KR102129437B1 - backlight unit and liquid crystal display module including the same - Google Patents

Abstract

The backlight unit of the present invention includes a reflective sheet; A light guide plate positioned on the reflective sheet and including a plurality of donut dot patterns on a rear surface; A plurality of optical sheets positioned on the light guide plate; And a light emitting diode assembly positioned on one side of the light guide plate.

Description

Backlight unit and liquid crystal display module including the same}

The present invention relates to a liquid crystal display device, and more particularly, to a backlight unit having improved luminance and a liquid crystal display module including the same.

A liquid crystal display (LCD) device includes a liquid crystal layer formed between two substrates and two substrates, and transmits light by controlling the arrangement of liquid crystal molecules in the liquid crystal layer to display an image.

In general, a liquid crystal display device includes a plurality of pixels arranged in a matrix, and each pixel includes a thin film transistor, a pixel electrode, and a common electrode. By applying voltage to the pixel electrode and the common electrode of each pixel, an electric field is generated between the pixel electrode and the common electrode, and the liquid crystal molecules of the liquid crystal layer are rearranged by the generated electric field, thereby changing the transmittance of the liquid crystal layer. Therefore, by controlling the voltage applied to the pixel electrode and the common electrode of the liquid crystal display, the transmittance of the liquid crystal layer of each pixel can be adjusted to have a value corresponding to the image signal, and as a result, the liquid crystal display displays an image.

Since such a liquid crystal display device is not a self-luminous device, light must be supplied separately. Accordingly, the liquid crystal display device includes a liquid crystal panel displaying an image and a backlight unit supplying light to the liquid crystal panel.

The backlight unit includes a light source, and a fluorescent lamp such as a cold cathode fluorescent lamp (CCFL) or an external electrode fluorescent lamp (EEFL) has been used as a light source of the backlight unit.

The backlight unit may be divided into a direct type and an edge type according to the path of light emitted from the lamp. The direct type backlight unit is a method in which a plurality of lamps are disposed under a liquid crystal panel to directly supply light emitted from the lamp to the liquid crystal panel. The side type backlight unit is a method of indirectly supplying light emitted from the lamp to the liquid crystal panel by using refraction and reflection in the light guide plate by arranging the light guide plate under the liquid crystal panel and placing the lamp on at least one side of the light guide plate.

Recently, in accordance with the trend of thinner and lighter weight of the liquid crystal display device, the side type backlight unit is widely used, and the light source of the backlight unit also has a light emitting diode (LED) lamp, which has advantages in power consumption, weight, brightness, and the like. Is replacing it.

1 is a cross-sectional view schematically showing a liquid crystal display module including a conventional side type backlight unit.

As shown in FIG. 1, the conventional liquid crystal display module includes a liquid crystal panel 10, a backlight unit 20, a support main 30, a top cover 40, and a bottom cover 50.

The liquid crystal panel 10 includes a lower substrate 10a and an upper substrate 10b, and a liquid crystal layer (not shown) is positioned between the two substrates 10a and 10b. The lower polarizing plate 12a is disposed under the lower substrate 10a, and the upper polarizing plate 12b is disposed on the upper substrate 10b.

A driving unit (not shown) including a driver integrated circuit (driver IC) is connected to one side of the liquid crystal panel 10 to signal a plurality of pixels (not shown) inside the liquid crystal panel 10. To supply.

The backlight unit 20 is positioned under the liquid crystal panel 10, and the backlight unit 20 includes a reflective sheet 22 and a light guide plate 24 sequentially arranged from the bottom and a plurality of optical sheets 26. . On the other hand, a light emitting diode (LED) assembly 28 is disposed on one side of the light guide plate 24 as a light source. The LED assembly 28 includes an LED printed circuit board 28a and an LED 28b.

The support main 30 surrounds the side surfaces of the liquid crystal panel 10 and the backlight unit 20, and the top cover 40 on the front of the liquid crystal panel 10 and the bottom cover 50 on the back of the backlight unit 20. They are combined together to form a liquid crystal display module.

In this side type backlight unit 20, as shown in FIG. 2, in order to uniformly provide light from the LED 28b located on one side of the light guide plate 24 to the liquid crystal panel 10, the light guide plate 24 ), a plurality of circular dot patterns 24a are formed on the back surface. Here, FIG. 2 is a view showing the rear surface of the light guide plate of the conventional side type backlight unit.

However, as the thickness of the light guide plate 24 becomes thin in accordance with the trend of thinner and lighter weight of the liquid crystal display device, the light from the LED 28b is not uniformly provided to the liquid crystal panel 10, and thus the stain is recognized in appearance. There is a limit to raising the luminance.

An object of the present invention is to provide a backlight unit capable of preventing stains and improving luminance and a liquid crystal display module including the same.

In order to achieve the above object, the backlight unit of the present invention includes a reflective sheet; A light guide plate positioned on the reflective sheet and including a plurality of donut dot patterns on a rear surface; A plurality of optical sheets positioned on the light guide plate; And a light emitting diode assembly positioned on one side of the light guide plate.

The donut-shaped dot pattern has a circular shape.

Alternatively, the donut-shaped dot pattern is elliptical. At this time, the long axis of the donut-shaped dot pattern is parallel to the longitudinal direction of the light emitting diode assembly.

The light guide plate is divided into first to n-th regions (n is a natural number) between the one side and the other side corresponding to the one side, and from the first region adjacent to the one side to the n region adjacent to the other side Increasingly, the size of the donut dot pattern increases.

The size of the donut dot pattern is the same in each of the first to n-th regions.

The donut-shaped dot patterns of the first to n-th regions have the same pitch.

The liquid crystal display module according to the present invention includes a reflective sheet, a light guide plate positioned on the reflective sheet and including a plurality of donut-shaped dot patterns on the rear surface, a plurality of optical sheets positioned on the light guide plate, and the light guide plate. A backlight unit including a light emitting diode assembly positioned on one side; A liquid crystal panel positioned on the backlight unit and displaying an image; A support main surrounding side surfaces of the liquid crystal panel and the backlight unit; A top cover on the front of the liquid crystal panel; And it includes a bottom cover on the back of the backlight unit.

In the present invention, by forming a donut-shaped dot pattern on the rear surface of the light guide plate, and increasing the portion scattering light compared to the circular dot pattern, it is possible to prevent stains and increase the brightness of the backlight unit.

Further, by making the donut-shaped dot pattern an elliptical shape, the luminance of the backlight unit can be further increased.

1 is a cross-sectional view schematically showing a liquid crystal display module including a conventional side-type backlight unit.
2 is a view showing a rear surface of a light guide plate of a conventional side type backlight unit.
3 is an exploded perspective view schematically showing a liquid crystal display module according to an embodiment of the present invention.
4A is a plan view showing a rear surface of a light guide plate according to an embodiment of the present invention, and FIG. 4B is a cross-sectional view showing a cross section of a light guide plate according to an embodiment of the present invention.
5A to 5C are enlarged views of portions of the first to third regions of the light guide plate according to the exemplary embodiment of the present invention.
6A and 6B are graphs showing luminance of the light guide plate with respect to a viewing angle according to a pattern shape on the back surface of the light guide plate.
7 is a plan view showing a rear surface of a light guide plate according to another embodiment of the present invention.

Hereinafter, a liquid crystal display module according to an exemplary embodiment of the present invention will be described in detail with reference to the accompanying drawings.

3 is an exploded perspective view schematically showing a liquid crystal display module according to an embodiment of the present invention.

As shown in FIG. 3, the liquid crystal display module of the present invention includes a liquid crystal panel 110 and a backlight unit 120, a support main 130, a top cover 140, and a bottom cover 150.

The liquid crystal panel 110 includes a lower first substrate 112 and an upper second substrate 114, and a liquid crystal layer (not shown) is positioned between the two substrates 112 and 114.

Although not illustrated, the first substrate 112 includes a plurality of gate wirings and data wirings on the inner surface, and the gate wirings and data wirings intersect to define a plurality of pixel regions. Thin film transistors and pixel electrodes connected to the gate wiring and the data wiring are positioned in each pixel region. The first substrate 112 is referred to as an array substrate.

Further, although not shown, the second substrate 114 includes a black matrix, a color filter layer, and a common electrode on the inner surface. The black matrix has an opening corresponding to the pixel area, and red, green, and blue color filter patterns of the color filter layer are sequentially positioned corresponding to the opening of the black matrix. The common electrode covers the black matrix and the color filter layer, and the common electrode forms a liquid crystal capacitor together with the pixel electrode. The second substrate 114 is referred to as a color filter substrate.

Meanwhile, the common electrode may be formed in the pixel region of the first substrate 114 together with the pixel electrode, and in this case, the common electrode and the pixel electrode may be alternately positioned in a pattern such as a rod shape.

Here, the area of the second substrate 114 is smaller than that of the first substrate 112, and the two adjacent edges of the first substrate 112 are partially exposed.

A driver integrated circuit (driver IC) 116 is connected to the exposed first substrate 112, and the driver integrated circuit 116 is connected to a printed circuit board (PCB) 117.

A first polarizing plate (not shown) and a second polarizing plate (not shown) are attached to the outside of the liquid crystal panel 110, that is, the lower portion of the first substrate 112 and the upper portion of the second substrate 114, respectively. . The first polarizing plate and the second polarizing plate transmit only linearly polarized light parallel to each light transmission axis. The optical transmission axis of the first polarizing plate and the optical transmission axis of the second polarizing plate are arranged perpendicular to each other.

The backlight unit 120 is positioned under the liquid crystal panel 110 to supply light to the liquid crystal panel 110. The backlight unit 120 includes a reflective sheet 122, a light guide plate 124, an optical sheet 126, and a light emitting diode (LED) assembly 128.

The LED assembly 128 includes an LED printed circuit board 128a and a plurality of LEDs 128b. The LED 128b is mounted on one surface of the LED printed circuit board 128a, for example, on the lower surface in the drawing, and is positioned at regular intervals along the length direction of the LED printed circuit board 128a. Here, the structure in which the LEDs 128b are arranged in one line is presented, but the LEDs 128b may be arranged in two lines.

The LED assembly 128 is disposed on one side of the light guide plate 124 and is positioned corresponding to the short side of the light guide plate 124. The light guide plate 124 serves to realize a surface light source by transmitting the light emitted from each of the plurality of LEDs 128a into the front through one side of the light guide plate 124 to the front side through reflection and refraction. do. A plurality of donut-shaped dot patterns 125 are formed on the rear surface of the light guide plate 124. Here, one side of the light guide plate 124 to which light is incident is referred to as an incident light surface, and a surface corresponding to the incident light surface is referred to as an incoming light surface.

The reflective sheet 122 is positioned under the light guide plate 124 and reflects light passing through the rear surface of the light guide plate 124 toward the liquid crystal panel 110, thereby improving light luminance.

A plurality of optical sheets 126 are positioned on the light guide plate 124, and the optical sheets 126 may include first to third optical sheets 126a, 126b, and 126c. Here, the first to third optical sheets 126a, 126b, and 126c diffuse or collect light from the light guide plate 124, and the first optical sheet 126a may be a sheet having a light diffusion function, and the second And the third optical sheets 126b and 126c may be sheets having a light collecting function.

Subsequently, a side of the backlight unit 120 is surrounded by a square frame-shaped support main 130, and an edge of the liquid crystal panel 110 is placed on the support main 130.

The top cover 140 has a cross section including a front side and a side surface and has an'A' shape, and has an opening in the center of the front side, covering the front edge and side of the liquid crystal panel 110.

The bottom cover 150 is located on the rear surface of the backlight unit 120 and is combined with the top cover 140 via the support main 130 to form a liquid crystal display module.

Here, the top cover 140 may be referred to as a case top or top case or top frame, the support main 130 may also be referred to as a main support or main frame, and the bottom cover 150 may be referred to as a cover bottom or bottom case or bottom. It is also called a frame.

4A is a plan view showing a rear surface of a light guide plate according to an embodiment of the present invention, and FIG. 4B is a cross-sectional view showing a cross section of a light guide plate according to an embodiment of the present invention.

4A and 4B, a plurality of donut dot patterns 125 are formed on the rear surface of the light guide plate 124. The donut-shaped dot pattern 125 has a substantially circular shape, and increases in size from the light incident surface 124a of the light guide plate 124 to the light entering surface 124b.

In one example, the light guide plate 124 may be divided into three regions A1, A2, and A3 along the first direction between the light incident surface 124a and the light incident surface 124b, the first adjacent to the light incident surface 124a The size of the donut dot pattern 125a in the area A1 is the smallest, the size of the donut dot pattern 125c in the third area A3 adjacent to the carry-in surface 124b is the largest, and the center second area The size of the donut dot pattern 125c in (A2) is between the donut dot patterns 125a and 125c in the first area A1 and the third area A3. At this time, the donut-shaped dot patterns 125 in each of the first to third regions A1, A2, and A3 may have the same size. Accordingly, the maximum thickness of the light guide plate 124 including the donut-shaped dot pattern 125a adjacent to the light incident surface 124a is the maximum thickness of the light guide plate 124 including the donut-shaped dot pattern 125c adjacent to the incoming light surface 124b. It may be less than the maximum thickness. Meanwhile, as shown in FIG. 4A, the donut-shaped dot pattern 125 includes first, second, and third patterns 1251, 1252, and 1253 sequentially positioned along a first direction, and a second pattern (1252) has a different size from the first pattern 1251, and may have the same size as the third pattern (1253). In addition, as illustrated in FIG. 4B, the maximum thickness of the light guide plate 124 including the second pattern 1252 is different from the maximum thickness of the light guide plate 124 including the first pattern 1251 and the third pattern 1253 ) May be the same as the maximum thickness of the light guide plate 124.

5A to 5C are enlarged views of portions of the first to third regions of the light guide plate according to the exemplary embodiment of the present invention, respectively, and correspond to regions B1, B2, and B3 of FIG. 4A, respectively.

5A to 5C, the donut dot patterns 125a, 125b, and 125c of each of the first to third regions B1, B2, and B3 are repeatedly arranged corresponding to square vertices and center points, respectively. do. Therefore, they are spaced at the same distance along the first direction and the second direction perpendicular thereto.

Here, the donut dot patterns 125a, 125b, and 125c of the first to third regions B1, B2, and B3 have different sizes, but their pitches d1, d2, d3, that is, adjacent donut dots The distances between the centers of the patterns 125a, 125b, and 125c are all the same.

These donut-shaped dot patterns 125a, 125b, and 125c may increase the circumferential length compared to a conventional circular dot pattern to improve the brightness of the backlight unit.

More specifically, when the area of the pattern formed on the rear surface of the light guide plate is the same, the luminance of the backlight unit increases as the circumferential length of the pattern increases. Accordingly, in the present invention, the portion having the inner circumferential surface and the outer circumferential surface having the shape of the pattern as a donut shape is added to scattering light. Therefore, compared to the light guide plate having a circular dot pattern, the brightness of the backlight unit can be improved.

At this time, by reducing the size and pitch of the pattern, it is possible to further increase the luminance of the backlight unit by increasing the circumferential length of the pattern within the same area.

6A and 6B are graphs showing the luminance of the light guide plate with respect to the viewing angle according to the pattern shape of the back surface of the light guide plate, FIG. 6A shows the luminance with respect to the vertical viewing angle, and FIG. Here, the solid line is the luminance of the light guide plate having a circular dot pattern, and the dotted line is the luminance of the light guide plate having a donut-shaped dot pattern.

As shown in FIGS. 6A and 6B, the brightness of the light guide plate varies depending on the vertical and horizontal viewing angles, and the brightness of the backlight unit is proportional to the total amount of light passing through the light guide plate, that is, the area of the graph.

Here, when the graph area of the light guide plate having the donut-type dot pattern is larger than the graph area of the light guide plate having the circular dot pattern, and the total luminance of the light guide plate having the circular dot pattern is 100.0%, the total of the light guide plates having the donut-type dot pattern The luminance is 111.2%, and the total luminance of the light guide plate having a donut dot pattern is about 11.2% higher than the total luminance of the light guide plate having a circular dot pattern.

Therefore, it can be seen that by using a light guide plate having a donut-shaped dot pattern, the luminance of the backlight unit can be improved compared to a light guide plate having a circular dot pattern.

The light guide plate having such a donut-shaped dot pattern is formed by forming a negative pattern on the surface of the base substrate by processing the base substrate using a laser having two peaks, and then applying a resin on the base substrate and curing, followed by curing. It can be formed by separating the resin from the base substrate.

7 is a plan view showing a rear surface of a light guide plate according to another embodiment of the present invention.

As shown in FIG. 7, the light guide plate 224 according to another embodiment of the present invention includes a plurality of donut-shaped dot patterns 225 on the rear surface. At this time, the donut-shaped dot pattern 225 has an oval shape, and the long axis of the donut-shaped dot pattern 225 is preferably parallel to the longitudinal direction in which LEDs (not shown) are arranged. When the donut-shaped dot pattern 225 has an elliptical shape, since the circumferential length is increased more than the circular shape when the area is the same, the luminance of the backlight unit can be further increased compared to the circular shape. Here, as shown, the distance between adjacent donut-shaped dot patterns 225 along the long side direction of the light guide plate 224 is greater than the distance between adjacent donut-shaped dot patterns 225 along the short side direction of the light guide plate 224.

It is preferable that the size of the donut-shaped dot pattern 225 increases from the light incident surface 224a of the light guide plate 224 to the light incident surface 224b.

In one example, the light guide plate 224 may be divided into three regions A11, A12, and A13 along the first direction between the light incident surface 224a and the light incident surface 224b, the first adjacent to the light incident surface 224a The size of the donut dot pattern 225a in the area A11 is the smallest, the size of the donut dot pattern 225c in the third area A13 adjacent to the carry-in surface 224b is the largest, and the center second area The size of the donut dot pattern 225c in (A12) is between the donut dot patterns 225a and 225c in the first area A11 and the third area A13. At this time, the donut-shaped dot patterns 125 in each of the first to third regions A11, A12, and A13 may have the same size. Accordingly, as shown in FIG. 7, the donut-shaped dot pattern 225 includes first, second, and third patterns 2251, 2252, and 2253 sequentially positioned along the first direction, and the second The pattern 2252 has a different size from the first pattern 2251 and may have the same size as the third pattern 2231.

The present invention is not limited to the above-described embodiments, and various changes and modifications are possible without departing from the spirit of the present invention.

110: liquid crystal panel 112: first substrate
114: second substrate 116: driving integrated circuit
117: Printed circuit board 120: backlight unit
122: reflective sheet 124: light guide plate
125: donut dot pattern 126: optical sheet
128: LED assembly 128a: LED printed circuit board
128b: LED 130: support main
140: top cover 150: bottom cover

Claims (10)

A reflective sheet;
A light guide plate positioned on the reflective sheet and including a plurality of donut dot patterns on a rear surface;
A plurality of optical sheets positioned on the light guide plate;
A light emitting diode assembly positioned on one side surface that is an incident surface of the light guide plate
It includes,
The plurality of donut-shaped dot patterns include first, second, and third patterns sequentially positioned along a first direction, and the second pattern has a different size from the first pattern and is the same as the third pattern. Has a size,
In the light guide plate, a maximum thickness including the donut-shaped dot pattern adjacent to the light incident surface is smaller than a maximum thickness including the donut-shaped dot pattern adjacent to the incoming light surface,
The maximum thickness of the light guide plate including the second pattern is different from the maximum thickness of the light guide plate including the first pattern and the same backlight unit as the maximum thickness of the light guide plate including the third pattern.
According to claim 1,
The donut-shaped dot pattern is a backlight unit, characterized in that the circular shape.
According to claim 1,
The donut-shaped dot pattern is an oval-shaped backlight unit.
According to claim 1,
The long axis of the donut-shaped dot pattern is a backlight unit, characterized in that parallel to the longitudinal direction of the light emitting diode assembly.
According to claim 1,
The light guide plate is divided into first to n-th regions (n is a natural number) along the first direction between the one side and the other side corresponding to the one side, and the other side in the first region adjacent to the one side. The size of the donut dot pattern for each region increases as the nth region adjacent to the nth region increases, and the size of the donut dot pattern in each of the first to nth regions is the same.
delete The method of claim 5,
The pitch of the donut dot pattern of the first to n-th regions is the same, characterized in that the backlight unit.
The backlight unit according to any one of claims 1 to 5 and 7;
A liquid crystal panel positioned on the backlight unit and displaying an image;
A support main surrounding side surfaces of the liquid crystal panel and the backlight unit;
A top cover on the front of the liquid crystal panel; And
Bottom cover on the back of the backlight unit
A liquid crystal display module comprising a. According to claim 1,
The donut-shaped dot pattern adjacent to the second direction perpendicular to the first direction has the same size.
According to claim 1,
The distance between the adjacent donut-shaped dot patterns along the long side direction of the light guide plate is greater than the distance between the adjacent donut-shaped dot patterns along the short side direction of the light guide plate.

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