KR20070071295A - Back-light unit and liquid crystal display device using thereof - Google Patents

Abstract

A backlight unit and an LCD(Liquid Crystal Display) using the same are provided to prevent bright line from being generated on an image display part of the LCD, by forming a protrusion at a corner of a light guiding plate so that the protrusion scatters a light generated from a lamp when the light is incident onto the corner of the light guiding plate. A lamp(201) generates light. A light guiding plate(204) guides the light generated from the lamp. The light guiding plate has a protrusion(205a) formed at a corner of an incident portion thereof. A lamp housing member(202) encloses the lamp, and reflects the light generated from the lamp. A reflecting plate(203) is disposed below the light guiding plate to reflect the light generated from the lamp. An optical sheet uniformly transfers the light guided by the light guiding plate to a space above the light guiding plate.

Description

BACK-LIGHT UNIT AND LIQUID CRYSTAL DISPLAY DEVICE USING THEREOF}

1 is a perspective view showing the configuration of a conventional backlight device

2 is a cross-sectional view showing the configuration of a conventional backlight device.

3 is a plan view showing a bright line generated in a conventional liquid crystal display device

4 is a cross-sectional view illustrating a reason why bright lines are generated in a conventional backlight device.

5 is a cross-sectional view showing a reason why generation of bright lines is prevented in the first embodiment of the present invention.

6 is a cross-sectional view showing the reason why generation of bright lines is prevented in the second embodiment of the present invention.

7 is a cross-sectional view showing the reason why generation of bright lines is prevented in the third embodiment of the present invention.

8 is a cross-sectional view showing the reason why generation of bright lines is prevented in the fourth embodiment of the present invention.

** Explanation of symbols for main parts of drawings **

201: Lamp

202: lamp housing

203: reflector

205a, 205b: protrusions having a rectangular cross section

206a, 206b: curved protrusions in cross section

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight device and a liquid crystal display device using the same, and more particularly, to a technique of preventing bright lines from occurring in an image display unit of a liquid crystal display device by forming protrusions at edge portions of the light guide plate constituting the backlight device.

Recently, the importance of the display device as a visual information transmission medium has been further emphasized, and many kinds of competitive display devices have been developed. Among such various types of display devices, in order to occupy a major position in the future, it is necessary to satisfy requirements such as low power consumption, thinness, light weight, and high quality.

 Liquid crystal display (LCD), the flagship product of flat panel displays (FPDs), is not only capable of satisfying these conditions but also mass-produced. It is widely used in various applications and is positioned as a core display device that can replace the market dominated by a conventional cathode ray tube (CRT).

The liquid crystal display device includes a liquid crystal panel comprising an upper plate called a thin film transistor array substrate, a lower plate called a color filter substrate, and a liquid crystal filled therebetween.

In this case, N × M pixels are arranged vertically and horizontally on the upper plate, and each unit pixel is formed with a thin film transistor for transmitting an image signal and a pixel electrode for forming an electric field. A color filter pattern and a black mattress are formed on the lower plate, and in the case of the vertical electric field method, a common electrode corresponding to the pixel electrode is formed. The liquid crystal filled between the upper plate and the lower plate is a material having optical anisotropy, and varies in arrangement depending on an electric field formed between the pixel electrode and the common electrode, thereby causing a change in transmittance according to polarization characteristics of light.

However, since the liquid crystal display is a display device having non-light emitting characteristics, a separate external light source for irradiating light is required in addition to the liquid crystal panel. In particular, in the case of a transmissive liquid crystal display device, a separate backlight device for generating light on the rear surface of the liquid crystal panel and inducing the generated light toward the liquid crystal panel is necessary.

As the backlight device, an edge type backlight device having lamps 106 disposed on one side or both sides of a liquid crystal panel is generally used. The structure thereof will be described with reference to FIG. 1, which is an exploded view showing a general edge type backlight device. do.

As shown in FIG. 1, a general edge type backlight device includes a lamp formed on both sides of a liquid crystal panel to generate light, a light guide plate formed at a lower portion of the liquid crystal panel to guide light generated from the lamp toward the liquid crystal panel, and It consists of a lamp housing protecting the lamp and formed on the side of the lamp, and an optical sheet formed on the light guide plate to uniformly transmit light toward the liquid crystal panel. In this case, the optical sheet is a diffusion sheet 111 for uniformly diffusing the light from the light guide plate, and a prism positioned on the diffusion sheet 111 to collect and diffuse the light diffused from the diffusion portion to the liquid crystal panel. The sheet 112 and the protective sheet 113 serves to protect the prism sheet 112 on the prism sheet 112. The bottom cover of the reflective plate protects the liquid crystal display and constitutes an exterior.

Referring to FIG. 2, the cross-sectional structure of a general edge type backlight device is as follows.

As shown in FIG. 2, in the edge type backlight device, lamps are positioned at both sides of the light guide plate, a lamp housing is positioned around the lamp, and a reflecting plate is positioned at the bottom of the light guide plate, and is disposed on an upper surface of the light guide plate. An optical sheet composed of a diffusion sheet, a prism sheet, and a protective sheet is located.

In the liquid crystal display device having the edge type backlight device, bright lines may occur in the image display unit.

As shown in FIG. 3, the bright line 120 appears in parallel with the longitudinal direction of the backlight around the backlight of the image display unit 119 of the liquid crystal display device 121. The bright line 120 is a phenomenon in which luminance is higher than that of surrounding pixels, which is more remarkably observed in an observer's eye than a dark spot, which is a major cause of deterioration of image quality of the display element.

The cause of the bright line will be described with reference to FIG. 4.

FIG. 4 is an enlarged view of an area where a lamp is located among the cut planes of AA ′ of FIG. 3.

As shown in FIG. 4, a lamp 106 wrapped in a lamp housing 105 is provided at an outer portion of the liquid crystal panel, and a light guide plate 110 is provided adjacent to the lamp 106. Below the reflective plate 109 is provided. In the drawings, the distance between the lamp housing 105 and the light guide plate 110 and the reflector plate 109 and the light guide plate 110 is widely indicated. This is not formed.

 Looking at the path of light in the structure, the light generated from the lamp 106 is reflected directly to the light 118 and the reflecting plate 109 which is incident directly to the vertical plane of the light guide plate 110 and then incident to the vertical plane of the light guide plate 110. After the light 117 and the reflecting plate 109 or the lamp housing 105 is reflected, the light 117 may be divided into light 115 and 116 incident on the horizontal plane of the light guide plate 110. The light 115 and 116 incident on the horizontal plane of the light guide plate after being reflected by the reflector plate 109 or the lamp housing 105 are again incident on the light horizontal plane of the light guide plate 116 and the light 115 incident on the lower horizontal plane. Divided by).

In this case, it can be seen that each light path is changed at a boundary between the air layer having the refractive index of 1 and the light guide plate 110 having the refractive index greater than 1. In addition, at the boundary, not only the refraction of the light but also the reflection of the light occurs. It is generally known that the smaller the angle of incidence, the more the reflection characteristic is superior to the light refraction characteristic.

First, the light 118 incident directly to the vertical plane of the light guide plate from the lamp is refracted by the vertical plane of the light guide plate 110 and reflected back from the horizontal plane of the light guide plate 110 to be supplied toward the liquid crystal panel. In this case, in the horizontal plane of the light guide plate 110, the incident angle is small, so that reflection is superior to refraction.

Secondly, the light 117 reflected on the reflecting plate and then incident on the vertical plane of the light guide plate is refracted at the vertical plane of the light guide plate and then supplied to the liquid crystal panel.

Third, the light 115 reflected by the reflecting plate and then incident on the lower horizontal plane of the light guide plate is refracted by the lower horizontal plane of the light guide plate and then supplied to the liquid crystal panel.

Fourth, the light 116 that is incident on the upper horizontal plane of the light guide plate after being reflected by the lamp housing is refracted in the upper horizontal plane and the lower horizontal plane of the light guide plate. Is supplied to the side.

 At this time, the important thing is the incident angle of light supplied to the liquid crystal panel.

The first 118 and the second light 117 has a small incident angle incident toward the liquid crystal panel, whereas the third 115 and the fourth light 116 have relatively large incident angles. As described above, the light 117 and 118 having a small incident angle exist at the same time while the components 117a and 118a transmitted to the liquid crystal panel and the reflected components 117b and 118b maintain a constant ratio. 116 is very small compared to the component through which the reflected component (not shown) is transmitted so that most of the light is refracted and transmitted. Therefore, bright lines are generated in the image display unit of the liquid crystal panel along the paths of the third and fourth lights 115 and 116.

The bright line generated by the above causes is a major cause of deterioration of the image quality of the liquid crystal display device, and if this is severe, it has to be judged as a defective product, which leads to a decrease in yield.

Other objects and features of the present invention will be described in the configuration and claims of the invention described below.

An object of the present invention is to prevent the occurrence of bright lines in the image display unit by forming a protrusion on the light guide plate of the backlight device constituting the liquid crystal display element.

By forming the protrusion, the light path generated in the lamp is separated in various ways, thereby dispersing the light concentrated at the position where the bright line is generated in the conventional liquid crystal display.

It is an object of the present invention to improve the image quality of the liquid crystal display device by preventing the occurrence of the bright line, and to increase the production yield by reducing the defective rate.

Liquid crystal display device manufacturing apparatus of the present invention for achieving the above object is a lamp for generating light; A light guide plate inducing light generated by the lamp and having a protrusion formed at an edge portion at which the light is incident; A lamp housing surrounding and protecting the lamp and reflecting light generated from the lamp; A reflection plate reflecting light generated by the lamp and formed under the light guide plate; And an optical sheet for uniformly transmitting the light guided by the light guide plate toward the light guide plate.

The protrusion formed on the light guide plate serves to prevent a bright line from being generated by dispersing the path when the light generated from the lamp is incident on the edge of the light guide plate.

At this time, the protrusions may be formed in various embodiments, and each embodiment will be described in detail below.

A first embodiment of the present invention will be described with reference to FIG.

As shown in Fig. 5, in the first embodiment, the protrusion 205a is formed at the lower edge of the light guide plate 204, and its cross section is formed in a square. In this case, the quadrangle may be a rectangular quadrangle. Although the distance between the upper surface of the lamp housing 202 and the light guide plate 204 and the reflecting plate 203 and the light guide plate 204 is largely distinguishable with the naked eye, this describes a small space through which light can enter. In practice, smaller gaps are formed.

Meanwhile, FIG. 5 shows only the path of light reflected from the lamp 201 to the reflecting plate 203 and incident on the horizontal plane below the light guide plate 204, which causes the light path to cause a bright line in the conventional structure. Because it is the path of light.

The light reflected by the reflector 203 and incident on the horizontal plane below the light guide plate 204 is guided toward the liquid crystal panel through three paths.

First, there is a path of light (first path, 207a) that is reflected by the reflector and passes through the lower horizontal plane of the protrusion, and then passes through the air layer, to the vertical plane of the light guide plate. Second, it is reflected by the reflector and is incident on the lower horizontal plane of the protrusion. And a light path (second path, 208a), which is reflected back from the upper horizontal plane of the protrusion and then reflected from the lower horizontal plane of the protrusion, and thirdly, it is reflected by the reflector and is incident on the lower horizontal plane of the protrusion and again from the upper horizontal plane of the protrusion. There is a path of light (third path, 209a) that is reflected and then reflected through the protrusion to the reflector.

As described above, in the conventional light guide plate, the light guided toward the liquid crystal panel along a single path reaches the top of the different light guide plates 204 through the various paths 207a, 208a, and 209a in the first embodiment, and thus the light dispersion effect. Occurs.

Therefore, it is possible to prevent the generation of bright lines in the image display unit, which has occurred in the conventional structure, by the light dispersion effect.

In addition, the protrusion 205a preferably has a size of several tens of microns (10 to 100 microns), which means that when the size of the protrusion 205a is larger than that, the light path is sprayed as shown in FIG. 5. This is because it can be led toward the liquid crystal panel along the same path. As described above, in FIG. 5, the gap between the upper surface of the lamp housing 202 and the light guide plate 204 and the reflective plate 203 and the light guide plate 204 is widely indicated. The reason becomes clearer.

On the other hand, the size of the protrusion 205a more precisely corresponds to the diameter of the rectangular circumscribed circle constituting the cross section.

Referring to Fig. 6, the second embodiment will be described in detail.

As shown in FIG. 6, in the second embodiment, a protrusion 206a having a curved cross section is formed at a lower edge of the light guide plate 204.

At this time, the path of the light emitted from the lamp is reflected on the reflecting plate 203, which corresponds to the path that caused the generation of bright lines in the conventional structure, and looks at the path incident to the curved portion of the protrusion 206.

The path of the light reflected by the reflecting plate and incident on the curved portion of the protrusion is the first path 207b along a similar path as in the first embodiment, It is distributed into the second path 208b and the third path 209b. However, the second embodiment is different from the first embodiment in that the angle of incidence of the light reflected by the reflector 203 to the curved portion of the protrusion 206a is slightly changed along the curve. This will change the position where the light reaches the liquid crystal panel at the end of the refraction and reflection stages in the future even though there are minute changes.

Therefore, in the second embodiment, the degree of dispersion of the light path is greater than in the first embodiment, and the effect of preventing the generation of bright lines is also increased.

On the other hand, in the second embodiment, the size of the protrusion 206a formed in the light guide plate is preferably required to be several tens of microns. The reason is the same as that described in the first embodiment, and description is omitted.

Referring to Fig. 7, the third embodiment will be described in detail.

As shown in FIG. 7, in the third embodiment, rectangular protrusions 205a and 205b are formed at both lower and upper edges of the light guide plate 204. The rectangular protrusions 205a and 205b may have rectangular cross sections.

In the drawings, only the path of light incident on the upper edge portion of the light guide plate 204 is shown for convenience of description, and the light incident on the lower edge portion of the light guide plate 204 is dispersed in the same manner as in the first embodiment described above. .

The path of light reflected on the upper part of the lamp housing 202 and incident on the upper protrusion of the light guide plate 204 corresponds to a path that causes the bright line as described in the conventional structure.

However, in the third embodiment, the path of light first enters the upper protrusion of the light guide plate, passes through the air layer, and then enters the vertical plane of the light guide plate (first path 210a), and secondly, the light guide plate. A path (second path, 211a) that is incident on the upper projection and is reflected from the lower surface of the light guide plate, and then is reflected from the upper surface of the light guide plate, and thirdly, is incident on the upper protrusion of the light guide plate and reflected from the lower surface of the protrusion. After that, it is dispersed in three kinds of paths (third path, 212a) reflected by the reflector again.

Accordingly, it can be seen that the light guide plate structure of the third embodiment as described above can more effectively prevent the occurrence of bright lines generated in the conventional structure.

In addition, the size of the protrusions 205a and 205b formed on the light guide plate is most preferably the case of several tens of microns as in the first and second embodiments.

A fourth embodiment will be described in detail with reference to FIG.

As shown in FIG. 8, in the fourth embodiment, protrusions 206a and 206b having curved cross sections are formed at both the lower and upper edges of the light guide plate 204.

Also in FIG. 8, as in FIG. 7 illustrating the third embodiment, only the path of light incident to the upper edge portion of the light guide plate is shown for convenience of description, and the light incident to the lower edge portion of the light guide plate is the second light described above. It is dispersed in the same manner as in the embodiment.

Similarly to the third embodiment in the fourth embodiment, the paths of light reflected from the lamp housing are distributed into three types of the first path 210b, the second path 211b, and the third path 212b.

Since the cross sections of the protrusions 206a and 206b formed at the lower and upper edges of the light guide plate are curved in cross section, the path of light reflected by the reflector is changed along the curve of the protrusions formed in the light guide plate. The change is made through various refraction and reflection steps in the future, and the position where light finally reaches the liquid crystal panel is changed.

Therefore, in the fourth exemplary embodiment, the protrusions 206a and 206b are formed at both the lower side and the upper side of the light guide plate, and the cross section of the protrusions is curved, and thus, it is most effective for preventing the occurrence of the bright line of the screen display unit.

Also in the fourth embodiment, the size of the protrusions 206a and 206b formed in the light guide plate is most preferably tens of microns for the same reason as in the first, second and third embodiments.

The backlight device of the present invention as described above is combined with the liquid crystal panel and the driver to form a liquid crystal display device.

Therefore, the liquid crystal display device including the backlight device of the present invention has an advantageous effect that the generation of bright lines in the image display unit is prevented.

Many details are set forth in the foregoing description but should be construed as illustrative of preferred embodiments rather than to limit the scope of the invention. Therefore, the invention should not be defined by the described embodiments, but should be defined by the claims and their equivalents.

As described above, in the backlight device according to the present invention, protrusions are formed at edge portions of the light guide plate. The protruding portion serves to prevent a bright line from being generated in the image display portion of the liquid crystal display by dispersing the path when the light generated from the lamp is incident on the edge portion of the light guide plate.

Since the liquid crystal display device including the backlight device of the present invention is prevented from generating bright lines, the image quality is improved and the production yield is improved.

Claims (18)

Lamps for generating light; A light guide plate inducing light generated by the lamp and having a protrusion formed at an edge portion at which the light is incident; A lamp housing surrounding and protecting the lamp and reflecting light generated from the lamp; A reflection plate reflecting light generated by the lamp and formed under the light guide plate; And And an optical sheet for uniformly transferring the light guided by the light guide plate toward the light guide plate. The method of claim 1, Protrusions formed in the corner portion of the light guide plate through which the light is incident, A backlight device, characterized in that formed in the lower corner. The method of claim 1, Protrusions formed in the corner portion of the light guide plate through which the light is incident, Back light device, characterized in that formed in the lower and upper corners. The method of claim 2, Protrusions formed at the lower edge of the light guide plate, A backlight device, characterized in that the cross section is rectangular. The method of claim 2, Protrusions formed at the lower edge of the light guide plate, A backlight device whose cross section is a rectangular quadrangle. The method of claim 2, Protrusions formed at the lower edge of the light guide plate, A backlight device, characterized in that the cross section is curved. The method of claim 3, wherein Protrusions formed in the lower and upper corners of the light guide plate, A backlight device, characterized in that the cross section is rectangular. The method of claim 3, wherein Protrusions formed in the lower and upper corners of the light guide plate, A backlight device whose cross section is a rectangular quadrangle. The method of claim 3, wherein Protrusions formed in the lower and upper corners of the light guide plate, A backlight device, characterized in that the cross section is curved. The method according to any one of claims 1 to 9, Protrusions formed in the corner portion of the light guide plate through which the light is incident, A backlight device, the size of which is 10 to 100 microns. Lamps for generating light; A light guide plate which induces light generated by the lamp and has a protrusion formed at a lower edge portion at which the light is incident; A lamp housing surrounding and protecting the lamp and reflecting light generated from the lamp; A reflection plate reflecting light generated by the lamp and formed under the light guide plate; And And a backlight device composed of an optical sheet for uniformly transferring the light guided by the light guide plate toward the light guide plate. Lamps for generating light; A light guide plate which induces light generated by the lamp and has protrusions formed at lower and upper edges of the light incident thereto; A lamp housing surrounding and protecting the lamp and reflecting light generated from the lamp; A reflection plate reflecting light generated by the lamp and formed under the light guide plate; And And a backlight device composed of an optical sheet for uniformly transferring the light guided by the light guide plate toward the light guide plate. The method of claim 11, Protrusions formed at the lower edge of the light guide plate, A liquid crystal display device, characterized in that the cross section is rectangular. The method of claim 11, Protrusions formed at the lower edge of the light guide plate, A liquid crystal display device, characterized in that the cross section is curved. The method of claim 12, Protrusions formed in the lower and upper corners of the light guide plate, A liquid crystal display device, characterized in that the cross section is rectangular. The method of claim 12, Protrusions formed in the lower and upper corners of the light guide plate, A liquid crystal display device, characterized in that the cross section is curved. The method according to any one of claims 11, 13 or 14, Protrusions formed at the lower edge portion of the light guide plate through which the light is incident, A backlight device, the size of which is 10 to 100 microns. The method according to any one of claims 12, 15 or 16, Protrusions formed on the lower and upper corners of the light guide plate through which the light is incident, A backlight device, the size of which is 10 to 100 microns.

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