KR101119193B1 - Light source unit and liquid crystal display device having the same - Google Patents

Abstract

Disclosed are a light source unit having improved uniformity of luminance and efficiency of color mixing, and a liquid crystal display having the same. The light source unit includes a point light source and a lens. The point light source is disposed on the substrate and emits light. The lens is curved with an angle of less than 30 degrees with a central normal passing through the center of the point light source and an angle between 20 and 75 degrees with an edge normal connected to the first interface and passing through the edge of the point light source. A point light source is enclosed by including a 2nd interface and the 3rd interface which connects a board | substrate and a 2nd interface. Accordingly, it is possible to improve the uniformity of luminance and the efficiency of color mixing of the light emitted from the light source unit by dividing the interface of the lens into several, and processing the divided interface.

Brightness, color mixing, light emitting diode, lens, interface

Description

LIGHT SOURCE UNIT AND LIQUID CRYSTAL DISPLAY DEVICE HAVING THE SAME

1A and 1B are three-dimensional and cross-sectional views of a Lambertian distribution of light emitted from a point light source.

2A and 2B are light intensity distribution diagrams and enlarged views of the light emitted from the point light source so as to have a uniform brightness in a circle having a radius of 100 mm in a plane having a height of 32.5 mm.

3 is a perspective view of a light source unit according to an embodiment of the present invention.

4 is a cross-sectional view of the light source unit illustrated in FIG. 3 taken along the cutting line I ′.

5 is a shape view of a curved surface of the first interface of the lens included in the light source unit.

6 is a path diagram of the emitted light at the first to third interfaces of the light source unit according to the exemplary embodiment of the present invention.

7 is a light amount distribution diagram of light emitted from a light source unit according to an exemplary embodiment of the present invention.

8 is a path diagram of the emitted light from the lens of the light source unit according to the comparative example of the present invention.

9A is an image chart of light emitted from a light source unit according to an embodiment of the present invention, and FIG. 9B is an image chart of light emitted from a light source unit according to a comparative example of the present invention.

10 is an exploded perspective view of a liquid crystal display according to an exemplary embodiment of the present invention.

<Description of the symbols for the main parts of the drawings>

100: backlight assembly 110: substrate

120: point light source 130: lens

132: first interface 134: second interface

136: third interface 140: reflecting plate

150: light mixing member 160: optical sheets

170: storage container 200: display unit

300: top chassis 400: rear case

500: front case

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light source unit, and more particularly, to a light source unit having increased luminance uniformity and color mixing efficiency, and a liquid crystal display having the same.

In general, a liquid crystal display device refers to a device for displaying an image by precisely controlling a liquid crystal having a characteristic of changing light transmittance corresponding to an electric field. Thus, the liquid crystal display needs light to display an image. In this case, the liquid crystal display displays an image by using external natural light or artificial light provided from a light source provided therein.

The light source includes a light emitting diode (LED), a cold cathode fluorescent lamp (CCFL), a flat fluorescent lamp (FFL), and the like. Among these light sources, cold cathode ray tube lamps and flat panel fluorescent lamps are mainly employed in large display devices, and light emitting diodes are employed in small display devices.

The light emitting diode is generally formed in the shape of a rectangular chip so that light is randomly emitted from the entire rectangular chip, but the diode may be regarded as a kind of point light source. Therefore, a Lambertian distribution, which is a distribution of light randomly emitted from the point light source, may be used as a distribution diagram of light emitted from the chip.

1A and 1B are three-dimensional and cross-sectional views of a Lambertian distribution of light emitted from a point light source.

Referring to FIG. 1A, the Lambertian distribution of light emitted from a point light source placed on a substrate has a spherical shape S formed above the light source. The distance away from the specific point of the spherical surface S to the light source is proportional to the amount of light that the emitted light has at an angle at which a straight line connecting the point and the light source forms a normal line passing through the light source.

In addition, the volume of the solid shape formed by the spherical surface specific region and the light source is proportional to the amount of light that the emitted light has in the solid angle range of the specific region.

Referring to FIG. 1B, the area of the plane formed by the specific portion of the circumference C and the light source is proportional to the amount of light that the emitted light has in the range of the plane angle of the specific portion.

The distance from the circumference C to the light source has a maximum value at an upper normal line of the light source, and has a minimum value on a straight line on which the light source is placed. Further, the distance has a value of approximately 70% of the maximum at a point at which the angle with the normal is approximately 45 degrees. Moreover, the area | region of the plane formed with the said light source occupies about 80% of the original area on drawing in the range which the angle | corner with the said normal line is within 0 degree to 45 degree.

That is, in the Lambertian distribution of light emitted from the point light source, the amount of light emitted is much higher than the horizontal direction component whose normal direction component is perpendicular to the normal line. Therefore, a problem arises in that the uniformity of luminance of the emitted light and the efficiency of color mixing are lowered.

Accordingly, the technical problem of the present invention is to solve such a conventional problem, and an object of the present invention is to provide a light source unit in which the uniformity of luminance of emitted light and the efficiency of color mixing are increased.

Another object of the present invention is to provide a liquid crystal display device having the light source unit.

A light source unit according to one feature for realizing the above object of the present invention includes a point light source and a lens. The point light source is disposed on a substrate and emits light. The lens has an angle of 20 degrees to 75 degrees with a curved first interface having an angle of 30 degrees or less with a central normal passing through the center of the point light source, and an edge normal connected to the first interface and passing through an edge of the point light source. It includes a curved second interface and a third interface connecting the substrate and the second interface surrounds the point light source.

According to another aspect of the present invention, a liquid crystal display device includes a backlight assembly and a liquid crystal panel. The backlight assembly has a point light source and a lens. The point light source is disposed on a substrate and emits light. The lens has an angle of 20 degrees to 75 degrees with a curved first interface having an angle of 30 degrees or less with a central normal passing through the center of the point light source, and an edge normal connected to the first interface and passing through an edge of the point light source. It includes a curved second interface and a third interface connecting the substrate and the second interface surrounds the point light source. The liquid crystal panel displays an image by using light emitted from the backlight assembly.

According to such a light source unit and a liquid crystal panel having the same, the lens surrounding the point light source is divided into several interfaces to effectively reflect and transmit the light emitted from the point light source, thereby providing uniformity in brightness of the emitted light. And the efficiency of color mixing.

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

2A and 2B are light intensity distribution diagrams and enlarged views of the light emitted from the point light source so as to have a uniform luminance in a plane having a height of 32.5 mm into a circle having a radius of 100 mm.

2A and 2B, a point light source is disposed at the center of the coordinates. The amount of light emitted from the point light source is represented by one point on the drawing according to the exit angle, and the first curve CL1 on the drawing shows the points continuously.

That is, the distance between one point of the first curve CL1 and the point light source is proportional to the amount of light emitted from the emission angle of the point. 90 to 270 degree region including 0 degree in the figure represents the upper region of the point light source placed on the substrate.

The first curve CL1 has a maximum distance from the point light source at approximately 80 degrees and 280 degrees, and includes about 80% of the total amount of emitted light in the angle. That is, the ratio of the light amount near a horizontal component to all the emitted light is very high. Therefore, in order to achieve uniformity in luminance, the light amount distribution of the point light source including a large amount of vertical components must be changed.

However, in the drawing, since the first curve CL1 near 0 degrees also has a constant distance from the point light source, the vertical component does not have to be completely removed.

As a result, in order to have the light quantity distribution of the ideal emitted light with uniformity of luminance, the light quantity distribution of the light emitted from the point light source must be changed. It is an object of the present invention and an embodiment to provide a light source unit including a lens surrounding the point light source in order to optimize the light quantity distribution of the emitted light.

3 is a perspective view of a light source unit according to an exemplary embodiment of the present invention, and FIG. 4 is a cross-sectional view of the light source unit illustrated in FIG. 3 taken along a cutting line I ′.

3 and 4, the light source unit includes a substrate 110, a point light source 120, and a lens 130.                     

The point light source 120 is disposed on the substrate 110 with the x-axis as the top surface to emit light. In this case, a light emitting diode is typically used as the point light source 120, and generally has a rectangular chip shape.

The lens 130 surrounds the point light source 120 and contacts the substrate 110. The lens 130 includes first to third interfaces 132, 134, and 136.

The first interface 132 has an angle of about 30 degrees or less with a z-axis including a normal of the point light source 120 with respect to the center M of the point light source. The first interface 132 includes a first curved surface CS1, a first spherical surface SS1, and first to third planes P1, P2, and P3.

The first curved surface CS1 has an angle of about 10 degrees or less with the z-axis based on the center M of the point light source. The first curved surface CS1 has an upper surface shape of an intersection portion of two cylinders perpendicularly intersecting with each other. The shape of the first curved surface CS1 is shown in more detail in FIG. 5.

The first spherical surface SS1 is connected to the first curved surface CS1 and has a sphere centered on a first point O1 of an inner region of the lens 130 surrounded by the lens 130 and the substrate 110. Part of the surface.

When the intersection of the x-axis and the z-axis is (0, 0) and mm is used as a unit, when the width of the point light source 120 is 0.7 mm to 0.8 mm, the first point O1 is approximately (2.02, 0.24) can be a preferable value. In this case, the distance from the first point O1 to the first spherical surface SS1 may be approximately 2.27 mm.

The first spherical surface SS1 is formed up to a portion that meets an imaginary plane extending in parallel in the z-axis direction at the edge E of the point light source.

The first plane P1 is connected to the first spherical surface SS1 and is inclined with respect to the z-axis direction. In this case, under the condition of the first spherical surface SS1, the coordinates of the end of the first plane P1 may have approximately (0.5, 1.93) as a preferable value.

The second plane P2 is connected to the first plane P1 and is formed parallel to the x-axis.

The third plane P3 is connected to the second plane P2 and is inclined with the z-axis direction. In this case, an angle formed by the end of the third plane P3 with the center M of the point light source is about 30 degrees, and an angle formed by the point light source edge E is about 20 degrees.

The second interface 134 has an angle of approximately 20 degrees to 75 degrees with a straight line parallel to the z-axis with respect to the edge E of the point light source. The second interface 134 includes a second spherical surface SS2, a fourth plane P4, and a third spherical surface SS3.

The second spherical surface SS2 is connected to the third plane P3, and an imaginary plane extending vertically toward the x-axis at an end of the third plane P3 and an edge E of the point light source. Is a portion of the surface of the sphere about the meeting second point O2 of the imaginary plane extending parallel to the x-axis.

The fourth plane P4 is connected to the second spherical surface SS2 and extends by a predetermined length d vertically toward the x-axis.

The third spherical surface SS3 is connected to the fourth plane P4 and is centered on the third point O3 spaced apart from the second point O2 by the length d vertically toward the x-axis. It is a part of surface of sphere to make. In this case, the distance from the third point O3 to the third spherical surface SS3 is preferably equal to the distance from the second point O2 to the second spherical surface SS2.

An end portion of the third spherical surface SS3 forms an angle of about 75 degrees with a straight line parallel to the z-axis with respect to the point light source edge E.

The third interface 136 includes a fifth plane P5. The fifth plane P5 is connected to the third spherical surface SS3, extends vertically toward the substrate 110, and is in contact with the substrate 110.

5 is a shape diagram of a first curved surface of a first interface of a lens included in the light source unit.

5, two cylinders are shown that intersect each other perpendicularly. The upper surface of the intersection where the two cylinders intersect is bent in all directions about the fourth point O4. The part belonging to the inside of the quadrangle shape centering on said 4th point O4 among the upper surface of the said intersection part is made into the shape of the said 1st curved surface CS1.

Since the shape of the point light source has a rectangular shape, the luminance of the light emitted from the point light source can be made more uniform by making the first curved surface CS1 have a rectangular shape instead of a circular shape.

6 is a path diagram of the emitted light at the first to third interfaces of the light source unit according to the exemplary embodiment of the present invention.

Referring to FIG. 6, the first output light PL1 emitted from the center of the point light source 120 in the z-axis direction is transmitted through the first curved surface CS1 to become the first transmitted light TL1. The second output light PL2 emitted from the point light source 120 is refracted toward the z-axis direction while passing through the first curved surface CS1 to become the second transmitted light TL2.

The third output light PL3 is reflected from the first spherical surface SS1 to become the first reflected light R1. The first spherical surface SS1 is formed such that an incident angle θ of the third output light PL3 is in a range of 42 to 60 degrees. Conditions optimized for maintaining the incident angle θ have been described with reference to FIG. 4.

Since the refractive index of the lens 130 is approximately 1.49 and the refractive index of the air layer outside the lens 130 is approximately 1, the Brewster angle to be totally reflected is approximately 42.5 degrees. Therefore, when the third output light PL3 enters the first spherical surface SS1, most of the incident angles θ exceed 42.5 degrees, and thus most of the third output light PL3 is reflected.

However, when the outgoing light is incident at an angle of about 40 degrees, since about 30% of light is experimentally transmitted, the third outgoing light PL3 incident on the first spherical surface SS1 at an incidence angle of about 40 degrees to about 42.5 degrees. Some of the will be transmitted.

Meanwhile, the first reflected light R1 travels substantially parallel to the x-axis, and passes through the fourth plane P4 to become the third transmitted light TL3. In this case, the fourth plane P4 serves as a kind of gate for transmitting the first reflected light R1.

The fourth output light PL4 is reflected by the first plane P1 to become the second reflected light R2. The first plane P1 is formed to reflect most of the fourth output light PL4 like the third output light PL3. The fifth output light PL5 is refracted toward the x-axis direction while passing through the second plane P2 to become the fourth transmitted light TL4.                     

The sixth emitted light PL6 is reflected by the third plane P3 to become the third reflected light R3. The seventh output light PL7 is refracted toward the x-axis direction while passing through the second spherical surface SS2 to become the fifth transmitted light TL5.

The eighth output light PL8 is refracted toward the x-axis direction while passing through the third spherical surface SS3 to become the sixth transmitted light TL6. The ninth output light PL9 is refracted toward the z-axis direction while passing through the fifth plane P5 to become the seventh transmitted light TL7.

Therefore, since most of the emitted light PL1 to PL9 are reflected and refracted in a direction parallel to the substrate 110 on which the point light source 120 is disposed, uniformity of luminance and efficiency of color mixing are increased. However, as described with reference to FIGS. 2A and 2B, light having a component perpendicular to the substrate 110 is also required. The light of the vertical component is supplied by the light transmitted through the first curved surface CS1 and the fifth plane P5. In addition, a part of light transmitted through the fourth plane P4 also supplies light of the vertical component.

7 is a light amount distribution diagram of light emitted from a light source unit according to an exemplary embodiment of the present invention.

Referring to FIG. 7, the amount of light emitted from the point light source of the light source unit is shown as a second curve CL2 on the drawing according to the emission angle.

The second curve CL2 has a maximum distance from the point light source at approximately 60 degrees and 320 degrees. Moreover, it has a considerable distance value in the vicinity of 0 degree.

Compared with the light intensity distribution diagrams shown in FIGS. 2A and 2B, there are some differences in the angle with the maximum distance, but the overall curve shape is similar and similar in that they have a constant distance value near 0 degree. .

Therefore, it can be said that it has a light quantity distribution to some extent close to the light quantity distribution of the ideal emitted light which has uniformity of luminance.

8 is a path diagram of the emitted light from the lens of the light source unit according to the comparative example of the present invention.

Referring to FIG. 8, the tenth output light PL10 emitted from the center of the point light source 120 in the z-axis direction is transmitted through the sixth plane P6 to become the eighth transmitted light TL8. The eleventh output light PL11 emitted from the point light source 120 is refracted toward the x-axis direction while passing through the sixth plane P6 to become the ninth transmitted light TL9.

The twelfth output light PL12 is reflected from the sixth plane P6 to become the fourth reflected light R4. The fourth reflected light R4 passes through the seventh plane P7 to become the tenth transmitted light TL10. The thirteenth output light PL13 is refracted toward the z-axis direction while passing through the seventh plane P7 to become the eleventh transmitted light TL11.

The fourteenth output light PL14 is refracted toward the x-axis direction while passing through the second curved surface CS2 to become the twelfth transmitted light TL12. The fifteenth emitted light PL15 is refracted toward the z-axis direction while passing through the eighth plane P8 to become the thirteenth transmitted light TL13.

When comparing an embodiment of the present invention with a comparative example, even in the comparative example, a substantial portion of the emitted light PL10 to PL15 light is reflected and refracted in a direction parallel to the substrate 110 on which the point light source 120 is disposed. Therefore, the comparative example and the embodiment of the present invention have similar aspects in that luminance uniformity and efficiency of color mixing are increased.                     

However, the amount of light in a direction perpendicular to the substrate 110 as the outgoing light PL11 is incident at an interface having an angle of 10 degrees or less to the normal of the point light source 120 in a direction away from the z-axis direction. This is less.

In addition, when the twelfth emission light PL12 is incident on the sixth plane P6, unlike the exemplary embodiment of the present invention, since it is not incident on a spherical surface, the emission position of the twelfth emission light PL12 is emitted. The angle of incidence is not always maintained beyond the Brewster's angle, which is totally reflected.

In addition, in the case of the seventh plane P7, the fourth reflected light R4 and the thirteenth transmitted light TL13 are refracted and transmitted in the z-axis direction, so that the amount of light proceeds in a direction parallel to the substrate 110. This is less.

As a result, the lens according to the embodiment of the present invention is superior to the lens according to the comparative example in terms of an optimized structure for having the ideal light quantity distribution shown in FIGS. 2A and 2B.

9A is an image chart of light emitted from a light source unit according to an embodiment of the present invention, and FIG. 9B is an image chart of light emitted from a light source unit according to a comparative example of the present invention.

9A and 9B, the brightness of the image is more uniform in the light source unit according to an embodiment of the present invention than in the light source unit according to the comparative example. That is, in the comparative example, the brightness of the image in the area close to each point light source is significantly brighter than the brightness of the image in the area far from the point light source.                     

However, in one embodiment of the present invention, the brightness difference according to the distance from the point light source is not large.

That is, the embodiment of the present invention is superior to the comparative example in terms of uniformity of luminance of light and efficiency of color mixing.

10 is an exploded perspective view of a liquid crystal display according to an exemplary embodiment of the present invention.

Referring to FIG. 10, the liquid crystal display includes a backlight assembly 100, a display unit 200, a top chassis 300, a rear case 400, and a front case 500. Compared with FIG. 3, the same reference numerals are given to the same parts, and description is omitted.

The backlight assembly 100 includes a substrate 110, a point light source 120, a lens 130, a reflector 140, a light mixing member 150, optical sheets 160, and a storage container 170. . In this case, the substrate 110, the point light source 120, and the lens 130 define a light source unit.

The reflective plate 140 prevents the light emitted from the lens 130 from leaking in a direction in which the light mixing member 150 is not formed.

The light mixing member 150 is formed to face the upper portion of the lens 130. The light mixing member 150 reflects and transmits the light such that the light emitted from the lens 130 is mixed in the air formed outside the lens 130.

The optical sheets 160 include a diffusion plate 162 and a prism sheet 164. The diffusion plate 162 diffuses the light emitted from the point light source 120 and passes through the light mixing member 150, and the prism sheet 164 collects the diffused light.

The storage container 160 includes a bottom member 162 having a portion opened and a side wall member 164 extending vertically from the bottom member 162. The light source units 110, 120, and 130, the reflecting plate 140, the light mixing member 150, and the optical sheets 160 are sequentially received in the bottom member 162 of the storage container 160.

The display unit 200 includes a liquid crystal panel 210 for displaying an image, a plurality of data side and gate side tape carrier packages (TCP) 220 and 230, and an integrated printed circuit board 240. It includes.

The liquid crystal panel 210 may include an array substrate 212 displaying pixels, a color filter substrate 214 facing the array substrate 212, and between the array substrate 212 and the color filter substrate 214. It includes a liquid crystal layer (not shown) injected into.

The plurality of data side TCPs 220 are attached to a source side of the array substrate 212, and the plurality of gate side TCPs 230 are attached to a gate side of the array substrate 212. The data side and gate side TCPs 220 and 230 apply a driving signal and a timing signal to the liquid crystal panel unit 210 for controlling the driving of the liquid crystal panel unit 210 and the timing of driving the liquid crystal panel unit 210.

One side of the data side TCP 220 is attached to the array substrate 212 and the other side is attached to the integrated printed circuit board 240 to electrically connect the liquid crystal panel unit 210 with the integrated printed circuit board 240. Connect it. The gate side TCP 230 is attached to the array substrate 212 to electrically connect the liquid crystal panel unit 210 with the integrated printed circuit board 240. The integrated printed circuit board 240 receives an electrical signal from the outside and applies the electrical signal to the data side and the gate side TCPs 220 and 230.                     

The data side and gate side TCPs 220 and 230 connected to the liquid crystal panel unit 210 are bent along the outer surface of the sidewall member 174 of the storage container 170, and the integrated printed circuit board 240 is formed. Is seated on the back of the bottom member 172.

The top chassis 300 that is a fixing means is provided on the liquid crystal panel 210. The top chassis 300 covers the effective display area of the liquid crystal panel 210 so as to be exposed to be coupled to the storage container 170 so as to face each other to fix the display unit 200.

The backlight assembly 100, the display unit 200, and the top chassis 300 are accommodated in the rear case 400, and the rear case 400 is provided at the top of the top chassis 300. The liquid crystal display is completed by opposing the 500 with each other.

As described above, according to the present invention, the interface of the lens surrounding the point light source is divided into several according to the emission angle. The shape of each of the divided interfaces is processed to increase the uniformity of luminance and the efficiency of color mixing, where the interfaces are processed into exactly calculated shapes to have an ideal light distribution.

Thus, the distribution of the light transmitted through the processed interfaces may have high uniformity of luminance and high efficiency of color mixing in a predetermined region.

In particular, when using a light emitting diode in the form of a square chip, it is possible to provide a light source unit optimized to have excellent luminance uniformity and color mixing efficiency.                     

Although described above with reference to the embodiments, those skilled in the art can be variously modified and changed within the scope of the invention without departing from the spirit and scope of the invention described in the claims below. I can understand.

Claims (12)

A point light source disposed on the substrate and emitting light; And A curved first interface having an angle of 30 degrees or less with a central normal passing through the center of the point light source, and an angle of 20 degrees to 75 degrees with an edge normal connected to the first interface and passing through an edge of the point light source And a lens surrounding the point light source, the lens including a true second interface and a third interface connecting the substrate and the second interface. The method of claim 1, wherein the first interface is A curved surface having an upper surface shape of two cylindrical intersections perpendicular to each other, A first spherical surface connected to the curved surface and centered on a first point of a lens inner region surrounded by the lens and the substrate; A first plane connected to the first spherical surface and inclined to the central normal, A second plane connected to the first plane and perpendicular to the central normal, And a third plane connected to the second plane and inclined at the center normal. The light source unit of claim 2, wherein the curved surface refracts the light emitted from the point light source in the direction of the center normal line. delete The method of claim 1, wherein the second interface is A second spherical surface centering on a second point which is an intersection of a plane perpendicular to the substrate and a straight line extending from the edge of the point light source in a direction perpendicular to the edge normal while passing through the connection portion with the first interface; , A third spherical surface centered on a third point spaced apart from the second point in a direction parallel to the edge normal, And a fourth plane extending between the second and third spherical surfaces and extending in the edge normal direction. 6. The light source unit according to claim 5, wherein the lengths of the radii of the third and fourth spherical surfaces are the same. 6. The light source unit according to claim 5, wherein the second and third spherical surfaces refract light emitted from the point light source in a direction perpendicular to the edge normal. The method of claim 5, wherein the first interface comprises a first spherical surface centered on a first point of the lens inner region surrounded by the lens and the substrate, And the fourth plane transmits light reflected from the first spherical surface. The light source unit of claim 1, wherein the third interface includes a fifth plane extending in the edge normal direction. 10. The light source unit according to claim 9, wherein the fifth plane refracts light emitted from the point light source in the edge normal direction. The light source unit according to claim 1, wherein the point light source is a light emitting diode. A point light source disposed on the substrate and emitting light; A curved first interface having an angle of 30 degrees or less with a central normal passing through the center of the point light source, and an angle of 20 degrees to 75 degrees with an edge normal connected to the first interface and passing through an edge of the point light source A backlight assembly having a lens surrounding the point light source, wherein the backlight includes a second interface and a third interface connecting the substrate and the second interface; And And a liquid crystal panel which displays an image by using light emitted from the backlight assembly.

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