Patent ID: 12222534

DETAILED DESCRIPTION

Various embodiments and terms used in the specification are not intended to limit the technical features described in the specification to specific embodiments, but it should be understood to include various modifications, equivalents, or substitutions of the embodiments. In connection with the description of the drawings, similar reference numerals may be used for similar or related components. The singular form of the noun corresponding to the item may include one or more of the elements unless the relevant context clearly dictates otherwise.

According to various embodiments, each component (e.g., module or program) of the above-described components may include a single or plural entity, and some of the plurality of entities may be separately placed in other components. According to various embodiments, one or more of the components or operations described above may be omitted, or one or more other components or operations may be added. Multiple components (e.g., modules or programs) may be alternatively or additionally integrated into a single component. In this case, the integrated component may perform one or more functions of each component of the plurality of components in the same or similar manner as those performed by the corresponding component of the plurality of components prior to the integration. According to various embodiments, operations performed by a module, program, or other component may be executed sequentially, in parallel, iteratively, or heuristically, or one or more of the operations may be executed in a different order or omitted. Alternatively, one or more other operations may be added.

Various embodiments will be described with reference to the associating drawings. In describing the prevent embodiments, the same names and the same symbols are used for the same components, and additional description will be omitted. In addition, in describing embodiments of the present disclosure, it is clear in advance that the same names and same symbols are used for components having the same function, but that they are not substantially the same as the conventional ones.

According to various embodiments, terms such as “comprise” or “have” are intended to designate the presence of a feature, number, step, operation, component, part, or combination described in the specification. It should be understood, however, that the above does not preclude the possibility of addition or existence of one or more of other features, or numbers, steps, operations, components, parts, or combinations.

FIG.1is a perspective view showing a liquid crystal display (LCD) device including an optical film according to an embodiment. In the detailed description below, a longitudinal direction (a vertical direction) of a liquid crystal display (LCD) device1may be referred to as a ‘Y-axis direction’, a lateral direction (a horizontal direction) may be referred to as an ‘X-axis direction’, and/or a height direction (a thickness direction) may be referred to as a ‘Z-axis direction.’ Additionally, in some embodiments, the direction where a component is oriented may be referred to as ‘negative/positive (−/+)’ along with the orthogonal coordinate system illustrated in the drawing. As shown inFIG.1, if the term ‘negative/positive (−/+)’ is not written in the orthogonal coordinate system, the coordinate axis may be interpreted as pointing in the + direction unless otherwise defined. For example, ‘X-axis direction’ can be interpreted as pointing to the +X-axis direction, and ‘Y-axis direction’ can be interpreted as pointing to the +Y-axis direction. ‘Z-axis direction’ can be interpreted as pointing to the +Z-axis direction. For example, referring toFIG.1, if a second sheet120is disposed over a first sheet110, it can be defined as being the second sheet120placed from the first sheet110on the ‘+Z axis direction.’ For example, referring toFIG.4A, it can be defined that one surface (e.g., a first side112a) of a first base portion112is a surface facing the ‘+Z-axis direction and the other surface (e.g., a second surface112b) is a surface facing the ‘−Z axis direction.’ According to an embodiment, in the description of an optical film100, the direction where light from the light source travels may be expressed as, for example, ‘+Z-axis direction.’ In explaining the direction below, heading toward one of the three axes of the orthogonal coordinate system may include heading in a direction parallel to the axis. Note that this is based on the orthogonal coordinate system described in the drawings for brevity of explanation, and that the description of directions or components does not limit the various embodiments of the present disclosure.

Referring toFIG.1, the liquid crystal display (LCD) device1may include a backlight unit10and a liquid crystal panel20. According to various embodiments, the backlight unit10may face the rear surface (a surface facing the −Z-axis direction) of the liquid crystal panel20to emit light to the liquid crystal panel20. The backlight unit10may include a light source11, a light guide plate12, a reflector13, an optical film100, and a diffusion sheet17. The backlight unit10may further include a reflective polarizing sheet although not shown in the drawing.

The light source11may be configured to emit light on the back of the liquid crystal panel20and may be placed on one side of the light guide plate (LGP)12. The light source can be classified as an edge-type or a direct-type depending on the structure configuration and in the present disclosure, as shown inFIG.1, an edge-type light source can be utilized. The light source11may be configured to emit light to the back of the liquid crystal panel20and the light emitted from the light source11can be converted into a surface light source by the light guide plate12. At this time, the light source11may be a cold cathode fluorescent lamp (CCFL) or an external electrode fluorescent lamp (EEFL). The reflector13may be disposed behind the light guide plate12thereby reflecting the light emitted toward the rear of the light guide plate12(a surface facing the −Z-axis direction) to the light guide plate12and then, making it incident. As a result, the loss of light can be minimized. In other words, the reflector13can perform light recycling.

Referring toFIG.1, the light emitted from the light guide plate12is incident to the optical film100. The optical film100of the present disclosure may include at least one prism sheet for concentrating light and it may further include a sheet including a pyramid pattern as a sheet for uniformly dispersing the incident light from the light guide plate12and then making it incident to the prism sheet. For convenience of explanation, one prism sheet or a combination of two or more prism sheets for concentrating light included in the optical film100can be referred to as a ‘concentrating prism sheet’ (or ‘cross prism sheet’) and a sheet containing the pyramid pattern can be referred to as a ‘pyramid sheet’ in the following description.

As will be described in detail below, the optical film100of the present disclosure may include a first sheet110where a pyramid pattern is formed on one surface facing a direction parallel to the direction of travel of the light emitted from the light source (e.g., Z-axis direction) and a prism pattern (i.e., a reversed prism pattern) is formed on the other surface facing a direction opposite to the direction of travel of the light emitted from the light source as a pyramid sheet. In addition, the optical film100of the present disclosure may include a second sheet120where a prism pattern is formed on one surface facing a direction parallel to the direction of travel of the light emitted from the light source (e.g., Z-axis direction) as a concentrating prism sheet. According to one embodiment, a diffusion layer may be formed on the other surface of the second sheet120facing a direction opposite to the direction of travel of the light emitted from the light source. According to one embodiment, the optical film100of the present disclosure may further include a third sheet130having a prism pattern where a direction of an edge of the prism pattern is different to a direction of an edge of the prism pattern formed on the second sheet120as a concentrating prism sheet other than the second sheet120. According to one embodiment, a diffusion layer may be formed on the other surface of the third sheet130facing a direction opposite to the direction of travel of the light emitted from the light source.

The concentrating prism sheet (the second sheet120and/or the third sheet130) can collect incident light using an optical pattern formed on its surface and then emit it to the liquid crystal panel20. The concentrating prism sheet (the second sheet120and/or the third sheet130) may include a transparent base film and a prism pattern layer formed on an upper surface (a surface facing the +Z-axis direction) of the base film. The prism pattern layer may be formed as an optical pattern layer in the form of a triangular array with a lateral face at a specified inclination angle (for example, a lateral face with 45° inclination) to improve brightness in the plane direction. The prism patterns of the prism pattern layer may be in the shape of a triangular pillar and may be arranged so that one surface of the triangular pillar faces the base film. The cross-section of each of the prism patterns may be triangular.

According to one embodiment, the concentrating prism sheet (the second sheet120and/or the third sheet130) may include the second sheet120and the third sheet130to form a composite prism sheet structure. Here, the third sheet130may be arranged to overlap the second sheet120. In the second sheet120, a plurality of second prism patterns may be arranged side by side with each other. Each second prism pattern may have a structure extending in one direction. For example, the vertex lines (referred to as ‘edges’) of each of the second prism patterns may be formed to extend toward the X-axis direction. Similarly, in the third sheet130, a plurality of third prism patterns may also be arranged side by side with each other. Each of the third prism patterns may have a structure extending in one direction. For example, the edges of each of the third prism patterns may be formed to extend toward the Y-axis direction which is perpendicular to the X-axis direction. Here, the extension direction of the first prism patterns and the extension direction of the second prism patterns are shown as facing the X-axis direction and Y-axis direction for convenience of explanation. However, it should be noted that it is not limited to the illustrated embodiment and may be oriented in a direction other than the X-axis direction or Y-axis direction.

According to one embodiment, a prism pattern (a plurality of first prism patterns) may also be formed on the pyramid sheet (the first sheet110). The plurality of first prism patterns included in the first sheet110may be formed to be protruded to a reversed direction (−Z-axis direction) of the direction of travel of light (+Z-axis direction) unlike the plurality of second prism patterns included in the second sheet120and the plurality of third prism patterns included in the third sheet130where they are protruded to a direction parallel to the direction of travel of light. Accordingly, the plurality of first prism patterns included in the first sheet110may be referred to as ‘reversed prism patterns.’ The edge direction P1of the plurality of first prism patterns (referred to as a ‘first prism direction’) may be formed the same as or different from the edge direction P2of the plurality of second prism patterns (referred to as a ‘second prism direction’) and the edge direction P3of the plurality of third prism patterns (referred to as a ‘third prism direction’). According to one embodiment, as shown inFIG.1, the edge direction P1of the plurality of first prism patterns may be perpendicular to the edge direction P2of the plurality of second prism patterns and may be parallel to the edge direction P3of the plurality of third prisms. The liquid crystal display (LCD) device1of the present disclosure may have associating effects. A more detailed explanation regarding the edge direction of the prism patterns will be described later.

The diffusion sheet17can uniformly disperse light incident from the optical film100. The diffusion sheet17where curable resin solution (e.g., urethane acrylate, epoxy acrylate, ester acrylate, or at least one selected from or mixed of ester acrylate and radical generating monomer) added with light diffusion beads is deposited can induce light diffusion by the light diffusion beads. In addition, the diffusion sheet17may be formed a protrusion pattern (or a protrusion portion) having uniform or non-uniform size of shape (e.g., spherical, hemispherical, or elliptical) to promote the diffusion of light. According to some conventional embodiments, the diffusion sheet17may further include the upper diffusion sheet17disposed over the concentrating prism sheet disclosed inFIG.1as well as the lower diffusion sheet disposed below the concentrating prism sheet. However, in the present specification, the lower diffusion sheet can be replaced by providing an optical film100where the concentrating prism sheet and the pyramid sheet are combined.

According to the embodiment, at least one of the above-described components (e.g., the diffusion sheet17) may be omitted from or one or more other components (e.g., a reflective polarizing sheet (not shown)) may be added to the backlight unit10.

Because the reflective polarizing sheet (not shown) may be provided on the top of the optical film100and the diffusion sheet17, it may play a role to transmit some polarized light of light concentrated from the optical film100and diffused by the upper diffusion sheet17and to reflect other polarized light to the lower part.

The liquid crystal panel20can refract light emitted from the light source11into a predetermined pattern according to an electrical signal. The refracted light may pass through a color filter and a polarizing filter disposed on the front of the liquid crystal panel20to construct an image.

Components included in the liquid crystal display (LCD) device1ofFIG.1may be assembled with other components in an overlapped and stacked fashion in a height direction (+Z-axis direction). For example, in the liquid crystal display (LCD) device1according to a certain embodiment as shown inFIG.1, the individually manufactured backlight unit10and the liquid crystal panel20may be overlapped and stacked in the height direction (+Z-axis direction).

FIG.2is a drawing illustrating a liquid crystal display (LCD) device including an optical film according to an embodiment.FIG.3is a drawing illustrating a liquid crystal display (LCD) device including an optical film according to an embodiment.

FIG.2may represent a cross-section parallel to a plane formed by the Y and Z axes of the liquid crystal display (LCD) device1andFIG.3may represent a cross section parallel to a plane formed by the X and Z axes of the liquid crystal display (LCD) device1. Below, overlapping description withFIG.1will be omitted.

The liquid crystal display (LCD) device1of the present disclosure may be characterized as replacing the diffusion sheet only with the optical film100of the present disclosure without a separate diffusion sheet (e.g., the lower diffusion sheet) between the optical film100and the light guide plate12.

In the present disclosure, the ‘optical film100’ may refer to a film including a first sheet110with a plurality of pyramid patterns formed on one surface, a second sheet120disposed on the first sheet110with a plurality of prism patterns formed on one surface, and a third sheet130disposed on the second sheet120with a plurality of prism patterns formed on one surface as shown inFIGS.1to3. InFIGS.1to3, for convenience of explanation, the first sheet110, the second sheet120, and the third sheet130are shown as spaced apart from each other. However, unlike this, the first sheet110, the second sheet120, and the third sheet130may be formed by being laminated with each other (via lamination). In the present specification, ‘lamination’ may mean that two different sheets are adhered by an included pattern formed of adhesive resin on at least one surface of the facing surfaces of the two different sheets. For example, there is a pattern formed of semi-cured adhesive resin on one of the two opposing surfaces of two different sheets and the other surface may be in contact with this pattern, and then completely cured and adhered. In addition, for example, two opposing surfaces of two different sheets may be formed of adhesive resin in a semi-cured state and may be fully cured and adhered after contacting each other. The laminated optical film100can be provided to a backlight unit that is thinner and has excellent shielding performance compared to an embodiment where the film is simply stacked rather than laminated.

The plurality of pyramid (or quadrangular pyramid) patterns of the first sheet110may refract and/or reflect light transmitted from the light source11and then transmit it to the second sheet120. The second sheet120may be formed with a plurality of prisms (or triangular pillars) extending in the lateral direction (X-axis direction) of the liquid crystal display (LCD) device1and protruding in the height direction (Z-axis direction). The second sheet120may transmit light passing through the first sheet110to the third sheet130. The third sheet130may be formed with a plurality of prisms (or triangular pillars) extending in the longitudinal direction (Y-axis direction) of the liquid crystal display (LCD) device1and protruding in the height direction (Z-axis direction). The third sheet130can transmit light passing through the second sheet120toward the liquid crystal panel20. Because the light incident to the optical film100from the light source11may be diffused and/or concentrated while sequentially passing through the first sheet110, the second sheet120, and the third sheet130to form the light source11, it is possible to have the advantage of not only securing shielding performance for covering the shape of the light source11, but also securing high brightness performance. According to an embodiment inFIGS.1to3, the plurality of prism patterns of the second sheet120is shown to be extended in the lateral direction (X-axis direction) of the liquid crystal display (LCD) device1and the plurality of prism patterns of the third sheet130is shown to be extended in the longitudinal direction (Y-axis direction) of the liquid crystal display (LCD) device1but are not necessarily limited to. In contrast, the plurality of prism patterns of the second sheet120may be extended in the longitudinal direction (Y-axis direction) of the liquid crystal display (LCD) device1and the plurality of prism patterns of the third sheet130may be extend in the lateral direction (X-axis direction) of the liquid crystal display (LCD) device1. However, it may be sufficient for the plurality of prism patterns of the second sheet120and the plurality of prism patterns of the third sheet130to be orthogonal to each other.

Referring toFIG.1again, the pyramid pattern layer111of the first sheet110may include a pyramid pattern (referred to as the pyramid pattern111aofFIG.4A) having a length of a first side of a pyramid base of ‘a’ in a first pyramid direction, a length of a second side of the pyramid base of ‘b’ in a second pyramid direction, a height of ‘h’, and four side surfaces111-1,111-2,111-3,111-4having vertex angles of A and B. The dimensions of the pyramid pattern may be set differently depending on the embodiment. When the pyramid base of the pyramid pattern111ais viewed from above (e.g., looking in a direction opposite to the Z-axis direction), the pyramid base may have a rectangular shape having the length of the first side of the pyramid base of a in the first pyramid direction and the length of the second side of the pyramid base of b in the second pyramid direction. In this case, a diagonal length of the pyramid base is c. According to an embodiment, the pyramid base of the pyramid pattern111amay be square. In this case, the length of a in the pyramid first direction and the length of b in the pyramid second direction are the same (a=b), and the diagonal length of the pyramid base c may have the value of √2a. However, in the present specification, the fact that the pyramid base of the pyramid pattern111ais square may include the case where the length of a in the first pyramid direction is the same as the length of b in the second pyramid direction (a=b) but is not limited to. It should be noted that cases where the length of a in the first pyramid direction and the length of b in the second pyramid direction are different within a certain margin of error (e.g., 15% margin of error) (a≠b) may also be included.

Below, the optical film100will be described in more detail with reference toFIGS.4A to4F.FIG.4Ais a cross-sectional view showing an optical film according to an embodiment.FIG.4Bis a cross-sectional view showing an optical film according to an embodiment.FIG.4Cis a cross-sectional view showing an optical film according to an embodiment.FIG.4Dis an image and a cross-sectional view showing a pyramid pattern and a prism pattern according to an embodiment.FIG.4Eis an image illustrating a top view of the pyramid pattern layer before lamination according to an embodiment.FIG.4Fis an image illustrating a top view of the pyramid pattern layer after lamination according to an embodiment.

Referring toFIGS.4A to4C, the optical film100according to an embodiment of the present disclosure may include an optical film100aincluding a first sheet110, an optical film100bincluding the first sheet110, and a second sheet120, and an optical film100cincluding the first sheet110, the second sheet120and a third sheet130. For example, the first sheet110may be used alone as a component of the optical film100awithout using other sheets (e.g., the second sheet120and the third sheet130). According to the present disclosure, the second sheet120and/or the third sheet130may further include the first sheet110thereby providing an optical film with excellent shielding performance against a light source and excellent brightness performance. Below, unless otherwise specified, each component included in the optical film100may be described in detail using the optical film100cofFIG.4Cas an example for convenience. According to an embodiment, the optical film of three sheets110,120,130(e.g., the optical film100cofFIG.4C) as well as the optical film of one sheet110(e.g., the optical film100aofFIG.4A) and the optical film of two sheets110,120(e.g., the optical film100bofFIG.4B) may also be included within the scope of the present disclosure.

Referring toFIG.4C, the optical film100(e.g., optical film100c) may include the first sheet110, the second sheet120, and the third sheet130, respectively, and they may also respectively include a first base portion112, a second base portion122, and a third base portion132. At this time, the first base portion112, the second base portion122, and the third base portion132may be made of transparent material capable of transmitting light including, for example, polycarbonate series, polysulfone series, polyacrylate series, polystyrene series, polyvinyl chloride series, polyvinyl alcohol series, polynorbornene series, and polyester series material. For a specific example, the first base portion112, the second base portion122, and/or the third base portion132may be made of polyethylene terephthalate (PET) or polyethylene naphthalate, etc. The first base portion112, the second base portion122, and the third base portion132may be, for example, PET with a thickness of about 10 μm to about 50 μm, and more specifically, they may be PET having a thickness of about 24 μm to about 40 μm. In various experimental examples, including the viewing angle distribution described later with reference toFIG.6Aand subsequent drawings, the first base portion112, the second base portion122, and the third base portion132each made of PET with a thickness of 24 μm can be used as examples. However, it should be noted that the thicknesses of the first base portion112, the second base portion122, and the third base portion132are not limited to the above examples.

As previously discussed in the embodiment ofFIG.1, the first sheet110may include a pyramid pattern111awith a first pyramid directional length of ‘a’, a second pyramid directional length of ‘b’, a height of ‘h’, a pitch of ‘P’, and four side surfaces111-1,111-2,111-3,111-4forming the vertex angles of A and B corresponding to a quadrangular pyramid shape formed on the first surface112aof the first base portion112. The optical film100may include a plurality of pyramid patterns111ahaving a plurality of columns in the first pyramid direction and a plurality of rows in the second pyramid direction perpendicular to the first pyramid direction.

Referring toFIGS.4A and4Dtogether, according to an embodiment, the pyramid pattern111amay be an intaglio pattern. The pyramid pattern111amay mean an intaglio pattern where quadrangular pyramid shaped grooves are formed regularly and it may be defined by the four side surfaces111-1,111-2,111-3,111-4. Here, the four sides may have the same or different triangular shapes, and the dimensions of the vertex angles of A and B may be set according to the lateral length of ‘a’, the longitudinal length of ‘b’, and the height of each cross-section of the pyramid pattern111a. According to an embodiment, the vertex angles A and B may be formed as substantially the same angle, and accordingly, the lateral length of ‘a’ and the longitudinal length of ‘b’ of the pyramid pattern111amay also be set to be substantially the same. Here, the fact that the vertex angles A and B are substantially the same may mean that the vertex angle A and the vertex angle B have the same value within a process deviation (e.g., about 10%).

Additionally, the height of ‘h’ and the pitch of ‘P’ may be set with respect to the vertex angle of C of the pyramid pattern111a. The optical film100may include the pyramid pattern111awhose vertical cross-section parallel to the height direction (Z-axis direction) is triangular or trapezoid and the vertex angle of C may be defined as an angle formed between two facing sides of the four sides of the pyramid pattern111a.

According to an embodiment, the vertex angle of C of the pyramid pattern111amay be defined as 60° or more and 160° or less. For example, the vertex angle of C may be 90°. As the vertex angle of C of the pyramid pattern111ais increased within a specified angle range, the angle θ (theta) of light incident to the second sheet120(referred to as ‘incident angle θ’) may be increased. For example, in case of the optical film (e.g., the optical film100c) including three sheets of the present disclosure, the first sheet110including the pyramid pattern111amay play a role in ensuring that light incident to the second sheet120and the third sheet130can be incident at an optimal angle in a way to improve brightness. The relationship between the components of the optical film and the brightness will be described in more detail later with reference to embodiments inFIG.5and subsequent drawings.

According to an embodiment, the pyramid pattern111amay also be formed as an embossed pattern.FIG.4Eshows the pyramid pattern layer before the first sheet110is laminated to the second sheet120andFIG.4Fshows the pyramid pattern where the first sheet110is peeled from the second sheet120after the first sheet110and the second sheet120was laminated. Referring toFIG.4E, the pyramid pattern layer111before lamination may include a first barrier rib111-5formed between the first side surface111-1and the fourth side surface111-4for defining a boundary between the first side surface111-1and the fourth side surface111-4and a second barrier rib111-6formed between the second side surface111-2and the third side surface111-3for defining a boundary between the second side surface111-2and the third side surface111-3. The barrier rib111-5and the second barrier rib111-6may be the uppermost part of the first sheet110. According to an embodiment, the first barrier rib111-5may be formed to be parallel to the first pyramid direction and the second barrier rib111-6may be formed to be parallel to the second pyramid direction, but noted that it is not necessarily limited. Referring toFIG.4F, if the pyramid pattern layer111disposed on the upper surface of the first sheet110is laminated to the rear surface of the second sheet120(e.g., the rear surface of the second base portion121of the second sheet120or the first diffusion layer123of the second sheet120), tips of the first barrier rib111-5and the second barrier rib111-6, which are the uppermost part of the pyramid pattern layer111, may be pressed. Accordingly, the tip of the first barrier rib111-5may be deformed to form a first flat portion111-7with a predetermined width W1and the tip of the second barrier rib111-6may be deformed to form a second flat portion111-8with predetermined width W2. According to an embodiment, the width W1of the first flat portion111-7and the width W2of the second flat portion111-8may be substantially the same.

According to various embodiments of the present disclosure, it is possible to control lights in four quadrant directions in a peripheral area by including the pyramid pattern layer111. According to an embodiment of the present disclosure, the pyramid pattern layer111may include a pyramid pattern111awhose vertex angle, which is the angle between two facing triangles, may be greater than or equal to 90° and less than or equal to 130°. According to an embodiment, if the vertex angle of the pyramid pattern111ais formed at an angle of at least 90°, the shielding performance can be satisfied as shown inFIG.6Aand if the vertex angle is less than 90°, hot spot visibility (HSV) where the light source11ais visible may be increased.

The pyramid pattern layer111may be composed of a plurality of pyramid patterns and may be regularly arranged on the first surface112aof the first sheet110. A first prism pattern layer113including a plurality of first prism patterns may be formed on the second surface112bof the first base portion112. Except for the direction where the first prism pattern layer113is arranged with the second prism pattern layer121provided on the second sheet120and the third prism pattern layer131provided on the third sheet130, it may have substantially the same configuration with others.

A plurality of second prism patterns extended along the lateral direction (or longitudinal direction) of the liquid crystal display (LCD) device1. It may include a second prism pattern layer121. The cross-section of the second prism pattern layer121may be triangular. For example, the plurality of second prism patterns included in the second prism pattern layer121may have a pitch of pi3 and a height of h3. The third sheet130may be formed on the first surface132aof the third base portion132with a plurality of third prism patterns extended in parallel in the longitudinal direction (or lateral direction) of the liquid crystal display (LCD) device1. It may include a third prism pattern layer131. The cross-section of the prism pattern formed in the third prism pattern layer131may be triangular. For example, the plurality of third prism patterns formed in the third prism pattern layer131may have a pitch of ‘pi4’ and a height of ‘h4’. Here, the plurality of second prism patterns included in the second prism pattern layer121and the plurality of third prism patterns included in the third prism pattern layer131may be extended in directions orthogonal to each other, and the second and the third prism patterns may be formed to have the same pitch and height each other, but is not necessarily limited to and the configuration of the prism patterns may be varied depending on the embodiment.

According to the embodiment, a first diffusion layer123may be included on the second surface122bof the second base portion122of the second sheet120and a second diffusion layer133may be included on the second surface132bof the third base portion132of the third sheet130. The first diffusion layer123and the second diffusion layer133may be treated to have a matte pattern to increase turbidity by creating a rough surface of the first diffusion layer123and the second diffusion layer133, respectively, by using beads of glass and polymer, etc. It can be manufactured using any treatment method that increases turbidity including bead treatment to increase turbidity. For example, in various experimental examples including the viewing angle distribution described later in the drawings ofFIG.8B, the first diffusion layer123has a haze value of 3% and the second diffusion layer133has a haze value of 40%.

The first sheet110and the second sheet120may be laminated through the pyramid pattern layer111of the first sheet110and the second sheet120(or the first diffusion layer123of the second sheet120). The second sheet120and the third sheet130may be laminated through the second prism pattern layer121of the second sheet120and the third sheet130(or the second diffusion layer133of the third sheet130). At this time, each of the first diffusion layer123and the second diffusion layer133may be formed of, for example, an adhesive (e.g., adhesive resin) matte pattern. It can be manufactured by initially laminating a sheet with approximately 50% cured state which was not 100% cured (e.g., a semi-cured state) to another sheet and then, laminating the sheet to another sheet with being 100% cured state.

FIG.5Ashows the configuration for measuring the brightness of an optical film according to an embodiment.FIG.5Bis a table showing a viewing angle distribution and an optimal incident angle for increasing light distribution and brightness according to an embodiment. InFIG.5B, the viewing angle distribution may represent the distribution of light focused on a horizontal plane (e.g., a plane parallel to the XY plane).

Referring toFIG.5A, the configuration of an experiment for measuring the brightness may include an optical film100and an optical measurement device210. Here, the optical film100may represent the second sheet120and the third sheet130laminated together and the first sheet110may be omitted. The optical measurement device210may be a high-speed spectroscopic measurement system such as a colorimetric luminance meter. Although not shown in the drawing, a backlight unit including a light source may be disposed on the opposite side of the optical measurement device210with respect to the optical film100.

The optical measurement device210can measure light incident in a height direction (Z-axis direction) of the optical film100as shown inFIG.5A. And the light distribution can be illustrated as shown inFIG.5Bby using a viewing angle distribution (BSDF, bidirectional scattering distribution function). At this time, to obtain high brightness for the liquid crystal display LCD) device1, the brightness near ‘0° reference of the optical measurement device’ which is parallel to the Z-axis direction where the optical measurement device210faces must be high in the viewing angle data measured by the optical measurement device210. It was found through experimental results that the brightness around 0° became the highest when light passing through the second sheet120and the third sheet130in the optical film100was incident at a specific angle. In other words, the brightness of the liquid crystal display (LCD) device1can be the highest when light passing through the lower surface of the laminated one of the second sheet120and the third sheet130(e.g., the second surface122bof the second sheet120) is incident at a specific angle of incidence θ. Here, the incident angle θ may mean an angle formed by central light of the light (or light bundle) emitted from the first sheet110with respect to a normal line to the second surface122bof the second sheet120.

For example, referring to an embodiment (example 1-1) ofFIG.5B, in an embodiment where the second base portion122and the third base portion132have a thickness of 24 μm, respectively, if the pitch ‘pi3’ of the prism pattern of the second prism pattern layer121formed on the first surface122aof the second base portion122is 50 μm and the height ‘h3’ is 25 μm; the first diffusion layer123formed on the second surface122bof the second base portion122has a haze value of 3%; the pitch ‘pi4’ of the prism pattern of the third prism pattern layer131formed on the first surface132aof the third base portion132is 50 μm and the height ‘h4’ is 25 μm; and the second diffusion layer133formed on the second surface132bof the third base portion132has a haze value of 40%, the optimal angle of incidence θ where the brightness near 0° reference of the optical measurement device becomes the highest may be formed at 65°. In other words, when light passing through the lower surface of the laminated one of the second sheet120and the third sheet130(e.g., the second surface122bof the second sheet120) is incident at +65° (or −65°), the highest brightness can be achieved.

In addition, for example, referring to an embodiment (example 1-2) ofFIG.5B, in an embodiment where the second base portion122and the third base portion132have a thickness of 24 μm, respectively, if the pitch ‘pi3’ of the prism pattern of the second prism pattern layer121formed on the first surface122aof the second base portion122is 45 μm and 55 μm and the height ‘h3’ is 22.5 μm and 22.7 μm; the first diffusion layer123formed on the second surface122bof the second base portion122has a haze value of 15%; the pitch ‘pi4’ of the prism pattern of the third prism pattern layer131formed on the first surface132aof the third base portion132is 50 μm and the height ‘h4’ is 25 μm; and the second diffusion layer133formed on the second surface132bof the third base portion132has a haze value of 30%, the optimal angle of incidence θ where the brightness near 0° reference of the optical measurement device becomes the highest may be formed at 73°. In other words, when light passing through the lower surface of the laminated one of the second sheet120and the third sheet130(e.g., the second surface122bof the second sheet120) is incident at +73° (or −73°), the highest brightness can be achieved.

To summarize the above, the incident angle θ of light incident to the second sheet120may be determined by the configuration and/or the edge direction (e.g., P2inFIG.1) of the plurality of second prism patterns of the second prism pattern layer121included in the second sheet120and the configuration and/or the edge direction (e.g., P3inFIG.1) of the plurality of third prism patterns of the third prism pattern layer131included in the third sheet130. In other words, the incidence angle θ can be set in various ways depending on the requirements of the second sheet120and/or the third sheet130required also for the optical film100. Because the optical film100in the present disclosure may include the first prism pattern layer113including the prism pattern on the lower surface and the pyramid pattern layer111including the pyramid pattern on the upper surface based on the first base portion112, it is possible to form an optical path corresponding to the optimal angle of incidence θ required for the optical film100according to a certain embodiment and as a result, the optical film100with high brightness can be provided. Meanwhile, referring toFIG.5B, the viewing angle Φ is displayed, and it may mean an angle formed by an imaginary line extending from the center of the viewing angle distribution shown inFIG.5Bto one side (e.g., a direction parallel to the X-axis) and the central light of the emitted light (or light bundle) from the first sheet110. The viewing angle (Φ, phi) is determined by the configuration and/or the edge direction (e.g., P1inFIG.1) of the plurality of first prism patterns of the first prism pattern layer113of the first sheet110where light is incident to the second sheet120. The optimal viewing angle Φ in the two embodiments (example 1-1, example 1-2) shown inFIG.5Bis formed at 45°.

According to various embodiments of the present disclosure, it is possible to provide the optical film100including the first sheet110designed to increase the shielding performance in the direction where light is incident as well as for light passing through the lower surface of the laminated one of the second sheet120and the third sheet130(e.g., the second surface122bof the second sheet120) to be incident at a specific angle θ. Referring toFIGS.1to5B, the optical film100according to one embodiment may comprise the first sheet110including the first base portion112, the pyramid pattern layer111where a plurality of pyramid patterns is formed on the first surface112aof the first base portion112, and a first prism pattern layer113where a plurality of first prism patterns is formed on the second surface112bof the first base portion112; the second sheet120disposed overlapping the first sheet110including the second base portion122, the second prism pattern layer121where a plurality of second prism patterns are formed on the first surface122aof the second base portion122, and the first diffusion layer123formed on the second surface122bof the second base portion122; and the third sheet130disposed overlapping the second sheet120including the third base portion132, the third prism pattern layer131where a plurality of third prism patterns formed on the first surface132aof the third base portion132, and the second diffusion layer133formed on the second surface132bof the third base portion132.

In the liquid crystal display (LCD) device1ofFIGS.1to5B, the first sheet110, the second sheet120, and the third sheet130may be manufactured in a form where the first sheet110, the second sheet120, and the third sheet130are laminated together. Particularly considering the configurations of the laminated second sheet120and the third sheet130, the first sheet110can refract and/or reflect light to enter at an angle θ from a point where the second surface122bof the second sheet120meets to the second sheet120by properly adjusting the configurations of the pyramid pattern layer111formed on the first surface112aof the first base portion112and the first prism pattern layer113formed on the second surface112bof the first base portion112(improvement of brightness performance).

FIG.6Ais a liquid crystal panel image and drawings of a reversed prism pattern (a first prism pattern layer) and a pyramid pattern showing an outcome from an arrangement of the reversed prism pattern and the pyramid pattern according to a certain embodiment.FIG.6Bis a liquid crystal panel image and drawings of a reversed prism pattern (a first prism pattern layer) and a pyramid pattern showing an outcome from an arrangement of the reversed prism pattern and the pyramid pattern according to an embodiment.

It is very important for the optical film100ofFIGS.1to5Bdescribed above to have high brightness, but it may also be very important to prevent or minimize the moiré phenomenon. The moiré phenomenon will be described in detail below, but the moiré phenomenon may be easily occurred or never occurred by varying a parameter and/or a pattern arrangement of the pyramid pattern111aof the pyramid pattern layer111and the prism pattern of the first prism pattern layer113(or the reversed prism pattern layer).

For example, as shown inFIGS.6A and6B, when the pyramid pattern111aof the pyramid pattern layer111and the prism pattern of the first prism pattern layer113are arranged, the moiré phenomenon may be easily occurred or never occurred depending on the difference between the parameter of the pyramid pattern111aand the parameter of the prism pattern (referred to as ‘numerical difference in parameters’). Here, the parameter may be, for example, a parameter for length, and in this case, for example, ‘numerical difference in parameters’ may mean the difference between the pitch of the pyramid pattern and the pitch of the prism pattern.

According to an embodiment of the present disclosure, the pyramid pattern layer111may include a plurality of pyramid patterns111awith a first pitch ‘pi1’ and the first prism pattern layer113(or the reversed prism pattern layer) may include a plurality of prism patterns with a second pitch ‘pi2’. Here, the first pitch ‘pi1’ of the pyramid pattern111amay be defined as the length of the sides ‘a1’ and ‘a2’ of the pyramid base. The difference in the numerical values of the patterns may mean the difference between the first pitch ‘pi1’ and the second pitch ‘pi2’.

On the other hand, if the pyramid direction of one side of the pyramid base of the pyramid pattern111aand the prism direction of the edge of the prism pattern does not form 0° or 90° but forms more than a predetermined angle (e.g. 30°), the numerical difference between the patterns can be compared with a first prime pitch ‘pi1-1’ corresponding to a diagonal length of the pyramid base of the pyramid pattern111arather than the first pitch ‘pi1’ corresponding to the length of the side of the pyramid base of the pyramid pattern111a. In an embodiment ofFIGS.6A and6B, it can be disclosed whether the moiré phenomenon may be occurred when the half of the diagonal length (pi1-1)/2 of the pyramid base of the pyramid pattern113a, not the side lengths of the pyramid base ‘a1’, ‘a2’ of the pyramid pattern113a, is compared with the pitch ‘pi2’ of the prism pattern.

For example, the moiré phenomenon may be occurred in the liquid crystal panel20shown inFIG.6A, but the moiré phenomenon may not be occurred in the liquid crystal panel20shown inFIG.6B. For example,FIG.6Ashows that the moiré phenomenon is occurred when the pitch ‘pi2’ of the prism pattern is 21 μm, the side length of the pyramid base of the pyramid pattern is 30 μm, and the half of the diagonal length of the pyramid pattern is 21.21 μm. For example,FIG.6Bshows that the moiré phenomenon is not occurred when the pitch ‘pi2’ of the prism pattern is 13 μm, the side length of the pyramid base of the pyramid pattern is 30 μm, and the half of the diagonal length of the pyramid base of the pyramid pattern is 21.21 μm. Through this, it can be confirmed that the moiré phenomenon may be occurred when the length of a certain parameter of the pyramid pattern (e.g., half of the diagonal length) and the pitch length of the prism pattern are similar, and that the moiré phenomenon may not be occurred when the length of the pitch of the prism pattern is similar. In some embodiments of the present specification, when the pitch of the pyramid pattern and the pitch of the prism pattern are similar, the term ‘similar’ means, for example, if they have the same value when the value below the decimal point at two different pitches in micrometers (μm) was discarded, they can be said to be similar. Alternatively, the term ‘similar’ may be said to be similar when, for example, the difference between two different pitches is less than 3% of the total pitch length of one pattern.

FIG.7is a perspective view showing a liquid crystal display (LCD) device including an optical film according to an embodiment.FIG.8Ais drawings illustrating an arrangement of a pyramid pattern and a prism pattern according to various embodiments.FIG.8Bis a table showing optical characteristics of an optical film according to various embodiments.FIG.9Ais drawings illustrating an arrangement of a pyramid pattern and a prism pattern according to various embodiments.FIG.9Bis a table showing optical characteristics of an optical film according to various embodiments.

Through the embodiments ofFIGS.8A to9B, various optical properties of the optical film according to various arrangements of the pyramid pattern111aof the pyramid pattern layer111and the prism pattern of the first prism pattern layer113can be confirmed. Here, various arrangements of the pyramid pattern and prism pattern may mean various angle differences between the pyramid pattern and the prism pattern. The various angles between the pyramid pattern and the prism pattern may refer to the angle between one side of the pyramid base of the pyramid pattern and the edge direction (e.g., P1inFIG.1) of the prism pattern (e.g., the first prism pattern) (referred to as ‘in-between angle α’).

In embodiments inFIGS.8A to9B, simulation results can be shown by varying the angle difference between the pyramid pattern and the prism pattern in a case where the edge direction of the prism pattern is perpendicular to the arrangement direction of the light source (e.g., LED) (or in a case where the edge direction of the prism pattern is parallel to the incident direction of light emitted from a light source (e.g., LED)) when the side length of the pyramid base of the pyramid pattern is 30 μm and the pitch of the prism pattern is 21 μm. InFIGS.8B and9B, the viewing angle distribution1may show optical characteristics for light measured between the first sheet110and the second sheet120as shown inFIG.7and the viewing angle distribution2may show the optical characteristics for light measured between the third sheet130and the diffusion sheet17.

Referring toFIGS.8A and8B, when the angle (a, alpha) formed between the pyramid direction of one side of the pyramid base of the pyramid pattern111aand the edge direction (shown by an arrow) of the prism pattern is 90°, the brightness can be 63.2%, when the angle ‘α’ is 75°, the brightness can be 73.4%, and when the angle ‘α’ is 60°, the brightness can be 91.7%. Meanwhile, when the angle ‘α’ formed between the pyramid direction of one side of the pyramid base of the pyramid pattern111aand the edge direction of the prism pattern (shown by an arrow) is 45°, the brightness may be 100.0%. Referring toFIGS.9A and9B, when the angle ‘α’ formed between the pyramid direction of one side of the pyramid base of the pyramid pattern111aand the edge direction of the prism pattern (shown by an arrow) is 30°, the brightness may be 90.3%, when the angle ‘α’ is 15°, the brightness may be 74.4%, and when the angle ‘α’ is 0°, the brightness may be 64.4%. When all other conditions are the same as above, it can be seen that the brightness according to the angle ‘α’ formed between patterns has the highest value at an angle of 45° when going from 90° to 0°.

Through the embodiments inFIGS.8A to9B, it can be confirmed that the highest brightness can be achieved between the pyramid pattern111aof the pyramid pattern layer111and the prism pattern of the first prism pattern layer113when the in-between angle ‘α’ formed between the pyramid direction of one side of the pyramid base of the pyramid pattern111aand the edge direction of the prism pattern is 45°. From another perspective, it may be viewed as having the highest brightness when the diagonal length direction of the pyramid base of the pyramid pattern111aof the pyramid pattern layer111and the edge direction of the prism pattern are perpendicular to each other.

FIG.10Ais a table showing the moiré phenomenon simulation results according to various embodiments.FIG.10Bis a table showing the moiré phenomenon simulation results according to various embodiments.

FIGS.10A and10Bshow the results of the moiré phenomenon simulation of the optical film100with respect to the angle (in-between angle, a) formed between the pyramid direction of the pyramid pattern111aof the pyramid pattern layer111and the prism edge direction of the prism pattern of the first prism pattern layer113.FIG.10Ashows the degree of the moiré phenomenon with respect to various angles (in-between angle, a) when the side length of the pyramid base of the pyramid pattern111aof the pyramid pattern layer111is 30 μm and the pitch of the prism pattern of the first prism pattern layer113is 21 μm.FIG.10Bshows the degree of the moiré phenomenon with respect to various angles (in-between angle, α) when the side length of the pyramid base of the pyramid pattern111aof the pyramid pattern layer111is 30 μm and the pitch of the prism pattern of the first prism pattern layer113is 30 μm. Here, the moiré phenomenon can be observed in the liquid crystal panel20ofFIG.1.

Referring toFIG.10A, it can be confirmed that the degree of the moiré phenomenon occurrence is the greatest at 45° when the pyramid pattern111aof the pyramid pattern layer111and the prism pattern of the first prism pattern layer113has the in-between angle ‘α’ of 0°, 15°, 30°, 40°, 45°, 50°, 60°, 75°, and 90°, respectively. In addition, it can be confirmed that some moiré phenomenon is occurred even at 40° and 50° which are around 45°. Referring toFIG.10B, it can be confirmed that the degree of moiré phenomenon occurrence is the greatest at 0° and 90°. InFIG.10B, unlikeFIG.10A, it can be confirmed that moiré phenomenon is not occurred at 45°. As can be seen through the embodiments ofFIGS.10A and10B, for example, when the in-between angle ‘α’ formed between the pyramid direction of one side of the pyramid base of the pyramid pattern111aand the edge direction (shown by an arrow) of the prism pattern is 0°, 45°, or 90°, the moiré phenomenon may be occurred depending on the relationship between the length of the side of the pyramid base and/or the diagonal of the pyramid base of the pyramid pattern and the pitch of the prism pattern.

For example, if the length of one side of the pyramid base of the pyramid pattern111aand the pitch of the prism pattern are similar, the moiré phenomenon may be occurred when the in-between angle ‘α’ formed between the pyramid direction of one side of the pyramid base of the pyramid pattern111aand the edge direction of the prism pattern is 0° or 90°. In addition, for example, when the half of the diagonal length of the pyramid base of the pyramid pattern111aand the pitch of the prism pattern are similar, the moiré phenomenon may be occurred when the in-between angle ‘α’ formed between the pyramid direction of one side of the pyramid base of the pyramid pattern111aand the edge direction of the prism pattern is 45°. As such, to provide an optical film having high brightness characteristics without causing the moiré phenomenon, it must be designed by considering the angle (in-between angle) formed between the pyramid pattern and the prism pattern as well as the numerical relationship of the parameters. Below, referring toFIGS.11A to11D, the in-between angle and the pitch length conditions for providing an optical film having high brightness characteristics without causing the moiré phenomenon will be examined in more detail.

FIG.11Ais a drawing showing an arrangement of a pyramid pattern and a prism pattern according to an embodiment.FIG.11Bis a drawing showing an arrangement of a pyramid pattern and a prism pattern according to an embodiment.FIG.11Cis a drawing showing an arrangement of a pyramid pattern and a prism pattern according to an embodiment.FIG.11Dis a drawing showing an arrangement of a pyramid pattern and a prism pattern according to one embodiment.

FIGS.11A to11Dshow the arrangement relationship between the pyramid pattern111aof the pyramid pattern layer111and the prism pattern of the first prism pattern layer113, and they are the ones for varying the in-between angles formed between the pyramid direction of one side of the pyramid base of the pyramid pattern111aand the prism pattern while one vertex v1 of the pyramid patter111ais fixed to the edge of the prism pattern.FIG.11Ashows when the in-between angle ‘α’ formed between the pyramid direction of one side of the pyramid base of the pyramid pattern111aand the prism pattern is 0°,FIG.11Bshows when the in-between angle ‘α’ formed between the pyramid direction of one side of the pyramid base of the pyramid pattern111aand the prism pattern may be 10°,FIG.11Cshows when the in-between angle ‘α’ formed between one side of the pyramid base of the pyramid pattern111aand the prism pattern may be 20°, andFIG.11Dshows when the in-between angle ‘α’ formed between the pyramid direction of one side of the pyramid base of the pyramid pattern111aand the prism pattern may be 45°. InFIGS.11A to11D, the pyramid pattern111ahaving the four side surfaces111-1,111-2,111-3,111-4and the corresponding four sides of the pyramid base111-1′,111-2′,111-3′,111-4′ is disclosed. As a reference for the in-between angle formed between the pyramid pattern and the prism pattern, the second side111-2′ of the pyramid base of the pyramid pattern111acan be used, but this is only an example and another side of the pyramid base (e.g., the first side of the pyramid base111-1′, the third side of the pyramid base111-3′, and the fourth side of the pyramid base111-4′) may also be used.

In the present disclosure, the pyramid pattern111amay have the pyramid base of square shape. For example, the four sides of the pyramid base111-1′,111-2′,111-3′,111-4′ may have substantially the same length, respectively. Here, the expression ‘having substantially the same length’ may mean that each side has the same length within a predetermined margin of error.

Referring toFIGS.11A to11Dtogether, as the in-between angle formed between the pyramid direction of one side of the pyramid base of the pyramid pattern111aand the prism pattern varies, the dominant pitch of the pyramid pattern111a, which affects the moiré phenomenon, may be varied. Here, the dominant pitch may mean that a pitch that has a greater influence on the moiré phenomenon among the first pitch ‘pi1’ corresponding to the length of the side of the pyramid base of the pyramid pattern111aand the first prime pitch ‘pi1-1’ corresponding to the diagonal length of the pyramid base of the pyramid pattern111a. For example, referring toFIG.11A, when the in-between angle ‘α’ formed between the pyramid direction of one side of the pyramid base of the pyramid pattern111aand the prism pattern may be 0°, the first pitch ‘pi1’ corresponding to the length of the side of the pyramid base (e.g., the fourth side of the pyramid base111-4′) of the pyramid pattern111amay be the dominant pitch ‘x1’. The first prime pitch ‘pi1-1’ corresponding to the diagonal length of the pyramid pattern111amay be the dominant pitch ‘x1’ if the first pitch ‘pi1’ maintains the dominant pitch until the in-between angle ‘α’ formed between the pyramid direction of one side of the pyramid base of the pyramid pattern111aand the prism pattern has a predetermined angle difference (e.g., less than approximately 10°), and then the in-between angle is increased beyond the predetermined angle difference. Referring toFIG.11B, when the in-between angle ‘α’ formed between the pyramid direction of one side of the pyramid base of the pyramid pattern111aand the prism pattern may be 10°, the first prime pitch ‘pi1-1’ corresponding to the diagonal length of the pyramid pattern111amay be the dominant pitch ‘x2’. Referring toFIG.11C, when the in-between angle ‘α’ formed between the pyramid direction of one side of the pyramid base of the pyramid pattern111aand the prism pattern may be 20°, the first prime pitch ‘pi1-1’ corresponding to the diagonal length of the pyramid base of the pyramid pattern111amay be the dominant pitch ‘x3’. Referring toFIG.11D, when the in-between angle ‘α’ formed between the pyramid direction of one side of the pyramid base of the pyramid pattern111aand the prism pattern may be 45°, the first prime pitch ‘pi1-1’ corresponding to the diagonal length of the pyramid base of the pyramid pattern111amay be the dominant pitch ‘x4’.

Referring toFIGS.10A and10Bagain, in a case where the length of one side of the pyramid base of the pyramid pattern111aand the pitch of the prism pattern are similar, the moiré phenomenon may be occurred when the in-between angle ‘α’ formed between the pyramid direction of one side of the pyramid base of the pyramid pattern111aand the edge direction of the prism pattern is 0° or 90°. Also, for example, in a case where the half of the diagonal length of the pyramid base of the pyramid pattern111aand the pitch of the prism pattern are similar, the moiré phenomenon may be occurred when the in-between angle ‘α’ formed between the pyramid direction of one side of the pyramid base of the pyramid pattern111aand the edge direction of the prism pattern is 45°. Referring toFIG.11Aagain, when the in-between angle ‘α’ formed between the pyramid direction of one side of the pyramid base of the pyramid pattern111aand the edge direction of the prism pattern is 0° or 90°, the first pitch ‘pi1’ corresponding to the length of the side of the pyramid base of the pyramid pattern111abecomes the dominant pitch ‘x1’ thereby causing the moiré phenomenon when the first pitch is similar to the second pitch ‘pi2’ of the prism pattern. Referring toFIGS.11B to11Dagain, when the in-between angle ‘α’ formed between the pyramid direction of one side of the pyramid base of the pyramid pattern111aand the edge direction of the prism pattern is not 0° or 90° (e.g., 10° to 80°), the first prime pitch ‘pi1-1’ corresponding to the diagonal length of the pyramid base of the pyramid pattern111abecomes the dominant pitch ‘x2’, ‘x3’, ‘x4’ thereby causing the moiré phenomenon when the half of the first prime pitch is similar to the second pitch ‘pi2’ of the prism pattern.

The pitch relationship at which the moiré phenomenon is not occurred for the optical film100can be summarized in Equations as follows. To prevent the moiré phenomenon from being occurred for the optical film100, Equation 1 or Equation 2 below must be satisfied.

n·(pi1-1)2<pi⁢2<n·pi⁢1⁢or[Equation⁢1]n·(pi1-1)2>pi⁢2[Equation⁢2]

Here, ‘n’ may be a natural number. Because the second pitch ‘pi2’ should not be matched with multiples of (pi1-1)/2 or multiples of ‘pi1’ to prevent the moiré phenomenon being occurred, a value where ‘n’ times the value of (pi1-1)/2 and the value of ‘pi1’ was applied in Equation 1 and Equation 2.

Referring toFIG.11B, when the in-between angle ‘α’ formed between the pyramid direction of one side of the pyramid base of the pyramid pattern111aand the edge direction of the prism pattern may be a predetermined angle (e.g., 10° or more), the first prime pitch ‘pi1-1’ corresponding to the diagonal length of the pyramid base of the pyramid pattern111abecomes the dominant pitch, and the moiré phenomenon cannot be occurred if the half of the first prime pitch (pi1-1)/2 should not be matched with the second pitch ‘pi2’. Through the illustration ofFIG.11B, generalizingFIGS.11B to11Dresults in the following equation. To prevent the moiré phenomenon from being occurred for the optical film100, Equation 3 below must be satisfied.

n·pi⁢1·(sin⁢α+cos⁢α)2≠pi⁢2[Equation⁢3]

Here, ‘n’ may be a natural number. Because the second pitch ‘pi2’ should not be matched with multiples of (pi1(sin α+cos α))/2 to prevent the moiré phenomenon from being occurred, a value where n times the value of (pi1(sin α+cos α))/2 was applied in Equation 3.

In addition to the condition where the moiré phenomenon is not occurred, the optical film100can satisfy Equation 4 to exhibit high brightness of 90% or more with reference toFIGS.8B and9B.
30°<α<60°  [Equation 4]

FIG.12is a table comparing an embossed pyramid pattern and an intaglio pyramid pattern according to various embodiments. According to various embodiments of the present disclosure, the pyramid pattern111aof the pyramid pattern layer111may be formed as intaglio. Referring toFIG.12, it can be seen as to the difference in brightness value, incident angle θ, and viewing angle Φ for the combination of the intaglio pyramid pattern and the reversed prism pattern compared to the combination of the embossed pyramid pattern and the reversed prism pattern.

Compared to the combination of the embossed pyramid pattern and the reversed prism pattern, the combination of the intaglio pyramid pattern and the reversed prism pattern has better light concentrating efficiency and can have a higher brightness value. The incidence and viewing angles of the combination of the intaglio pyramid pattern and the reversed prism pattern are narrower than those of the combination of the embossed pyramid pattern and the reversed prism pattern. This can be interpreted as the incident and viewing angles moving to the center thereby increasing light concentrating efficiency.

In addition, for the embossed pyramid pattern, because the physical peak portions (e.g., barrier ribs111-5,111-6inFIG.4E) are vulnerable to damage, it may be more advantageous to apply the intaglio pyramid pattern rather than to apply the embossed pyramid pattern. According to an embodiment, the intaglio pyramid pattern applied to the present disclosure may be referred to as a ‘waffle-type pyramid pattern.’

FIG.13is a table showing optical characteristics according to the refractive index of a pyramid pattern layer (referred to as ‘pyramid refractive index’) and a reversed prism pattern layer according to various embodiments. InFIG.13, the alphabet n indicating the refractive index may be shown in front of the number.

According to an embodiment, when considering brightness and color coordinates, it may be advantageous to have the refractive index of the pyramid pattern111aof the pyramid pattern layer111and the refractive index of the prism pattern (reversed prism pattern) of the first prism pattern layer113being smaller than the refractive index of the first base portion112.

Referring toFIG.13, for example, when the refractive index (PET refractive index) of the base portion120of the first sheet110is 1.65, if the refractive index of the pyramid pattern111aof the pyramid pattern layer111(abbreviated as ‘pyramid refractive index’) is varied from 1.49 to 1.58, and then sequentially varied to 1.69 while the refractive index of the prism pattern (reversed prism pattern) of the first prism pattern layer113(abbreviated as ‘reversed prism refractive index’) is fixed at 1.49, changes in optical properties may be occurred. Here, changes in optical characteristics may include, for example, changing of viewing angle distribution, brightness, color coordinates (e.g. Δy), angle of incidence θ, and viewing angle Φ, but for convenience, we will focus on changes in brightness value.

As shown inFIG.13, when sequentially comparing an embodiment with a pyramid refractive index of 1.49 (e.g., example 2-1), an embodiment with a pyramid refractive index of 1.58 (e.g., example 2-2), and an embodiment with a pyramid refractive index of 1.69 (e.g., example 2-3) while the refractive index (PET refractive index) of the base portion120is 1.65 and the reversed prism refractive index is fixed to a low refractive index (e.g., reversed prism refractive index of 1.49), it can be confirmed that the brightness has been changed. For example, when the pyramid refractive index is close to or has a higher value (e.g., 1.69) than the refractive index of the base portion120(i.e., when the pyramid refractive index is higher than the refractive index of the base portion (e.g., example 2-3)), it can be confirmed that the brightness value is significantly lowered compared to the cases where the pyramid refractive index is 1.49 and 1.58 (i.e., when the pyramid refractive index is lower than the refractive index of the base (e.g., example 2-1, 2-2, 2-4)).

Referring to another embodiment ofFIG.13(e.g., example 2-4), when the refractive index (PET refractive index) of the base portion120is 1.65, it can be confirmed that the brightness is decreased even when the refractive index of the portion120is close to or has a higher value (e.g., 1.69) (i.e., when the refractive index of the reversed prism is higher than the refractive index of the base portion) even if the pyramid refractive index is 1.49 which is a low refractive index. Referring to the various embodiments ofFIG.13, when each of the refractive index of the reversed prism and the refractive index of the pyramid is smaller than the refractive index of the base portion (e.g., example 2-1, 2-2), a high brightness value may be achieved. However, when at least one of the refractive index of the reversed prism and the refractive index of the pyramid is higher than the refractive index of PET (e.g., examples 2-3, 2-4), it can be confirmed that it does not have a higher brightness value than when each of the refractive index of the reversed prism and the refractive index of the pyramid is smaller than the refractive index of the base portion (e.g., example 2-1, 2-2). In summary, embodiments where the refractive index of the reversed prism and the refractive index of the pyramid are both formed to be lower than the refractive index of the base portion can be applied to the present disclosure.

It should be noted, however, that the specific values of the refractive index shown inFIG.13are exemplary except the characteristics of the high-low relationship among the refractive index of the base (PET refractive index), the pyramid refractive index, and the prism refractive index which are factors causing the deterioration of the optical properties. Accordingly, the values of the base portion refractive index (PET refractive index), the pyramid refractive index, and the prism refractive index may be partially changed depending on the embodiment.

According to an embodiment of the present disclosure, the optical film may include the first base portion; the pyramid pattern layer where a plurality of pyramid patterns having the first pitch ‘pi1’ are formed on the first surface of the first base portion; and the first prism pattern layer where a plurality of prism patterns having the second pitch ‘pi2’ are formed on the second surface of the first base portion. The optical film may satisfy Equation 1 or Equation 2 when the diagonal length of the pyramid pattern has the first prime pitch ‘pi1-1’:

n·(pi1-1)2<pi⁢2<n·pi⁢1⁢or[Equation⁢1]n·(pi1-1)2>pi⁢2,[Equation⁢2]
where n is a natural number.

According to an embodiment, the optical film may satisfy Equation 3 with respect to the in-between angle ‘α’ formed between the pyramid direction of one side of the pyramid base of the pyramid pattern and the edge direction of the prism pattern:

n·pi⁢1·(sin⁢α+cos⁢α)2≠pi⁢2,[Equation⁢3]
where n is a natural number.

According to an embodiment, the in-between angle ‘α’ formed between the pyramid direction of one side of the pyramid base of the pyramid pattern and the edge direction of the prism pattern may satisfy Equation 4:
30°<α<60°  [Equation 4].

According to an embodiment, the plurality of pyramid patterns may be formed as intaglio. According to an embodiment, the second sheet disposed over the first sheet may further include the second base portion and a second prism pattern layer having a plurality of prism patterns formed on the first surface of the second base portion. According to an embodiment, the second sheet may include the first diffusion layer formed on the second surface of the second base portion and facing the pyramid pattern layer.

According to an embodiment, the third sheet is disposed over the second sheet may further include the third base portion and the third prism pattern layer having a plurality of prism patterns formed on the first surface of the third base portion. According to an embodiment, the third sheet may include the second diffusion layer formed on the second surface of the third base portion and facing the second prism pattern layer.

According to an embodiment, the plurality of first prism patterns may have edges formed toward the first prism direction, the plurality of second prism patterns may have edges formed toward the second prism direction, and the plurality of third prism patterns may have edges formed toward the third prism direction which is perpendicular to the second prism direction. According to an embodiment, each of the refractive index of the pyramid pattern layer and the refractive index of the first prism pattern layer may be smaller than the refractive index of the base portion.

The backlight unit comprising the optical film according to the above-described embodiment may include an edge-type light source and the optical film disposed over the light source. According to an embodiment, the edge-type light source may be arranged in the first direction perpendicular to the third prism direction and may be formed to irradiate light in the second direction parallel to the third prism direction.

The optical film of various embodiments of the present disclosure described above and the backlight unit including the optical film are not limited to the above-described embodiments and drawings. Moreover, various substitutions, modifications, and changes are possible for those skilled in the art within the technical scope of the present disclosure. The effects that can be obtained from the present disclosure are not limited to the effects mentioned above, and other effects not mentioned can be clearly understood by those skilled in the art from the description above.