KR102565085B1 - Liquid crystal display device - Google Patents

Abstract

A liquid crystal display device according to an embodiment of the present invention includes a liquid crystal display panel, a plurality of optical sheets, a light guide plate, a guide panel, a cover bottom, and a side cover. A plurality of optical sheets are disposed below the liquid crystal display panel, and a light guide plate is disposed below the optical sheets. The guide panel is disposed between the liquid crystal display panel and the optical sheets to support the liquid crystal display panel. The cover bottom accommodates the light guide plate. The side cover covers at least one side surface of the light guide plate.

Description

Liquid crystal display {LIQUID CRYSTAL DISPLAY DEVICE}

The present invention relates to a liquid crystal display device including a backlight unit.

Liquid crystal display devices are used as display devices in various fields such as portable computers such as notebook PCs, office automation devices, audio/video devices, indoor and outdoor advertising displays, and vehicle displays. The liquid crystal display may be divided into a reflective type, a transflective type, a transmissive type, and the like. A transflective or transmissive liquid crystal display displays an image by controlling an electric field applied to a liquid crystal layer to adjust light incident from a back light unit (BLU) according to a data voltage.

Fluorescent lamps such as Cold Cathode Fluorescent Lamps (CCFLs) have been used as light sources for backlight units, but recently, light emitting diodes (hereinafter referred to as 'LEDs') are mainly used compared to conventional fluorescent lamps. It is becoming.

In-vehicle displays are getting larger in size and the quantity installed per vehicle is also increasing. In-vehicle displays are being applied as driving support interfaces in addition to navigation. Vehicle displays are expanding their application range to instrument panels, driver warnings, and display means for driving assistance. In addition, liquid crystal displays are also being applied to Head-Up Display (HUD) devices that project vehicle speed, remaining fuel, and navigation information as graphic images on the windshield right in front of the driver. A liquid crystal display is being applied for a Rear-Seat Entertainment (RSE) system for enjoying DVD movies or games in the back seat of a vehicle.

Since the display for a vehicle requires visibility even in sunlight, high brightness is required compared to displays for other purposes, and reliability under vehicle temperature conditions and vibration conditions is required.

A liquid crystal display device includes a liquid crystal display panel and a backlight unit. The backlight unit has a structure in which a light source is disposed to face a side surface of the light guide plate and a plurality of optical sheets are disposed between the liquid crystal display panel and the light guide plate. The liquid crystal display panel and the backlight unit are assembled together with case members that fix them to be implemented as a liquid crystal module (LCM). The case member may include a guide panel, a cover bottom, a case top, and the like.

The light guide plate and the optical sheets accommodated in the case member may expand or contract or move their positions due to external factors such as temperature change, humidity change, external shock, or vibration. When the light guide plate and the optical sheets are damaged due to movement, the optical characteristics of the liquid crystal display may be changed. This deteriorates product reliability of the liquid crystal display device, such as causing poor image quality.

An object of the present invention is to provide a liquid crystal display capable of preventing noise caused by the flow of light guide plates and optical sheets that may occur due to external factors such as temperature change.

In order to achieve the above object, a liquid crystal display device according to an embodiment of the present invention includes a liquid crystal display panel, a plurality of optical sheets, a light guide plate, a guide panel, a cover bottom, and a side cover. A plurality of optical sheets are disposed below the liquid crystal display panel, and a light guide plate is disposed below the optical sheets. The guide panel is disposed between the liquid crystal display panel and the optical sheets to support the liquid crystal display panel. The cover bottom accommodates the light guide plate. The side cover covers at least one side surface of the light guide plate.

The light guide plate includes a first surface facing the optical sheets, a second surface facing the first surface, and a third surface perpendicular to the first surface and the second surface. The side cover covers first to third surfaces of the light guide plate.

The optical sheets are separated from the side cover by a predetermined gap. The side cover may be a bar type covering all one side of the light guide plate or a piece type covering a part of one side surface of the light guide plate.

The light guide plate further includes a first step formed at a corner where the first and second surfaces meet and a second step formed at a corner where the second and third surfaces meet, and the side cover covers the first step and the second step. .

The first step of the light guide plate includes at least one groove, and a part of the side cover is coupled to the groove.

Also, a display device according to an exemplary embodiment includes a liquid crystal display panel, a plurality of optical sheets, a light guide plate, a guide panel, and a cover bottom. A plurality of optical sheets are disposed below the liquid crystal display panel and have at least one hole at an edge thereof. The light guide plate is disposed below the optical sheets, has at least one protrusion at one edge thereof, and is inserted into at least one hole of the plurality of optical sheets. The guide panel is disposed between the liquid crystal display panel and the optical sheets to support the liquid crystal display panel. The cover bottom accommodates the light guide plate.

At least one protrusion of the light guide plate is spaced apart from an end of the light guide plate.

According to the present invention, the flow of the optical sheet can be reduced and noise can be prevented by reducing an assembly gap by providing a side cover or a protrusion on the light guide plate. In particular, since the risk of interference between the optical sheets may be reduced due to the light guide plate flowing in the same direction as the optical sheets depending on the temperature, there is an advantage in reducing wrinkle defects of the optical sheets.

1 and 2 are exploded perspective views showing a liquid crystal display device according to the present invention.
3 is a perspective view showing a backlight unit according to the present invention;
4 and 5 are cross-sectional views taken along the line II′ of FIG. 3;
6 is a cross-sectional view illustrating a backlight unit according to a first embodiment of the present invention.
7 to 9 are perspective views illustrating a light guide plate equipped with a side cover according to the present invention.
10 and 6 are cross-sectional views illustrating a backlight unit according to a first embodiment of the present invention.
11 is a perspective view illustrating a backlight unit according to a second embodiment of the present invention;
12 and 13 are cross-sectional views illustrating a backlight unit according to a second embodiment of the present invention.
14 is a cross-sectional view illustrating a backlight unit according to a third embodiment of the present invention.
15 is a perspective view illustrating a light guide plate of a backlight unit according to a third embodiment of the present invention;
16 is a perspective view illustrating a backlight unit according to a third embodiment of the present invention;
17 is an image of wrinkles generated in an optical sheet observed on a liquid crystal display panel;
18 is an image of wrinkles generated in an optical sheet observed in a backlight unit.

Hereinafter, preferred embodiments according to the present invention will be described in detail with reference to the accompanying drawings. Like reference numbers throughout the specification indicate substantially the same elements. In the following description, if it is determined that a detailed description of a known function or configuration related to the present invention may unnecessarily obscure the subject matter of the present invention, the detailed description will be omitted. In describing various embodiments, the same components are representatively described at the beginning and may be omitted thereafter.

Terms including ordinal numbers, such as first and second, may be used to describe various components, but the components are not limited by the terms. These terms are only used for the purpose of distinguishing one component from another.

1 and 2 are exploded perspective views showing a liquid crystal display device according to the present invention, FIG. 3 is a perspective view showing a backlight unit according to the present invention, and FIGS. 4 and 5 are cross-sectional views taken along the line II' of FIG. 3 am.

Referring to FIGS. 1 to 4 , a liquid crystal display device according to an embodiment of the present invention includes a liquid crystal display panel (PNL) and a backlight unit (BLU) disposed under the liquid crystal display panel (PNL). The liquid crystal display panel PNL includes an upper substrate, a lower substrate, and a liquid crystal layer interposed between the upper and lower substrates.

More specifically, the lower substrate of the liquid crystal display panel PNL includes data lines supplied with video data voltages, gate lines crossed with the data lines and sequentially supplied with scan signals, that is, gate pulses, data lines and gates. It includes a pixel and a TFT array including TFTs formed at intersections of lines, pixel electrodes of a liquid crystal cell connected to the TFTs, and a storage capacitor. An upper substrate of the liquid crystal display panel PNL includes a black matrix, a color filter, and a common electrode. The common electrode is formed on the upper substrate in vertical electric field driving methods such as TN (Twisted Nematic) mode and VA (Vertical Alignment) mode, and horizontal electric field driving such as IPS (In Plane Switching) mode and FFS (Fringe Field Switching) mode. In this method, it is formed on the lower substrate together with the pixel electrode. A polarizing plate and a polarizing plate protective film are attached to each of the upper substrate and the lower substrate.

The backlight unit BLU is provided below the liquid crystal display panel PNL and radiates light to the rear surface of the liquid crystal display panel PNL. The backlight unit BLU includes a light source LS, a light guide plate LGP, and at least one optical sheet OPS. The light supplied from the light source LS to the light incident surface of the light guide plate LGP is converted into a form of the surface light source LS and emitted to the front surface of the light guide plate LGP, and the optical sheet positioned on the light guide plate LGP. While passing through (OPS), it is uniformly irradiated to the rear surface of the liquid crystal display panel (PNL).

The light source (LS) is one or more light sources (LS) of lamps such as a light emitting diode (LED), a cold cathode fluorescent lamp (CCFL), and an external electrode fluorescent lamp (EEFL). can include The light source LS radiates light to a side surface of the light guide plate LGP facing at least one side surface (or light incident surface) of the light guide plate LGP. The light guide plate (LGP) is a plate material molded from transparent plastic, for example, polymethacrylate (PMMA), and converts light in the form of a point light source (LS) or line light source (LS) into light in the form of a surface light source (LS). plays a role in converting

The optical sheets OPS include one or more prism sheets and one or more diffuser sheets to diffuse light incident from the light guide plate LGP and to substantially affect the light incident surface of the liquid crystal display panel PNL. refracts the path of light at a perpendicular angle.

The optical sheets OPS may include first to third optical sheets SH1 , SH2 , and SH3 . For example, the first optical sheet SH1 may be a diffusion sheet, the second optical sheet SH2 may be a prism sheet, and the third optical sheet SH3 may be a multilayer optical film DBEF. However, it is not limited thereto. Hereinafter, for convenience of explanation, a case in which the optical sheets OPS OPS include first to third optical sheets SH1 , SH2 , and SH3 will be described as an example.

Below the light guide plate LGP, a lower reflector BREF is disposed to increase the efficiency of light incident on the liquid crystal display panel PNL by reflecting light incident from the light guide plate LGP. The lower reflector BREF may be adhered to the cover bottom CB. In addition, a side reflector SREF is disposed in the light-receiving portion of the light guide plate LGP.

The liquid crystal display panel (PNL) and the backlight unit (BLU) are assembled together with the cover bottom (CB), guide panel (GP), and case top (CT) to form a liquid crystal module (Liquid Crystal Module, LCM).

The cover bottom CB has a cross section of an “B” shape having at least one bent portion. The backlight unit BLU including the light source LS, the light guide plate LGP, and at least one optical sheet OPS is accommodated in the inner space provided by the cover bottom CB. The cover bottom CB may include a material having high thermal conductivity and high stiffness so as to smoothly dissipate heat from the driving circuit and the light source LS to the outside. For example, the cover bottom (CB) is made of aluminum, aluminum nitride (AlN), electro-galvanized steel (EGI), stainless (SUS), galvalume (SGLC), aluminum-plated steel (aka ALCOSTA), tin-plated steel (SPTE) It may be made of a metal plate such as In addition, such a metal plate may be coated with a high-conductivity material to promote heat transfer.

The guide panel GP is disposed below the liquid crystal display panel PNL. The guide panel GP includes a panel support part SP provided between the liquid crystal display panel PNL and the backlight unit BLU to support an edge of the liquid crystal display panel PNL from a lower portion. The panel support part SP is provided between the liquid crystal display panel PNL and the optical sheet OPS to maintain a constant distance between the liquid crystal display panel PNL and the optical sheet OPS. The guide panel GP may have a rectangular frame shape through which a center is penetrated. The guide panel GP may be made of a plastic-based material that can be molded into a mold, such as polycarbonate.

The case top CT is disposed to surround the side surfaces of the guide panel GP and the cover bottom CB. The case top may be fixed to the guide panel GP and/or the cover bottom CB by a screw or screwless fastening method. The case top CT may be made of a metal plate such as electro-galvanized steel (EGI), stainless (SUS), galvalume, aluminum-coated steel (aka ALCOSTA), and tin-plated steel (SPTE).

Meanwhile, as shown in FIGS. 4 and 5 , the optical sheet OPS is spaced apart from the cover bottom CB by a predetermined gap G to have an assembly margin. However, the optical sheet OPS expands/adsorbs according to the temperature, and causes wrinkles by contacting the cover bottom CB while canceling the gap G with the cover bottom CB. In order to prevent this, if a sufficient gap G is set between the cover bottom CB and the optical sheet OPS, the flow of the optical sheet OPS increases, resulting in noise.

Therefore, in order to prevent wrinkles and noise caused by the movement of the optical sheet OPS according to temperature, a means for guiding the optical sheet to the light guide plate is provided.

6 is a cross-sectional view showing a backlight unit according to a first embodiment of the present invention, FIGS. 7 to 9 are perspective views showing a light guide plate equipped with a side cover of the present invention, and FIG. 10 is a first embodiment of the present invention. It is a cross-sectional view showing the backlight unit according to the embodiment.

Referring to FIG. 6 , the light guide plate LGP has a first surface S1 facing the optical sheets OPS, a second surface S2 opposite the first surface S1 , and a first surface S1 . and a third surface S3 which is a side surface perpendicular to the second surface S2. In the present invention, a side cover (SC) covering the first surface (S1), the second surface (S2), and the third surface (S3) of the light guide plate (LGP) is included. The side cover SC is provided on the side of the light guide plate LGP, which expands or contracts according to temperature, like the optical sheets OPS, and serves to guide the optical sheets OPS.

Table 1 below shows the thermal expansion coefficients of the optical sheet, the light guide plate, and the cover bottom.

Optical Sheet (PET) Light guide plate (PC) Cover bottom (Al) Coefficient of thermal expansion (10 ^-6 m/mK) 59.4 70.2 22.2

Referring to Table 1 above, it can be fully confirmed that the optical sheet and the light guide plate can contract or expand due to heat.

As shown in FIG. 7 , the side cover SC may be formed of a bar type covering all one side of the light guide plate LGP. Also, as shown in FIGS. 8 and 9 , the side cover SC may be of a piece type covering a part of one side of the light guide plate LGP. However, the present invention is not limited thereto, and any structure of the side cover SC may be used as long as it surrounds the first, second, and third surfaces of the light guide plate LGP. Also, when the light guide plate LGP is mounted on the cover bottom CB, at least one side is closely adhered to the cover bottom CB to be fixed. Therefore, the side cover SC of the present invention may be provided on the remaining sides of the light guide plate LGP that are not in close contact with the cover bottom CB.

Referring to FIG. 10 , the side cover SC is provided on at least one side of the light guide plate LGP. The side cover SC expands or contracts according to the temperature and the light guide plate LGP expands or contracts at the same time as the optical sheets OPS, so that the side cover SC moves together with the optical sheets OPS and the optical sheets ( The assembly gap (G) with OPS) can be set to the minimum. For example, when the side cover SC is not provided, the assembly gap G between the optical sheets OPS and the cover bottom CB is set to about 0.5 mm. An assembly gap G between the seat OPS and the side cover SC may be set to about 0.145 mm.

Accordingly, the present invention has an advantage of reducing the movement of the optical sheet and preventing noise by reducing an assembly gap by providing a side cover on at least one side of the light guide plate. In particular, since the risk of interference between the optical sheets may be reduced due to the side cover that flows in the same direction as the optical sheets depending on the temperature, there is an advantage in reducing wrinkle defects of the optical sheets.

11 is a perspective view showing a backlight unit according to a second embodiment of the present invention, and FIGS. 12 and 13 are cross-sectional views showing a backlight unit according to a second embodiment of the present invention.

Referring to FIGS. 11 and 12 , the present invention includes a side cover SC covering the first surface S1 , the second surface S2 , and the third surface S3 of the light guide plate LGP. Unlike the first embodiment described above, the light guide plate LGP includes a first step USG formed at a corner where the first surface S1 and the second surface S2 meet, and the second surface S2 and the second surface S2 A second step LSG formed at the corner where the three surfaces S3 meet is included. The first level difference USG refers to a region where the thickness of the light guide plate LGP is reduced on the first surface S1 of the light guide plate LGP, and the second level difference LSG is formed on the third surface S3 of the light guide plate LGP. This refers to a region where the thickness of the light guide plate LGP is reduced.

The side cover SC of the present invention covers the first step USG, the second step LSG, and the third surface S3 of the light guide plate LGP. The side cover SC is provided on the side of the light guide plate LGP, which expands or contracts according to temperature, like the optical sheets OPS, and serves to guide the optical sheets OPS. In this case, the lower surface of the side cover SC surrounding the second step LSG of the light guide plate LGP coincides with the second surface S2 of the light guide plate LGP, so that the light guide plate LGP and the side cover SC unify In addition, the upper surface of the side cover SC surrounding the first step USG of the light guide plate LGP is formed to protrude beyond the first surface S1 of the light guide plate LGP, thereby forming an assembly gap with the optical sheet OPS ( G) to keep

Also, referring to FIG. 13 , the first step USG of the light guide plate LGP includes at least one groove UGR. A part of the side cover (SC), for example, an end, is coupled to the groove (UGR) of the light guide plate (LGP) to maintain the bonding force between the side cover (SC) and the light guide plate (LGP).

Therefore, the display device according to the second embodiment of the present invention has the advantage of reducing the flow of the optical sheet and preventing noise by providing a side cover on at least one side of the light guide plate and reducing an assembly gap with the optical sheet. . In addition, reliability may be improved by increasing unity and bonding force between the side cover and the light guide plate.

14 is a cross-sectional view showing a backlight unit according to a third embodiment of the present invention, FIG. 15 is a perspective view showing a light guide plate of the backlight unit according to a third embodiment of the present invention, and FIG. 3 It is a perspective view showing the backlight unit according to the embodiment.

Referring to FIG. 14 , in the third embodiment of the present invention, unlike the first and second embodiments described above, at least one protrusion PP is provided on the first surface S1 of the light guide plate LGP. The protrusion PP is formed integrally with the light guide plate LGP and serves to support the optical sheets OPS. The optical sheets OPS disposed on the light guide plate LGP have at least one hole OCH. At least one protrusion PP of the light guide plate LGP is inserted into and coupled to at least one hole OCH provided in the optical sheets OPS, so that the light guide plate LGP expands or expands together with the optical sheets OPS. While shrinking, the optical sheets OPS are guided.

Referring to FIG. 15 , the protrusion PP of the light guide plate LGP is arranged spaced apart from the end of the light guide plate LGP and has a rectangular parallelepiped shape. do.

Referring to FIG. 16 , the holes OCH of the optical sheets OPS are spaced apart from ends of the optical sheets OPS. The hole OCH of the optical sheets OPS has a planar shape similar to that of the protrusion PP of the light guide plate LGP so that the protrusion PP of the light guide plate LGP can be inserted therein. For example, if the planar shape of the projection PP of the light guide plate LGP is a rectangle, the planar shape of the hole OCH of the optical sheets OPS is also rectangular so that they can be coupled to each other.

Therefore, the display device according to the third embodiment of the present invention has an advantage of reducing the movement of the optical sheets and preventing noise by providing protrusions on the light guide plate and providing holes on the optical sheets to be coupled to each other.

FIG. 17 is an image of wrinkles generated in an optical sheet observed on a liquid crystal display panel, and FIG. 18 is an image obtained by observing wrinkles generated on an optical sheet in a backlight unit.

Referring to FIGS. 17 and 18 , when the protrusions of the side cover or the light guide plate are not provided, the optical sheets OPS expand by heat and interfere with the cover bottom CB. Therefore, the occurrence of wrinkles in the optical sheets OPS is observed in both the liquid crystal display panel and the backlight unit, resulting in deterioration in display quality.

As described above, the present invention has the advantage of reducing the movement of the optical sheet and preventing noise by reducing the assembly gap by providing the side cover or the protrusion on the light guide plate. In particular, since the risk of interference between the optical sheets may be reduced due to the light guide plate flowing in the same direction as the optical sheets depending on the temperature, there is an advantage in reducing wrinkle defects of the optical sheets.

Through the above description, those skilled in the art will know that various changes and modifications are possible without departing from the technical spirit of the present invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification, but should be determined by the claims.

OPS: optical films CB: cover bottom
LGP: light guide plate SC: side cover
GP: Guide Panel

Claims (9)

liquid crystal display panel;
a plurality of optical sheets disposed under the liquid crystal display panel;
a light guide plate disposed below the optical sheets;
a guide panel disposed between the liquid crystal display panel and the optical sheets to support the liquid crystal display panel;
a cover bottom accommodating the light guide plate; and
Including a side cover surrounding at least one side of the light guide plate,
The light guide plate,
a step formed at a corner where at least two surfaces meet; and
At least one groove formed in the step,
A portion of the side cover is coupled to the groove. According to claim 1,
The light guide plate includes a first surface facing the optical sheets, a second surface facing the first surface, and a third surface perpendicular to the first surface and the second surface. According to claim 2,
The side cover covers first to third surfaces of the light guide plate. According to claim 3,
The optical sheets are spaced apart from the side cover by a predetermined gap. According to claim 1,
The side cover is formed of a bar type covering all one side surface of the light guide plate or a piece type covering a part of one side surface of the light guide plate. According to claim 3,
The step includes a first step formed at a corner where the first surface and the second surface meet and a second step formed at a corner where the second surface and the third surface meet,
The side cover surrounds the first step and the second step. According to claim 6,
The first step of the light guide plate includes the at least one groove, and a part of the side cover is coupled to the groove. delete delete

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