NL1030209C2 - BACKGROUND LIGHTING UNIT AND LIQUID-CRYSTAL SCREEN DEVICE WHICH USES THIS. - Google Patents

Description

Title: Backlight unit and liquid crystal display device that uses these

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. § 119 of the Korean Patent Application Nos. 10-2004-84960, filed on October 5, 2004 and 10-2004-98697, filed on November 29, 2004 at the Korean Office for Intellectual Property, which are incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the invention

The present general inventive concept relates to a backlight unit and a liquid crystal display device (LCD) that uses these, and more particularly, to a direct backlight type backlight unit and an LCD device that uses these.

2. Description of the prior art 20

An LCD is a type of a non-emitting display panel and requires an external light source to produce an image, since the LCD itself does not emit light. Thus, a backlight unit is placed behind the LCD and emits light.

[0004] Backlight units are classified into direct lighting type backlight units and edge lighting type backlight units according to a position in which light sources 1030209 of backlight units are arranged. For a direct lighting type background lighting unit, a number of light sources placed under the LCD emit light on an LCD screen. For an edge illumination type background ratio unit, a light source positioned along a side wall of a fiber optic panel (LGP) radiates light to the LCD panel via the LGP.

The direct illumination type background ratio unit can use light emitting diodes (LEDs) which emit Lambertian radiation as a point-shaped source.

Figure 1 illustrates a typical arrangement of LEDs 5 for a conventional direct lighting type background ratio unit using the LEDs 5 as point light sources. Referring to Figure 1, the LEDs 5 are arranged in a two-dimensional matrix on a printed circuit board (PCB) substrate 1 with equal gaps p. When the conventional background ratio unit is measured and observed from a front thereof, four corners of the background ratio unit appear to be dark due to a lack of light in the four corners.

SUMMARY OF THE INVENTION

The present general inventive concept provides a background ratio unit to improve brightness uniformity by improving an arrangement of luminous device units to prevent angles from turning out to be dark due to a lack of amount of light in the corners, and a liquid crystal display device (LCD) which uses this background ratio unit.

Additional aspects and advantages of the present general inventive concept will be provided in part in the description which follows 3 and in part will be clear from the description, or may be learned by using the general inventive concept.

The foregoing and / or other aspects and advantages of the present general inventive concept can be achieved by providing a backlight unit comprising a base plate and a plurality of light emitting device units disposed on the base plate with different spacing spaces so that the light emitting device units are closer to are arranged on edges of the base plate then in the center of the base plate.

The number of light emitting device units can be arranged on the base plate in n rows and the light emitting device units can be arranged closer to each other at edges of the at least one outer row than at the center thereof. The spacing gaps between the light emitting device units that are arranged in the at least one outer row can increase from the edges of the at least one outer row to the center thereof. The equal number of light emitting device units can be arranged in each of the n rows. The light emitting device units in each of the remaining rows can be arranged with equal spacing spaces.

When a gap between the light emitting device units is arranged in each of the remaining rows dO, a minimum space between the light emitting device units is arranged at the edges of the at least one outer row d1, and a maximum space between the light emitting device units is arranged in the middle of the at least one outer row d2, then the light emitting device units can be arranged to satisfy d1 <dO <d2.

The number of luminous device units can be arranged on the base plate in n rows and a number of luminous device units, which is arranged in the at least one outer row, can be larger than a 4 number of luminous device units, which is arranged in each of the remaining rows.

The light emitting device units in each of the remaining rows can be arranged with equal spacing spaces. The spacing gaps between the light emitting device units that are arranged in the at least one outer row can increase from the edges of the at least one outer row to the center thereof.

The number of light emitting device units can be arranged on the base plate in n rows and the arrangement gaps between outer rows along an arrangement direction of the n rows can be narrower than the arrangement gaps between intervening rows. The equal number of light emitting device units can be arranged in each of the n rows.

Each light emitting pixel may comprise a light emitting diode (LED) chip to generate light, and a collimator to collimate the generated light through the LED chip. The collimator can be a side emitter to emit incident light in a substantially lateral direction. The collimator can be dome-shaped.

The background lighting unit may further comprise an optical plate and a number of reflection mirrors, which is placed on a surface of the optical plate to reflect light radiating up directly from the light emitting device units. The optical plate can be made of transparent polymethyl methacrylate (PMMA) or can be a transmissive diffusion plate.

The light emitting device units can emit red, green and blue color beams, and can be arranged in alternation in color in each row.

The background lighting unit may further comprise a first transmissive diffusion plate, which is placed above the light emitting device units and transmits and scatters incident light. The background lighting unit may further comprise a reflection diffusion plate 5, which is placed under the light emitting device units and reflects and scatters incident light.

The background enhancement unit may further comprise at least one of a brightness enhancement layer (BEF) to improve the direction of the light transmitted through the first transmissive diffusion plate and a polarization enhancement layer to improve polarization efficiency.

The foregoing and / or other aspects of the present general inventive concept can also be achieved by providing an LCD device comprising a liquid crystal screen, and a background ratio unit to irradiate light beams onto the liquid crystal screen and providing a base plate, and a plurality of light emitting device units arranged on the base plate with different spacing spaces, so that the light emitting device units are arranged closer to each other at edges of the base plate than in the center of the base plate.

The foregoing and / or other aspects of the present general inventive concept can also be achieved by providing a background releasing unit that can be used with a liquid crystal display (LCD) device, which includes a base plate 20, and a plurality of rows of light emitting units placed on the base plate to emit light, the number of rows comprising outer rows placed at opposite ends of the base plate and having light emitting units spaced apart with smaller gaps at the ends thereof than in the middle thereof, and inner rows placed between the outer rows on the base plate, these comprising light emitting units spaced apart with equal gaps at the ends and in the middle thereof.

The foregoing and / or other aspects of the present general inventive concept can also be achieved by using a background lighting unit with a liquid crystal display (LCD) device, which includes a base plate, and a plurality of rows of light emitting Units placed on the base plate to emit light and arranged so that outer rows of light emitting units with smaller gaps are spaced apart than the inner rows of light emitting units.

The foregoing and / or other aspects of the present general inventive concept can also be achieved by providing a backlight unit with a liquid crystal display (LCD) device, which includes a base plate, and light emitting units mounted on the base plate separated by spaces of different dimensions in at least one of the length direction of the base plate and width direction of the base plate according to a position of each of the light emitting units on the base plate. The foregoing and / or other aspects of the present general inventive concept can also be achieved by providing a liquid crystal display device comprising a liquid crystal display and a backlight unit to emit light toward the liquid crystal display, and which has a base plate, a first number of light emitting device units placed in a first surface unit of the base plate, and a second number of light emitting device units placed in a second surface unit of the base plate, which is the same size as the first surface unit.

The foregoing and / or other aspects of the present general inventive concept can also be achieved by providing a liquid crystal display device comprising a liquid crystal display and a backlight unit to emit light toward the liquid crystal display, which has a base plate and a first unit which has first luminous device units 30, which are placed in a first area of the base plate to emit light 7 with a first brightness, and a second unit which has second luminous device units placed in a second area of the base plate to emit light with a second brightness, wherein the first area differs from the second area and the first area has the same dimensions as the second area.

The foregoing and / or other aspects of the present general inventive concept can also be achieved by providing a backlight unit comprising a base plate, a number of first luminous device units disposed in a first area of the base plate, and a number of second luminous devices device units disposed in a second area of the base plate, the number of first luminous device units being equal to the number of second luminous device units and the first area having a different size than the second area.

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BRIEF DESCRIPTION OF THE DRAWINGS

These and / or other aspects and advantages of the present general inventive concept will become clear and more easily appreciated from the following description of the embodiments, taken in combination with the accompanying drawings, in which:

Figure 1 is a view illustrating a typical arrangement of light emitting diodes (LEDs) for a conventional direct lighting type background lighting unit which uses LEDs as point light sources;

Figure 2 is a sectional view illustrating a backlight unit according to an embodiment of the present general inventive concept; 8

Fig. 3 is a plan view schematically illustrating an arrangement of the light emitting pixels of the background lighting unit of Fig. 2 according to an embodiment of the present general inventive concept; Fig. 4 is a plan view schematically illustrating an arrangement of the light emitting pixels of the background lighting unit of Fig. 2, according to another embodiment of the present general inventive concept;

Fig. 5 is a plan view schematically illustrating an arrangement of 10 luminous pixels of the background lighting unit of Fig. 2, according to another embodiment of the present general inventive concept;

Figure 6 is an enlarged sectional view illustrating one of the light emitting pixels of the background lighting unit of Figure 2;

Figure 7 is a sectional view illustrating a backlight unit according to another embodiment of the present general inventive concept;

Fig. 8A is a view illustrating a simulation result of uniformity when the luminous pixels are arranged in a conventional arrangement;

Fig. 8B is a view illustrating a simulation result of uniformity when the light emitting pixels are arranged according to an embodiment of the present general inventive concept;

Figure 9 is a view schematically illustrating gaps on which the light emitting pixels are arranged to obtain the results illustrated in Figures 8A and 8B; 9

Figure 10 is a view schematically illustrating measurement areas and points used in determining the uniformity and determining an improvement effect of the dark portions; and

Figure 11 is a view that schematically illustrates a liquid crystal display (LCD) device that uses a backlight unit according to an embodiment of the present general inventive concept.

DETAILED DESCRIPTION OF THE 10 PREFERRED EMBODIMENTS

Reference is now made in detail to the embodiments of the present general inventive concept, the examples of which are illustrated in the accompanying drawings, in which the same reference numerals always refer to the same elements. The embodiments are described below to explain the present general inventive concept with reference to the figures.

Figure 2 illustrates a background lighting unit 100 according to an embodiment of the present general inventive concept. Referring to Figure 2, the backlight unit 100 includes a plurality of light emitting pixels 10 disposed on a base plate 101, a transmissive diffusion plate 140 disposed above the plurality of light emitting pixels 10 and transmitting and scattering incident light, and a reflection diffusion plate 110 disposed. reflects and scatters below the number of luminous 25 pixels 10 and incident light.

Here, "above" refers to a main direction of propagation of light from a light emitting diode (LED) chip 11 in each of the light emitting pixels 10, while "below" refers to an opposite direction. The main direction of propagation of the light corresponds essentially to a central axis C (see Figure 6) of each luminous pixel 10.

10

The base plate 101 serves as a substrate on which the number of luminous pixels 10 is arranged. The base plate 101 can be a printed circuit board (PCB) to which the light-emitting diode (LED) chips 11 are electrically coupled. Alternatively, the background lighting unit 100 may comprise the base plate 101 and a PCB to control the light emitting pixels 10 separately. Gaps between the number of luminous pixels 10 differ such that the luminous pixels 10 are arranged closer to each other at edges of the base plate 101 than in the center of the base plate 101.

Figure 3 schematically illustrates an arrangement of the luminous pixels 10 of Figure 2 according to an embodiment of the present general inventive concept. Referring to Figure 3, the light emitting pixels 10 are arranged on the base plate 101 in a matrix of n rows Li through Ln. Gaps between adjacent rows may be larger than the gaps between the luminous pixels 10 in each row.

As illustrated in Figure 3, the light emitting pixels 10 are arranged closer together at edges of the at least outer rows Li and Ln than in a center of the outer rows Li and Ln. That is, the luminous pixels 10 are arranged in the outer rows Li and Ln with gaps that increase from the edges to the center. On the other hand, the light emitting pixels 10 are arranged in each of the remaining rows L2 through Ln-i with equal gaps.

Accordingly, the gaps between the luminous pixels 10, which are arranged at the edges of the outer rows L 1 and L n, are smaller than the gaps between the luminous pixels 10, which are arranged in each of the remaining rows L 2 through L n-1. .

The equal number of luminous pixels 10 can be arranged for each row. Accordingly, the gaps between the luminous pixels 10 arranged in the middle of the outer rows L 1 and L n are larger than the gaps between the luminous pixels 10, 11 arranged with equal gaps in each of the remaining rows L 2 to with Ln-i.

For example, when the spacing between the adjacent light emitting pixels 10 arranged in each of the remaining rows L2 is through Ln-i d0, a minimum spacing between the adjacent light emitting pixels 10 arranged at the edges of the outer rows L 1 and L n is d 1, and a maximum spacing between the adjacent light emitting pixels 10 arranged in the center thereof is d 2, then the number of light emitting pixels 10 can be arranged to satisfy d 1 <d 0 <d 2 10 .

By varying only the spacing between the luminous pixels 10 arranged in the outer rows L 1 and L n, while maintaining the same number of luminous pixels 10 arranged on each of the rows L 1 through L n , it is possible to use the equal number of luminous pixels 10 as used when the luminous pixels 10 are arranged in each row with equal gaps. This prevents the creation of dark areas in the four corners of the background lighting unit 100 without incurring additional manufacturing costs, thereby resulting in an improvement in overall brightness uniformity.

Figure 3 illustrates an example in which the light emitting pixels 10 are arranged in five rows, wherein the light emitting pixels 10 are arranged closer together at the edges of the first and fifth rows L1 and L5 than in the middle thereof, while the light emitting pixels 10 in each of the three intermediate rows L2 to L4 are arranged with equal gaps. The number of rows and the number of luminous pixels 10 arranged in each row may vary depending on the design requirements.

When the light emitting pixels 10 are arranged as illustrated in Figure 3, an amount of light in the four corners of the background lighting unit 100 can be increased in relation to the 12 light emitting diode arranged with equal intervals, thereby the overall brightness uniformity magnifying by the same number of luminous pixels 10, while preventing the four corners of the background ratio unit 100 from turning dark due to a shortage in the amount of light.

The brightness uniformity of the background conditioner unit 100 is crucial to determine the performance of a surface light source. Since the brightness measured in the four angles of the background ratio unit 100 is the lowest, the uniformity of the background ratio unit 100 tends to decrease. Although the arrangement of the light emitting pixels 10 according to the embodiment of Figure 3, wherein the gaps between the light emitting pixels 10 in the four corners are small, the brightness uniformity improves, while the creation of dark areas in the four corners is prevented.

The number of luminous pixels 10 is not limited to the arrangement of the embodiment of Figure 3, and can be arranged in various ways. Figures 4 and 5 schematically illustrate arrangements of the luminous pixels 10 of Figure 2 according to various other embodiments of the present general inventive concept. While Figures 4 and 5 illustrate that the total number of luminous pixels 10 is limited for better visualization compared to what is shown in Figure 3, the number of luminous pixels 10 may be greater than illustrated in Figures 4 and 5. In addition, while the Figures 4 and 5 illustrate that the luminous pixels 10 are arranged in 6 rows, the number of rows may vary depending on the design requirements.

Referring to Figure 4, the number of light emitting pixels 10 can be arranged in n rows and a number of light emitting pixels 10 arranged in at least one outer row, for example Li and L n, can be greater than a number of light emitting pixels 10 that is arranged in each of the 13 remaining rows L2 to Ln-i. Furthermore, the light emitting pixels 10 are arranged closer together at edges of the outer rows Li and Ln than in a center thereof.

Similar to the embodiment of Figure 3, the luminous pixels 10 can be arranged in the outer rows Li and Ln with gaps that increase from the edges to the center.

Luminous pixels 10 in each of the remaining rows L2 through Ln-i can be arranged with equal gaps. Since a larger number of light emitting pixels 10 can be arranged in the outer rows Li 10 and L n, the light emitting pixels 10 arranged in the middle of the outer rows Li and L n can be arranged with equal intervals as the light emitting pixels 10 in each of the remaining rows L2 to Ln-i.

The arrangement of the plurality of light emitting pixels 10 illustrated in Figure 4, wherein the light emitting pixels 10 are arranged closer together at the edges of the backlight unit 100 than in the center thereof, prevents the creation of dark portions in the corners of the background lighting unit 100 due to a shortage of light and thereby improving the overall brightness uniformity of the background lighting unit 100.

Figure 5 schematically illustrates an arrangement of the light emitting pixels 10 of Figure 2 according to another embodiment of the present general inventive concept. Referring to Figure 5, the number of luminous pixels 10 is arranged on the base plate 101 in n rows, and a gap Y1 between the outer rows along an arrangement direction of the n rows is smaller than a gap Y between the intervening rows. The number of luminous pixels 10 and the gaps between the adjacent luminous pixels 10 in each row may be the same as illustrated in Figure 5, but the present general inventive concept is not limited thereto.

14

The arrangement as illustrated in Figure 5, in which the luminous pixels 10 are arranged closer together in the outer rows than in the intermediate rows prevents the creation of dark portions in the corners of the backlight unit 100 due to a shortage of quantity. light and thereby improves the overall brightness uniformity of the background lighting unit 100.

Figure 5 illustrates an example in which the gaps between the rows differ and the luminous pixels 10 in each row are arranged with equal gaps. However, the gaps between the luminous pixels 10 and at least one outer row can be made smaller at the edges of the at least one outer row than in a center thereof and the gaps between the rows may differ.

If a direction in which each line extends is a horizontal direction and the arrangement direction of the rows is a vertical direction, the overall brightness uniformity of the backlight unit 100 can be improved by changing the gaps between the luminous pixels 10 in the horizontal and / or vertical directions, as illustrated in Figures 3 to 5 and in particular, by arranging the luminous pixels 10 closer together at the edges of the background lighting unit 100 than in the center thereof. Figures 3 and 4 here illustrate the arrangements that can improve the brightness and prevent formation of dark portions by reducing the gaps between the light emitting pixels 10 in the four corners of the backlight unit 100 and increasing the amount of light thereon. Figure 5 illustrates the arrangement in which the gaps between the luminous pixels 10 vary along the vertical direction, while maintaining the same number of luminous pixels 10 for each row.

Fig. 6 is an enlarged sectional view illustrating a luminous pixel 10. Referring to Figure 6, a luminous pixel 10 may include the LED chip 11 to generate light and a side emitter 13 that serves as a collimator to collimate light generated by the LED chip 11 and to collimate the collimated light into a substantially lateral direction.

The LED chip 11 can be combined with the side radiator 13 when it is mounted on a base 12. The LED chip 11 can be glued close to the side radiator 13 to maximize an amount of light transmitted by the LED chip 11 is radiated to the side radiator 13.

The light emitting pixels 10 can emit red (R), green (G) and blue 10 (B) color beams. In this case, the light emitting pixels 10 comprise the LED chips 11 to generate R, G and B, respectively, color beams. In each of the rows Li and Ln, the light emitting pixels 10 that emit the R, G and B color beams can be arranged arranged according to color.

The number of light emitting pixels 10 for each color beam arranged in each row may differ depending on an intensity of the color beams emitted from there.

The intensities of R, G, and B color beams emitted from the corresponding LED chips 11 may be different from each other.

For example, the intensity of the G color bundle may be lower than that of the R and B color bundles. Thus, for example, the number of red luminous pixels 10 for each row can be the same as that of blue luminous pixels 10, and the number of green luminous pixels 10 can be twice as large as the number of red or blue luminous pixels 10. The red , green and blue luminous pixels 10 can be arranged in any row in the order R, G, G, B or B, G, G, R.

Alternatively, the light emitting pixels 10 can all emit white light. That is, each luminous pixel 10 may comprise the LED chip 11, which generates white light.

16

When the backlight unit 100 includes luminous pixels 10 that include LED chips 11 that generate R, G, and B color beams or the luminous pixels 10 with the LED chips 11 that generate the white light, then a liquid crystal display ( LCD device 5 comprising the backlight unit 100 displaying a color image.

As illustrated in Figure 6, the side radiator 13 may comprise a transparent body made of a transparent material. More specifically, the side radiator 13 may comprise a funnel-shaped reflection surface 14 slanting relative to the central axis C, a first refractive surface 15 rotated inclined relative to the central axis C to displace light reflected from the reflection surface 14. and a second refraction surface 17, which extends as a convex curve from the base 12 to the first refraction surface 15. Light radiating from the LED chip 11 to the reflection surface 14 or the side emitter 13 is reflected from the reflection surface 14 to the first refraction surface 15 and then broken from the first refraction surface 15 in an approximately lateral direction. Light emitted directly from the LED chip to the second refraction surface 17 is refracted from the second refraction surface 17 in an approximately lateral direction.

Here, the side emitter 13 can be of any other shape that can emit incident light from the LED chip 11 in the approximately lateral direction.

Referring back to Figure 2, the reflection diffusion plate 110 reflects and scatters incident light such that the reflected light is propagated upwards. The reflection diffusion plate 110 is placed on the base plate 101 below the light emitting pixels 10. Accordingly, the reflection diffusion plate 110 may have a number of holes through which the corresponding light emitting pixels 10 can pass. The 17 reflection diffusion plate 110 is placed on the base plate 101, the luminous pixels 10 being inserted into the plurality of holes.

The transmissive diffusion plate 140 is spaced above a lower portion 100a of the backlight unit 100, i.e., the side-emitting light-emitting pixels 10 and the reflection diffusion plate 110, with the predetermined distance d. The transmissive diffusion plate 140 transmits and scatters incident light.

If the transmissive diffusion plate 140 is placed too close to the light emitting pixels 10, the area in which the light emitting pixel 10 is positioned appears brighter than a remaining area, resulting in a decrease in brightness uniformity. Furthermore, as a distance between the transmissive diffusion plate 140 and a luminous pixel 10 increases, a thickness of the backlight unit 100 increases. Thus, it can be determined that the distance d between the transmissive diffusion plate 140 and the lower part 100a of the backlight unit 100, which comprises the light emitting pixel 10 and the reflection diffusion plate 110, can be minimized within a range in which light can be mixed enough as desired.

While most of the light generated by the LED chip 11 in each luminous pixel 10 is emitted by the side emitter 13 in the approximately lateral direction, a portion of the light (eg, approximately 20%) can be directly be propagated upwards from the side radiator 13.

Due to the presence of the light traveling up the side emitter 13, light spots located at positions of the LED chips 11 may become visible from above the background lighting unit 100. Furthermore, when the LED chips 11, which emit the R, G and B color beams are used to display a color image, the colors of the LED chips 11 can be seen from above the background lighting unit 100.

18

Thus, the background lighting unit 100 may further comprise a number of reflection mirrors 120, which are placed on a surface of an optical plate 130 and which reflect light that radiates directly upwards from the luminous pixels 10. The number of reflection mirrors 120 is arranged on the surface of the optical plate 130 to correspond to the location of the luminous pixels 10. That is, each of the number of reflection mirrors 120 is placed above a corresponding luminous pixel 10.

The optical plate 130 on which the number of reflection mirrors 120 is arranged can be made of a transparent polymethyl methacrylate (PMMA) which transmits light. Alternatively, the optical plate 130 may be a second transmissive diffusion plate.

Each of the plurality of reflection mirrors 120 may be spaced apart from the corresponding light emitting pixels 10 by a predetermined distance. To maintain the distance, the optical plate 130 can be supported by a support 135. The support 135 supports the optical plate 130 relative to the reflection diffusion plate 110 or the base plate 101.

Using the second transmissive diffusion plate as the optical plate 130 allows the light to be spread out sufficiently compared to the use of only the reflection diffusion plate 110 and the transmissive diffusion plate 140, thereby reducing the distance between the transmissive plate 140 and a luminous pixel 10, ie, the distance d between the transmissive diffusion plate 140 and the lower part 100a of the background lighting unit 100. This results in a reduction in the thickness of the background lighting unit 100.

When the second transmissive diffusion plate is used as the optical plate 130, light transmittance is smaller than when the transparent PMMA is used. Thus, whether the transmissive diffusion plate or the transparent PMMA can be used as the optical plate 130 depending on whether limiting the thickness of the backlight unit 100 is more important than increasing the light emission ratio.

Meanwhile, the backlight unit 100 further comprises a brightness enhancement layer (BEF) 150 to improve a direction of light transmitted through the transmissive diffusion plate 140 and a polarization enhancement layer 170 to improve polarization efficiency.

The BEF 150 is used to refract and focus the light transmitted through the transmissive diffusion plate 140 to enrich the direction of the light, thereby increasing the brightness of the light. The polarization enrichment layer 170 transmits one type of polarized light beam, eg, a p / polarized light beam, while it reflects another type of polarized light beam, eg, a p-polarized light beam, thus allowing most incident light beams to be converted into p-polarized beams as the incident light beams are transmitted through the polarization enrichment layer 170.

An LCD device that uses the backlight unit 100 includes a liquid crystal screen placed above the backlight unit 100. As is well known, when one linearly polarized beam passes through a liquid crystal layer in a liquid crystal screen, a direction of a liquid crystal control changed by an applied electric field, so that the polarization of the beam is changed, thereby allowing image information to be displayed on the liquid crystal screen.

Since the efficiency of light use is improved if incident light on the liquid crystal screen has a single polarization state, use of the polarization enrichment layer 170 in the backlight unit 100 can increase optical efficiency.

20

As described above, using the backlight unit 100 for the LCD device prevents the four corners of the backlight unit 100 from getting dark and thereby improving the brightness uniformity, whereby a high quality image with a uniform brightness over an entire screen of the LCD device is provided.

Figure 7 is a sectional view illustrating a backlight unit 100 'according to a second exemplary embodiment of the present general inventive concept.

While the background lighting unit 100 of Figure 2 comprises the luminous pixels 10, each having the side radiator 13 as a collimator, the background lighting unit 100 'of Figure 7 comprises luminous pixels 50, each having a dome-shaped collimator 60. The remaining components in the background lighting unit 100 of Figure 7 have substantially the same functions as their equivalents illustrated in Figure 2, except for the light-emitting pixel 50 with the dome-shaped collimator 60. Similar reference numerals in the drawings refer to the same elements, and so these descriptions will be omitted.

The effect of enhancing the dark portions when the light emitting pixels 10 (50) are arranged closer together at the edges of the outer rows than at the center thereof, as described above in the backlight unit 100 will become more detailed described with reference to Figures 8A and 8B. Fig. 8A illustrates a result of an optical simulation when the light emitting pixels 10 (50) are arranged in a conventional arrangement, and Fig. 8B illustrates a result of an optical simulation when the light emitting pixels 10 (50) are arranged according to an embodiment of the present general inventive concept.

The results illustrated in Figures 8A and 8B are obtained when the light emitting pixels 10 (50) are arranged in five rows, 21 and 19 red, 38 green and blue light emitting pixels are arranged in the order R, G, G , B or B, G, G, R, for each row, a total of 76 luminous pixels 10 (50) are arranged within width of 960 mm, and a gap between the rows is 105 mm, as illustrated in Figure 9.

Fig. 8A corresponds to a case where the light emitting pixels 10 (50) are arranged in each row at equal intervals, and Fig. 8B corresponds to a case where the light emitting pixels 10 (50) are arranged closer together at the edges of first and fifth rows then in the middle thereof and arranged with equal gaps in the second to fourth rows.

As is clear from the portions indicated by Aconventioneei in Figure 8A and the present invention in Figure 8B, the four corners of a backlight unit 100 appear brighter as luminous pixels 10 (50) are arranged closer to each other at the edges of the outer rows than in the middle thereof, then when the luminous pixels 10 (50) are arranged in each row with equal gaps.

As a result of calculating the effect of improvements in the evenness and removing the dark portions using the optical simulation results, this embodiment of the present general inventive concept shows about 3% enrichment in uniformity and of about 19% in removing the dark portions above the conventional method, which exhibits a uniformity of 86% and removal of dark portions of 76%. That is, this embodiment of the present general inventive concept exhibits a uniformity of about 89% and a removal of the dark portions of about 95%.

The resulting improvements in the evenness and removal of the dark portions is measured using 22 measurement ranges and points, as illustrated in Figure 10. As illustrated in Figure 10, the measurement points include a central point 1, four points 2, 3, 4 and 5 positioned 339 mm in width and 191 mm in length from the center point 1 and four corner points 6, 7, 8 and 9 positioned 484 mm in width and 261.5 mm in length from the center point 1. The width of each measured point is 50 mm.

When T1, T2, T3, T4, T5, T6, T7, T8 and T9 refer to brightness measured at points 1, 2, 3, 4, 5, 6, 7, 8 and 9 respectively, the uniformity becomes represented as a percentage of a minimum of T2, T3, T4 and T5 divided by T1 and the removal of the dark portions is expressed as a percentage of a minimum of T6, T7, T8 and T9 divided by T1.

The evenness is typically measured at points positioned at a distance corresponding to about 10% facing inwards from the edges. Points specified in the American

National Standards Institute (ANSI), which is an international standard used in calculating uniformity, corresponds to the center of nine equal-sized rectangles, which cover the entire image, i.e., points 2, 3, 4 and 5.

The result of calculating the improvement in the evenness and the removal of the dark portions, using the optical simulation results, prove that the arrangement of the light emitting pixels according to this embodiment of the present general inventive concept can improve uniformity, while this significantly prevents dark areas from forming without affecting the evenness.

Figure 11 schematically illustrates an LCD device that uses the backlight unit 100 according to an embodiment of the present general inventive concept.

Referring to Figure 11, the LCD device includes the 23 backlight unit 100 and a liquid crystal display 300, which is placed above the backlight unit 100. The liquid crystal display 300 is coupled to a driver circuit. Since the detailed configuration of the liquid crystal screen 300 and screen operation using a driver circuit are well known, a description will not be given.

[0095] In a background lighting unit according to the embodiment of the present general inventive concept, a plurality of light emitting pixels are arranged closer together at the edges of a base plate than in the center thereof, by varying gaps between the plurality of light emitting pixels, forming dark areas in the corners of the base plate due to a lack of light can be prevented, while overall brightness uniformity is improved.

[0096] Although a number of embodiments of the present general inventive concept have been shown and described, those skilled in the art will realize that changes may be made within these embodiments without departing from the principles and character of the present inventive concept, of which the framework is defined in the appended claims and their equivalents.

Claims (37)

A background lighting unit comprising: a base plate; and a plurality of light emitting device units disposed on the base plate with different spacing spaces so that the light emitting device units are arranged closer together at edges of the base plate than in a center of the base plate. The backlight unit of claim 1, wherein the number of light emitting device units is arranged on the base plate in 10 rows, and the number of light emitting device units is arranged closer to each other at edges of at least one outer row than in a center thereof. 3. Backlight unit according to claim 2, wherein the spacing spaces between the light emitting device units that are arranged in the at least one outer row increase from the edges of the at least one outer row to the center thereof. 4. Backlight unit according to claim 2, wherein the equal number of light-emitting device units is arranged in each of the n rows. 5. Backlight unit according to claim 2, wherein the light-emitting device units are arranged in each of the remaining rows with equal spacing spaces. 1030209 6. Backlight unit according to claim 5, wherein when a gap between the light emitting device units is arranged in each of the remaining rows dO, a minimum space between the light emitting device units is arranged at the edges of the at least one outer row d1, and a maximum space between them between the light emitting device units arranged in the center of the at least one outer row d2, then the light emitting device units are arranged to satisfy d1 <d0 <d2. The backlight unit of claim 1, wherein the number of light emitting device units is arranged on the base plate in n rows, and wherein a number of light emitting device units arranged in at least one outer row is greater than a number of light emitting device units arranged in each of the remaining rows. 15 The backlight unit of claim 7, wherein the light emitting device units are arranged in each of the remaining rows with spaced up gaps. The backlight unit of claim 7, wherein the suspension gaps between the light emitting device units arranged in the at least one outer row increase from the edges of the at least one outer row to the center thereof. The backlight unit of claim 1, wherein the plurality of light emitting device units are arranged on the base plate in n rows, and wherein the mounting spaces between outer rows along an arrangement direction of the n rows are narrower than the mounting spaces between intermediate rows. 30 The backlight unit of claim 10, wherein the equal number of light emitting device units is arranged in each of the n rows. 12. The backlight unit of claim 1, wherein each of the plurality of light emitting device units comprises: a light emitting diode (LED) chip for generating light; and a collimator to collimate the light generated by the LED chip. The backlight unit of claim 12, wherein the collimator comprises a side emitter to emit incident light in a substantially lateral direction. 14. Backlight unit according to claim 12, wherein the collimator is dome-shaped. The backlight unit of claim 1, further comprising: an optical plate; and a plurality of reflection mirrors disposed on a surface of the optical plate and reflecting light emanating directly from the light emitting device units. 16. Backlight unit according to claim 15, wherein the optical plate comprises one of a transparent polymethyl methacrylate (PMMA) plate and a transmissive diffusion plate. 17. Backlight unit according to claim 1, wherein the light emitting device units emit red, green and blue color beams 30, which are arranged alternately on color on the base plate. The background lighting unit according to any of claims 1-17. wherein it further comprises: a first transmissive diffusion plate which is placed above the luminous device units and transmits and scatters incident light 19. Backlight unit according to claim 18, wherein it further comprises: a reflection diffusion plate placed under the light emitting device units and reflecting and scattering incident light. 20. Background enhancement unit according to claim 18, wherein it further comprises: at least one of a brightness enhancement layer (BEF) to improve the direction of the light transmitted through the first transmissive diffusion plate and a polarization enhancement layer to improve polarization efficiency. A liquid crystal display device comprising: a liquid crystal display; and the background conditioner unit according to any of claims 1-17 which emits light on the liquid crystal screen. 22. Device as claimed in claim 21, further comprising: a first transmissive diffusion plate which is placed above the light emitting device units and transmits and scatters incident light. 23. Device as claimed in claim 22, further comprising: a reflection diffusion plate which is placed under the light-emitting device units and reflects and scatters incident light. The device of claim 22, further comprising: at least one of a brightness enhancement layer (BEF) to improve the direction of light transmitted through the first transmissive diffusion plate and a polarization enhancement layer to improve polarization efficiency. 25. A backlight unit to be used in a liquid crystal display (LCD) device, comprising: a base plate; and a plurality of rows of luminous units disposed on the base plate to emit light, the plurality of rows comprising: outer rows disposed at opposite ends of the base plate, comprising luminous units spaced apart at smaller gaps at the ends thereof then in the middle thereof, and inner rows placed between the outer rows on the base plate comprising these light emitting units spaced apart with equal gaps at the ends and in the middle thereof. The backlight unit of claim 25, wherein the outer rows comprise an equal number of light emitting units as the inner rows. 25 The backlight unit of claim 25, wherein the outer rows comprise a greater number of light emitting units than the inner rows. The background releasing unit of claim 27, wherein the light emitting units disposed in the center of the outer rows are spaced apart with a spaced gap as the light emitting units of the inner rows. 5 The background relationship unit of claim 25, wherein the plurality of rows are spaced apart with spaced gaps. 30. A background conditioner to be used with a liquid crystal display (LCD) device, comprising: a base plate; and a plurality of rows of securing units disposed on the base plate for radiating light and arranged so that outer rows of securing units with smaller spacings are spaced apart from each other than the inner rows of securing units. The backlight unit of claim 30, wherein the illuminating units in each of the plurality of rows with spaced spacings are spaced apart. 20 32. A background conditioner to be used with a liquid crystal display (LCD) device, comprising: a base plate; and light-emitting units arranged on the base plate to be separated by different size gaps in at least one of a longitudinal direction of the base plate and width direction of the base plate according to a position of each of the adhering units on the base plate. 33. Backlight unit according to claim 32, wherein the light-emitting units that are placed near corners of the base plate are separated by smaller gaps in one of the longitudinal and width directions, than the light-emitting units that are placed near the center of the base plate. A liquid crystal display device comprising: a liquid crystal display; and a backlight unit for radiating light toward the liquid crystal screen, and comprising: a base plate, a first plurality of light emitting device units disposed in a first surface unit of the base plate, and a second plurality of light emitting device units placed in a second surface light unit unit of the base plate which is the same size as the first surface unit. The liquid crystal display device of claim 34, further comprising: an optical plate disposed between the liquid crystal display and the backlight unit and having a plurality of reflection mirrors, wherein each of the luminous device units comprises a reflection surface to reflect a first light beam, has a first refraction surface to break a second light beam, and a second refraction surface to break a third light beam in a direction substantially perpendicular to a central axis of the base plate. A liquid crystal display device comprising: a liquid crystal display; and a backlight unit for emitting light toward the liquid crystal screen, which has: a base plate, a first unit having first luminous device units disposed in a first area of the base plate to emit light with a first brightness, and a second unit which has second luminous device units placed in a second area of the base plate to emit light with a second brightness, the first area being different from the second area and the first area having the same dimensions as the second area. A backlight unit comprising: a base plate; A plurality of first luminous device units disposed in a first area of the base plate; and a plurality of second light emitting device units disposed in a second area of the base plate, wherein the number of first light emitting device units is equal to the number of second light emitting device units and the first area having a different size than the second area. 25