optical element, and the shape of the second region E2 is complementary thereto. Thus, the direction of light propagation is restricted within at least two planes perpendicular to the surface of the optical element. In practice, the role of such an optical element is usually to focus the direction of light propagation of transmitted light to angles close to or parallel to the vertical centerline of the optical element. Here, "close" means that the angle from the vertical centerline or parallel line (depending on the specific design) is less than 25° or less than 30°.

[0033] The first region E1 and the second region E2 may have other shapes. In order to maintain the functionality of the present invention, it is important to achieve a rapid change in the refractive index with as little air gap as possible by making the first region E1 and the second region E2 optically adjacent to each other.

[0034] Furthermore, a lens structure L is provided on the light-emitting side of at least a portion of the first region E1 (preferably on all of the first region E1), and is preferably a convex lens structure. This allows for better focusing of the light passing through the optical element.

[0035] In special application scenarios, it is advantageous for at least one first region E1 to be formed on the optical element, such that the minimum dimension when viewed in a parallel projection perpendicular to the optical element is at least 20 times the minimum dimension of all second regions E2 when viewed in a parallel projection perpendicular to the optical element. Therefore, within the above-mentioned at least one first region E1 (excluding its edges, losses, and misalignment), the propagation direction of light emitted from the light output side of the optical element is not restricted with respect to light incident on the light incidence side of the optical element.

[0036] Furthermore, in addition to the first region E1 and the second region E2, other regions E3, E4, ... may be formed that have different parameters in terms of shape and / or refractive index from the first region E1 and the second region E2, so that the restriction on the propagation direction of light emitted from the optical element after passing through these other regions E3, E4, ... is different from that of the first region E1.

[0037] The present invention also includes a method for manufacturing an optical element having 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 arranged alternately in a one-dimensional or two-dimensional order on the surface of the optical element (10). The method includes the following steps: A step of forming a plurality of first regions E1 on a substrate S using a transparent material having a first refractive index N1, and forming a gap between any two of the plurality of first regions E1 by, for example, a nanoimprint process (e.g., roll-to-roll ultraviolet nanoimprint); The step of partially (but incompletely) 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, which can be achieved by one or more filling steps; The next step is to further fill the gaps with diffuse or specular reflective material to completely form the second region E2; up to 50% of the height of the second region E2 is made up of diffuse or specular reflective material, and the material used here does not need to be 100% opaque; usually, at least 25% opacity is sufficient.

[0038] Preferably, as a final step, the method further includes sealing the plurality of first regions and the plurality of second regions by applying a lacquer or coating to the side of the plurality of first regions and the plurality of second regions that is facing away from the substrate (S).

[0039] In principle, any material can be used instead of diffuse or specular reflecting material, but it is necessary to apply one or more diffuse or specular reflecting materials to the interface between the first region E1 and the second region E2.

[0040] Alternatively, an OCA (Optically Clear Adhesive) laminate film may be used as a covering layer to seal the structure and protect it from mechanical stress and environmental conditions.

[0041] Alternatively, a film called Dual Brightness Enhancement Film (DBEF) may be laminated, for example, by 3M. TM This thin film not only functions as a protective layer, but its effective transmittance is also improved by polarization recovery. When the transmitted polarization direction is perpendicular to the main propagation direction in the first region E1, the optical function of the structure is sensitive to polarization, and the focusing of light is further improved.

[0042] The angle of incidence at which light or (synonymous) is incident on the first region E1 is the geometric direction of incidence, and more specifically, the direction vector of the light. This direction vector represents the horizontal and perpendicular angles of incidence of the light with respect to the light incidence surface (also called the "bottom surface") of the first region E1. The propagation of light at such an interface between the first region E1 and the second region E2 is more important than the polarization state of the light.

[0043] To clarify the physical concept and to re-emphasize it here, the term “refractive index” may refer to a first refractive index N1 or a second refractive index N2 for a specific wavelength (e.g., 580 nm), or it may refer to the entire dispersion curve within the visible light 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 an arbitrarily selected wavelength λ within the visible light wavelength range.

[0044] If a substrate and / or coating layer is present, it can be selectively constructed from the same material as the first region E1.

[0045] Furthermore, it is preferable to optimize the effect by placing polarizers (reflective polarizers if necessary) below and / or above the optical elements. By controlling the polarization state with polarizers, the efficiency of utilizing refractive index conversion can be improved. In addition, Fresnel reflection can be effectively reduced by utilizing the p-polarization state of the incident or emitted light, that is, the restriction of the direction of light propagation can be optimized.

[0046] In general, for all optical elements, the roughness Ra of the interface between the first region E1 having a first refractive index N1 and the second region E2 having a second refractive index N2 must be 400 nm or less, preferably less than 100 nm, and particularly preferably less than 40 nm. The present invention is of particular significance when the optical element described above is applied in combination with an illumination device used in a display unit (e.g., an LCD panel, OLED, microLED, or other display technology having a pixel structure) or a transmissive display unit (e.g., an LCD panel). In the latter case, the optical element is directly incorporated into the illumination device for a transmissive display device such as an LCD panel. The illumination device can function continuously as a directional backlight and can be applied exemplary to the embodiments described in applicant WO2015 / 121398 A1 or WO2019 / 002496 A1.

[0047] Alternatively, if the optical element of the present invention is positioned in front of the observation direction of the display unit, the display unit further includes an optical device that focuses the light emitted from each pixel of the display device onto the side opposite to the first region E1. This can be achieved, for example, by a microlens array or lenticular lens having a period approximately the same as the pixel width (or pixel height). Ideally, the period of the first region E1 should match the period of the pixel width or height. This allows for particularly high transmission efficiency to be achieved.

[0048] The various embodiments of the present invention described above may be directly implemented in a self-emissive display unit. Among these, the most suitable are OLED panels, which will be described in more detail below. Of course, other types of self-emissive displays may also be used.

[0049] For example, this is achieved by directly providing a first region E1 made of a first refractive index N1 material in the light-emitting region of an OLED pixel. A second region E2 having a structure complementary to the first region E1 is provided in the non-light-emitting region of the OLED panel.

[0050] With respect to a particular embodiment, the present invention can also be extended to insert a transparent material having a refractive index N3 between all regions of a material having a first refractive index N1 and a second refractive index N2.

[0051] Basically, the performance of the present invention is maintained as long as the above parameters change within a specific range. It should be understood that the above features and the features described below may be used not only in the predetermined combinations but also in other combinations, or individually, without departing from the scope of the present invention. [Brief explanation of the drawing]

[0052] The present invention will be described in detail below using embodiments combined with drawings that disclose the essential technical features of the present invention. These embodiments are merely illustrative and should not be interpreted as limiting the scope of protection. For example, in the description of embodiments including multiple elements or components, not all elements or components are necessarily essential. Conversely, other embodiments may be implemented using alternative components or components, a reduction in the number of components, or additional components. Unless otherwise specified, elements or components in different embodiments can be combined with each other. Modifications and changes described for one embodiment are applicable to other embodiments. To avoid duplication, identical or corresponding elements in different drawings are denoted by the same reference numerals, and redundant descriptions are omitted. However, [Figure 1] Figure 1 is a schematic cross-sectional view of a conventional optical element. [Figure 2] Figure 2 is a schematic cross-sectional view of the optical element of Example 1. [Figure 3] Figure 3 is a schematic cross-sectional view of the optical element in the second embodiment. [Figure 3a] Figure 3a is a schematic cross-sectional view of an optical element based on the second embodiment of Figure 3. [Figure 4] Figure 4 is a schematic cross-sectional view of an LCD screen including an optical element in the first embodiment, in addition to the backlight. [Modes for carrying out the invention]

[0053] The drawings are not drawn to scale and are only schematic. Also, for clarity, only a small amount of light is usually shown, but in reality, a large amount of light exists.

[0054] Figure 1 is a cross-sectional view of a conventional optical element. It can be seen that light A incident (from below) can pass through region A1 and through the optical element with the desired deflection, but incident light B is absorbed in region A2. Light B (depending on the ratio of the lower surface of region A1 to the lower surface of region A2) is absorbed more when the optical element (more precisely, region A2) is irradiated with light, so the optical efficiency of conventional optical elements has been greatly limited.

[0055] In contrast, Figure 2 is a schematic cross-sectional view of an optical element according to the first embodiment of the present invention. This planar optical element (10) has a first large surface to which light is incident (also called the light incident surface) and a second large surface to which light is emitted (also called the light emission surface). The optical element (10) has a plurality of first regions E1 made of a transparent material having at least a first refractive index N1, and a plurality of second regions E2 made of an opaque material having at least 50% of a second refractive index N2 and 50% or less of a reflective material or white scattering material. In the example shown in Figure 2, about 80% is opaque material and about 20% is white scattering material. The first regions E1 and the second regions E2 are arranged alternately on the surface of the optical element (10) in a one-dimensional or two-dimensional manner (preferably periodic, but not necessarily periodic in dimensions). Across 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 region E2, the opaque material is mainly aligned in the direction of the second large surface of the optical element (10), while the reflective material or white scattering material is mainly aligned in the direction of the first large surface. The first region E1 and the second region E2 are trapezoidal, at least partially parabolic and / or stepped when viewed from a cross-sectional direction perpendicular to the second large surface of the optical element (10).

[0056] As a result, at least a portion of the light irradiated onto the first large surface, which is the light incident surface of the optical element (10), can be incident onto the optical element (10) from the light incident surface of the first region E1, or irradiated onto the second region E2, which is reflected or white-scattered. Depending on the angle of incidence of the light, the polarization of the light, and the proportional relationship between the ratio of the first refractive index (N1) to the second refractive index (N2), a) the light propagates without hindrance or is completely reflected within the first region E1 and then recombined (as shown by light A) at the corresponding light-emitting surface of the first region E1, or b) the light is completely or partially refracted from the first region E1 and enters the adjacent second region E2, where it is absorbed by the opaque material of the second region E2, or reflected or scattered by the reflective or white-scattering material of the second region E2.

[0057] Therefore, for the light irradiated onto the first large surface of the optical element (10), the light irradiated onto the second large surface of the optical element (10) is restricted in its propagation direction, and at least a part of the light incident on the first large surface of the optical element (10) and irradiated onto the second region E2 is reflected or scattered (exemplarily, refer to light B in FIG. 2). According to a specific embodiment, at least 25% of the incident light is reflected or (backward) scattered. Preferably, it further includes a coating layer D and a substrate S. Both of them have the first refractive index N1 or their refractive indices deviate slightly from the first refractive index N1, that is, the deviation is less than 0.02.

[0058] Exemplarily, the size and parameters of the optical element are listed below: The width in the direction where the light incident surface of the first region E1 faces the first large surface is D1. This width is usually smaller than the width D2 on the light incident surface of the second region. For example, the width D1 is 10 μm to 70 μm, preferably 25 μm, and the width D2 increases by about 5 μm to 20 μm. Exemplarily, when D1 is 25 μm, D2 is 30 μm. The total height of the first region E1 and the second region E2 is 50 μm to 250 μm, preferably 125 μm respectively. The interface between the first region E1 and the second region E2 forms an angle slightly deviated by about 0° with respect to the normal of the light incident surface (provided parallel to each other) perpendicular to these regions, for example, between 3° and 12°, preferably 5.5°. The first region E1 gradually expands toward the direction of its light exit surface or the second interface of the optical element. In this arrangement, the first refractive index N1 can take values between 1.44 and 1.7, the second refractive index N2 can take values between 1.35 and 1.6, and always satisfies N2 < N1. For example, N1 is 1.56 and N2 is 1.45.

[0059] External factors (such as pixel width, pixel shape, pixel height, the type of display used for the optical element (10), requirements for the restriction of the propagation direction, and possible other parameters) can all affect the selection of the above sizes.

[0060] Due to the difference between the first refractive index N1 and the second refractive index N2, light entering the second region E2 is refracted so as to move more strongly away from the normal before being absorbed in the second region E2. This enhances the absorption effect.

[0061] Of the light incident on the first large surface of the optical element (10), the portion that is reflected or scattered in the second region E2 should typically account for at least 20% to 25%, and the backlight 20 shown in Figure 4 can be recycled in a light source (not shown in Figure 2) located below it. Due to the focusing effect of the optical element's structure, the efficiency of light recovery can also be improved by up to three times.

[0062] Therefore, a material having reflective or white scattering properties located in the second region E2 on the first surface of the optical element (10) reflects at least a portion of the incident light back to its origin. This reflection may be specular or diffuse.

[0063] Exemplary, such reflective or white-scattering materials consist of a transparent material (e.g., lacquer or another polymer material having a second refractive index N2) that is doped with reflective and / or white-scattering particles to achieve an overall reflective or white-scattering effect. Materials located in the second region E2 can be obtained, for example, by dispersing nanoparticles or microparticles in a transparent lacquer. Other implementations are also possible.

[0064] As particles, for example, particles such as TiO2 or SiO2, or fillers such as powder / lacquer mixtures can be used. Alternatively, silver, aluminum, chromium, etc., can be deposited, or a solvent can be applied and the solvent evaporated to form a reflective metal layer. Furthermore, scattering or reflection effects can be generated by directional deposition or sputtering in the boundary region between the first region E1 and the second region E2, for example, by using aluminum, chromium, or other metals or dielectric layers. In addition, similar to lacquer, the corresponding material can be introduced into the second region E2 as a solution, in which case the solvent evaporates and the required material remains in the structure by means of heating, for example.

[0065] Exemplary, the opaque material may consist 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 opaque effect is achieved by doping this material with absorbent particles. Therefore, the opaque material may consist of a lacquer or polymer mixed with absorbent particles such as graphite particles with a particle size of less than 500 nm, black carbon nanoparticles with a particle size of less than 200 nm, Fe(II,III)O particles, MnFe-attached O-attached particles, and dyes or dye mixtures. The mass fraction of absorbent particles is a maximum of 75%. Graphite particles are preferably 5% to 30% by mass. The preferred mass fraction of Fe(II,III)O particles is 10% to 75%.

[0066] Furthermore, it is preferable that the first region E1 and the second region E2 are arranged alternately in a stripe pattern on the surface of the optical element (10) when viewed in a parallel projection perpendicular to the optical element, and that each region has multiple first regions E1 and multiple second regions E2. The periodically alternating first regions E1 and second regions E2 do not necessarily have to always have the same width and / or height, meaning that the first regions E1 and second regions E2 always appear alternately. However, their size is variable. For this reason, the direction of light propagation perpendicular to the stripe regions is restricted, while the direction of light propagation parallel to the stripe regions is unaffected.

[0067] In other embodiments, the first region E1 and / or the second region E2 are trapezoidal or at least partially parabolic when viewed from a cross-sectional direction perpendicular to the upper surface of the optical element (10). Figure 2 is a diagram showing an example of a trapezoidal shape, and Figure 3 is a cross-sectional view showing an example of a parabolic shape of the optical element (10) in the second embodiment, where the dashed line indicates a deviation from the trapezoidal shape. Figure 3(a) more clearly shows the parabolic shape of at least a portion of the first region E1 and / or the second region E2 when viewed from a cross-sectional direction perpendicular to the upper surface of the optical element (10). Such a shape design of the first region E1 and the second region E2 allows for directional control of the propagation direction of light emitted from the optical element, and according to specific embodiments, the light forms a strong or weak focus on the surface. Here, "focusing" does not mean optically focusing to a single focal point by a lens, but rather means that the light emitted from the second large surface is strongly or weakly diffused.

[0068] When the side surface of the interface between the first region E1 and the second region E2 is designed to have a parabolic curvature as shown in Figures 3 and 3a, there are two advantages: the molding process in the manufacturing of the optical element (10) is simplified, while the effective transmittance is improved due to an additional focusing effect, and the restriction of the light propagation direction is optimized. As with Figures 2 and 4, light B, which is not depicted in Figures 3 and 3a, is also reflected.

[0069] In short, it can be confirmed that technical proposals based on trapezoidal or parabolic shapes can achieve the desired light focusing effect. For example, by providing a reflective coating on the light incident surface of the optical element (10), an effective transmittance of over 100% can be obtained, where the brightness of the light emitted from the first region E1 is higher than the brightness of the light incident on the first region E1.

[0070] Furthermore, the present invention relates to known layers in the prior art, such as 3M TMThis material is compatible with DBEF (Double Brightness Enhancement Film), so-called "wire grid" polarizers, and most brightness enhancement films (BEF, Brightness Enhancement Film, prism layer). Such layers can further increase effective transmittance. For example, the exemplary size and parameters described above can theoretically achieve a 2x brightness gain, which is an additional gain beyond the "gain" obtained by DBEF or BEF, and can achieve a "top hat" distribution within the horizontal viewing angle range (+ / -200 from the observer's perspective).

[0071] A method for manufacturing the optical element (10) described above, comprising a first region E1 and a second region E2, wherein the first region E1 and the second region E2 are arranged alternately in one or two dimensions on the surface of the optical element (10). The method includes the following steps.

[0072] A gap is formed between any two first regions E1 by molding a first region E1 on a substrate S (see Figure 2 for the substrate S, which is exemplified by glass or polymer) using a transparent material having a first refractive index N1. The second region E2 is partially formed by partially (incompletely) filling the gap with an opaque material having a second refractive index N2, filling the gap to at least 50% of its height, and may be achieved by one or more filling steps. The gaps are further filled with diffuse reflective material or specular reflective material to completely form the second region E2, and up to 50% of the height of the second region E2 is composed of diffuse reflective material or specular reflective material.

[0073] A selective final step includes sealing the sides of the first region E1 and the second region E2 away from the substrate by applying a lacquer or a covering layer D (see Figure 2 for covering layer D). Preferably, the covering layer D has a first refractive index N1, similar to the substrate S.

[0074] The angle of incidence of light into the first region E1 is the geometric direction of incidence, and in particular, it is a direction vector that describes the horizontal and perpendicular angles of incidence of light to the light incidence surface (also called the "bottom surface") of the first region E1. The angle of incidence is important not only for the polarization state of light, but also for the propagation of light in the first region E1 and for the propagation of light at the interface with the second region E2.

[0075] For example, if the wavelength is 550 nm, the refractive indices may be N1=1.6 and N2=1.5. To clarify the physical concept, as needs to be explained here, “refractive index” may refer to the first refractive index N1 or the second refractive index N2 for a specific wavelength (e.g., 580 nm), or it may refer to the entire dispersion curve within the visible light 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 an arbitrarily selected wavelength λ within the visible light wavelength range.

[0076] In general, for all optical elements (10), the roughness Ra of the interface between the first region E1 and the second region E2 must be 400 nm or less, preferably less than 100 nm, and particularly preferably less than 40 nm.

[0077] The present invention is particularly significant when the optical element (10) is applied in combination with an illumination device used in a display unit (for example, an LCD panel, OLED, microLED, or a display unit based on other display technologies having a pixel structure) or a transmissive display unit (for example, an LCD panel). In the latter case, the optical element (10) is directly incorporated into the illumination device of the transmissive display unit 30, such as an LCD panel.

[0078] Therefore, Figure 4 shows a principle cross-sectional view of an LCD screen, which further includes the optical element (10) and LCD panel 30 in the first embodiment, in addition to the backlight 20. This configuration is basically applicable to different types of backlights 20, particularly edge lighting and direct lighting. Display devices with backlight types other than the LCD panel 30 may also be used. Here, light A and light AB are given as examples, but in reality, there are many different types of light. As mentioned above, light A passes through the optical element (10) and then through the LCD panel 30. Light B is reflected by the backlight 20, and at least a large portion is collected by the backlight 20, meaning that after passing through different layers, the corresponding light returns to the optical element (10), which is the reason for the improved efficiency compared to the conventional technology.

[0079] In this modified version, the back surface of the "DBEF" layer may be laminated onto the LCD panel 30 to further improve efficiency. The DBEF layer allows most of the polarized light that is not aligned with the incident polarizer to be reflected and recovered.

[0080] Since the lighting device having optical elements can also be used permanently as a directional backlight, it can be used, exemplary, according to the embodiments of the applicant's WO2015 / 121398 A1 or WO2019 / 002496 A1, and can switch between at least two different luminance distributions, for example, used for illuminating an LCD panel, which can operate in free-view mode and protected-view mode.

[0081] Each embodiment of the present invention described above may be directly mounted on a self-emissive display device. OLED panels are particularly preferred and will be described in detail below. However, other types of self-emissive displays may also be used.

[0082] For example, this can be achieved by directly coating or placing a first region E1 of a material having a first refractive index N1 onto the light-emitting region of an OLED pixel. A second region E2 having a structure complementary to the first region E1 is coated or placed on the non-light-emitting region of the OLED panel. This makes it possible to achieve a configuration with particularly high light efficiency without reducing the resolution of the OLED.

[0083] This invention solves the problem that the described planar extended optical element clearly affects the direction of incident light propagation. This optical element is low-cost and can be used universally with various types of screens, especially without significantly reducing the screen's resolution. Furthermore, this optical element can achieve "top-hat" light distribution. At the same time, the optical element improves the effective light transmission efficiency compared to the prior art. By using this optical element in a screen, light diffusion can be effectively limited, the direction of light propagation can be more concentrated or focused, and a privacy effect can be achieved, depending on the embodiment.

[0084] The advantages of the present invention are numerous. The above effects are achieved by a single optical element, which does not necessarily need to have a special surface structure. Furthermore, it is preferable to achieve a "top-hat" distribution in the emitted light, enabling the realization of any desired high privacy contrast in theoretical simulations. When the optical element of the present invention is applied to the backlight of an LCD panel, high illumination density and good light recovery can be achieved. In addition, light propagation limitation in two planes (e.g., left / right and up / down simultaneously) can be achieved with only one optical element.

[0085] The present invention can be used in combination with a display device and is applicable when it is necessary to display and / or input confidential data, for example, PIN entry or data display in ATMs or payment terminals, password entry, or email viewing on mobile devices. The present invention can also be applied, for example, when a driver should not be able to see certain image content (e.g., entertainment programs) of passengers. Furthermore, the optical elements of the present invention can be used in other technologies and commercial applications. For example, they can be used for directing light used in dark-field illumination of microscopes, light shaping commonly used in illumination such as lights, and in measurement techniques. sign 10 Optical elements 20 Backlight 30 LCD panels A Light A1 area A2 area B light D Cover layer D1 Width of the first region D2 Width of the second region E1 1st area E2 2nd area S substrate

Claims

1. An optical element (10) that extends in a planar shape, The optical element (10) comprises 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), and the optical element is A plurality of first regions (E1) made of a transparent material having at least a first refractive index (N1); and It includes a plurality of second regions (E2) consisting of an opaque material having at least 50% of a second refractive index (N2) and at most 50% of a reflective material or white scattering material, Here, the plurality of first regions (E1) and the plurality of second regions (E2) are arranged alternately in one-dimensional or two-dimensional order on the surface of the optical element (10), the first refractive index (N1) is greater than the second refractive index (N2) over the entire wavelength range visible to the human eye, and in the plurality of second regions, the opaque material is mainly arranged in the direction of the larger second surface on the optical element (10). Here, when viewed 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, and at least a portion of the light irradiated onto the first large surface of the optical element (10) enters the optical element (10) through the light incident surface of the first region (E1), or is irradiated onto the second region (E2) which is reflected or white-scattered, and depending on the angle of incidence 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 or being perfectly reflected within the first region (E1) without obstruction, the light is recombined or recombined at the light emission surface in the first region (E1), b) The light is completely or partially refracted from the first region (E1) to the adjacent second region (E2), and there it is absorbed by the opaque material in the second region (E2), or reflected or scattered by the reflective material or white scattering material in the second region (E2), As a result, with respect to the light irradiated onto the first large surface of the optical element (10), the propagation direction of light away from the second large surface of the optical element (10) is restricted. Herein, the optical element (10) is characterized in that at least the other portion of the light incident on the first large surface of the optical element (10) and irradiated onto the second region (E2) is reflected or scattered.

2. The opaque material is made of a transparent material having the second refractive index (N2), The optical element (10) according to claim 1, characterized in that absorbent particles are mixed into the transparent material to produce an opacity effect.

3. The opaque material consists of lacquer or polymer. The opaque material includes graphite particles with a particle size of less than 500 nm as absorbent particles, black carbon nanoparticles with a particle size of less than 200 nm, Fe(II,III)O particles, and MnFe. ２ O ４ The optical element (10) according to claim 1 or 2, characterized in that it is doped with particles, dyes, or a mixture of dyes.

4. The aforementioned reflective material or white scattering material is made of a transparent material. The optical element (10) according to any one of claims 1 to 3, characterized in that the transparent material is doped with reflective particles and / or white scattering particles, and the transparent material exhibits an overall reflective effect or white scattering effect.

5. The optical element 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 (N2) is less than 0.

2.

6. The optical element (10) according to any one of claims 1 to 5, characterized in that when viewed in parallel projection perpendicular to the optical element (10), the first region (E1) and the second region (E2) are alternately arranged in a stripe pattern on the surface of the optical element (10).

7. The optical element according to any one of claims 1 to 5, characterized in that, when viewed in parallel projection perpendicular to the optical element (10), the first region (E1) is distributed on the surface of the optical element (10) in a point-like, circular, elliptical, rectangular, or hexagonal pattern, and the second region (E2) is complementary to the shape of the first region (E1).

8. A method for manufacturing an optical element (10), The optical element (10) includes a plurality of first regions (E1) and a plurality of second regions (E2), the plurality of first regions (E1) and the plurality of second regions (E2) are arranged alternately on the surface of the optical element (10) in a one-dimensional or two-dimensional order, and the manufacturing method is A step of forming a plurality of first regions (E1) on a substrate (S) using a transparent material having a first refractive index (N1), wherein there is a gap between any two adjacent first regions (E1); The step of partially filling the gap with an opaque material having a second refractive index (N2) such that the gap is filled to at least 50% of its height to partially form the plurality of second regions (E2); A method for manufacturing an optical element (10) according to any one of claims 1 to 7, comprising the step of further filling the gap using a diffuse reflective material or a specular reflective material to completely form the plurality of second regions (E2).

9. The method for manufacturing an optical element (10) according to claim 8, further comprising the step of sealing the plurality of first regions and the plurality of second regions by applying lacquer or coating to the side of the plurality of first regions and the plurality of second regions that is facing away from the substrate (S) as a final step.

10. A light-emitting device for transmitting light through a screen, Backlight (20), and The optical element (10) is included in any one of claims 1 to 8, Herein, the light-emitting device is characterized in that the propagation direction of the light emitted by the light-emitting device is restricted by the optical effect of the optical element (10).

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