Optical film and backlight unit including optical film

Abstract

To provide an optical film.SOLUTION: The optical film according to various different embodiments of the present disclosure includes: a first base part; and a first sheet having a pyramid pattern layer having a plurality of pyramid patterns with a first pitch pi1 in a first surface of the first base and a first prism pattern layer having a plurality of prism patterns with a second pitch Pi2 in a second surface of the first base part.SELECTED DRAWING: Figure 11b

Description

[Technical Field]

[0001] Various embodiments of the present disclosure relate to optical films for use in liquid crystal displays and backlight units including the optical films. [Background technology]

[0002] Generally, a liquid crystal display (LCD) may include a backlight unit that uniformly irradiates light across the entire screen of an electronic device. The backlight unit may include a light source, a light guide plate, a diffusion sheet, and an optical film including a prism. Light emitted from the light source is transmitted upward through the light guide plate, and the transmitted light is diffused through the diffusion sheet and then transmitted to the LCD panel through the optical film provided on the upper side. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] US Patent Application Publication No. 2015 / 0226999 Summary of the Invention [Problem to be solved by the invention]

[0004] Recently, display devices have been developed with a gradually decreasing thickness, which has led to a demand for thinner backlight units. Developments have been made to eliminate the relatively thick diffusion sheet in backlight units. For example, research has been conducted to eliminate or replace the diffusion sheet in embodiments of backlight units that include a light source, a light guide plate, a diffusion sheet, and a prism sheet.

[0005] The diffusion sheet may have a diffusion layer formed on one and / or the other side. The diffusion layer generally contains light diffusing beads, which diffuse light from the light source and the light guide plate toward the prism sheet over a wider area while also acting as a shielding sheet that reduces the visibility of the light source. Because diffusion sheets are generally thick and hinder the improvement of the brightness of the backlight unit, efforts are being made to replace them.

[0006] As an example, as disclosed below in various embodiments of the present invention, by replacing the diffusion sheet with a sheet including a pyramid pattern and an inverted prism pattern, the thickness of the backlight unit can be reduced while improving the brightness.

[0007] However, when a sheet including a pyramid pattern and an inverted prism pattern is used instead of the diffusion sheet, a problem of moire occurring due to the arrangement of the pyramid pattern and the inverted prism pattern may occur.

[0008] The present invention aims to provide an optical film for a liquid crystal display device, through various embodiments, that has excellent performance in preventing the shape of a light source from being visible (hereinafter also referred to as "shielding performance") and high brightness (hereinafter also referred to as "brightness performance") without using a thick diffusion sheet. Furthermore, various embodiments of the optical film can be provided to effectively avoid moire when a sheet including a pyramid pattern and an inverted prism pattern is used instead of a diffusion sheet. [Means for solving the problem]

[0009] According to various embodiments of the present disclosure, an optical film can be provided, which includes a first sheet including a first base portion, a pyramid pattern layer having a plurality of pyramid patterns with a first pitch pi1 formed on a first surface of the first base portion, and a first prism pattern layer having a plurality of prism patterns with a second pitch pi2 formed on a second surface of the first base portion. [Effects of the Invention]

[0010] According to various embodiments of the present disclosure, an optical film and a backlight unit including the same can be provided in which moiré is reduced and / or prevented.

[0011] According to various embodiments of the present disclosure, the backlight unit does not include a thick diffusion sheet, which can contribute to making the backlight unit thinner.

[0012] According to various embodiments of the present disclosure, an optical film having excellent light source shielding performance and excellent brightness performance, and a backlight unit including the same can be provided.

[0013] The effects obtained by the present disclosure are not limited to the effects mentioned above, and other effects not mentioned will be clearly understood by a person having ordinary skill in the technical field to which the present disclosure pertains from the following description.

[0014] The above-described aspects and other aspects, features and / or advantages of one embodiment of the present disclosure may become more apparent from the following detailed description that refers to the accompanying drawings. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a perspective view illustrating a liquid crystal display device including an optical film according to an embodiment. [Figure 2] 1 is a diagram illustrating a liquid crystal display device including an optical film according to an embodiment. [Figure 3]1 is a diagram illustrating a liquid crystal display device including an optical film according to an embodiment. [Figure 4a] 1 is a cross-sectional view illustrating an optical film according to an embodiment. [Figure 4b] 1 is a cross-sectional view illustrating an optical film according to an embodiment. [Figure 4c] 1 is a cross-sectional view illustrating an optical film according to an embodiment. [Figure 4d] FIG. 1 illustrates a pyramidal pattern and a prism pattern according to one embodiment. [Figure 4e] FIG. 1 illustrates a top view of a pyramidal pattern layer prior to lamination according to one embodiment. [Figure 4f] FIG. 10 illustrates a top view of a pyramidal pattern layer after lamination according to one embodiment. [Figure 5a] 1 illustrates an experimental setup for measuring the brightness of an optical film according to one embodiment. [Figure 5b] FIG. 1 illustrates a light distribution diagram and optimal incident angle for enhanced brightness according to one embodiment. [Figure 6a] 10A and 10B are diagrams showing the appearance of a liquid crystal panel with an arrangement of an inverted prism pattern (first prism pattern layer) and a pyramid pattern according to a certain embodiment. [Figure 6b] FIG. 10 is a diagram showing the appearance of a liquid crystal panel with an arrangement of an inverted prism pattern (first prism pattern layer) and a pyramid pattern according to an embodiment. [Figure 7] 1 is a perspective view illustrating a liquid crystal display device including an optical film according to an embodiment. [Figure 8a] 1A-1C illustrate arrangements of pyramidal and prism patterns according to various embodiments. [Figure 8b] 1A-1C illustrate optical properties of optical films according to various embodiments. [Figure 9a] 1A-1C illustrate arrangements of pyramidal and prism patterns according to various embodiments. [Figure 9b]1A-1C illustrate optical properties of optical films according to various embodiments. [Figure 10a] 1A-1C illustrate moiré simulation results according to various embodiments. [Figure 10b] 1A-1C illustrate moiré simulation results according to various embodiments. [Figure 11a] FIG. 1 illustrates an arrangement of pyramid and prism patterns according to one embodiment. [Figure 11b] FIG. 1 illustrates an arrangement of pyramid and prism patterns according to one embodiment. [Figure 11c] FIG. 1 illustrates an arrangement of pyramid and prism patterns according to one embodiment. [Figure 11d] FIG. 1 illustrates an arrangement of pyramid and prism patterns according to one embodiment. [Figure 12] 1A-1C are diagrams comparing raised and recessed pyramid patterns according to various embodiments. [Figure 13] 10A-10C illustrate optical properties according to the refractive index of a pyramid pattern and the refractive index of an inverse prism pattern, in accordance with various embodiments. DETAILED DESCRIPTION OF THE INVENTION

[0016] The various embodiments of the present disclosure and the terms used therein are not intended to limit the technical features described in the present disclosure to specific embodiments, but should be understood to include various modifications, equivalents, or alternatives of the embodiments. In connection with the description of the drawings, like reference numerals may be used for similar or related components. The singular form of a noun corresponding to an item may include one or more of the said item, unless otherwise specified in the relevant context.

[0017] According to various embodiments, each of the aforementioned components (e.g., modules or programs) may include one or more objects, and some of the multiple objects may be located separately in other components. According to various embodiments, one or more of the aforementioned components or operations may be omitted, or one or more other components or operations may be added. Alternatively, or additionally, multiple components (e.g., modules or programs) may be integrated into a single component. In such cases, the integrated component may perform one or more functions of each of the multiple components that are the same as or similar to those performed by the multiple components prior to integration. According to various embodiments, operations performed by a module, program, or other component may be performed sequentially, in parallel, iteratively, or heuristically, or one or more of the operations may be performed in a different order, omitted, or one or more other operations may be added.

[0018] Various embodiments will be described below with reference to the accompanying drawings. In describing the present embodiments, the same components will be designated by the same names and reference numerals, and additional description thereof will be omitted. Furthermore, in describing the embodiments of the present invention, components having the same functions will be designated by the same names and reference numerals, but it should be noted that they are not substantially the same as those of the prior art.

[0019] In various embodiments, terms such as "comprise" or "have" should be understood to indicate the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, without precluding the possible presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0020] FIG. 1 is a perspective view showing a liquid crystal display device including an optical film according to an embodiment.

[0021] In the following detailed description, the longitudinal direction (vertical direction) of the liquid crystal display device 1 may be defined as the "Y-axis direction," the width direction (horizontal direction) as the "X-axis direction," and / or the height direction (thickness direction) as the "Z-axis direction." Furthermore, in some embodiments, the direction in which components are oriented may be expressed using "negative / positive (- / +)" in conjunction with the Cartesian coordinate system illustrated in the drawings. As shown in FIG. 1, if "negative / positive (- / +)" is not indicated in the Cartesian coordinate system, the coordinate axis may be interpreted as pointing in the positive direction unless otherwise defined. For example, the "X-axis direction" may be interpreted as referring to the +X-axis direction, the "Y-axis direction" may be interpreted as referring to the +Y-axis direction, and the "Z-axis direction" may be interpreted as referring to the +Z-axis direction. For example, referring to FIG. 1, if the second sheet 120 is disposed over the first sheet 110, the second sheet 120 may be defined as being disposed in the "+Z-axis direction" from the first sheet 110. 4a, for example, one surface (e.g., first surface 112a) of the first base portion 112 can be defined as a "surface facing the +Z axis direction," and the other surface (e.g., second surface 112b) can be defined as a "surface facing the -Z axis direction." According to one embodiment, the traveling direction of the light source in the description of the optical film 100 can be expressed as, for example, the "+Z axis direction." When describing directions, in the following description of directions, "facing one of the three axes of a Cartesian coordinate system" may also include "facing a direction parallel to an axis." It should be noted that this is based on the Cartesian coordinate system depicted in the drawings for the sake of simplicity, and that the description of such directions or components does not limit the various embodiments of the present disclosure.

[0022] Referring to FIG. 1, a liquid crystal display device (or LCD (liquid crystal display) device) 1 may include a backlight unit 10 and a liquid crystal panel 20. According to various embodiments, the backlight unit 10 may face the rear surface (surface facing the -Z axis direction) of the liquid crystal panel 20 so as to emit light to the liquid crystal panel 20. The backlight unit 10 may include a light source 11, a light guide plate 12, a reflector 13, an optical film 100, and a diffusion sheet 17. Although not shown in the drawings, the backlight unit 10 may further include a reflective polarizing sheet.

[0023] The light source 11 is configured to radiate light toward the rear surface of the liquid crystal panel 20 and may be disposed on one side of the light guide plate (LGP) 12. Light sources may be classified as edge-type or direct-type depending on their arrangement. In the present disclosure, an edge-type light source may be used, as shown in FIG. 1 . The light source 11 is configured to irradiate light toward the rear surface of the liquid crystal panel 20, and the light emitted from the light source 11 may be converted into a surface light source by the light guide plate 12. In this case, the light source 11 may be a cold cathode fluorescent lamp (CCFL) or an external electrode fluorescent lamp (EEFL). The reflector 13 is disposed behind the light guide plate 12 and reflects light emitted toward the rear of the light guide plate 12 (the surface facing the −Z axis direction) toward the light guide plate 12, thereby minimizing light loss. In other words, the reflector 13 may perform light recycling.

[0024] 1 , light emitted from light guide plate 12 is incident on optical film 100, and optical film 100 of the present disclosure includes at least one prism sheet for concentrating light, and may further include a sheet including a pyramid pattern as a sheet for uniformly dispersing the light incident from light guide plate 12 and then causing the light to be incident on the prism sheet. For ease of explanation, hereinafter, one prism sheet or a combination of two or more prism sheets for concentrating light included in optical film 100 will be referred to as a "concentrating prism sheet" (or a "cross prism sheet"), and a sheet including a pyramid pattern will be referred to as a "pyramid sheet."

[0025] As will be described in detail below, the optical film 100 of the present disclosure may include a first sheet 110 (or first optical sheet 110) as a pyramid sheet, having a pyramid pattern formed on one surface facing parallel to the light source traveling direction (e.g., the Z-axis direction) and a prism pattern (i.e., an inverted prism pattern) formed on the other surface facing opposite to the light source traveling direction. The optical film 100 of the present disclosure may also include a second sheet 120 as a condensing prism sheet, having a prism pattern formed on one surface facing parallel to the light source traveling direction (e.g., the +Z-axis direction). According to one embodiment, the second sheet 120 (or second optical sheet 120) may have a diffusion layer formed on the other surface facing opposite to the light source traveling direction. According to one embodiment, the optical film 100 of the present disclosure may further include, in addition to the second sheet 120, a third sheet 130 (or third optical sheet 130) as a condensing prism sheet, including a prism pattern having a ridge line direction different from that of the prism pattern formed on the second sheet 120. According to one embodiment, a diffusion layer may also be formed on the other surface of the third sheet 130, facing in the direction opposite to the traveling direction of the light source.

[0026] The light-collecting prism sheet (second sheet 120 and / or third sheet 130) can collect incident light using an optical pattern formed on its surface and then emit the collected light to the liquid crystal panel 20. The light-collecting prism sheet (second sheet 120 and / or third sheet 130) can include a light-transmitting base film and a prism pattern layer formed on the upper surface (surface facing the +Z axis direction) of the base film. The prism pattern layer can be formed as an optical pattern layer in the form of a triangular array with inclined surfaces at a specified angle (e.g., 45° inclined surfaces) formed to improve brightness in the in-plane direction. The prism pattern of the prism pattern layer can be in the shape of a triangular prism, and one surface of the triangular prism can be arranged to face the base film. Each cross section of the prism pattern can be triangular.

[0027] According to one embodiment, the condensing prism sheet (second sheet 120 and / or third sheet 130) may form a composite prism sheet structure including the second sheet 120 and the third sheet 130. Here, the third sheet 130 may be disposed over the second sheet 120 so as to overlap it. In the second sheet 120, a plurality of second prism patterns may be disposed side by side. Each second prism pattern may have a structure extending in one direction. For example, each vertex line (hereinafter referred to as a "crest" or "ridge") of the second prism pattern may be formed to extend in the X-axis direction. Similarly, in the third sheet 130, a plurality of third prism patterns may be disposed side by side. Each third prism pattern may have a structure extending in one direction. For example, each ridge line of the third prism pattern may be formed to extend in the Y-axis direction perpendicular to the X-axis. Here, for convenience of explanation, the extension direction of the first prism pattern and the extension direction of the second prism pattern are shown along the X-axis and Y-axis, respectively. However, it should be noted that this is not limited to the illustrated embodiment and the extension direction may be along a direction other than the X-axis or Y-axis.

[0028] According to one embodiment, a prism pattern (plurality of first prism patterns) may also be formed on the pyramid sheet (first sheet 110). Unlike the plurality of second prism patterns included in the second sheet 120 and the plurality of third prism patterns included in the third sheet 130, the plurality of first prism patterns included in the first sheet 110 may be formed to protrude in the opposite direction (-Z axis direction) to the light propagation direction, rather than in the direction parallel to the light propagation direction (+Z axis direction). Therefore, the plurality of first prism patterns included in the first sheet 110 may be referred to as an "inverse prism pattern." The ridge direction P1 (hereinafter referred to as the "third direction") of the plurality of first prism patterns may be formed to be the same as or different from the ridge direction P2 (hereinafter referred to as the "fourth direction") of the plurality of second prism patterns and the ridge direction P3 (hereinafter referred to as the "fifth direction") of the plurality of third prism patterns. 1, the ridge direction P1 of the first prism patterns can be formed perpendicular to the ridge direction P2 of the second prism patterns and parallel to the ridge direction P3 of the third prism patterns, and the liquid crystal display device 1 of the present disclosure can achieve the corresponding effects. The ridge direction will be described in more detail later.

[0029] The diffusion sheet 17 can uniformly disperse light incident from the optical film 100. The diffusion sheet 17 can be formed by applying a solution of a curable resin (e.g., a mixture of one or more selected from at least one of urethane acrylate, epoxy acrylate, ester acrylate, ester acrylate, and radical-generating monomer) to which light diffusing beads have been added, thereby causing light diffusion through the light diffusing beads. The diffusion sheet 17 can also be formed with a protrusion pattern (or protrusions) of uniform or non-uniform size and shape (e.g., spherical, hemispherical, or elliptical) to promote light diffusion. According to some embodiments of the prior art, the diffusion sheet 17 may include not only the upper diffusion sheet 17 disposed over the condensing prism sheet shown in FIG. 1 but also a lower diffusion sheet disposed below the condensing prism sheet. However, in the present disclosure, the lower diffusion sheet can be replaced by providing an optical film 100 that combines a condensing prism sheet and a pyramid sheet.

[0030] According to one embodiment, the backlight unit 10 may omit at least one of the aforementioned components (e.g., the diffusion sheet 17) or may add one or more other components (e.g., a reflective polarizing sheet (not shown)).

[0031] A reflective polarizing sheet (not shown) is provided on top of the optical film 100 and the diffusion sheet 17, and can serve to transmit some of the polarized light collected from the optical film 100 and diffused by the upper diffusion sheet, and reflect the other polarized light downward.

[0032] The liquid crystal panel 20 can refract the light emitted from the light source 11 in a predetermined pattern in response to an electrical signal. This refracted light passes through a color filter and a polarizing filter arranged in front of the liquid crystal panel 20 to form a screen.

[0033] 1 can be assembled in a state where the components included in the liquid crystal display device 1 are overlapped and stacked with other components in the height direction (+Z-axis direction). For example, in the liquid crystal display device 1 according to some embodiments, as shown in FIG. 1, the backlight unit 10 and the liquid crystal panel 20, which are manufactured separately, can be overlapped and stacked in the height direction (+Z-axis direction).

[0034] 2 and 3 are diagrams illustrating a liquid crystal display device including an optical film according to an embodiment.

[0035] Fig. 2 shows a cross section parallel to the plane formed by the Y-axis and Z-axis of the liquid crystal display device 1, and Fig. 3 shows a cross section parallel to the plane formed by the X-axis and Z-axis of the liquid crystal display device 1. Hereinafter, explanations of parts that overlap with Fig. 1 will be omitted.

[0036] The liquid crystal display device 1 of the present disclosure can be characterized in that no separate diffusion sheet (e.g., a lower diffusion sheet) is provided between the optical film 100 and the light guide plate 12, and the diffusion sheet is replaced only by the optical film 100 of the present disclosure.

[0037] In the present disclosure, the term "optical film 100" may refer to a film including a first sheet 110 having a plurality of pyramidal patterns formed on one surface thereof, a second sheet 120 disposed on the first sheet 110 and having a plurality of prism patterns formed on one surface thereof, and a third sheet 130 disposed on the second sheet 120 and having a plurality of prism patterns formed on one surface thereof, as shown in FIGS. 1 to 3. For convenience of explanation, the first sheet 110, the second sheet 120, and the third sheet 130 are shown as being spaced apart from one another in FIGS. 1 to 3. However, the first sheet 110, the second sheet 120, and the third sheet 130 may alternatively be formed by lamination with one another. In the present disclosure, "lamination" may refer to two different sheets being bonded together by including a pattern formed of an adhesive resin on at least one of the opposing surfaces of the two different sheets. For example, one of the two opposing surfaces of two different sheets may have a pattern formed with a semi-cured adhesive resin, and the other surface may be brought into contact with this pattern, and then fully cured and bonded together. Alternatively, the opposing surfaces of the two different sheets may be formed with a semi-cured adhesive resin on both sides, and after they come into contact with each other, they may be fully cured and bonded together. The laminated optical film 100 can provide a backlight unit that is thinner and has excellent shielding performance than an embodiment in which the optical film 100 is simply stacked without lamination.

[0038] The plurality of pyramid (or quadrangular pyramid) patterns of the first sheet 110 can refract and / or reflect light transmitted from the light source 11 and transmit the light to the second sheet 120. The second sheet 120 may be formed with a plurality of prisms (or triangular prisms) extending in the width direction (X-axis direction) of the liquid crystal display device 1 and protruding in the height direction (Z-axis direction). The second sheet 120 can transmit the light that has passed through the first sheet 110 to the third sheet 130. The third sheet 130 may be formed with a plurality of prisms (or triangular prisms) extending in the length direction (Y-axis direction) of the liquid crystal display device 1 and protruding in the height direction (Z-axis direction). The third sheet 130 can transmit the light that has passed through the second sheet 120 toward the liquid crystal panel 20. Light incident on the optical film 100 from the light source 11 is diffused and / or concentrated as it passes through the first sheet 110, the second sheet 120, and the third sheet 130 in that order, which has the advantage of ensuring not only the shielding performance of covering the shape of the light source 11 but also high brightness. In the embodiment shown in FIGS. 1 to 3 , the multiple prism patterns on the second sheet 120 extend in the width direction (X-axis direction) of the liquid crystal display device 1, and the multiple prism patterns on the third sheet 130 extend in the longitudinal direction (Y-axis direction) of the liquid crystal display device 1. However, this is not necessarily limited thereto. The multiple prism patterns on the second sheet 120 may extend in the longitudinal direction (Y-axis direction) of the liquid crystal display device 1, and the multiple prism patterns on the third sheet 130 may extend in the width direction (X-axis direction) of the liquid crystal display device 1. However, it is sufficient that the multiple prism patterns on the second sheet 120 and the multiple prism patterns on the third sheet 130 are perpendicular to each other.

[0039] Referring again to FIG. 1, the pyramid-patterned layer 111 of the first sheet 110 may include a pyramid pattern (hereinafter referred to as pyramid pattern 111a in FIG. 4a) including a bottom surface having a base with a length a in a first direction and a length b in a second direction, and four side surfaces 111-1, 111-2, 111-3, and 111-4 with height h and apex angles A and B. The dimensions of the pyramid pattern may be set differently depending on the embodiment. When viewed from above (e.g., in the direction opposite to the Z axis) the bottom surface of the pyramid pattern 111a, having a base with a length a in the first direction and a length b in the second direction, may have a rectangular shape, with a diagonal length of c. According to one embodiment, the bottom surface of the pyramidal pattern 111a may be square, in which case the length in the first direction and the length in the second direction are equal to each other (a=b), and the length of the diagonal line c may have a value of √2a. However, it should be noted that in the present disclosure, the bottom surface of the pyramidal pattern 111a being square includes, but is not necessarily limited to, the case where the length in the first direction and the length in the second direction are equal to each other (a=b), and may also include the case where the length in the first direction and the length in the second direction are different within a predetermined error range (e.g., an error range of 15%) (a≠b).

[0040] The optical film 100 will now be described in more detail with reference to FIGS. 4a to 4f.

[0041] Figure 4a is a cross-sectional view of an optical film according to an embodiment. Figure 4b is a cross-sectional view of an optical film according to an embodiment. Figure 4c is a cross-sectional view of an optical film according to an embodiment. Figure 4d is a diagram showing a pyramid pattern and a prism pattern according to an embodiment. Figure 4e is a diagram showing a top view of a pyramid pattern layer before lamination according to an embodiment. Figure 4f is a diagram showing a top view of a pyramid pattern layer after lamination according to an embodiment.

[0042] 4a to 4c, an optical film 100 according to an embodiment of the present disclosure may include an optical film 100a including a first sheet 110, an optical film 100b including the first sheet 110 and a second sheet 120, and an optical film 100c including the first sheet 110, the second sheet 120, and a third sheet 130. For example, the first sheet 110 may be used alone as a component of the optical film 100a without other sheets (e.g., the second sheet 120 and the third sheet 130). According to the present disclosure, the second sheet 120 and / or the third sheet 130 may further include the first sheet 110, thereby providing an optical film with excellent light source shielding performance and excellent brightness performance. Hereinafter, for convenience, each component included in the optical film 100 will be described in detail using the optical film 100c of FIG. 4c as an example unless otherwise specified. It should be noted that according to one embodiment, not only an optical film having three sheets 110, 120, 130 (e.g., optical film 100c in FIG. 4c), but also an optical film having one sheet 110 (e.g., optical film 100a in FIG. 4a) and an optical film having two sheets 110, 120 (e.g., optical film 100b in FIG. 4b) may be included within the scope of the present invention.

[0043] 4c, in the optical film 100 (e.g., optical film 100c), the first sheet 110, the second sheet 120, and the third sheet 130 may include a first base portion 112, a second base portion 122, and a third base portion 132, respectively. In this case, the first base portion 112, the second base portion 122, and the third base portion 132 may include a transparent material that can transmit light, such as a polycarbonate-based, polysulfone-based, polyacrylate-based, polystyrene-based, polyvinyl chloride-based, polyvinyl alcohol-based, polynorbornene-based, or polyester-based material. As a specific example, the first base portion 112, the second base portion 122, and / or the third base portion 132 may be made of polyethylene terephthalate (PET) or polyethylene naphthalate. The first base portion 112, the second base portion 122, and the third base portion 132 may be made of PET having a thickness of, for example, about 10 to about 50 μm, more specifically, about 24 to about 40 μm. In various experimental examples including the viewing angle distribution described below with reference to FIG. 6a and subsequent drawings, the first base portion 112, the second base portion 122, and the third base portion 132 may each be made of PET having a thickness of 24 μm. However, it should be noted that the thicknesses of the first base portion 112, the second base portion 122, and the third base portion 132 are not limited to the above example.

[0044] 1, the first sheet 110 may include, on a first surface 112a of a first base portion 112, a pyramid pattern 111a in the form of a quadrangular pyramid corresponding to four side surfaces 111-1, 111-2, 111-3, and 111-4 that form a length a in a first direction, a length b in a second direction, a height h, a pitch P, and apex angles A and B. The optical film 100 may include a plurality of pyramid patterns 111a having a plurality of columns in a first direction and a plurality of rows in a second direction perpendicular to the first direction.

[0045] Referring to FIGS. 4a and 4d together, according to one embodiment, the pyramidal pattern 111a may be an intaglio pattern. The pyramidal pattern 111a may refer to an intaglio pattern having regularly formed quadrangular pyramidal grooves and may be defined by four side surfaces 111-1, 111-2, 111-3, and 111-4. Here, the four side surfaces may be the same or different triangular shapes, and the dimensions of the apex angles A and B may be set according to the horizontal length a, vertical length b, and height of each cross section of the pyramidal pattern 111a. According to one embodiment, the apex angles A and B may form substantially the same angle, thereby allowing the horizontal length a and vertical length b of the pyramidal pattern 111a to be set substantially equal. Here, "the apex angles A and B being substantially the same" may mean that the apex angles A and B have the same value within a process tolerance (e.g., within 10%).

[0046] Furthermore, the height h and pitch P of the pyramidal pattern 111a can be set based on the vertex angle C. The optical film 100 includes pyramidal patterns 111a whose vertical cross sections parallel to the height direction (Z-axis direction) are triangular or trapezoidal, and the vertex angle C can be defined as the angle between two opposing side surfaces among the four side surfaces of the pyramidal pattern 111a.

[0047] According to one embodiment, the apex angle C of the pyramidal pattern 111a may be defined as being between 60 degrees and 160 degrees. For example, the apex angle C may be 90 degrees. Within the specified range, the larger the apex angle C of the pyramidal pattern 111a, the larger the angle θ (theta) of light incident on the second sheet 120 (hereinafter referred to as the "incident angle θ"). For example, in an optical film including three sheets (e.g., optical film 100c) of the present disclosure, the first sheet 110 including the pyramidal pattern 111a may function to ensure that light incident on the second sheet 120 and the third sheet 130 is incident at an optimal angle to enhance brightness. The relationship between the components of the optical film and brightness will be described in more detail below through embodiments starting with FIG. 5.

[0048] According to one embodiment, the pyramidal pattern 111a may be formed as a relief pattern.

[0049] 4e shows the pyramid-pattern layer before the first sheet 110 is laminated to the second sheet 120, and FIG. 4f shows the pyramid-pattern layer after the first sheet 110 has been laminated to the second sheet 120 and then peeled from the second sheet 120. Referring to FIG. 4e, the pyramid-pattern layer 111 before lamination may include a first partition wall 111-5 between the first side surface 111-1 and the fourth side surface 111-4 that distinguishes the boundary between the first side surface 111-1 and the fourth side surface 111-4, and a second partition wall 111-6 between the second side surface 111-2 and the third side surface 111-3 that distinguishes the boundary between the second side surface 111-2 and the third side surface 111-3. The first partition wall 111-5 and the second partition wall 111-6 may be the highest portions of the first sheet 110. According to one embodiment, the first partition wall 111-5 is parallel to the first direction, and the second partition wall 111-6 is parallel to the second direction, but this is not necessarily limited to this. Referring to FIG. 4F, when the pyramid pattern layer 111 located on the upper surface of the first sheet 110 is laminated to the back surface of the second sheet 120 (e.g., the back surface of the second base portion 122 of the second sheet 120 or the first diffusion layer 123 of the second sheet 120), the ends of the first partition wall 111-5 and the second partition wall 111-6, which are located at the top end of the pyramid pattern layer 111, may be pressed. As a result, the tip of the first partition wall 111-5 is deformed to form a first flat portion 111-7 having a predetermined width W1, and the tip of the second partition wall 111-6 is deformed to form a second flat portion 111-8 having a predetermined width W2. According to one embodiment, the width W1 of the first flat portion 111-7 and the width W2 of the second flat portion 111-8 may be substantially equal.

[0050] According to various embodiments of the present disclosure, the pyramid pattern layer 111 can control light in four peripheral directions. According to one embodiment of the present disclosure, the pyramid pattern layer 111 can include pyramid patterns 111a having a vertex angle, which is the angle between two opposing triangles, of 90 degrees or more and 130 degrees or less. According to one embodiment, when the vertex angle of the pyramid pattern 111a is at least 90 degrees, shielding performance can be satisfied, as shown in FIG. 6a . When the vertex angle is less than 90 degrees, hot spot visibility (HSV), in which the light source 11a is visible, can be increased.

[0051] The pyramid pattern layer 111 may be composed of a plurality of pyramid patterns, which may be regularly arranged on the first surface 112a of the first sheet 110. A first prism pattern layer 113 including a plurality of first prism patterns may be formed on the second surface 112b of the first base portion 112. The first prism pattern layer 113 may have substantially the same configuration as the second prism pattern layer 121 provided on the second sheet 120 and the third prism pattern layer 131 provided on the third sheet 130, except for the direction in which they are arranged.

[0052] The second sheet 120 may include a second prism pattern layer 121 on a first surface 122a of a second base portion 122, in which a plurality of second prism patterns extending parallel to one another in the width direction (or longitudinal direction) of the liquid crystal display device 1 are formed. The cross section of the second prism pattern layer 121 may be triangular. For example, the plurality of second prism patterns included in the second prism pattern layer 121 may be formed with a pitch of pi3 and a height of h3. The third sheet 130 may include a third prism pattern layer 131 on a first surface 132a of a third base portion 132, in which a plurality of third prism patterns extending parallel to one another in the longitudinal direction (or width direction) of the liquid crystal display device 1 are formed. The cross section of the prism pattern formed on the third prism pattern layer 131 may be triangular. For example, the plurality of third prism patterns formed on the third prism pattern layer 131 may be formed with a pitch of pi4 and a height of h4. Here, the plurality of second prism patterns included in the second prism pattern layer 121 and the plurality of third prism patterns included in the third prism pattern layer 131 may be formed to extend in directions perpendicular to each other and have the same pitch and height, but this is not necessarily limited to this and may vary depending on the embodiment.

[0053] According to an embodiment, the second surface 122b of the second base portion 122 of the second sheet 120 may include a first diffusing layer 123, and the second surface 132b of the third base portion 132 of the third sheet 130 may include a second diffusing layer 133. The first diffusing layer 123 and the second diffusing layer 133 may be fabricated using any treatment method to increase turbidity, including a matte treatment that increases turbidity by roughening the first diffusing layer 123 and the second diffusing layer 133, and a bead treatment that increases turbidity using beads of glass, polymer, or the like. For example, in various experimental examples including the viewing angle distribution described below in Figures 8b and subsequent drawings, the first diffusing layer 123 may have a haze value of 3%, and the second diffusing layer 133 may have a haze value of 40%.

[0054] The first sheet 110 and the second sheet 120 may be connected in a laminated form between the pyramid pattern layer 111 of the first sheet 110 and the second sheet 120 (or the first diffusion layer 123 of the second sheet 120), or the second sheet 120 and the third sheet 130 may be connected in a laminated form between the second prism pattern layer 121 of the second sheet 120 and the third sheet 130 (or the second diffusion layer 133 of the third sheet 130). In this case, the first diffusion layer 123 and the second diffusion layer 133 may each be formed, for example, with a matte pattern using an adhesive (e.g., an adhesive resin). Initially, the first diffusion layer 123 and the second diffusion layer 133 may be laminated to another sheet in an approximately 50% cured (e.g., semi-cured) state rather than 100% cured, and then may be laminated to another sheet by being 100% cured.

[0055] 5a shows an experimental setup for measuring the brightness of an optical film according to one embodiment. 5b shows a diagram illustrating the optimal incident angle for enhancing light distribution and brightness according to one embodiment. In FIG. 5b, the viewing angle distribution can represent the distribution of light focused on a horizontal plane (e.g., a plane parallel to the XY plane).

[0056] 5a, an experimental setup for measuring brightness may include an optical film 100 and a light measurement device 210. Here, the optical film 100 may show a state in which a second sheet 120 and a third sheet 130 are laminated together, and the first sheet 110 may be omitted. The light measurement device 210 may be, for example, a high-speed spectroscopic measurement system such as a color luminance meter. Although not shown in the drawing, a backlight unit including a light source may be disposed on the opposite side of the light measurement device 210 relative to the optical film 100.

[0057] As shown in FIG. 5a, the light measurement device 210 can measure light incident in the height direction (Z-axis direction) of the optical film 100. The light distribution can be shown as shown in FIG. 5b using a viewing angle distribution (BSDF, bidirectional scattering distribution function). In this case, to obtain high brightness in the liquid crystal display device 1, the viewing angle data measured by the light measurement device 210 must have high brightness near "0 degrees based on the light measurement device," which is parallel to the Z-axis, the direction in which the light measurement device 210 faces. Experimental results have shown that the brightness near 0 degrees is greatest when light passing through the second sheet 120 and the third sheet 130 in the optical film 100 is incident at a specific angle. That is, the brightness of the liquid crystal display device 1 can be greatest when light passing through the lower surface of the bonded body of the second sheet 120 and the third sheet 130 (e.g., the second surface 122b of the second sheet 120) is incident at a specific incident angle θ. Here, the incident angle θ may refer to the angle formed by the central ray of the light (or light beam) emitted from the first sheet 110, based on the normal line to the second surface 122b of the second sheet 120.

[0058] For example, referring to one embodiment (Example 1-1) of FIG. 5b, in an embodiment in which the second base portion 122 and the third base portion 132 each have a thickness of 24 μm, the pitch pi3 of the prism pattern of the second prism pattern layer 121 formed on the first surface 122a of the second base portion 122 is 50 μm, the height h3 is 25 μm, and the pitch pi3 of the prism pattern of the first prism pattern layer 121 formed on the second surface 122b of the second base portion 122 is 50 μm, the height h3 is 25 μm. has a haze value of 3%, the pitch pi4 of the prism pattern of the third prism pattern layer 131 formed on the first surface 132a of the third base portion 132 is 50 μm, the height h4 is 25 μm, and the second diffusion layer 133 on the second surface 132b of the third base portion 132 has a haze value of 40%, the optimal incident angle θ at which the brightness is highest near 0 degrees as measured by the light measurement device can be formed to be 65 degrees. That is, the light passing through the lower surface of the laminate of the second sheet 120 and the third sheet 130 (for example, the other surface 122b of the second sheet 120) may have the highest brightness value when it is incident at an angle of +65 degrees (or -65 degrees).

[0059] Furthermore, for example, referring to one embodiment (Example 1-2) of FIG. 5b, in an embodiment in which the second base portion 122 and the third base portion 132 each have a thickness of 24 μm, the pitch pi3 of the prism pattern of the second prism pattern layer 121 formed on the first surface 122a of the second base portion 122 is 45 and 55 μm, and the height h3 is 22.5 and 22.7 μm. If the first diffusion layer 123 has a haze value of 15%, the third prism pattern layer 131 formed on the first surface 132a of the third base portion 132 has a prism pattern pitch pi4 of 50 μm and a height h4 of 25 μm, and the second diffusion layer 133 on the second surface 132b of the third base portion 132 has a haze value of 30%, the optimal incident angle θ at which brightness is highest near 0 degrees based on the light measurement device can be formed at 73 degrees. That is, light passing through the lower surface of the laminate of the second sheet 120 and the third sheet 130 (for example, the other surface 122b of the second sheet 120) may have the highest brightness value when incident at an angle of +73 degrees (or -73 degrees).

[0060] In summary, the incident angle θ of light incident on the second sheet 120 can be determined according to the specifications and / or ridge direction (e.g., P2 in FIG. 1 ) of the plurality of second prism patterns of the second prism pattern layer 121 included in the second sheet 120 and the specifications and / or ridge direction (e.g., P3 in FIG. 1 ) of the plurality of third prism patterns of the third prism pattern layer 131 included in the third sheet 130. That is, the incident angle θ can be set in various ways depending on the required specifications of the second sheet 120 and / or the third sheet 130 required for the optical film 100. However, the optical film 100 of the present disclosure includes, based on the first base portion 112, the first prism pattern layer 113 including a prism pattern on its lower surface and the pyramid pattern layer 111 including a pyramid pattern on its upper surface, thereby forming a light path corresponding to the optimal incident angle θ required for the optical film 100 according to some embodiments. As a result, the optical film 100 can have high brightness. 5b, the viewing angle Φ is shown, which may refer to the angle between an imaginary line drawn to one side (e.g., parallel to the X-axis) from the center of the viewing angle distribution shown in FIG. 5b and the central ray of the light (or light beam) exiting the first sheet 110. The viewing angle Φ (phi) is determined by the specifications and / or ridge direction (e.g., P1 in FIG. 1) of the plurality of first prism patterns of the first prism pattern layer 113 of the first sheet 110 of the light incident on the second sheet 120. In the two embodiments (Example 1-1 and Example 1-2) shown in FIG. 5b, the optimal viewing angle Φ is formed at 45 degrees.

[0061] According to various embodiments of the present disclosure, an optical film 100 can be provided that includes a first sheet 110 that is designed to improve the shielding performance in the direction in which light is incident, while allowing light passing through the lower surface of the laminate of the second sheet 120 and the third sheet 130 (e.g., the second surface 122b of the second sheet 120) to be incident at a specific incident light angle θ.

[0062] As shown in FIGS. 1 to 5b, an optical film 100 according to an embodiment includes a first sheet 110 including a first base portion 112, a pyramid pattern layer 111 having a plurality of pyramid patterns formed on a first surface 112a of the first base portion 112, and a first prism pattern layer 113 having a plurality of first prism patterns formed on a second surface 112b of the first base portion 112, and a second base portion 122 and a second prism pattern layer 113 having a plurality of second prism patterns formed on one surface of the second base portion 122. The device may include a second sheet 120 including a second prism pattern layer 121 having a prism pattern formed thereon and a first diffusion layer 123 formed on the second surface 122b of the second base portion 122, and a third sheet 130 arranged over the second sheet 120, the third sheet 130 including a third base portion 132, a third prism pattern layer 131 having a plurality of third prism patterns formed on one surface 132a of the third base portion 132, and a second diffusion layer 133 formed on the second surface 132b of the third base portion 132.

[0063] The liquid crystal display device 1 of Figures 1 to 5b can be manufactured in a form in which the first sheet 110, the second sheet 120, and the third sheet 130 are laminated together. In particular, taking into consideration the specifications of the laminated second sheet 120 and the third sheet 130, by appropriately adjusting the specifications of the pyramid pattern layer 111 formed on the first surface 112a of the first base portion 112 and the first prism pattern layer 113 formed on the second surface 112b, the first sheet 110 can refract and / or reflect light at the point where it abuts the second surface 122b of the second sheet 120 so that the light is incident toward the second sheet 120 at a specific incident light angle θ (improved brightness performance).

[0064] 6a is a diagram showing the appearance of a liquid crystal panel with an arrangement of an inverse prism pattern (first prism pattern layer) and a pyramid pattern according to a certain embodiment. FIG. 6b is a diagram showing the appearance of a liquid crystal panel with an arrangement of an inverse prism pattern (first prism pattern layer) and a pyramid pattern according to one embodiment.

[0065] It is very important that the optical film 100 of FIGS. 1 to 5b has high brightness, but it may also be very important that the moire phenomenon does not occur or is minimized.

[0066] The moire phenomenon will be described in detail below, but the pyramid pattern 111a of the pyramid pattern layer 111 and the prism pattern of the first prism pattern layer 113 (or inverse prism pattern layer) may or may not occur easily by varying the parameter values and / or pattern arrangements.

[0067] 6a and 6b, when the pyramid pattern 111a of the pyramid pattern layer 111 and the prism pattern of the first prism pattern layer 113 are arranged, the moiré phenomenon may or may not occur depending on the difference between the parameter values of the pyramid pattern 111a and the parameter values of the prism pattern (hereinafter referred to as "parameter value difference"). Here, the parameter is, for example, a parameter for length, and the "parameter value difference" may mean, for example, the difference between the pitch of the pyramid pattern and the pitch of the prism pattern.

[0068] According to one embodiment of the present disclosure, the pyramid pattern layer 111 includes a plurality of pyramid patterns 111a having a first pitch pi1, and the first prism pattern layer 113 (or inverse prism pattern layer) includes a plurality of prism patterns having a second pitch pi2. Here, the first pitch pi1 of the pyramid patterns 111a can be defined as the length of the bases a1 and a2. The numerical difference between the patterns can refer to the difference between the first pitch pi1 and the second pitch pi2.

[0069] On the other hand, when one base of the pyramidal pattern 111a is inclined at a predetermined angle (e.g., 30 degrees) or more relative to the ridge direction of the prism pattern, the difference in numerical values of the patterns can be compared based on the first pitch pi1, which is the length of the base of the pyramidal pattern 111a, rather than the first pitch pi1, which is the length of the diagonal of the pyramidal pattern 111a. In the embodiment of Figures 6a and 6b, the phenomenon of moire occurrence can be demonstrated by comparing pi1-1 / 2, which is half the length of the diagonal of the pyramidal pattern 111a, with the prism pattern pitch pi2, rather than comparing the base lengths a1 and a2 of the pyramidal pattern 111a with the prism pattern pitch pi2.

[0070] For example, moiré may occur in the liquid crystal panel 20 shown in FIG. 6a, but not in the liquid crystal panel 20 shown in FIG. 6b. For example, FIG. 6a shows that moiré occurs when the prism pattern pitch pi2 is 21 μm, the pyramid pattern base length is 30 μm, and half the length of the pyramid pattern diagonal is 21.21 μm. Also, FIG. 6b shows that moiré does not occur when the prism pattern pitch pi2 is 13 μm, the pyramid pattern base length is 30 μm, and half the length of the pyramid pattern diagonal is 21.21 μm. This confirms that moiré occurs when a certain parameter of the pyramid pattern (e.g., half the diagonal) is similar to the prism pattern pitch, but does not occur when they are not similar. In some embodiments of the present disclosure, when the pitch of a pyramidal pattern and the pitch of a prism pattern are similar, "similar" means, for example, that the two different pitches have the same value in micrometers (μm) when the decimal point is discarded. Alternatively, "similar" means, for example, that the difference between the two different pitches is less than 3% of the total length of the pitch of a given pattern.

[0071] Fig. 7 is a perspective view showing a liquid crystal display device including an optical film according to an embodiment. Fig. 8a is a diagram showing the arrangement of pyramid patterns and prism patterns according to various embodiments. Fig. 8b is a diagram showing the optical properties of the optical film according to various embodiments. Fig. 9a is a diagram showing the arrangement of pyramid patterns and prism patterns according to various embodiments. Fig. 9b is a diagram showing the optical properties of the optical film according to various embodiments.

[0072] 8a to 9b, various optical properties of the optical film can be seen due to various arrangements of the pyramid patterns 111a of the pyramid pattern layer 111 and the prism patterns of the first prism pattern layer 113. Here, various arrangements of the pyramid patterns and prism patterns may refer to various angle differences between the pyramid patterns and the prism patterns. The various angles between the pyramid patterns and the prism patterns may refer to the angle (hereinafter referred to as "angle α") between one base of the pyramid pattern and the ridge direction (e.g., P1 in FIG. 1) of the prism pattern (e.g., the first prism pattern).

[0073] 8a to 9b, the base length of the pyramid pattern is 30 μm, the pitch of the prism pattern is 21 μm, and the ridge direction of the prism pattern is perpendicular to the arrangement direction of the light sources (e.g., LEDs) (or parallel to the incident direction of light emitted from the light sources (e.g., LEDs)). Simulation results can be shown by changing the angle difference between the pyramid pattern and the prism pattern. In FIGS. 8b and 9b, viewing angle distribution 1 represents the optical characteristics of light measured between the first sheet 110 and the second sheet 120, as shown in FIG. 7, and viewing angle distribution 2 represents the optical characteristics of light measured between the third sheet 130 and the diffusion sheet 17.

[0074] 8a and 8b, when the angle α (alpha) between one base of the pyramid pattern 111a and the ridge direction of the prism pattern (indicated by the arrow) is 90 degrees, the brightness is 63.2%, when the angle α is 75 degrees, the brightness is 73.4%, and when the angle α is 60 degrees, the brightness is 91.7%. On the other hand, when the angle α between one base of the pyramid pattern 111a and the ridge direction of the prism pattern (indicated by the arrow) is 45 degrees, the brightness is 100.0%. And, when the angle α between one base of the pyramid pattern 111a and the ridge direction of the prism pattern (indicated by the arrow) is 30 degrees, the brightness is 90.3%, when the angle α is 15 degrees, the brightness is 74.4%, and when the angle α is 0 degrees, the brightness is 64.4%. As mentioned above, it can be seen that, all other conditions being equal, the brightness value according to the angle α between the patterns has a maximum value at an angle of 45 degrees when going from 90 degrees to 0 degrees.

[0075] 8a to 9b, it can be seen that the highest brightness value can be obtained when the angle α between one base side of the pyramid pattern 111a and the ridge direction of the prism pattern is 45 degrees between the pyramid pattern 111a of the pyramid pattern layer 111 and the prism pattern of the first prism pattern layer 113. From another perspective, it can also be considered that the highest brightness value can be obtained when the direction of the diagonal length of the pyramid pattern 111a of the pyramid pattern layer 111 and the ridge direction of the prism pattern are perpendicular to each other.

[0076] 10a and 10b show moiré simulation results according to various embodiments.

[0077] 10a and 10b show moiré simulation results for an optical film depending on the angle (interval angle, α) between the pyramid patterns 111a of the pyramid pattern layer 111 and the prism patterns of the first prism pattern layer 113. FIG. 10a shows the extent of moiré occurrence at various angles (interval angles, α) when the base length of the pyramid patterns 111a of the pyramid pattern layer 111 is 30 μm and the pitch of the prism patterns of the first prism pattern layer 113 is 21 μm. FIG. 10b shows the extent of moiré occurrence at various angles (interval angles, α) when the base length of the pyramid patterns 111a of the pyramid pattern layer 111 is 30 μm and the pitch of the prism patterns of the first prism pattern layer 113 is 30 μm. Here, the moiré can be observed on the liquid crystal panel 20 of FIG. 1.

[0078] When the pyramid patterns 111a of the pyramid pattern layer 111 and the prism patterns of the first prism pattern layer 113 have mutual angles α of 0 degrees, 15 degrees, 30 degrees, 40 degrees, 45 degrees, 50 degrees, 60 degrees, 75 degrees, and 90 degrees, as shown in FIG. 10a, the degree of moiré occurrence is greatest at 45 degrees. It is also observed that some moiré occurs at angles of 40 degrees and 50 degrees near 45 degrees. As shown in FIG. 10b, the degree of moiré occurrence is greatest at 0 degrees and 90 degrees. Unlike FIG. 10a, it is also observed that no moiré occurs at 45 degrees in FIG. 10b.

[0079] As can be seen from the embodiment of Figures 10a and 10b, for example, when the angle α between one base of the pyramid pattern 111a and the ridge direction of the prism pattern (indicated by the arrow) is 0 degrees, 45 degrees, or 90 degrees, moire may occur depending on the relationship between the length of the base and / or diagonal of the pyramid pattern and the pitch of the prism pattern.

[0080] For example, if the length of one base of the pyramid pattern 111a is similar to the pitch of the prism pattern, moiré may occur when the angle α between one base of the pyramid pattern 111a and the ridge direction of the prism pattern is 0 degrees or 90 degrees. Also, if half the length of the diagonal of the pyramid pattern 111a is similar to the pitch of the prism pattern, moiré may occur when the angle α between one base of the pyramid pattern 111a and the ridge direction of the prism pattern is 45 degrees.

[0081] In order to provide an optical film that has high brightness characteristics and does not cause moire, the angle between the pyramid pattern and the prism pattern must be considered in the design, along with the numerical relationship of the parameters.

[0082] Hereinafter, with reference to FIGS. 11a to 11d, the conditions for the spacing angle and pitch length for providing an optical film that has high brightness characteristics and does not cause the moire phenomenon will be described in more detail.

[0083] Figure 11a is a diagram illustrating an arrangement of a pyramid pattern and a prism pattern according to one embodiment, Figure 11b is a diagram illustrating an arrangement of a pyramid pattern and a prism pattern according to one embodiment, Figure 11c is a diagram illustrating an arrangement of a pyramid pattern and a prism pattern according to one embodiment, and Figure 11d is a diagram illustrating an arrangement of a pyramid pattern and a prism pattern according to one embodiment.

[0084] 11a to 11d show the positional relationship between the pyramid pattern 111a of the pyramid pattern layer 111 and the prism pattern of the first prism pattern layer 113. The angle between a base of the pyramid pattern 111a and the prism pattern may be varied while one vertex v1 of the pyramid pattern 111a is fixed to the edge of the prism pattern. Fig. 11a shows the case where the angle α between the base of the pyramid pattern 111a and the prism pattern is 0 degrees. Fig. 11b shows the case where the angle α between the base of the pyramid pattern 111a and the prism pattern is 10 degrees. Fig. 11c shows the case where the angle α between the base of the pyramid pattern 111a and the prism pattern is 20 degrees. Fig. 11d shows the case where the angle α between the base of the pyramid pattern 111a and the prism pattern is 45 degrees. 11a to 11d show a pyramid pattern 111a including four side surfaces 111-1, 111-2, 111-3, and 111-4 and four corresponding base surfaces 111-1', 111-2', 111-3', and 111-4'. The second base surface 111-2' of the pyramid pattern 111a can be used as a reference for the angle between the pyramid pattern and the prism pattern, but this is merely an example, and other base surfaces (e.g., the first base surface 111-1', the third base surface 111-3', and the fourth base surface 111-4') can also be used.

[0085] In the present disclosure, the pyramidal pattern 111a may have a square bottom. For example, the four bases 111-1', 111-2', 111-3', and 111-4' may have substantially the same length. Here, the expression "having substantially the same length" may mean that the lengths are the same as each other within a predetermined error range.

[0086] 11a to 11d, the dominant pitch of the pyramidal pattern 111a, which affects the moiré phenomenon, may change as the angle between one base side of the pyramidal pattern 111a and the prism pattern changes. Here, the dominant pitch may refer to the pitch that has the greater effect on the moiré phenomenon between the first pitch pi1 corresponding to the length of the base side of the pyramidal pattern 111a and the 1-1 pitch pi1-1 corresponding to the length of the diagonal of the pyramidal pattern 111a. For example, referring to FIG. 11a, when the angle α between one base side of the pyramidal pattern 111a and the prism pattern is 0 degrees, the first pitch pi1 corresponding to the length of the base side (e.g., the fourth base side 111-4') of the pyramidal pattern 111a may be the dominant pitch x1. The first pitch pi1 remains dominant until the angle α between one base of the pyramid pattern 111a and the prism pattern reaches a predetermined angle (e.g., less than about 10 degrees). If the angle difference is greater than this, the first pitch pi1-1, which corresponds to the length of the diagonal of the pyramid pattern 111a, may become the dominant pitch. Referring to FIG. 11b, when the angle α between one base of the pyramid pattern 111a and the prism pattern is 10 degrees, the first pitch pi1-1, which corresponds to the length of the diagonal of the pyramid pattern 111a, may become the dominant pitch x2. Referring to FIG. 11c, when the angle α between one base of the pyramid pattern 111a and the prism pattern is 20 degrees, the first pitch pi1-1, which corresponds to the length of the diagonal of the pyramid pattern 111a, may become the dominant pitch x3. Referring to FIG. 11d, when the angle α between one base side of the pyramid pattern 111a and the prism pattern is 45 degrees, the 1-1 pitch pi1-1 corresponding to the length of the diagonal of the pyramid pattern 111a can be the dominant pitch x4.

[0087] 10a and 10b, when the length of one base of the pyramid pattern 111a is similar to the pitch of the prism pattern, moiré may occur when the angle α between one base of the pyramid pattern 111a and the ridge direction of the prism pattern is 0 degrees or 90 degrees. Furthermore, when, for example, half the length of the diagonal of the pyramid pattern 111a is similar to the pitch of the prism pattern, moiré may occur when the angle α between one base of the pyramid pattern 111a and the ridge direction of the prism pattern is 45 degrees. Referring again to FIG. 11a, when the angle α between one base of the pyramid pattern 111a and the ridge direction of the prism pattern is 0 degrees or 90 degrees, the first pitch pi1 corresponding to the length of one base of the pyramid pattern 111a becomes the dominant pitch x1, and when this is similar to the second pitch pi2 of the prism pattern, moiré may occur. 11b to 11d, if the angle α between one base of the pyramidal pattern 111a and the ridge direction of the prism pattern is not 0 degrees or 90 degrees (for example, 10 degrees to 80 degrees), the first-first pitch pi1-1 corresponding to the length of one base of the pyramidal pattern 111a becomes the dominant pitch x2, x3, x4, and if half of this pitch is similar to the second pitch pi2 of the prism pattern, moire may occur. The pitch relationship that prevents moire from occurring in the optical film 100 can be expressed mathematically as follows: In order for moire to not occur in the optical film 100, the following mathematical formula 1 or 2 must be satisfied.

[0088]

number

[0089]

number

[0090] Moire will not occur unless the second pitch pi2 is a multiple of (pi1-1) / 2 or a multiple of pi1, so in the above equations 1 and 2, the (pi1-1) / 2 value and the value multiplied by n by pi1 are applied.

[0091] 11b, when the angle α between one base of the pyramidal pattern 111a and the ridge direction of the prism pattern is a predetermined angle (for example, 10 degrees or more), the first-first pitch pi1-1 corresponding to the length of the diagonal of the pyramidal pattern 111a becomes the dominant pitch, and moiré may not occur unless half of this value (pi1-1) / 2 matches the second pitch pi2. Generalizing Figures 11b to 11d using the illustration in Figure 11b, we obtain the following equation. To prevent moiré from occurring in the optical film 100, the following equation 3 must be satisfied:

[0092]

number

[0093] Moiré will not occur unless the second pitch pi2 matches a multiple of (pi1(sinα+cosα)) / 2, so in the above equation 3, the value n times the (pi1(sinα+cosα)) / 2 value is applied.

[0094] In addition to the condition for preventing moire, referring to FIGS. 8b and 9b, the optical film 100 can satisfy the following formula 4 to exhibit high brightness of 90% or more.

[0095]

number

[0096] FIG. 12 is a diagram comparing raised and recessed pyramid patterns, according to one embodiment.

[0097] According to various embodiments of the present disclosure, the pyramidal patterns 111a of the pyramidal pattern layer 111 can be formed by intaglio engraving.

[0098] Referring to FIG. 12, the difference in luminance value, incident angle θ, and viewing angle Φ for the combination of the recessed pyramid pattern and the inverted prism pattern can be considered compared to the combination of the raised pyramid pattern and the inverted prism pattern.

[0099] Compared with the combination of a embossed pyramid pattern and an inverted prism pattern, the combination of a recessed pyramid pattern and an inverted prism pattern has a higher light collecting efficiency, thereby resulting in a higher brightness value. The incident angle and viewing angle of the combination of a recessed pyramid pattern and an inverted prism pattern are narrower than those of the combination of a embossed pyramid pattern and an inverted prism pattern, which can be interpreted as the incident angle and viewing angle being shifted to the center, resulting in a higher light collecting efficiency.

[0100] Furthermore, in the case of a raised pyramid pattern, the peak portions (e.g., partitions 111-5, 111-6 in Figure 4e) are physically vulnerable to damage, so applying a recessed pyramid pattern may be more advantageous than applying a raised pyramid pattern.

[0101] According to one embodiment, the engraved pyramid pattern applied in the present disclosure may be referred to as a "waffle-type pyramid pattern."

[0102] FIG. 13 is a diagram showing optical characteristics according to various embodiments, based on the refractive index of the pyramid pattern layer (hereinafter abbreviated as "pyramid refractive index") and the refractive index of the inverse prism pattern layer (hereinafter abbreviated as "inverse prism refractive index").

[0103] In FIG. 13, the alphabet n representing the refractive index can be shown in front of the numbers.

[0104] According to one embodiment, in consideration of brightness and color coordinates, it may be advantageous for the refractive index of the pyramid pattern 111a of the pyramid pattern layer 111 and the refractive index of the prism pattern (inverse prism pattern) of the first prism pattern layer 113 to have a smaller refractive index than that of the first base portion 112.

[0105] 13, for example, when the refractive index (PET refractive index) of the base portion 112 of the first sheet 110 is 1.65, if the refractive index (hereinafter abbreviated as "inverse prism refractive index") of the prism pattern (inverse prism pattern) of the first prism pattern layer 113 is fixed at 1.49, and the refractive index (hereinafter abbreviated as "pyramid refractive index") of the pyramid pattern 111a of the pyramid pattern layer 111 is sequentially changed from 1.49 to 1.58 and then to 1.69, a change in optical characteristics may occur. Here, the change in optical characteristics refers to, for example, the viewing angle distribution, luminance, color coordinate (e.g., Δy), incident angle θ, and viewing angle Φ, but for convenience, the description will focus on the change in luminance value.

[0106] 13, when the refractive index of the base portion 112 (PET refractive index) is 1.65 and the refractive index of the inverse prism is fixed at a low refractive index (e.g., an inverse prism refractive index of 1.49), a comparison of an embodiment in which the pyramid refractive index is 1.49 (e.g., Example 2-1), an embodiment in which the pyramid refractive index is 1.58 (e.g., Example 2-2), and an embodiment in which the pyramid refractive index is 1.69 (e.g., Example 2-3) reveals a change in luminance. For example, when the refractive index of the pyramid is close to or greater than the refractive index of the base portion 112 (e.g., 1.69) (i.e., the pyramid refractive index is higher than the refractive index of the base portion (e.g., Example 2-3)), it can be seen that the luminance value is significantly lower than when the pyramid refractive index is 1.49 or 1.58 (i.e., the pyramid refractive index is lower than the refractive index of the base portion (e.g., Examples 2-1, 2-2, and 2-4)).

[0107] Referring to another embodiment (e.g., Example 2-4) of Figure 13, when the refractive index of the base portion 112 (PET refractive index) is 1.65, even if the pyramid refractive index is 1.49, which is a low refractive index, it can be confirmed that a decrease in brightness occurs even when the refractive index of the inverted prism is close to or has a larger value (e.g., 1.69) than the refractive index of the base portion 112 (i.e., when the refractive index of the inverted prism is higher than the refractive index of the base portion).

[0108] 13, when the refractive index of the inverted prism and the refractive index of the pyramid are each smaller than the refractive index of the base portion (e.g., Examples 2-1 and 2-2), a high brightness value can be obtained, but when at least one of the refractive index of the inverted prism and the refractive index of the pyramid is higher than the refractive index of the PET (e.g., Examples 2-3 and 2-4), the brightness value is not as high as when the refractive index of the inverted prism and the refractive index of the pyramid are each smaller than the refractive index of the base portion (e.g., Examples 2-1 and 2-2). In summary, the present disclosure can be applied to embodiments in which both the refractive index of the inverted prism and the refractive index of the pyramid are formed lower than the refractive index of the base portion.

[0109] 13 are merely illustrative, except for the characteristics of the magnitude relationship among the refractive index of the base portion (PET refractive index), the pyramid refractive index, and the prism refractive index, which are factors that cause the deterioration of the optical properties. Therefore, the values of the refractive index of the base portion (PET refractive index), the pyramid refractive index, and the prism refractive index may be partially changed depending on the embodiment.

[0110] According to one embodiment of the present disclosure, an optical film may include a first sheet including a first base portion, a pyramid pattern layer having a plurality of pyramid patterns with a first pitch pi1 formed on a first surface of the first base portion, and a first prism pattern layer having a plurality of prism patterns with a second pitch pi2 formed on a second surface of the first base portion. When the lengths of the diagonals of the pyramid patterns have a pitch pi1-1 of 1-1, the optical film may satisfy the following formula 1 or 2:

[0111]

number

[0112]

number

[0113] According to one embodiment, the optical film can satisfy the following formula 3 regarding the angle α between one base side of the pyramid pattern and the ridge direction of the prism pattern.

[0114]

number

[0115] According to one embodiment, the optical film can satisfy the following formula 4 with respect to the angle α between one base of the pyramid pattern and the ridge direction of the prism pattern.

[0116]

number

[0117] According to one embodiment, the plurality of pyramid patterns may be formed by intaglio engraving.

[0118] According to one embodiment, the device may further include a second base portion, a second prism pattern layer having a plurality of prism patterns formed on a first surface of the second base portion, and a second sheet disposed over the first sheet.

[0119] According to one embodiment, the second sheet includes a first diffusion layer formed on the second surface of the second base portion, and the first diffusion layer can face the pyramid pattern layer.

[0120] According to one embodiment, the device may further include a third base portion, a third prism pattern layer having a plurality of prism patterns formed on a first surface of the third base portion, and a third sheet disposed over the second sheet.

[0121] According to one embodiment, the third sheet includes a second diffusing layer formed on a second surface of the third base portion, and the second diffusing layer can face the second prism pattern layer.

[0122] According to one embodiment, the plurality of first prism patterns may form crests in a third direction, the plurality of second prism patterns may form crests in a fourth direction, and the plurality of third prism patterns may form crests in a fifth direction perpendicular to the fourth direction.

[0123] According to an embodiment, the refractive index of the pyramid pattern layer and the refractive index of the first prism pattern layer may each be smaller than the refractive index of the base portion.

[0124] A backlight unit including the optical film according to the above-described embodiments may include an edge-type light source and the optical film disposed over the light source.

[0125] According to one embodiment, the edge-type light source may be arranged in a sixth direction perpendicular to the third direction and configured to emit light in a direction parallel to the third direction.

[0126] The optical films of the various embodiments of the present disclosure and the backlight units including the same described above are not limited to the above-described embodiments and drawings, and it will be apparent to those skilled in the art to which the present invention pertains that various substitutions, modifications, and alterations are possible within the technical scope of the present disclosure. [Explanation of symbols]

[0127] LCD display: 1 Backlight units: 10 Light source: 11 Light guide plate: 12 Reflector: 13 Diffusion sheet: 17 LCD panel: 20 Optical film: 100 1st sheet: 110 Pyramid Pattern Layers: 111 First base: 112 First prism pattern layer: 113 Second sheet: 120 Second prism pattern layer: 121 Second base: 122 First diffusion layer: 123 Third seat: 130 Third prism pattern layer: 131 Third base: 132 Second diffusion layer: 133

Claims

1. In optical films, a first base portion; a pyramid pattern layer in which a plurality of pyramid patterns having a first pitch pi1 are formed on a first surface of the first base portion; and a first sheet including a first prism pattern layer on a second surface of the first base portion, the first prism pattern layer having a plurality of prism patterns having a second pitch pi2 formed thereon; When the length of the diagonal line of the pyramidal pattern has a 1-1 pitch pi1-1, the optical film satisfies the following formula 1 or 2: [Equation 1] [Equation 2] (where n is a natural number)

2. The optical film according to claim 1 , wherein an angle α between one base of the pyramid pattern and a ridge direction of the prism pattern satisfies the following formula 3: [Equation 3] (where n is a natural number)

3. The optical film according to claim 2 , wherein an angle α between one base of the pyramid pattern and a ridge direction of the prism pattern satisfies the following formula 4: [Equation 4]

4. The optical film according to claim 1 , wherein the plurality of pyramid patterns are formed by intaglio engraving.

5. 2. The optical film of claim 1, further comprising a second sheet including a second base portion and a second prism pattern layer having a plurality of prism patterns formed on a first surface of the second base portion, the second sheet being superimposed over the first sheet.

6. The optical film of claim 5 , wherein the second sheet includes a first diffusing layer formed on the second surface of the second base portion, the first diffusing layer facing the pyramid pattern layer.

7. 6. The optical film according to claim 5, further comprising a third sheet including a third base portion and a third prism pattern layer having a plurality of prism patterns formed on a first surface of the third base portion, the third sheet being superimposed on the second sheet.

8. The optical film of claim 7 , wherein the third sheet includes a second diffusing layer formed on the second surface of the third base portion, the second diffusing layer facing the second prism pattern layer.

9. the plurality of first prism patterns form a crest in a third direction; the plurality of second prism patterns form ridges extending in a fourth direction; The optical film according to claim 7 , wherein ridge lines of the plurality of third prism patterns form ridge lines in a fifth direction perpendicular to the fourth direction.

10. The optical film according to claim 1 , wherein the refractive index of the pyramid pattern layer and the refractive index of the first prism pattern layer are each smaller than the refractive index of the first base portion.

11. A backlight unit comprising the optical film according to any one of claims 1 to 10, Edge-type light sources, and a backlight unit including the optical film disposed over the light source;

12. The backlight unit according to claim 11 , wherein the edge-type light source is arranged in a sixth direction perpendicular to the third direction and is configured to emit light in a direction parallel to the third direction.

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