Light redirecting film, polarizing plate and display containing the polarizing plate

Abstract

The present invention discloses a light redirecting film, a polarizing plate having the light redirecting film, and a display including the polarizing plate. The light redirecting film includes a light redistribution layer and a light guiding layer, wherein the light guiding layer is disposed on the light redistribution layer. The light redistribution layer of the light redirecting film includes a plurality of strip microprisms extending along a first direction and arranged at intervals, and a plurality of diffraction gratings disposed at the interval bottoms of adjacent strip microprisms, wherein each strip microprism has at least one side as a light guiding inclined surface, each interval bottom has at least one set of diffraction gratings, and the light guiding layer is connected to the strip microprisms and the plurality of diffraction gratings. When the light redirecting film is disposed on the display side of the display, the light loss problem at the display side at viewing angle can be improved, and the brightness distribution at different viewing angles can be made more uniform.

Description

Technical Field

[0001] The invention relates to a light redirecting film, a polarizing plate having the light redirecting film, and a display including the polarizing plate. The light redirecting film can equalize the brightness difference of the display at each viewing angle to avoid the problem of excessive viewing angle dependence. Background Art

[0002] As displays are developing towards larger sizes, especially for large TVs or spliced ​​display walls, even if users are viewing these displays at a straight angle, the contrast and brightness of the edge images of large-size displays are still inconsistent with the central image, not to mention that when users are viewing at a side angle, the color deviation and saturation reduction caused by the overall side brightness deficiency will be more serious. Although today's displays, whether passively emitting liquid crystal displays (LCDs), or actively emitting organic light-emitting diode displays (OLED displays), small-pitch LED displays, sub-millimeter light-emitting diode displays (mini LED displays), micron light-emitting diode displays (micro LED displays, the same below) and other electroluminescent displays, have excellent contrast characteristics at all viewing angles, allowing users to view displayed images at all viewing angles. The so-called contrast value is actually the ratio of the bright image to the dark black screen. For the contrast value of the display at the side viewing angle, such as in the liquid crystal display, it often has a certain contrast value because the light at the side viewing angle has been greatly attenuated and the light leakage in the dark state has become extremely low. For another example, in the electroluminescent display, because it does not emit light in the dark state, the contrast value is also higher, but it does not represent the uniformity and image quality of the bright image that the user can actually feel. Therefore, now users are not only satisfied with the minimum requirement that the displayed image can be viewed at the side viewing angle but the actual image brightness is weak, but they expect the displayed image to have consistent and uniform image light and image quality at all viewing angles. In addition, current displays, whether passive or active, generally use electroluminescent bodies as image light sources, such as liquid crystal displays using light-emitting diode (LED) backlights, or self-luminous organic light-emitting diode displays. Because electroluminescent bodies are point light sources with extremely high single-point brightness, good light guidance is required to form a uniform overall display screen without flickering. Please refer to Figure 1A , Figure 1ATaking a general liquid crystal display as an example, the distribution diagram of bright light at a horizontal viewing angle. It can be clearly seen from the diagram that the intensity of light emitted by the liquid crystal display decreases significantly as the viewing angle increases. This is because the liquid crystal display is a non-active light-emitting display and the pixel light transmittance of the display panel is low. In order to increase the backlight intensity and efficiency, a brightness enhancement film, a focusing prism sheet and other structures must often be used in the light-emitting diode backlight module for brightness enhancement. However, these methods can often only increase the peak brightness of the front view, and when the light emitted by the backlight source passes through the display panel, it is limited by the aperture ratio of the pixels and will further attenuate as the viewing angle increases. In addition, for an electroluminescent display that uses its own light-emitting body directly as a display pixel, due to the lack of optical structure films in the backlight module such as a diffuser and a light guide plate on the display side, it is also easy to cause light loss and uneven light distribution when viewed from a larger side viewing angle, and it is difficult to form an ideal surface light source with similar brightness at each viewing angle. Therefore, the image viewed from the side cannot have the better image quality as the one viewed from the front, and it is particularly easy to have low contrast or abnormal color performance due to insufficient brightness due to light loss.

[0003] In addition, by Figure 1A The spectrum also shows the distribution characteristics of the brightness of conventional general displays. Its intensity is higher in the positive viewing angle range (for example, within ±30° viewing angle), and its intensity is greatly reduced in the side viewing angle range (for example, outside ±30° viewing angle). This does not conform to the ideal normal distribution of brightness, and the brightness has a large tangent slope change with the viewing angle spectrum. In the conventional technology, the half-width (FWHM) of the spectrum curve is increased by strengthening the front-view incident intensity of the backlight source, but the overall distribution characteristics of the display brightness cannot be changed. Therefore, the conventional half-width (FWHM) method of observing whether the brightness distribution at each viewing angle is uniform and wide is not representative.

[0004] Please refer to Figure 1B , Figure 1B The evaluation method is to use a method that can actually reflect the brightness of the front viewing angle and the side viewing angle. For example, more than 75% of the maximum brightness of the display at the vertical viewing angle represents the front viewing angle range, and more than 40% of the maximum brightness represents the side viewing angle range. When the front viewing angle range is not excessively reduced or limited, the side viewing angle range can be extended and increased, so that the tangent slope of the brightness to the viewing angle spectrum changes smaller and slower, thereby presenting a more ideal normal distribution curve. The brightness of the display is better uniform at each viewing angle, and the human eye can feel a more uniform brightness when viewing.

[0005] Among the conventional methods for improving the image quality of a display at a side viewing angle, for example, Taiwan Patent TWI645218 discloses using a light redirecting film with a double-layer grating surface to improve the color washout or gray-scale inversion phenomenon of a liquid crystal display at a wide viewing angle. However, actual tests have shown that although the light redirecting film has the effect of improving the color washout and gray-scale inversion phenomenon, the double-layer grating structure has a greater reduction in light brightness. In actual measurements, the grating structure still has relatively high zero-order diffraction and first-order diffraction intensities due to the diffraction effect. Although enhanced interference has a better light deflection efficiency than refraction or scattering, the angle it affects is still within the range of the normal viewing angle, and the gain in improving the side viewing brightness is limited. For another example, Taiwan Patent TWI731590 discloses a liquid crystal display including a color improvement film having a stripe-shaped micro-prism layer to improve the color shift and saturation reduction problems of side-viewing. However, without excessive refraction of the micro-prisms to reduce the display resolution, the light guide angle of the stripe-shaped micro-prism layer alone is still insufficient, so it still cannot solve the problems of light loss and uneven light distribution at side viewing angles. Summary of the invention

[0006] In order to solve the above problems, the present invention provides a light redirecting film applied to the light-emitting side of the display, which can improve the brightness performance of the display in the side viewing range, without excessively sacrificing brightness in the near-front viewing range to reduce the front viewing range. Without affecting the original front viewing brightness of the display, the display light brightness distribution pattern can be changed, the side viewing range can be extended, and the image light quality and uniformity viewed from all angles can be improved.

[0007] In order to achieve the above-mentioned purpose, the present invention proposes a light redirecting film, which includes a light redistribution layer and a light guiding layer. The light redistribution layer has a plurality of strip-shaped microprisms extending along a first direction and arranged at intervals, and a plurality of diffraction gratings arranged at the bottom of the intervals between adjacent strip-shaped microprisms, wherein each strip-shaped microprism has at least one side that is a light guiding inclined surface, and each interval bottom has at least one group of diffraction gratings; the light guiding layer is arranged on the light redistribution layer and connected to the strip-shaped microprisms and the diffraction gratings.

[0008] In one embodiment of the light redirecting film of the present invention, the light redistribution layer has a first refractive index n1, the light guiding layer has a second refractive index n2, the first refractive index n1 and the second refractive index n2 are between 1.4 and 1.7, and the difference between n1 and n2 is not less than 0.05.

[0009] In another embodiment of the light redirecting film of the present invention, the maximum width of the bottom of each stripe-shaped microprism of the light redistribution layer is between 3 μm and 15 μm.

[0010] In another embodiment of the light redirecting film of the present invention, the height of each stripe-shaped microprism of the light redistribution layer is between 5 μm and 15 μm.

[0011] In another embodiment of the light redirecting film of the present invention, the width of the bottom intervals between adjacent stripe-shaped microprisms of the light redistribution layer is between 3 μm and 15 μm.

[0012] In another embodiment of the light redirecting film of the present invention, the tops of the stripe-shaped microprisms of the light redistribution layer are flat, pointed or curved.

[0013] In another embodiment of the light redirecting film of the present invention, each light guiding slope of the strip microprisms of the light redistribution layer forms an angle θ with the normal direction of the light redirecting film surface in a cross section perpendicular to the first direction, and the angle θ is not less than 5° and not more than 15°.

[0014] In another embodiment of the light redirecting film of the present invention, the period of the diffraction grating disposed at the bottom of the interval between adjacent strip-shaped micro-prisms is between 0.5 μm and 3.0 μm.

[0015] In another embodiment of the light redirecting film of the present invention, the height of each diffraction grating disposed at the bottom of the interval between adjacent strip-shaped micro-prisms is between 0.4 μm and 1.0 μm.

[0016] In another embodiment of the light redirecting film of the present invention, the light redirecting film further includes a functional layer, which is formed on the surface of the light guiding layer of the light redirecting film, wherein the functional layer can be selected from one of the groups consisting of a hard coating layer, an anti-reflection layer and an anti-glare layer, or a combination thereof.

[0017] In addition, the present invention also proposes a polarizing plate, which includes a polarizing layer with an absorption axis and the aforementioned light redirecting film, wherein the light redirecting film is arranged on one side of the polarizing layer, and the light redirecting film can be arranged on the light output side or the light input side of the polarizing layer, wherein the light redirecting film includes a light redistribution layer and a light guiding layer, and the first direction in which the strip microprisms of the light redistribution layer extend intersects with the absorption axis of the polarizing layer at an angle between 90°±25°.

[0018] In addition, the present invention also proposes a display, which includes a display panel and the above-mentioned polarizing plate and uses the polarizing plate as a display side polarizing plate, wherein the viewing angle extension ratio of the display at a normalized maximum brightness of 75% is >1.0, and the viewing angle extension ratio at a maximum brightness of 40% is >1.3.

[0019] In another embodiment of the present invention, the absolute value of the maximum tangent slope of the spectrum of the maximum brightness after normalization of the display brightness as a function of viewing angle is less than 4.0x10 -2 .

[0020] The above invention content is intended to provide a simplified summary of the content of this patent so that readers can have a basic understanding of the content of this patent. This invention content is not a complete overview of the content of this patent, and its intention is not to point out the important / key elements of the embodiments of the present invention or to define the scope of the present invention. After referring to the following implementation methods, those with ordinary knowledge in the technical field to which the present invention belongs can easily understand the basic spirit of the present invention and the technical means and implementation forms adopted by the present invention.

[0021] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments, but is not intended to limit the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1A , Figure 1B The diagram shown is a schematic diagram of bright light distribution of a liquid crystal display at a horizontal viewing angle.

[0023] Figure 2A Depicted is a perspective view of a light redirecting film according to an embodiment of the present invention.

[0024] Figure 2B Depicted is a cross-sectional view of a light redirecting film disclosed according to an embodiment of the present invention.

[0025] Figure 3 FIG. 4 is a schematic diagram of the light guiding effect of a conventional color improvement film having only a strip-shaped micro-prism layer.

[0026] Figure 4 Schematic diagram of the light guiding effect of the light redirecting film according to an embodiment of the present invention

[0027] Figure 5 FIG. 1 is a schematic diagram of a light redirecting film according to another embodiment of the present invention.

[0028] Figure 6 FIG. 1 is a schematic diagram of a polarizing plate disclosed according to another embodiment of the present invention.

[0029] Figure 7 FIG. 1 is a schematic diagram of a display according to another embodiment of the present invention.

[0030] Figure 8 The diagram depicts a normalized spectrum showing the variation of the maximum brightness with viewing angle. DETAILED DESCRIPTION

[0031] In order to make the description of the content of the present invention more detailed and complete, the following is an illustrative description of the implementation and specific embodiments of the present invention; however, this is not the only form of implementing or using the specific embodiments of the present invention. The embodiments disclosed below can be combined or replaced with each other under beneficial circumstances, and other embodiments can be added to one embodiment without further recording or explanation.

[0032] In the following description, many specific details will be described in detail to enable the reader to fully understand the following embodiments. However, embodiments of the present invention can be practiced without these specific details. In other cases, well-known structures and devices are only schematically depicted in the figures to simplify the drawings.

[0033] First, refer to Figure 2A as well as Figure 2B , Figure 2A The figure shows a perspective view of a light redirecting film according to an embodiment of the present invention. Figure 2B The cross-sectional view of the light redirecting film according to one embodiment of the present invention is shown along the cross section perpendicular to the Y axis. The light redirecting film 10 of the present invention comprises a light redistribution layer 20 and a light guide layer 30. The light redistribution layer 20 has a plurality of strip microprisms 21 extending along a first direction D1 and arranged at intervals, and a plurality of diffraction gratings 22 arranged at the bottom of the intervals between adjacent strip microprisms 21, wherein each strip microprism 21 has at least one side as a light guiding inclined surface 21a, and each interval bottom has at least one set of diffraction gratings 22; the light guide layer 30 is arranged on the light redistribution layer 20 and connected to the strip microprisms 21 and the diffraction gratings 22. In actual operation, the first direction D1 can be the length direction or the width direction of the light redirecting film 10.

[0034] In a preferred embodiment of the light redirecting film of the present invention, the maximum bottom width W1 of the strip microprisms 21 is between 3 μm and 15 μm, the height H1 is between 5 μm and 15 μm, and the bottom spacing width W2 of adjacent strip microprisms 21 is between 3 μm and 15 μm. In the embodiment of the light redirecting film of the present invention, the height H1 of the strip microprisms 21 is sufficient to allow the light deflected by the diffraction grating 22 to pass obliquely, and the maximum bottom width W1 of the strip microprisms 21 and the bottom spacing width W2 of adjacent strip microprisms 21 can be adjusted according to the lateral light source intensity required by the display in actual application to guide the light in a proportion.

[0035] The light redirecting film 10 of the present invention is formed of a light redistribution layer 20 and a light guiding layer 30 with a curable resin having different refractive indices. In the interface between the light redistribution layer 20 and the light guiding layer 30, a diffraction grating 22 has a strong diffraction effect and performs a first light splitting on the incoming light. The light splitting effect of the diffraction grating 22 is related to the grating period, height, etc., and does not change significantly due to the light path first passing through a high refractive index resin layer and then a low refractive index resin layer, or first passing through a low refractive index resin layer and then a high refractive index resin layer, but there must be a refractive index difference between the two. Therefore, the first refractive index n1 of the light redistribution layer can be selected to be greater than or less than the second refractive index n2 of the light guiding layer. In one embodiment of the present invention, the first refractive index n1 and the second refractive index n2 are between 1.4 and 1.7, and the difference between the first refractive index n1 and the second refractive index n2 is not less than 0.05 and not more than 0.3.

[0036] See also Figure 3 , Figure 3 Schematic diagram of the light guiding effect of the conventional color improvement film 40 having only a strip microprism layer 41. The conventional color improvement film 40 deflects the light L incident on the strip microprism layer 41 by means of the refractive index difference between the strip microprism layer 41 and the filling layer 42 and the light guiding inclined surfaces 411a of the plurality of strip microprisms 411 to improve the color deviation problem of the side view. However, since the light L is deflected only when passing through the light guiding inclined surfaces 411a when it is incident from the front, under the trend of the display to be thinner, the only way is to increase the angle θ between the light guiding inclined surfaces 411a and the normal line of the film surface to change the proportion of light that can pass through the light guiding inclined surfaces 411a; or to increase the refractive index difference between the strip microprism layer 41 and the filling layer 42 to increase the degree of light deflection after the incident light. However, it is difficult to obtain special optical materials with extremely high or low refractive index. Therefore, it is impossible to significantly guide light to the side viewing angle to improve the brightness distribution difference between the side viewing angle range and the front viewing angle range.

[0037] Figure 4Schematic diagram of the light guiding effect of the light redirecting film 10 of the present invention. In one embodiment, the light redistribution layer 20 of the light redirecting film 10 is disposed on the light incident side of the light L, and the light guiding layer 30 is on the light exiting side. In addition to comprising a plurality of strip-shaped microprisms 21, the light redistribution layer 20 also includes a plurality of diffraction gratings 22 disposed at the bottom of the intervals between adjacent strip-shaped microprisms 21. Under the premise of not increasing the overall thickness of the light redirecting film 10, the diffraction gratings 22 can allow the incident light L to not only directly pass through the light-guiding bevels 21a, but also allow the light L that originally passed through the flat portion of the bottom of the interval without being deflected to be diffracted and deflected first, and then obliquely enter the light-guiding bevels 21a in the light-guiding layer 30, so as to increase the light-guiding path without increasing the overall thickness of the light redirecting film 10, and then pass through the adjacent light-guiding bevels 21a and the diffraction gratings 22 for multiple refraction, diffraction or reflection to a larger angle, so that the light intensity naturally decreases with the number of deflections at the lateral viewing angle, thereby reducing the brightness distribution difference between the lateral viewing angle range and the front viewing angle range, and achieving a stronger lateral light guiding and homogenizing effect.

[0038] In another embodiment of the present invention, the top of the strip microprism 21 of the light redirecting film 10 is not limited to a plane, a sharp angle or an arc, so as not to cause the bright state image of the display to produce a flickering feeling. In a preferred embodiment of the present invention, the top of the strip microprism 21 of the light redirecting film 10 is a plane.

[0039] In another embodiment of the present invention, each light guiding inclined surface 21a of the strip microprism 21 of the light redirecting film 10 forms an angle θ with the normal direction of the film surface of the light redirecting film 10 in a cross section perpendicular to the first direction D1, and the angle θ is preferably not less than 5° and not greater than 15°. By designing that the angle θ is not less than 5°, the light guiding inclined surface 31a can provide a sufficient light guiding incident surface to receive the light after passing through the diffraction gratings 22; by designing that the angle θ is not greater than 15°, a basically linear light guiding effect can be achieved.

[0040] In another embodiment of the present invention, the strip microprisms 21 of the light redirecting film 10 can be independently set to have the bottom maximum width W1, height H1, bottom spacing width W2 and angle θ to be completely or partially the same, depending on the pixel arrangement, pixel size, overall requirements or product design requirements of different display panels. Therefore, adjacent light-guiding inclined surfaces 21a in the light redirecting film 10 can be symmetrical or asymmetrical.

[0041] In another embodiment of the present invention, the period P of the diffraction grating 22 of the light redirecting film 10 is preferably between 0.5 μm and 3.0 μm. The height H2 of each diffraction grating 22 is between 0.4 μm and 1.0 μm. When the period P of the diffraction gratings 22 is smaller than the width of the strip microprism 21, and the height H2 of the diffraction gratings 22 is smaller than the height of the strip microprism 21, the diffraction gratings 22 can produce relatively more diffraction effects without affecting the image resolution. Moreover, the size of the diffraction gratings 22 is not less than the wavelength of visible light, so that the sub-wavelength effect will not be generated, thereby not affecting the reflection and penetration of visible light at the interface of the diffraction grating 22, and will not cause unexpected design variables due to the discontinuity of the diffraction effect.

[0042] See also Figure 5 In another embodiment of the light redirecting film of the present invention, the light redirecting film 11 further includes a functional layer 50, and the functional layer 50 is formed on the surface of the light guiding layer 30 of the light redirecting film 11 (that is, the functional layer 50 is formed on the surface of the light emitting side of the light redirecting film 11, or the light emitting surface), wherein the functional layer 50 can be selected from one of a hard coating layer, an anti-reflection layer, and an anti-glare layer or any combination thereof according to the actual needs of the display. In a preferred embodiment of the present invention, the functional layer 50 is a substrate used in the second curable resin molding process of the light guiding layer 30, and other surface treatment functions are appropriately added to the surface as required. In another embodiment of the present invention, the functional layer 50 can be a protective layer on the outer side of the light redirecting film 11.

[0043] See also Figure 6 In another embodiment of the present invention, an integrated polarizing plate 60 is disclosed. The integrated polarizing plate 60 includes a polarizing layer 70 having an absorption axis 70a and the above-mentioned light redirecting film 10, and the light redirecting film 10 is disposed on one side of the polarizing layer 70. In actual operation, the light redirecting film 10 can be disposed on the light emitting side or the light incident side of the polarizing layer 70. In a preferred embodiment, the light redirecting film 10 of the present invention is disposed on the light emitting side of the polarizing layer 70, wherein the first direction D1 (Y-axis direction) of the extension of the strip microprisms 21 and the diffraction grating 22 of the light redistribution layer 20 intersects with the absorption axis 70a of the polarizing layer 70 at an angle, and the angle is between 90°±25°, so as to enhance the brightness of the horizontal side viewing angle and the brightness equalization effect of each horizontal viewing angle. In a preferred embodiment, the light redirecting film 10 of the present invention is disposed on the light-emitting side of the polarizing layer 70. In an embodiment of the integrated polarizing plate of the present invention, the polarizing layer 70 can also be used as a substrate when the light redistribution layer 20 is formed by molding the first curable resin, and the light redirecting film 10 can be used as a protective layer for the polarizing layer 70.

[0044] See also Figure 7Another embodiment of the present invention discloses a display 100, which includes a display panel 80 and an integrated polarizer 60 of the above-mentioned embodiment, wherein the integrated polarizer 60 serves as a display side polarizer. The viewing angle extension ratio of the display 100 at the normalized maximum brightness of 75% is >1.0, and the viewing angle extension ratio at the maximum brightness of 40% is >1.3. In this article, the maximum brightness 75% positive viewing angle range (VW75) refers to the viewing angle range covered by the maximum brightness of the vertical viewing angle of the display 100 after brightness normalization, which is 75% or more. The maximum brightness 40% side viewing angle range (VW40) refers to the side viewing angle range covered by the maximum brightness of the vertical viewing angle of 40% or more. The original 75% positive viewing angle range and the original 40% side viewing angle range of a conventional display that does not include a light redirecting film 10 are represented by VW75, respectively. origin With VW40 origin The viewing angle extension ratio is the original viewing angle ratio of the display 100 of the present invention with the light redirecting film 10 relative to the conventional display without the light redirecting film 10. In the display 100 of the present invention, when the image light of the display panel 80 is perpendicularly incident on the light redirecting film 10, the light is efficiently transmitted laterally to extend the front viewing angle and the side viewing angle range, that is, the viewing angle extension ratio of 75% of the front viewing angle range is greater than 1.0 (VW75 / VW75 origin >1.0), and the viewing angle extension ratio of 40% of the side viewing angle range is greater than 1.3 (VW40 / VW40 origin >1.3) without compromising or limiting the brightness at normal viewing angles.

[0045] The light redirecting film disclosed in the present invention can be used in a variety of display panels without being limited by the light-emitting mechanism of the panel. The display panel can improve the light distribution of the bright image of the display by using the light redirecting film, especially for display panels with large differences in the maximum brightness L255 gradation between the front viewing angle and the side viewing angle or with a faster brightness decay changing with the viewing angle.

[0046] In another embodiment of the present invention, the absolute value of the maximum tangent slope of the spectrum of the normalized maximum brightness of the display 100 as a function of viewing angle is less than 4.0x10 -2 When the absolute value of the tangent slope is small, it means that the brightness changes more gently with the viewing angle and is not easily detected by the human eye and affects the visual experience.

[0047] The manufacturing method and formation order of the strip microprisms 21 and the diffraction gratings 22 of the light redirecting film 10 of the present invention are not limited. In one embodiment of the present invention, a first curable resin (not shown) having a first refractive index n1 can be firstly embossed by a mold, an engraving roller, etc. to form a plurality of strip microprisms 21 and a plurality of diffraction gratings 22 extending in the same direction, and after being cured to form the light redistribution layer 20, a second curable resin (not shown) having a second refractive index n2 is filled on the surface of the light redistribution layer 20 and flattened to form the light guiding layer 30. In another embodiment of the present invention, a second curable resin (not shown) with a second refractive index n2 used as the light guide layer 30 may be firstly embossed by a reverse structure mold, an engraving roller, etc., to form the strip microprisms 21 and a plurality of diffraction gratings 22 extending in the same direction and corresponding to each other in the reverse direction, and then a first curable resin (not shown) with a first refractive index n1 is filled in the embossed surface of the light guide layer 30 and flattened to form the light redistribution layer 20 after curing. The interface where the light redistribution layer 20 contacts the light guide layer 30 may have the microstructure of the strip microprisms 21 and the diffraction gratings 22. The first curable resin and the second curable resin may be light curable resins or heat curable resins, such as acrylic resins, silicone resins, polyurethane resins, epoxy resins or combinations thereof.

[0048] The method for manufacturing the stripe-shaped microprisms 21 and the diffraction gratings 22 of the light redirecting film 10 of the present invention can also be to coat a first curable resin having a first refractive index n1 on a substrate, and then emboss by a mold, an engraving roller, etc. to form a plurality of stripe-shaped microprisms 21 and a plurality of diffraction gratings 22 extending in the same direction. After curing to form the light redistribution layer 20, a second curable resin having a second refractive index n2 is then coated and the surface of the light redistribution layer 20 is flattened to form the light guide layer 30. In another embodiment of the present invention, a second curable resin having a second refractive index n2 used as the light guide layer 30 can also be coated on a substrate by a mold, an engraving roller, etc. having an inverse structure, and then embossed to form the stripe-shaped microprisms 21 and a plurality of diffraction gratings 22 extending in the same direction in the opposite direction. After curing, a first curable resin having a first refractive index n1 (not shown) is then filled on the embossed surface of the light guide layer 30 and flattened to form the light redistribution layer 20. After the light redistribution layer 20 and the light guiding layer 30 are fabricated, the substrate may be retained or removed. In the embodiment where a substrate is used to fabricate the light redirecting film, the substrate may be a transparent substrate commonly used in the art, such as polyethylene terephthalate film (PET), triacetyl cellulose film (TAC), polymethyl methacrylate film (PMMA), etc.

[0049] The following examples are used to further illustrate the present invention, but the present invention is not limited thereto.

[0050] Example

[0051] Example 1, Example 2 and Example 3

[0052] Examples 1 to 3 disclose different light redirecting films, wherein the size, material refractive index and light guiding bevel angle of the strip microprisms and diffraction gratings of the light redistribution layer of the light redirecting films of each embodiment are listed in Table 1. The light redirecting films of each embodiment are attached to the same polarizing layer by the light redistribution layer side in an externally attached manner, and the influence of the air layer interface is eliminated to form an integrated polarizing plate, wherein the first direction in which the strip microprisms of the light redistribution layer extend and the angle between the absorption axis of the polarizing layer are both 105°.

[0053] Comparative Example

[0054] Comparative Example 1

[0055] Comparative Example 1 uses only the same polarizing layer as used in Examples 1 to 3 but does not stack any polarizing plates with light-guiding structures such as strip microprisms or diffraction gratings.

[0056] Comparative Examples 2 and 3

[0057] Comparative Examples 2 and 3 also use the same external attachment method and the same angle with the absorption axis of the polarizing layer as in the first embodiment. Figure 3 The color improvement film with stripe-shaped microprisms is laminated on the polarizing layer of the same embodiment. The size, refractive index and light guiding slope angle of the stripe-shaped microprisms of the color improvement films of Comparative Examples 2 and 3 are shown in Table 1.

[0058] Comparative Example 4

[0059] In Comparative Example 4, the optical film having a diffraction grating structure is laminated on the polarizing layer which is the same as that in Example 1 by using the same external lamination method as that in Example 1.

[0060] Table 1

[0061]

[0062] The integrated polarizing plates prepared in the above-mentioned Examples 1 to 3 and Comparative Examples 2 to 4 and the polarizing plate of Comparative Example 1 were attached to a liquid crystal display panel (brand model: AUO, VP229DA) by an adhesive layer, and the maximum brightness of the bright state L255 gradation in the absorption axis direction of the polarizing layer was measured by a panel measuring instrument AutronicMelchers GmbH Mechanics, ConoScope 80, and the normalized spectrum is shown in Figure 8 The test results are shown in Table 2.

[0063] Table 2

[0064]

[0065]

[0066] It can be clearly seen from the test results in Table 2 that Comparative Examples 2 and 3 use integrated polarizing plates with only strip microprism optical films, and Comparative Example 4 uses integrated polarizing plates with only diffraction grating optical films. Compared with Comparative Example 1 using a polarizing plate without any light-guiding structure, it is difficult to simultaneously achieve the effect of increasing the angle range of the side viewing angle and reducing the maximum slope of the brightness curve on the liquid crystal display. In particular, in Comparative Example 3 with only a strip microprism structure, even if the height of the strip microprism has been greatly increased to increase the ability of its light-guiding slope to receive lateral light, its side viewing angle coverage above 40% of brightness still has its limit, which can only reach 78°. Although the maximum slope of the curve of brightness changing with viewing angle can also be reduced, the positive viewing angle coverage above 75% of brightness has been slightly reduced, and it is difficult to expect that the side light-guiding effect can be improved by repeatedly increasing the thickness of the structure. For Comparative Example 4 with only a diffraction grating structure, although it does not affect the positive viewing angle range, the effect of diffracting light to the side viewing angle is also not good. From the measured values ​​in Table 2 and Figure 8 From the spectrum of maximum brightness changing with viewing angle, the comparative example 1 without any light guide structure film is used as a control, and its maximum brightness of 40% represents the original 40% side viewing angle range (VW40 origin ) and maximum brightness 75% represents the original 75% positive viewing angle range (VW75 origin ), Examples 1 to 3 can all effectively extend the viewing angle, especially in the side viewing angle coverage range (VW40) above the maximum brightness of 40%, the efficiency is extremely good, and the 40% viewing angle extension ratio is VW40 / VW40 origin All are above 1.3. For the positive viewing angle range (VW75) with a maximum brightness of 75% or more, the 75% viewing angle extension ratio is VW75 / VW75. origin It is still greater than 1.0 and better than the original viewing angle, without limiting the original front viewing angle range. It only reduces the peak value of the maximum brightness L255 tone at the vertical viewing angle and effectively distributes the light evenly to the side viewing angle. Therefore, the maximum tangent slope of the spectrum of brightness changes with the viewing angle can be maintained at a low level of less than 4.0x10 -2 , making the bright-state spectrum of the display close to the ideal normal distribution curve.

[0067] Of course, the present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, technicians familiar with the field may make various corresponding changes and deformations based on the present invention, but these corresponding changes and deformations should all fall within the scope of protection of the claims attached to the present invention.

Claims

1. A light redirecting film, characterized in that include: A light redistribution layer having a plurality of strip-shaped micro-prisms extending along a first direction and arranged at intervals, and a plurality of diffraction gratings disposed at the bottom of the intervals between adjacent strip-shaped micro-prisms, wherein each strip-shaped micro-prism has at least one side as a light guiding inclined surface, and each interval bottom has at least one set of diffraction gratings; and A light guide layer is disposed on the light redistribution layer and connected to the plurality of strip-shaped micro-prisms and the plurality of diffraction gratings; The light redistribution layer has a first refractive index n1, the light guiding layer has a second refractive index n2, the first refractive index n1 and the second refractive index n2 are between 1.4 and 1.7, and the difference between the first refractive index n1 and the second refractive index n2 is not less than 0.

05.

2. The light redirecting film according to claim 1, wherein: The maximum width of the bottom of each stripe-shaped microprism of the light redistribution layer is between 3 μm and 15 μm.

3. The light redirecting film according to claim 1, wherein: The height of each stripe-shaped microprism of the light redistribution layer is between 5 μm and 15 μm.

4. The light redirecting film according to claim 1, wherein: The width of the bottom intervals between adjacent strip-shaped microprisms of the light redistribution layer is between 3 μm and 15 μm.

5. The light redirecting film according to claim 1, wherein: The tops of the plurality of strip-shaped micro-prisms of the light redistribution layer are flat, pointed or arc-shaped.

6. The light redirecting film according to claim 1, wherein: Each light guiding inclined surface of the plurality of strip-shaped microprisms of the light redistribution layer forms an angle θ with the normal direction of the light redirecting film surface in a cross section perpendicular to the first direction, and the angle θ is not less than 5° and not more than 15°.

7. The light redirecting film according to claim 1, wherein: The periods of the plurality of diffraction gratings of the light redistribution layer are between 0.5 μm and 3.0 μm.

8. The light redirecting film according to claim 1, wherein: The height of each diffraction grating of the light redistribution layer is between 0.4 μm and 1.0 μm.

9. The light redirecting film according to claim 1, wherein: The light redirecting film comprises a functional layer formed on the surface of the light emitting side of the light redirecting film, wherein the functional layer is selected from one of the groups consisting of a hard coating layer, an anti-reflection layer and an anti-glare layer or any combination thereof.

10. A polarizing plate, comprising a polarizing layer having an absorption axis and a light redirecting film as described in any one of claims 1 to 9, wherein the light redirecting film is arranged on one side of the polarizing layer, and the first direction in which the multiple strip-shaped microprisms of the light redistribution layer extend intersects with the absorption axis of the polarizing layer at an angle, and the angle is between 90°±25°.

11. A display comprising a display panel and the polarizing plate as claimed in claim 10, wherein the viewing angle extension ratio of the display at a maximum brightness of 75% after normalization of brightness is greater than 1.0, and the viewing angle extension ratio at a maximum brightness of 40% is greater than 1.

3.

12. The display according to claim 11, wherein the absolute value of the maximum tangent slope of the normalized maximum brightness variation with viewing angle spectrum is less than 4.0x10 -2 .

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