KR20040024725A - Optical Film and its Manufacturing Method and Back-light Unit For Liquid Crystal Display Using the Same - Google Patents

Abstract

The present invention discloses an optical film, a method of manufacturing the same, and a backlight unit for a liquid crystal display device using the same. According to this, a plurality of square-pyramidal protrusions which are prism patterns are formed in the board | substrate of an optical film. At this time, the protrusions are arranged repeatedly in the X and Y-axis directions that are orthogonal to each other or spaced apart from each other without being spaced apart from each other. In this case, the protrusion may include a cone, a triangular pyramid, a pentagonal pyramid, and a polygonal pyramidal shape such as a hexagonal pyramid. In addition, the protrusion may be formed in a multilayer structure on the substrate. In addition, the protrusions may be formed on one side or both sides of the substrate.

Therefore, the present invention can obtain uniform and high luminance while using one optical film, and can also make the thickness of the backlight unit thin. In addition, the present invention can easily produce an optical film using a flexible molding, it is possible to achieve a cost reduction of the optical film.

Therefore, the present invention can not only achieve high brightness of the backlight unit, but also enhance the price competitiveness of the backlight unit and the liquid crystal display device.

Description

Optical film and its manufacturing method and back-light unit for liquid crystal display using the same}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight unit for a liquid crystal display device, and more particularly, to an optical film, a method of manufacturing the same, and a backlight unit using the same, to improve brightness while using one sheet.

In recent years, the proportion of the flat panel display in the information display device is gradually increasing. Liquid crystal displays, which are one of flat panel displays, are widely used in monitors such as portable video cameras, televisions, car navigation systems, or personal computers.

A liquid crystal display device, particularly a transmissive liquid crystal display device, uses a backlight unit as a light source because it does not emit light by itself and only adjusts transmittance. The role and function of the backlight unit in such a liquid crystal display device has emerged as an important problem over time. This is because the size and the light efficiency of the liquid crystal display are significantly changed according to the change of the structure of the backlight unit, which affects the mechanical and optical properties of the overall liquid crystal display.

The liquid crystal display is classified into a direct method and an edge method according to the light source arrangement of the backlight unit. The direct method is to place the light source on the back of the panel where the image is displayed and direct light toward the front of the panel. The edge method is to arrange the light source on the side of the light guide plate to reflect the light passing through the light guide plate toward the front of the panel. It is a way of dimming.

At present, the edge type backlight unit is mainly used. The structure of the edge type backlight unit is disclosed in detail in US Patent No. 5,567,042, US Patent No. 5,592,193, US Patent No. 5,608,553, US Patent No. 5,640,483, and the like. In the backlight unit, a plurality of sheets are interposed between the light guide plate and the panel. These sheets consist of a combination of a diffusion sheet, an optical film and a protective sheet, for example.

The conventional backlight unit for a liquid crystal display device is configured as shown in FIG. That is, in FIG. 1, the lamp unit 10 is disposed on the left side of the light guide plate 20, and the reflecting plate 30 is disposed on the rear surface of the light guide plate 20. In addition, the diffusion sheet 40, the prism sheet 50, and the protective sheet 60 are disposed on the front surface of the light guide plate 20 in the order of going up from the bottom. In addition, a panel 70 in which liquid crystal cells (not shown) are formed on the protective sheet 60 is disposed. Each of these components is stably stored in the storage space of the frame 80.

Here, the lamp unit 10 includes a fluorescent lamp 11 which is a line light source and a lamp reflector 13 which surrounds the lamp 11 and reflects the light from the lamp 11 to the light guide plate 20. The light guide plate 20 serves to guide the light source from the lamp unit 10 to the front surface of the light guide plate 20 by changing the line light source to the surface light source. The reflecting plate 30 reflects a part of the light passing through the rear surface of the light guide plate 20 of the lamp unit 10 toward the front surface of the light guide plate 20 again. The diffusion sheet 40 uniformly diffuses the light exiting the entire surface of the light guide plate 20. The prism sheet 50 condenses the light passing through the diffusion sheet 40 in a direction perpendicular to the front surface of the light guide plate 20, that is, the emission surface, and emits the light toward the panel 70. Thus, image information can be displayed on the panel 70.

By the way, the conventional prism sheet 50 has a structure in which the first prism sheet 51 and the second prism sheet 53 thereon are stacked. In addition, the front surface of the first prism sheet 51 triangulates an arbitrary pattern, for example, a cross section, in order to focus the light exiting the light guide plate 20 of FIG. 1 in a direction perpendicular to the exit surface of the light guide plate 20. A plurality of protrusions 52 forming a straight line extend in the same direction. Similarly, the front surface of the second prism sheet 53 is arranged with a plurality of triangular projections 54 extending linearly in the same direction. At this time, the first and second prism sheets 51 and 53 are disposed such that the extending directions of the protrusions 52 and 54 cross at right angles to each other.

However, in the related art, since the prism sheet 50 is composed of two first and second prism sheets 51 and 53, the light passing through the diffusion sheet 40 is each of the first and second prism sheets 51. Each time it passes through, 53, the luminance is degraded. As a result, the optical brightness after passing through the conventional backlight unit remains at a relatively low level. As a result, it is difficult to achieve high luminance in a liquid crystal display device using a conventional backlight unit.

Furthermore, although the first and second prism sheets 51 and 53 are expensive, they are essential parts of the backlight unit which must be purchased from a specific company. This is one factor that makes it difficult to reduce the cost of the backlight unit.

In order to solve these problems, improvements to the conventional prism sheet have been studied, but there are no practical solutions yet, so the expensive prism sheet has to be continuously used for two sheets of the conventional backlight unit.

Accordingly, it is an object of the present invention to achieve high luminance of an optical film while reducing the quantity of optical film used.

Another object of the present invention is to achieve a cost reduction of the optical film and to further reduce the cost of the backlight unit.

Still another object of the present invention is to lower the cost of the optical film by easily manufacturing the optical film.

Still other objects of the present invention will become more apparent from the following detailed description and the accompanying drawings.

1 is an exploded perspective view showing a backlight unit for a liquid crystal display according to the prior art.

Figure 2 is a plan view showing an example in which the projecting portion of the square pyramid shape is disposed on one surface of the optical film according to the present invention without a spaced interval.

Figure 3 is a longitudinal sectional view showing the projection of the square pyramid of Figure 2;

Figure 4 is a plan view showing an example in which the projections of the square pyramid shape is disposed at a spaced interval on one surface of the optical film according to the present invention.

Figure 5 is a longitudinal sectional view showing the projection of the square pyramid of Figure 4;

Figure 6 is a longitudinal cross-sectional view showing an example in which the projection of the rectangular pyramid shape is laminated in multiple layers on one surface of the optical film according to the present invention.

Figure 7 is a longitudinal sectional view showing an example in which the projections of the square pyramid shape are arranged on both sides of the optical film according to the present invention.

8 is a process flowchart illustrating a method of manufacturing the optical film of FIG. 2.

9 is a process flowchart showing a method of manufacturing the optical film of FIG. 6.

10 is a process flowchart showing a method of manufacturing the optical film of FIG. 7.

11 is an exploded perspective view showing a backlight unit for a liquid crystal display device using the optical film according to the present invention.

12 is a graph illustrating a relationship between luminance and a viewing angle of the backlight unit of FIG. 11.

The optical film according to the present invention for achieving the above object

Transparent substrates; And a protrusion protruding in a predetermined horn shape on one surface of the substrate and arranged in a plurality in a direction orthogonal to each other, condensing and exiting light incident from the substrate.

Preferably, the protrusions may be arranged without spaced apart from each other. In addition, the protrusions may be arranged at predetermined intervals, preferably at intervals of 0.1 to 1 times the pitch of the protrusions.

Preferably, the protrusion may be made of any one of a triangular pyramid, a square pyramid, a pentagonal pyramid, a hexagonal pyramid, and a polygonal pyramid shape and a cone shape.

Preferably, it is preferable that the protrusion protrudes at an angle of 20 ° to 90 ° toward the apex of the protrusion. Pitch of the protrusion may be in the range of 10 ~ 200μm.

Preferably, the protrusions may be stacked in a multilayer structure of one or more layers. A predetermined mirror layer is interposed between the protrusions of the multilayer structure.

Preferably, the protrusion may protrude on the other surface of the substrate facing one surface of the substrate.

Preferably, the protrusion may be made of a material higher than the refractive index of the mirror layer.

Moreover, the manufacturing method of the optical film by this invention is

Coating a thin film of a predetermined resin solution on one surface of the transparent substrate; Temporarily hardening the thin film into flexible protrusions having a predetermined horn shape, which is a prism pattern, by flexible molding; And completely curing the protrusions.

Preferably, the protrusion can be temporarily cured by thermal curing, or temporarily cured by photocuring in a manner of irradiating light through the flexible mold.

Preferably, the step of temporarily hardening the thin film into the horn-shaped protrusions may be performed by stacking a predetermined mirror layer on the substrate including the temporary hardened protrusions and forming the protrusions by the flexible molding on the mirror layer. It may include the step of forming the multilayer structure of the protrusion by additionally performing one or more times the process of hardening while molding.

Preferably, when the thin film is coated on one surface of the substrate, the thin film may be coated on the other surface facing the one surface of the substrate.

In addition, the backlight unit for a liquid crystal display device using the optical film according to the present invention is

A lamp unit including a fluorescent lamp serving as a line light source and a lamp reflecting plate surrounding the lamp and reflecting light from the lamp; A light guide plate disposed on one side of the lamp unit and configured to change the line light source from the lamp unit into a surface light source and to guide the light to an emission surface; And a plurality of protrusions having a predetermined horn shape arranged in an upper portion of the light guide plate so as to intersect with each other, condensing the light passing through the light guide plate in a direction perpendicular to the exit surface of the light guide plate and emitting the light toward the panel. It is characterized by including an enteric optical film.

Preferably, the light guide plate may include a diffusion sheet disposed between the light guide plate and the optical film to uniformly diffuse light emitted from the light guide plate toward the optical film.

Therefore, the present invention can obtain uniform and high luminance while using one optical film, and can also make the thickness of the backlight unit thin. In addition, the present invention can easily produce an optical film using a flexible molding, it is possible to achieve a cost reduction of the optical film.

Hereinafter, an optical film, a method of manufacturing the same, and a backlight unit for a liquid crystal display device using the same according to the present invention will be described in detail with reference to the accompanying drawings. The same code | symbol is attached | subjected to the part of the same structure and the same action as the conventional part.

2 is a plan view showing an example in which the rectangular pyramid-shaped protrusions are disposed on one surface of the optical film according to the present invention without a spaced interval, and FIG. 3 is a longitudinal cross-sectional view of the rectangular pyramid-shaped protrusions of FIG. 2.

2 and 3, in the optical film 150 of the present invention, a plurality of protrusions 153 having the same shape as a prism pattern protrude upward on only one surface of the substrate 151. In this case, the protrusions 153 are adjacent to each other without being spaced apart from each other, and are repeatedly arranged in the X and Y axis directions perpendicular to each other.

Here, the protrusion 153 forms a square pyramid shape such as a pyramid shape. That is, the bottom portion of the protrusion 153 forms a square shape, preferably a square shape, and each side portion of the protrusion 153 is narrowed upward to form a triangular shape forming one vertex (C). In addition, P represents the pitch Pitch which is the distance between the vertices C of the protruding portions 153 adjacent to each other, preferably in the range of 10 to 200 m. H represents the height of the protrusion 153. (theta) shows the angle which the protrusion part 153 protruded toward the vertex C, Preferably it exists in the range of 20 degrees-90 degrees.

In addition, the first, second surfaces 1531, and 1533 of the protrusion 153 collect and emit incident light in the X-axis direction incident from the rear surface of the substrate 151 in the Z-axis direction perpendicular to the X-axis and the Y-axis. Let's do it. In addition, the third, fourth surfaces 1535, and 1537 of the protrusion 153 collect and emit incident light in the Y direction incident from the rear surface of the substrate 151 in the Z axis direction perpendicular to the X and Y axes. .

In addition, the substrate 151 is made of a transparent material, for example, a plate of a material such as polyethylene terephthalate (PET), and the protrusion 153 is formed of a resin material having an arbitrary refractive index and transparency. The said resin can also contain a thermosetting agent or a photocuring agent.

Meanwhile, the protrusion 153 may form a square pyramid shape as shown in FIG. 2, and may also form a cone, a triangular pyramid, a pentagonal pyramid, a hexagonal pyramid, or more polygonal pyramid shapes, although not shown in the drawing. For convenience of description, detailed description thereof will be omitted in order to avoid duplication of description.

Figure 4 is a plan view showing an example in which the rectangular pyramid-shaped protrusions are disposed at a spaced interval on one surface of the optical film according to the present invention, Figure 5 is a longitudinal cross-sectional view showing the rectangular pyramid-shaped protrusions of FIG. The same code | symbol is attached | subjected to the part which has the same structure and the same effect | action as the part of FIG. 2 and FIG.

4 and 5, except that the protrusion 153 is disposed adjacent to one surface of the substrate 151 with a spaced interval W therebetween, FIGS. 2 and 3. It is comprised similarly to the optical film 150 of. Here, it is preferable that the space | interval space | interval W exists in the range of 0.1-1 time of the pitch P. FIG.

Figure 6 is a longitudinal cross-sectional view showing an example in which the projections of the rectangular pyramid shape is laminated in multiple layers on one surface of the optical film according to the present invention. The same code | symbol is attached | subjected to the part which has the same structure and the same effect | action as the part of FIG. 2 and FIG.

Referring to FIG. 6, in the optical film 350 of the present invention, a transparent mirror layer 155 is stacked on the protrusion 153 and a protrusion 157 having the same shape as the protrusion 153 on the mirror layer 155. Except that is disposed, it is configured in the same manner as the optical film 150 of FIGS. Here, the protrusion is preferably made of a material higher than the refractive index of the mirror layer.

Fig. 7 is a longitudinal sectional view showing an example in which protrusions having a square pyramid shape are disposed on both surfaces of an optical film according to the present invention. The same code | symbol is attached | subjected to the part which has the same structure and the same effect | action as the part of FIG.

Referring to FIG. 7, the optical film 450 of the present invention is the same as the optical film 150 of FIGS. 2 and 3 except that the protrusions 153 are disposed on both upper and lower surfaces of the substrate 151. Is configured.

Therefore, since the present invention uses one optical film as shown in Figs. 2 to 7, the cost of the optical film is reduced compared to using the conventional first and second optical films 51 and 53. You can get In addition, the present invention can reduce the thickness of the backlight unit by reducing the thickness of the optical film, and further it is possible to realize the miniaturization of the liquid crystal display device. Optical properties such as brightness and viewing angle for the optical film of the present invention will be described in detail in the backlight unit section described below.

Hereinafter, the manufacturing method of the optical film by this invention is demonstrated with reference to FIG.

8 is a process flowchart showing a method for producing an optical film according to the present invention.

Referring to FIG. 8, first in step S10, a transparent substrate 151 as shown in FIGS. 2 and 3 is prepared. Separately, a resin solution (not shown) having any refractive index and transparency is prepared. Here, a material capable of photo curing or thermal curing may be used as the resin solution.

In step S20, a thin film of the resin solution is formed by coating the resin solution with a uniform thickness on one surface of the substrate 151, that is, the surface corresponding to the emission surface of the optical film. In this case, the thin film may be coated by roller printing or spin coating. In particular, in consideration of mass productivity, the roller printing method is preferred.

In step S30, the thin film of the substrate 151 is pressed by placing the thin film on a support of a soft mold (not shown) and vertically moving the upper mold of the soft mold. At this time, the surface of the upper mold, that is, the surface in contact with the thin film, for example, as shown in Figures 2 and 3, the shape corresponding to the projection 153 of the square pyramidal shape of the prism pattern without spaced apart. When a plurality of orthogonally arranged in the X and Y-axis directions orthogonal to each other are formed, the quadrangular pyramidal protrusions 153 are orthogonal to each other on the substrate 151 without being spaced apart as shown in FIGS. 2 and 3. Are arranged in a plurality of X, Y-axis direction and protruded.

In addition, when the upper mold is made of a transparent material, light such as ultra violet (UV) is irradiated to the thin film through the upper mold for a predetermined time while forming the protrusion 153. Therefore, the protrusion 153 is molded on the substrate 151 and temporarily hardened. Of course, thermal curing may also be used instead of the ultraviolet curing.

Therefore, the flexible mold has the advantages of the conventional injection molding has the advantages of simplifying the process and commercialization of the process, but has a lot of disadvantages that the mold manufacturing cost is expensive, the processing of the optical film is inadequate, the use of the release material is impossible, and the transfer ability is limited. It has many advantages such as simplification of process, minimization of mold manufacturing cost, multi-layering capability, high transferability, high energy efficiency, and the use of various materials. However, there are still disadvantages of insufficient commercialization.

On the other hand, when changing the interval between the pattern formed intaglio on the surface of the flexible mold, as shown in Fig. 4 and 5, the prism pattern of the rectangular pyramidal shape X, orthogonal to each other at arbitrary intervals, A plurality of arrangements in the Y-axis direction may be protruded. Further, in addition to the quadrangular pyramid shape, a cone, a triangular pyramid, a pentagonal pyramid, a hexagonal pyramid or more polygonal pyramid shapes may be formed. For convenience of description, a detailed description thereof will be omitted in order to avoid duplication of description.

In step S40, the upper mold is vertically moved upward to separate the substrate 151 from the substrate 151, and then the substrate 151 is removed from the support, and then the protrusion 153, which is a prism pattern, is further completely cured. Therefore, the optical film 150 of FIG. 2 or the optical film 250 of FIG. 4 is completed.

In addition, in order to manufacture the optical film 350 of FIG. 6 having the protrusion of the multi-layer structure, as shown in FIG. 9, after the steps S10, S20, and S30 of FIG. 8 are performed, step S50. ), The mirror surface layer 155 is laminated on the surface of the substrate 151 protruding from the protrusion 153 thicker than the height of the protrusion 153, and in steps S60 and S70, steps S20 and S70. In the same manner as in (S30), on the mirror surface layer 155, for example, a temporary hardening of the protrusion 157 having the same shape as the protrusion 153 while being soft molded. Here, it is preferable that the refractive indexes of the protrusions 153 and 157 are made of a material higher than the refractive index of the mirror layer 155. For convenience of description, the structure in which the protrusions are laminated in two layers has been described, but it is also possible to make a structure in which the multilayers are stacked in more layers. In step S80, the protrusions of the prism pattern are completely cured in the same manner as in step S40. Thus, the optical film 350 of FIG. 6 is completed.

In addition, in order to manufacture the optical film 450 of FIG. 7 having protrusions formed on both sides of the substrate, as shown in FIG. 10, after step S10 of FIG. 8 is performed, step S20 and step S20 may be performed. Coating the thin film of the resin solution on both sides of the substrate 151 in the same manner, and in step 100, in the same manner as the step (S30) the flexible prism pattern of the rectangular pyramidal shape 153 on both sides of the substrate 151 Temporary hardening while shape | molding. At this time, it is obvious that the shape corresponding to the protrusion 153 is engraved on the upper and lower mold surfaces of the flexible mold. In step S110, the protrusion 153, which is a prism pattern, is completely cured in the same manner as in step S40. Thus, the optical film 450 of FIG. 7 is completed. Of course, multilayer protrusions may be formed on both sides of the substrate 151. For convenience of description, description thereof will be omitted.

Example 1

Poly isocyanate having a refractive index of 1.47, poly thiol having a refractive index of 1.63, and a thermosetting agent were sufficiently mixed at 49 wt%, 50 wt%, and 1 wt%, respectively, to prepare a desired resin solution. For example, the air bubbles contained in the resin solution are removed by leaving the vacuum in a vacuum oven at room temperature for a predetermined time. The thin film of the resin solution is coated with a thickness of 50 μm on one surface of a substrate of 75 μm thick transparent material, for example, polyethylene terephthalate (PET). The thin film is temporarily cured by heat curing for 2 hours at a constant temperature of, for example, 60 ° C. while forming a protrusion by a flexible mold. At this time, the bottom face of the protrusion is, for example, a square pyramidal shape having a square shape, and an angle side of the square is 25 μm. The angle between opposite sides is 90 °. The substrate is separated from the flexible mold and then the protrusions are fully cured for 1 hour at a temperature of 90 ° C.

Example 2

Poly isocyanate having a refractive index of 1.47, poly thiol having a refractive index of 1.63, and a photocuring agent were sufficiently mixed at 49 wt%, 50 wt%, and 1 wt%, respectively, to form a resin solution. Bubbles contained in the resin solution are removed by leaving the vacuum in a vacuum oven at room temperature for a predetermined time. A thin film of the resin solution is coated on one surface of a substrate of 75 μm thick transparent polyethylene terephthalate (PET) to 50 μm thick. The thin film is temporarily cured by irradiating for 30 seconds through the flexible mold with ultraviolet light from an ultraviolet lamp, for example, a 300W xenon (Ze) lamp while shaping a square pyramidal protrusion by a transparent flexible mold. After the substrate is separated from the flexible mold, the protrusion is irradiated with ultraviolet rays for 1 minute to completely cure.

Example 3

One side of the substrate of 50 μm, 75 μm or 100 μm thick transparent polyethylene terephthalate (PET) is coated with UV curable one-component resin, for example acrylate resin, to 50 ?? m thick. The thin film is molded by a transparent flexible mold and irradiated with UV light for 5 minutes using two or more of 5W fluorescent lamps having a center wavelength of 365 nm, for example.

Example 4

After forming the protrusions as in Example 1, the mirror layer of the acrylate resin of Example 3 was formed to a thick thickness enough to completely fill the recesses between the protrusions. The protrusions of the multilayered structure are formed on the mirrored layer by the method of Example 1 again. Here, the refractive index of the protrusion may be made of a material higher than the refractive index of the mirror layer.

Example 5

Projections are formed by the method of Example 1 on both the upper and lower surfaces of a 100 μm-thick transparent polyethylene terephthalate (PET) substrate. On the other hand, in order to prevent the moire phenomenon (interference fringe) occurs, the protrusions on the upper and lower surfaces of the substrate is different in size and spacing.

Therefore, in the present invention, since the thin film of the resin solution is soft-molded using a flexible mold, it is possible to more precisely and quickly produce an optical film in which prism patterns such as square pyramidal protrusions are arranged. Furthermore, since the use of a transparent soft mold enables heat curing or light curing during the molding process, manufacturing time can be shortened and manufacturing productivity can be improved as compared with conventional injection molding. As a result, cost reduction of the optical film is possible. This can enhance the price competitiveness of the backlight unit and further enhance the price competitiveness of the liquid crystal display device.

Hereinafter, a backlight unit for a liquid crystal display device using the optical film according to the present invention will be described with reference to FIG. 11.

11 is an exploded perspective view showing a backlight unit for a liquid crystal display device using the optical film according to the present invention. The same code | symbol is attached | subjected to the part of the same structure and the same action as the conventional part.

Referring to FIG. 11, in the backlight unit of the present invention, the lamp unit 10 is disposed on the left side of the light guide plate 20, and the reflector plate 30 is disposed on the rear surface of the light guide plate 20. In addition, a protective sheet for protecting the damage of the diffusion sheet 40, the optical film 150 of Figs. 2 and 3, the optical film 150 in the order of ascending from the bottom to the front surface, which is the exit surface of the light guide plate 20 60 is disposed. In addition, a panel 70 in which liquid crystal cells (not shown) are formed on the protective sheet 60 is disposed. Each of these parts is stably stored in the storage space of the mold frame 80.

Here, the lamp unit 10 includes a fluorescent lamp 11 which is a line light source and a lamp reflector 13 which surrounds the lamp 11 and reflects the light from the lamp 11 to the light guide plate 20.

The light guide plate 20 plays a role of guiding the light source from the lamp unit 10 to a plane light source and outputting the light source to the exit surface of the light guide plate 20. The rear surface of the light guide plate 20 forms an inclined surface so that the thickness of the light guide plate 20 becomes thinner as it moves away from the lamp unit 10. A plurality of reflective dots (not shown) may be formed on the rear surface of the light guide plate 20 to reflect the light from the lamp unit 10. The reflective dot is formed in a small size to reduce the amount of light reflection in the region adjacent to the lamp unit 10, and is formed in a relatively large size in order to increase the amount of light reflection in an area spaced more than a predetermined distance from the lamp unit 10. . Therefore, the light guide plate 20 can emit light uniformly over the entire emission surface, and can obtain a uniform luminance of light emitted through the light guide plate 20 toward the panel 70.

In addition, the reflector 30 is spaced apart from the rear of the light guide plate 20 by a predetermined distance, even though the reflective dot is formed on the back of the light guide plate 20, the lamp passing through the back of the light guide plate 20 The light from the unit 10 is reflected back to the exit surface of the light guide plate 20.

In addition, the diffusion sheet 40 uniformly diffuses the light emitted from the light guide plate 20 toward the optical film 150. Meanwhile, as shown in the drawing, the diffusion sheet 40 is preferably disposed between the light guide plate 20 and the optical film 150. However, since the diffusion sheet 40 may not necessarily be disposed, the diffusion sheet 40 may be disposed as necessary. It may be omitted.

In addition, the optical film 150 condenses the light passing through the diffusion sheet 40 in a direction perpendicular to the emission surface of the light guide plate 20 and emits the light toward the panel 70. In this case, as shown in FIGS. 2 and 3, the protrusions of the optical film 150 may be arranged without spaced apart to form a square pyramid shape. Although the protrusions are shown as being arranged in the shape of a square pyramid without spaced apart, it is also possible to form a conical or triangular pyramid, pentagonal pyramid, hexagonal pyramid or more polygonal pyramid shape. In addition, the protrusions may be arranged at regular intervals, as shown in FIGS. 4 and 5. In addition, the protrusion may have a multi-layer structure as shown in FIG. 6 or may be formed on both sides of the substrate as shown in FIG.

At this time, as shown in FIG. 2, the first, second surfaces 1531, and 1533 of the protrusion 153 of the optical film 150 may transmit incident light in the X-axis direction perpendicular to the X-axis and the Y-axis. Condenses in a direction to exit toward the panel 70. In addition, the third and fourth surfaces 1535 and 1537 of the protrusion 153 collect incident light in the Y direction in the Z-axis direction perpendicular to the X-axis and the Y-axis, and emit the light toward the panel 70. At this time, the measurement result of the brightness is as shown in FIG. That is, it can be seen that the viewing angle of the backlight unit of the present invention is extended by 10 ° to the left and right as compared to the conventional backlight unit disclosed in Japanese Patent Application No. 1992-246225.

Therefore, the present invention can obtain uniform and high brightness optical properties by reducing the optical film used for the backlight unit from two to one. In addition, since the thickness of the optical film can be reduced, the thickness of the backlight unit can be reduced and the liquid crystal display device can be miniaturized.

Furthermore, since the optical film of the present invention is much cheaper than the conventional optical film, it enhances the price competitiveness of the backlight unit and further enhances the price competitiveness of the liquid crystal display device.

As described above, the present invention forms a plurality of protrusions having a rectangular pyramid shape, which is a prism pattern, on the substrate of the optical film. At this time, the protrusions are arranged repeatedly in the X and Y-axis directions that are orthogonal to each other or spaced apart from each other without being spaced apart from each other. In this case, the protrusion may include a cone, a triangular pyramid, a pentagonal pyramid, and a polygonal pyramidal shape such as a hexagonal pyramid. In addition, the protrusion may be formed in a multilayer structure on the substrate. In addition, the protrusions may be formed on one side or both sides of the substrate.

Therefore, the present invention can obtain uniform and high luminance while using one optical film, and can also make the thickness of the backlight unit thin. In addition, the present invention can easily produce the optical film using a flexible molding, it is possible to achieve the cost reduction of the optical film.

Therefore, the present invention can not only achieve high brightness of the backlight unit, but also enhance the price competitiveness of the backlight unit and the liquid crystal display device.

On the other hand, the present invention has been described by showing one specific embodiment, it is obvious that the present invention may be variously modified and implemented by those skilled in the art. Such modified embodiments should not be understood individually from the technical spirit or point of view of the present invention and these modified embodiments should fall within the scope of the appended claims of the present invention.

Claims (18)

Transparent substrates; And An optical film protruding in a predetermined horn shape on one surface of the substrate and arranged in a plurality in a direction orthogonal to each other, comprising an protrusion for collecting and exiting light incident from the substrate. The optical film of claim 1, wherein the protrusions are arranged without spaced apart from each other. The optical film of claim 2, wherein the protrusions are disposed at predetermined intervals. The optical film of claim 3, wherein the protrusions are disposed at a spacing of 0.1 to 1 times the pitch of the protrusions. The optical film according to claim 2 or 3, wherein the protruding portion is one of a triangular pyramid, a square pyramid, a pentagonal pyramid, a hexagonal pyramid, and a polygonal pyramid shape and a cone shape. The optical film according to claim 5, wherein the protrusion protrudes at an angle of 20 ° to 90 ° toward the apex of the protrusion. The pitch of the said projection part exists in the range of 10-200 micrometers, The optical film of Claim 4 characterized by the above-mentioned. The optical film according to any one of claims 1 to 3, wherein the protrusions are laminated in a multilayer structure of one or more layers. The optical film according to claim 8, wherein a predetermined mirror surface layer is interposed between the protrusions of the multilayer structure. The optical film of claim 8, wherein the protrusion protrudes from the other surface of the substrate to face one surface of the substrate. The optical film of claim 9, wherein the protrusion is made of a material having a refractive index higher than that of the mirror layer. Coating a thin film of a predetermined resin solution on one surface of the transparent substrate; Temporarily hardening the thin film into flexible protrusions having a predetermined horn shape, which is a prism pattern, by flexible molding; And And completely curing the protrusions. The manufacturing method of the optical film of Claim 12 which temporarily hardens the said protrusion part by thermosetting. The method of manufacturing an optical film according to claim 12, wherein the protrusion is temporarily cured by photocuring in a manner of irradiating light through the flexible mold. The method of claim 12, wherein the step of temporarily hardening the thin film into the horn-shaped protrusions The multilayer structure of the protrusion is formed by stacking a predetermined mirror layer on the substrate including the temporarily hardened protrusion and additionally performing one or more steps of temporarily hardening the protrusion while forming the protrusion by the flexible molding on the mirror layer. Method for producing an optical film comprising the step of making. The method of claim 12, wherein when the thin film is coated on one surface of the substrate, the thin film is coated on the other surface opposite to the one surface of the substrate. A lamp unit including a fluorescent lamp serving as a line light source and a lamp reflecting plate surrounding the lamp and reflecting light from the lamp; A light guide plate disposed on one side of the lamp unit and configured to change the line light source from the lamp unit into a surface light source and to guide the light to an emission surface; And A plurality of protrusions arranged in an upper portion of the light guide plate and arranged in a direction in which a predetermined horn shape intersects each other, condensing the light passing through the light guide plate in a direction perpendicular to the exit surface of the light guide plate and outputting the light toward the panel; Back light unit for a liquid crystal display device comprising an optical film. 18. The backlight unit of claim 17, further comprising a diffusion sheet disposed between the light guide plate and the optical film to uniformly diffuse light emitted from the light guide plate toward the optical film.