Optical film and backlight unit containing it

Abstract

To provide an optical film for a liquid crystal display device that is excellent in performance of preventing the shape of a light source from being visually recognized on a liquid crystal panel, and has high brightness.SOLUTION: An optical film includes: a first sheet including a pyramid pattern layer having a plurality of pyramid patterns formed on one face of a first base part, and a first diffusion layer having a plurality of optical projection patterns formed on the other face of the first base part; a second sheet including a first prism pattern layer having a plurality of prism patterns formed on one face of a second base part, and a second diffusion layer having a plurality of optical projection patterns with adhesive properties formed on the other face of the second base part; and a third sheet including a second prism pattern layer having a plurality of prism patterns formed on one face of a third base part, and a third diffusion layer having a plurality of optical projection patterns with adhesive properties formed on the other face of the third base part. The first, second, third sheets are laminated into one by the optical projection patterns of the second and third diffusion layers.SELECTED DRAWING: Figure 4a

Description

Technical Field

[0001] Various embodiments of the present disclosure relate to an optical film used in a liquid crystal display device and a backlight unit including the same.

Background Art

[0002] As a light source, a liquid crystal display device using mini-LEDs (light emitting diodes) and / or micro-LEDs, which have advantages such as miniaturization, weight reduction, and / or low power consumption, is actively utilized. Each mini-LED or micro-LED chip can constitute an individual pixel or light source, eliminating restrictions on the size and shape of the display and enabling a clearer image quality than when using existing light sources. Along with the miniaturization of the LED chip size, research on backlight units for compensating for the characteristics of LED light is also actively underway.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] A direct-lit backlight unit using mini-LEDs or micro-LEDs as the light source may include a diffusion sheet for converting the light from a point source into a surface light source, and a prism sheet for focusing the light and improving brightness. In a direct-lit backlight unit, since the light source is positioned on a plane, a thick diffusion sheet or a structure in which multiple diffusion sheets are stacked may be applied to prevent the shape of the light source (e.g., the shape of the mini-LED or micro-LED) from being visible on the liquid crystal panel, i.e., to shield the shape of the light source. Furthermore, a direct-lit backlight unit may include a prism sheet with a triangular prism-shaped prism pattern layer formed on one surface, which can increase the brightness of the surface light source that has passed through the diffusion sheet.

[0005] However, if the diffusion sheet is made thicker to prevent the shape of the light source from being visible on the liquid crystal panel, there is a limit to how thin the liquid crystal display can be made, and the thickness of the diffusion sheet may cause a significant decrease in the brightness of the liquid crystal display. Therefore, by laminating at least one diffusion sheet and / or at least one prism sheet, it is possible to increase the degree of shielding without making the diffusion sheet thicker, while preventing a decrease in brightness. For example, an optical film may have a form in which one diffusion sheet and two prism sheets are laminated. However, even when one diffusion sheet and two prism sheets are laminated, a decrease in brightness due to the lamination form may occur.

[0006] The present invention aims to provide an optical film for liquid crystal display devices that, through various embodiments, has excellent performance in preventing the shape of the light source from being visible on the liquid crystal panel (hereinafter also referred to as "shielding performance") without using a thick diffusion sheet, and at the same time has high brightness (hereinafter also referred to as "brightness performance"). [Means for solving the problem]

[0007] According to various embodiments of the present disclosure, an optical film comprises: a first sheet including a first base portion, a pyramid pattern layer having a plurality of pyramid patterns formed on one surface of the first base portion, and a first diffusion layer having a plurality of optical projection patterns formed on the other surface of the first base portion; a second sheet disposed on top of the first sheet, including a second base portion, a first prism pattern layer having a plurality of prism patterns formed on one surface of the second base portion, and a second diffusion layer having a plurality of adhesive optical projection patterns formed on the other surface of the second base portion; and disposed on top of the second sheet An optical film can be provided in which the first, second, and third sheets are laminated together by the multiple adhesive optical protrusions of the second and third diffuse layers. The third sheet includes a third base portion, a second prism pattern layer having a plurality of prism patterns formed on one surface of the third base portion, and a third diffuse layer having a plurality of adhesive optical protrusion patterns formed on the other surface of the third base portion, wherein the refractive index of the pyramid pattern layer is greater than or equal to that of the first diffuse layer, the haze value of the first diffuse layer is 15% or more, and the first, second, and third sheets are laminated together by the plurality of adhesive optical protrusions of the second and third diffuse layers.

[0008] According to various embodiments of the present disclosure, a backlight unit can be provided that includes a light source, a color conversion sheet for converting the color of light emitted from the light source, and an optical film disposed on top of the color conversion sheet. [Effects of the Invention]

[0009] According to various embodiments of this disclosure, the absence of a thick diffusion sheet can contribute to making the backlight unit thinner.

[0010] According to various embodiments of this disclosure, it is possible to provide an optical film that has excellent shielding performance for mini-LEDs or micro-LEDs and also has excellent brightness performance, as well as a backlight unit including the same.

[0011] The effects obtained from this disclosure are not limited to those mentioned above, and other effects not mentioned above can be clearly understood by a person with ordinary skill in the art to which this disclosure pertains from the following description. [Brief explanation of the drawing]

[0012] [Figure 1] This figure shows a liquid crystal display device including a diffusion sheet according to one embodiment. [Figure 2] This figure shows a liquid crystal display device to which an optical film according to one embodiment of the present disclosure is applied. [Figure 3] This is a perspective view showing a liquid crystal display device to which an optical film according to one embodiment of the present disclosure is applied. [Figure 4a] This is a cross-sectional view showing an optical film according to one embodiment of the present disclosure. [Figure 4b] This is a perspective view showing a pyramidal pattern according to one embodiment of the present disclosure. [Figure 4c] This is a perspective view showing a pyramidal pattern according to one embodiment of the present disclosure. [Figure 4d] This figure shows the pyramid pattern layer in its pre-lamination state, as viewed from above, according to one embodiment of the present disclosure. [Figure 4e] This figure shows the pyramid pattern layer after lamination according to one embodiment of the present disclosure, viewed from above. [Figure 5a] This figure shows the viewing angle based on the vertex angle of an optical film according to one embodiment of the present disclosure. [Figure 5b] This figure shows the viewing angle based on the vertex angle of an optical film according to one embodiment of the present disclosure. [Figure 6a] This figure shows the illuminance (degree of shielding) at the vertex angle of an optical film according to one embodiment of the present disclosure. [Figure 6b] This figure shows the illuminance (degree of shielding) at the vertex angle of an optical film according to one embodiment of the present disclosure. [Figure 7] This disclosure shows the configuration of an experiment for measuring luminance according to one embodiment. [Figure 8a]It is a diagram showing the optical characteristics between the liquid crystal display device disclosed in the embodiment of FIG. 1 and the liquid crystal display devices disclosed in the embodiments of FIGS. 2 to 6b. [Figure 8b] It is a diagram showing the optical characteristics between the liquid crystal display device disclosed in the embodiment of FIG. 1 and the liquid crystal display devices disclosed in the embodiments of FIGS. 2 to 6b. [Figure 9] It is a graph showing the optical characteristics between the liquid crystal display device disclosed in the embodiment of FIG. 1 and the liquid crystal display devices disclosed in the embodiments of FIGS. 2 to 6b. [Figure 10a] It is a diagram showing other optical characteristics between the liquid crystal display device disclosed in the embodiment of FIG. 1 and the liquid crystal display devices disclosed in the embodiments of FIGS. 2 to 6b. [Figure 10b] It is a diagram showing other optical characteristics between the liquid crystal display device disclosed in the embodiment of FIG. 1 and the liquid crystal display devices disclosed in the embodiments of FIGS. 2 to 6b. [Figure 11] It is a graph showing other optical characteristics between the liquid crystal display device disclosed in the embodiment of FIG. 1 and the liquid crystal display devices disclosed in the embodiments of FIGS. 2 to 6b.

Embodiments for Carrying Out the Invention

[0013] Various embodiments of this specification and the terms used therein are not intended to limit the technical features described in this specification to a specific embodiment, but should be understood to include various modifications, equivalents, or alternatives of that embodiment. Regarding the description of the drawings, similar or related components can use the same reference numerals. The singular form of the noun corresponding to an item can include one or more of the said items in the relevant context, unless otherwise specified.

[0014] According to various embodiments, each of the aforementioned components (e.g., a module or a program) may contain one or more objects, and some of the objects may be separated and placed 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., a module or a program) can be integrated into a single component. In such cases, the integrated component can perform one or more functions of each of the multiple components in the same or similar manner as those performed by the component in the multiple components before integration. According to various embodiments, operations performed by a module, program or other component may be performed sequentially, in parallel, repeatedly, or empirically, or one or more of the operations may be performed in a different order, or omitted, or one or more other operations may be added.

[0015] Various embodiments will be described below with reference to the attached drawings. In describing these embodiments, the same names and reference numerals will be used for identical components, and any further explanation will be omitted. Furthermore, in describing embodiments of the present invention, it should be noted that components having the same function will not be substantially identical to those in the conventional invention, even if the same names and reference numerals are used.

[0016] Depending on the various embodiments, terms such as “includes” or “having” should be understood to indicate the presence of features, figures, stages, operations, components, parts, or combinations thereof described in the specification, without prejudice to the possibility of the presence or addition of one or more other features, figures, stages, operations, components, parts, or combinations thereof.

[0017] Figure 1 shows a liquid crystal display device 1 including a diffusion sheet according to one embodiment.

[0018] In the following detailed description, the longitudinal direction (vertical direction) of the liquid crystal display device 1 can 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." In some embodiments, the direction that a component points can be expressed in conjunction with the Cartesian coordinate system illustrated in the drawings, using both "negative / positive (- / +)." For example, referring to Figure 1, if the second prism sheet 16 is positioned on top of the first prism sheet 15, then the second prism sheet 16 can be defined as being positioned in the "+Z-axis direction (or first direction)" from the first prism sheet 15. Also, for example, referring to Figure 4a, one surface of the first base portion 112 can be defined as the "surface facing the +Z-axis direction (or first direction)," and the other surface as the "surface facing the -Z-axis direction (or second direction)." When describing directions, as shown in Figure 1 below, if "negative / positive (- / +)" is not indicated in the Cartesian coordinate system, unless otherwise defined, the coordinate axis may be interpreted as pointing in the positive direction. For example, "X-axis direction" can be interpreted as pointing in the +X-axis direction, "Y-axis direction" can be interpreted as pointing in the +Y-axis direction, and "Z-axis direction" can be interpreted as pointing in the +Z-axis direction. In describing directions, pointing towards one of the three axes of the Cartesian coordinate system may include pointing in a direction parallel to that axis. Note that this is based on the Cartesian coordinate system shown in the drawings for the sake of brevity, and such descriptions of directions or components do not limit the various embodiments of this disclosure.

[0019] Referring to Figure 1, the 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 back surface (the surface facing the -Z axis) of the liquid crystal panel 20 so as to radiate light to the liquid crystal panel 20. The backlight unit 10 may include a substrate 11 containing a light source 11a, a color conversion sheet 13, a diffusion sheet 14, 17, and prism sheets 15, 16. The backlight unit 10 may further include a reflective polarizing sheet, although this is not shown in the drawings.

[0020] The light source 11a is configured to emit light to the back of the liquid crystal panel 20 and can be arranged on one side of the substrate 11. The light source 11a may be a light-emitting diode (LED). The light source 11a may include, for example, multiple LED chips that emit light. Here, the LED may be made of materials such as InGaN or GaN. LEDs can be classified into large LEDs (chip size: 1,000 μm or more), middle LEDs (chip size: 300 to 500 μm), small LEDs (chip size: 200 to 300 μm), mini LEDs (chip size: 100 to 200 μm), and micro LEDs (chip size: 100 μm or less) depending on the size of the LED chip. As the light source 11a in this disclosure, the LED may include any of the large LEDs, medium LEDs, small LEDs, mini LEDs, or micro LEDs. The embodiment in Figure 1 is shown to include, for example, a mini LED. Light emitted from the light source 11a can diverge towards the back of the liquid crystal panel 20 (in the +Z axis direction). Light emitted from the light source 11a can pass through the color conversion sheet 13 and enter the diffusion sheet 14.

[0021] According to one embodiment, a reflective sheet 12 may be formed on the surface of the substrate 11. The reflective sheet 12 may contain substances such as BaSO4, TiO2, CaCO3, SiO2, Ca3(SO4)2, or substances such as Ag, and may be applied or coated on the substrate 11 between the light sources 11a. The reflective sheet 12 can reflect the light emitted from the light source 11a back towards the substrate 11 in the direction of light emission, as the light is transmitted through the color conversion sheet 13, diffusion sheets 14, 17 and prism sheets 15, 16, according to interfacial reflection, etc. This minimizes light loss. In other words, the reflective sheet 12 can perform light recycling.

[0022] The color conversion sheet 13 can convert the color of the light emitted from the light source 11a. For example, the light from a mini-LED or micro-LED may be blue light (450 nm). In this case, the blue light needs to be converted to white light. As a result, the color conversion sheet 13 can transmit the blue light emitted from the light source 11a while simultaneously converting the blue light to white light.

[0023] The diffusion sheets 14 and 17 can uniformly disperse the light incident from the color conversion sheet 13. The diffusion sheets 14 and 17 can be coated with a curable resin solution (for example, a mixture of one or more selected from at least one of urethane acrylate, epoxy acrylate, ester acrylate, and radical-generating monomers) to induce light diffusion by the light-diffusing beads. In addition, the diffusion sheets 14 and 17 can be formed with a pattern of protrusions (or projections) of uniform or non-uniform size (for example, spherical, hemispherical, or elliptical) to promote light diffusion.

[0024] The diffusion sheets 14 and 17 may include at least one of the lower diffusion sheet 14 and the upper diffusion sheet 17. The lower diffusion sheet 14 may be placed between the color conversion sheet 13 and the prism sheet 15, and the upper diffusion sheet 17 may be placed between the prism sheet 16 and the liquid crystal panel 20. If the backlight unit 10 further includes a reflective polarizing sheet, the upper diffusion sheet 17 may be placed between the prism sheet 16 and the reflective polarizing sheet.

[0025] The prism sheets 15 and 16 can focus incident light using an optical pattern formed on their surface and then emit it to the liquid crystal panel 20. The prism sheets 15 and 16 may include a translucent base film and a prism pattern layer formed on the upper surface (the surface facing the +Z axis) of the base film. The prism pattern layer may be formed as an optical pattern layer in the form of a triangular array, with inclined surfaces at a specified angle (e.g., a 45° inclined surface) to improve brightness in the planar direction. The prism pattern of the prism pattern layer may be triangular prism-shaped, and one side of the triangular prism may be positioned opposite the base film. Each cross-section of the prism pattern may be triangular.

[0026] According to one embodiment, the prism sheets 15 and 16 can form a composite prism sheet structure including a first prism sheet 15 and a second prism sheet 16. Here, the second prism sheet 16 may be placed on top of the first prism sheet 15. In the first prism sheet 15, a plurality of first prism patterns may be arranged side by side. Each first prism pattern may have a structure that extends in one direction. For example, each vertex line of the first prism pattern may be formed to extend in the direction of the X-axis. Similarly, in the second prism sheet 16, a plurality of second prism patterns may also be arranged side by side. Each second prism pattern may have a structure that extends in one direction. For example, each vertex line 16a of the second prism pattern may be formed to extend in the direction of the Y-axis perpendicular to the X-axis. Here, for the sake of explanation, the extension directions of the first prism pattern and the extension directions of the second prism pattern are shown toward the X and Y axes. However, the embodiment is not limited to the illustrated one, and may be oriented in directions other than the X or Y axis.

[0027] The reflective polarizing sheet (not shown) is provided above the prism sheets 15 and 16 and the upper diffusion sheet 17, and plays a role in allowing some of the polarized light, which is focused from the prism sheets 15 and 16 and diffused by the upper diffusion sheet, to pass through and reflect the other polarized light to the lower surface.

[0028] The liquid crystal panel 20 can refract light emitted from the light source 11a into a predetermined pattern according to an electrical signal. This refracted light passes through a color filter and a polarizing filter placed on the front of the liquid crystal panel 20 to form a screen.

[0029] The components included in the liquid crystal display device 1 in Figure 1 can be assembled in an overlapped state and a stacked state with other components in the height direction (Z-axis direction). For example, in the liquid crystal display device 1 according to one embodiment, as shown in Figure 1, the individually manufactured lower diffusion sheet 14, first prism sheet 15 and second prism sheet 16 can be overlapped and stacked in the height direction (Z-axis direction).

[0030] Figure 2 shows a liquid crystal display device 1 to which an optical film according to one embodiment of the present disclosure is applied. Figure 3 is a perspective view showing the liquid crystal display device 1 to which an optical film according to one embodiment of the present disclosure is applied.

[0031] Referring to Figure 2, a liquid crystal display device (or LCD (liquid crystal display) device) 1 according to one embodiment of the present disclosure may include a backlight unit 10 and a liquid crystal panel 20. The backlight unit 10 may include a substrate 11 including a light source 11a and an optical film 100. A reflective sheet 12 may be formed on one surface of the light source 11a. According to one embodiment of the present disclosure, the backlight unit 10 may further include a color conversion sheet 13 and / or a diffusion sheet 17. According to another embodiment, the backlight unit 10 may omit at least one of these components (e.g., the diffusion sheet 17), or may add one or more other components (e.g., a reflective polarizing sheet (not shown)).

[0032] The following explanation will omit details that overlap with Figure 1. The liquid crystal display device 1 of this disclosure is characterized in that the lower diffusion sheet 14, the first prism sheet 15, and the second prism sheet 16 of Figure 1 are not individually provided, and an optical film 100 of this disclosure is provided. That is, the liquid crystal display device 1 of this disclosure can provide an optical film 100 that replaces the lower diffusion sheet 14, the first prism sheet 15, and the second prism sheet 16 of Figure 1. However, it should be noted that this is not limited to this, and in addition to the lower diffusion sheet 14, the optical film 100 may be further provided, or sheets other than the lower diffusion sheet 14 may be further provided. For example, the backlight unit 10 of Figure 2 is shown to include a substrate 11 including a light source 11a, a color conversion sheet 13, an optical film 100, and a diffusion sheet 17, but a shielding sheet may be further included between the optical film 100 and the color conversion sheet 13. In this case, the shielding sheet placed between the optical film 100 and the color conversion sheet 13 can be a single sheet, as shown in the lower diffusion sheet 14 in Figure 1, or it can be a laminated form of multiple sheets, or various other embodiments can be applied.

[0033] In this disclosure, “optical film 100” can mean a film comprising a first sheet 110 having a plurality of pyramid patterns formed on one surface, a second sheet 120 placed on the first sheet 110 and having a plurality of prism patterns formed on one surface, and a third sheet 130 placed on the second sheet 120 and having a plurality of prism patterns formed on one surface, as shown in Figures 2 and 3. In Figures 2 and 3, for convenience of explanation, the first sheet 110, the second sheet 120, and the third sheet 130 are shown to be separated from each other, but contrary to this, the first sheet 110, the second sheet 120, and the third sheet 130 may be formed by lamination. In this disclosure, “lamination” can mean that two different sheets are bonded together by having at least one of the opposing surfaces of the two different sheets include a pattern formed of an adhesive resin. For example, one of the two opposing surfaces of two different sheets may have a pattern formed from a semi-cured adhesive resin, and the other surface may be in contact with this pattern before being fully cured and bonded together. Alternatively, for example, both opposing surfaces of two different sheets may be formed from a semi-cured adhesive resin, and after 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 better shielding performance than the embodiment in which it is simply laminated without lamination.

[0034] Multiple pyramidal (or square pyramidal) patterns on the first sheet 110 can refract and / or reflect light transmitted from the light source 11a and transmit it to the second sheet 120. The second sheet 120 may be formed in a manner in which multiple prisms (or triangular prisms) extend in the longitudinal direction (Y-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 that has passed through the first sheet 110 to the third sheet 130. The third sheet 130 may be formed in a manner in which multiple 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 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 11a is diffused and / or focused as it sequentially passes through the first sheet 110, the second sheet 120, and the third sheet 130, providing the advantage of ensuring not only shielding performance that covers the shape of the light source 11a, but also high brightness performance. In the embodiment shown in Figure 3, the prism pattern of the second sheet 120 extends in the longitudinal direction (Y-axis direction) of the liquid crystal display device 1, and the prism pattern of the third sheet 130 extends in the width direction (X-axis direction) of the liquid crystal display device 1. However, this is not necessarily limited to this, and alternatively, the prism pattern of the second sheet 120 may extend in the width direction (X-axis direction) of the liquid crystal display device 1, and the prism pattern of the third sheet 130 may extend in the longitudinal direction (Y-axis direction) of the liquid crystal display device 1. However, the prism patterns of the second sheet 120 and the third sheet 130 only need to be orthogonal to each other. Referring to Figure 3, the pyramid pattern layer 111 of the first sheet 110 may include a pyramid pattern (hereinafter, pyramid pattern 111a in Figure 4a) that includes a bottom surface having a length a in the first direction and a length b in the second direction, four sides 111-1, 111-2, 111-3, 111-4 having height h and apex angles A and B, and one bottom surface. The dimensions of the pyramid pattern can be set differently depending on the embodiment.

[0035] The optical film 100 will be described in more detail below with reference to Figure 4a.

[0036] Figure 4a is a cross-sectional view showing an optical film 100 according to one embodiment of the present disclosure. Figures 4b and 4c are perspective views showing a pyramid pattern according to one embodiment of the present disclosure. Figure 4d shows the pyramid pattern layer before lamination as viewed from above according to one embodiment of the present disclosure. Figure 4e shows the pyramid pattern layer after lamination as viewed from above according to one embodiment of the present disclosure.

[0037] Referring to Figure 4a, an optical film 100 according to one embodiment of the present disclosure may include a first sheet 110, a second sheet 120, and a third sheet 130. The first sheet 110, the second sheet 120, and the third sheet 130 may each include a first base portion 112, a second base portion 122, and a third base portion 132. In this case, the first base portion 112, the second base portion 122, and the third base portion 132 may be made of 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, etc. The first base portion 112, the second base portion 122, and the third base portion 132 may be PET having a thickness of approximately 10 to approximately 50 μm, and more specifically, PET having a thickness of approximately 24 to approximately 40 μm. In various experimental examples, including the field of view angle distribution described later in Figure 6a and subsequent drawings, the first base portion 112, the second base portion 122, and the third base portion 132 can be exemplified as PET having a thickness of 24 μm each. 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.

[0038] As illustrated in the embodiment of Figure 3, the first sheet 110 may include a pyramidal pattern 111a on one surface 112a of the first base portion 112, having a length a in the first direction, a length b in the second direction, a height h, a pitch P, and four sides 111-1, 111-2, 111-3, 111-4 that form vertex angles A and B. The optical film 100 may include multiple pyramidal patterns 111a having multiple columns in the first direction and multiple rows in the second direction perpendicular to the first direction.

[0039] Referring together to Figures 4a, 4b, and 4c, in one embodiment, the pyramid pattern 111a may be an incised pattern. The pyramid pattern 111a can mean an incised pattern in which square pyramidal grooves are regularly formed and can be defined by four sides 111-1, 111-2, 111-3, and 111-4. Here, the four sides may be the same or different triangular shapes, and the dimensions of vertex angles A and B can be set according to the lateral length a, vertical length b, and height of each cross section of the pyramid pattern 111a. According to one embodiment, vertex angles A and B can form substantially the same angle, thereby allowing the lateral length a and vertical length b of the pyramid pattern 111a to be set substantially equal. Here, vertex angles A and B being substantially identical can mean that vertex angles A and B have the same value within a process deviation (e.g., around 10%).

[0040] Furthermore, the height h and pitch P in the pyramid pattern 111a can be set based on the vertex angle C. The optical film 100 includes a pyramid pattern 111a with a vertical cross-section parallel to the height direction (Z-axis direction) that is triangular or trapezoidal, and the vertex angle C can be defined as the angle between two opposing sides of the four sides of the pyramid pattern 111a.

[0041] According to one embodiment, the vertex angle C in the pyramid pattern 111a can be defined as being between 60 degrees and 160 degrees. For example, the vertex angle C may be 90 degrees.

[0042] Figure 4d shows the pyramid pattern layer before the first sheet 110 is laminated to the second sheet 120, and Figure 4d can also show the pyramid pattern layer after the first sheet 110 has been laminated with the second sheet 120 and the first sheet 110 has been peeled off from the second sheet 120. Referring to Figure 4c, the pyramid pattern layer 111 before lamination may include a first partition 111-5 between the first side 111-1 and the fourth side 111-4, distinguishing the boundary between the first side 111-1 and the fourth side 111-4, and a second partition 111-6 between the second side 111-2 and the third side 111-3, distinguishing the boundary between the second side 111-2 and the third side 111-3. The first partition wall 111-5 and the second partition wall 111-6 may be the highest part of the first sheet 110. In one embodiment, the first partition wall 111-5 is formed parallel to the first direction and the second partition wall 111-6 is formed parallel to the second direction, but it should be noted that this is not necessarily limited. Referring to Figure 4e, 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 (for example, the second diffusion layer 123 on the back surface 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 uppermost end of the pyramid pattern layer 111, may be pressed. As a result, the tip of the first partition wall 111-5 deforms to form a first flat portion 111-7 having a predetermined width W1, and the tip of the second partition wall 111-6 deforms 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.

[0043] Figures 5a and 5b show the viewing angle of the optical film 100 at its vertex angle according to one embodiment of the present disclosure. Figures 6a and 6b show the illuminance (degree of shielding) of the optical film 100 at its vertex angle according to one embodiment of the present disclosure.

[0044] Referring to Figures 5a and 5b, the field of view distribution and luminance based on the vertex angle can be explained. Figure 5a shows the field of view distribution and luminance measurement results when the pyramid pattern has a vertex angle of 90 degrees, and Figure 5b shows the field of view distribution and luminance measurement results when the pyramid pattern has a vertex angle of 130 degrees. Figures 5a and 5b show that the chief ray of light passes through the center of the drawing, and the marginal rays of light pass through the periphery, and the brightness can be shown in various color distributions depending on the light intensity of the chief ray and the marginal rays. Referring to Figures 5a and 5b, it can be confirmed that the luminance is high in the center and gradually decreases from the center to the periphery. However, in Figure 5a, it can be confirmed that the luminance increases at the edges of the periphery. In Figure 5b, it can be confirmed that the light is more concentrated in the center compared to Figure 5a. Within the specified range, the larger the vertex angle of the pyramid pattern layer 111, the smaller the degree of light diffusion incident on the optical film 100, allowing light to be concentrated in the center. Conversely, as the vertex angle decreases, the degree of light diffusion increases, which can lead to greater brightness loss. In other words, the degree of light diffusion can be said to mean the probability that light is reflected back within the liquid crystal display device 1, i.e., the probability of recycling. As the vertex angle decreases, the probability of light recycling can increase, which in turn can increase the degree of shielding (and thus increase the brightness loss rate).

[0045] According to various embodiments of this disclosure, the inclusion of a pyramidal pattern layer 111 allows for control of light in the four planes of the periphery. According to one embodiment of this disclosure, the pyramidal pattern layer 111 may include a pyramidal pattern 111a where the vertex angle, which is the angle between two opposing triangles, is between 90 and 130 degrees. According to one embodiment, when the vertex angle of the pyramidal pattern 111a is formed at an angle of at least 90 degrees, shielding performance can be satisfied, as shown in Figure 6a, and when the vertex angle is less than that, the hot spot visibility (HSV) of the light source 11a may be increased. The illuminance (shielding) with respect to the vertex angle can be described with reference to Figures 6a and 6b. Figure 6a shows the illuminance (shielding) when the pyramidal pattern has a vertex angle of 90 degrees, and Figure 6b shows the illuminance (shielding) when the pyramidal pattern has a vertex angle of 130 degrees. Figure 6a shows that the visibility of multiple light sources 11a separated by a predetermined interval decreases (within the specified range, as the vertex angle decreases, the probability of light recycling increases, the degree of light diffusion increases, the luminance loss increases, and the degree of occlusion increases). In comparison, Figure 6b shows that the light sources 11a and the dark area distribution 11b around the light sources 11a are more clearly visible than in Figure 6a, and the visibility is higher (within the specified range, as the vertex angle increases and the degree of light diffusion decreases, the light is focused towards the center and the degree of occlusion decreases).

[0046] The pyramid pattern layer 111 may consist of multiple pyramid patterns, which may be regularly arranged on one surface of the first sheet 110. The multiple pyramid patterns are arranged in a 1:1 correspondence with the light source 11a formed on the substrate 11, or at least partially overlapping, thereby diffusing the point light source emitted from the light source into a surface light source. At the same time, the light from the light source 11a is light-separated (or light-diffused) by the diffusing effect of the optical film 100, thereby reducing the visibility of hot spots (HSV) due to light concentration. A first diffusion layer 113 having multiple optical protrusion patterns may be formed on the other surface 112b of the first base portion 112. The first diffusion layer 113 may have optical protrusion patterns formed by adding light-diffusing beads to a solution of a curable resin (for example, at least one selected from urethane acrylate, epoxy acrylate, ester acrylate, and radical-generating monomer, and mixing one or more of them) to induce light diffusion. Furthermore, the first diffusion layer 113 can be fabricated to include an optical projection pattern by using all methods to increase turbidity, including matte treatment to form a rough surface and bead treatment using beads such as glass or polymer. In various experimental examples, including the field of view distribution described later in Figure 8 and subsequent figures, the first diffusion layer 113 can be exemplified as having a haze value of at least 15%.

[0047] On the other hand, if the haze value of the first diffusion layer 113 is set to 15% or higher, not only the shielding power but also the brightness can be improved. For example, the optical projection pattern of the first diffusion layer 113 can be formed as an inverse prism pattern, as shown in the structure disclosed in Figure 4c, to achieve high brightness.

[0048] In various embodiments of the present disclosure, the liquid crystal display device 1 does not separately include the lower diffusion sheet 14 shown in Figure 1, and the lower diffusion sheet 14, which is located on the lower surface of the first sheet 110, can be replaced with the first diffusion layer 113.

[0049] According to one embodiment, the refractive index of the pyramid pattern layer 111 in the first sheet 110 can be formed to be relatively larger than or equal to the refractive index of the first diffusion layer 113. This is to improve the degree of shielding, and when the refractive index of the first diffusion layer 113, which is the part into which light enters from the first sheet 110, is, for example, 1.49, the refractive index of the pyramid pattern layer 111, which is the part from which light is emitted, can be formed to be 1.49 or higher, thereby reducing the visibility of hot spots and improving shielding performance.

[0050] The second sheet 120 may include a first prism pattern layer 121 on one surface 122a of the second base portion 122, in which a plurality of prism patterns extending parallel to the longitudinal direction of the liquid crystal display device 1 are formed. The cross-section of the first prism pattern layer 121 may be triangular. For example, the plurality of prism patterns included in the first prism pattern layer 121 may be formed with a pitch of c and a height of d. The third sheet 130 may include a second prism pattern layer 131 on one surface 132a of the third base portion 132, in which a plurality of prism patterns extending parallel to the width direction of the liquid crystal display device 1 are formed. The cross-section of the prism patterns formed on the second prism pattern layer 131 may be triangular. For example, the prism patterns formed on the second prism pattern layer 131 may be formed with a pitch of e and a height of f. Here, the multiple prism patterns included in the first prism pattern layer 121 and the multiple prism patterns included in the second prism pattern layer 131 extend in directions orthogonal to each other and can be formed to have the same pitch and height, but are not necessarily limited to this and can vary depending on the embodiment. Furthermore, the other surface 122b of the second base portion 122 of the second sheet 120 may include a second diffusion layer 123 containing multiple optical projection patterns, and the other surface 132b of the third base portion 132 of the third sheet 130 may include a third diffusion layer 133 containing multiple optical projection patterns.

[0051] The second diffusion layer 123 and the third diffusion layer 133 may have substantially the same configuration as the first diffusion layer 113 formed on the other surface 112b of the first base portion 112 of the first sheet 110. The second diffusion layer 123 and the third diffusion layer 133 can each be fabricated using all methods to increase turbidity, including matte treatment to form a rough surface and bead treatment using beads such as glass or polymer to increase turbidity. For example, in various experimental examples including the viewing angle distribution described later in Figures 8 and below, the second diffusion layer 123 may have a haze value of 3%, and the third diffusion layer 133 may have a haze value of 40%.

[0052] The first sheet 110 and the second sheet 120 are connected in a form where the pyramid pattern layer 111 of the first sheet 110 and the second diffusion layer 123 of the second sheet 120 are laminated to each other, and the second sheet 120 and the third sheet 130 can be connected in a form where the first prism pattern layer 121 of the second sheet 120 and the third diffusion layer 133 of the third sheet 130 are laminated to each other. In this case, the second diffusion layer 123 and the third diffusion layer 133 can each be formed with, for example, multiple optical projection patterns (mat patterns) using an adhesive (e.g., adhesive resin), and can be manufactured in a form where they are initially laminated to the other sheet in a state of approximately 50% curing (e.g., semi-cured) rather than 100% curing, and then laminated to the other sheet after 100% curing.

[0053] Figure 7 shows the configuration of an experiment for luminance measurement according to one embodiment of the present disclosure.

[0054] Referring to Figure 7, the configuration of the experiment for measuring luminance may include an optical film 100 and a light measuring device 210. Here, the optical film 100 may be shown with a second sheet 120 and a third sheet 130 bonded together, and the first sheet 110 may be omitted. The light measuring device 210 may be, for example, a high-speed spectroscopic measurement system such as a colorimeter. Although not shown in the drawing, a backlight unit including a light source may be placed on the opposite side of the light measuring device 210 with respect to the optical film 100.

[0055] As shown in Figure 7, the light measuring device 210 can measure light incident on the optical film 100 in the height direction (Z-axis direction). In order to obtain high brightness for the liquid crystal display device 1, the brightness around 0 degrees must be high in the viewing angle data measured by the light measuring device 210. Experimental results showed that the brightness around 0 degrees is greatest when light passing through the second sheet 120 and the third sheet 130 of the optical film 100 is incident at a specific angle C. In other words, the brightness of the liquid crystal display device 1 may be greatest when light passing through the bottom surface of the bonded body of the second sheet 120 and the third sheet 130 (for example, the other surface 122b of the second sheet 120) is incident at a specific angle C.

[0056] For example, in an embodiment in which the second base portion 122 and the third base portion 132 each have a thickness of 24 μm, if the pitch c of the prism pattern of the first prism pattern layer 121 formed on one surface 122a of the second base portion 122 is 50 μm and the height d is 40 μm, and the second diffusion layer 123 has a haze value of 3%, and the pitch e of the prism pattern of the second prism pattern layer 131 formed on one surface 132a of the third base portion 132 is 50 μm and the height f is 40 μm, and the third diffusion layer 133 has a haze value of 40%, then the angle C of the incident light at which the brightness is highest near 0 degrees can be formed at 59 degrees. In other words, the highest brightness value may be obtained when light passing through the lower surface of the bonded material of the second sheet 120 and the third sheet 130 (for example, the other surface 122b of the second sheet 120) is incident at an angle of +59 degrees or -59 degrees.

[0057] According to various embodiments of this disclosure, it is possible to provide an optical film 100 that includes a first sheet 110 designed to improve shielding performance in the direction of incident light, while simultaneously ensuring that light passing through the underside of the laminate of the second sheet 120 and the third sheet 130 (for example, the other side 122b of the second sheet 120) is incident at a specific angle C. An optical film 100 according to one embodiment, as shown in Figures 2 to 6b, includes a first sheet 110 comprising a first base portion 112, a pyramid pattern layer 111 having a plurality of pyramid patterns formed on one surface 112a of the first base portion 112, and a first diffusion layer 113 disposed on the other surface 112b of the first base portion 112, and a second base portion 122 having a plurality of prism patterns formed on one surface of the second base portion 122, which is disposed on top of the first sheet 110, and is arranged in superimposition on the first sheet 110. The second sheet 120 includes a first prism pattern layer 121 and a second diffusion layer 123 formed on the other surface 122b of the second base portion 122, and the third sheet 130 is placed on top of the second sheet 120 and includes a third base portion 132, a second prism pattern layer 131 with a plurality of prism patterns formed on one surface 132a of the third base portion 132 and a third diffusion layer 133 formed on the other surface 132b of the third base portion 132.

[0058] Comparing the embodiment shown in Figure 1 with the embodiments in Figures 2 to 6b, the liquid crystal display device 1 in Figure 1 is equipped only with a simple lower diffusion sheet 14, making it difficult to shield the light source 11a. On the other hand, the direction of light incident on the prism sheets 15 and 16 from the surface P1 facing the prism pattern may not be designed to form an angle that exhibits optimal brightness performance. In contrast, the liquid crystal display devices 1 in Figures 2 to 6b 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, the first sheet 110 has a first diffusion layer 113 on the other surface 112b of the first base portion 112, and a pyramid pattern on one surface 112a, which allows for light diffusion while improving the visibility of hot spots caused by light concentration (improved shielding performance). Furthermore, considering the specifications of the laminated second sheet 120 and third sheet 130, the first sheet 110 can be made to refract and / or reflect light at a point where it contacts the lower surface 122b of the second sheet 120 (for example, P2 in Figure 2) so that the light is incident toward the second sheet 120 at a specific angle, by appropriately adjusting the specifications of the first diffusion layer 113 formed on the other surface 112b of the first base portion 112 and the pyramid pattern formed on one surface 112a (improvement of brightness performance).

[0059] According to various embodiments, the refractive index of the pyramid pattern layer 111 and the second diffusion layer 123 can be formed with a deviation of 0.05 or less. Forming the refractive index of the pyramid pattern layer 111 and the second diffusion layer 123 with a deviation of 0.05 or less may be advantageous in maintaining the light recycling characteristics while preventing damage to the pyramid pattern during bonding. According to various embodiments, the refractive index of the first prism pattern layer 121 and the third diffusion layer 133 can be formed with a deviation of 0.05 or more. Forming the refractive index of the first prism pattern layer 121 and the third diffusion layer 133 with a deviation of 0.05 or more can minimize the reduction in brightness.

[0060] According to one embodiment, if the pitch ratio of the pyramid pattern layer 111 of the first sheet 110 to the pitch of the first prism pattern layer 121 and the second prism pattern layer 131 included in the second sheet 120 and the third sheet 130 is formed as an integer multiple, a moiré phenomenon may occur. Therefore, the pitch of the pyramid pattern layer 111 of the first sheet 110 can be configured to have a deviation of a predetermined multiple from an integer multiple of the pitch of the first prism pattern layer 121 and the second prism pattern layer 131 included in the second sheet 120 and the third sheet 130. For example, if the pitches of the first prism pattern layer 121 and the second prism pattern layer 131 included in the second sheet 120 and the third sheet 130 are each formed at 50 μm, the pitch p of the pyramid pattern layer 111 of the first sheet 110 can be formed at 85 μm, resulting in a multiple deviation of 15%.

[0061] Figures 8a and 8b show the optical characteristics between the liquid crystal display device 1 disclosed in the embodiment of Figure 1 and the liquid crystal display device 1 disclosed in the embodiments of Figures 2 to 6b. Figure 9 is a graph showing the optical characteristics between the liquid crystal display device 1 disclosed in the embodiment of Figure 1 and the liquid crystal display device 1 disclosed in the embodiments of Figures 2 to 6b. Figure 9 may be a graph showing the illuminance of Figures 8a and 8b.

[0062] Here, Figure 8a shows the illuminance measurement results for investigating the visibility of hot spots due to the presence of light sources 11a in a liquid crystal display device 1 including the configuration of the diffusion sheet 14 disclosed in the embodiment of Figure 1. Figure 8b shows the illuminance measurement results for investigating the visibility of hot spots due to the presence of light sources 11a in a liquid crystal display device 1 including the configuration of the optical film 100 disclosed in the embodiments of Figures 2 to 6b. Looking at Figure 8a, it can be confirmed that multiple light sources 11a separated by a predetermined interval are visible. In comparison, looking at Figure 8b, it can be confirmed that the light sources 11a appear slightly shifted compared to Figure 8a, resulting in lower visibility (higher degree of shading), a decrease in the distribution of dark areas 11b between the light sources 11a, and an increase in the degree of diffusion.

[0063] Referring to Figures 8a, 8b, and 9 together, the illuminance was measured for each of the embodiments in Figure 1 and Figures 2 to 6b. The results confirmed that the optical film 100 according to the embodiments in Figures 2 to 6b has a higher shielding effect.

[0064] Figures 10a and 10b show other optical characteristics between the liquid crystal display device 1 disclosed in the embodiment of Figure 1 and the liquid crystal display device 1 disclosed in the embodiment of Figure 2. Figure 11 is a graph showing other optical characteristics between the liquid crystal display device 1 disclosed in the embodiment of Figure 1 and the liquid crystal display device 1 disclosed in the embodiment of Figure 2. Figure 11 may be a graph showing the viewing angles of Figures 10a and 10b.

[0065] Here, Figure 10a shows the viewing angle distribution and luminance measurement results at point P1 of the liquid crystal display device 1, including the configuration of the diffusion sheet 14 disclosed in the embodiment of Figure 1. Figure 10b shows the viewing angle distribution and luminance measurement results at point P2 of the liquid crystal display device 1, including the configuration of the optical film 100 disclosed in the embodiments of Figures 2 to 6b. In Figures 10a and 10b, brightness can be displayed with various color distributions. Referring to Figures 10a and 10b, it can be confirmed that the luminance is high in the center and gradually decreases from the center towards the periphery. However, in Figure 10b, it can be confirmed that the luminance increases from the periphery towards the edge.

[0066] Referring to Figures 10a, 10b, and 11 together, the results of measuring the viewing angle and brightness for each embodiment of Figure 1 and Figures 2 to 6b show that the optical film 100 according to the embodiments of Figures 2 to 6b exhibits higher brightness at angles greater than +59 degrees or less than -59 degrees. In other words, the optical film 100 examined in the embodiments of Figures 2 to 6b can exhibit higher brightness performance than the embodiment of Figure 1 within a specific angular range.

[0067] The optical films and backlight units containing the same in the various embodiments of the present disclosure described above are not limited to the embodiments and drawings described above, and a person with ordinary skill in the art to which the present invention belongs will recognize that various substitutions, modifications and changes are possible within the technical scope of the present disclosure. [Explanation of Symbols]

[0068] 1:LCD display device 10: Backlight Unit 11a: Light source 12: Reflective sheet 13: Color conversion sheet 14: Lower diffusion sheet 15: First prism sheet 16: Second prism sheet 17: Upper diffusion sheet 20: LCD panel 100: Optical film 110: First seat 111: Pyramid Pattern Layer 112: First base section 113: First diffusion layer 120: Second seat 121: First prism pattern layer 122: Second base section 130: Third seat 131: Second prism pattern layer 123: Second diffusion layer 132: Third base section 133: Third Diffusion Layer

Claims

1. A first sheet comprising a first base portion, a pyramid pattern layer having a plurality of pyramid patterns formed on one surface of the first base portion, and a first diffusion layer having a plurality of optical projection patterns formed on the other surface of the first base portion. A second sheet, placed on top of the first sheet, comprising a second base portion, a first prism pattern layer on one surface of the second base portion having a plurality of triangular prism-shaped first prism patterns extending along the second base portion and having triangular cross-sections when viewed from the direction of extension, and a second diffusion layer on the other surface of the second base portion having a plurality of adhesive optical projection patterns, and The third sheet is positioned on top of the second sheet and includes a third base portion, a second prism pattern layer on one surface of the third base portion having a plurality of triangular prism-shaped second prism patterns that extend along the third base portion and have a triangular cross-section when viewed from the direction of extension, and a third diffusion layer on the other surface of the third base portion having a plurality of adhesive optical projection patterns. The refractive index of the pyramidal pattern layer is formed to be greater than or equal to the refractive index of the first diffusion layer, and the haze value of the first diffusion layer is 15% or more. The first sheet, the second sheet, and the third sheet are laminated together by a plurality of optical projection patterns having adhesion between the second and third diffusion layers. The refractive index of the pyramidal pattern layer and the second diffusion layer is formed with a deviation of 0.05 or less. An optical film in which the refractive indices of the first prism pattern layer and the third diffusion layer are formed with a deviation of 0.05 or more.

2. The optical film according to claim 1, wherein the plurality of optical projection patterns of the first diffusion layer include an adhesive and have a matte pattern including a plurality of protrusions projecting from the first base portion.

3. The optical film according to claim 1, wherein the plurality of pyramidal patterns are formed by intaglio.

4. The optical film according to claim 1, wherein the plurality of pyramidal patterns have a vertical cross-section parallel to the height direction of the optical film that forms an isosceles triangle.

5. The optical film according to claim 1, wherein the plurality of pyramid patterns have vertex angles of 60 degrees or more and 160 degrees or less.

6. The optical film according to claim 5, wherein the plurality of pyramid patterns have vertex angles of 80 degrees or more and 130 degrees or less.

7. The optical film according to claim 1, wherein the pitch of the pyramid pattern is formed to be shifted by a non-integer multiple from the pitch of the first prism pattern and the second prism pattern.

8. light source, Color conversion sheet, and The optical film placed on top of the aforementioned color conversion sheet is A fourth sheet comprising a fourth base portion, a pyramid pattern layer having a plurality of pyramid patterns with vertex angles of 60 degrees or more and 160 degrees or less formed on one surface of the fourth base portion, and a fourth diffusion layer having a plurality of optical projection patterns formed on the other surface of the fourth base portion. A fifth sheet, placed on top of the fourth sheet, comprising a fifth base portion, a third prism pattern layer on one surface of the fifth base portion having a plurality of triangular prism-shaped third prism patterns extending along the fifth base portion and having triangular cross-sections when viewed from the direction of extension, and a fifth diffusion layer on the other surface of the fifth base portion having a plurality of adhesive optical projection patterns, and The sixth sheet is positioned on top of the fifth sheet and includes a sixth base portion, a fourth prism pattern layer on one surface of the sixth base portion having a plurality of triangular prism-shaped fourth prism patterns that extend along the sixth base portion and have a triangular cross-section when viewed from the direction of extension, and a sixth diffusion layer on the other surface of the sixth base portion having a plurality of adhesive optical projection patterns. The refractive index of the pyramidal pattern layer is formed to be greater than or equal to the refractive index of the fourth diffusion layer, and the haze value of the fourth diffusion layer is 15% or more. A backlight unit comprising an optical film made of a single lamination sheet by a plurality of optical protrusion patterns having adhesive properties for the fifth and sixth diffusion layers, wherein the fourth, fifth, and sixth sheets are the fourth, fifth, and sixth sheets.

9. The backlight unit according to claim 8, wherein the plurality of optical projection patterns of the fourth diffusion layer include an adhesive and have a matte pattern including a plurality of protrusions projecting from the fourth base portion.

10. The backlight unit according to claim 8, wherein the plurality of pyramidal patterns are formed by intaglio.

11. The backlight unit according to claim 10, wherein the pitch of the pyramid pattern is formed to be offset by a non-integer multiple from the pitch of the third prism pattern and the fourth prism pattern.

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