Method for producing a display device, and display device

Abstract

The present application relates to a method for producing a display device, and to a corresponding display device. A photosensitive layer is provided on a display having a plurality of self-luminous image elements. The image elements are controlled to expose the photosensitive layer so as to form a gradient-index microlens arrangement.

Description

[0001] Method for manufacturing a display device and display device

[0002] Technical field

[0003] The invention relates to a method for manufacturing a display device and a corresponding display device.

[0004] background

[0005] Display devices are devices or systems that present information in a visually perceptible form. Light field displays are an example of display devices.

[0006] Light fields describe the intensity and direction of light rays at any point in three-dimensional space. These light fields are crucial for a realistic representation of objects, as they describe how light is reflected from different surfaces. Imitating the real light field of objects enables a natural depth perception that corresponds to the perception of the human eye.

[0007] Light field displays utilize technologies to reproduce light rays in different directions and with varying intensity. These displays often employ microlens arrays mounted on self-illuminating image elements (pixels). The microlenses project light intensity and color information onto the viewer according to a viewing angle. This reconstructs the natural light field of the displayed objects, resulting in continuous and natural depth perception without the need for special glasses or aids. This makes light field displays a particularly user-friendly solution for displaying complex visual content.

[0008] The light intensity and color information of the image elements are typically determined using parallax images (also called parallax-related images). Parallax images are image data captured from multiple perspectives to capture the parallax effect and thus create the perception of depth. They allow the reconstruction of three-dimensional scenes by extracting pixels with identical coordinates from each of the parallax images and arranging them around the pixels of a display with similar coordinates. This is illustrated in Figure 4. For example, if three parallax images are extracted vertically and horizontally from a three-dimensional scene, and each of these images has a resolution of 500x500 pixels, a display with a resolution of 1500x1500 pixels can be used, and the pixels of the parallax images with the coordinates can be used.

[0009] 1,1 1,1 1,1

[0010] 1,1 1,1 1,1

[0011] 1,1 1,1 1,1 can be placed in the upper left corner of the 1500x1500 pixel display and form a group of pixels that can constitute a picture element of the display:

[0012] 1.1 1.2 1.3

[0013] 2.1 2.2 2.3

[0014] 3.1 3.2 3.3

[0015] This pixel swapping can continue until the entire display area is covered with pixels from appropriately grouped parallax images. Each group of pixels arranged in this way can form a picture element of the display. A layer of microlenses applied to the picture elements transmits the light intensity and color information to the different viewing angles, thus reconstructing the natural light field that would emanate from a depicted three-dimensional object.

[0016] The microlenses arranged in a grid must be aligned so that each lens completely covers a specific number of image elements, for example, the group of nine pixels in the 1500x1500 pixel display shown in Figure 4. If the microlens grid is subsequently applied to a display device, alignment errors can occur, such as misalignment between the microlens and the image element. Misalignments of the microlens grid lead to errors in the projected light field, which become particularly visible when multiple screens are combined to create a large light field display.

[0017] To illustrate the problem, Figure 5 shows two examples of microlens arrangements 40 on a display 20 consisting of individual self-illuminating image elements. The display 20 can, for example, be an LED or OLED display comprising a multitude of self-illuminating image elements, which can be RGB pixels.

[0018] In a display device 100 of Figure 5, the microlenses 41 are applied to the display 20 such that they completely enclose a number of image elements. The microlenses 41 are flush with the image elements located at the edge of the microlenses. As an example, the transition between microlens 41a and microlens 41b in area 21 is shown, which is aligned with the transition between two image elements.

[0019] A display device 200 shows a misalignment of the microlens arrangement 40. The microlenses 42 are mounted on the display 20 such that they are offset relative to the image elements. As an example, the transition between microlens 42a and microlens 42b in area 22, which lies centrally to an image element, is shown. Such a displacement causes artifacts in a light field generated based on the image elements.

[0020] Precisely aligning a retrofitted microlens array onto an existing display device is complex. Therefore, the challenge lies in providing a method that simplifies the alignment of a microlens grid on a display, thereby reducing image artifacts in light field displays, for example.

[0021] Summary

[0022] The problem is solved by a method for manufacturing a display device according to claim 1 and a display device according to claim 14.

[0023] The method comprises providing a display with a plurality of self-illuminating image elements, providing a photosensitive layer, which may be a photopolymer layer, on the display, and controlling the image elements of the display to expose the photosensitive layer in order to form a desired gradient-index microlens array in the photosensitive layer.

[0024] Photopolymers are light-sensitive materials composed of monomers that can undergo chemical structural changes upon irradiation with light, usually under the influence of photoinitiators, typically through polymerization and / or curing. The photoinitiators contained in the photopolymers can initiate polymerization, in which monomers are linked to form polymers, potentially resulting in changes such as a change in the refractive index.

[0025] Unlike conventional lenses, where light refraction is achieved through the lens's geometric shape, gradient-index microlenses (GRIN microlenses, also known as gradient refractive index (micro)lenses or gradient (micro)lenses) are characterized by the fact that light refraction is achieved by varying the refractive index within the lens material. This variation in the refractive index can be achieved by exposing the photosensitive layer. For the purposes of this application, a photosensitive layer is defined as a layer whose refractive index can be locally modified by irradiation with light. The photosensitive layer can consist of photopolymers, which can be exposed via the display's image elements. The display's image elements can be individually controlled to generate different light intensities.In this way, polymerization of the photopolymers in the photosensitive layer can be initiated in a controlled manner, resulting in a controlled change in the refractive index of the material and the formation of gradient-index microlenses. By forming the gradient-index microlens arrays directly on the intended display, it is possible to ensure that the gradient-index microlens array precisely matches the image elements, so that each gradient-index microlens always covers a specific number of specific image elements, thus ensuring correct alignment throughout the process.

[0026] The process can further include fixing the photosensitive layer after exposure to stabilize the gradient-index microlens array created in the material. The fixing process can, for example, involve further exposure, thermal treatment (also known as temperature curing), or a combination of further exposure and thermal treatment.

[0027] Fixing by further exposure to light within a specific wavelength range is also known as bleaching. This process allows any remaining reactive photopolymers or other molecules to be completely polymerized and stabilizes the optical properties of the material. Furthermore, the photosensitive layer, into which the gradient-index microlens array may be embedded, can be fully cured by fixing. The specified wavelength range for fixing by further exposure can be any wavelength range that does not alter the optical properties of the gradient-index microlenses upon further exposure. The specified wavelength range depends on the photoinitiators used within the photopolymers and can encompass wavelengths across the entire electromagnetic spectrum.

[0028] Depending on the material system chosen, fixation can also be achieved through thermal treatment, for example, with heat or infrared radiation. Generally, thermal treatment involves adjusting the temperature to values ​​specific to the photosensitive material used, such as photopolymer, and fixing it in place. One advantage of thermal fixation is that it allows for better control of the reactivity differences between the materials in the photosensitive layer.

[0029] Furthermore, the process may include the application of a protective layer, which may be designed to protect the display from the effects of fixing. Fixing by exposure may, for example, involve UV radiation, which can damage the materials of the image elements, thus impairing brightness and color accuracy. Fixing by exposure may also, for example, utilize infrared radiation, which can generate heat that can affect the electronics of the display device. Fixing by thermal treatment may, for example, involve heat treatment, which can also affect the electronics of the display device.

[0030] The protective layer can be provided as a separate layer between the display and the photosensitive layer and can be designed, for example, to reflect, absorb, and / or thermally insulate light within a specified wavelength range. In another embodiment, additives are incorporated into the photosensitive layer that reflect, absorb, and / or have thermally insulating properties. In this embodiment, the protective layer would be integrated into the photosensitive layer.

[0031] The photosensitive layer can be protected against moisture penetration by appropriate measures, as damage to plastics caused by ultraviolet light, for example, can be accelerated by exposure to moisture. This can be achieved, for instance, by sealing or coating. The photosensitive layer can consist of a photosensitive material that may have a first component and a second component, where the first component may exhibit a higher refractive index change upon exposure and / or a higher rate of refractive index change upon exposure. By composing the photosensitive material from several components with different refractive indices and / or rates of change and / or other properties, the properties of the photosensitive material can be varied.Furthermore, this allows for a finer adjustment of the final refractive index in the gradient-index microlenses.

[0032] The first and second components can be monomers. A material system can consist of an acrylate mixture or a hybrid system with epoxy, epoxy hardener, silicon-containing and sulfur-containing monomers (also oligomers, polymers), and ethylene double bonds. The material system can include, for example, the following materials:

[0033] UV epoxy

[0034] - Acrylate

[0035] SH-EN (material consisting of thiols and alkenes) UV epoxy mixtures Epoxy Silanes Silicones

[0036] SH-EN materials are light-curing systems consisting of thiols and alkenes. Thiols can be monomers with a suitable refractive index and are therefore suitable for the process.

[0037] Depending on the choice of material system for the first and second components, different conditions may be required for polymerization and / or fixation. Fixation, and thus the curing of the photosensitive layer, can, for example, take place in air. However, it is also possible that material systems do not react in the presence of oxygen and / or air. In this case, it may be necessary to carry out the fixation in the absence of oxygen and / or air. This can be done, for example, under vacuum and / or a protective gas, such as nitrogen. Another possibility is to use a coating over the photosensitive layer. The refractive index of the first and / or second component can be in the range of 1.3 to 1.6; preferably, the refractive index of the first and / or second component is in the range of 1.4 to 1.55.Preferably, the refractive index of the first component and the refractive index of the second component should differ by 0.2 or more.

[0038] The refractive index change of the first component upon exposure can be greater than 0.01, preferably greater than 0.02. The refractive index change of the second component upon exposure can be less than 0.01, preferably less than 0.002.

[0039] The reaction rate of the first component can be greater than the reaction rate of the second component when exposed to light.

[0040] Differences in refractive indices, refractive index changes, and / or reaction rates allow for a large difference in refractive index and thus a suitable refractive index gradient within the gradient-index microlenses for projecting a light field. Furthermore, imaging errors, such as those caused by spherical and / or chromatic aberration, can be minimized.

[0041] It should be noted that, in addition to the components of a material system mentioned here, other types of photopolymers can also be used without limiting the scope of application of the previously described method for producing gradient-index microlenses.

[0042] Furthermore, a display device is provided which includes a display with a plurality of self-illuminating image elements and a photosensitive layer provided on the display into which a gradient-index microlens arrangement is exposed.

[0043] The display device can be manufactured using the above methods and in particular may include a protective layer as described above, which protects the display from fixing, in particular from a predetermined wavelength range and / or thermal treatment for fixing.

[0044] Brief description of the drawings

[0045] Figure 1 shows a flowchart illustrating a method according to an exemplary embodiment. Figure 2 illustrates process steps of a method for fabricating a gradient-index microlens array on a display device using a photosensitive layer.

[0046] Figure 3 schematically shows an example of a change in refractive index as a function of wavelength.

[0047] Figure 4 illustrates the reconstruction of three-dimensional scenes based on parallax images.

[0048] Figure 5 shows orientations of a conventional microlens arrangement on a display device.

[0049] Detailed description

[0050] The following section describes embodiments of the invention in detail with reference to the accompanying drawings. It is understood that the following description of embodiments is not to be understood in a limiting sense. The scope of the invention is not intended to be limited by the embodiments described below or by the drawings, which serve only for illustration.

[0051] The drawings are to be considered schematic representations, and the objects depicted in the drawings are not necessarily shown to scale. Rather, the various elements are represented in such a way that their function and general purpose are recognizable to a knowledgeable person.

[0052] Figure 1 shows a flowchart illustrating a process for fabricating a gradient-index microlens array according to one embodiment. Figure 2 illustrates the process steps shown in Figure 1.

[0053] Step 10 provides a display with self-illuminating pixels. Step 11 provides a photosensitive layer on the display. Figure 2 shows an embodiment of the display device according to steps 10 and 11 at S1. The display device comprises a display 20 and a photosensitive layer 30. The display 20 can, for example, be an LED or OLED display comprising a plurality of self-illuminating pixels, which can be RGB pixels. The photosensitive layer 30 can be a photopolymer layer, wherein the photopolymer in the photosensitive layer 30a can be photosensitive to the wavelengths of the light emitted by the display 20 in the unexposed state.

[0054] The light emitted by the pixels of the display 20 can, for example, encompass wavelengths in the range of 450 nm to 750 nm, which corresponds to a typical wavelength range of RGB pixels. In other embodiments, the pixels of the display 20 can also emit light in a different wavelength range. The photopolymers in the photosensitive layer 30a in the unexposed state can be designed to be photosensitive to the entire wavelength range of the pixels. Alternatively, the photopolymers can be designed to exhibit selective photosensitivity, limited to specific sub-ranges of the wavelength spectrum. The photosensitivity of the photopolymers can be achieved, for example, by a specific material composition of a photosensitive material.It is also possible that a first component of the photosensitive material, for example a first photopolymer, has a different photosensitivity than a second component of the photosensitive material, for example a second photopolymer.

[0055] At stage 12, the self-illuminating pixels of the display are controlled in such a way that the photosensitive layer is exposed. Exposure of the photosensitive layer results in the formation of a gradient-index microlens array.

[0056] Figure 2 further shows an embodiment S2 of the exposure of the photosensitive layer 30 on the display 20. The pixels of the display 20 can be controlled to generate different colors and light intensities. Area 20a shows a gradual exposure of the pixels, for example with increasing light intensities. The progression of the light intensity is illustrated by arrows, for example arrows A2a and A2b, with the arrows pointing in the direction of increasing light intensity. A maximum light intensity can be reached, for example, in the middle of area 20a.

[0057] An exposure time can be expected for typical LED displays with luminance levels of 400-500 cd / m². 2 or irradiance levels of 0.5 mJ / cm² 2 or 50-100 mJ / cm² 2 approximately 100 seconds.

[0058] Exposure of the display elements 20 causes local polymerization of the photopolymers located above the activated image elements. This allows the polymerization to be initiated in a controlled manner at predefined positions. The polymerization of the photopolymers causes a change in the refractive index An, whereby the local change in the refractive index An of the photopolymers depends on the respective dye and light intensity as well as on the position of the activated image elements of the display 20. In this way, a variation in the change in the refractive index An, and thus a variation in the refractive index n, can occur in the photosensitive layer 30.

[0059] In embodiment S2 of Figure 2, a gradual change in the refractive index An in the exposed photosensitive layer 30b is shown, with the change in refractive index An being illustrated by arrows, for example, arrows A1a and A1b. The arrows point in the direction of increasing change in refractive index An. Accordingly, for example, in region 31a, the change in refractive index An increases from a minimum value at the edge to the center of the region and reaches a maximum value in the center. As explained above, the change in refractive index An correlates with the change in light intensity of the image elements.

[0060] Exposure can cause a positive change in the refractive index An of the photopolymers, with higher light intensity resulting in a larger positive change in the refractive index An. Accordingly, the areas with a larger change in the refractive index An in the photosensitive layer 30b can be areas with a higher refractive index n, compared to the areas with a smaller change in the refractive index An, which can have a lower refractive index n.

[0061] The areas of the exposed photosensitive layer 30b with a larger refractive index change An are located, as explained above, above the pixels of the display 20 that are exposed with a higher light intensity. The areas of the exposed photosensitive layer 30b with a smaller refractive index change An are located, as explained above, above the pixels of the display 20 that are exposed with a lower light intensity. In the areas of the photosensitive layer 30 that lie above unactivated pixels and are therefore not exposed, there is essentially no refractive index change An. These areas can have the lowest refractive index. This results in a gradual progression of the refractive index n in the photosensitive layer 30.In another embodiment, the photopolymers can be configured such that exposure causes a negative refractive index change in the photopolymers, with higher light intensity resulting in a greater negative refractive index change An. Accordingly, the areas with a greater refractive index change An in the photosensitive layer can be areas with a lower refractive index n, compared to the areas with a smaller refractive index change An, which can have a higher refractive index n. In this case of a negative refractive index change, the display's image elements must be driven in a manner that may differ from the driving behavior for a positive refractive index change in order to generate the desired gradient-index microlens array.In general, attention must therefore be paid to how the change in refractive index at the photopolymer within the photosensitive layer correlates with the staining and light intensity of the image elements.

[0062] The light field display with gradient-index microlens arrangement formed in 12 is illustrated in Figure 2 using an embodiment S3. A gradient-index microlens arrangement 30c was formed by controlled polymerization of the photosensitive layer 30, which is aligned with the image elements of the display 20.

[0063] The gradient of the refractive index n within the gradient-index microlens array 30c is illustrated by arrows, for example, arrows A3a and A3b. Arrows A3a and A3b point in the direction of increasing refractive index change An, which can correspond to an increasing refractive index n. At the edges of the gradient-index microlenses, such as gradient-index microlens 31b, the refractive index change An can be minimal. These regions of minimal refractive index change, which can exhibit a minimal refractive index, essentially form over uncontrolled image elements and can form the boundary of the gradient-index microlenses. In the center of the gradient-index microlenses, such as gradient-index microlens 31b, the refractive index change An can be maximal, and the refractive index n can have a maximum value.The alignment of the gradient index microlens arrays thus results automatically from the process and requires no further subsequent alignment.

[0064] Following the previously described process, the photosensitive layer 30 can be fixed. Fixing can, for example, include further exposure to light of a predetermined wavelength range, thermal treatment (temperature curing), or a combination of further exposure and thermal treatment of the photosensitive layer 30, into which a gradient-index microlens arrangement 30c has been exposed, which can result in complete polymerization of the photopolymers, the embodiment of which depends on the material system of the photosensitive layer 30.

[0065] For fixing by further exposure, the specified wavelength range depends on the material system of the photosensitive layer and can be any wavelength range that does not change the optical properties of the gradient-index microlenses upon further exposure.

[0066] For example, a possible specified wavelength range could be less than 400 nm or greater than 780 nm. It is also possible for the specified wavelength range to encompass wavelengths between 400 nm and 780 nm. In general, it is possible for the specified wavelength range to include wavelengths across the entire electromagnetic spectrum.

[0067] For fixing by thermal treatment, the choice of temperature for curing the photosensitive layer depends on the material system of the photosensitive layer, whereby generally all temperatures are conceivable.

[0068] To protect the display 20 from the specified wavelength range and / or the thermal treatment for fixing the photosensitive layer 30, a protective layer can be provided. The protective layer can, for example, be arranged between the display 20 and the photosensitive layer 30. For instance, the protective layer can be designed to reflect or absorb waves of the specified wavelength range and / or to provide thermal insulation. It would also be conceivable to incorporate additives into the photosensitive layer 30 that reflect or absorb light and / or have heat-insulating properties. In this embodiment, the protective layer would be integrated into the photosensitive layer 30.

[0069] Figure 3 schematically shows an example of a refractive index change An of a possible photosensitive material of the photosensitive layer 30 as a function of wavelength. The photosensitive material can be a two-component system and comprise a first component, monomer 1 with refractive index ni, and a second component, monomer 2 with refractive index n2. The monomers can be photosensitive to the emitted wavelengths of the image elements of the display device and can exhibit the largest possible difference in refractive index such that m » n2. The middle graph corresponds to the refractive index of a mixture of the monomers n.

[0070] Exposure of the photopolymers can cause a change in the refractive index An. A positive change in refractive index An > 0 can occur, and the change in refractive index of monomer 1 Am can be greater than the change in refractive index of monomer 2 Am, such that Am » Am.

[0071] The rate of change in the refractive index of the first component n can be higher than the rate of change in the refractive index of the second component r2, such that n » r2. With simultaneous exposure, the refractive index of the first component changes faster than the refractive index of the second component, resulting in a large difference in refractive index.

[0072] The refractive index of the first component m and / or the second component m can be in the range of 1.3 to 1.6; preferably, the refractive index of the first component m and / or the second component m is in the range of 1.4 to 1.55. Preferably, the refractive index of the first component and the refractive index of the second component should differ by 0.2 or more.

[0073] The refractive index change of the first component Am can be greater than 0.01 upon exposure, preferably greater than 0.02. The refractive index change of the second component Am can be smaller, for example less than 0.01, preferably less than 0.002.

[0074] This can result, for example, in a refractive index change of the An monomer mixture from 0.01 to 0.1. This allows for the creation of a suitable refractive index gradient in the gradient-index microlenses for projecting a light field. Furthermore, imaging errors, such as those caused by spherical and / or chromatic aberration, can be minimized.

[0075] The refractive index change of the first component Am can be greater than the

[0076] The refractive index change of the second component Am should preferably be at least 1.5 times, at least 2 times, at least 5 times, or at least 10 times as large. For example, if the refractive index change of the second component An2 is less than 0.002, the refractive index change of the first component A is preferably at least 0.01. For example, if the refractive index change of the second component Am is less than 0.005, the refractive index change of the first component Am is preferably at least 0.02. For example, if the refractive index change of the second component Am is less than 0.01, the refractive index change of the first component Am is preferably at least 0.1.

[0077] The reaction rate of the first component upon exposure can be greater than the reaction rate of the second component. For example, the reaction rate of the first component can be at least 1.5 times or at least 2 times greater than the reaction rate of the second component upon exposure. In another embodiment, the reaction rate of the first component upon exposure can be at least 4 times greater than the reaction rate of the second component upon exposure. In a further embodiment, the reaction rate of the first component upon exposure can be 6 times greater than the reaction rate of the second component upon exposure.

[0078] The photosensitive material can consist, for example, of an acrylate mixture or a hybrid system with epoxy, epoxy hardener, silicon-containing and sulfur-containing monomers (also oligomers, polymers) and ethylene double bonds, and may include the following materials:

[0079] UV epoxy

[0080] - Acrylate

[0081] SH-EN (material consisting of thiols and alkenes) UV epoxy mixtures Epoxy Silanes Silicones

[0082] Depending on the choice of material system for the first and second components, different conditions may be required for polymerization and / or fixation. Fixation, and thus the curing of the photosensitive layer, can, for example, take place in air. However, it is also possible that material systems will not react and / or polymerize in the presence of oxygen and / or air. In this case, it may be necessary to perform fixation in the absence of oxygen and / or air. This can be done, for example, under vacuum and / or a protective gas, such as nitrogen. Another option is to cover the photosensitive layer.

Claims

Patent claims 1. Method for manufacturing a display device, comprising: Providing a display (20) with a large number of self-illuminating image elements, Providing a photosensitive layer (30) on the display (20), and Controlling the image elements of the display (20) to expose the photosensitive layer (30) in order to form a gradient index microlens arrangement (30c) in the photosensitive layer (30).

2. The method according to claim 1, further comprising fixing the photosensitive layer (30) after exposure.

3. Method according to claim 2, wherein the fixing comprises further exposure to light of a predetermined wavelength range.

4. Method according to claim 2 or 3, wherein the fixing comprises a thermal treatment.

5. The method of claim 3, wherein the method comprises providing a protective layer which protects the display (20) from light of the specified wavelength range.

6. The method of claim 4, wherein the method comprises providing a protective layer which protects the display (20) from thermal treatment.

7. Method according to claim 5 or 6, wherein the protective layer is provided between the display (20) and the photosensitive layer (30).

8. Method according to claim 5 or 6, wherein the protective layer is integrated into the photosensitive layer (30).

9. Method according to any one of claims 1 to 8, wherein the photosensitive material comprises a first component and a second component, wherein the first component exhibits a higher refractive index change upon exposure.

10. Method according to any one of claims 1 to 9, wherein the photosensitive material comprises a first component and a second component, wherein the first component has a reaction rate at least 1.5 times higher upon exposure than the second component.

11. Method according to claim 9, wherein the refractive index change of the first component and / or the second component is in the range of 1.3 to 1.

6.

12. The method of claim 9 or 10, wherein the first component and / or the second component are selected from the group consisting of: - Acrylate epoxy Silane silicone Thiole - Alkenes 13. Method according to any one of claims 7 to 9, wherein the change in refractive index upon exposure is greater than 0.01 for the first component and less than 0.01 for the second component.

14. Display device comprising: a display (20) with a plurality of self-illuminating image elements, and a photosensitive layer (30) provided on the display (20) in which a gradient index microlens arrangement (30c) is exposed.

15. Display device according to claim 14, further comprising a protective layer which is configured to protect the display (20) from light in a predetermined wavelength range.

16. Display device according to claim 14, further comprising a protective layer which is configured to protect the display (20) from thermal treatment.

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