KR20060109663A - Backlight unit and liquid crystal display device having the same - Google Patents

Abstract

A backlight unit and an LCD including the same are provided to reduce a light loss and improve a brightness by providing a transparent plate on an LED(light emitting diode) and having a total reflection preventing pattern. An LED circuit board(52) includes an LED(51). A transparent plate(60) is placed on the LED and has a total reflection preventing pattern(62) on its emission surface. A light blocking unit(61) is formed at an incidence surface of the transparent plate, corresponding to the LED.

Description

BACKLIGHT UNIT AND LIQUID CRYSTAL DISPLAY DEVICE HAVING THE SAME}

1 and 2 are an exploded perspective view and a cross-sectional view of a liquid crystal display device according to a first embodiment of the present invention;

3 is a view for explaining the reason why the optical loss is reduced in the liquid crystal display according to the first embodiment of the present invention,

4 is a perspective view of principal parts of a liquid crystal display according to a second embodiment of the present invention;

5 is a perspective view of an essential part of a liquid crystal display according to a third exemplary embodiment of the present invention.

6 is a cross-sectional view of main parts of a liquid crystal display device according to a fourth embodiment of the present invention; and

7 is a perspective view of an essential part of a liquid crystal display according to a fifth exemplary embodiment of the present invention.

Explanation of symbols on the main parts of the drawings

10: upper chassis 20: liquid crystal display panel

25 drive unit 30 optical member

40: reflector 51: LED

52: LED circuit board 60: transparent plate

61: light shield 62,63,64: total reflection suppression pattern

   71: diffusion film 73: prism film

   80: lower chassis

The present invention relates to a backlight unit and a liquid crystal display including the same, and more particularly, to a direct type backlight unit and a liquid crystal display including the same.

The liquid crystal display device includes a thin film transistor substrate, a color filter substrate, and a liquid crystal display panel in which liquid crystal is injected between both substrates. Since the liquid crystal display panel is a non-light emitting device, a backlight unit for supplying light is disposed on the rear surface of the thin film transistor substrate. Light transmitted from the backlight unit is adjusted according to the arrangement of liquid crystals.

The backlight unit is divided into an edge type and a direct type according to the position of the light source. The direct type is a structure mainly developed as the size of the liquid crystal display device is enlarged. The direct type is a structure in which one or more light sources are arranged on the lower surface of the liquid crystal display panel to supply light to the liquid crystal display panel.

Recently, as a light source of a direct type backlight unit, LEDs having high luminance and excellent color reproducibility have been used. However, the direct type backlight unit using the LED as a light source has a problem that luminance unevenness is generated in which the arrangement of the LED is recognized by the user.

In order to solve this problem, a transparent plate having a light blocking portion corresponding to the LED is used. However, when the transparent plate is used, some of the light emitted from the LED causes a total reflection in the transparent plate, causing a problem of light loss.

Accordingly, an object of the present invention is to provide a backlight unit having a reduced light loss in a transparent plate and a liquid crystal display including the same.

According to the present invention, an LED circuit board on which an LED is mounted, and a transparent plate which is located above the LED and has a total reflection suppression pattern formed on an exit surface, is provided by the backlight unit. Can be achieved.

It is preferable that the light shielding portion corresponding to the LED is formed on the incident surface of the transparent plate.

The total reflection suppression pattern may include at least one of a prism, embossing, and a V-cut pattern.

Another object of the present invention can be achieved by a liquid crystal display device comprising a liquid crystal display panel and the backlight unit positioned on the rear surface of the liquid crystal display panel.

On the other hand, the above object, according to the invention, characterized in that it comprises an LED circuit board on which the LED is mounted, a transparent plate located on the upper portion of the LED, and an optical film in close contact with the exit surface of the transparent plate It can also be achieved by a backlight unit.

It is preferable that the light shielding portion corresponding to the LED is formed on the incident surface of the transparent plate.

The optical film may be at least one of a diffusion film, a prism film, and a reflective polarizing film.

On the other hand, another object of the present invention can be achieved by a liquid crystal display device comprising a liquid crystal display panel and the backlight unit located on the back of the liquid crystal display panel.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

1 and 2 are an exploded perspective view and a cross-sectional view of a liquid crystal display according to a first embodiment of the present invention. The enlarged transparent plate in the dotted line of Figure 1 is shown upside down the upper and lower transparent plates for convenience of understanding.

The liquid crystal display device 1 includes a liquid crystal display panel 20, a plurality of optical members 30 disposed on the rear surface of the liquid crystal display panel 20, and an LED 51 and an LED disposed over the entire rear surface of the liquid crystal display panel 20. Reflective plate 40 positioned below 51, LED circuit board 52 on which LED 51 is mounted, and transparent plate 60 positioned between LED circuit board 52 and optical member 30. It includes.

 The liquid crystal display panel 20 bonds the thin film transistor substrate 21 on which the thin film transistor is formed, the color filter substrate 22 facing the thin film transistor substrate 21, and the two substrates 21 and 22 to each other, thereby bonding a cell gap. a sealant 23 forming a gap), and a liquid crystal layer 24 positioned between both substrates 21 and 22 and the sealant 23. The liquid crystal display panel 20 adjusts the arrangement of the liquid crystal layer 24 to form a screen, but because it is a non-light emitting device, light must be supplied from the LED 51 located on the rear surface. One side of the thin film transistor substrate 21 is provided with a driver 25 for applying a drive signal. The driver 25 includes a flexible printed circuit board (FPC. 26), a driving chip (27) mounted on the flexible printed circuit board (26), and a circuit board (PCB) connected to the other side of the flexible printed circuit board (26). 28). The driver 25 illustrated represents a chip on film (COF) method, and other known methods such as a tape carrier package (TCP) and a chip on glass (COG) may be used. In addition, the driver 25 may be formed on the thin film transistor substrate 21 during the wiring formation process.

The optical member 30 disposed on the rear surface of the liquid crystal display panel 20 may include a diffusion plate 32, a diffusion film 33, a prism film 34, and a protective film 35.

The diffusion plate 32 and the diffusion film 33 is composed of a base plate and a bead-shaped coating layer formed on the base plate. Light emitted from the transparent plate 60, which will be described later, has less light in the front direction and more light having an angle in the normal direction. The diffusion film 33 changes the light in this normal direction in the front direction according to the refractive effect to increase the front brightness. The diffusion film 33 may be used by overlapping two or three sheets.

The prism film 34 is formed with a triangular prism-shaped prism on an upper surface thereof. The prism film 34 collects light diffused from the diffusion film 33 in a direction perpendicular to the plane of the upper liquid crystal display panel 20. Two prism films 34 are usually used, and the micro prisms formed on each prism film 34 have a predetermined angle. The light passing through the prism film 34 is almost vertically progressed to provide a uniform luminance distribution.

The uppermost protective film 35 protects the prism film 34 that is weak to scratches.

The reflective plate 40 is positioned between the LED 51 and the LED circuit board 52 which will be described later. To this end, a through hole 43 through which the LEDs 51 can pass is formed in the reflector plate 40, and a reflector 41 reflects light emitted from the LEDs 51 toward the liquid crystal display panel 20. Formed.

The light source unit 50 includes a plurality of LEDs 51 for generating light and an LED 51 mounted thereon and includes an LED circuit board 52 having a bar shape.

The direction of the light supplied from the LED 51 can be adjusted in various ways, it is preferable to limit the light emitted from the top as possible. This is because light going straight to the top degrades color uniformity. The LEDs 51 are arranged in a row on the LED circuit board 52. LEDs 51 emitting red, green, and blue, respectively, are arranged in a row on the LED circuit board 52 to provide white light to the liquid crystal display panel 20 by color mixing.

In order to provide white light through color mixing, a space for color mixing is required between the LED 51 and the optical member 30. The transparent plate 60 is located in a space apart from each other and the light shield 62 is attached to the incident surface. The transparent plate 60 may be made of an acrylic resin such as polymethyl methacrylate (PMMA), and may be somewhat thicker than the diffusion plate 32, the diffusion film 33, the prism film 34, and the protective film 35. do.

Although not shown in the drawings, the LED 51 and the transparent plate 60, the transparent plate 60, and the diffusion plate 32 are spaced apart from each other by a supporting part supporting therebetween.

The transparent plate 60 is provided with light blocking portions 61 arranged in a plurality of rows. The light blocking portion 61 is provided on the surface of the transparent plate 60 facing the LEDs 51 in a size similar to that of the LEDs 51 and is positioned above the LEDs 51. The light blocking unit 61 blocks light generated in the vertical direction of the liquid crystal display panel 20 from the LED 51 to improve color uniformity. The light blocking portion 61 may be formed of the same material as the reflecting plate 40, in which case the light incident on the light blocking portion 61 is reflected to enter the reflecting plate 40.

The prism pattern 62 is provided on the exit surface of the transparent plate 60. The prism pattern 62 prevents light loss in which light generated from the LED 51 is totally reflected in the transparent plate 60 so that the light cannot be directed toward the liquid crystal display panel 20. In addition, it performs a light collecting function.

The liquid crystal display panel 20, the optical member 30, the reflector 40, the LED 51, the LED circuit board 52, and the transparent plate 60 described above are attached to the upper chassis 10 and the lower chassis 80. Is accommodated by.

Hereinafter, the reason why the light loss is reduced in the liquid crystal display device 1 according to the present invention will be described with reference to FIG. 3.

First, the reason why light loss occurs in the liquid crystal display device 1 will be described.

When light is incident from an optically dense medium (a material with a high refractive index) to a small medium (a material with a small index of refraction), if the incident angle is above a certain angle (critical angle), the light is completely It is reflected and there is no refraction light. This is total reflection, and the minimum value of the incident angle at which total reflection can occur is called a critical angle.

The light generated by the LED 51 is directly incident on the transparent plate 60 or reflected on the reflecting plate 40, incident on the transparent plate 60, or reflected by the light blocking unit 61, and then again reflected on the reflecting plate 40. As a result, the light is incident on the transparent plate 60. Part of the light is reflected from the incident surface of the transparent plate 60 and the remaining light is moved to the exit surface. The light moved to the exit surface is supplied to the liquid crystal display panel 20 through the optical member 30 after passing through the exit surface.

The transparent plate 60 made of acrylic resin such as polymethyl methacrylate (PMMA) has a higher density than air, so that light having an incident angle with respect to the exit surface is greater than the total reflection critical angle among the light incident in the transparent plate 60, results in total reflection. It does not pass through the exit plane and is reflected back to the entrance plane. Some of the reflected light passes through the incident surface to the reflecting plate and the remaining light undergoes total reflection at the incident surface. In this process, some of the light emitted from the LED 51 passes through the exit surface and is not supplied to the liquid crystal display panel 20.

In the present invention, by forming a prism pattern 62 functioning as a prism film as a pattern for suppressing total reflection on the exit surface of the transparent plate 60 to reduce the light loss due to the total reflection generated in the transparent plate 60 Improve brightness.

3, the light blocking portion 61 is provided on the incident surface of the transparent plate 60, and the prism pattern 62, which is a total reflection suppression pattern, is formed on the exit surface.

In this configuration, the light generated from the LED 51 and incident on the transparent plate 60 reaches the prism pattern 62 through the transparent plate 60. In this case, when the incident angle of the light reaching the prism pattern 62 is less than or equal to the total reflection threshold angle, total reflection does not occur and thus passes through the prism pattern 62. When the incident angle is an angle θ1 equal to or greater than the total reflection critical angle, it is reflected and incident on another adjacent prism pattern 62. In this case, the incident angle θ2 becomes less than or equal to the total reflection critical angle and passes through the prism pattern 62 to the liquid crystal display panel 20. Will proceed. As a result, the light loss due to total reflection at the exit surface of the transparent plate 60 is reduced, thereby improving luminance.

4 is a perspective view of an essential part of a liquid crystal display according to a second exemplary embodiment of the present invention.

In this embodiment, the embossing pattern 63 is provided on the exit surface of the transparent plate 60 as a pattern for suppressing total reflection occurring in the transparent plate 60. The embossing pattern 63 also forms a traveling path for the light incident on the exit surface of the transparent plate 60 to be less than or equal to the total reflection critical angle so that total reflection does not occur and passes through the embossing pattern 63 so that the liquid crystal display panel 20 To proceed. As a result, the total reflection due to the exit surface of the transparent plate 60 is suppressed, thereby reducing the light loss, thereby improving luminance.

5 is a perspective view of an essential part of a liquid crystal display according to a third exemplary embodiment of the present invention.

In this embodiment, a V-cut pattern 64 is provided on the exit surface of the transparent plate 60 as a pattern for suppressing total reflection occurring in the transparent plate 60. The V-cut pattern 64 also suppresses total reflection at the exit surface of the transparent plate 60, thereby reducing light loss and improving luminance.

The total reflection suppression pattern of the present invention described in the above embodiments may be variously modified. In other words, the light incident on the exit surface of the transparent plate 60 may be deformed into various shapes such as to have a diffusion pattern having a random roughness such that the light is below a critical angle. In addition, both the prism pattern, the embossing pattern, and the V-cut pattern may be formed on the exit surface of the transparent plate 60, and two patterns may be formed.

6 is a cross-sectional view illustrating main parts of a liquid crystal display according to a fourth exemplary embodiment of the present invention.

In the present embodiment, unlike the previous embodiment, the diffusion film 71 is provided to be in close contact with the emission surface of the transparent plate 60 instead of forming the total reflection suppression pattern on the transparent plate 60. When the diffusion film 71 made of a material having a greater density than the transparent plate 60 is brought into close contact with the transparent plate 60, the light incident on the transparent plate 60 passes through the transparent plate 60 without being totally reflected. The diffusion film 71 diffuses toward the liquid crystal display panel. Therefore, the light loss due to total reflection in the transparent plate 60 may be reduced, thereby improving luminance.

7 is a perspective view of an essential part of a liquid crystal display according to a fifth exemplary embodiment of the present invention.

In this embodiment, the prism film 73 is in close contact with the exit surface of the transparent plate 60. Even with the prism film made of a material having a higher density than the transparent plate 60, the light loss due to total reflection in the transparent plate 60 is reduced, thereby improving luminance.

Meanwhile, although not shown, in the sixth embodiment, the reflective polarizing film may be brought into close contact with the emission surface of the transparent plate 60 to reduce light loss due to total reflection, thereby improving luminance. Reflective polarizing film is DBEF (dual brightness enhancement film). A cholesteric liquid crystal film (CLCF) or a diffuse reflective polarizer film (DRPF) may be used.

In the fourth and the sixty-fifth embodiments, a single diffusion film 71, a prism film 73, or a reflective polarizing film (not shown) is used as the optical film, but is not limited thereto. If necessary, the diffusion film 71, the prism film 73, the reflective polarizing film, and other films can be used in close contact with the transparent plate 60 together. In addition, it is also possible to use the optical film attached to the transparent plate 60 using an adhesive.

In addition, the present invention described above may be variously modified. If necessary, the liquid crystal display device 1 may be provided by omitting the optical member 30 in the above embodiment, and a diffusion pattern or a light collecting pattern may be formed on the incident surface of the transparent plate 60. . In addition, instead of bringing the optical film into close contact with the exit surface of the transparent plate 60, it is also possible to form a resin layer capable of performing the function of the optical film to suppress total reflection.

 Thus, while some embodiments of the invention have been shown and described, it will be apparent to those skilled in the art that the embodiments may be modified without departing from the spirit or spirit of the invention. There will be. It is intended that the scope of the invention be defined by the claims appended hereto and their equivalents.

As described above, according to the present invention, there is provided a backlight unit and a liquid crystal display device which can improve brightness by reducing light loss.

Claims (8)

An LED circuit board on which an LED is mounted; The backlight unit is positioned above the LED, and comprises a transparent plate having a total reflection suppression pattern formed on an exit surface. The method of claim 1, The light blocking unit corresponding to the LED is formed on the incident surface of the transparent plate. The method of claim 1, The total reflection suppression pattern may include at least one of a prism, embossing, and a V-cut pattern. A liquid crystal display panel; A liquid crystal display device comprising a backlight unit according to any one of claims 1 to 3 positioned on a rear surface of the liquid crystal display panel. An LED circuit board on which an LED is mounted; A transparent plate positioned above the LED; And a optical film in close contact with the exit surface of the transparent plate. The method of claim 5, The light blocking unit corresponding to the LED is formed on the incident surface of the transparent plate. The method of claim 5, The optical film is a backlight unit, characterized in that at least any one of a diffusion film, a prism film, a reflective polarizing film. A liquid crystal display panel; A liquid crystal display device comprising a backlight unit according to any one of claims 5 to 7 positioned on a rear surface of the liquid crystal display panel.

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