KR100518670B1 - Optical film with micro conic lens array and back-light unit using thereof - Google Patents

Abstract

The present invention provides a backlight unit using an optical sheet on which a micro conical lens array is formed and a light guide plate on which a micro convex lens array is formed, thereby providing advantages of viewing angle and uniformity of a conventional scatterer type backlight unit and high brightness of a direct reflection type backlight unit. It relates to an invention so as to satisfy at the same time.

In the optical sheet according to an aspect of the present invention, a plurality of microconical lenses arranged adjacent to each other on a transparent plate having a predetermined thickness is embossed in a predetermined form.

According to another aspect of the present invention, a backlight unit includes a light source; The light source is disposed on one side, and a plurality of micro-convex lenses arranged adjacent to each other while having a predetermined vertex radius on a transparent plate having a predetermined thickness are embossed in a predetermined shape to image the light beam incident from the light source. A plurality of micro-conical lenses arranged adjacent to each other on the light guide plate and the transparent plate having a predetermined thickness is embossed in a predetermined shape, so that the micro-conical lens on the light guide plate toward the micro convex lens. And an optical sheet disposed to emit light beams incident from the light guide plate to an upper surface thereof.

Description

Optical film with micro conic lens array and back-light unit using equivalent}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical sheet and a backlight unit using the same, and more particularly, to an optical sheet having a microconical lens array and a backlight unit using the optical sheet together with a light guide plate having a microconvex lens array.

The backlight unit refers to a surface light source that effectively transmits light to an active area of a liquid crystal display, which is a non-self emission.

1 is a schematic cross-sectional view of a general structure of a backlight unit. As shown in FIG. 1, a linear light source and a point light source are mainly used as the light source 130 used in the general backlight unit 100, and among these, a cold cathode ray tube fluorescent lamp which is a kind of a discharge lamp is used. Cold Cathode Fluorescent Lamp (CCFL) is mainly used, and a light emitting diode (LED) is mainly used as a point light source.

The light guide plate 120, which is the most important core component of the backlight unit 100, has the light fluxes 120 emitted from the light source 130 incident into the light guide plate 120 when the light guide plate 120 is disposed (pattern insertion surface) or the top surface (beam output surface). After converting into a light flux in the form of a surface light source by using a scattering element or the like inserted in the), it serves to effectively provide the light flux in the form of a surface light source to the entire display area of the liquid crystal display device.

On the other hand, the luminous flux emitted to the upper surface of the light guide plate 120 is determined by Snell's Law. In general, when the refractive index of the medium of the light guide plate 120 is greater than that of air, the light exits from the upper surface of the light guide plate 120. The main angle of the luminous flux has a large exit angle of 80 degrees or more with the normal of the upper surface. This is a result of the critical angle boundary condition according to the ratio of the refractive index of the light guide plate 120 to the refractive index of air.

However, the emission angle required for the liquid crystal display device requires that the main angle of the emission light beam is parallel to the direction of the normal of the upper surface of the light guide plate 120, and the effective viewing angle (full width half maximum-FWHM) should be about 30 degrees. An additional function is required to condense a large angle of light emitted from the upper surface in the normal direction. Therefore, the optical sheets for condensing were used together with the light guide plate 120, and the order and characteristics of the optical sheets for condensing stacked in the backlight unit 100 are light guide plates 120 when the structure of the light guide plate 120 is in the form of scatterers. Diffuser film 150 from the top surface, two Brightness Enhancement Film (BEF) (160, 170), in addition, Moire pattern (Moire Pattern) generated by the lifting phenomenon between the light collecting film Secondary diffusion films (not shown) may be added for removal.

In FIG. 1, reference numeral 110 denotes a reflective sheet disposed under the light guide plate 120 to reflect light emitted from the bottom of the light guide plate 120 and re-enter the light guide plate 120, and 180 denotes an upper brightness enhancing film 170. The protection sheet is disposed on the upper side of the panel to prevent damage to the brightness enhancement film 170, and 140 denotes a reflector reflecting light generated from the light source 130 and outputting the light to the light guide plate 120.

The advantage of the conventional backlight unit having such a structure is that it is possible to secure a sufficient viewing angle as a personal portable display element when using all of the above-mentioned light collecting optical sheets, the disadvantage is that compared to the total amount of light emitted from the light guide plate 50 The relatively low light utilization rate of about% and the cost of the entire optical sheet amount to 30% of the total manufacturing cost of the backlight unit, which is a relatively high financial cost.

In order to compensate for the low light utilization rate and the cost burden of using the light collecting optical sheet, which is a disadvantage of the prior art, a new backlight unit having a 'V' shaped pattern is inserted into the upper or lower surface of the LGP. This technology has the advantage of increasing the center output luminous flux by compensating the conventional low light utilization rate by directly reflecting the luminous flux incident into the LGP and making the emission angle of the luminous flux emitted to the upper surface of the LGP parallel or normal. The conventional light collecting optical sheet for securing is effective in the scattering effect, but inadequate in the direct reflection effect, so it is necessary to manufacture the light collecting plate dedicated light guide plate in which the 'V' shaped pattern is inserted. Since it is parallel to or close to the normal of the upper surface of the light guide plate, there is a disadvantage in that it is inevitable to use a diffusion optical sheet having a large scattering or spreading (HAZE) to secure an effective viewing angle.

As a result, the backlight unit using the light guide plate inserted with the 'V' shaped pattern has no cost benefit compared to the conventional backlight unit technology due to the cost of manufacturing a dedicated optical sheet for condensing, and spreads to secure an effective viewing angle. The use of a large-angle diffusion optical sheet has a problem in that there is also no gain in optical properties compared with the prior art.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has an advantage of viewing angle and uniformity of an existing scatterer-type backlight unit by constructing a backlight unit using an optical sheet on which a micro conical lens array is formed and a light guide plate on which a micro convex lens array is formed. And it aims to be able to simultaneously satisfy the advantages of the high brightness of the direct reflection type backlight unit.

Optical sheet according to an aspect of the present invention for achieving the above object is made of a plurality of micro-conical lenses arranged adjacent to each other on a transparent plate having a predetermined thickness embossed in a predetermined form.

According to another aspect of the present invention, a backlight unit includes a light source; The light source is disposed on one side, and a plurality of micro-convex lenses arranged adjacent to each other while having a predetermined vertex radius on a transparent plate having a predetermined thickness are embossed in a predetermined shape to image the light beam incident from the light source. A plurality of micro-conical lenses arranged adjacent to each other on the light guide plate and the transparent plate having a predetermined thickness is embossed in a predetermined shape, so that the micro-conical lens on the light guide plate toward the micro convex lens. And an optical sheet disposed to emit light beams incident from the light guide plate to an upper surface thereof.

Hereinafter, an optical sheet and a backlight unit using the same according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

2A, 2B, and 2C are plan, cross-sectional, and perspective views, respectively, of a structure according to an embodiment of a light guide plate in the backlight unit of the present invention, and FIGS. 3A and 3B are different implementations of the light guide plate in the backlight unit of the present invention, respectively. A plan view and a cross-sectional view showing a structure according to an example. As shown in FIGS. 2 and 3, the light guide plates 200 and 210 used in the backlight unit according to the exemplary embodiment of the present invention are arranged in a plurality of micro-convex arranged adjacent to each other on a transparent plate having a predetermined thickness. The lens (Micro Convex Lens) may be embossed in a predetermined form, for example, polycarbonate (Polycarbonate), PMMA (Poly Methylmethacrylate) which is a kind of high-purity acrylic resin may be used.

In the above configuration, each micro-convex lens can have a variety of vertex radius, which is less convex than the hemisphere if the vertex radius of r for the exact hemispherical shape is greater than r. If small, it will be more convex than the hemisphere. Micromachining (Micro Machining) and Micro Electro Mechanical System (MEMS) technologies are used to fabricate the micro convex lens arrays 202 and 212.

Meanwhile, as a representative form of the micro convex lens array, a line connecting the center points of four micro convex lenses adjacent to the top, bottom, left and right as shown in FIG. 2A forms a square (hereinafter referred to as a 'four-convex lens array'). As shown in FIG. 2A and FIG. 3A, a parallelogram is formed, that is, a line connecting center points of three adjacent microconvex lenses forms an equilateral triangle (hereinafter referred to as a 'triangle convex lens array'). And the like. The spacing of each micro-convex lens can be appropriately determined according to the structure, material (refractive index), etc. of the optical sheet used together.

4A and 4B are diagrams for describing a filling factor of a light guide plate having a quadrangular convex lens array and a triangular convex lens array, respectively. As shown in Fig. 4A, the area of the unoccupied space in which the microconvex lens is not filled in the square in which the length of one side of the quadrangular convex lens array 202 is twice the diameter (2r) of one microconvex lens is L. When A is the total area of A and A ( ) Are the same as Equations 1 and 2, respectively, and accordingly, ) Is as shown in Equation 3 below. Meanwhile, as shown in FIG. 4B, in the triangular convex lens array 212, the length of one side is twice as large as the diameter 2r of one micro convex lens (L). Area When we say Wow Total area of ( ) Are the same as Equations 4 and 5, respectively, and accordingly, ) Is as shown in Equation 6 below.

As can be seen in the above equations 3 and 6, since the light guide plate 210 having the arrangement of FIG. 3A has a larger filling rate than the light guide plate 200 having the arrangement of FIG. The smaller portion occupies the higher the light output gain.

5A, 5B and 5C are plan, cross-sectional and perspective views showing a structure according to an embodiment of the optical sheet disposed on the light guide plate in the backlight unit of the present invention, respectively, and FIGS. 6A and 6B are the backlight unit of the present invention. A plan view and a cross-sectional view showing a structure according to another embodiment of an optical sheet disposed on the light guide plate in FIG. 5 and 6, the optical sheet according to an embodiment of the present invention has a plurality of micro-conical lens (Micro Conic Lens) arranged adjacent to each other on a transparent plate having a predetermined thickness in a predetermined form It may be embossed, the material may be, for example, PMMA (Poly Methylmethacrylate), which is a kind of high-purity acrylic resin.

In the above-described configuration, the height of each micro-conical lens, the radius of the base and the corner angle, and the distance between each other may be appropriately determined according to the structure or material (refractive index) of the light guide plate used together, and the radius of the base of the light guide plate It is preferable to be equal to or less than the radius of the micro convex lens of. Micro-machining and MEMS techniques are used to fabricate the micro-conical lens arrays 300 and 310.

Meanwhile, as a representative form of the micro-cone lens array, as shown in FIG. 5A, a line connecting the center points of four micro-cone lenses adjacent to the top, bottom, left, and right sides forms a square (hereinafter, referred to as a 'quadron micro cone array'. As shown in (300) or FIG. 6A, a parallelogram is formed, that is, a line connecting the center points of three adjacent microconical lenses forms an equilateral triangle (hereinafter referred to as a `` triangular microconical lens array '') ( 310) and the like.

7 is a cross-sectional view schematically showing the overall structure of a backlight unit according to an embodiment of the present invention, an optical sheet having a light guide plate 200 having a quadrangular convex lens array 202 and a quadrangular conical lens array 302. The example which employ | adopted and comprised 300 is shown. As shown in FIG. 7, the overall structure of the backlight unit according to the embodiment of the present invention includes a point light source such as an LED or a CCFL on one side of the light guide plate 200 on which the micro convex lens array 202 is formed. The light source 130 implemented by the same linear light source is disposed, and the optical sheet 300 on which the microconical lens array 302 is formed is disposed on the light guide plate 200. In this case, the microconical lens array 302 is disposed. ) Is inverted to interview the micro convex lens array 202 of the light guide plate 200. A reflecting sheet 110 is disposed below the light guide plate 200 to reflect the light beam emitted from the bottom surface of the light guide plate 200 and re-inject into the light guide plate 200. In the drawing, reference numeral 140 denotes a reflector reflecting the light beam generated by the light source 130 and incident on the side surface of the light guide plate 200, and 180 denotes a protective sheet for protecting the optical sheet 300. As described above, the present invention has excellent brightness and uniformity than the performance of the conventional backlight unit even without using a diffusion film or brightness enhancement film as in the prior art.

Although not shown, a light scattering pattern may be formed on the bottom of the light guide plate 200 so that the light beam may be uniformly radiated over the entire area of the light guide plate 200. The light scattering pattern may be scattered. Hemispherical relief having rough surface and a predetermined diameter of about 80-120 [㎛], that is, a pattern protruding outward from the bottom of the light guide plate 200 or a 'V' shaped relief or intaglio pattern which is a kind of a direct reflection structure. This can be In addition, it is preferable that a fine pattern is formed on the side surface of the light guide plate 200, which is in contact with the light source 130, that is, the light incident surface, and the fine pattern may be implemented as, for example, a serrated pattern. The light is focused or dispersed according to the cabinet's internal angle and arrangement period.

8A and 8B are diagrams for explaining the alignment between the light guide plate and the optical sheet in the backlight unit of the present invention, respectively, in which the corners of the individual micro-convex and micro-conical lenses have the same radius, so The example shows that the convex lens is aligned in the center of the empty space. As shown in Figs. 8A and 8B, when the light guide plate having the four-convex lens array 202 is adopted, it is preferable to use an optical sheet having the four-conical lens array 302, and the three-convex lens array In the case where the light guide plate having 212 is adopted, it is preferable to use an optical sheet having a triangular conical lens array 312.

9A and 9B are views for explaining the position shifting allowance range of the optical sheet in the alignment state shown in FIGS. 8A and 8B, respectively. In FIGS. 9A and 9B, when the vertical axis is referred to as the Y axis and the horizontal axis is referred to as the X axis, the allowable range of position shift of the optical sheet with respect to the light guide plate having the quadrangular convex lens array 202 is respectively defined around the center of the vacant seat. Axially This can be The position shifting range of the optical sheet with respect to the light guide plate having the triangular convex lens array 212 is in the Y-axis direction with respect to the center of the vacant seat as shown in FIG. 9B. In the X-axis direction Can be

FIG. 10 is a view illustrating a light exit pattern of a light guide plate and an optical sheet in a backlight unit according to an exemplary embodiment of the present invention; a light guide plate and a quadrangular conical lens array having a four-convex convex lens array 202; An example in which an optical sheet having 302 is adopted is shown. As shown in FIG. 10, in the light guide plate 200 of the present invention, the angle of incidence of the light beams incident on the light guide plate upper surface in the light guide plate medium and the normal line of the micro convex lens is a plane in which the micro convex lens is not formed. Since the angle of incidence is smaller than that in the case, the circumferential angle of the emitted light beam becomes small as ± 30 to 35 degrees. This results in the same light emission characteristics and effective viewing angle range of the backlight unit to which the prior art is applied, thus leading to the conclusion that the conventional optical sheet does not need to be used. However, the emission form has a disadvantage that the central output light amount is low due to a circular band having a circumference of ± 30 to 35 degrees, and due to the characteristics of the micro-cone lens array 302 of the optical sheet used together, When the shape converges in a circular band, and the incident direction is incident from the vertex of the cone of the cone toward the bottom, the shape of the outgoing light transmitted through the bottom of the cone lens is a circular plane. Therefore, by using the characteristics of the conical lens, the circular beam-shaped exiting light beam emitted from the upper surface of the light guide plate passes through the micro-cone lens array 302 to form a final light beam incident on the liquid crystal display device. It is possible to increase the center emission light amount by making a plane and to obtain a gain having an effective viewing angle at the same time.

As such, the exit angle of the luminous flux from the optical sheet is preferably parallel to the normal to the upper surface of the optical sheet, that is, the angle of the normal to 0 degrees. In this case, the refractive angle at the conical surface of the microconical lens of the luminous flux ( ) May be determined as in Equation 7 below.

From here, and Are the refractive indices of the air and micro-conical lenses, respectively. Denotes the angle of incidence of the light beam with respect to the normal of the microconical cone surface, Denotes the increment of the microcone vertex angle. As can be seen from Equation (7), by adjusting the type of refractive index of the optical sheet and the angle of incidence of the micro-cone lens and the angle of incidence through the conical surface of the micro-cone lens, the output angle of the light beam from the optical sheet is adjusted. It can be kept parallel to the normal to the top surface. Furthermore, the angle of incidence through the conical surface of the micro ) Also depends on the type (refractive index) of the medium of the microconvex lens and its vertex radius. Furthermore, the area where the center exit angle is 0 degrees depends on the distance between the light guide plate and the optical sheet.

The optical sheet of the present invention and the backlight unit using the same are not limited to the above-described embodiments and may be modified in various ways within the scope of the technical idea of the present invention.

As described above, according to the backlight unit of the present invention, while using one light guide plate and one optical sheet, advantages of the viewing angle and uniformity of the existing scatterer pattern type backlight unit and advantages of high brightness of the direct reflection type backlight unit Can be satisfied at the same time, the overall thickness of the backlight unit can be reduced, and the manufacturing cost thereof can be reduced.

1 is a cross-sectional view schematically showing the overall structure of a general backlight unit;

2A, 2B and 2C are a plan view, a cross-sectional view and a perspective view respectively showing a structure according to an embodiment of a light guide plate in the backlight unit of the present invention;

3A and 3B are a plan view and a sectional view showing a structure according to another embodiment of a light guide plate in the backlight unit of the present invention, respectively;

4A and 4B are diagrams for explaining the filling rate of the light guide plate shown in FIGS. 2A and 3A, respectively;

5A, 5B, and 5C are plan views, cross-sectional views, and perspective views illustrating a structure according to an embodiment of an optical sheet disposed on an upper light guide plate of the backlight unit of the present invention;

6A and 6B are a plan view and a cross-sectional view showing a structure according to another embodiment of an optical sheet disposed on the light guide plate in the backlight unit of the present invention;

7 is a cross-sectional view schematically showing the overall structure of a backlight unit according to an embodiment of the present invention;

8A and 8B are views for explaining an alignment state between the light guide plate and the optical sheet in the backlight unit of the present invention, respectively;

9A and 9B are views for explaining the position shift allowance range of the optical sheet in the alignment state shown in Figs. 8A and 8B, respectively;

10 is a view for explaining a light emission pattern of the light guide plate and the optical sheet in the backlight unit according to an embodiment of the present invention.

*** Explanation of symbols for the main parts of the drawing ***

100: backlight unit, 110: reflective sheet,

120: light guide plate, 130: light source,

140: reflector, 150: diffusion film,

160: lower brightness film, 170: upper brightness film,

180: protective sheet, 200, 210: light guide plate,

202, 212: micro convex lens array, 300, 310: optical sheet,

302, 312: micro-conical lens array

Claims (8)

delete delete delete Light source; The light source is disposed on one side, and a plurality of micro-convex lenses arranged adjacent to each other while having a predetermined vertex radius on a transparent plate having a predetermined thickness are embossed in a predetermined shape to image the light beam incident from the light source. Light guide plate and A plurality of micro-conical lenses arranged adjacent to each other on a transparent plate having a predetermined thickness is embossed in a predetermined form, the micro-conical lens is disposed on the light guide plate to face the micro convex lens from the light guide plate A backlight unit comprising an optical sheet for emitting the incident light beam to the upper surface. The method of claim 4, wherein And a radius of the bottom side of the micro conical lens is equal to or less than a radius of the bottom side of the micro convex lens. The method of claim 5, wherein the micro-convex lenses are arranged such that a line connecting the center points of the four micro-convex lenses adjacent to the top, bottom, left and right forms a square, And the micro-conical lens is arranged such that a line connecting the center points of the four micro-cone lenses adjacent to each other in the top, bottom, left and right forms a square. The method of claim 5, wherein the micro-convex lenses are arranged such that a line connecting the center points of the four micro-convex lenses adjacent to the top, bottom, left and right forms a parallel rectangle, And the micro-conical lens is arranged such that a line connecting center points of the four micro-cone lenses adjacent to each other vertically, horizontally, and quadrangularly forms a parallelogram. The method according to any one of claims 4 to 7, And a predetermined pattern is formed on a bottom surface of the light guide plate and a light incident surface facing the light source.