TWI852062B - Optical film and back light unit including the same - Google Patents

Abstract

The backlight unit of multiple embodiments of the present invention is characterized in that it may include: a light source; a color change sheet, which is used to change the color of light released from the light source; and at least one optical film, which is arranged on the color change sheet, at least one of the optical films includes: a first sheet, which includes a first substrate portion, a first pattern layer and a second pattern layer, the first pattern layer is arranged on one side of the first substrate portion and includes a first pattern, the second pattern layer is arranged on the other side of the first substrate portion and includes a second pattern different from the first pattern; and a second sheet, which includes a second substrate portion, a third pattern layer and a fourth pattern layer, the third pattern layer is arranged on one side of the second substrate portion and includes the first pattern, the fourth pattern layer is arranged on the other side of the second substrate portion and includes the second pattern, and the first sheet and the second sheet of the optical film are bonded.

Description

Optical film and backlight unit including the same

Multiple embodiments of the present invention relate to an optical film and a backlight unit including the same.

Typically, a liquid crystal display (LCD) may include a backlight unit for uniformly irradiating light to the entire screen of an electronic device. According to the position of the light source, the backlight unit is divided into an edge type in which the light is located on the side of the substrate including the display surface (a light guide plate is required to convert the linear light of the light into surface light) and a direct type in which the light is located below the substrate including the display surface (no light guide plate is required). Among them, the direct type backlight unit has a higher light utilization efficiency and a simple structure, and the size of the substrate is not limited, so it is generally widely used in liquid crystal display devices. A general direct type backlight unit may include an optical film having a light source, a diffuser, and a prism. After being diffused by the diffuser, the light emitted from the light source can be transmitted to the liquid crystal panel through the optical film disposed on the upper part.

As a light source, a liquid crystal display device using a small light emitting diode (LED) and/or a micro light emitting diode is actively utilized, which has the advantages of miniaturization, light weight and/or low power consumption. Each chip of a small light emitting diode or a micro light emitting diode can constitute an individual pixel or light source, thereby removing the restrictions on the size and shape of the display, and this can embody a clearer picture quality than the case of using existing light sources.

We are actively conducting research on backlight units that improve the light characteristics of LEDs while miniaturizing the size of LED chips.

A direct-type backlight unit using a small LED or a micro LED as a light source may use a diffusion sheet for converting light from a point light source into a surface light source. The direct-type backlight unit arranges the light source on a plane, and therefore, in order to prevent the shape of the light source (e.g., the shape of the small LED or the micro LED) from being displayed on the liquid crystal panel, a thick diffusion sheet or a structure in which a plurality of diffusion sheets are stacked may be used.

According to one embodiment, in addition to or instead of the diffusion sheet, a shielding sheet for shielding a hot spot as a phenomenon in which the shape of the light source appears on the liquid crystal panel may be included.

The shielding sheet (and/or diffusion sheet) may have a certain thickness in order to prevent the shape of the light source from being displayed on the liquid crystal panel, so the thinning of the liquid crystal display device is limited. On the contrary, when the thickness of the shielding sheet is too thick, the brightness of the liquid crystal display device may be greatly reduced. As described above, in the backlight unit having the shielding sheet, the thickness of the shielding sheet may be related to the shielding performance and the brightness performance, wherein the shielding performance and the brightness performance may be in a trade-off relationship.

The present invention provides, through a plurality of embodiments, an optical film for a liquid crystal display device having excellent performance (hereinafter referred to as "shielding performance") in preventing the shape of a light source from appearing on a liquid crystal panel even without using a thicker diffusion sheet.

The backlight unit of multiple embodiments of the present invention is characterized in that it may include: a light source; a color change sheet, which is used to change the color of light released from the light source; and at least one optical film, which is arranged on (over) the color change sheet, at least one of the optical films includes: a first sheet, which includes a first substrate portion, a first pattern layer and a second pattern layer, the first pattern layer is arranged on one side of the first substrate portion and includes a first pattern, the second pattern layer is arranged on the other side of the first substrate portion and includes a second pattern different from the first pattern; and a second sheet, which includes a second substrate portion, a third pattern layer and a fourth pattern layer, the third pattern layer is arranged on one side of the second substrate portion and includes the first pattern, the fourth pattern layer is arranged on the other side of the second substrate portion and includes the second pattern, and the first sheet and the second sheet of the optical film are laminated.

According to various embodiments of the present invention, the present invention can provide an optical film and a backlight unit including the same, wherein the backlight unit has a shielding sheet to which multiple films are bonded, and therefore, even without a thick sheet with a relatively high thickness, the shielding performance is relatively good.

The effects that can be obtained in the present invention are not limited to the effects mentioned above, and those skilled in the art can clearly understand other effects not mentioned from the following description.

It should be understood that the multiple embodiments and terms used in this document do not limit the technical features recorded in this document to specific embodiments, but include multiple changes, equivalent technical solutions or alternative technical solutions of the corresponding embodiments. In connection with the description in the figures, similar figure marks may be used for similar or related structural elements. Unless the context clearly stipulates otherwise, the singular form of the noun corresponding to an item may include one or more of the items.

According to a plurality of embodiments, each structural element (e.g., a film or a sheet) in the described structural elements may include a single or multiple individuals, and a portion of the multiple individuals may also be separately configured in other structural elements. According to a plurality of embodiments, one or more structural elements or actions in the corresponding structural elements may be omitted, or one or more other structural elements or actions may be added. Alternatively or additionally, a plurality of structural elements (e.g., a film or a sheet) may be combined into one structural element. In this case, the combined structural element may implement one or more functions of each structural element in the plurality of the structural elements in the same or similar manner by the corresponding structural elements in the plurality of the structural elements before the combination.

The embodiments are described with reference to the attached drawings. In the process of describing the embodiments, the same names and the same marks are used for the same structures, and additional descriptions thereof are omitted. In addition, in the process of describing the embodiments of the present invention, the same names and the same marks are used for the structural elements with the same functions, which is substantially completely different from the current technology.

According to various embodiments, terms such as “including” or “having” are used to specify the existence of features, numbers, steps, actions, structural elements, components, or combinations thereof described in the specification, but do not preclude the existence or additional possibility of one or more other features, numbers, steps, actions, structural elements, components, or combinations thereof.

FIG. 1 is a diagram showing a liquid crystal display device including a diffusion sheet according to an embodiment.

1 , a liquid crystal display device 1 (or a liquid crystal display (LCD)) may include a backlight unit 10 and a liquid crystal panel 20. According to various embodiments, the backlight unit 10 may be disposed toward the rear surface (the surface facing the −Z direction) of the liquid crystal panel 20 to emit light to the liquid crystal panel 20. The backlight unit 10 may include a substrate 11, a color conversion sheet 13, diffusion sheets 14, 17, and prism sheets 15, 16, and the substrate 11 includes a light source 11a. Although not shown, the backlight unit 10 may also include a reflective polarizer.

According to various embodiments, the light source 11a is a structure for emitting light toward the back side of the liquid crystal panel 20, and can be disposed on one side of the substrate 11. The light source 11a can correspond to a light emitting diode (LED, hereinafter referred to as "light emitting diode"). For example, the light source 11a can include a plurality of light emitting diode chips 11a that emit light. According to the size of the LED chip, the LED can be divided into large LED (chip size: 1000μm or more), middle LED (chip size: 300μm-500μm), small LED (chip size: 200μm-300μm), mini LED (chip size: 100μm-200μm) and micro LED (chip size: 100μm or less). The LED may include materials such as InGaN and GaN. The light emitted from the light source 11a may be emitted toward the direction of the liquid crystal panel 20 (Z direction). The light emitted from the light source 11a may be incident on the diffusion sheet 14 through the color conversion sheet 13.

According to various embodiments, a reflective sheet 12 may be formed on the surface of the substrate 11. The reflective sheet 12 may include materials such as BaSo ₄ , TiO ₂ , CaCo ₃ , SiO ₂ , Ca ₃ (So ₄ ) ₂ , and may include materials such as Ag, and may be coated or spread on the substrate 11 between the light sources 11a and 11a. The reflective sheet 12 may play a role in reflecting the light emitted from the light source 11a through the color change sheet 13 , the diffusion sheets 14 , 17 , and the prism sheets 15 , 16 and reflected to the side of the substrate 11 by interface reflection back to the emission direction of the light. Therefore, the loss of light may be minimized. That is, the reflective sheet 12 may implement light recycling.

According to various embodiments, the color change sheet 13 can change the color of the light emitted from the light source 11a. As an example, the light of the small LED or micro LED can be blue light (450nm). In this case, the blue light needs to be changed into white light. The color change sheet 13 can pass the blue light emitted from the light source 11a and change the blue light into white light.

According to various embodiments, the diffusion sheets 14 and 17 can uniformly disperse the light incident from the color change sheet 13. The diffusion sheets 14 and 17 can be coated with a curable resin solution (for example, one or more of polyurethane acrylate, epoxy acrylate, acrylate, acrylate and free radical generating monomer are selected to be used alone or in combination) to which light diffusion agent beads are added, and light diffusion is induced by the light diffusion agent beads. In addition, the diffusion sheets 14 and 17 can be formed with protrusion patterns (or protrusions) of uniform or non-uniform size (for example, spherical) to promote light diffusion.

According to various embodiments, the diffusion sheets 14 and 17 may include a lower diffusion sheet 14 and an upper diffusion sheet 17. The lower diffusion sheet 14 may be disposed between the color change sheet 13 and the prism sheet 15, and the upper diffusion sheet 17 may be disposed between the prism sheet 16 and the liquid crystal panel 20. When the backlight unit 10 also includes a reflective polarizer, the upper diffusion sheet 17 may be disposed between the prism sheet 16 and the reflective polarizer.

According to various embodiments, the prism sheets 15 and 16 can utilize an optical pattern formed on the surface to collect incident light and then emit it to the liquid crystal panel 20. The prism sheets 15 and 16 can include a light-transmitting base film and a prism pattern layer formed on the upper surface (the surface facing the +Z axis direction) of the base film. The prism pattern layer can be formed into an optical pattern layer in the form of a triangular array with a tilted surface at a specified angle (e.g., a 45° tilted surface) to increase the brightness in the surface direction. The prism pattern of the prism pattern layer can be in the shape of a triangular prism, and one surface of the triangular prism can face the base film.

According to one embodiment, the prisms 15 and 16 may include a first prism 15 and a second prism 16 to form a composite prism structure. The second prism 16 may be overlapped and arranged on the upper surface of the first prism 15. In the first prism 15, a plurality of first prism patterns may be arranged side by side with each other. Each first prism pattern may be a structure extending in one direction. For example, the vertex line 15a of each first prism pattern may extend in the direction of the X-axis. Similarly, in the second prism 16, a plurality of second prism patterns may also be arranged side by side with each other. Each second prism pattern may be a structure extending in one direction. For example, the vertex line 16a of each second prism pattern may extend toward a direction perpendicular to the X-axis and the Z-axis (hereinafter referred to as the "Y-axis"). For the sake of explanation, the extending direction of the first prism pattern and the extending direction of the second prism pattern are toward the X-axis and the Y-axis, but this is not limited to the embodiment shown, and may also be toward other directions except the X-axis or the Y-axis.

According to various embodiments, a reflective polarizer (not shown) may be disposed above the prisms 15, 16 and the upper diffuser 17. For the light collected by the prisms 15, 16 and diffused by the upper diffuser, a portion of the polarized light is transmitted and the other polarized light is reflected from the lower portion.

According to various embodiments, the liquid crystal panel 20 can bend the light emitted from the light source 11a into a predetermined pattern according to an electrical signal. The bent light can form a screen through a color filter and a bias filter disposed on the front surface of the liquid crystal panel 20.

FIG. 2 is a diagram showing a liquid crystal display device including a backlight unit having a plurality of film-laminated shielding sheets according to various embodiments of the present invention.

2, a liquid crystal display device 1 (or a liquid crystal display device (LCD)) of an embodiment of the present invention may include a backlight unit 10 and a liquid crystal panel 20. The backlight unit 10 may include a substrate 11, a color change sheet 13, prism sheets 15 and 16 of an optical film 100, and a diffusion sheet 17. The substrate 11 includes a light source 11a. According to an embodiment, a reflective sheet 12 may be formed on one side of the light source 11a.

According to one embodiment, the backlight unit 10 may omit at least one of the structural elements (e.g., the diffusion sheet 17), or may add one or more other structural elements (e.g., a reflective polarizer (not shown)). The description of the parts that overlap with FIG. 1 is omitted below. The liquid crystal display device 1 of the present invention is characterized in that at least two optical films can be provided. Among them, at least two of the optical films 100 can replace the lower diffusion sheet 14 or they can be additionally provided. In the following, in the description of the attached drawings of the present invention, an example can be given of providing at least one optical film on one side to replace the lower diffusion sheet 14.

In the present invention, the "optical film" may be a form in which two shielding sheets are laminated to each other, with a first pattern provided on one side of a light-transmitting base film (hereinafter referred to as the "substrate portion") and a second pattern also provided on the other side of the substrate portion. Furthermore, in the present invention, as shown in FIG. 2 , at least one optical film may include two optical films. However, it is not limited thereto, and more than three optical films may be included depending on the circumstances. In the attached figure of FIG. 2 , it is slightly enlarged for the convenience of explanation, and two very thin sheets 110 and 120 of different thickness are laminated to each other to form a first optical film 100, and two other different sheets 210 and 220 form a second optical film 200.

In the present invention, "lamination" can be performed by attaching an adhesive to at least one of two different sheets. Compared with the embodiment in which the sheets are simply laminated without lamination, the optical film in the lamination state is thinner and can provide a backlight unit with excellent shielding performance.

According to various embodiments of the present invention, in the case where four different shielding sheets 110, 120, 130, 140 form two optical films, the base material portions of the first sheet 110 and the second sheet 120 may have a thickness of 50 μm respectively, and are bonded together to form the first optical film 100, and the base material portions of the third sheet 210 and the fourth sheet 220 may have a thickness of 75 μm respectively, and are bonded together to form the second optical film 200. The first optical film 100 and the second optical film 200 of the present invention can replace the lower diffusion sheet 14 or be additionally provided on the color change sheet 13 in a mutually stacked state. For example, compared with the embodiment of a simple stack of a first sheet 110 and a second sheet 120 with a thickness of 50 μm and a third sheet 210 and a fourth sheet 220 with a thickness of 75 μm (hereinafter referred to as "optical film in non-bonded form"), the optical films 100 and 200 of the various embodiments of the present invention (hereinafter referred to as "optical film in bonded form") can have a form that is thinner than several μm, and have high rigidity and can exert excellent shielding performance. For example, according to the simulation results implemented by the applicant, compared with the optical film of the four different shielding sheets 110, 120, 130, 140 having a thickness of 405 μm and a shielding degree of 2.1, the optical film in bonded form has a thickness of 402 μm, thereby having a thinner thickness and a higher shielding degree of 2.3. Furthermore, in terms of brightness characteristics, the optical film in the laminated form has a brightness of 94.8%, compared to the 92.0% brightness of the optical film in the unlaminated form, thereby having excellent performance in terms of brightness.

FIG. 3 is a side view showing a shielding sheet of multiple films bonded together according to multiple embodiments of the present invention, and FIG. 4 is a three-dimensional view showing a shielding sheet of multiple films bonded together according to multiple embodiments of the present invention.

In the present invention, at least one of the optical films may include a first optical film 100 and a second optical film 200 .

Specifically, the first optical film 100 may include: a first sheet 110, which includes a first substrate portion 112, a first pattern layer 111 and a second pattern layer 113, wherein the first pattern layer 111 is disposed on one side of the first substrate portion 112 and includes a first pattern, and the second pattern layer 113 is disposed on the other side of the first substrate portion 112 and includes a second pattern different from the first pattern; and a second sheet 120, which includes a second substrate portion 122, a third pattern layer 121 and a fourth pattern layer 123, wherein the third pattern layer 121 is disposed on one side of the second substrate portion 122 and includes the first pattern, and the fourth pattern layer 123 is disposed on the other side of the second substrate portion and includes the second pattern.

The second optical film 200 includes: a third sheet 210, which includes a third substrate portion 212, a fifth pattern layer 211 and a sixth pattern layer 213, wherein the fifth pattern layer 211 is disposed on one side of the third substrate portion 212 and includes a first pattern, and the sixth pattern layer 213 is disposed on the other side of the third substrate portion 212 and includes a second pattern different from the first pattern; and a fourth sheet 220, which includes a fourth substrate portion 222, a seventh pattern layer 221 and an eighth pattern layer 223, wherein the seventh pattern layer 221 is disposed on one side of the fourth substrate portion 222 and includes the first pattern, and the eighth pattern layer 223 is disposed on the other side of the fourth substrate portion 222 and includes the second pattern.

The thickness of the third substrate portion 212 and the fourth substrate portion 222 may be different from the thickness of the first substrate portion 112 and the second substrate portion 122. For example, as shown in FIG. 2 , the thickness of the third substrate portion 212 and the fourth substrate portion 222 may be 75 μm, and the thickness of the first substrate portion 112 and the second substrate portion 122 may be 50 μm. Therefore, overall, the thickness of the second optical film 200 may be greater than the thickness of the first optical film 100. When the thickness of the substrate portion is thinner, the heat generated from the light source 11a may be damaged, thereby causing uneven expansion of the sheet (sheet creep phenomenon). Therefore, according to an embodiment of the present invention, the uneven expansion of the sheet can be prevented and the reliability of the product can be improved by making the thickness of the second optical film 200 close to the light source 11a greater than the thickness of the first optical film 100. According to one embodiment, the refractive index of each layer can be used to improve the shielding performance of the first optical film 100. For example, the first optical film 100 can be formed such that the refractive index of the first pattern layer 111 is smaller than the refractive index of the second pattern layer 113. In addition, the refractive index of the third pattern layer 121 can be greater than the refractive index of the fourth pattern layer 123. The refraction angle of light can be increased to improve the shielding performance by making the refractive index of the third pattern layer 121 as the light emitting layer greater than the refractive index of the fourth pattern layer 123 as the light incident layer. However, in the case where the first pattern layer 111 as the uppermost layer corresponds to the light emitting layer, in order to prevent the brightness from being significantly reduced, the refractive index of the first pattern layer 111 can be smaller than the refractive index of the second pattern layer 113. Specifically, when the refractive index of the first substrate portion 112 and the second substrate portion 122 is approximately 1.60 to 1.70, the refractive index of the first pattern layer 111 may be approximately 1.45 to 1.50, and the refractive index of the second pattern layer 113 may be approximately 1.50 to 1.55 greater than the refractive index of the first pattern layer 113. Furthermore, the refractive index of the third pattern layer 121 may be approximately 1.65 to 1.70, and the refractive index of the fourth pattern layer 123 may be approximately 1.45 to 1.50.

According to one embodiment, when the optical film includes the first optical film 100 and the second optical film 200, the refractive index of each layer can be used to improve the shielding performance of the first optical film 100 and the second optical film 200. For example, the first optical film 100 can be formed such that the refractive index of the first pattern layer 111 is smaller than the refractive index of the second pattern layer 113. In addition, the refractive index of the third pattern layer 121 can be greater than the refractive index of the fourth pattern layer 123. The second optical film 200 can be formed such that the refractive index of the fifth pattern layer 211 is greater than the refractive index of the sixth pattern layer 213, and the refractive index of the seventh pattern layer 221 is greater than the refractive index of the eighth pattern layer 223. The refraction angle of light can be increased to improve the shielding performance by making the refractive index of the third pattern layer 121, the fifth pattern layer 211 and the seventh pattern layer 221 as the light emitting layer greater than the refractive index of the fourth pattern layer 123, the sixth pattern layer 213 and the eighth pattern layer 223 as the light incident layer. However, when the first pattern layer 111 as the uppermost layer corresponds to the light emitting layer, the refractive index of the first pattern layer 111 can be smaller than the refractive index of the second pattern layer 113 to prevent a significant decrease in brightness. For example, when the refractive index of the first substrate portion 112 and the second substrate portion 122 of the first optical film 100 is approximately 1.60 to 1.70, the refractive index of the first pattern layer 111 may be 1.45 to 1.50, and the refractive index of the second pattern layer 113 may be approximately 1.50 to 1.55 greater than the refractive index of the first pattern layer 113. Furthermore, the refractive index of the third pattern layer 121 may be approximately 1.65 to 1.70, and the refractive index of the fourth pattern layer 123 may be approximately 1.45 to 1.50. In the second optical film 200, when the refractive index of the third substrate portion 212 and the fourth substrate portion 222 is approximately 1.60 to 1.70, the refractive index of the fifth pattern layer 211 can be approximately 1.65 to 1.70, and the refractive index of the sixth pattern layer 213 can be approximately 1.50 to 1.55. Moreover, the refractive index of the seventh pattern layer 221 can be approximately 1.65 to 1.70, and the refractive index of the eighth pattern layer 223 can be approximately 1.45 to 1.50. In addition to the sheet including the light emitting layer (e.g., the first pattern layer 111) forming the uppermost layer, the remaining sheet portion is formed such that the refractive index of the light emitting layer is greater than the refractive index of the light incident layer, thereby improving the shielding performance.

FIG. 5 is a diagram showing a sheet included in an optical film according to various embodiments of the present invention.

According to an embodiment, a shielding sheet included in the optical film can be taken as an example of the first sheet 110 of the first optical film 100, and the description of the first sheet 110 can also be applied to the remaining sheets (the second sheet 120, the third sheet 210, and the fourth sheet 220).

According to various embodiments, a shielding sheet 110 may include: a first substrate portion 112; a first pattern layer 111 including a first pattern disposed on one surface of the substrate portion 112; and a second pattern layer 113 including a second pattern disposed on the other surface of the substrate portion 112. The first pattern layer 111 may be disposed on a surface facing the +Z direction of the substrate portion 112, and the second pattern layer 113 may be disposed on a surface facing the -Z direction of the substrate portion 112.

According to one embodiment, the substrate portion 112 can be used to support the first pattern layer 111 and/or the second pattern layer 113. For example, the substrate portion 112 can be formed of a transparent material capable of transmitting light, and the material (for example) can include polycarbonate, polysulfone, polyacrylate, polystyrene, polyvinyl chloride, polyvinyl alcohol, polynorbornene, and polyester. As a specific example, the substrate portion 112 can be formed of at least one of polyethylene terephtalate and polyethylene naphthalate.

According to various embodiments, the first pattern layer 111 may include a plurality of prism patterns having parallel pattern directions toward a first direction (eg, direction A). The cross-section of each prism pattern may be a triangle. The plurality of prism patterns may be designed to have a size that gradually decreases toward the +Z axis.

According to multiple embodiments, the second pattern layer 113 may include multiple pyramidal patterns having multiple rows in a second direction (e.g., B direction) and multiple rows in a third direction (e.g., B' direction) perpendicular to the second direction. The cross-section of each pyramidal pattern may be a triangle or a trapezoid. When observed from below the second pattern layer 113 (when observed toward the +Z axis), the multiple pyramidal patterns may be designed as intaglio patterns. According to one embodiment, the second direction (e.g., B direction) may be oriented in a direction different from the first direction (e.g., A direction). According to one embodiment, the angle (φ) formed by the second direction (e.g., B direction) and the first direction (e.g., A direction) may be -5˚ to +5˚. Since the second direction (eg, B direction) forms -5˚ to +5˚ with the first direction (eg, A direction), the occurrence of moire can be prevented. Each pyramid pattern can be engraved and designed to gradually increase in size toward the -Z axis.

According to one embodiment, for example, the thickness of the substrate portion 112 may be approximately 50 μm to 75 μm. However, the thickness of the base film 112 is not limited to this example, and may be changed to a variety of appropriate thicknesses to support the first pattern layer 111 and the second pattern layer 113.

The first shielding sheet 110 of the present invention can be provided with pattern layers (first pattern layer 111, second pattern layer 113) on one side and the other side (i.e., on both sides) based on the substrate portion 112, thereby increasing the light diffusion effect and reducing light interference and color unevenness. According to one embodiment, the first pattern layer 111 and the second pattern layer 113 can be coated with an ultraviolet (UV) curable resin solution on one side (or the other side) of the substrate portion 112 and irradiated with light to achieve curing, thereby achieving micro patterning.

According to various embodiments, in relation to the light diffusion effect, light incident on the second pattern layer 113 may be diffused by the plurality of pyramidal patterns formed on the second pattern layer 113. The second pattern layer 113 may transmit light in the emission direction (Z direction) of the light emitted from the light source 11a. In this process, light loss may be minimized and brightness reduction may be minimized by bending light bent on the interface of the pyramidal pattern and reflected light based on interface reflection, etc. The pyramidal pattern formed on the second pattern layer 113 may include a plurality of (e.g., M×N) pyramids, and may form a pyramidal pattern having M columns and N rows, so that at least a portion may overlap with the light source 11a formed on the substrate 11.

According to various embodiments, the shielding sheet 110 may include: a first pattern layer 111, which is formed with a prism pattern having a predetermined height a (or thickness) and a spacing b; and a second pattern layer 113, which is formed with a pyramid pattern having a predetermined height c (or thickness) and a spacing d.

According to one embodiment, in the first pattern layer 111, the height a and the spacing b of the prism pattern can be defined based on the first vertex angle θ1. The first vertex angle θ1 can be defined as the angle between two opposing surfaces of the three surfaces that form the prism pattern with a triangular cross-section. For example, the first vertex angle θ1 can be 70° to 120°. Moreover, the height a and the spacing b of the prism pattern with a triangular cross-section can be defined according to a ratio based on the first vertex angle θ1. For example, when the first vertex angle θ1 is 90°, the ratio of the height a and the spacing b of the prism pattern can be defined as 1:2. For example, the height a of the prism pattern can be approximately 5μm to 35μm, and the spacing b of the prism pattern can be approximately 10μm to 70μm. More specifically, preferably, the height a of the prism pattern may be approximately 25 μm, and the spacing b of the prism pattern may be approximately 50 μm.

According to another embodiment, in the second pattern layer 113, the height c and the spacing d of the pyramidal pattern can be defined based on the second vertex angle θ2. The second vertex angle θ2 can be defined as the angle between two facing surfaces of the four surfaces forming the pyramidal pattern with a trapezoidal cross section. For example, the second vertex angle θ2 can be 90° to 150°. Within the specified range, the greater the vertex angle of the pyramidal pattern, the further the diffusion of light incident on the shielding sheet 110 can be reduced. When the vertex angle is reduced, the diffusion of light can increase and increase the brightness loss. Moreover, the height c and the spacing d of the pyramidal pattern with a trapezoidal cross section can be defined according to a ratio based on the second vertex angle θ2. For example, when the top angle is 130°, the ratio of the height c and the spacing d of the pyramid pattern can be 1:4. For example, the height c of the pyramid pattern can be about 5 μm to 15 μm, and the spacing d of the pyramid pattern can be about 20 μm to 60 μm. More specifically, preferably, the height a of the pyramid pattern can be about 10 μm, and the spacing d of the pyramid pattern can be about 40 μm. Multiple pyramid patterns with such height c and spacing d can be regularly arranged under the shielding sheet 110. A plurality of pyramidal patterns may correspond 1:1 to a light source (e.g., light source 11a in FIG. 3 ) formed on a substrate (e.g., substrate 11 in FIG. 3 ), or may be arranged in a form in which at least a portion of the light sources overlap, thereby diffusing a point light source emitted from the light source into a surface light source. On the other hand, through the diffusion effect of the optical film 100 , the light from the light source 11a undergoes light separation (or light diffusion), thereby reducing hot spot visibility (HSV; hot spot visibility) caused by light concentration.

FIG6a is a graph showing the illumination, beam width, standard deviation, and brightness value at each vertex angle of the prism of multiple embodiments of the present invention, and FIG6b is a graph showing the standard deviation at each vertex angle of the prism of multiple embodiments of the present invention.

Referring to FIG. 6a and FIG. 6b, when the second vertex angle θ2 of the pyramidal pattern of the second pattern layer 113 is fixed and the first vertex angle θ1 of the prism pattern of the first pattern layer 111 is changed, the illumination, beam width, standard deviation and brightness value can be confirmed. In the figures of the various embodiments of the present invention including FIG. 6a, the beam width can be the width of the light passing through the shielding sheet diffused based on the light source (light-emitting diode). The larger the beam width, the light will undergo light separation (or light diffusion), and therefore, the hot spot visibility (HSV; hot spot visibility) caused by the concentration of light is improved, so that the light characteristics are better. In the figures of the various embodiments of the present invention including FIG. 6a, the standard deviation is an indicator of the uniformity of light distribution, and the higher the value, the greater the deviation of the light distribution. When the deviation of the light distribution (hereinafter referred to as "standard deviation") is greater, as the difference between bright and dark areas becomes clearer, the shielding will decrease, thereby reducing the light characteristics.

According to various embodiments, the beam width and standard deviation are measured when the second top angle θ2 of the pyramid pattern of the second pattern layer 113 is approximately 130° and the first top angle θ1 of the prism pattern of the first pattern layer 111 changes from approximately 70° to approximately 120°.

Referring to FIG. 6a and FIG. 6b together, when the first vertex angle θ1 of the prism pattern is 70°, the beam width is 2.77 mm, when it is 80°, the beam width is 3.85 mm, when it is 90°, the beam width is 3.92 mm, when it is 100°, the beam width is 2.83 mm, when it is 110°, the beam width is 2.41 mm, and when it is 120°, the beam width is 2.71 mm. It can be confirmed that the beam width presents the maximum value in 90°. At the same time, when the vertex angle is greater than 90°, it can be confirmed that the shielding performance will decrease.

On the other hand, when the first vertex angle θ1 of the prism pattern is 70°, the standard deviation is 4256.8, when it is 80°, the standard deviation is 3593.2, when it is 90°, the standard deviation is 2660.8, when it is 100°, the standard deviation is 3293.0, when it is 110°, the standard deviation is 4385.2, and when it is 120°, the standard deviation is 5220.0, and it can be confirmed that the standard deviation value presents the minimum value in 90°. At the same time, when the vertex angle is greater than 90°, it can be confirmed that the standard deviation value will increase, thereby reducing the shielding performance.

Referring to FIG. 6a and FIG. 6b, when the top angle of the pyramidal pattern is 130°, it can be confirmed that the top angle of the prism pattern is 90°, which has the best optical performance in terms of shielding performance and standard deviation. According to various embodiments of the present invention, the top angle of the prism pattern can be set based on the intersection of the line graph about the beam width and the line graph about the standard deviation. For this purpose, referring to FIG. 6b, preferably, the prism pattern of various embodiments of the present invention can be formed to have a top angle in the range of 80° to 100°, and the range includes the prism top angle of 90° with the best optical performance.

Fig. 7a is a graph showing the illumination, beam width, standard deviation and brightness value of each pitch of the prism of various embodiments of the present invention. Fig. 7b is a graph showing the standard deviation of each pitch of the prism of various embodiments of the present invention.

7a and 7b, while the second vertex angle θ2 of the pyramidal pattern of the second pattern layer 113 and the first vertex angle θ1 of the prism pattern of the first pattern layer 111 are fixed, the illumination, beam width, standard deviation and brightness value can be confirmed by changing the spacing of the prism pattern of the first pattern layer 111.

According to multiple embodiments, when the second top angle θ2 of the pyramid pattern of the second pattern layer 113 is approximately 130° and the first top angle θ1 of the prism pattern of the first pattern layer 111 is approximately 90°, the beam width and standard deviation are measured when the pitch of the prism pattern changes from 10 μm to 90 μm.

Referring to FIG. 7c and FIG. 7b together, when the pitch of the prism pattern is 10 μm, the beam width is 4.19 mm, when the pitch is 30 μm, the beam width is 4.14 mm, when the pitch is 50 μm, the beam width is 3.92 mm, when the pitch is 70 μm, the beam width is 4.18 mm, and when the pitch is 90 μm, the beam width is 3.96 mm. It can be confirmed that the beam width presents the minimum value in 50 μm. At the same time, when the pitch is greater than 30 μm, it can be confirmed that the shielding performance will decrease.

On the other hand, when the pitch of the prism pattern is 10μm, the standard deviation is 2476.2, when the pitch is 30μm, the standard deviation is 2570.5, when the pitch is 50μm, the standard deviation is 2660.8, when the pitch is 70μm, the standard deviation is 2653.5, and when the pitch is 90μm, the standard deviation is 2677.0. It can be confirmed that the larger the pitch, the gradually increasing standard deviation value, and the maximum value is shown at a pitch of 50μm.

Referring to FIG. 7a and FIG. 7b, when the top angle of the pyramid pattern is 130° and the top angle of the prism pattern is 90°, it can be confirmed that the smaller the pitch of the prism pattern, the better optical performance in terms of shielding performance and standard deviation. According to various embodiments of the present invention, the pitch of the prism pattern can be set based on the intersection of the line graph of the beam width and the line graph of the standard deviation. For this purpose, referring to FIG. 7b, preferably, the prism pattern of various embodiments of the present invention can be formed to have a pitch of 10 μm to 30 μm.

Fig. 8a is a graph showing the illumination, beam width, standard deviation and brightness value at each vertex angle of the pyramid of multiple embodiments of the present invention. Fig. 8b is a graph showing the standard deviation at each vertex angle of the pyramid of multiple embodiments of the present invention.

8a and 8b, when the first vertex angle θ1 of the first pattern layer 111 is fixed and the second vertex angle θ2 of the pyramid pattern of the second pattern layer 113 is changed, the illumination, beam width, standard deviation and brightness value can be confirmed.

According to various embodiments, the beam width and standard deviation are measured when the first top angle θ1 of the prism pattern of the first pattern layer 111 is 90° and the second top angle θ2 of the pyramid pattern of the second pattern layer 113 is changed to approximately 90° to 150°.

Referring to FIG. 8a and FIG. 8b, when the second top angle θ2 of the pyramidal pattern is 90°, the beam width is 3.00 mm, when it is 100°, the beam width is 3.17 mm, when it is 110°, the beam width is 3.48 mm, when it is 120°, the beam width is 4.25 mm, when it is 130°, the beam width is 4.33 mm, when it is 140°, the beam width is 4.50 mm, and when it is 150°, the beam width is 3.75 mm. It can be confirmed that the beam width presents the maximum value in 140°. At the same time, when the top angle is greater than 140°, it can be confirmed that the shielding performance is reduced.

On the other hand, when the second top angle θ2 of the pyramidal pattern is 90°, the standard deviation is 5870.9, when it is 100°, the standard deviation is 5183.7, when it is 110°, the standard deviation is 4382.3, when it is 120°, the standard deviation is 3191.0, when it is 130°, the standard deviation is 2420.2, when it is 140°, the standard deviation is 2199.5, and when it is 150°, the standard deviation is 2177.5. It can be confirmed that the standard deviation value presents the minimum value in 150°.

Referring to FIG8a and FIG8b, when the top angle of the prism pattern is 90°, it can be confirmed that the best optical performance in terms of shielding performance and standard deviation is achieved when the top angle of the pyramidal pattern is 140°. According to various embodiments of the present invention, the top angle of the pyramidal pattern can be set based on the intersection of the line graph of the beam width and the line graph of the standard deviation. However, referring to FIG8a and FIG8b again, when the top angle of the pyramidal pattern is greater than 140°, the beam width decreases sharply, and therefore, 120° to 140° can be set as the preferred top angle range of the pyramidal pattern.

Fig. 9a is a graph showing the illumination, beam width, standard deviation and brightness value for each pitch of the pyramid of various embodiments of the present invention. Fig. 9b is a graph showing the standard deviation for each pitch of the pyramid of various embodiments of the present invention.

9a and 9b, while the second vertex angle θ2 of the pyramidal pattern of the second pattern layer 113 and the first vertex angle θ1 of the prism pattern of the first pattern layer 111 are fixed, the illumination, beam width, standard deviation and brightness value can be confirmed by changing the spacing of the pyramidal patterns of the second pattern layer 113.

According to multiple embodiments, when the second top angle θ2 of the pyramid pattern of the second pattern layer 113 is approximately 130° and the first top angle θ1 of the prism pattern of the first pattern layer 111 is approximately 90°, the beam width and standard deviation are measured when the pitch of the pyramid pattern changes from 40 μm to 100 μm.

Referring to Figures 9a and 9b together, when the pitch of the pyramidal pattern is 40μm, the beam width is 3.77mm, when the pitch is 60μm, the beam width is 3.60mm, when the pitch is 80μm, the beam width is 3.49mm, and when the pitch is 100μm, the beam width is 3.23mm. It can be confirmed that the larger the pitch of the pyramidal pattern, the lower the shielding performance.

On the other hand, when the pitch of the prism pattern is 40μm, the standard deviation is 2870.8, when the pitch is 60μm, the standard deviation is 2875.1, when the pitch is 80μm, the standard deviation is 2973.1, and when the pitch is 100μm, the standard deviation is 3362.2. It can be confirmed that the larger the pitch, the greater the standard deviation value, and the maximum value is shown at a pitch of 100μm.

Referring to FIG. 9a and FIG. 9b, when the top angle of the pyramidal pattern is 130° and the top angle of the prism pattern is 90°, it can be confirmed that the smaller the pitch of the pyramidal pattern is, the better optical performance in terms of shielding performance and standard deviation is obtained. According to various embodiments of the present invention, the pitch of the pyramidal pattern can be set based on the intersection of the line graph of the beam width and the line graph of the standard deviation. For this purpose, referring to FIG. 9b, preferably, the pyramidal pattern of various embodiments of the present invention is formed to have a pitch of 40 μm to 80 μm.

The optical films and backlight units including the optical films of the various embodiments of the present invention described above are not limited to the embodiments and drawings, and those skilled in the art should understand that various replacements, modifications and changes can be made within the technical scope of the present invention.

10: Backlight unit 11: Substrate 11a: Light source 12: Reflector 13: Color changer 15: Prism 15a: Vertex line 16: Prism 16a: Vertex line 17: Diffuser 20: Liquid crystal panel 100: First optical film 110: First film 120: Second film 200: Second optical film 210: Third film 220: Fourth film

FIG. 1 is a diagram showing a liquid crystal display device including a diffusion sheet of an embodiment. FIG. 2 is a diagram showing a liquid crystal display device including a backlight unit having a shielding sheet with multiple films laminated thereto of multiple embodiments of the present invention. FIG. 3 is a side view showing a shielding sheet with multiple films laminated thereto of multiple embodiments of the present invention. FIG. 4 is a three-dimensional view showing a shielding sheet with multiple films laminated thereto of multiple embodiments of the present invention. FIG. 5 is a diagram showing a sheet included in an optical film of multiple embodiments of the present invention. FIG. 6a is a diagram showing the illuminance, beam width, standard deviation and brightness value at each vertex angle of a prism of multiple embodiments of the present invention. FIG. 6b is a graph showing the standard deviation at each vertex angle of a prism of multiple embodiments of the present invention. FIG. 7a is a graph showing the illuminance, beam width, standard deviation, and brightness value of each pitch of the prism of multiple embodiments of the present invention. FIG. 7b is a graph showing the standard deviation of each pitch of the prism of multiple embodiments of the present invention. FIG. 8a is a graph showing the illuminance, beam width, standard deviation, and brightness value of each vertex of the pyramid of multiple embodiments of the present invention. FIG. 8b is a graph showing the standard deviation of each vertex of the pyramid of multiple embodiments of the present invention. FIG. 9a is a graph showing the illuminance, beam width, standard deviation, and brightness value of each pitch of the pyramid of multiple embodiments of the present invention. FIG. 9b is a graph showing the standard deviation of each pitch of the pyramid of multiple embodiments of the present invention.

10: Backlight unit

11: Substrate

11a: Light source

12: Reflective sheet

13: Color changing film

15: Prism

15a: Vertex line

16: Prism

16a: Vertex line

17: Diffusion film

20: LCD panel

100: The first optical film

110: The first piece

120: The second piece

200: Second optical film

210: The third piece

220: The fourth piece

Claims (14)

A backlight unit includes: a light source; a color change sheet for changing the color of light emitted from the light source; and at least one optical film disposed on the color change sheet; wherein the at least one optical film includes: a first sheet including a first substrate portion, a first pattern layer and a second pattern layer, the first pattern layer being disposed on one side of the first substrate portion and including a first pattern, the second pattern layer being disposed on the other side of the first substrate portion and including a second pattern different from the first pattern; and a second sheet including a first substrate portion; The optical film is provided with a first substrate portion, a second substrate portion, a third pattern layer and a fourth pattern layer, wherein the third pattern layer is disposed on one side of the second substrate portion and includes the first pattern, and the fourth pattern layer is disposed on the other side of the second substrate portion and includes the second pattern; the first sheet and the second sheet of the optical film are bonded together; wherein the optical film comprises: a first optical film, which comprises a first sheet and a second sheet, wherein the first sheet comprises a first substrate portion, a first pattern layer and a second pattern layer, wherein the first pattern layer is disposed on one side of the first substrate portion and includes the first pattern, and the fourth pattern layer is disposed on the other side of the second substrate portion and includes the second pattern. The second pattern layer is arranged on the other side of the first substrate portion and includes a second pattern different from the first pattern, the second sheet includes a second substrate portion, a third pattern layer and a fourth pattern layer, the third pattern layer is arranged on one side of the second substrate portion and includes the first pattern, the fourth pattern layer is arranged on the other side of the second substrate portion and includes the second pattern; and a second optical film includes a third sheet and a fourth sheet, the third sheet includes a third substrate portion, a fifth pattern layer and a sixth pattern layer, the fifth pattern layer is arranged on the third substrate portion The first sheet and the second sheet of the first optical film are bonded together; and the third sheet and the fourth sheet of the second optical film are bonded together. A backlight unit as described in claim 1, wherein the first pattern includes a prism pattern arranged parallel to a first direction. A backlight unit as described in claim 2, wherein the second pattern includes a pyramidal pattern having a plurality of rows in a second direction and a plurality of columns in a third direction perpendicular to the second direction. The backlight unit as described in claim 3, wherein the second pattern is an engraved pyramidal pattern formed by etching the other surfaces of the first substrate portion and the second substrate portion. A backlight unit as described in claim 3, wherein the second direction and the first direction have an angle of -5° to +5°. A backlight unit as described in claim 3, wherein the prism pattern forms a first vertex angle defined as the angle between two facing surfaces of three surfaces of a triangular cross-sectional shape; the first vertex angle is 80° to 100°. The backlight unit as described in claim 1, wherein the thickness of the first pattern is 5μm to 35μm, and the pitch of the first pattern is 10μm to 70μm. The backlight unit as described in claim 1, wherein the second pattern is a pyramidal pattern, which forms a second top angle defined as the angle between two facing faces among the four faces of the pyramidal shape, and the second top angle is 120° to 140°. The backlight unit as described in claim 1, wherein the thickness of the second pattern is 5μm to 15μm, and the pitch of the second pattern is 20μm to 60μm. The backlight unit as described in claim 1, wherein the refractive index of the first pattern layer is less than the refractive index of the second pattern layer, and the refractive index of the third pattern layer is greater than the refractive index of the fourth pattern layer. The backlight unit as described in claim 1, wherein the thickness of the third substrate parts and the fourth substrate parts is different from the thickness of the first substrate parts and the second substrate parts. The backlight unit as described in claim 1, wherein the thickness of the third substrate parts and the fourth substrate parts is greater than the thickness of the first substrate parts and the second substrate parts. The backlight unit as described in claim 1 also includes a prism sheet disposed on the optical film, wherein the prism sheet is stacked with a first prism sheet and a second prism sheet having prism patterns arranged in different directions. The backlight unit as described in claim 1, wherein the refractive index of the first pattern layer is less than the refractive index of the second pattern layer, the refractive index of the third pattern layer is greater than the refractive index of the fourth pattern layer, the refractive index of the fifth pattern layer is greater than the refractive index of the sixth pattern layer, and the refractive index of the seventh pattern layer is greater than the refractive index of the eighth pattern layer.