KR102009798B1 - Backlight unit - Google Patents

Abstract

The present invention relates to a backlight unit capable of reducing cost and slimming down.
A backlight unit according to the present invention includes a printed circuit board; A light emitting package formed on the printed circuit board; A light diffusion lens formed on the printed circuit board and having an inner curved surface positioned on an upper end of the light emitting package and an outer curved surface diffusing light incident through the inner curved surface; And a reflection plate formed on the printed circuit board on which the light emitting package and the light diffusing lens are formed, each reflecting plate having an opening for exposing each of the light diffusing lenses, wherein each of the inner curved surface and the outer curved surface of the light diffusing lens has no inflection point. It is characterized by.

Description

Backlight Unit {BACKLIGHT UNIT}

The present invention relates to a backlight unit, and more particularly to a backlight unit that can reduce the cost and slim.

In general, the liquid crystal display (Liquid Crystal Display) is a flat panel display device that displays an image using a liquid crystal, it is thinner and lighter than other display devices, and has the advantages of low driving voltage and low power consumption, It is widely used throughout.

Such a liquid crystal display device requires a backlight unit for supplying light because the liquid crystal display panel for displaying an image is a non-light emitting device that does not emit light by itself. The light emitting packages used as the light source of the backlight unit have a limited emission range, and thus, uniform luminance cannot be obtained over a large area. Therefore, since a large number of light sources are used to obtain luminance uniformity, the cost increases. In addition, in order to obtain luminance uniformity, increasing the distance between the printed circuit board on which the light source is mounted and the diffusion plate increases the overall thickness of the backlight unit, making it difficult to slim down.

In order to solve the above problems, the present invention is to provide a backlight unit that can reduce the cost and slim.

A backlight unit according to the present invention for achieving the above object is a printed circuit board; A light emitting package formed on the printed circuit board; A light diffusion lens formed on the printed circuit board and having an inner curved surface positioned on an upper end of the light emitting package and an outer curved surface diffusing light incident through the inner curved surface; And a reflection plate formed on the printed circuit board on which the light emitting package and the light diffusing lens are formed, each reflecting plate having an opening for exposing each of the light diffusing lenses, wherein each of the inner curved surface and the outer curved surface of the light diffusing lens has no inflection point. It is characterized by.

Here, each of the inner curved surface and the outer curved surface is formed in a shape that satisfies the following equation (1) and (2).

[Equation 1]

In Equation 1, z is a vertical distance from the vertices of the inner surface and the outer surface to the light emitting package located in the negative direction relative to the vertex, and r is the inner surface and the outer surface from the vertices of the inner surface and the outer surface, respectively The horizontal distance to each outermost part, c is the curvature of each of the inner and outer surfaces, k is the cone constant, and each of a1, a2, a3, ..., an is the 1st, 2nd, 3rd order The order of aspherical surface coefficients is shown.

[Equation 2]

dz / dr <0

In Equation 2, dz is the amount of change in the vertical distance from the vertices of the inner surface and the outer surface to the light emitting package located in the negative direction with respect to the vertex, and dr is the inner surface and The amount of change in the horizontal distance to the outermost part of each of the outer curved surfaces is shown.

Specifically, the coefficient range of the inner curved surface is -10 <c <-0.1, -2 <k <0, 0 <a2 <1.5, 0 <a3 <0.006, 0 <a4 <0.002, and the coefficient range of the outer curved surface Is -0.154 <c <0, -10 <k <0,0 <a2 <0.03, 0 <a3 <0.0006, -0.0006 <a4 <0, -0.000008 <a6 <0.

The light diffusing lens may be formed in the form of a meniscus lens in which the inner curved surface has a negative power and the outer curved surface has a positive power.

On the other hand, the support unit of the backlight unit according to the present invention is formed between the light diffusing lens and the printed circuit board, characterized in that to provide a storage space having a surface area larger than the surface area of the light emitting package.

In addition, the stepped portion of the backlight unit according to the present invention is characterized by forming a step of several tens of micrometers with the bottom surface between the inner curved surface and the bottom surface of the light diffusion lens.

In addition, the backlight unit according to the present invention may further include a scattering pattern formed at a height of several μm on at least one of the inner curved surface, the outer curved surface, the bottom surface, and the stepped portion of the light diffusing lens.

In order to achieve the above technical problem, the backlight unit according to the present invention includes a printed circuit board; A light emitting package formed on the printed circuit board and having at least two light emitting diodes; A light diffusion lens formed on the printed circuit board and having an inner curved surface positioned on an upper end of the light emitting package and an outer curved surface diffusing light incident through the inner curved surface; And a reflector formed on the printed circuit board on which the light emitting package and the light diffusing lens are formed, the reflecting plate having an opening for exposing each of the light diffusing lenses, wherein each of the inner curved surface and the outer curved surface of the light diffusing lens has no inflection point. The horizontal cross section of the inner curved surface of the light diffusing lens is oval.

Here, the inner curved surface is formed in a shape that satisfies the following equation (3).

[Equation 3]

In Equation 3, x is the major axis radius of the inner surface of the elliptical horizontal cross section, y is the minor axis radius of the inner surface, c _x is the curvature of the inner surface in the x direction, c _y is the curvature of the inner surface in the y direction k _x represents a conic constant in the x direction, and k _y represents a conical constant in the y direction.

The ratio between the long axis radius and the short axis radius is 0.2 to 2 times the ratio between the long side and the short side of the light emitting package.

In order to achieve the above technical problem, the backlight unit according to the present invention includes a printed circuit board; A light emitting package formed on the printed circuit board and having at least two light emitting chips; A light diffusion lens formed on the printed circuit board and having an inner curved surface positioned on an upper end of the light emitting package and an outer curved surface diffusing light incident through the inner curved surface; And a reflecting plate formed on the printed circuit board on which the light emitting package and the light diffusing lens are formed, the reflecting plate having an opening for exposing each of the light diffusing lenses, wherein the inner curved surface of the light diffusing lens is larger than the number of the light emitting chips. And a vertex and an inflection point equal to or greater than the number of light emitting chips.

Here, the inner curved surface is formed in a shape that satisfies the following equation (4).

[Equation 4]

In Equation 4, z is a vertical distance from the lowest peak of the inner curved surface to the light emitting package relative to the lowest peak, r is a horizontal distance from the central axis of the light diffusion lens to the inner curved surface, A, B, Each of C, D, ... represents secondary, quaternary, sixth, eighth, ... aspherical coefficients.

Here, when the light emitting chip is two, the inner curved surface of the light diffusion lens has three vertices and two inflection points.

According to the present invention, since the inner curved surface and the outer curved surface of the light diffusing lens are formed so as not to have an inflection point, color dispersion can be prevented and processing can be easily performed to reduce manufacturing cost. In addition, in the present invention, since the distribution of light passing through the light diffusing lens is circular, energy can be prevented from being concentrated at the same position as the light emitting chip, thereby obtaining a uniform image. In addition, in the present invention, the light generated from the light emitting package is diffused through the light diffusing lens to make the backlight unit slim, and the number of light emitting packages can be reduced, thereby reducing the cost. In addition, the present invention reduces manufacturing costs and simplifies the process due to the elimination of circular reflectors.

1 is a perspective view illustrating a light diffusing lens according to a first embodiment of the present invention.
FIG. 2 is a cross-sectional view illustrating the light diffusing lens illustrated in FIG. 1.
3 is a cross-sectional view showing a conventional light diffusing lens compared with the present invention.
4 is a cross-sectional view showing another embodiment of the support shown in FIG.
5 is a cross-sectional view illustrating a light diffusing lens according to a second exemplary embodiment of the present invention.
FIG. 6 is a cross-sectional view of a mold for manufacturing the light diffusing lens shown in FIG. 5.
FIG. 7 is a diagram for describing occurrence of a bad pattern when the lower core illustrated in FIG. 6 is formed in a curved surface.
8 is a cross-sectional view illustrating a light diffusing lens according to a third exemplary embodiment of the present invention.
9A and 9B are diagrams for describing bright spot removal with or without a scattering pattern illustrated in FIG. 5.
10 is a perspective view illustrating a light diffusing lens according to a fourth embodiment of the present invention.
FIG. 11 is a cross-sectional view illustrating the light diffusing lens illustrated in FIG. 10.
FIG. 12 is a diagram for describing a relationship between a light diffusing lens and a light emitting package illustrated in FIG. 10.
FIG. 13 is a diagram for describing a process of changing light distribution through the light diffusion lens illustrated in FIG. 10.
14 is a perspective view illustrating a light diffusing lens according to a fifth embodiment of the present invention.
FIG. 15 is a cross-sectional view illustrating the light diffusing lens illustrated in FIG. 14.
FIG. 16 is a diagram for describing the light diffusing lens illustrated in FIG. 14 in detail.
FIG. 17 is a diagram for describing an optical path through the light diffusion lens illustrated in FIG. 10.
18 is a cross-sectional view illustrating a liquid crystal display module having a light diffusing lens according to any one of first to fifth embodiments of the present invention.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

1 is a perspective view illustrating a light diffusing lens of a backlight unit according to a first embodiment of the present invention, and FIG. 2 is a cross-sectional view illustrating the light diffusing lens illustrated in FIG. 1.

The light diffusing lens 120 illustrated in FIGS. 1 and 2 is formed to correspond one-to-one with the light emitting package 112 formed on the printed circuit board 114. In this case, the line width of the printed circuit board 114 on which the light emitting package 112 is formed may be smaller than the width and length of the light diffusion lens 120, thereby reducing the cost. The light emitting package 112 and the light diffusing lens 120 formed on the printed circuit board 114 to have a one-to-one correspondence are exposed to the outside by the opening 162 of the reflecting plate 160.

The light diffusing lens 120 is formed to have an inner curved surface 122 and an outer curved surface 124 each having a symmetrical structure with respect to the central axis.

The inner curved surface 122 is formed to be concave to have a curved surface from the rear surface of the light diffusing lens 120 to be adjacent to the outer surface of each of the plurality of light emitting packages 112. In particular, the steeper the inclination of the inner curved surface 122, the more light is spread, and thus the density of light emitted through the central region of the light diffusion lens 120 may be reduced. Accordingly, the diameter of the bottom surface of the light diffusing lens 120 is equal to or larger than the light emitting surface of the light emitting package 112 so that the inner curved surface 122 has a conic shape.

The outer curved surface 124 is formed in the aspherical surface on the upper surface of the light diffusion lens 120. The outer curved surface 124 serves to diffuse light incident through the inner curved surface 122.

Each of the inner curved surface 122 and the outer curved surface 124 may have a shape satisfying Equation 1, and a higher order term may be added.

In Equation 1, z is vertical from the vertices PP1 and PP2 of each of the inner surface 122 and the outer surface 124 to the light emitting package 112 positioned in the negative direction with respect to the vertices PP1 and PP2. R is a horizontal distance from the vertices PP1 and PP2 of each of the inner surface 122 and the outer surface 124 to the outermost portion of each of the inner surface 122 and the outer surface 124, and c is the inner The curvature of each of the surface 122 and the outer surface 124, k is the conic constant, and a1, a2, a3, ..., an each is primary, secondary, tertiary, ..n The difference aspherical surface coefficient is shown.

For example, the outer curved surface 124 and the inner curved surface 122 are formed to have the values shown in Table 1.

c k a1 a2 a3 a4 a5 a6 Exterior surface -0.154 <c <0 -10 <k <0 0 0 <a2 <0.03 0 <a3 <0.0006 -0.0006 <a4 <0 0 -0000008 <a6 <0 Inside surface -10 <c <-0.1 -2 <k <0 0 0 <a2 <1.5 0 <a3 <0.006 0 <a4 <0.002

In addition, each of the inner curved surface 122 and the outer curved surface 124 of the light diffusing lens 120 has dz / dr <0 (where dz is a vertex PP1 and PP2 of each of the inner curved surface 122 and the outer curved surface 124). ) Is the amount of change in the vertical distance from the light emitting package 112, dr is the vertex (PP1, PP2) of each of the inner surface (122) and outer surface (124) from the inner surface (122) and outer surface (124) Since there is no inflection point, the shape is simpler than that of the conventional light diffusing lens, thereby reducing processing time and manufacturing cost.

In addition, the light diffusing lens 120 is formed in the form of a meniscus lens forming a hollow portion 126 surrounding the exit surface of the light emitting package 112.

In this case, the inner curved surface 122 of the light diffusion lens 120 of the meniscus lens type has a negative power according to Equation 2, and the outer curved surface 124 has a positive power according to Equation 3 Is formed.

In Equation 2, R1 is the curvature of the inner surface 122, n1 is the refractive index of the hollow portion 126 surrounding the exit surface of the light emitting package 112, n2 represents the refractive index of the light diffusing lens 120. . In this case, since the refractive index n1 of the hollow part 126, that is, the internal air is 1, and the refractive index n2 of the light diffusing lens 120 formed of the plastic resin is 1.5, the hollow part 126 is hollow at the refractive index of the light diffusing lens 120. The subtracted refractive index of the portion 126 has a positive value, and the curvature of the inner curved surface 122 is formed to be concave toward the light emitting package 112 and thus has a negative curvature. Therefore, the inner curved surface 122 of the light diffusing lens 120 has a negative power.

In Equation 3, R2 is the curvature of the outer curved surface 124, n3 is the refractive index of the outside air surrounding the outer curved surface of the light diffusing lens 120, n2 represents the refractive index of the light diffusing lens 120. In this case, since the refractive index n3 of the external air is 1 and the refractive index n2 of the light diffusing lens 120 formed of plastic is 1.5, a value obtained by subtracting the refractive index of the light diffusing lens 120 from the refractive index of the external air is It has a negative value and has a negative curvature because the curvature of the outer curved surface 124 is formed concave toward the light emitting package 112. Thus, the outer curved surface 124 of the light diffusing lens 120 has a positive power.

As such, the light diffusing lens 120 of the present invention has an inner curved surface 122 having a negative power and an outer curved surface 124 having a positive power in the front, such as a doublet of a camera lens system. Color dispersion can be alleviated.

On the other hand, the conventional light diffusing lens 20 shown in FIG. 3 is formed on the printed circuit board 14 with the circular reflector 16 interposed therebetween. The circular reflector 16 is formed on the printed circuit board 14 so as to correspond one-to-one with each light diffusing lens 12, and a reflecting plate (not shown) is formed on the printed circuit board 14 except for the circular reflector 16. do. The conventional light diffusing lens 20 is formed of an inner curved surface 22 having no inflection point and an outer curved surface 24 having an inflection point. Here, the vertex regions P1 and P2 of the outer curved surface 24 formed concave toward the light emitting package 12 have negative curvature, and the vertex regions of the outer curved surface 24 formed convex toward the light emitting package 12. P3 has a positive curvature. Thus, the outer curved surface 24 of the conventional light diffusing lens 20 has both negative power and positive power. In this case, among the white light emitted from the light emitting package 12 in which the blue light and the yellow light are mixed to generate the white light, yellow light having a long wavelength is refracted toward the outer side of the outer curved surface 24 having a positive power and is emitted. The blue light is refracted toward the center of the outer curved surface 24 having negative power and emitted. Accordingly, the backlight unit having the conventional light diffusing lens 20 has a problem in that color dispersion in which yellow light is dispersed in a ring shape is generated in a region corresponding to each of the light diffusing lenses 20.

In addition, in the conventional light diffusing lens 20, as described above, the central portion of the outer curved surface 24 has negative power. In this case, the light emitted from the light emitting package 12 tends to cause total reflection at the center of the light diffusing lens 20 having negative power, thereby causing a dark spot at the center of the light diffusing lens 20.

On the other hand, since the outer curved surface 124 of the light diffusing lens 120 according to the present invention has a positive power as described above, total reflection is not likely to occur, thereby preventing dark spots generated at the center of the light diffusing lens 120. can do.

In addition, the light diffusing lens 120 according to the present invention can reduce the amount of light totally reflected from the outer curved surface 124 compared to the light diffusing lens 20 shown in FIG. 3 to reduce the light diffusing lens 120 according to the present invention. The amount of light incident on the liquid crystal panel 140 is similar to the amount of light incident on the liquid crystal panel through the conventional light diffusing lens 20 shown in FIG. 3 without a circular reflector. Accordingly, the present invention simplifies the process due to the material cost reduction and removal of the attachment process of the circular reflector since the conventional circular reflector is unnecessary.

On the other hand, the light diffusing lens according to the present invention has a support 128 as shown in FIG. The support part 128 is formed to allow the light diffusing lens 120 to be positioned on the light emitting package 112, and to provide an accommodation space 116 to accommodate the light emitting package 112. The storage space 116 has an area larger than the upper area of the light emitting package 112. The support 128 has a bottom surface of the light diffusing lens 120 and the printed circuit board 114 such that the storage space 116 is formed adjacent to the hollow portion 126 in the inner curved surface 122 of the light diffusing lens 120. Formed between). In this case, the line width of the support 128 is narrower than the bottom surface of the light diffusion lens 120 or is similarly formed as shown in FIG. 4. The support 128 is inserted into a fixing groove (not shown) formed in the printed circuit board 114 and then fixed to the printed circuit board 114 through a photocuring method or a thermosetting method. On the other hand, the support 128 may be formed integrally with the same material as the light diffusing lens 120 or may be formed separately from the same material or different materials.

As described above, the light diffusing lens according to the present invention is formed such that each of the inner curved surface and the outer curved surface does not have an inflection point, thereby preventing color dispersion and easily processing, thereby reducing manufacturing cost. In addition, the light diffusing lens according to the present invention diffuses the light generated in the light emitting package, so that the backlight unit can be made slim and the number of light emitting packages can be reduced, thereby reducing the cost. In addition, the present invention reduces manufacturing costs and simplifies the process due to the elimination of circular reflectors.

5 is a cross-sectional view illustrating a light diffusing lens of a backlight unit according to a second exemplary embodiment of the present invention.

The light diffusing lens illustrated in FIG. 5 has the same components except for providing a stepped portion as compared to the backlight unit illustrated in FIG. 2. Accordingly, detailed description of the same components will be omitted.

The stepped portion 164 illustrated in FIG. 5 is formed between the inner curved surface and the bottom surface of the light diffusion lens 120 to form a step h of several tens of micrometers. As a result, the accuracy of processing in manufacturing the light diffusing lens 120 is increased and injection is easy.

Specifically, to manufacture the light diffusing lens illustrated in FIG. 5, the base 180 includes upper and lower bases 180a and 180b and upper and lower cores 182 and 184 as illustrated in FIG. 6. .

The upper core 182 positioned inside the upper base 180a provides a frame for forming an outer curved surface of the light diffusing lens 120. The upper core 182 is formed to be in contact with the lower base 180b to easily control the tolerance of the height.

The lower core 184 positioned inside the lower base 180b is formed to face the upper core 182 to provide a cavity 186 having the same shape as the light diffusing lens. The lower core 184 includes a curved first lower core 184a and a second lower core 184b having a wider width than the first lower core 184a. The first lower core 184a is formed to have a surface forming an inner curved surface of the light diffusing lens 120, and the second lower core 184b is formed to correspond to the stepped portion 164 of the light diffusing lens 120. Is formed. In particular, the second lower core 184b is formed as a flat surface whose side contacting the lower base 180b is not a curved surface. Accordingly, it is possible to prevent the formation of an empty space between the second lower core 184b and the lower base 180b, thereby increasing the accuracy of processing and accurately controlling the vertical movement. On the other hand, when the side surface of the lower core 184 in contact with the lower base 180b is formed as a curved surface, as shown in FIG. 7, an empty space A is formed between the lower base 180b and the lower core 184. Is generated. When the plastic resin is injected into the cavity 186, the plastic resin is also injected into the empty space A connected to the cavity 186. Accordingly, there is a problem that a bad pattern is formed on the bottom surface of the light diffusing lens 120, thereby reducing the accuracy of processing.

As described above, the present invention prevents formation of an empty space between the second lower core 184b and the lower base 180b by forming the flat side surface of the second lower core 184b in contact with the lower base 180b. This increases the accuracy of machining and can be accurately controlled when moving up and down.

8 is a cross-sectional view illustrating a light diffusing lens of a backlight unit according to a third exemplary embodiment of the present invention.

The backlight unit illustrated in FIG. 8 has the same components except that the backlight unit illustrated in FIG. 2 further includes a scattering pattern. Accordingly, detailed description of the same components will be omitted.

The scattering pattern 118 illustrated in FIG. 8 is formed on at least one of the inner curved surface 122 and the bottom surface of the light diffusing lens 120. This scattering pattern 118 is formed to have a height of several μm. The light diffusing lens 120 having the scattering pattern 118 is formed through an injection process using a lower core having a surface formed in an irregular shape through a sand blast process or an etching process.

The scattering pattern 118 formed on the bottom surface of the light diffusing lens 120 may remove spots having a spot shape at the center of the light diffusing lens 120 using scattering characteristics.

Specifically, when there is no scattering pattern 118 on the bottom surface of the light diffusing lens 120, as shown in FIG. 9A, some of the light La1 emitted from the light emitting package 112 is the outer curved surface 124. The light is emitted through the remaining light La2 and is reflected toward the printed circuit board 114 by Fresnel reflection. The light La2 reflected toward the printed circuit board 114 is reflected back and emitted through the outer curved surface 124. At this time, since the light La2 that is re-reflected and emitted is close to the central axis of the light diffusion lens 120, a bright point phenomenon in which the center of the light diffusion lens 120 is bright is generated.

On the other hand, when the scattering pattern 118 is located on the bottom surface of the light diffusing lens 120, as shown in FIG. 9B, some of the light Lb1 emitted from the light emitting package 112 is the outer curved surface 124. Is emitted through the remaining light Lb2 is reflected toward the printed circuit board 114 by Fresnel reflection. The light Lb2 reflected toward the printed circuit board 114 is diffused by the scattering pattern 118 and is emitted in a direction away from the central axis of the light diffusion lens 120. Accordingly, the present invention can prevent the bright spot phenomenon in which the center of the light diffusing lens 120 is bright through the scattering pattern 118 formed on the bottom surface of the light diffusing lens 120.

When the scattering pattern 118 formed on the inner curved surface 122 of the light diffusing lens 120 scatters light toward the center of the light diffusing lens 120 using scattering characteristics, there is no circular reflector on the printed circuit board 114. It is possible to prevent the central dark portion that occurs. On the other hand, the scattering pattern 118 may be formed on the outer curved surface 124 and the stepped portion 164 shown in FIG. 5 as well as the inner curved surface 122 to prevent the central arm portion.

10 is a perspective view illustrating a light diffusing lens of a backlight unit according to a fourth exemplary embodiment of the present invention, and FIG. 11 is a cross-sectional view illustrating the light diffusing lens illustrated in FIG. 10.

The light diffusing lens 220 illustrated in FIGS. 10 and 11 is formed in a symmetrical structure with respect to the central axis, and has an inner curved surface 222 and an outer curved surface 224.

The outer curved surface 224 serves to diffuse light incident through the inner curved surface 222.

The inner curved surface 222 has a smaller diameter than the outer curved surface 224, so that the design accuracy is high due to the high pattern accuracy during injection molding. The inner curved surface 222 and the outer curved surface 224 are formed to surround the light emitting package 112 having a rectangular shape having at least two light emitting chips 112a and 112b, and are concave toward the light emitting package 112.

The inner curved surface 222 is formed such that the horizontal cross section satisfies Equation 4 in an elliptical shape, and a higher order term may be added as shown in Equation 5.

In Equations 4 and 5, x is the major axis radius of the inner surface 222 having an elliptical horizontal cross section as shown in FIG. 12, y is the minor axis radius of the inner surface 222, and c _x is the inner surface of the x direction. Is the curvature of (222), c _y is the curvature of the inner surface 222 in the y direction, k _x is the conic constant ( _x) in the x direction, k _y represents the cone constant in the y direction, Where Ax is the fourth-order aspherical coefficient in the x direction, Ay is the fourth-order aspherical coefficient in the y direction, Bx is the sixth-order aspherical coefficient in the x direction, By is the sixth-order aspherical coefficient in the y direction, and Cx is the x-direction in the x direction. An eighth order aspherical coefficient, Cy represents an eighth order aspherical coefficient in the y direction.

The long side LL of the light emitting package 112 surrounded by the inner curved surface 222 is parallel to the long axis radius x of the inner curved surface 222, and the short side LL of the light emitting package 112 is the inner curved surface 222. Parallel to the short axis radius (y). In this case, the ratio of the long axis radius LL and the short axis radius SL of the inner curved surface 222 is 0.2 to 2 times the ratio of the length of the long side x and the short side y of the light emitting package 112.

The light distribution concentrated on each of the light emitting chips 112a and 112b in the light emitting package 112 is diffused by the light diffusion lens 220 to form a circle.

Specifically, as shown in FIG. 13, the light distributions LD1 and LD2 emitted from each of the two light emitting chips 112a and 112b form a circle. The light distributions LD1 and LD2 have a difference in an up / down, left / right stretching ratio through the light diffusion lens 220 having an inner curved surface 222 having an elliptical shape in a horizontal cross section. Therefore, the energy of the light emitted from each of the two light emitting chips 112a and 112b and passing through the light diffusion lens 220 overlaps the light distribution LD1 and LD2 to form a circular shape, thereby obtaining a uniform image.

Meanwhile, the line width of the support part 228 of the light diffusing lens 220 of the backlight unit according to the fourth embodiment of the present invention is narrower than the bottom surface of the light diffusing lens 220 or as shown in FIG. 4. It may be formed similarly to the bottom surface of the 220, a stepped portion 164 shown in FIG. 5 may be formed between the inner curved surface 222 and the bottom surface of the light diffusing lens 220, and the light diffusing lens ( A scattering pattern 118 illustrated in FIG. 8 may be formed on at least one of the inner curved surface 222 and the bottom surface of the 220.

14 is a perspective view illustrating a light diffusing lens of a backlight unit according to a fifth exemplary embodiment of the present invention, and FIG. 15 is a cross-sectional view illustrating the light diffusing lens illustrated in FIG. 14.

The light diffusing lens 320 illustrated in FIGS. 14 and 15 is formed in a symmetrical structure with respect to the central axis and is formed to have an inner curved surface 322 and an outer curved surface 324.

The inner curved surface 322 has a smaller diameter than the outer curved surface 324 and thus has high pattern accuracy in injection molding, so that the design is easy. The inner curved surface 322 is formed to surround the rectangular light emitting package 112 having at least two light emitting chips 112a and 112b.

The inner curved surface 322 has more vertices (dz / dr = 0) than the number of light emitting chips 112a and 112b positioned in the light emitting package 112, and the light emitting chips 112a and positioned in the light emitting package 112. 112b) is formed into an equation shape of even-order terms that satisfy equation (6) having an inflection point (d ² z / dr ² = 0) or more.

In Equation 6, z is a vertical distance from the lowest vertex of the inner surface 322 to the light emitting package 112 based on the lowest vertex, as shown in Figure 15, r is from the central axis of the inner surface to the inner surface Are the horizontal distances of A, B, C, D, ..., and each represents the 2nd, 4th, 6th, 8th, ... aspherical coefficients.

For example, and the three two light emitting chips (112a, 112b) for having the light emitting package 112 is dz / dr = 0 is the vertex (PP11, PP12, PP13), as shown in Fig. 16, d ² z The inflection points PL1 and PL2 with / dr ² = 0 are formed in the form of an equation with even-numbered terms.

The inner curved surface 322 collects the light distribution concentrated on each of the light emitting chips 112a and 112b in the light emitting package 112 to the center.

The outer curved surface 324 is formed concave toward the light emitting package 112 to diffuse the light gathered in the center through the inner curved surface 322.

Specifically, as shown in FIG. 17, when the light diffusing lens 320 is applied to the light emitting package 112 having the two light emitting chips 112a and 112b, the light emitting lenses 112 emit light from each of the two light emitting chips 112a and 112b. The light is incident on the light diffusing lens 320. Light incident on the inner curved surface 322 of the light diffusing lens 320 is refracted and emitted in a direction NL perpendicular to the inner curved surface 322. That is, the refractive index of the hollow portion 326, that is, air, surrounding the light emitting package 112 is 1, and the refractive index of the light diffusion lens 320 formed of the plastic resin is about 1.1 to 1.9 which is higher than the air. Accordingly, the light emitted from the light emitting chips 112a and 112b proceeds from the hollow portion 326 having a low refractive index to the light diffusing lens 320 having a high refractive index, and according to Snell's law, an emission angle smaller than the incident angle θ1 is obtained. ([theta] 2). Therefore, the light emitted from each of the two light emitting chips 112a and 112b and incident on the light diffusing lens 320 is collected by the inner curved surface 322 to the center of the light diffusing lens 320 and the light diffusing lens 320. Diffused by the outer curved surface 324) and exits to the outside. As a result, the light energy is not concentrated at the same positions as the light emitting chips 112a and 112b, and the distribution of light passing through the light diffusion lens 320 is circular, thereby obtaining a uniform image.

Meanwhile, the line width of the support part 328 of the light diffusion lens 320 according to the fifth embodiment of the present invention is narrower than the bottom surface of the light diffusion lens 320 or as shown in FIG. 4. It may be formed similarly to the bottom surface, and the stepped portion 164 illustrated in FIG. 5 may be formed between the inner curved surface 322 and the bottom surface of the light diffusion lens 320, and the light diffusion lens 320 may be formed. A scattering pattern 118 illustrated in FIG. 8 may be formed on at least one of the inner curved surface 322 and the bottom surface.

18 is a cross-sectional view illustrating a liquid crystal display module according to the present invention.

The liquid crystal display module illustrated in FIG. 18 includes a liquid crystal panel 140, a backlight unit, and a bottom cover 150.

The bottom cover 150 accommodates the light emitting package 112 and the light diffusing lens 120 of the backlight unit and supports the diffusion plate 102 and the plurality of optical sheets 130.

The liquid crystal panel 140 implements an image by using light emitted through the backlight unit. To this end, the liquid crystal panel 140 includes a color filter substrate 142 and a thin film transistor substrate 144 facing each other with the liquid crystal interposed therebetween.

The backlight unit is disposed under the liquid crystal panel 140 and provides light to the liquid crystal panel 140. To this end, the backlight unit includes a light emitting package 112, a light diffusing lens 120, a printed circuit board 114, a diffusion plate 102, and a plurality of optical sheets 130.

The light emitting package 112 is mounted on the printed circuit board 114 to be driven by receiving power from the outside to generate light. The light emitting package 112 is formed of at least one light emitting diode (LED) in the form of a chip. For example, the light emitting package 112 includes a light emitting chip that emits blue light and a yellow phosphor that converts blue light into white light.

The light diffusion lenses 120, 220, and 320 are formed in the structure shown in any one of FIGS. 2, 4, 5, 8, 10, and 14 to diffuse the light generated by the light emitting package 112 to diffuse the diffusion plate 102. Investigate with).

The printed circuit board 114 is disposed on the bottom surface of the bottom cover 150 to face the diffuser plate 102. The printed circuit board 114 is formed with a driving power line to which driving power is supplied from the outside. Accordingly, the printed circuit board 114 emits the plurality of light emitting packages 112 by supplying the driving power supplied from the outside through the driving power line to each of the light emitting packages 112. The light emitting package 112 and the light diffusing lens 120 are sequentially formed on the printed circuit board 114, and the reflecting plate is formed on the printed circuit board 114 on which the light emitting package 112 and the light diffusing lens 120 are formed. 160 is formed. In this case, the reflecting plate 160 has an opening 162 having an area greater than or equal to the light diffusing lens 120, and the light diffusing lens 120 is exposed to the outside through the opening 162. The reflective plate 160 reflects light generated from the light emitting package 112 and propagates toward the bottom cover 150 toward the liquid crystal panel 140 to improve light efficiency.

The diffuser plate 102 diffuses the light emitted from the light emitting package 112 to have a uniform distribution and irradiates the plurality of optical sheets 130.

The plurality of optical sheets 130 includes a light collecting sheet 132, a diffusion sheet 134, and a polarizing sheet 136, and the light emitted from the diffusion plate 102 is perpendicular to the front direction of the liquid crystal panel 140. And irradiate to the liquid crystal panel 140.

Although the present invention has been described with reference to the embodiments illustrated in the accompanying drawings, it is merely exemplary, and it will be understood by those skilled in the art that various modifications and equivalent other embodiments are possible. Could be.

112: light emitting package 114: printed circuit board
118: scattering pattern 120,220,320: light diffusion lens
122,222,322: Inner Surface 124,222,324: Outer Surface
128,228,328: Support

Claims (19)

A printed circuit board;
A light emitting package formed on the printed circuit board;
A light diffusion lens formed on the printed circuit board and having an inner curved surface positioned on an upper end of the light emitting package and an outer curved surface diffusing light incident through the inner curved surface;
A reflective plate formed on the printed circuit board on which the light emitting package and the light diffusing lens are formed, the reflecting plate having an opening for exposing each of the light diffusing lenses;
Each of the inner curved surface and the outer curved surface of the light diffusing lens has no inflection point,
Each of the inner curved surface and the outer curved surface is formed in a shape that satisfies Equation 1 and Equation 2 below.
[Equation 1]

In Equation 1, z is a vertical distance from the vertices of the inner surface and the outer surface to the light emitting package located in the negative direction with respect to the vertex, and r is the inner surface and the outer surface from the vertices of the inner surface and the outer surface, respectively The horizontal distance to each outermost part, c is the curvature of each of the inner and outer surfaces, k is the cone constant, and each of a1, a2, a3, ..., an is the 1st, 2nd, 3rd order represents the aspherical surface coefficient,
[Equation 2]
dz / dr <0
In Equation 2, dz is the amount of change in the vertical distance from the vertices of the inner surface and the outer surface to the light emitting package located in the negative direction with respect to the vertex, and dr is the inner surface and The amount of change in the horizontal distance to the outermost part of each of the outer curved surfaces is shown. delete The method of claim 1,
The coefficient range of the inner surface is -10 <c <-0.1, -2 <k <0, 0 <a2 <1.5, 0 <a3 <0.006, 0 <a4 <0.002, and the coefficient of the outer surface is -0.154 <c <0, -10 <k <0, 0 <a2 <0.03, 0 <a3 <0.0006, -0.0006 <a4 <0, -0.000008 <a6 <0. The method of claim 1,
The light diffusing lens is a backlight unit is formed in the form of a meniscus lens having the inner curved surface has a negative power, the outer curved surface has a positive power. The method of claim 1,
And a support part formed between the light diffusing lens and the printed circuit board and providing an accommodation space having a surface area larger than that of the light emitting package. The method of claim 1,
And a stepped portion that forms a step of several tens of micrometers with the bottom surface between the inner curved surface and the bottom surface of the light diffusion lens. The method of claim 6,
And a scattering pattern formed on at least one of an inner curved surface, an outer curved surface, a bottom surface, and a step portion of the light diffusing lens to have a height of several μm. A printed circuit board;
A light emitting package formed on the printed circuit board and having at least two light emitting diodes;
A light diffusion lens formed on the printed circuit board and having an inner curved surface positioned on an upper end of the light emitting package and an outer curved surface diffusing light incident through the inner curved surface;
A reflective plate formed on the printed circuit board on which the light emitting package and the light diffusing lens are formed, the reflecting plate having an opening for exposing each of the light diffusing lenses;
Each of the inner curved surface and the outer curved surface of the light diffusing lens has no inflection point,
The horizontal cross section of the inner curved surface of the light diffusing lens is elliptical,
The inner curved surface is formed in a shape satisfying the following equation (3).
[Equation 3]

In Equation 3, x is the major axis radius of the inner surface of the elliptical horizontal cross section, y is the minor axis radius of the inner surface, c _x is the curvature of the inner surface in the x direction, c _y is the curvature of the inner surface in the y direction k _x represents a conic constant in the x direction, and k _y represents a conical constant in the y direction. delete The method of claim 8,
And a ratio of the long axis radius and the short axis radius is 0.2 to 2 times the ratio of the long side and the short side of the light emitting package. The method of claim 8,
And a support part formed between the light diffusing lens and the printed circuit board and providing an accommodation space having a surface area larger than that of the light emitting package. The method of claim 8,
And a stepped portion that forms a step of several tens of micrometers with the bottom surface between the inner curved surface and the bottom surface of the light diffusion lens. The method of claim 12,
And a scattering pattern formed on at least one of an inner curved surface, an outer curved surface, a bottom surface, and a step portion of the light diffusing lens to have a height of several μm. A printed circuit board;
A light emitting package formed on the printed circuit board and having at least two light emitting chips;
A light diffusion lens formed on the printed circuit board and having an inner curved surface positioned on an upper end of the light emitting package and an outer curved surface diffusing light incident through the inner curved surface;
A reflective plate formed on the printed circuit board on which the light emitting package and the light diffusing lens are formed, the reflecting plate having an opening for exposing each of the light diffusing lenses;
The inner curved surface of the light diffusing lens has more vertices than the number of light emitting chips and an inflection point of more than the number of light emitting chips,
The inner curved surface is formed in a shape satisfying the following equation (4).
[Equation 4]

In Equation 4, z is a vertical distance from the lowest peak of the inner curved surface to the light emitting package relative to the lowest peak, r is a horizontal distance from the central axis of the light diffusion lens to the inner curved surface, A, B, Each of C, D, ... represents secondary, quaternary, sixth, eighth, ... aspherical coefficients. delete The method of claim 14,
2, the inner curved surface of the light diffusing lens has three vertices and two inflection points. The method of claim 14,
And a support part formed between the light diffusing lens and the printed circuit board and providing an accommodation space having a surface area larger than that of the light emitting package. The method of claim 17,
And a stepped portion that forms a step of several tens of micrometers with the bottom surface between the inner curved surface and the bottom surface of the light diffusion lens. The method of claim 18,
And a scattering pattern formed on at least one of an inner curved surface, an outer curved surface, a bottom surface, and a step portion of the light diffusing lens to have a height of several μm.

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