KR102399874B1 - Backlight unit and liquid crystal display device having the same - Google Patents

Abstract

The backlight unit of the present invention and the liquid crystal display having the same include a pad between the light guide plate and the LED array printed circuit board to maintain the space between the light guide plate and the LED array, and at the same time, the expansion direction of the light guide plate at the contact portion of the pad in contact with the light guide plate It is characterized in that it has a protrusion protruding side by side.
The protrusion of the pad makes linear or point contact with the light guide plate to minimize contact friction when the light guide plate is expanded, thereby providing an effect of minimizing thermal expansion noise.

Description

Backlight unit and liquid crystal display having same

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

In the recent information society, the importance of display devices as a visual information delivery medium is further emphasized, and in order to occupy a major position in the future, it is necessary to satisfy the requirements of low power consumption, thinness, light weight, and high quality.

Display devices are cathode ray tube (CRT) that emits light by itself, electro luminescence (EL), light emitting diode (LED), vacuum fluorescent display (VFD), electric field It can be divided into light-emitting types such as Field Emission Display (FED) and Plasma Display Panel (PDP) and non-emissive types such as Liquid Crystal Display (LCD) that do not emit light by themselves. .

A liquid crystal display device is a device that expresses an image by using the optical anisotropy of liquid crystal, and has been in the spotlight as a display device because it has excellent visibility compared to conventional CRTs, has lower average power consumption compared to CRTs of the same screen size, and also has less heat dissipation. there is.

Hereinafter, a general liquid crystal display device will be described.

In general, a liquid crystal display device can display a desired image by individually supplying data signals according to image information to pixels arranged in a matrix form, and adjusting light transmittance of the pixels.

Accordingly, the liquid crystal display includes a liquid crystal panel in which pixels are arranged in a matrix, a driving unit for driving the pixels, and a backlight unit for supplying light to the liquid crystal panel.

1 is an exploded perspective view schematically showing the structure of a general liquid crystal display device.

And, FIG. 2 is a cross-sectional view schematically showing a part of a structure of a general backlight unit.

1 and 2 , a typical liquid crystal display device has a liquid crystal panel 10 in which pixels are arranged in a matrix form to output an image, a driver (not shown) for driving the pixels, and a rear surface of the liquid crystal panel 10 . It is installed and consists of a backlight unit 40 that emits light over the entire surface of the liquid crystal panel 10 , and a lower cover 50 that accommodates and fixes the liquid crystal panel 10 and the backlight unit 40 .

The liquid crystal panel 10 has a color filter substrate 5 and an array substrate 15 bonded to each other to face each other to maintain a uniform cell gap, and a liquid crystal formed in a cell gap between the color filter substrate 5 and the array substrate 15 . It consists of layers (not shown).

Upper and lower polarizing plates (not shown) are attached to the outside of the liquid crystal panel 10 , respectively. At this time, the lower polarizing plate polarizes light passing through the backlight unit 40 , and the upper polarizing plate passes through the liquid crystal panel 10 . Polarizes light.

When describing the backlight unit 40 in detail, a light emitting diode (LED) assembly 30 for emitting light is installed on one side of a light guide plate 42 , and the A reflecting plate 41 is provided on the rear surface.

In this case, the LED assembly 30 includes an LED array 31 , an LED array printed circuit board (PCB) 33 for driving the LED array 31 , and a housing 32 .

Light emitted from the LED array 31 is incident on the side of the light guide plate 42 made of a transparent material, and the reflector 41 disposed on the rear surface of the light guide plate 42 transmits light transmitted through the rear surface of the light guide plate 42 to the light guide plate 42 . ) is reflected toward the optical sheets 43 on the upper surface to reduce light loss and improve uniformity.

The liquid crystal panel 10 including the color filter substrate 5 and the array substrate 15 is seated on the upper part of the backlight unit 40 configured as described above through the guide panel 45 , and the lower cover 50 is coupled to the lower part. This constitutes a liquid crystal display device.

At this time, the heat dissipation pad 35 is positioned between the LED array printed circuit board 33 and the housing 32 , and the contact prevention pin 60 for fixing includes the lower cover 50 , the housing 32 and the LED array printing. They all pass through the circuit board 33 in order and protrude toward the incident surface of the light guide plate 42 .

To this end, the lower cover 50, the housing 32, and the LED array printed circuit board 33 are formed with through-holes into which the fixing contact prevention pins 60 are inserted.

This fixing contact prevention pin 60 serves to fix the lower cover 50, the housing 32, and the LED array printed circuit board 33, and supports the light guide plate 42 while supporting the light guide plate 42 and the LED. It serves to prevent the arrays 31 from contacting each other.

However, since the contact prevention pin 60 for fixing must be fastened by forming through-holes in a plurality of parts, there is a disadvantage in that the process is complicated and the cost is increased.

Accordingly, a method of attaching a pad to the LED array printed circuit board 33 to maintain the distance from the LED array 31 while supporting the light guide plate 42 is used, but between the light guide plate 42 and the pad during thermal expansion of the light guide plate 42 . There is a disadvantage in that noise is generated due to friction of Since the light guide plate 42 and the pad are in surface contact, noise is generated due to friction caused by the expansion of the light guide plate 42 . In particular, as the pad made of injection plastic increases friction with the light guide plate 42 made of PMMA material, noise generation during driving of the liquid crystal display device is deepened.

In addition, due to the narrow design, the internal space in consideration of the expansion of the light guide plate 42 is insufficient, and the interference with the surrounding components is increasing when the light guide plate 42 is expanded.

An object of the present invention is to provide a backlight unit that minimizes noise due to thermal expansion of a light guide plate, and a liquid crystal display having the same.

In addition, other objects and features of the present invention will be described in the following description of the invention and claims.

In order to achieve the above object, a backlight unit according to an embodiment of the present invention includes a light guide plate, a light source assembly provided in front of an incident surface of the light guide plate, and a plurality of light sources and a printed circuit board on which the light sources are mounted, and the light source It may be configured to include at least one pad disposed between the printed circuit board and in contact with the incident surface of the light guide plate.

The liquid crystal display according to an embodiment of the present invention may be configured to further include a liquid crystal panel provided on an upper surface of the light guide plate in the backlight unit.

The backlight unit and the liquid crystal display according to an embodiment of the present invention include a plurality of protrusions protruding toward the light guide plate at a contact portion where the pad is in contact with the light guide plate to make line contact or point contact with the light guide plate. characterized.

In this case, the pad may include the contact portion contacting the incident surface of the light guide plate and a body connected to the contact portion.

In this case, while the contact portion is elongated in a vertical direction, the body is elongated in a horizontal direction so that the entire pad may have an inverted T-shape.

Each of the protrusions may be parallel to an expansion direction of the light guide plate (a longitudinal direction of the printed circuit board).

Each of the protrusions may have a hemispherical shape or a columnar shape.

In this case, a protective layer having a smaller surface roughness than that of the protrusion may be included on the surface of the protrusion.

As described above, in the backlight unit and the liquid crystal display having the same according to an embodiment of the present invention, the protruding part of the pad makes linear or point contact with the light guide plate to minimize the contact frictional force during expansion of the light guide plate, thereby minimizing thermal expansion noise. characterized in that As a result, it provides the effect of increasing product reliability.

1 is an exploded perspective view schematically showing the structure of a general liquid crystal display device;
2 is a cross-sectional view schematically illustrating a part of a structure of a general backlight unit;
3 is a plan view schematically illustrating a structure of a backlight unit according to a first embodiment of the present invention;
4 is a cross-sectional view schematically illustrating a part of a structure of a backlight unit according to a first embodiment of the present invention;
5A to 5C are schematic views of a pad according to a first embodiment of the present invention;
6 is a perspective view schematically showing an LED array printed circuit board according to a first embodiment of the present invention.
7 is a cross-sectional view schematically showing a part of a structure of a backlight unit according to a second embodiment of the present invention;
8A and 8B are schematic front views of a pad according to a second embodiment of the present invention;
9A and 9B are schematic side views of a pad according to a second embodiment of the present invention;
10a and 10b schematically show a pad according to a third embodiment of the present invention;

Hereinafter, with reference to the accompanying drawings, a preferred embodiment of a backlight unit and a liquid crystal display having the same according to the present invention will be described in detail so that those of ordinary skill in the art can easily implement it.

Advantages and features of the present invention and methods of achieving them will become apparent with reference to the embodiments described below in detail in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be embodied in various different forms, and only these embodiments allow the disclosure of the present invention to be complete, and common knowledge in the art to which the present invention pertains It is provided to fully inform those who have the scope of the invention, and the present invention is only defined by the scope of the claims. Like reference numerals refer to like elements throughout. The sizes and relative sizes of layers and regions in the drawings may be exaggerated for clarity of description.

Reference to an element or layer to another element or “on” or “on” includes not only directly on the other element or layer, but also with other layers or other elements interposed therebetween. do. On the other hand, reference to an element "directly on" or "directly on" indicates that there are no intervening elements or layers.

The spatially relative terms "below, beneath", "lower", "above", "upper", etc. are one element or component as shown in the drawings. and can be used to easily describe the correlation with other devices or components. The spatially relative terms should be understood as terms including different orientations of the device during use or operation in addition to the orientation shown in the drawings. For example, when an element shown in the figures is turned over, an element described as "beneath" or "beneath" another element may be placed "above" the other element. Accordingly, the exemplary term “below” may include both directions below and above.

The terminology used herein is for the purpose of describing the embodiments, and thus is not intended to limit the present invention. In this specification, the singular also includes the plural unless specifically stated otherwise in the phrase. As used herein, "comprise" and/or "comprising" refers to the presence of one or more other components, steps, operations and/or elements mentioned. or addition is not excluded.

3 is a plan view schematically illustrating a structure of a backlight unit according to a first embodiment of the present invention.

4 is a cross-sectional view schematically showing a part of the structure of the backlight unit according to the first embodiment of the present invention, and shows a part of the cross-section taken along line A-A' of FIG. 3 .

5A to 5C are diagrams schematically showing a pad according to a first embodiment of the present invention. At this time, FIG. 5A schematically shows the front side of the pad, FIG. 5B schematically shows the side surface of the pad, and FIG. 5C schematically shows the rear surface of the pad.

And, Figure 6 is a perspective view schematically showing the LED array printed circuit board according to the first embodiment of the present invention.

Referring to the drawings, the liquid crystal display according to the first embodiment of the present invention includes a liquid crystal panel (not shown) in which liquid crystal is injected between a color filter substrate and an array substrate to output an image, and is installed on the rear surface of the liquid crystal panel. The backlight unit 140 that emits light over the entire surface of the liquid crystal panel may include a guide panel 145 and a lower cover 150 for fixing the liquid crystal panel and the backlight unit 140 to each other.

Although not shown, in the liquid crystal panel, pixels are arranged in a matrix to output an image, and a color filter substrate facing each other to maintain a uniform cell gap, an array substrate, and a cell gap between the color filter substrate and the array substrate It consists of a liquid crystal layer formed.

A common electrode and a pixel electrode are formed in the liquid crystal panel to which the color filter substrate and the array substrate are bonded, and an electric field is applied to the liquid crystal layer. , the liquid crystal of the liquid crystal layer rotates by dielectric anisotropy according to the electric field between the common electrode and the pixel electrode, thereby transmitting or blocking light for each pixel to display text or images.

In this case, in order to control the voltage of the data signal applied to the pixel electrode for each pixel, a switching element such as a thin film transistor (TFT) is individually provided in the pixels.

That is, gate lines and data lines that are arranged vertically and horizontally to define a pixel area are formed on the array substrate, and a thin film transistor, which is a switching element, is formed at an intersection area of the gate line and the data line.

The thin film transistor includes a gate electrode connected to a gate line, a source electrode connected to a data line), and a drain electrode connected to a pixel electrode.

The color filter substrate consists of a color filter composed of a plurality of sub-color filters that realize red, green, and blue colors, a black matrix that separates the sub-color filters and blocks light passing through the liquid crystal layer, and a color filter and a black matrix It may consist of an overcoat layer formed thereon.

A polarizing plate is attached to the outside of the color filter substrate and the array substrate, respectively. At this time, the lower polarizing plate polarizes the light passing through the backlight unit 140 , and the upper polarizing plate polarizes the light passing through the liquid crystal panel.

The lower cover 150 includes a bottom portion 150a and a plurality of side portions 150b. The bottom part 150a forms a square shape. The side portions 150b extend vertically from each corner of the bottom portion 150a to have a predetermined height. Edges of the side portions 150b adjacent to each other are connected to each other. The space surrounded by the side parts 150b and the bottom part 150a forms a storage space in which the liquid crystal panel and the backlight unit 140 are accommodated.

The guide panel 145 is placed on the side portion 150b of the lower cover 150 . The guide panel 145 serves to support the liquid crystal panel. To this end, the guide panel 145 includes a body portion 145a placed on the side portion 150b of the lower cover 150 and the body portion 145a. ) and a support portion (not shown) extending toward the receiving space and a rim portion 145b extending downward from the body portion 145a to surround the side portion 150b of the lower cover 150 . The edge of the liquid crystal panel is seated on the support portion of the guide panel 145 .

As such, a liquid crystal panel including a color filter substrate and an array substrate is mounted on the upper portion of the backlight unit 140 through the guide panel 145 , and the lower cover 150 is coupled to the lower portion to constitute a liquid crystal display device.

When the backlight unit 140 according to the first embodiment of the present invention will be described in detail, a light emitting diode (LED) assembly including a light source emitting light on one side of a light guide plate 142 . 130 is provided, and a reflective plate 141 is provided on the rear surface of the light guide plate 142 .

In addition, a plurality of optical sheets 143 for irradiating the liquid crystal panel by improving the efficiency of light emitted from the light guide plate 142 may be disposed on the upper surface of the light guide plate 142 .

However, the present invention is not limited to the structure of the backlight unit 140 described above, and any structure of the backlight unit 140 may be applied to the liquid crystal display device according to the present invention.

The light guide plate 142 receives light from the light source and guides the light toward the liquid crystal panel. In this case, the light provided from the light source is provided to the incident surface of the light guide plate 142 . This incident surface faces one side portion 150b of the side portions 150b of the lower cover 150 . That is, the light source is positioned on one side portion 150b of the lower cover 150 , and the incident surface of the light guide plate 142 faces the light output surface of the light source.

The light guide plate 142 may be made of PMMA plastic.

The reflection plate 141 is positioned between the horizontal portion 132a of the housing 132 and the rear surface of the light guide plate 142 . The reflection plate 141 serves to reflect the light from the light source and the light from the light guide plate 142 toward the liquid crystal panel.

The light source is a means for emitting light, and for example, any one of CCFL (Cold Cathode Fluorescence Lamp), HCFL (Hot Cathode Fluorescence Lamp), EEFL (External Electrode Fluorescence Lamp) or LED may be selected and used, but is not limited thereto. does not Hereinafter, for convenience of explanation, a case in which an LED is used as a light source is exemplified.

The LED array 131 may be formed of a light emitting package including at least one LED. The light emitting package can be a light emitting package having different colors, for example, a red light emitting diode, a green light emitting diode and a blue light emitting diode.

The LED array 131 is installed on the LED array printed circuit board 133 so that the light emitting surface faces the incident surface of the light guide plate 142 .

The LED array printed circuit board 133 is positioned between the incident surface of the light guide plate 142 and the vertical portion 132b of the housing 132 . A plurality of power lines (not shown) and electrical components (not shown) for transmitting power to the light source are formed on the LED array printed circuit board 133 .

The LED array printed circuit board 133 may be a general printed circuit board (PCB) or a metal type printed circuit board. Although not shown, the metal type printed circuit board may be formed of a base layer made of aluminum or a copper alloy, a thermally conductive resin layer formed on the base layer, and conductive patterns formed on the thermally conductive resin layer. These conductor patterns include the power lines described above. Metal-type printed circuit boards are excellent in heat dissipation and mechanical strength enough to be called heat dissipation metal substrates.

The housing 132 includes a horizontal portion 132a and a vertical portion 132b. The horizontal portion 132a of the housing 132 is positioned between the rear surface of the light guide plate 142 and the bottom portion 150a of the lower cover 150 , and the vertical portion 132b is a predetermined distance from one end of the horizontal portion 132a. extends vertically in height. The vertical portion 132b is positioned between the LED array printed circuit board 133 and one side portion 150b of the lower cover 150 .

At this time, a heat dissipation pad 135 is positioned between the LED array printed circuit board 133 and the housing 132 , and the heat dissipation pad 135 serves to radiate heat generated from the light source to the outside. That is, heat generated from the light source may be emitted to the outside through the LED array printed circuit board 133 , the heat dissipation pad 135 , the housing 132 , and the lower cover 150 . To this end, the heat dissipation pad 135 is in physical contact with the LED array printed circuit board 133 and the housing 132 , and the housing 132 is in physical contact with the lower cover 150 .

The above-described LED array 131 , the LED array printed circuit board 133 for driving the LED array 131 , and the housing 132 constitute the LED assembly 130 .

The light source may be connected to an inverter (not shown) to receive power and emit light.

The light emitted from the light source is incident on the side of the light guide plate 142 made of a transparent material, and the reflective sheet 141 disposed on the rear surface of the light guide plate 142 reflects the light transmitted through the rear surface of the light guide plate 142 on the upper surface of the light guide plate 142 . By reflecting toward the optical sheets 143, the loss of light is reduced and the uniformity is improved.

In this case, the optical sheets 143 include a diffuser sheet and upper and lower prism sheets, and a protective sheet may be added thereto.

The optical sheets 143 are provided between the upper surface of the light guide plate 142 and the rear surface of the liquid crystal panel, and the edges of the optical sheets 143 are covered by the support part of the guide panel 145 . The prism sheet collects light from the light guide plate 142, the diffusion sheet diffuses the light from the prism sheet, and the protective sheet serves to protect these prism sheets and the diffusion sheet. The light passing through the protective sheet is provided to the liquid crystal panel.

The light guide plate 142 inside the backlight unit 140 configured as described above is easily expanded by heat generated from the light source. At this time, when the light guide plate 142 expands and collides with a light source located close to it, the light source and the light guide plate 142 are damaged. In this case, the light source may not emit light or the light guide plate 142 may be scratched, thereby causing a problem in that the luminance is lowered.

Accordingly, in the present invention, the contact prevention pad 120 is provided between the LED array printed circuit board 133 and the light guide plate 142 . That is, the pad 120 attached to the LED array printed circuit board 133 serves to maintain the distance between the light guide plate 142 and the LED array 131 while supporting the light guide plate 142 .

The pad 120 may include, for example, a contact portion 122 in contact with the incident surface of the light guide plate 142 and a body 121 connected to the contact portion 122 .

The contact portion 122 of the pad 120 is elongated in a vertical direction, while the body 121 is elongated in a horizontal direction, so that the entire pad 120 may have an inverted T-shape. However, the present invention is not limited thereto.

As the pad 120 has a thickness greater than the thickness of the LED array 131 protruding from the LED array printed circuit board 133, even if the light guide plate 142 expands, it is possible to prevent the light guide plate 142 and the light source from colliding with each other. can That is, even if the light guide plate 142 expands in the direction of the light source (the Y-axis direction in FIG. 3 ) due to heat in the storage space, the light guide plate 142 is prevented from proceeding further by the pad 120 . Accordingly, it is possible to prevent the light guide plate 142 and the light source from colliding with each other, thereby preventing damage to the light guide plate 142 and the light source.

The pad 120 may be made of, for example, a PC plastic.

The pad 120 is disposed between the LED arrays 131 , and a plurality of pads 120 may be provided throughout the LED array printed circuit board 133 . In this case, the pad 120 may be fastened to the LED array printed circuit board 133 by a plurality of fastening means 124 and double-sided tape 125 provided on the rear surface.

At this time, on three surfaces of the light guide plate 142 on which the pad 120 is not located, that is, on three surfaces other than the incident surface of the light guide plate 142 , vibration or the like is caused by the silicon pad 175 attached to the lower cover 150 . Collision between the light guide plate 142 and other components due to an external force can be prevented.

In addition, the pad 120 according to the first embodiment of the present invention includes a plurality of protrusions 123 protruding toward the light guide plate 142 at the contact portion 122 of the pad 120 in contact with the light guide plate 142 . characterized in that At this time, the protrusion 123 according to the first embodiment of the present invention is parallel to the expansion direction of the light guide plate 142 (X-axis or -X-axis direction in FIG. 3; hereinafter referred to as a horizontal direction for convenience of description). characterized in that it is arranged.

The protrusion 123 of the pad 120 makes linear or point contact with the light guide plate 142 to minimize the contact frictional force when the light guide plate 142 expands, thereby preventing thermal expansion noise.

That is, when the liquid crystal display is driven, heat is generated in the LED array 131 and the light guide plate 142 is expanded in the horizontal direction. At this time, although the light guide plate 142 expands also in the vertical direction (the Y-axis direction in FIG. 3 ) perpendicular to the horizontal direction, the light guide plate 142 is incident by the pad 120 made of PC material, which is harder than the silicon pad 175 . As the face is supported, the longitudinal expansion is negligible.

At this time, noise may be generated due to friction between the light guide plate 142 that expands in the horizontal direction and the pad 120 made of PC material. Therefore, in the first embodiment of the present invention, a plurality of protrusions 123 in parallel in the horizontal direction are provided on the contact portion 122 of the pad 120 in contact with the light guide plate 142 to make line contact with the light guide plate 142 . It is characterized in that the contact friction force is minimized.

Each of the protrusions 123 is parallel to the horizontal direction, which is the expansion direction of the light guide plate 142 .

The protrusion 123 has a predetermined height, and by reducing the width as much as possible, it is possible to minimize an area in contact with the light guide plate 142 . The protrusion 124 may protrude to have the same height as the body 121 of the pad 120 , but the present invention is not limited thereto. The protrusion 124 may protrude to protrude more than the body 121 of the pad 120 or to protrude further in.

The upper end of the protrusion 123 in contact with the light guide plate 142 may be flat or may have an angled and round shape as shown in FIGS. 5A and 5B .

In addition, in the present invention, when a protective layer having a smooth surface such as Teflon is formed on the surface of the protruding part of the pad or a tape is attached, the contact friction force can be further reduced, thereby minimizing noise generation. This is because the smooth surface of Teflon is smaller than the surface roughness of the protrusion, which can further reduce the adhesive friction force with the light guide plate.

According to the present invention, the contact friction force can be further reduced by forming the protrusion of the pad in contact with the light guide plate in a hemispherical shape or a columnar shape to make point contact with the light guide plate, which will be described in detail through the second embodiment of the present invention.

7 is a cross-sectional view schematically showing a part of a structure of a backlight unit according to a second embodiment of the present invention.

8A and 8B are schematic front views of a pad according to a second embodiment of the present invention. 9A and 9B are diagrams schematically showing a side surface of a pad according to a second embodiment of the present invention.

In this case, the backlight unit according to the second embodiment of the present invention has substantially the same configuration as the backlight unit according to the first embodiment of the present invention, except for the shape of the protrusion of the pad.

Referring to the drawings, the liquid crystal display according to the second embodiment of the present invention includes a liquid crystal panel (not shown) in which liquid crystal is injected between a color filter substrate and an array substrate to output an image, as described above, and the liquid crystal panel. A backlight unit 240 installed on the back side to emit light over the entire surface of the liquid crystal panel, and a guide panel 245 and a lower cover 250 for fastening the liquid crystal panel and the backlight unit 240 to each other. can

Although not shown, in the liquid crystal panel, pixels are arranged in a matrix form to output an image, and a color filter substrate facing each other to maintain a uniform cell gap, an array substrate, and a cell gap between the color filter substrate and the array substrate It consists of a liquid crystal layer formed.

A polarizing plate is attached to the outside of the color filter substrate and the array substrate, respectively. At this time, the lower polarizing plate polarizes the light passing through the backlight unit 240 , and the upper polarizing plate polarizes the light passing through the liquid crystal panel.

The lower cover 250 includes a bottom portion 250a and a plurality of side portions 250b. The bottom part 250a has a rectangular shape. The side portions 250b extend vertically from each corner of the bottom portion 250a to have a predetermined height. Edges of the side portions 250b adjacent to each other are connected to each other. The space surrounded by the side parts 250b and the bottom part 250a forms a storage space in which the liquid crystal panel and the backlight unit 240 are accommodated.

The guide panel 245 is placed on the side portion 250b of the lower cover 250 . The guide panel 245 serves to support the liquid crystal panel. To this end, the guide panel 245 includes a body portion 245a placed on the side portion 250b of the lower cover 250, and the body portion 245a. ) and a support portion (not shown) extending toward the receiving space and a rim portion 245b extending downward from the body portion 245a to surround the side portion 250b of the lower cover 250 . The edge of the liquid crystal panel is seated on the support portion of the guide panel 245 .

As described above, a liquid crystal panel composed of a color filter substrate and an array substrate is mounted on the upper portion of the backlight unit 240 through the guide panel 245 , and the lower cover 250 is coupled to the lower portion to constitute a liquid crystal display device.

When the backlight unit 240 according to the second embodiment of the present invention will be described in detail, an LED including a light source for generating light on one side of the light guide plate 242 is substantially the same as that of the first embodiment of the present invention described above. The assembly 230 is installed, and the reflection plate 241 is installed on the rear surface of the light guide plate 242 .

In addition, a plurality of optical sheets 243 for irradiating the liquid crystal panel by improving the efficiency of light emitted from the light guide plate 242 may be disposed on the upper surface of the light guide plate 242 .

However, the present invention is not limited to the structure of the backlight unit 240 described above, and any structure of the backlight unit 240 may be applied to the liquid crystal display according to the present invention.

The light guide plate 242 receives light from the light source and guides the light toward the liquid crystal panel. In this case, the light provided from the light source is provided to the incident surface of the light guide plate 242 . This incident surface faces one side part 250b of the side parts 250b of the lower cover 250 . That is, the light source is positioned on one side portion 250b of the lower cover 250 , and the incident surface of the light guide plate 242 faces the light output surface of the light source.

The light guide plate 242 may be made of PMMA plastic.

The reflection plate 241 is positioned between the horizontal portion 232a of the housing 232 and the rear surface of the light guide plate 242 . The reflection plate 241 serves to reflect the light from the light source and the light from the light guide plate 242 toward the liquid crystal panel.

In the case of using an LED as a light source, the LED array 231 may be formed of a light emitting package including at least one LED. The light emitting package can be a light emitting package having different colors, for example, a red light emitting diode, a green light emitting diode and a blue light emitting diode.

The LED array 231 is installed on the LED array printed circuit board 233 so that the light emitting surface faces the incident surface of the light guide plate 242 .

The LED array printed circuit board 233 is positioned between the incident surface of the light guide plate 242 and the vertical portion 232b of the housing 232 . A plurality of power lines (not shown) and electrical components (not shown) for transmitting power to the light source are formed on the LED array printed circuit board 233 .

The LED array printed circuit board 233 may be a general printed circuit board or a metal type printed circuit board.

The housing 232 includes a horizontal portion 232a and a vertical portion 232b. The horizontal part 232a of the housing 232 is positioned between the rear surface of the light guide plate 242 and the bottom part 250a of the lower cover 250 , and the vertical part 232b is a predetermined distance from one end of the horizontal part 232a. extends vertically in height. The vertical portion 232b is positioned between the LED array printed circuit board 233 and one side portion 250b of the lower cover 250 .

In this case, a heat dissipation pad 235 is positioned between the LED array printed circuit board 233 and the housing 232 , and the heat dissipation pad 235 serves to radiate heat generated from the light source to the outside. To this end, the heat dissipation pad 235 is in physical contact with the LED array printed circuit board 233 and the housing 232 , and the housing 232 is in physical contact with the lower cover 250 .

The above-described LED array 231 , the LED array printed circuit board 233 for driving the LED array 231 , and the housing 232 constitute the LED assembly 230 .

The light source may be connected to an inverter (not shown) to receive power and emit light.

The light emitted from the light source is incident on the side of the light guide plate 242 made of a transparent material, and the reflective sheet 241 disposed on the rear surface of the light guide plate 242 transmits light transmitted through the rear surface of the light guide plate 242 to the upper surface of the light guide plate 242 . By reflecting toward the optical sheets 243, light loss is reduced and uniformity is improved.

In this case, the optical sheets 243 include a diffusion sheet and upper and lower prism sheets, and a protective sheet may be added.

At this time, as described above, the present invention is characterized in that the contact prevention pad 220 is provided between the LED array printed circuit board 233 and the light guide plate 242 . That is, the pad 220 attached to the LED array printed circuit board 233 serves to maintain the distance between the light guide plate 242 and the LED array 231 while supporting the light guide plate 242 .

The pad 220 may include, for example, a contact portion 222 in contact with the incident surface of the light guide plate 242 and a body 221 connected to the contact portion 222 .

The contact portion 222 of the pad 220 is elongated in the vertical direction, while the body 221 is elongated in the horizontal direction, so that the entire pad 220 may have an inverted T-shape. However, the present invention is not limited thereto.

As the pad 220 has a thickness greater than the thickness of the LED array 231 protruding from the LED array printed circuit board 233, even if the light guide plate 242 expands, it is possible to prevent the light guide plate 242 and the light source from colliding with each other. can Accordingly, it is possible to prevent the light guide plate 242 and the light source from colliding with each other, thereby preventing damage to the light guide plate 242 and the light source.

The pad 220 may be made of, for example, a PC plastic.

The pad 220 is disposed between the LED arrays 231 , and a plurality of pads 220 may be provided throughout the LED array printed circuit board 233 . In this case, the pad 220 may be fastened to the LED array printed circuit board 233 by a plurality of fastening means 224 provided on the rear surface and double-sided tape (not shown).

At this time, the pad 220 according to the second embodiment of the present invention includes a plurality of protrusions 223 protruding toward the light guide plate 242 at the contact portion 222 of the pad 220 in contact with the light guide plate 242 . characterized in that

The protrusion 223 of the pad 220 has a hemispherical shape (in the case shown in FIG. 9B) or a columnar shape (in the case shown in FIG. 9A), and makes point contact with the light guide plate 242 when the light guide plate 242 is expanded. By minimizing contact friction, it provides the effect of maximally preventing thermal expansion noise.

That is, as described above, noise may be generated due to friction between the light guide plate 242 that expands in the horizontal direction and the pad 220 made of a PC material. Accordingly, in the second embodiment of the present invention, a plurality of hemispherical or pillar-shaped protrusions 223 are provided on the contact portion 222 of the pad 220 in contact with the light guide plate 242 to make point contact with the light guide plate 242 . It is characterized in that the contact friction force can be further reduced compared to the first embodiment of the present invention described above.

The pillar-shaped protrusion 223 has a predetermined height, and by reducing the width as much as possible, it is possible to minimize an area in contact with the light guide plate 242 . In this case, the upper end of the protrusion 223 in contact with the light guide plate 242 may be flat or may have an angled and round shape as shown in FIG. 9A .

These protrusions 223 may be arranged in a row up and down (as shown in FIG. 8A ) or alternately up and down (as shown in FIG. 8B ).

As described above, in the present invention, when a coating layer having a smooth surface such as Teflon is formed on the surface of the protruding part of the pad or a tape is attached, the contact friction force can be further reduced, thereby maximally reducing noise generation. will be described in detail through the third embodiment of the present invention. This is because the smooth surface of Teflon is smaller than the surface roughness of the protrusion, which can further reduce the adhesive friction force with the light guide plate.

10A and 10B are diagrams schematically showing a pad according to a third embodiment of the present invention.

At this time, FIG. 10A schematically shows the front side of the pad, and FIG. 10B schematically shows the side surface of the pad, including an enlarged view of a part of the contact part of the pad.

10A and 10B , the pad 320 according to the third embodiment of the present invention includes, for example, a contact portion 322 in contact with the incident surface of the light guide plate and a body connected to the contact portion 322 ( 321) can be configured.

The contact portion 322 of the pad 320 is elongated in the vertical direction, while the body 321 is elongated in the horizontal direction, so that the entire pad 320 may have an inverted T-shape. However, the present invention is not limited thereto.

As described above, since the pad 320 has a thickness greater than that of the LED array protruding from the LED array printed circuit board, it is possible to prevent the light guide plate and the light source from colliding with each other even if the light guide plate is expanded.

The pad 320 may be made of, for example, a PC plastic.

The pad 320 is disposed between the LED arrays, and a plurality of pads 320 may be provided over the entire LED array printed circuit board. In this case, the pad 320 may be fastened to the LED array printed circuit board by a plurality of fastening means 324 provided on the rear surface and double-sided tape (not shown).

In this case, the pad 320 according to the third embodiment of the present invention is characterized in that it includes a plurality of protrusions 323 protruding toward the light guide plate at the contact portion 322 of the pad 320 in contact with the light guide plate. In this case, the protrusions 323 according to the third embodiment of the present invention are characterized in that they are arranged in parallel in the expansion direction (ie, the horizontal direction) of the light guide plate. However, the present invention is not limited thereto, and the protrusion 323 according to the third embodiment of the present invention may have a hemispherical shape or a columnar shape like the second embodiment of the present invention described above.

The protrusion 323 of the pad 320 makes linear or point contact with the light guide plate to minimize the contact frictional force when the light guide plate is expanded, thereby providing an effect of preventing thermal expansion noise.

That is, as described above, noise may be generated due to friction between the light guide plate expanding in the horizontal direction and the pad 320 made of PC material. Accordingly, in the third embodiment of the present invention, a plurality of protrusions 323 in the shape of a hemispherical or column or parallel to the contact portion 322 of the pad 320 in contact with the light guide plate 342 are provided in a horizontal direction. It is characterized in that the contact friction force is minimized by making line or point contact with the light guide plate.

Each of the protrusions 323 is parallel to the horizontal direction, which is the expansion direction of the light guide plate.

The protrusion 323 has a predetermined height, and by reducing the width as much as possible, it is possible to minimize an area in contact with the light guide plate.

The upper end of the protrusion 323 in contact with the light guide plate may have a flat or angled round shape.

In addition, on the surface of the protrusion 323 of the pad 320 according to the third embodiment of the present invention, a coating layer 325 having a smooth surface such as Teflon may be formed or a tape may be attached. It can be further reduced, providing the effect of maximally reducing noise generation. This is because the smooth surface of the Teflon is smaller than the surface roughness of the protrusion 323 , so that the adhesive friction force with the light guide plate 342 can be further reduced.

The coating layer 325 may be formed on the front surface of the pad 320 or on the front surface of the contact portion 322 of the pad 320 (in the case shown in FIG. 10B ) including the protrusion 323 . However, the present invention is not limited thereto, and the coating layer 325 according to the third embodiment of the present invention may be formed only on the surface of the protrusion 323 .

Although many matters are specifically described in the above description, these should be construed as examples of preferred embodiments rather than limiting the scope of the invention. Accordingly, the invention should not be defined by the described embodiments, but should be defined by the claims and equivalents to the claims.

120,220,320: pad 121,221,321: body
122,222,322: contact part 123,223,323: protrusion
124,224,324: fastening means 132,232: housing
133,233: LED array printed circuit board
140,240: backlight unit 141,241: reflector
142,242: light guide plate 143,243: optical sheet
145,245: guide panel 150,250: lower cover
325: coating layer

Claims (12)

a lower cover including a sea portion and a side portion extending in a direction perpendicular to the bottom portion;
a light guide plate having an incident surface facing the side surface;
a housing including a horizontal portion positioned between a rear surface of the light guide plate and the bottom portion of the lower cover and a vertical portion extending from the horizontal portion in the vertical direction;
an LED array positioned between the incident surface of the light guide plate and the vertical portion of the housing and including at least one LED;
an LED printed circuit board on which the LED array is mounted and driving the LED array;
a heat dissipation pad disposed between the LED printed circuit board and the vertical portion of the housing; and
It is disposed between the LED printed circuit board and the incident surface of the light guide plate, and includes at least one pad in contact with the incident surface of the light guide plate,
The pad includes a contact portion contacting the incident surface of the light guide plate and a body connected to the contact portion, wherein the contact portion includes a plurality of protrusions protruding toward the incident surface of the light guide plate to make line contact with the light guide plate or point contact,
A coating layer having a smaller surface roughness than the protrusion is provided on the front surface of the contact part having the protrusion part, the backlight unit. delete The backlight unit of claim 1 , wherein the contact portion is elongated in the vertical direction while the body is elongated in the horizontal direction, so that the entire pad has an inverted T-shape. The backlight unit of claim 1 , wherein each of the protrusions is parallel to an expansion direction of the light guide plate (a longitudinal direction of the LED printed circuit board). The backlight unit of claim 1 , wherein each of the protrusions has a hemispherical shape or a pillar shape. delete a light guide plate; a lower cover including a bottom part and a side part extending in a direction perpendicular to the bottom part;
a light guide plate having an incident surface facing the side surface;
a housing including a horizontal portion positioned between a rear surface of the light guide plate and the bottom portion of the lower cover and a vertical portion extending from the horizontal portion in the vertical direction;
a liquid crystal panel provided on the upper surface of the light guide plate;
an LED array positioned between the incident surface of the light guide plate and the vertical portion of the housing and including at least one LED;
an LED printed circuit board on which the LED array is mounted;
a heat dissipation pad disposed between the LED printed circuit board and the vertical portion of the housing; and
at least one pad disposed between the LED printed circuit board and the incident surface of the light guide plate and in contact with the incident surface of the light guide plate;
The pad includes a contact portion contacting the incident surface of the light guide plate and a body connected to the contact portion, and the contact portion includes a plurality of protrusions protruding toward the light guide plate to make line contact or point contact with the light guide plate. and
A liquid crystal display having a coating layer having a smaller surface roughness than that of the protruding part on the front surface of the contact part having the protrusion part. The liquid crystal display device of claim 7 , wherein each of the protrusions is parallel to an expansion direction of the light guide plate (a longitudinal direction of the printed circuit board). The liquid crystal display device of claim 7 , wherein each of the protrusions has a hemispherical shape or a pillar shape. delete The backlight unit of claim 1 , wherein the pad is in direct contact with the heat dissipation pad located on a rear surface of the LED printed circuit board. The backlight unit of claim 1 , wherein the protrusion of the pad has a thickness greater than that of the LED array.

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