Optical film and backlight unit including same

Abstract

The present disclosure provides an optical film and a backlight unit including the same. An optical film according to various embodiments of the present disclosure may include: a specific diffusion sheet including a first pattern forming a reference direction, the reference direction being an extending direction of the first pattern; a third sheet spaced apart from the specific diffusion sheet and including a third pattern extending in a third pattern direction; and a second sheet disposed between the specific diffusion sheet and the third sheet and including a second pattern extending in a second pattern direction, at least one of the second pattern and the third pattern being tiltable with respect to the reference direction, the third pattern forms an included angle in a range of-30 degrees to + 30 degrees with respect to the reference direction.

Description

Technical Field

[0001] Embodiments of the present disclosure relate to an optical film for a liquid crystal display device and a backlight unit including the same. Background Art

[0002] Generally, a liquid crystal display (LCD) may include a backlight unit that uniformly irradiates light onto 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 prisms. Light emitted from the light source may be transmitted upward through the light guide plate, and the light transmitted upward may be diffused by the diffusion sheet and then transmitted to the liquid crystal panel through the optical film provided on the upper portion.

[0003] Recently developed display devices are getting thinner and thinner, so the backlight unit is also required to be manufactured in a thinner form. Currently, research and development are underway to remove relatively thick diffusion sheets from the backlight unit. For example, in an embodiment of a backlight unit including a light source, a light guide plate, a diffusion sheet, and a prism sheet, research and development are underway to remove or replace the diffusion sheet.

[0004] The diffusion sheet may form a diffusion layer on one surface and / or the other surface. The diffusion layer generally includes light diffusing agent microspheres, which can diffuse light to a wider range when the light provided from the light source and the light guide plate is directed toward the prism sheet, and at the same time can also act as a light shielding sheet for reducing the visibility of the light source. The diffusion sheet generally has problems such as a relatively thick thickness and affecting the brightness improvement of the backlight unit, so efforts are being made to find alternatives to it.

[0005] For example, in the invention with the publication number CN119225071A, by using a sheet including a pyramid pattern and an inverse prism pattern to replace the diffusion sheet, the thickness of the backlight unit can be reduced and the brightness can be improved.

[0006] However, when using a sheet including a pyramid pattern and an inverse prism pattern to replace the diffusion sheet, a Moiré phenomenon may occur due to the arrangement of the pyramid pattern and the inverse prism pattern. Summary of the Invention

[0007] The present disclosure aims to provide, through various embodiments, an optical film for a liquid crystal display device, which can effectively prevent the shape of the light source from being visible (hereinafter referred to as "light shielding performance") without using a thick diffusion sheet, while achieving high brightness (hereinafter referred to as "brightness performance"). In addition, various embodiments of an optical film that can effectively avoid the Moiré phenomenon when using a sheet including a pyramid pattern and an inverse prism pattern to replace the diffusion sheet can be provided.

[0008] Optical films according to various embodiments of the present disclosure may include: a specific diffusion sheet including a first pattern forming a reference direction, which is an extending direction of the first pattern; a third sheet spaced apart from the specific diffusion sheet and including a third pattern extending in a third pattern direction; and a second sheet disposed between the specific diffusion sheet and the third sheet and including a second pattern extending in a second pattern direction, wherein at least one of the second pattern and the third pattern may be inclined with respect to the reference direction, and the third pattern forms an included angle within a range of -30 degrees to +30 degrees with respect to the reference direction.

[0009] According to various embodiments of the present disclosure, an optical film capable of reducing and / or preventing a moiré phenomenon and a backlight unit including the optical film may be provided.

[0010] According to various embodiments of the present disclosure, by removing a thick diffusion sheet, thinning of the backlight unit may be promoted.

[0011] According to various embodiments of the present disclosure, an optical film having excellent light source shielding performance and brightness performance and a backlight unit including the optical film may be provided.

[0012] The effects achievable in the present disclosure are not limited to the above effects, and other effects not mentioned may be clearly understood by those of ordinary skill in the art to which the present disclosure pertains based on the following. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Through the following detailed description with reference to the accompanying drawings, the above aspects or other aspects, configurations, and / or advantages of the embodiments of the present disclosure will become more apparent.

[0014] Figure 1 is a perspective view of a liquid crystal display device including an optical film according to an embodiment; Figure 2 is a schematic view of a liquid crystal display device including an optical film according to an embodiment; Figure 3 is a schematic view of a liquid crystal display device including an optical film according to an embodiment; Figure 4 is a cross-sectional view of an optical film according to an embodiment; Figure 5 is a perspective view of a liquid crystal display device including an optical film according to an embodiment; Figure 6 is a schematic view for explaining an angle between members included in an optical film; Figure 7 is a schematic view for explaining an effect of an optical film according to an embodiment of the present disclosure; and Figure 8 is a schematic view for explaining an effect of an optical film according to an embodiment of the present disclosure. Detailed implementation mode

[0015] Figure 1 is a perspective view of a liquid crystal display device including an optical film according to an embodiment.

[0016] In the following detailed description, the length direction (longitudinal direction) of the liquid crystal display device 1 may be defined as the "Y-axis direction", the width direction (lateral direction) may be defined as the "X-axis direction", and / or the height direction (thickness direction) may be defined as the "Z-axis direction". In addition, in some embodiments, regarding the direction of the component orientation, in addition to the rectangular coordinate system exemplified in the drawings, "negative / positive (- / +) " may also be marked simultaneously. As Figure 1 shown, when "negative / positive (- / +) " is not marked in the rectangular coordinate system, unless otherwise defined, it should be interpreted that the coordinate axis points to the + direction. For example, the "X-axis direction" should be interpreted as pointing to the +X axis direction, the "Y-axis direction" should be interpreted as pointing to the +Y axis direction, and the "Z-axis direction" should be interpreted as pointing to the +Z axis direction. For example, referring to Figure 1 , when the second sheet 120 is disposed above a specific diffusion sheet 110, it may be defined that the second sheet 120 is disposed along the "+Z-axis direction" starting from the specific diffusion sheet 110. Another example, referring to Figure 4 , one surface (for example: the first surface 112a) of the first base portion 112 may be defined as the "surface facing the +Z-axis direction", and the other surface (for example: the second surface 112b) may be defined as the "surface facing the -Z-axis direction". According to an embodiment, in the description of the optical film 100, the traveling direction of the light source may be expressed as the "+Z-axis direction". When describing the direction below, "pointing to any one of the three axes of the rectangular coordinate system" may include a direction parallel to that axis. It should be noted that for the sake of simplicity of description, this document is based on the illustrated rectangular coordinate system, and the description of such a direction or component will not limit the various embodiments of the present disclosure.

[0017] Referring to Figure 1 , the liquid crystal display device (or LCD device) 1 may include a backlight unit 10 and a liquid crystal panel 20. According to various embodiments, the backlight unit 10 may be disposed opposite to the back surface (the surface facing the -Z-axis direction) of the liquid crystal panel 20 to irradiate 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 marked in the figure, the backlight unit 10 may further include a reflective polarizer.

[0018] The light source 11 is a component that emits light to the back surface of the liquid crystal panel 20, and it may be disposed at one side of the light guide plate 12 (LPG). According to the arrangement structure, the light source can be divided into an edge type or a direct-lit type, as Figure 1As shown, an edge-type light source can be adopted in the present disclosure. The light source 11 is a component that irradiates light onto the back surface of the liquid crystal panel 20, and the light emitted from the light source 11 can be converted into a surface light source form through the light guide plate 12. At this time, the light source 11 can adopt a light-emitting diode (LED), 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 by reflecting the light emitted toward the rear of the light guide plate 12 (the surface facing the -Z axis direction) and making it incident on the light guide plate 12, light loss can be minimized. That is, the reflector 13 can play a role in light recycling.

[0019] Referring to Figure 1 , the light emitted from the light guide plate 12 is incident on the optical film 100. The optical film 100 of the present disclosure includes at least one prism sheet for condensing light, and as a sheet that minimizes the brightness loss of the incident light from the light guide plate 12 and uniformly disperses it before being incident on the prism sheet, it may also include a sheet having an inverse prism pattern. For ease of explanation, hereinafter, the combination of one or more prism sheets for condensing light included in the optical film 100 will be referred to as "condensing prism sheets 120, 130", and the sheet having an inverse prism pattern will be referred to as "specific diffusion sheet 110".

[0020] As described below, the optical film 100 of the present disclosure may include a specific diffusion sheet 110, which has an inverse prism pattern formed on one surface facing the direction opposite to the light source traveling direction (e.g., the Z axis direction), and a pyramid pattern (or diffusion sheet) formed on the other surface facing the light source traveling direction. In addition, the optical film 100 of the present disclosure may include a second sheet 120, which has a prism pattern formed on one surface parallel to the light source traveling direction (e.g., the +Z axis direction). According to an embodiment, the second sheet 120 may also have a diffusion layer formed on the other surface facing the direction opposite to the light source traveling direction. According to an embodiment, in addition to the second sheet 120, the optical film 100 of the present disclosure may also include a third sheet 130, which includes a prism pattern having a ridge line direction different from that of the prism pattern formed on the second sheet 120. According to an embodiment, the third sheet 130 may also have a diffusion layer formed on the other surface facing the direction opposite to the light source traveling direction.

[0021] The condenser prism sheets 120 and 130 can condense incident light by using an optical pattern formed on the surface and then emit it toward the liquid crystal panel 20. The condenser prism sheets 120 and 130 may include a light-transmitting substrate film and a prism pattern layer formed on the upper surface (the surface facing the +Z-axis direction) of the substrate film. To enhance the brightness in the plane direction, the prism pattern layer may be formed as a triangular array optical pattern layer having inclined surfaces with a specified angle (e.g., an inclined surface of 45°). The prism patterns of the prism pattern layer may be in the shape of triangular prisms, and one surface of the triangular prism shape may be disposed opposite to the substrate film. The cross-section of each prism pattern may be triangular.

[0022] According to an embodiment, the third sheet 130 may overlap above the second sheet 120. In the second sheet 120, a plurality of second prism patterns may be arranged parallel to each other. Each second prism pattern may be a structure extending in one direction. For example, the connecting line of the vertices of each second prism pattern (hereinafter referred to as the "ridge line") may be formed to extend in the X-axis direction. Similarly, in the third sheet 130, a plurality of third prism patterns may also be arranged parallel to each other. Each third prism pattern may be a structure extending in one direction. For example, the ridge line of each third prism pattern may be formed to extend in the Y-axis direction perpendicular to the X-axis. For ease of explanation, the extending directions of the second prism pattern and the third prism pattern are respectively marked as the X-axis direction and the Y-axis direction in the figure. However, it should be noted that this is not limited to the illustrated embodiment and may also be in other directions other than the X-axis or the Y-axis.

[0023] According to an embodiment, an inverse prism pattern (a plurality of first prism patterns) may be formed in the specific diffuser sheet 110. Different from 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 specific diffuser sheet 110 are not formed in a direction parallel to the light traveling direction (+Z-axis direction), but protrude in the reverse direction (-Z-axis direction) with respect to the light traveling direction. The ridge line direction P1 of the plurality of first prism patterns (hereinafter may be referred to as the "third direction") may be formed to be the same as or different from the ridge line direction P2 of the plurality of second prism patterns (hereinafter may be referred to as the "fourth direction") and the ridge line direction P3 of the plurality of third prism patterns (hereinafter may be referred to as the "fifth direction"). According to an embodiment, as Figure 1 shown, the ridge line direction P1 of the plurality of first prism patterns may be formed to be orthogonal to the ridge line direction P2 of the plurality of second prism patterns and parallel to the ridge line direction P3 of the plurality of third prism patterns, and the liquid crystal display device 1 of the present disclosure can thus obtain corresponding effects. The ridge line direction will be described in detail later.

[0024] The diffusion sheet 17 can evenly disperse the light incident from the optical film 100. The diffusion sheet 17 can induce light diffusion by using light diffusing agent microspheres through coating a solution of a curable resin (at least one or a combination of polyurethane acrylate, epoxy acrylate, ester acrylate, and a radical generating monomer) added with the light diffusing agent microspheres. In addition, the diffusion sheet 17 can also promote light diffusion by forming a convex pattern (or convex portion) having a shape with uniform or non-uniform sizes (e.g., spherical, hemispherical, or elliptical). According to certain embodiments of the prior art, the diffusion sheet 17 may include not only Figure 1 the upper diffusion sheet 17 disposed above the condenser prism sheet as shown, but may also include a lower diffusion sheet disposed below the condenser prism sheet. However, in the present disclosure, by providing the optical film 100 that combines the condenser prism sheet and a specific diffusion sheet, the lower diffusion sheet can be replaced.

[0025] According to an embodiment, the backlight unit 10 may omit at least one of the above components (e.g., the diffusion sheet 17), or add one or more other components (e.g., a reflective polarizing sheet (not shown)).

[0026] The reflective polarizing sheet (not shown) may be disposed on the upper portion of the optical film 100 and the diffusion sheet 17, and may perform the function of transmitting partial polarized light and reflecting other polarized light downward for the light condensed by the optical film 100 and diffused by the upper diffusion sheet.

[0027] The liquid crystal panel 20 can refract the light emitted from the light source 11 into a predetermined pattern according to an electrical signal. The refracted light can pass through a color filter and a polarizing filter disposed on the front surface of the liquid crystal panel 20 and form an image.

[0028] Included in Figure 1 the components shown in the liquid crystal display device 1 can be assembled in a state of overlapping and stacking with other components in the height direction (+Z-axis direction). For example, as Figure 1 shown, in the liquid crystal display device 1 according to an embodiment, the separately manufactured backlight unit 10 and the liquid crystal panel 20 can be overlapped and stacked in the height direction (+Z-axis direction).

[0029] Figure 2 is a schematic diagram of a liquid crystal display device including an optical film according to an embodiment. Figure 3 is a schematic diagram of a liquid crystal display device including an optical film according to an embodiment.

[0030] Figure 2 can show a cross-section parallel to the plane formed by the Y-axis and the Z-axis of the liquid crystal display device 1, and Figure 3 can show a cross-section parallel to the plane formed by the X-axis and the Z-axis. The following will omit the description of the parts that repeat the description content. Figure 1 ​

[0031] The liquid crystal display device 1 of the present disclosure may be characterized in that a diffusion sheet (e.g., a lower diffusion sheet) is not separately provided between the optical film 100 and the light guide plate 12, but only the optical film 100 of the present disclosure substitutes for the diffusion sheet.

[0032] In the present disclosure, the "optical film 100" may refer to, as Figures 1 to 3 shown, a film including a specific diffusion sheet 110 having a plurality of reverse prism patterns formed on one surface, a second sheet 120 provided on the specific diffusion sheet 110 and having a plurality of prism patterns formed on one surface, and a third sheet 130 provided on the second sheet 120 and having a plurality of prism patterns formed on one surface. In Figures 1 to 3 order to facilitate explanation, the specific diffusion sheet 110, the second sheet 120, and the third sheet 130 are shown spaced apart from each other, but differently, the specific diffusion sheet 110, the second sheet 120, and the third sheet 130 may be formed by laminating each other. In the present disclosure, "lamination" may refer to including a pattern formed of a viscous resin on at least one of the opposite surfaces of two different sheets, thereby joining the two different sheets. For example, there is a pattern formed of a viscous resin in a semi-cured state on one of the opposite surfaces of two different sheets, and in a state where the other surface is brought into contact with the pattern, they are joined after being completely cured. In addition, for example, both of the opposite surfaces of two different sheets are formed of a viscous resin in a semi-cured state, and after being brought into contact with each other, they are joined after being completely cured. Compared with an embodiment of a simple lamination rather than a laminated form, the laminated optical film 100 may be thinner and may provide a backlight unit having excellent light-shielding performance.

[0033] The inverse prism pattern of the specific diffusion sheet 110 performs a light condensing function, and the upper pyramid pattern performs a light shielding function. Meanwhile, when a diffusion pattern is used to replace the pyramid pattern, compared with the pyramid pattern, the brightness can be improved while maintaining the same light shielding performance. The second sheet 120 can be formed in a shape in which a plurality of prisms (or triangular prisms) extend in the width direction (X-axis direction) of the liquid crystal display device 1 and protrude in the height direction (Z-axis direction). The second sheet 120 can transmit the light passing through the specific diffusion sheet 110 to the third sheet 130. The third sheet 130 can be formed in a shape in which a plurality of prisms (or triangular prisms) extend in the length direction (Y-axis direction) of the liquid crystal display device 1 and protrude in the height direction (Z-axis direction). The third sheet 130 can transmit the light passing through the second sheet 120 toward the liquid crystal panel 20. The light incident on the optical film 100 from the light source 11 is diffused and / or condensed when passing through the specific diffusion sheet 110, the second sheet 120, and the third sheet 130 in sequence, thereby having the advantages of not only ensuring the shielding performance of the shape that can block the light source 11 but also ensuring the high brightness performance. In Figures 1 to 3 In the illustrated embodiment, it is shown that the plurality of prism patterns of the second sheet 120 extend in the width direction (X-axis direction) of the liquid crystal display device 1, and the plurality of prism patterns of the third sheet 130 extend in the length direction (Y-axis direction) of the liquid crystal display device 1, but it is not necessarily limited thereto. On the contrary, the plurality of prism patterns of the second sheet 120 may extend in the length direction (Y-axis direction) of the liquid crystal display device 1, and the plurality of prism patterns of 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 plurality of prism patterns of the second sheet 120 and the plurality of prism patterns of the third sheet 130 are orthogonal to each other.

[0034] Figure 4 is a cross-sectional view of the optical film 100 according to an embodiment.

[0035] The optical film 100 according to an embodiment of the present disclosure includes a specific diffusion sheet 110, a second sheet 120, and a third sheet 130, thereby providing excellent light source shielding performance and brightness performance.

[0036] Referring to Figure 4, the specific diffusion sheet 110, the second sheet 120, and the third sheet 130 may respectively include a first base material portion 112, a second base material portion 122, and a third base material portion 132. Among them, the first base material portion 112, the second base material portion 122, and the third base material portion 132 may be composed of a transparent material capable of transmitting light (for example, substances such as polycarbonates, polysulfones, polyacrylates, polystyrenes, polyvinyl chlorides, polyvinyl alcohols, polynorbornenes, and polyesters). Specifically, the first base material portion 112, the second base material portion 122, and / or the third base material portion 132 may be composed of polyethylene terephthalate (PET) or polyethylene naphthalate (PEN). For example, the first base material portion 112, the second base material portion 122, and the third base material portion 132 may be PET with a thickness of about 10 to 100 μm, and more specifically, may be PET with a thickness of about 24 to 75 μm. However, it should be noted that the thickness of the first base material portion 112, the second base material portion 122, and the third base material portion 132 is not limited to the example range.

[0037] The specific diffusion sheet 110 may include a first pattern 113. The first pattern 113 may protrude along one direction of the specific diffusion sheet 110. The first pattern 113 may have a triangular prism shape. The first base material portion 112 may include a first-1 base material surface 112a and a first-2 base material surface 112b. The first-1 base material surface 112a may be the surface opposite to the second sheet 120. The first-2 base material surface 112b may be the surface opposite to the light guide plate (for example: Figure 1 the light guide plate 12). The first pattern 113 may protrude from the first-2 base material surface 112b.

[0038] The specific diffusion sheet 110 may include a pyramid pattern 111. The pyramid pattern 111 may have a pyramid shape. The pyramid pattern 111 may have a quadrangular pyramid shape. The pyramid pattern 111 may protrude from the first-1 base material surface 112a. The pyramid pattern 111 may protrude toward the second sheet 120.

[0039] In addition, the specific diffusion sheet 110 may include a diffusion pattern to replace the pyramid pattern 111.

[0040] The second sheet 120 may include a second pattern 121. The second pattern 121 may protrude along one direction of the second sheet 120. The second pattern 121 may have a triangular prism shape. The second base material portion 122 may include a second-1 base material surface 122a and a second-2 base material surface 122b. The second-1 base material surface 122a may be the surface opposite to the third sheet 130. The second-2 base material surface 122b may be the surface opposite to the specific diffusion sheet 110. The second pattern 121 may protrude from the second-1 base material surface 122a. The second pattern 121 may protrude toward the third sheet 130.

[0041] The third sheet 130 may include a third pattern 131. The third pattern 131 may protrude along one direction of the third sheet 130. The third pattern 131 may have a triangular prism shape. The third base portion 132 may include a 3-1 base surface 132a and a 3-2 base surface 132b. The 3-1 base surface 132a may be the surface opposite to the liquid crystal panel (e.g., Figure 1 the liquid crystal panel 20). Alternatively, the 3-1 base surface 132a may be the surface opposite to the diffusion sheet (e.g., Figure 1 the diffusion sheet 17). The 3-2 base surface 132b may be the surface opposite to the second sheet 120. The third pattern 131 may protrude from the 3-1 base surface 132a. The third pattern 131 may protrude toward the liquid crystal panel 20.

[0042] Figure 5 is an exploded schematic view of the backlight unit 10. Refer to Figure 5 The components described may be partially or entirely the same as the components described with reference to Figures 1 to 4

[0043] The first direction D1 may be the direction in which the light guide plate 12 extends. The first direction D1 may be a direction parallel to the Y-axis. The first direction D1 may be the direction in which light irradiates from the light source 11. The first direction D1 may be named the "light output direction".

[0044] The second direction D2 may be the extending direction of the first pattern 113 of the specific diffusion sheet 110. The second direction D2 may be a direction parallel to the Y-axis. The first pattern 113 may include a first corner 1131. The first corner 1131 may form the vertex of the first pattern 113. The second direction D2 may be the direction in which the first corner 1131 extends. The second direction D2 may be named the "reference direction".

[0045] The third direction D3 may be a direction intersecting the Y-axis. The third direction D3 may be a direction intersecting the second direction D2. The third direction D3 may be the direction in which the plurality of pyramid patterns 111 are arranged. The third direction D3 may be named the "pyramid pattern direction".

[0046] Refer to Figure 6 , the 3-1 direction - D3 may be a direction symmetric to the third direction D3 with respect to the reference direction D2. The 3-1 direction - D3 may be the direction in which the plurality of pyramid patterns 111 are arranged.

[0047] The fourth direction D4 can be the direction in which the third sheet 130 extends. The fourth direction D4 can be a direction parallel to the Y-axis. The fourth direction D4 can be the extending direction of the third pattern 131. The fourth direction D4 can be a direction perpendicular to the direction in which a plurality of third patterns 131 are arranged. The fourth direction D4 can be named the "third pattern direction". The third pattern 131 can include a third corner 1311. The third corner 1311 can form the vertex of the third pattern 131. The 4-1 direction - D4 can be a direction symmetric to the fourth direction D4 with respect to the reference direction D2.

[0048] The fifth direction D5 can be the direction in which the second sheet 120 extends. The fifth direction D5 can be a direction parallel to the X-axis. The fifth direction D5 can be the extending direction of the second pattern 121. The fifth direction D5 can be a direction perpendicular to the direction in which a plurality of second patterns 121 are arranged. The fifth direction D5 can be named the "second pattern direction". The second pattern 121 can include a second corner 1211. The second corner 1211 can form the vertex of the second pattern 121. The fifth direction D5 can be the direction in which the second corner 1211 extends. The 5-1 direction - D5 can be a direction symmetric to the fifth direction D5 with respect to the reference direction D2. The 5-1 direction - D5 can be the direction in which the second corner 1211 extends.

[0049] Figure 6 is a conceptual diagram for describing the angles between different components that make up a backlight unit (e.g., Figure 5 the backlight unit 10). The components described with reference to Figure 6 can be partially or entirely the same as the components described with reference to Figures 1 to 5

[0050] Different components that make up the backlight unit 10 (e.g., the light guide plate 12, the specific diffusion sheet 110, the second sheet 120, the third sheet 130) can be inclined relative to each other. Different components that make up the backlight unit 10 (e.g., the light guide plate 12, the specific diffusion sheet 110, the second sheet 120, the third sheet 130) can be inclined relative to each other. An included angle can be formed between different components that make up the backlight unit 10 (e.g., the light guide plate 12, the specific diffusion sheet 110, the second sheet 120, the third sheet 130).

[0051] The specific diffusion sheet 110 can be parallel to the light extraction direction D1. The reference direction D2 can be parallel to the light extraction direction D1. The first corner 1131 of the first pattern 113 can extend parallel to the light extraction direction D1.

[0052] ​The pyramid pattern direction D3 can be inclined relative to the reference direction D2. The pyramid pattern 111 can include an inclined surface 1111. The inclined surface 1111 of the pyramid pattern 111 can be a part of the bottom surface of the pyramid pattern 111 having a quadrangular pyramid shape. The inclined surface 1111 of the pyramid pattern 111 can be inclined relative to the reference direction D2. The pyramid pattern 111 can have an included angle A1 relative to the reference direction D2. The included angle between the pyramid pattern 111 and the reference direction D2 can be in the range of 40 degrees to 50 degrees. The included angle between the pyramid pattern 111 and the reference direction D2 can be 45 degrees. The pyramid pattern 111 can have an included angle -A1 relative to the reference direction D2. The included angle between the pyramid pattern 111 and the reference direction D2 can be in the range of -40 degrees to -50 degrees. The included angle between the pyramid pattern 111 and the reference direction D2 can be -45 degrees. Among them, the included angle represented by a positive number (+) (for example: A1, 40 degrees to 50 degrees) can represent the angle of the first direction relative to the reference direction D2 (for example: clockwise direction). Among them, the included angle represented by a negative number (-) (for example: -A1, -40 degrees to -50 degrees) can represent the angle of the second direction relative to the reference direction D2 (for example: counterclockwise direction). The included angle between the pyramid pattern 111 and the reference direction D2 can be in the range of -45 degrees to +45 degrees.

[0053] The third pattern direction D4 can be inclined relative to the reference direction D2. The third pattern 131 can include a third pattern corner 1311. The third pattern corner 1311 can be the same as the third corner 1311 described with reference to Figure 5 The third pattern corner 1311 can be inclined relative to the reference direction D2. The third pattern 131 can have an included angle A2 relative to the reference direction D2. The included angle A2 between the third pattern 131 and the reference direction D2 can be in the range of 25 degrees to 35 degrees. The included angle A2 between the third pattern 131 and the reference direction D2 can be 30 degrees. The third pattern 131 can have an included angle -A2 relative to the reference direction D2. The included angle -A2 between the third pattern 131 and the reference direction D2 can be in the range of -25 degrees to -35 degrees. The included angle -A2 between the third pattern 131 and the reference direction D2 can be -30 degrees. Among them, the included angle represented by a positive number (+) (for example: A2, 25 degrees to 35 degrees) can represent the angle of the first direction relative to the reference direction D2 (for example: clockwise direction). Among them, the included angle represented by a negative number (-) (for example: -A2, -25 degrees to -35 degrees) can represent the angle of the second direction relative to the reference direction D2 (for example: counterclockwise direction). The included angle A2 between the third pattern 131 and the reference direction D2 can be in the range of -30 degrees to +30 degrees.

[0054] The second pattern direction D5 can be inclined relative to the reference direction D2. The second pattern 121 can include a second pattern corner 1211. The second pattern corner 1211 can be the same as the one described with reference to Figure 5is the same as the second corner 1211 described. The second pattern corner 1211 can be inclined relative to the reference direction D2. The second pattern 121 can have an included angle A3 relative to the reference direction D2. The included angle A3 between the second pattern 121 and the reference direction D2 can be in the range of 55 degrees to 65 degrees. The included angle A3 between the second pattern 121 and the reference direction D2 can be 60 degrees. The second pattern 121 can have an included angle -A3 relative to the reference direction D2. The included angle -A3 between the second pattern 121 and the reference direction D2 can be in the range of -55 degrees to -65 degrees. The included angle -A3 between the second pattern 121 and the reference direction D2 can be -60 degrees. Among them, the included angle represented by a positive number (+) (e.g., A3, 55 degrees to 65 degrees) can represent the angle of the first direction relative to the reference direction D2 (e.g., the clockwise direction). Among them, the included angle represented by a negative number (-) (e.g., -A3, -55 degrees to -65 degrees) can represent the angle of the second direction relative to the reference direction D2 (e.g., the counterclockwise direction). The included angle between the second pattern 121 and the reference direction D2 can be in the range of -60 degrees to +60 degrees.

[0055] The third pattern direction D4 and the second pattern direction D5 can intersect each other. The third pattern direction D4 and the second pattern direction D5 can be inclined relative to each other. The third pattern corner 1311 of the third pattern 131 can extend in a direction intersecting with the second pattern corner 1211 of the second pattern 121. The third pattern corner 1311 can be inclined relative to the second pattern corner 1211. An included angle (A4, -A4) can be formed between the third pattern direction D4 and the second pattern direction D5. An included angle (A4, -A4) can be formed between the third pattern corner 1311 and the second pattern corner 1211. The included angle (A4, -A4) can be 90 degrees. That is, the second sheet 120 and the third sheet 130 can be orthogonal to each other. At this time, the orthogonality of the second sheet 120 and the third sheet 130 can mean that the third pattern 131 and the second pattern 121 can extend in mutually orthogonal directions.

[0056] Figure 7 is a schematic diagram for explaining the brightness characteristics when changing the direction relative to the reference direction D2 in a state where the second sheet and the third sheet are vertically fixed. Refer to Figure 7 the components described can be partially or entirely the same as the components referred to in Figures 1 to 6 the description.

[0057] The brightness loss of the optical film 100 should be controlled within the allowable range R. The optical film 100 according to an embodiment of the present disclosure can reduce the moiré phenomenon while controlling the brightness loss within the allowable range R. For example, the optical film 100 according to an embodiment of the present disclosure can reduce the moiré phenomenon while achieving the brightness loss within the allowable range R by adjusting the included angle A2 or the included angle A3 between the third pattern direction D4 or the second pattern direction D5 and the reference direction D2 to a predetermined range. For example, the included angle A2 between the third pattern direction D4 and the reference direction D2 can be adjusted within a range of -30 degrees to +30 degrees. The included angle A2 between the third pattern direction D4 and the reference direction D2 can be adjusted within the first allowable range C1, the second allowable range C2, and the third allowable range C3.

[0058] Figure 8 is a diagram for explaining the change of the viewing angle characteristics according to the included angle A1 between the pyramid pattern direction D3 and the reference direction D2 described with reference to Figure 6 The components described with reference to Figure 8 may be partially or entirely the same as the components described with reference to Figures 1 to 7 described.

[0059] The first viewing angle may mean the viewing angle of the light transmitted through a specific diffusion sheet 110. The second viewing angle may mean the viewing angle of the light transmitted through the specific diffusion sheet 110, the second sheet 120, and the third sheet 130.

[0060] With reference to Figure 8 it can be seen that when the included angle A1 between the pyramid pattern direction D3 and the reference direction D2 is within a predetermined range (for example, within 30 degrees to 60 degrees), the first viewing angle and the second viewing angle are improved. In addition, when the included angle A1 between the pyramid pattern direction D3 and the reference direction D2 is within a predetermined range (for example, within 40 degrees to 50 degrees), the brightness loss is minimized.

[0061] As described with reference to the optical film 100 according to an embodiment of the present disclosure Figures 5 to 8 shown, an inclination angle may be formed between the components constituting the optical film 100. By adopting the above structure, the optical film 100 according to an embodiment of the present disclosure can improve the moiré phenomenon while reducing the brightness loss. Moreover, by adopting the above structure, the optical film 100 according to an embodiment of the present disclosure can reduce the process deviation that occurs in the manufacturing process of the optical film 100. For example, when the optical film 100 is manufactured in a state where the inclination angle between the components constituting the optical film 100 is set, the process deviation (for example, the deviation from the specified design value of the pattern) of the components constituting the optical film 100 (for example, the specific diffusion sheet 110, the second sheet 120, the third sheet 130) can be reduced.

Claims

1. An optical film, characterized in that: It includes: A specific diffusion sheet including a first pattern forming a reference direction, where the reference direction is the extension direction of the first pattern; A third sheet spaced apart from the specific diffusion sheet and including a third pattern extending along a third pattern direction; and A second sheet disposed between the specific diffusion sheet and the third sheet and including a second pattern extending along a second pattern direction, At least one of the second pattern and the third pattern is inclined with respect to the reference direction, The third pattern forms an included angle within the range of -30 degrees to +30 degrees with respect to the reference direction.

2. The optical film according to claim 1, characterized in that: Both the second pattern and the third pattern are inclined with respect to the reference direction.

3. The optical film according to claim 1, characterized in that: The second pattern is orthogonal to the third pattern.

4. The optical film according to claim 1, characterized in that: The specific diffusion sheet includes a pyramid pattern inclined within the range of -45 degrees to +45 degrees with respect to the reference direction.

5. The optical film according to claim 1, characterized in that: The first pattern, the second pattern, and the third pattern are inclined with respect to each other.

6. A backlight unit, characterized in that: It includes: A light source; A light guide plate through which light irradiated from the light source is transmitted; An optical film through which light traveling from the light guide plate is transmitted, The optical film includes: A specific diffusion sheet including a first pattern forming a reference direction, where the reference direction is the extension direction of the first pattern; A third sheet spaced apart from the specific diffusion sheet and including a third pattern extending along a third pattern direction; and A second sheet disposed between the specific diffusion sheet and the third sheet and including a second pattern extending along a second pattern direction, At least one of the second pattern and the third pattern is inclined with respect to the reference direction, The third pattern forms an included angle within the range of -30 degrees to +30 degrees with respect to the reference direction.

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