CN116360148A - Light redirecting film, polarizing plate and display comprising polarizing plate - Google Patents
Light redirecting film, polarizing plate and display comprising polarizing plate Download PDFInfo
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- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on liquid crystals, e.g. single liquid crystal display cells
- G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
- G02F1/1333—Constructional arrangements; Manufacturing methods
- G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
- G02F1/1336—Illuminating devices
- G02F1/133602—Direct backlight
- G02F1/133606—Direct backlight including a specially adapted diffusing, scattering or light controlling members
- G02F1/133607—Direct backlight including a specially adapted diffusing, scattering or light controlling members the light controlling member including light directing or refracting elements, e.g. prisms or lenses
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- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
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- G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on liquid crystals, e.g. single liquid crystal display cells
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Abstract
The invention discloses a light redirecting film, a polarizing plate with the light redirecting film and a display comprising the polarizing plate. The light redirecting film comprises a plurality of strip-shaped micro prisms extending along a first direction and arranged at intervals and a plurality of diffraction gratings arranged at the bottoms of the intervals of the adjacent strip-shaped micro prisms, wherein each strip-shaped micro prism is provided with at least one light guiding inclined plane at one side, each interval bottom is provided with at least one group of diffraction gratings, and the light guiding layer is connected with the strip-shaped micro prisms and the plurality of diffraction gratings. The light redirecting film can improve the side view angle light loss problem of the display when being arranged on the display side of the display, and ensures that the brightness distribution under different viewing angles is more uniform.
Description
Technical Field
The present 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 homogenize brightness differences among various viewing angles of the display and avoid the problem of excessive viewing angle dependence.
Background
With the trend of larger size of displays, especially for large-sized televisions or tiled display walls, even if the user views the displays at a front view angle, the edge frames of the large-sized displays can still find that the contrast, brightness and other performances of the edge frames are inconsistent with those of the central frames, and even though the user views at a side view angle, the situation of color deviation and saturation reduction caused by the main reason of insufficient overall lateral brightness is more serious. Although modern displays, whether passive light emitting Liquid Crystal Displays (LCDs) or organic light emitting diode displays (OLED displays) capable of active light emission, small-pitch light emitting diode displays (small-pitch LED display), sub-millimeter light emitting diode displays (mini LED displays), micro light emitting diode displays (micro LED display) (or micro light emitting diode displays, the same applies hereinafter), and the like, have excellent contrast characteristics at each viewing angle, so that users can view the display images at each viewing angle range. The contrast value is substantially the ratio of bright image to dark black image, and the contrast value of the display at the side view angle, such as in the liquid crystal display, is often very low due to the substantial degradation of the light at the side view angle, and the light leakage at the dark state is also very low. In an electroluminescent display, for example, the contrast ratio is high because the dark state does not emit light, but does not represent the uniformity and image quality of the bright image that the user can actually feel. Therefore, the user is not only satisfied with the minimum requirement that the displayed image can be viewed from the side view angle but the brightness of the actual image is weak, but the viewed displayed image is expected to have uniform image light and image quality at each view angle. In addition, current displays, whether passive light emitting or active light emitting displays, generally employ electroluminescence bodies as image light sources, such as liquid crystal displays employing Light Emitting Diode (LED) backlights, or self-luminous organic light emitting diode displays. Because the electroluminescent body belongs to a point light source with extremely high single-point brightness, good light guide is needed to form a uniform and flicker-free integral display picture. Referring to fig. 1A in conjunction, fig. 1A is a diagram illustrating a bright state light distribution diagram of a typical lcd at a horizontal viewing angle. The light intensity emitted by the lcd is greatly reduced with the increase of the viewing angle, because the lcd belongs to the non-active light emitting display and the pixel light transmittance of the display panel is low, and in order to increase the backlight intensity and efficiency, the led backlight module often has to be brightened by adopting a structure such as a brightness enhancement film and a light-gathering prism sheet, but these structures can only raise the peak value of the front-view brightness, and the light emitted by the backlight source is limited by the aperture ratio of the pixels and further attenuated with the increase of the viewing angle when passing through the display panel. In addition, in the electroluminescent display using the light-emitting body as the display pixel, the lack of the optical structure film in the backlight module such as the diffusion sheet and the light guide plate on the display side is easy to cause the problems of light loss and uneven light distribution when viewing at a larger side view angle, and the ideal surface light source with close brightness at each view angle is difficult to form. Therefore, the image viewed from the side cannot have the same quality as the image viewed from the front, and the image is particularly easy to have low contrast or abnormal color performance due to insufficient brightness caused by light loss.
In addition, the map of fig. 1A also shows that the conventional general display brightness distribution characteristics have high intensity in the front view angle range (for example, in the ±30° viewing angle), the intensity in the side view angle range (for example, outside the ±30° viewing angle) is greatly reduced, which does not conform to the ideal brightness normal distribution, and the brightness has a large tangential slope change to the viewing angle spectrum, and the conventional art increases the Full Width Half Maximum (FWHM) of the spectrum curve in a manner of enhancing the normal incidence intensity of the backlight, but the overall distribution characteristics of the display brightness cannot be changed, so that the conventional Full Width Half Maximum (FWHM) is not representative of whether the brightness distribution of each viewing angle is uniform and wide.
Referring to fig. 1B, fig. 1B shows that the brightness of the front view and the side view angle can be actually reflected as an evaluation mode, for example, more than 75% of the maximum brightness of the vertical view of the display is used to represent the front view angle range, and the maximum brightness is more than 40% to represent the side view angle range.
In a conventional way of improving the image quality of the side view angle of a display, for example, taiwan patent No. TWI645218 discloses a light redirecting film with a double-layer grating surface to improve the phenomenon of white color (color wash out) or gray scale inversion (gray-scale inversion) of the liquid crystal display at a wide viewing angle. However, through practical tests, the light redirecting film has the effect of improving the phenomena of frame whitening and gray scale inversion, but the double-layer grating structure has more damage to the brightness of light, while during practical measurement, the grating structure mainly uses zero-order diffraction and first-order diffraction intensities due to diffraction effects, although the enhanced interference has better refraction or scattering on the light deflection efficiency, the affected angle still falls within the range of a front view angle, and the gain range for improving the side view brightness is limited. For example, taiwan patent No. 731590 discloses a liquid crystal display, which includes a color improving film having a stripe-shaped microprism layer to improve the problems of side view color bias and saturation reduction, however, the problem of side view light loss and uneven light distribution cannot be solved by only relying on the insufficient light guiding angle of the stripe-shaped microprism layer without causing the display resolution to be reduced due to excessive refraction of the microprism.
Disclosure of Invention
In order to solve the above-mentioned problems, the present invention provides a light redirecting film applied to the light-emitting side of a display, which can improve the brightness performance of the display in the side view angle range, and can not excessively sacrifice the brightness in the near front view range to reduce the front view angle range. The light brightness distribution pattern of the display can be changed without affecting the original front-looking brightness of the display, the side-looking angle range can be extended, and the quality and uniformity of the image light viewed at each angle can be improved.
In order to achieve the above-mentioned objective, the present invention provides a light redirecting film, which includes a light redirecting layer and a light guiding layer, wherein the light redirecting layer has a plurality of stripe-shaped micro prisms extending along a first direction and arranged at intervals, and a plurality of diffraction gratings disposed at the bottoms of the intervals of the adjacent stripe-shaped micro prisms, each stripe-shaped micro prism has at least one light guiding inclined plane on one side, and each bottom of the interval has at least one group of diffraction gratings; the light guide layer is disposed on the light redistribution layer and connected to the stripe-shaped microprisms and the diffraction gratings.
In an embodiment of the light redirecting film of the present invention, the light redirecting 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.
In another embodiment of the light redirecting film of the invention, the maximum width of the bottom of each of the bar-shaped microprisms of the light redirecting layer is between 3 μm and 15 μm.
In another embodiment of the light redirecting film of the invention, the height of each of the bar-shaped microprisms of the light redirecting layer is between 5 μm and 15 μm.
In another embodiment of the light redirecting film of the invention, the bottom pitch width of adjacent stripe-shaped microprisms of the light redirecting layer is between 3 μm and 15 μm.
In another embodiment of the light redirecting film of the present invention, the tops of the bar-shaped microprisms of the light redirecting layer are planar, pointed or curved.
In another embodiment of the light redirecting film of the present invention, each of the light guiding inclined planes of the strip-shaped microprisms of the light redirecting layer forms an angle θ with the normal direction of the light redirecting film surface on a cross section perpendicular to the first direction, and the angle θ is not less than 5 ° and not more than 15 °.
In another embodiment of the light redirecting film of the present invention, the period of the diffraction grating disposed at the bottom of the spaces of adjacent stripe-shaped microprisms is between 0.5 μm and 3.0 μm.
In another embodiment of the light redirecting film of the present invention, the height of each diffraction grating disposed at the bottom of the spaces of adjacent stripe-shaped microprisms is between 0.4 μm and 1.0 μm.
In another embodiment of the light redirecting film of the present invention, the light redirecting film further comprises a functional layer formed on a surface of the light guiding layer of the light redirecting film, wherein the functional layer is selected from one of the group consisting of a hard coat layer, an anti-reflection layer, and an anti-glare layer, or a combination thereof.
In addition, the invention also provides a polarizing plate, which comprises a polarizing layer with an absorption axis and the 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 emitting side or the light entering side of the polarizing layer, wherein the light redirecting film comprises a light redirecting layer and a light guiding layer, and the first direction of the extending strip-shaped microprisms of the light redirecting layer intersects with the absorption axis of the polarizing layer at an angle between 90 DEG + -25 deg.
In addition, the invention also provides a display, which comprises a display panel and the polarizing plate, wherein the polarizing plate is used as a display side polarizing plate, the viewing angle extension ratio of the maximum brightness 75% of the normalized display is more than 1.0, and the viewing angle extension ratio of the maximum brightness 40% is more than 1.3.
In another embodiment of the present invention, the maximum tangential slope absolute value of the spectrum of the display brightness normalized with respect to the viewing angle is less than 4.0x10 -2 。
The above summary is intended to provide a simplified summary of the disclosure so that the reader will provide a basic understanding of the disclosure. This summary is not an extensive overview of the disclosure and is intended to neither identify key/critical elements of the embodiments of the invention nor delineate the scope of the invention. Those skilled in the art will readily appreciate the basic spirit of the present invention and the technical means and aspects of the present invention after review of the following detailed description.
The invention will now be described in more detail with reference to the drawings and specific examples, which are not intended to limit the invention thereto.
Drawings
Fig. 1A and 1B are schematic diagrams showing bright light distribution of the lcd at a horizontal viewing angle.
Fig. 2A is a schematic perspective view of a light redirecting film in accordance with one embodiment of the present invention.
Fig. 2B illustrates a cross-sectional view of a light redirecting film in accordance with one embodiment of the present invention.
FIG. 3 is a schematic diagram showing the light guiding effect of a conventional color improving film having only a stripe-shaped micro-prism layer.
FIG. 4 is a schematic view showing the light guiding effect of the light redirecting film according to an embodiment of the invention
Fig. 5 is a schematic view of a light redirecting film as disclosed in accordance with yet another embodiment of the invention.
Fig. 6 is a schematic diagram of a polarizing plate according to another embodiment of the invention.
Fig. 7 is a schematic diagram of a display according to another embodiment of the invention.
FIG. 8 is a diagram showing the normalized spectrum of the measured maximum luminance with the change of viewing angle.
Detailed Description
In order that the manner in which the above recited invention is attained and can be understood in detail, a more particular description of the invention, briefly summarized below, may be had by reference to embodiments thereof which are illustrated in the appended drawings; this is not the only form of practicing or implementing the invention as embodied. The embodiments disclosed below may be combined with or substituted for each other as advantageous, and other embodiments may be added to one embodiment without further description or illustration.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the embodiments below. However, embodiments of the invention may be practiced without these specific details. In other instances, well-known structures and devices are schematically depicted in order to simplify the drawings.
First, referring to fig. 2A and 2B, fig. 2A is a schematic perspective view of a light redirecting film according to an embodiment of the invention, and fig. 2B is a cross-sectional view of a light redirecting film according to an embodiment of the invention along a vertical Y-axis direction. The light redirecting film 10 of the present invention comprises a light redirecting layer 20 and a light guiding layer 30, wherein the light redirecting layer 20 has a plurality of stripe microprisms 21 extending along a first direction D1 and arranged at intervals, and a plurality of diffraction gratings 22 disposed at the bottoms of the intervals between adjacent stripe microprisms 21, each stripe microprism 21 has at least one light guiding inclined plane 21a on one side, and each bottom of the interval has at least one group of diffraction gratings 22; the light guiding layer 30 is disposed on the light redistribution layer 20 and connected to the stripe-shaped micro prisms 21 and the diffraction grating 22. In practice, the first direction D1 may be the length direction or the width direction of the light redirecting film 10.
In the preferred embodiment of the light redirecting film of the present invention, the bottom maximum width W1 of the stripe microprisms 21 is between 3 μm and 15 μm, the height H1 is between 5 μm and 15 μm, and the bottom pitch width W2 of the adjacent stripe 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 stripe-shaped micro prisms 21 is sufficient to provide oblique incidence of the light deflected by the diffraction grating 22, and the bottom maximum width W1 of the stripe-shaped micro prisms 21 and the bottom interval width W2 of the adjacent stripe-shaped micro prisms 21 can be adjusted according to the light guiding ratio of the lateral light source intensity required by the display in practical application.
The light redirecting film 10 of the present invention forms the light redirecting layer 20 and the light guiding layer 30 from curable resins having different refractive indices, and in the interface between the light redirecting layer 20 and the light guiding layer 30, the diffraction grating 22 having a strong diffraction effect and causing the incoming light to be split for the first time, and the light splitting effect of the diffraction grating 22 is related to the grating period, the height, etc., and does not substantially change due to the light path passing through the resin layer having a high refractive index first and then the resin layer having a low refractive index or passing through the resin layer having a low refractive index first and then the resin layer having a high refractive index, but the refractive index difference is required between the two. Therefore, the first refractive index n1 of the light redistribution layer may be selected to be greater than or less than the second refractive index n2 of the light guiding layer. In an embodiment of the 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.
Referring to fig. 3, fig. 3 is a schematic view showing the light guiding effect of a conventional color improving film 40 having only a stripe-shaped micro-prism layer 41. The conventional color improving film 40 deflects the light L incident on the stripe-shaped micro-prism layer 41 by the refractive index difference between the stripe-shaped micro-prism layer 41 and the filling layer 42 and the light guiding inclined surfaces 411a of the plurality of stripe-shaped micro-prisms 411 to improve the side view character deviation problem. However, since the light L is deflected only when passing through the light guiding inclined planes 411a when being normally incident, the light duty ratio of the light passing through the light guiding inclined planes 411a can be changed only by increasing the angle θ between the light guiding inclined planes 411a and the normal line of the film surface under the trend of the display towards thinning; or by increasing the refractive index difference between the stripe-shaped micro-prism layer 41 and the filling layer 42, the deflection degree of the incident light is increased. However, the special optical material with extremely high refractive index or extremely low refractive index is difficult to obtain, and therefore, light cannot be greatly guided to the side view angle to improve the brightness distribution difference between the side view angle range and the front view angle range.
Fig. 4 is a schematic view of the light guiding effect of the light redirecting film 10 of the present invention. In one embodiment, the light redirecting layer 20 of the light redirecting film 10 is disposed on the light incident side of the light beam L, and the light guiding layer 30 is on the light emitting side. The light redistribution layer 20 includes a plurality of stripe-shaped micro prisms 21, and a plurality of diffraction gratings 22 disposed at the bottoms of the spaces between adjacent stripe-shaped micro prisms 21. The diffraction gratings 22 can make the incident light L not only directly pass through the light guiding inclined planes 21a, but also diffract the light L which is originally not deflected at the flat bottom of the interval to deflect, and then obliquely enter the light guiding inclined planes 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 refract, diffract or reflect the light L to a larger angle for multiple times through the adjacent light guiding inclined planes 21a and the diffraction gratings 22 again, so that the light intensity naturally decreases along with the deflection times of the lateral viewing angle, and the brightness distribution difference between the lateral viewing angle range and the front viewing angle range can be reduced, thereby achieving stronger lateral light guiding and homogenizing effects.
In another embodiment of the present invention, the top of the stripe-shaped micro prisms 21 of the light redirecting film 10 is not limited to a plane, a sharp corner or an arc shape, so as not to cause a flickering effect of the bright state image of the display. In a preferred embodiment of the present invention, the tops of the bar-shaped microprisms 21 of the light redirecting film 10 are planar.
In another embodiment of the present invention, each light guiding inclined surface 21a of the bar-shaped micro prisms 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 on the cross section perpendicular to the first direction D1, and the angle θ is preferably not less than 5 ° and not more than 15 °. By the design that the included angle θ is not smaller than 5 °, the light guiding inclined plane 31a can provide enough light guiding incident surface to receive the light from the diffraction gratings 22; by means of the design that the included angle theta is not larger than 15 degrees, the light guide effect is basically linear.
In another embodiment of the present invention, the stripe-shaped micro prisms 21 of the light redirecting film 10 can be configured to have the same or partially the same bottom maximum width W1, height H1, bottom interval width W2 and included angle θ according to the pixel arrangement, pixel size, overall requirement or product design requirement of different display panels, so that the adjacent light guiding inclined planes 21a of the light redirecting film 10 can be symmetrical or asymmetrical.
In another embodiment of the present invention, the period P of diffraction grating 22 of 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 stripe-shaped micro-prisms 21, and the height H2 of the diffraction gratings 22 is smaller than the height of the stripe-shaped micro-prisms 21, the diffraction gratings 22 can generate relatively more diffraction effects without affecting the image resolution. In addition, the size of the diffraction gratings 22 is not lower than the wavelength of visible light, so that no sub-wavelength effect is generated, reflection and penetration degree of the visible light at the interface of the diffraction gratings 22 are not affected, and unexpected design variables are not caused by discontinuity of the diffraction effect.
Referring to fig. 5, in another embodiment of the light redirecting film of the present invention, the light redirecting film 11 further includes a functional layer 50, wherein the functional layer 50 is formed on the surface of the light guiding layer 30 of the light redirecting film 11 (i.e., the functional layer 50 is formed on the surface of the light emitting side of the light redirecting film 11, or called the light emitting surface), and one of the hard coat layer, the anti-reflection layer, the anti-glare layer, or any combination thereof may be selected as the functional layer 50 according to the actual requirements 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 guide layer 30 and has other surface treatment functions appropriately added to the surface as required. In another example of the present invention, the functional layer 50 may be a protective layer outside the light redirecting film 11.
Referring to fig. 6, in still 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 light redirecting film 10 described above, and the light redirecting film 10 is disposed on one side of the polarizing layer 70. In practice, the light redirecting film 10 may be disposed on either the light exit side or the light entrance side of the polarizer 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) in which the stripe-shaped microprisms 21 of the light redirecting layer 20 and the diffraction grating 22 extend intersects with the absorption axis 70a of the polarizing layer 70 at an angle between 90 ° ± 25 ° to enhance the brightness of the horizontal viewing angle and the brightness uniformity 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, and in an embodiment of the integrated polarizing plate of the present invention, the polarizing layer 70 may also be used as a substrate when the light redirecting film 10 is formed by molding the first curable resin to form the light redirecting layer 20, and the light redirecting film 10 may be used as a protective layer of the polarizing layer 70.
Referring to fig. 7 again, another embodiment of the present invention discloses a display 100, wherein the display 100 includes a display panel 80 and the integrated polarizing plate 60 of the above embodiment, and the integrated polarizing plate 60 is used as a display-side polarizing plate. Viewing angle extension value of 75% of maximum brightness of display 100 after normalization>1.0, and a viewing angle extension ratio of 40% at maximum luminance>1.3. Herein, the maximum luminance 75% positive viewing angle range (VW 75) refers to the viewing angle range covered by the display 100, which is 75% or more of the maximum luminance with respect to the vertical viewing angle, after the display is normalized in luminance, and the maximum luminanceThe large luminance 40% side view angle range (VW 40) is a side view angle range in which luminance is 40% or more with respect to the vertical viewing angle maximum luminance. The original 75% front view angle range and the original 40% side view angle range of a conventional display not including the light redirecting film 10 are each defined by VW75 origin And VW40 origin And (3) representing. The viewing angle extension ratio is the original viewing angle ratio of the display 100 of the present invention having the light redirecting film 10 relative to a conventional display that does not include the light redirecting film 10. In the display 100 of the present invention, when the image light of the display panel 80 is redirected perpendicularly to the light redirecting film 10, the light is efficiently laterally conducted to extend the forward and side view angle ranges, i.e., to have a viewing angle extension ratio of greater than 1.0 in the 75% forward view angle range (VW 75/VW75 origin >1.0 And a viewing angle extension ratio of 40% side view angle range of greater than 1.3 (VW 40/VW 40) origin >1.3 Without compromising or limiting the brightness of the positive viewing angle.
The light redirecting film disclosed by the invention can be used for various display panels without being limited by a light emitting mechanism of the panel, and the display panel can improve the bright state image light distribution of a display by matching with the light redirecting film, especially for the display panel with larger difference of the L255 steps of the maximum brightness of a front view angle and a side view angle or faster brightness variation along with the attenuation change of the view angle.
In another embodiment of the present invention, the maximum tangential slope absolute value of the spectrum of the normalized luminance of the display 100 with respect to the viewing angle is less than 4.0x10 -2 When the absolute value of the tangential slope is smaller, the brightness is changed slowly along with the visual angle, and the visual sense is not easily influenced by the human eyes.
The manner and order of formation of the stripe-shaped microprisms 21 and diffraction gratings 22 of the light redirecting film 10 of the present invention are not limited. In an embodiment of the present invention, a first curable resin (not shown) having a first refractive index n1 is first embossed by a mold, an engraving roller, etc. to form a plurality of stripe-shaped micro prisms 21 and a plurality of diffraction gratings 22 extending along the same direction, and after curing 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 planarized to form the light guiding layer 30. In another embodiment of the present invention, a second curable resin (not shown) having a second refractive index n2 as the light guiding layer 30 may be first imprinted by a mold, an engraving roller, etc. with a reverse structure to form a stripe-shaped micro-prism 21 and a plurality of diffraction gratings 22 extending in the same direction corresponding to each other in reverse direction, and then the first curable resin (not shown) having a first refractive index n1 is filled in the imprinted surface of the light guiding layer 30 and planarized to form the light redistribution layer 20 after curing. The interface between the light redistribution layer 20 and the light guide layer 30 may have a microstructure of the stripe-shaped microprisms 21 and the diffraction grating 22. The first curable resin and the second curable resin can be photo-curable resin or thermal curable resin, such as acrylic resin, silicon-on-carbon resin, polyurethane resin, epoxy resin or combination thereof.
The method for manufacturing the stripe-shaped micro prisms 21 and the diffraction gratings 22 of the light redirecting film 10 of the present invention may also be to coat a first curable resin having a first refractive index n1 on a substrate, then to form a plurality of stripe-shaped micro prisms 21 and a plurality of diffraction gratings 22 extending in the same direction by embossing with a mold, an engraving roller, etc., to form the light redirecting layer 20 by curing, and then to cover and planarize the surface of the light redirecting layer 20 with a second curable resin having a second refractive index n2 to form the light guiding layer 30. In another embodiment of the present invention, a second curable resin having a second refractive index n2 used as the light guiding layer 30 may be coated on a substrate and then embossed by a mold, an engraving roller, etc. with a reverse structure to form a stripe-shaped micro prism 21 and a plurality of diffraction gratings 22 extending in the same direction corresponding to each other in reverse direction, and then a first curable resin (not shown) having a first refractive index n1 is filled on the embossed surface of the light guiding layer 30 and planarized to form the light redistribution layer 20. After the light redistribution layer 20 and the light guide layer 30 are fabricated, the substrate may be left or removed. In embodiments where the substrate is used for light redirecting film fabrication, the substrate may be a transparent substrate commonly used in the art, such as polyethylene terephthalate film (PET), cellulose triacetate film (TAC), polymethyl methacrylate film (PMMA), and the like.
The following examples are provided to further illustrate the invention, but the invention is not limited thereto.
Examples
Example 1, example 2 and example 3
Examples 1 to 3 disclose different light redirecting films, wherein the dimensions, material refractive indices, and light guiding slope angles of the stripe-shaped microprisms and diffraction gratings of the light redirecting layers of each example light redirecting film are listed in table 1. The light redirecting film of each embodiment is attached to the same polarizing layer on the light redirecting layer side by an external attaching manner, and the influence of an air layer interface is eliminated, so as to form an integrated polarizing plate, wherein the included angles between the first direction of the extending strip-shaped microprisms of the light redirecting layer and the absorption axis of the polarizing layer are all 105 degrees.
Comparative example
Comparative example 1
Comparative example 1 uses only the same polarizing layer as used in examples 1 to 3 but does not laminate any light guiding structure such as a bar-shaped microprism or diffraction grating.
Comparative example 2 and comparative example 3
Comparative examples 2 and 3 the same external application method and the same angle of absorption axis with the polarizing layer as in the examples were used to laminate the color improving film having stripe-shaped microprisms as illustrated in fig. 3 on the polarizing layer as in the examples. The dimensions, refractive indices, and light guiding slope angles of the stripe-shaped microprisms of the color improving films of comparative examples 2 and 3 are shown in table 1.
Comparative example 4
Comparative example 4 an optical film having a diffraction grating structure was laminated on the polarizing layer as in example 1 using the same external application method as in example 1.
TABLE 1
The integrated polarizers prepared in examples 1 to 3 and comparative examples 2 to 4 and the polarizer of comparative example 1 were attached to a liquid crystal display panel (model No. AUO, VP229 DA) with an adhesive layer, and the maximum brightness change of the bright state L255 steps in the absorption axis direction of the polarizer was measured by a panel measuring instrument Autronic Melchers GmbH Mechanics, conoScope 80, respectively, and the normalized spectrum was shown in FIG. 8, and the test result values are shown in Table 2.
TABLE 2
As is apparent from the test result data of table 2, the integrated polarizing plates having only the stripe-shaped microprism optical film used in comparative examples 2 and 3 and the integrated polarizing plate having only the diffraction grating optical film used in comparative example 4 have both the effects of increasing the coverage angle range of the side viewing angle and reducing the maximum slope of the brightness curve on the lcd at the same time, which are difficult to achieve, compared to the polarizing plate having no light guiding structure used in comparative example 1. In particular, in comparative example 3 having only the stripe-shaped microprism structure, even if the height of the stripe-shaped microprism has been greatly increased, the light guiding capability of the light guiding inclined surface in the receiving side direction is increased, but the coverage range of the side view angle at a luminance of 40% or more still has a limit, and only 78 ° can be reached, while the maximum slope of the luminance variation curve with the viewing angle can be reduced, the coverage range of the front view angle at a luminance of 75% or more has been slightly reduced, and it is difficult to expect that the side light guiding effect can be improved by increasing the structure thickness again. In comparative example 4 having only the diffraction grating structure, the effect of greatly diffracting light to the side view angle was not good, although the front view angle range was not affected. From the measurement values of table 2 and the spectrum of the maximum luminance versus viewing angle of fig. 8, comparative example 1 without any light guiding structure film was used as a control, and 40% of the maximum luminance thereof was used as representative of the original 40% side view angle range (VW 40 origin ) And 75% of maximum brightness represents the original 75% of the positive viewing angle range (VW 75 origin ) Examples 1 to 3 are each effective for extending the extended viewing angle, especially over a range of side view angles of 40% or more of maximum brightnessThe surrounding (VW 40) has excellent lifting efficiency, and the 40% view angle extension ratio VW40/VW40 origin All are above 1.3, and for a positive viewing angle range (VW 75) of above 75% of maximum brightness, a 75% viewing angle extension ratio VW75/VW75 origin Still greater than 1.0 and superior to the original viewing angle, but without limiting the original positive viewing angle range, only the peak value of the maximum brightness L255 tone of the vertical viewing angle is reduced and the effective light guiding is uniformly distributed to the side view angle, so that the maximum tangential slope of the spectrum of brightness along with the change of the viewing angle can be kept lower than 4.0x10 -2 The bright state spectrum of the display is made to approach the ideal normal distribution curve.
Of course, the present invention is capable of other various embodiments and its several details are capable of modification and variation in light of the present invention by one skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (13)
1. A light redirecting film comprising:
the light redistribution layer is provided with a plurality of strip-shaped micro prisms extending along a first direction and arranged at intervals and a plurality of diffraction gratings arranged at the bottoms of the intervals of the adjacent strip-shaped micro prisms, wherein each strip-shaped micro prism is provided with at least one light guide inclined plane at one side, and each bottom of the interval is provided with at least one group of diffraction gratings; and
the light guide layer is arranged on the light redistribution layer and is connected with the plurality of strip-shaped microprisms and the plurality of diffraction gratings.
2. The light redirecting film of claim 1 wherein the light redirecting layer has a first refractive index n1 and the light guiding layer has a second refractive index n2, the first refractive index n1 and the second refractive index n2 being between 1.4 and 1.7, and the difference between the first refractive index n1 and the second refractive index n2 being no less than 0.05.
3. The light redirecting film of claim 1 wherein the maximum width of the bottom of each stripe-shaped microprism of the light redirecting layer is between 3 μm and 15 μm.
4. The light redirecting film of claim 1 wherein the height of each of the bar-shaped microprisms of the light redirecting layer is between 5 μm and 15 μm.
5. The light redirecting film of claim 1 wherein the bottom pitch width of adjacent stripe-shaped microprisms of the light redirecting layer is between 3 μm and 15 μm.
6. The light redirecting film of claim 1 wherein the tops of the plurality of stripe-shaped microprisms of the light redirecting layer are planar, pointed or curved.
7. The light redirecting film of claim 1 wherein each light guiding slope of the plurality of stripe-shaped microprisms of the light redirecting layer forms an angle θ with respect to a normal to the light redirecting film surface on a cross-section perpendicular to the first direction, the angle θ being no less than 5 ° and no greater than 15 °.
8. The light redirecting film of claim 1 wherein the period of the plurality of diffraction gratings of the light redirecting layer is between 0.5 μm and 3.0 μm.
9. The light redirecting film of claim 1 wherein the height of each diffraction grating of the light redirecting layer is between 0.4 μm and 1.0 μm.
10. The light redirecting film of claim 1 comprising a functional layer formed on a surface of the light-exiting side of the light redirecting film, wherein the functional layer is selected from the group consisting of a hard coat layer, an antireflective layer, and an antiglare layer, or any combination thereof.
11. A polarizing plate comprising a polarizing layer having an absorption axis and the light redirecting film of any one of claims 1 to 10, wherein the light redirecting film is disposed on one side of the polarizing layer, the first direction in which the plurality of stripe-shaped microprisms of the light redirecting layer extend intersects the absorption axis of the polarizing layer at an angle between 90 ° ± 25 °.
12. A display comprising a display panel and the polarizing plate according to claim 11, wherein the viewing angle extension ratio of 75% of the maximum brightness of the display after brightness normalization is >1.0, and the viewing angle extension ratio of 40% of the maximum brightness is >1.3.
13. The display of claim 12, wherein the normalized maximum brightness has a maximum tangential slope absolute value of the viewing angle dependent spectrum of less than 4.0x10 -2 。
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|---|---|---|---|
| CN202111611990.9A CN116360148A (en) | 2021-12-27 | 2021-12-27 | Light redirecting film, polarizing plate and display comprising polarizing plate |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202111611990.9A CN116360148A (en) | 2021-12-27 | 2021-12-27 | Light redirecting film, polarizing plate and display comprising polarizing plate |
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| CN116360148A true CN116360148A (en) | 2023-06-30 |
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| CN202111611990.9A Pending CN116360148A (en) | 2021-12-27 | 2021-12-27 | Light redirecting film, polarizing plate and display comprising polarizing plate |
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