Indication device

Abstract

To provide a display device with which it is possible to suppress losses of emitted light of a micro LED or a micro-organic EL element and improve utilization efficiency.SOLUTION: A display device 1 comprises: an element substrate 10 on which a plurality of light sources are arranged; a protective layer 20 that is provided on the element substrate and covers the light sources; a color filter 30 that is provided on the protective layer and has a plurality of color filters arranged in correspondence to the light sources; a lens array that is provided on the color filter and has a plurality of micro-lenses 41 that are arranged in correspondence to the color filter; and a planarizing layer 50 that is provided on the lens array and covers the micro-lenses, and that has a lower refractive index than the micro-lenses. The refractive index nm of the micro-lenses, the refractive index nt of the planarizing layer, and r / H, which is the ratio of curvature radius r and height H, of the lens surface of the micro-lenses satisfy prescribed formulas.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a display device. [Background technology]

[0002] In so-called microdisplays that use micro LEDs, micro organic EL elements, etc. as light sources, there is a demand for improving the efficiency of emitted light utilization and increasing efficiency in order to increase brightness and reduce power consumption.

[0003] In this regard, Patent Document 1 describes that light utilization efficiency is improved by arranging a hemispherical microlens on a light emitting element. Furthermore, Patent Document 2 describes that the viewing angle characteristics are improved by providing a light-transmitting layer on the microlenses. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2021-136208 [Patent Document 2] Japanese Patent Application Publication No. 2020-184481 Summary of the Invention [Problem to be solved by the invention]

[0005] As a light source, micro LEDs and micro OLED elements do not have a very high directivity of emitted light, so the light enters the microlens at various angles. Light that enters the interface between the transparent layer and the microlens at an angle greater than the critical angle is totally reflected, and therefore cannot be extracted as an effective emitted light component, resulting in a decrease in brightness.

[0006] The inventors have extensively studied the relationship between the form of the microlenses and the light-transmitting layer, and have completed the present invention based on the findings they have obtained.

[0007] An object of the present invention is to provide a display device that can reduce loss of light emitted from a micro LED or a micro organic EL element and improve utilization efficiency. [Means for solving the problem]

[0008] The present invention is a display device comprising an element substrate on which a plurality of light sources are arranged, a protective layer provided on the element substrate and covering the light sources, a color filter provided on the protective layer and having a plurality of color filters arranged corresponding to the light sources, a lens array provided on the color filter and having a plurality of microlenses arranged corresponding to the color filters, and a planarization layer provided on the lens array, covering the microlenses and having a refractive index lower than that of the microlenses. In this display device, the refractive index n of the microlens m , the refractive index of the planarization layer n t and r / H, which is the ratio of the radius of curvature r of the lens surface of the microlens to the height H, satisfies the following formula 1. 0.3<(n m -n t )-0.1(r / H) 2 +0.2(r / H)<0.6…(1) [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a display device that can reduce loss of light emitted from a micro LED or a micro organic EL element and improve utilization efficiency. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic cross-sectional view showing a part of a display device according to one embodiment of the present invention. [Figure 2] FIG. 2 is a diagram showing the positional relationship between the organic EL elements, color filters, and microlenses in a plan view of the display device. [Figure 3] FIG. 10 is a diagram showing the results of a ray tracing simulation for one shape of microlens. [Figure 4]FIG. 10 is a diagram showing the results of a ray tracing simulation for one shape of microlens. [Figure 5] FIG. 10 is a diagram showing the results of a ray tracing simulation for one shape of microlens. DETAILED DESCRIPTION OF THE INVENTION

[0011] An embodiment of the present invention will now be described with reference to Figures 1 to 5. A display device 1 according to this embodiment uses an organic EL element as a light source and has a configuration in which a large number of pixels are arranged when viewed from the front.

[0012] 1 shows a schematic cross-sectional view of one pixel of the display device 1. The display device 1 includes an element substrate 10 on which an organic EL element (light source) 11 is arranged, and a protective layer 20, a color filter 30, a lens array, and a planarization layer 50 formed on the element substrate 10. A light-transmitting substrate 70 is bonded onto the planarizing layer 50 by an adhesive layer 60, and a user can view an image displayed on the display device 1 from the light-transmitting substrate 70 side.

[0013] The organic EL elements 11 have a known configuration including a pixel electrode, a common electrode, and a functional layer, are connected to wiring (not shown) provided on the element substrate 10, and are each driven to emit light independently. The protective layer 20 is transparent and protects the organic EL element 11, and also flattens the surface to facilitate placement of the color filter 30. The protective layer 20 may be composed of multiple layers and may have gas barrier properties. A partition wall that separates the sub-pixels may be formed in the protective layer 20. By forming the partition wall, stray light to adjacent sub-pixels can be suppressed.

[0014] The color filter 30 is provided on each organic EL element 11. The color filter 30 has a plurality of color filters that transmit light in any of the wavelength bands of red (R), green (G), and blue (B), which are the three primary colors of light. The number of color filters and the colors that they transmit can be determined depending on the display characteristics of the display device, and may include yellow, etc.

[0015] The lens array is formed on the color filter 30 and has a plurality of microlenses 41 aligned in correspondence with the color filters. The microlenses 41 according to this embodiment are so-called plano-convex lenses, and have a refractive index higher than at least the refractive index of air and the planarizing layer 50 .

[0016] FIG. 2 shows the positional relationship between the organic EL element 11, the color filter 30, and the microlens 41 in a plan view of the area shown in FIG. A pixel of the display device 1 is composed of three sub-pixels 101, 102, and 103 corresponding to red (R), green (G), and blue (B), respectively. Each of the sub-pixels 101, 102, and 103 is provided with a red filter 30R, a green filter 30G, and a blue filter 30B, which respectively constitute a color filter. Each sub-pixel is provided with one organic EL element 11 and three microlenses 41. The above is just one example, and the planar shape of the sub-pixel, the number of organic EL elements 11 and microlenses 41 to be arranged, and the like can be determined depending on the display characteristics and the like.

[0017] The planarization layer 50 absorbs and flattens the irregularities of the microlenses 41, making it easier to bond the light-transmitting substrate 70. For this reason, the maximum thickness of the planarization layer 50 is set to be equal to or greater than the height of the microlenses 41.

[0018] The planarization layer 50 has a refractive index lower than that of at least the microlenses 41. The closer the refractive index of the planarization layer 50 is to the refractive index of air, the greater the difference in refractive index between the planarization layer 50 and the microlenses 41 can be.

[0019] In one example, the planarization layer 50 contains a hollow filler and a medium. The hollow filler and the medium are transparent in visible wavelengths, for example, having a total light transmittance of 90% or more for light of visible wavelengths. The hollow filler contributes to lowering the refractive index of the planarization layer 50. The medium is present between the hollow filler particles, bonding the hollow fillers together and stabilizing the planarization layer 50.

[0020] A suitable hollow filler material is silicon dioxide (silica, SiO2). Hollow fillers made of silica are inexpensive and have high transparency and physical stability in visible wavelengths. When hollow fillers are located in the low refractive index layer, air regions are scattered within the planarization layer 50, resulting in a lower refractive index of the planarization layer 50. As the hollow filler content increases, the refractive index approaches that of air.

[0021] In the display device 1, light emitted from the driven organic EL element 11 passes through the protective layer 20 and the color filter 30, enters the microlens 41, and then passes through the planarization layer 50, the adhesive layer 60, and the light-transmitting substrate 70 to be extracted to the outside.

[0022] In the above process, light is also refracted at the interface between the upper surface (lens surface) of the microlens 41 and the planarization layer 50. This refraction varies depending on the shape of the lens surface and the refractive index of the microlens 41 and the planarization layer 50, so the inventors used ray tracing simulations to study how to optimize this to extract light efficiently.

[0023] The model used in the simulation is shown below. (fixed parameters) Microlens shape: Hemispherical Pitch between pixels (gaps): 2.8 μm Planarization layer thickness: 1.2 μm Distance DH between the organic EL element and the microlens: 2.6 μm (variable parameters) Microlens shape shape 1 Height H: 1.1 μm, radius of curvature r of lens surface: 1.4 μm (r / H 1.27) shape 2 Height H: 0.8 μm, radius of curvature r of lens surface: 1.6 μm (r / H 2.0) shape 3 Height H: 0.6 μm, radius of curvature r of lens surface: 1.9 μm (r / H 3.17) Microlens refractive index: 1.3 to 1.8 in 0.1 increments Refractive index of the planarization layer: 1.1 to 1.5 in 0.1 increments, and no planarization layer (an adhesive layer 60 (refractive index 1.7) is present on the lens array) Under the above conditions, the refractive index of the microlens was changed in increments of 0.1, and the brightness in the front direction of the pixel was calculated. Furthermore, for each of microlens shapes 1 to 3, the improvement or decrease in brightness was calculated based on the brightness under the condition of "microlens refractive index 1.6, no planarization layer."

[0024] The simulation results for shapes 1 to 3 are shown in Figs. 3 to 5, respectively. In all shapes, there was a tendency for brightness to improve relative to the reference value by making the refractive index of the planarization layer lower than the refractive index of the microlenses. However, unexpected findings were obtained, such as the fact that the brightness improvement effect is reduced if the refractive index of the planarization layer is too low or the refractive index of the microlenses is too high, and that the optimal range for the difference in refractive index between the two varies depending on the shape.

[0025] Specifically, we found that the refractive index difference at which the brightness improvement effect is maximized tends to increase as the height of the microlens decreases and the radius of curvature of the lens surface increases, i.e., as the value of r / H increases. In this study, the optimal refractive index difference for shape 1 was 0.3, while the optimal refractive index differences for shapes 2 and 3 were 0.4 and 0.5, respectively, varying in parallel with the value of r / H. We also found that for all shapes, a generally favorable brightness improvement effect can be achieved as long as the refractive index difference is within a range of ±0.1 of the optimal refractive index difference.

[0026] In a display device, the dimensions of each part of the microlens vary depending on the pixel dimensions, etc., so the inventors attempted to generalize the conditions under which a good brightness improvement effect can be obtained based on the above findings, and as a result, they found that a good brightness improvement effect can be obtained when the following inequality 1 is satisfied. 0.3<(n m -n t )-0.1(r / H) 2 +0.2(r / H)<0.6…(1) In addition, in formula 1, n m is the refractive index of the microlens, n t and denote the refractive index of the planarization layer, respectively.

[0027] In this study, for Shape 1, where r / H is in the range of 1 or more and less than 2, the preferred range of the refractive index difference was 0.2 or more and 0.5 or less, more preferably 0.2 or more and 0.4 or less. For Shape 2, where r / H is in the range of 2 or more and less than 3, the preferred range of the refractive index difference was 0.3 or more and 0.6 or less, more preferably 0.3 or more and 0.5 or less. For Shape 3, where r / H is in the range of 3 or more, the preferred range of the refractive index difference was 0.3 or more, preferably 0.6 or more and 0.8 or less. These conditions for each shape all satisfy the above formula 1.

[0028] In the display device 1 according to this embodiment, based on the above findings, the refractive indexes of the microlenses and the planarizing layer, and the shape of the microlenses are set to satisfy the above formula 1, thereby reducing the loss of emitted light and improving utilization efficiency even when using a light source that is not highly directional, such as the organic EL element 11. As a result, light generated from the organic EL element 11 can be efficiently guided to the front of the device regardless of the pixel dimensions, etc., and display quality such as brightness can be significantly improved.

[0029] Although one embodiment of the present invention has been described in detail above, the present invention is not limited to a specific embodiment and includes configuration changes and combinations within the scope of the gist of the present invention. Some examples of changes are shown below, but these are not all inclusive and other changes are also possible. Two or more of these changes may be combined as appropriate.

[0030] In the display device according to the present invention, the light source is not limited to the organic EL element described above, and other light source elements such as micro LEDs can also be used.

[0031] The planar shape of the microlenses is not limited to the circular shape shown in the above embodiment. For example, adjacent microlenses may be provided over the entire sub-pixel by etching back or other processes, resulting in a rectangular or other planar shape similar to that of the sub-pixel. [Explanation of symbols]

[0032] 10 Element substrate 11 Organic EL element (light source) 20 protective layer 30 Color Filters 30R Red Filter (Color Filter) 30G Green Filter (Color Filter) 30B Blue filter (color filter) 41 Microlens 50 Planarization layer 60 Adhesive layer 70 Translucent substrate

Claims

1. an element substrate on which a plurality of light sources are arranged; a protective layer provided on the element substrate and covering the light source; a color filter provided on the protective layer and having a plurality of color filters arranged corresponding to the light sources; a lens array provided on the color filter and having a plurality of microlenses arranged corresponding to the color filters; a planarization layer disposed on the lens array, covering the microlenses, the planarization layer having a refractive index lower than that of the microlenses; Equipped with The refractive index n of the microlens ｍ , the refractive index n of the planarization layer ｔ and r / H, which is the ratio of the radius of curvature r of the lens surface of the microlens to the height H, satisfies the following formula 1: Display device. 0.3<(n ｍ -n ｔ )-0.1(r / H) ２ +0.2(r / H)<0.6…(1)

2. the r / H is 1 or more and less than 2, The n ｍ and the n ｔ The difference is 0.2 or more and 0.5 or less. The display device according to claim 1 .

3. the r / H is 2 or more and less than 3, The n ｍ and the n ｔ The difference is 0.3 or more and 0.6 or less. The display device according to claim 1 .

4. the r / H is 3 or more, The n ｍ and the n ｔ The difference is 0.6 or more and 0.8 or less. The display device according to claim 1 .

5. an element substrate on which a plurality of light sources are arranged; a protective layer provided on the element substrate and covering the light source; a color filter provided on the protective layer and having a plurality of color filters arranged corresponding to the light sources; a lens array provided on the color filter and having a plurality of microlenses arranged corresponding to the color filters; a planarization layer disposed on the lens array, covering the microlenses, the planarization layer having a refractive index lower than that of the microlenses; Equipped with the ratio r / H of the radius of curvature r of the lens surface of the microlens to the height H is 3 or more; The refractive index n of the microlens ｍ and the refractive index n of the planarization layer ｔ The difference between Display device.

6. The light source is an organic EL element or a micro LED. The display device according to claim 1 .

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