KR20070108991A - Backlight assembly and liquid crystal display using the same - Google Patents

Abstract

A back light assembly and a liquid crystal display device using the same are provided to prevent condensation of the light generated from a light emitting diode in an incident side adjacent to the light emitting diode by forming at least one cutting part in a side part of an optical sheet. A back light assembly comprises a light emitting diode unit(149), a reflective plate(141), a light guide plate(142), and an optical sheet(143). The light emitting diode unit includes at least one light emitting diode(145) emitting the light, and a light emitting diode printed circuit board(148) having a driving circuit driving each light emitting diode. The reflective plate reflects the light generated from the light emitting diode unit. The light guide plate arranged in a side part of the light emitting unit provides the light toward a front side of a liquid crystal panel. The optical sheet installed on the light guide plate diffuses and condenses the light transferred from the light guide plate. At least one cutting part(143a) which is a partially cut part of the optical sheet is formed in a side part of the optical sheet adjacent to the light emitting diode.

Description

Backlight assembly and liquid crystal display using the same

1 is a view schematically showing a conventional edge type backlight assembly.

2 is a schematic view of a conventional direct backlight assembly.

3 is an exploded perspective view schematically illustrating a structure of a liquid crystal display according to an exemplary embodiment of the present invention.

4A is a view for explaining the progress of light when the light emitted from the light emitting diode is incident into a single medium.

4B is a view for explaining the progress of light when the light emitted from the light emitting diode is incident into the light guide plate, which is a different medium.

5 is an enlarged view illustrating a backlight assembly according to an embodiment of the present invention.

6 is a cross-sectional view illustrating a liquid crystal display using the backlight assembly according to an exemplary embodiment of the present invention.

FIG. 7 is an enlarged cross-sectional view illustrating an incident part of the backlight assembly in the liquid crystal display illustrated in FIG. 6.

8 is an enlarged perspective view of a backlight assembly of a liquid crystal display according to another exemplary embodiment of the present invention.

(Explanation of symbols for the main parts of the drawing)

100; liquid crystal panel 120, 130; drive circuit unit

Printed circuit board (122,132); tape carrier package

140; backlight assembly 141; reflector

142; light guide plate 143,843; optical sheet

143a, 843a; cutting portion 145; light emitting diode

147; holder 148; light emitting diode printed circuit board

149; light emitting diode unit 150; mold frame

151; upper case 152; lower case

The present invention relates to a liquid crystal display, and more particularly, to a backlight assembly using a light emitting diode (LED) as a light source and a liquid crystal display using the same.

In general, a liquid crystal display (LCD) is a display device that displays a desired image by individually supplying data signals according to image information to a plurality of pixels arranged in a matrix to adjust light transmittance of the pixels. .

Such a liquid crystal display device inevitably needs a backlight assembly for supplying light from its rear surface such that a difference in light transmittance is expressed to the outside.

Recently, an active matrix type in which pixels, which are basic units of image expression, are arranged in a matrix on a liquid crystal panel and individually controlled by using switching elements such as thin film transistors (TFTs). This color reproduction and video display is widely used, and in this case, the backlight assembly includes a cold cathode fluorescent lamp (CCFL) or an exterior electrode fluorescent lamp (EEFL) as a light source that emits light. It is used.

At this time, it can be divided into an edge type or a direct type according to the position of the lamp. The edge type of the electron is provided on the back side of the liquid crystal panel with a separate light guide plate (LGP) and one side of the light guide plate. Light is supplied to the liquid crystal panel by refracting the light incident from the light source, and the latter direct type supplies light directly to the front surface of the liquid crystal panel by arranging the light source on the back of the liquid crystal panel.

Hereinafter, the structures of the conventional edge type backlight assembly and the direct type backlight assembly will be described in detail.

1 is a view schematically showing a conventional edge-type backlight assembly, the conventional edge-type backlight assembly 10 is a light guide plate 11 disposed on the back of the liquid crystal panel (not shown) and the light guide plate 11 Lamp 13 disposed on the side, Reflective plate 15 disposed on the back of the light guide plate 11, Lamp holder (not shown) for fixing the lamp 13 to the side of the light guide plate 11, Lamp reflector 17 And a wiring 19 for applying power to the lamp 13.

The light generated by the lamp 13 is incident on the side surface of the light guide plate 11 of a transparent material, and the reflector plate 15 disposed on the rear surface of the light guide plate 11 transmits light transmitted to the rear surface of the light guide plate 11. Reflected to the front of the panel reduces light loss and improves uniformity.

Therefore, the light guide plate 11 transmits the light emitted from the lamp 13 together with the reflecting plate 15 to the front surface of the liquid crystal panel.

2 is a schematic view of a conventional direct backlight assembly.

The conventional direct backlight assembly 20 includes a plurality of lamps 21 disposed on a rear surface of a liquid crystal panel (not shown) and incident light onto the entire rear surface of the liquid crystal panel, and a rear surface of the plurality of lamps 21. Applying power to the reflector plate 23 disposed on the plurality of lamps 21, the diffuser plate 25 disposed on the plurality of lamps 21 to diffuse the light emitted from the lamps 21, and the plurality of lamps 21. For wirings 27.

As described above, the liquid crystal display device including the edge type or direct type backlight assemblies 10 and 20 mainly uses fluorescent lamps 13 and 21 as light sources, so that the power consumption of the light sources is high, the lifespan is short, and the brightness is high. Is not uniform and is relatively low in terms of high brightness and uniformity. In addition, since an inverter circuit for controlling each of the fluorescent lamps 13 and 21 is separately required, manufacturing costs are increased, and the area of the lamp occupied by the backlight assembly is relatively large, which makes it difficult to miniaturize the backlight assembly. .

Recently, a backlight assembly and a liquid crystal display using a light emitting diode (LED) as a light source instead of the conventional fluorescent lamps 13 and 21 have been disclosed.

However, the light emitted from the light emitting diode has a constant emission angle, and a hot spot phenomenon occurs in which portions of the emission angle overlap each other. This hot spot phenomenon has a problem of causing luminance unevenness and poor appearance.

Accordingly, an object of the present invention is to provide a backlight assembly that can prevent a hot spot problem that occurs when a light emitting diode is used as a light source.

Another object of the present invention is to provide a liquid crystal display device using the above-described backlight assembly.

Further technical problems to be achieved by the present invention are not limited to the above-mentioned technical problems, and other technical problems not mentioned above are clearly understood by those skilled in the art from the following description. It can be understood.

According to an aspect of the present invention, there is provided a backlight assembly comprising: at least one light emitting diode emitting light, a light guide plate disposed on the light emitting diode side, and a light guide plate disposed on the light guide plate; It includes an optical sheet having at least one cut portion partially cut on the adjacent side.

In this case, the cutting portion is characterized in that it is formed to face each position where the light emitting diode is disposed.

In addition, the cutting portion is characterized in that the horizontal cross-section is any one of a square, semi-circle, triangular, trapezoidal shape. The cutting parts may be formed to be spaced apart from each other, or contacted adjacent to each other.

In addition, the cutting portion is characterized in that formed on both sides facing each other in the optical sheet.

In addition, the light emitting diode is characterized in that disposed on both sides of the light guide plate.

In addition, the light emitting diode is preferably a device that implements any one color of red, green, blue, white.

In addition, it is preferable to further include a light shielding film positioned on the light emitting diode and the light guide plate and partially overlapping the optical sheet to block light emitted from the light emitting diode.

The light emitting diode may further include a light emitting diode printed circuit board provided on an outer side of the light emitting diode and mounted with driving elements for driving the light emitting diode.

On the other hand, the liquid crystal display device according to an embodiment of the present invention for achieving the another technical problem, a liquid crystal panel including an array substrate and a color filter substrate, a liquid crystal layer formed between the array substrate and the color filter substrate, and the liquid crystal At least one light emitting diode disposed at a rear side of the panel to emit light, a light guide plate disposed at the side of the light emitting diode, and at least a portion of the light guide plate disposed above the light guide plate and partially cut to a side adjacent to the light emitting diode. A backlight assembly including an optical sheet having at least one cut portion formed therein, and a case protecting the liquid crystal panel and the backlight assembly.

In this case, in the backlight assembly, the cutting portion is formed to face each position where the light emitting diode is disposed.

In addition, in the backlight assembly, the cut portion is characterized in that the horizontal cross-section is any one of a square, semi-circle, triangular, trapezoidal shape. The cutting parts may be formed to be spaced apart from each other, or contacted adjacent to each other.

In addition, in the backlight assembly, the cutting parts may be formed on both sides of the optical sheet facing each other.

In addition, the light emitting diode is characterized in that disposed on both sides of the light guide plate.

In addition, the light emitting diode is characterized in that the device for implementing any one of red, green, blue, white color.

The backlight assembly may further include a light blocking film positioned on the light emitting diode and the light guide plate and partially disposed to overlap the optical sheet to block light emitted from the light emitting diode.

The backlight assembly may further include a light emitting diode printed circuit board provided on the outside of the light emitting diode to surround the light emitting diode and mounted with driving elements for driving the light emitting diode.

Specific details of other embodiments are included in the detailed description and the drawings. Advantages and features of the present invention and methods for achieving them will be apparent with reference to the embodiments described below in detail with the accompanying drawings. Like reference numerals refer to like elements throughout.

Hereinafter, a backlight assembly and a liquid crystal display according to exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

3 is an exploded perspective view schematically illustrating a structure of a liquid crystal display according to an exemplary embodiment of the present invention, and illustrates a liquid crystal display using a light emitting diode (LED) as a light source.

Referring to FIG. 3, a liquid crystal display according to an exemplary embodiment of the present invention may include a liquid crystal panel 100 in which a plurality of pixels (not shown) are arranged in a matrix form, and driving to drive pixels of the liquid crystal panel 100. The circuit unit 120 and 130, a backlight assembly 140 that provides a light source on the rear surface of the liquid crystal panel 100, and cases 151 and 152 for protecting them are included.

Although not shown in the drawings, the liquid crystal panel 100 is composed of an array substrate and a color filter substrate bonded to each other to maintain a uniform cell gap, and a liquid crystal layer formed between the array substrate and the color filter substrate. .

The driving circuits 120 and 130 are printed circuit boards on which various elements (not shown) and tape carrier packages (TCP) 122 and 132 for driving the liquid crystal panel 100 are mounted, such as a timing controller. (Printed Circuit Board; PCB) 121,131.

The backlight assembly 140 may include at least one light emitting diode 145 emitting light, a reflecting plate 141 reflecting light generated from the light emitting diode 145, and a light guide plate providing light to the front of the liquid crystal panel 100. 142 and an optical sheet 143 installed on the light guide plate 142 to diffuse and collect light transmitted from the light guide plate 142.

The light emitting diode 145 has a longer lifespan than a conventional cold cathode fluorescent lamp, and consumes only 20% of the power of a conventional product, and is advantageous in thinning the backlight assembly and improving the internal area because no additional equipment such as an inverter is required. .

In the liquid crystal display device according to the exemplary embodiment, the liquid crystal panel 100 and the backlight assembly 140 are stacked on the mold frame 150 to form side surfaces of the liquid crystal panel 100 and the backlight assembly 140. The mold frame 150 is supported by the mold frame 150, and the mold frame 150 is assembled into an assembly by coupling the upper case 151 and the lower case 152 using screws or the like.

In this case, when the light emitting diode 145 is used as a light source as described above, a light section and a dark section on the incidence side where the light emitting diode 145 is disposed according to the point light source characteristics of the light emitting diode 145. This alternate hot spot phenomenon occurs.

That is, light generated from the light emitting diode 145, which is a point light source, is transmitted to the light guide plate 142 with a constant emission angle, and the light guide plate 142 uniformly distributes the light of the incident light emitting diode 145 as a whole. The non-ideal light guide plate 142 is a hot spot phenomenon that appears relatively bright near the light source of the light emitting diode 145.

FIG. 4A is a view illustrating a process of light when light emitted from a light emitting diode is incident into a single medium, and FIG. 4B is a process of light when light emitted from a light emitting diode is incident into light guide plates of different media. A diagram for explaining.

For reference, FIGS. 4A and 4B illustrate radiation angles at which light of the light emitting diode 145, which is a point light source, travels when viewed from the top of the liquid crystal panel.

As shown in FIG. 4A, the light of the light emitting diode 145 in a single medium such as air maintains the emission angle a of about 110 degrees, but as shown in FIG. 4B, the light emitting diode 145 is shown. When the light exiting from the light guide plate 142 passes through the light guide plate 142, the radiation angle a 'is reduced to about 66.6 degrees. This is because light is transmitted from the small medium (I) to the light guide plate 142 which is the dense medium (II). When the radiation angle a 'is decreased, the light emitted from the light emitting diode 145 is separated from the light emitting diode 145. It is further biased at the side of the nearest light guide plate 142. Due to this phenomenon, a light spot in which the light does not proceed due to a constant radiation angle of the light emitting diode 145 appears relatively dark in the light guide plate 142, and a hot spot phenomenon in which the light-biased side is relatively bright appears. It will deepen.

In order to improve such a hot spot phenomenon, in this embodiment, by changing the shape of the optical sheet 143, the light on the incident side of the optical sheet 143 which is the main cause of the hot spot phenomenon is caused. Prevents condensing This will be described in detail with reference to the drawings.

5 is an enlarged view illustrating a backlight assembly according to an embodiment of the present invention, FIG. 6 is a cross-sectional view illustrating a liquid crystal display using the backlight assembly according to an embodiment of the present invention, and FIG. 6 is an enlarged cross-sectional view illustrating an incident part of the backlight assembly in the liquid crystal display shown in FIG. 6.

In this case, the same reference numerals are given to the same parts that play the same role as the above description in order to avoid duplicate description of the liquid crystal display.

First, referring to FIG. 5, the backlight assembly 140 according to an embodiment of the present invention includes a light emitting diode unit 149, a reflector 141 reflecting light generated from the light emitting diode unit 149, and light. The light guide plate 142, which is provided on the front surface of the liquid crystal panel 100 of FIG. 6, and the optical sheet 143 that is installed on the light guide plate 142 and diffuses and transmits light transmitted from the light guide plate 142.

The light emitting diode unit 149 includes at least one light emitting diode 145 for emitting light and a light emitting diode printed circuit board 148 mounted with a driving circuit for driving each light emitting diode 145, which is shown in the drawings. Although not illustrated, the light emitting diodes 145 may include a lead electrically connected to each of the light emitting diodes 145, and a holder 147 fixing the light emitting diodes 145.

In this case, each of the light emitting diodes 145 is arranged in a line along the side direction of the light guide plate 142 on one side or both sides of the light guide plate 142, and implements any one color of red, green, blue, and white. .

The LED printed circuit board 148 is in the form of a flexible printed circuit board (FPC), and is bent to surround the LED 145 on the outside of the LED 145 as shown.

In the present exemplary embodiment, a case in which a single chip is implemented to implement red, green, blue, or white in one light emitting diode 145 is described, but the present invention is not limited thereto. Each chip that implements green, blue, or white can be applied as a built-in type, and this type can not only realize a mixed color of red, green, blue, and white, but also improve brightness. There is this.

The reflective plate 141 is disposed on the rear surface of the light guide plate 142 to reflect the light transmitted to the rear surface of the light guide plate 142 to the front surface of the light guide plate 142 to reduce the loss of light and to transmit the light transmitted to the front surface of the light guide plate 142. It serves to improve the uniformity of.

The light guide plate 142 is disposed on the side of the light emitting diode unit 149 to transmit the light incident from the light emitting diode 145 and the reflecting plate 141 to the front side.

The optical sheet 143 is disposed on the light guide plate 142, and at least one cut part 143a is formed on a side adjacent to the light emitting plate 145 to emit from the light emitting diode 145. Prevents light from being collected.

The cutout 143a may be formed differently depending on whether the light emitting diode 145 is disposed, but in general, when the light emitting diode 145 is disposed on one side of the light guide plate 142, the cutout 143a may be formed by the optical sheet 143. When the light emitting diode 145 is disposed on both sides of the light guide plate 142, the cutouts 143a are formed on both sides of the optical sheet 143 facing each other.

In addition, the cutouts 143a are formed to face the positions where the light emitting diodes 145 are disposed, respectively, and as illustrated, the cut portions 143a are formed to have a horizontal cross section and are spaced apart from each other. In this case, the light emitting diodes 145 disposed at regular intervals may be spaced apart from each other by a pitch of the light emitting diodes 145.

In addition, the cutting portion 143a may be formed in a semicircular, triangular or trapezoidal shape in addition to the horizontal cross section.

In addition, the cutting parts 143a may be formed to be in contact with each other.

For example, as shown in FIG. 8, the cutout 843a may correspond to the number of the light emitting diodes 145 to correspond to the light emitting diodes 145 disposed on one or both sides of the light guide plate 142. The plurality of cut portions 843a have a semicircular shape, and the cut portions 843a are adjacent to each other. Accordingly, the optical sheet 843 has a wave pattern in which a semicircle is continuously formed on one side or both sides.

As another embodiment, when the horizontal section of the cutting portion is triangular and formed adjacent to each other, the optical sheet according to this has a sawtooth pattern in which a triangular shape is continuously formed on one side or both sides.

As described above, in the present embodiment, the structures of the optical sheets 143 and 843 are not limited to the above-described examples, and may be variously configured by combining various shapes (shapes of the horizontal cross section) and patterns, and the optical sheets configured as described above. Reference numerals 143 and 843 may be improved in terms of luminance than structures in which the entire side surface is cut.

Referring back to FIGS. 5 and 6, the optical sheet 143 typically has a diffusion sheet for diffusing light transmitted from the light guide plate 142 and a diffused light to uniformly distribute the light on the entire surface of the liquid crystal panel 100. And a protective sheet on top of the prism sheet.

As described above, the backlight assembly 140 according to the exemplary embodiment of the present invention has an optical sheet 143 having at least one cut portion 143a partially cut at the side adjacent to the light emitting diode 145. ), It is possible to prevent a hot spot phenomenon occurring around the light source of each light emitting diode 145.

In more detail, as shown in FIG. 7, the light generated from the light emitting diode 145 is incident to the side of the light guide plate 142 and passes through the light guide plate 142 and the optical sheet 143 to the front liquid crystal panel 100. At this time, at least one cut portion 143a is formed on a side surface of the optical sheet 143 adjacent to the light emitting diode 145, and the light incident from the light emitting diode 145 toward the incident side of the light guide plate 142 is incident. The light is scattered by the cutting portion 143a without passing through the optical sheet 143.

Therefore, it is possible to prevent the light from being collected at the incident side of the light guide plate 142.

Here, the incident side of the light guide plate 142 means a front end portion of the light guide plate 142 to which the light source of the light emitting diode 145 is incident. In addition, the dotted arrows shown in the drawing exemplarily show that light is not collected by the cutting portion 143a of the optical sheet 143.

On the other hand, the backlight assembly according to an embodiment of the present invention is disposed so as to overlap a portion of the light guide plate 142 and the optical sheet 143 on the light emitting diode 145 and the light guide plate 142 to block unnecessary light. 170 may be further configured. The light blocking film 170 may be a sheet type or an adhesive tape type.

Reference numeral 150 is a mold frame in which the liquid crystal panel 100 and the backlight assembly 140 are laminated and bonded, and reference numeral 160 is a polarizing plate.

Although embodiments of the present invention have been described above with reference to the accompanying drawings, those skilled in the art to which the present invention pertains may implement the present invention in other specific forms without changing the technical spirit or essential features thereof. You will understand that.

Therefore, since the embodiments described above are provided to completely inform the scope of the invention to those skilled in the art, it should be understood that they are exemplary in all respects and not limited. The invention is only defined by the scope of the claims.

The backlight assembly and the liquid crystal display using the same according to the embodiment of the present invention made as described above may improve the life of the liquid crystal display by using a light emitting diode as a light source.

In addition, by forming at least one cut portion on the side of the optical sheet to prevent the light generated from the light emitting diodes from being concentrated on the incident side adjacent to the light emitting diodes to prevent hot spots occurring around the light source, Furthermore, there is an effect of improving the appearance of the liquid crystal display device.

Claims (20)

At least one light emitting diode emitting light; A light guide plate disposed on the light emitting diode side; And And an optical sheet disposed on the light guide plate, the optical sheet having at least one cut portion partially cut on a side surface adjacent to the light emitting diode. The method of claim 1, The cutting portion And the light emitting diodes are formed to face each position where the light emitting diodes are disposed. The method of claim 1, The cutting unit has a horizontal cross section of the backlight assembly, characterized in that any one of a square, semi-circle, triangular, trapezoidal shape. The method of claim 3, And the cutting parts are formed to be spaced apart from each other. The method of claim 3, And the cut portions are formed to be in contact with each other adjacent to each other. The method of claim 1, The cutting portion Backlight assembly, characterized in that formed on both sides facing each other in the optical sheet. The method according to claim 1 or 6, The light emitting diode is backlight assembly, characterized in that disposed on both sides of the light guide plate. The method of claim 1, The light emitting diode is a backlight assembly, characterized in that the device for implementing any one of red, green, blue, white color. The method of claim 1, And a light shielding film disposed on the light emitting diode and the light guide plate, the light shielding film being partially overlapped with the optical sheet to block light emitted from the light emitting diode. The method of claim 1, And a light emitting diode printed circuit board provided on the outside of the light emitting diode to surround the light emitting diode and mounted with driving elements for driving the light emitting diode. A liquid crystal panel including an array substrate and a color filter substrate, and a liquid crystal layer formed between the array substrate and the color filter substrate; At least one light emitting diode disposed on a rear side of the liquid crystal panel to emit light, a light guide plate disposed on a side of the light emitting diode, and a portion of the light guide plate disposed on an upper side of the light guide plate and cut in a portion adjacent to the light emitting diode; A backlight assembly including an optical sheet having at least one cut portion formed thereon; And And a case protecting the liquid crystal panel and the backlight assembly. The method of claim 11, In the backlight assembly And the cutting part is formed to face each position where the light emitting diode is disposed. The method of claim 11, In the backlight assembly And the cutting portion has any one of horizontal, rectangular, semicircular, triangular, and trapezoidal shapes. The method of claim 13, And the cut portions are formed spaced apart from each other. The method of claim 13, And the cutting parts are formed to be in contact with each other adjacent to each other. The method of claim 11, In the backlight assembly And the cutting parts are formed on both side surfaces of the optical sheet facing each other. The method according to claim 11 or 16, And the light emitting diodes are disposed at both sides of the light guide plate. The method of claim 11, The light emitting diode is a liquid crystal display, characterized in that the device for implementing any one of red, green, blue, white color. The method of claim 11, The backlight assembly And a light shielding film positioned on the light emitting diode and the light guide plate and partially disposed to overlap the optical sheet to block light emitted from the light emitting diode. The method of claim 11, The backlight assembly And a light emitting diode printed circuit board provided on the outside of the light emitting diode to surround the light emitting diode and mounted with driving elements for driving the light emitting diode.

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