KR20100072655A

KR20100072655A - Light guide plate and backlight unit for liquid crystal display device using the same

Info

Publication number: KR20100072655A
Application number: KR1020080131129A
Authority: KR
Inventors: 정상원
Original assignee: 엘지디스플레이 주식회사
Priority date: 2008-12-22
Filing date: 2008-12-22
Publication date: 2010-07-01

Abstract

The present invention relates to a backlight unit for a liquid crystal display device, and more particularly, to a light guide plate of a backlight unit.

A feature of the present invention is to form the protrusion of the light guide plate to have an inclined surface at a predetermined portion from the light incident portion to the light incident portion.

As a result, the light incident to the light guide plate is totally reflected inside the light guide plate by the inclined surface of the light guide plate in the process of spreading the light incident on the inside of the light guide plate evenly spreading from the light incident part of the light guide plate to the light incident part by several total reflections. Therefore, it is possible to prevent the light concentration phenomenon in which light is concentrated at angled edges of the existing protrusion.

As a result, light leakage due to the protrusion of the light guide plate can be prevented, thereby improving luminance and color uniformity of the liquid crystal display device.

Description

Light guide plate and backlight unit for liquid crystal display device using the same}

In line with the recent information age, the display field has also been rapidly developed, and a liquid crystal display device (FPD) is a flat panel display device (FPD) having advantages of thinning, light weight, and low power consumption. LCD, plasma display panel device (PDP), electroluminescence display device (ELD), field emission display device (FED), etc. : It is rapidly replacing CRT.

Among them, liquid crystal display devices are most actively used in the field of notebooks, monitors, TVs, etc. due to their excellent contrast ratio and high contrast ratio. The liquid crystal display device is a device that does not have its own light emitting element. Will require a light source.

As a result, a backlight unit having a lamp is provided on the rear side to irradiate light toward the front of the liquid crystal panel, thereby realizing an image of identifiable luminance.

1 is an exploded perspective view of a general liquid crystal display device.

As illustrated, a general liquid crystal display module includes a liquid crystal panel 10, a backlight unit 20, a support main 30, a cover bottom 50, and a top cover 40.

The liquid crystal panel 10 is a part that plays a key role in image expression and is composed of first and second substrates 12 and 14 bonded to each other with a liquid crystal layer interposed therebetween. The printed circuit board 17 is connected to one side edge of the liquid crystal panel 10 through the connection member 15.

In addition, the backlight unit 20 is provided behind the liquid crystal panel 10.

In this case, the backlight unit 20 includes a lamp 24 arranged along the longitudinal direction of at least one edge of the support main 30, a white or silver reflecting plate 22 seated on the cover bottom 50, and the reflecting plate. Seated on 22, lamp 24 includes a light guide plate 26 on one side and a plurality of optical sheets 28 interposed thereon.

The liquid crystal panel 10 and the backlight unit 20 have a top cover 40 surrounding the top edge of the liquid crystal panel 10 and a back surface of the backlight unit 20 in a state where the edges are surrounded by the support main 30 having a rectangular frame shape. Cover cover 50 to cover each is coupled in front and rear are integrated through the support main 30 as a medium.

As a result, the light emitted from the lamp 24 is incident on the light incident part of the light guide plate 26 and refracted in the direction of the liquid crystal panel 10, and processed to a high quality of uniform brightness while passing through the plurality of optical sheets 28. The liquid crystal panel 10 is incident on the liquid crystal panel 10.

As a result, the liquid crystal panel 10 displays an image to the outside.

On the other hand, at least two edges facing each other of the light guide plate 26 are provided with protrusions 26a, and the light guide plate 26 has a light guide plate fixing jaw (hereinafter, fixed jaw) formed at the support main 30 with the protrusions 26a. In this case, it is possible to prevent flow due to external impact or vibration.

However, the light leakage phenomenon occurs due to the protrusion 26a of the light guide plate 26.

In more detail, the light incident into the light guide plate 26 through the light incidence part of the light guide plate 26 is spread evenly while traveling in the direction of the light incidence part from the light incidence part of the light guide plate 26 by a plurality of total reflections. Light also spreads to the protrusion 26a of the light guide plate 26.

At this time, the light spread to the protrusions 26a of the light guide plate 26 is concentrated at the angular corners of the protrusions 26a, so that light concentration occurs, and the concentrated light causes strong light leakage.

Such light leakage can be visually confirmed as shown in FIG. 2, resulting in deterioration of the quality of the liquid crystal display device such as a decrease in luminance and color uniformity.

The present invention has been made to solve the above problems, and a first object of the present invention is to prevent light leakage of the liquid crystal display due to the protrusion of the light guide plate.

For this reason, the second object is to improve the luminance and color uniformity of the liquid crystal display device.

In order to achieve the object as described above, the present invention is a reflection plate; A lamp arranged on one side of the reflector; A light guide plate including a light incident portion corresponding to the lamp and a plurality of protrusions on both sides perpendicular to the light incident portion; It includes a plurality of optical sheets seated on the light guide plate, the plurality of protrusions provides a backlight unit for a liquid crystal display device is formed to have an inclined surface at a predetermined portion from the light incident portion to the light incident portion of the light guide plate.

In this case, the light guide plate may include a light incident part to which light is incident, both side surfaces facing the light incident part, and an upper surface on which the light incident part and light are emitted, and a lower surface facing the reflecting plate, and the protrusion part is an upper surface of the light guide plate. And a second surface facing in parallel with the first surface and the first surface extending from the second surface, and third to fifth surfaces forming a side surface perpendicular to the first and second surfaces, and the fifth surface being the mouth. It consists of an inclined surface which is inclined at an angle toward the direction from the miner to the incoming light part.

Herein, a plurality of protrusions are formed along both sides of the light guide plate at predetermined intervals, and a pattern is formed on a lower surface of the light guide plate, and the pattern is an elliptical pattern or a polygon pattern. , A hologram pattern, a prism pattern, or a lenticular pattern.

In addition, the present invention is provided with a light incident part incident light and both sides and the upper surface facing the incident light and the light exiting and a lower surface facing the reflecting plate is provided, the second side extending from the upper surface A first face and a second face facing in parallel with the first face, and a plurality of protrusions each having a third to fifth face which is lateral to and perpendicular to the first and second face, wherein the fifth face comprises: Provided is a light guide plate for a liquid crystal display device which is an inclined surface that is inclined at a predetermined angle from the light incident part toward the light incident part.

As described above, according to the present invention, a feature of the present invention is that the protrusion of the light guide plate is formed to have an inclined surface at a predetermined portion from the light incidence part to the light incidence part, so that the light incident into the light guide plate is caused by the total reflection of the light guide plate. In the process of spreading the light from the miner to the light incident part, the light spread to the protrusion of the light guide plate is totally reflected to the inside of the light guide plate by the inclined surface of the light guide plate, thereby preventing the light concentration phenomenon in which light is concentrated at the angular edge of the existing protrusion. It can be effective.

As a result, light leakage due to the protrusion of the light guide plate can be prevented, thereby improving the luminance and color uniformity of the liquid crystal display device.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

The present invention can be applied to mobile phones, digital multimedia broadcasting (DMB) terminals, small liquid crystal display devices mounted on PDAs (personal digital assistants) and digital cameras, and large liquid crystal display devices used in TVs or computer monitors. In the following, a small liquid crystal display manufactured to 5 inches or less will be described as an example.

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

As shown, the liquid crystal display device includes a liquid crystal panel 110, a backlight unit 120, a support main 130, a cover bottom 150, and a top cover 140.

First, the liquid crystal panel 110 plays a key role in image expression, and includes the first and second substrates 112 and 114 bonded to each other with the liquid crystal layer interposed therebetween.

In this case, under the premise of an active matrix method, although a plurality of gate lines and data lines are intersected on the inner surface of the first substrate 112, which is commonly referred to as a lower substrate or an array substrate, pixels are defined. Thin film transistors (TFTs) are provided at each crossing point and are connected one-to-one with the transparent pixel electrodes formed in each pixel.

In addition, the inner surface of the second substrate 114 called the upper substrate or the color filter substrate may correspond to each pixel, for example, a color filter of red (R), green (G), and blue (B) color, and each of them. A black matrix covering the non-display elements such as gate lines, data lines, and thin film transistors is provided. In addition, a transparent common electrode covering them is provided.

The printed circuit board 117 is connected to at least one edge of the liquid crystal panel 110 via a connection member 115 such as a flexible circuit board, and thus the side surface or cover cover 150 of the support main 130 is modularized. It is bent to the back and adheres tightly.

Although not clearly shown in the drawings, upper and lower alignment layers (not shown) for determining the initial molecular alignment direction of the liquid crystal are interposed between the two substrates 112 and 114 of the liquid crystal panel 110 and the liquid crystal layer. In order to prevent leakage of the liquid crystal layer filled therebetween, a seal pattern is formed along edges of both substrates 112 and 114.

In this case, polarizers (not shown) are attached to outer surfaces of the first and second substrates 112 and 114, respectively.

A backlight unit 120 for supplying light is provided on a rear surface of the liquid crystal panel 110 such that a difference in transmittance of the liquid crystal panel 110 is expressed to the outside.

The backlight unit 120 includes a lamp 124 arranged along at least one edge length direction of the support main 130, a white or silver reflecting plate 122 mounted on the cover bottom 150, and a reflecting plate ( 122 includes a light guide plate 126 seated on and a plurality of optical sheets 128 interposed thereon.

Although not shown in the drawings, the light shielding tape may further include a light shielding tape between the plurality of optical sheets 128 and the liquid crystal panel 110 to prevent light from leaking to portions outside the screen display area of the liquid crystal panel 110.

In addition, a lamp guide for guiding the lamp 124 is further provided. The lamp guide surrounds the upper and lower sides of the lamp 124 with the inner side facing the light guide plate 126 open and the light, together with the protection of the lamp 124. Is concentrated in the direction of the light guide plate 126.

In this case, as the light source, the lamp 124 may be a fluorescent lamp such as a cold cathode fluorescent lamp or an external electrode fluorescent lamp. Alternatively, in addition to the fluorescent lamp, a light-emitting diode lamp may be used as the lamp 124. When the light-emitting diode lamp is used, the lamp guide may be omitted.

At this time, the light guide plate 126 evenly spreads the light incident from the lamp 124 into the light guide plate 126 while propagating the light from the light guide plate 126 by a plurality of total reflections. To provide.

The light guide plate 126 is formed with a plurality of protrusions 160 spaced apart at regular intervals along the length direction of both edges of the light guide plate 126 facing each other, and the protrusions 160 are incident from the light incident part of the light guide plate 126. The width of the inclined surface is reduced to a predetermined angle toward the direction toward. We will look into this in more detail later.

In addition, the reflector plate 122 is positioned on the rear surface of the light guide plate 126 to improve the brightness of the light by reflecting the light passing through the rear surface of the light guide plate 126 toward the liquid crystal panel 110.

The plurality of optical sheets 128 on the light guide plate 126 include a diffusion sheet and at least one light collecting sheet.

Here, the diffusion sheet is positioned directly on the light guide plate 126, and serves to adjust the direction of light so that the light propagates toward the light collecting sheet while dispersing light incident through the light guide plate 126.

The light diffused through the diffusion sheet by the light collecting sheet is focused in the direction of the liquid crystal panel 110. As a result, the light passing through the light collecting sheet is almost perpendicular to the liquid crystal panel 110.

The liquid crystal panel 110 and the backlight unit 120 are modularized through the top cover 140, the support main 130, and the cover bottom 150. The top cover 140 is the top and side surfaces of the liquid crystal panel 110. A rectangular frame having a cross section bent in a shape of “a” so as to cover an edge thereof is configured to open an entire surface of the top cover 140 to display an image implemented in the liquid crystal panel 110.

In addition, the cover bottom 150 on which the liquid crystal panel 110 and the backlight unit 120 are mounted, and which is the basis for assembling the entire structure of the LCD device module, has a rectangular plate shape and bends the edges at both sides thereof in a predetermined height at a predetermined height. Configure.

A support main 130 having a rectangular frame shape seated on the cover bottom 150 and surrounding the edges of the liquid crystal panel 110 and the backlight unit 120 is combined with the top cover 140 and the cover bottom 150.

In this case, stepped light guide plate fixing jaws (hereinafter, referred to as fixing jaws: 131) are formed on upper surfaces of both edges of the support main 130.

Here, the top cover 150 may be referred to as a case top or a top case, the support main 130 may be referred to as a guide panel or a main support, and a mold frame, and the cover bottom 150 may be referred to as a bottom cover.

Meanwhile, the backlight unit 120 having the above-described structure is called a side light method, and a plurality of lamps 124 may be arranged in a plurality of layers along an inner length direction of one edge of the support main 130. It is also possible to arrange them side by side along the inner longitudinal direction of both edges of the main 130 facing each other.

4 is a schematic cross-sectional view of some cross-section of FIG. 3 modularized.

As illustrated, the light guide plate 126 including the reflector plate 122 and the protrusion 160, a lamp (124 of FIG. 3) positioned on one side of the light guide plate 126, and a plurality of optical parts on the light guide plate 126. The sheets 128 form a stacked backlight unit.

In addition, the liquid crystal panel 110 having a liquid crystal layer (not shown) interposed therebetween is disposed between the backlight unit and the first and second substrates 112 and 114, and the first and second substrates 112 and 114. On each of the outer surfaces of), polarizing plates 119a and 119b for selectively transmitting only specific light are attached.

The backlight unit and the liquid crystal panel 110 have an edge surrounded by the support main 130, and the cover bottom 150 is coupled to the rear surface thereof, and the top cover 140 covering the upper edge and the side of the liquid crystal panel 110. Is coupled to the support main 130 and cover bottom 150.

At this time, the stepped light guide plate fixing jaw (hereinafter, referred to as fixing jaw: 131) is formed on the upper surface of both edges of the support main 130, and the protrusion 160 of the light guide plate 126 is fixed to the fixing jaw 131. do.

Thus, the position of the light guide plate 126 is fixed.

Therefore, the light emitted from the lamp 124 is incident on the light incident part of the light guide plate 126 and refracted in the direction of the liquid crystal panel 110, and processed into a uniform high quality while passing through the plurality of optical sheets 128 and then the liquid crystal. The light is incident on the panel 110, and the liquid crystal panel 110 may display a high brightness image by using the same.

Particularly, in the present invention, the protrusion 160 of the light guide plate 126 is formed of an inclined surface whose width decreases at a predetermined angle toward the direction from the light incident part of the light guide plate 126 toward the light incident part in plan view. The light condensation phenomenon, in which light is concentrated, may be prevented.

As a result, light leakage may be prevented to improve luminance and color uniformity of the liquid crystal display. This will be described in more detail with reference to FIG. 5.

5 is a perspective view schematically illustrating a light guide plate according to an embodiment of the present invention.

As shown, the light guide plate 126 is a plastic material such as polymethylmethacrylate (PMMA) or polycarbonate (PC), which is an acrylic transparent resin, which is one of transparent materials capable of transmitting light. It is manufactured in flat type by series.

Here, PMMA is an acrylic resin, which is excellent in transparency, weather resistance and colorability, and induces light diffusion when light is transmitted.

The light guide plate 126 has a light incident surface 126a corresponding to the lamp 124 of FIG. 3, an incoming light incident surface 126b on the opposite side thereof, and an upper surface 126c which connects the light incident surface and the incoming light incident surface and emits light. And a lower surface 126d facing the reflective plate 122 of FIG. 4 and both side surfaces 126e and 126f facing each other.

At this time, both side surfaces 126e and 126f of the light guide plate 126 are formed with a plurality of protrusions 160 spaced apart at regular intervals along the length direction, and the protrusions 160 are formed on the upper surface 126c of the light guide plate 126. The first surface 161 and the second surface 163 facing in parallel with the first surface 161 and the third to fifth sides lateral to the first and second surfaces 161 and 163. Faces 165, 167, and 169.

The third surface 165 of the protrusion 160 faces the light incident surface 126a of the light guide plate 126 and the fifth surface 169 faces the light incident surface 126b of the light guide plate 126. The fifth surface 169 may be formed as an inclined surface that is inclined at an angle toward the direction from the light incident surface 126a toward the light incident surface 126b.

Accordingly, the light guide plate 126 in the process of spreading the light incident on the light guide plate 126 through the light incident portion of the light guide plate 126 evenly spreads from the light incident portion of the light guide plate 126 toward the incoming light incident portion by a plurality of total reflections. The light propagated to the protrusion 160 may be totally reflected inside the light guide plate 126 by the fifth surface 169 of the protrusion 160.

Thus, it is possible to prevent the light concentration phenomenon in which light is concentrated at the angular corner of the existing protrusion (26a of FIG. 1), it is possible to prevent the light leakage occurs.

The protrusion 160 of the light guide plate 126 is made of the same material as the light guide plate 126.

Meanwhile, in the drawings and the description, the protrusions 160 are formed to face each other at both side surfaces 126e and 126f of the light guide plate 126, but the protrusions 160 may be alternately formed so as not to face each other.

The light guide plate 126 may include a pattern of a specific shape on the rear surface to supply a uniform surface light source.

Here, the pattern may be configured in various ways, such as an elliptical pattern, a polygonal pattern, a hologram pattern, and the like to guide light incident to the light guide plate 126. The pattern is formed on the lower surface of the light guide plate 126 by a printing method or an injection method.

6A and 6B are plan views schematically illustrating a protrusion part of the light guide plate of the present invention fixed to the fixing jaw of the support main.

As shown, the fixing jaw 131 is formed on the edge of the support main 130, the fixing jaw 131 is a part of the upper surface of the edge of the support main 130 in the form of a stepped cross-sectional shape, It is configured to form a rectangular shape formed along the longitudinal longitudinal direction of the support main 130 in a plane.

The protrusion 160 of the light guide plate 126 is fixed to the fixing jaw 131 of the support main 130, and the protrusion 160 is formed on the upper surface (126c of FIG. 5) of the light guide plate 126 as described above. An extended first face (161 in FIG. 5) and a second face (163 in FIG. 5) facing in parallel with the first face (161 in FIG. 5), and first and second faces (161, 163 in FIG. 5). The third to fifth surfaces 165, 167, and 169 that form a side surface perpendicular to the lateral plane.

In this case, the fifth surface 169 may be formed as an inclined surface that is inclined at a predetermined angle from the light incident surface (126a of FIG. 5) toward the light incident surface (126b of FIG. 5).

Accordingly, the light incident on the light guide plate 126 through the light incident part of the light guide plate 126 is uniformly spread from the light incident part of the light guide plate 126 toward the incoming light incident part by a plurality of total reflections. Light propagated to the protrusion 160 is totally reflected inside the light guide plate 126 by the fifth surface 169 of the light guide plate 126.

As a result, it is possible to prevent the light concentration phenomenon in which light is concentrated at angled corners of the existing protrusion 160, and as shown in FIG. 7, the light leakage is significantly reduced.

As described above, the protrusion 160 of the light guide plate 126 is formed to have an inclined surface at a predetermined portion from the light incidence part to the light incident part, so that light incident into the light guide plate 126 is reflected by a plurality of total reflections of the light guide plate 126. As the light spreads from the light incident part toward the light incident part and spreads evenly to the protrusion 160 of the light guide plate 126 in the process of being evenly spread, the total protrusion of the light exits the inside of the light guide plate 126 by the inclined surface of the light guide plate 126. There is an effect that can prevent the light concentration phenomenon that the light is concentrated in the angled corner of 26a) of FIG.

As a result, light leakage due to the protrusion 160 of the light guide plate 126 may be prevented, thereby improving brightness and color uniformity of the liquid crystal display.

The present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the present invention.

1 is an exploded perspective view of a general liquid crystal display device.

Figure 2 is a photograph showing a light leakage phenomenon occurring in the prior art.

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

4 is a schematic cross-sectional view of a partial cross section of FIG. 3 modularized;

Figure 5 is a perspective view schematically showing the appearance of a light guide plate according to an embodiment of the present invention.

6A to 6B are plan views schematically showing a state in which the protrusion of the light guide plate of the present invention is fixed to the fixing jaw of the support main;

Figure 7 is a photograph showing the appearance of no light leakage phenomenon in accordance with an embodiment of the present invention.

Claims

A reflector;

A lamp arranged on one side of the reflector;

A light guide plate including a light incident portion corresponding to the lamp and a plurality of protrusions on both sides perpendicular to the light incident portion;

A plurality of optical sheets seated on the light guide plate

Wherein the plurality of protrusions are formed to have an inclined surface at a predetermined portion from the light incidence part of the light guide plate to the light incidence part.

The method of claim 1,

The light guide plate may include a light incident part to which light is incident, both side surfaces facing the light incident part, and an upper surface on which the light incident part and light are emitted, and a lower surface facing the reflecting plate.

The method of claim 2,

The protruding portion includes a first surface extending from the upper surface of the light guide plate and a second surface facing in parallel with the first surface, and third to fifth surfaces perpendicular to the first and second surfaces. And the fifth surface is an inclined surface that is inclined at an angle toward the direction from the light incident portion toward the light incident portion.

The method of claim 1,

And a plurality of protrusions formed at regular intervals along both sides of the light guide plate.

The method of claim 1,

A pattern is formed on a lower surface of the light guide plate, and the pattern is an elliptical pattern, a polygon pattern, a hologram pattern or a prism pattern, a lenticular pattern. A backlight unit for a liquid crystal display device which is one selected from the forms.

It is provided with a light incident part to which light is incident, both sides and the incoming light incident part and the upper surface and the lower surface facing the reflecting plate, the light is emitted,

A plurality of first and second surfaces extending parallel to the first and second surfaces extending from the upper surface, and third to fifth surfaces forming side surfaces perpendicular to the first and second surfaces. Overhang

And the fifth surface is an inclined surface that is inclined at an angle toward the direction from the light incident portion toward the light incident portion.