Liquid crystal display including at least two light guiding plates abutting each other

A liquid crystal display of a large screen size, a slim thickness and light weight is disclosed. The liquid crystal display includes a light supply unit group having at least two light guiding plates arranged in parallel and at least one lamp unit coupled to one side of the light guiding plate. A light control element is mounted on an upper surface of the light supply unit group, and uniformly controls luminance between the light guiding plate and the lamp unit. A reflective plate is disposed on a rear surface of the light supply unit group and has a shape corresponding to the rear surface of the light supply unit group. A back light assembly includes a receiving container that receives the light supply unit group, the light control element, and the reflective plate.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a liquid crystal display (LCD), and more particularly to a liquid crystal display in which at least two or more light guiding plates are arranged in parallel, a lamp unit is disposed at one side of the light guiding plate or between the light guiding plates, thereby enhancing luminance of a large screen sized LCD, and enabling the LCD to have a uniform luminance and a compact size of a lighter weight.

2. Description of the Related Art

Generally, an LCD is a mostly used type of flat panel display. Especially, the small size, lighter weight and lower power consumption render the LCD to replace the traditional cathode ray tube (CRT).

To display an image on the LCD panel, the LCD needs a light source called as back light assembly.

The back light assembly comprises a lamp unit for generating light beams, a diffusion sheet disposed below the LCD panel, for diffusing light beams generated from the lamp unit, a light guiding plate having a wedge shape or a flat shape, for guiding the light beams generated from the lamp unit into whole surface of the light guiding plate, a reflecting plate disposed below the light guiding plate, for directing the leaked light from the light guiding plate toward the LCD panel and a receiving container called as mold frame and that receives the lamp unit, the diffusion sheet, the light guiding plate and the reflecting plate.

Recently, an LCD panel of 14 inch or larger diagonal size is being developed for a desk top computer as well as a notebook computer. Moreover, its application gains the popularity as the display in almost all of industries.

Then, although the development in the LCD technology is directed toward large-sized screen, the thickness of the LCD panel is not increased to a large degree. However, size and thickness of the back light assembly increase to a large degree as the screen size increases, and also increase the size of the light guiding plate.

In order to prevent the luminescence inconsistency, which may be inevitable as the LCD becomes large, the incident face of the light guiding plate becomes thicker. This increases the total area and weight of the light guiding plate, increasing the entire size and thickness of the LCD. This goes against the current trend of a slimmer and lighter LCD.

SUMMARY OF THE INVENTION

The present invention enables an LCD to have a large screen, a slimmer thickness and a lighter weight.

To achieve these and other advantages in accordance with the purpose of the present invention as embodied and broadly described, a liquid crystal display comprises: a light supply unit group having at least two light guiding plates arranged in parallel and at least one lamp unit coupled to one side of said light guiding plate; a light control element mounted on an upper surface of said light supply unit group, for uniformly controlling luminance between said light guiding plate and said lamp unit; a reflective plate disposed on a rear surface of said light supply unit group and having a corresponding shape to that of said rear surface of said light supply unit group; a back light assembly including a receiving container that receives said light supply unit group, said light control element, and said reflective plate; and a display unit mounted on said light control element and fixed by said receiving container.

In addition, a plurality of different shape and combinations of light guiding plate are disclosed. It can achieve a slimmer and lighter LCD with a large screen size.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, a liquid crystal display according to the present invention is described more fully with reference to the accompanying drawings.

FIG. 1is an exploded perspective view of the liquid crystal display according to a preferred embodiment of the present invention.

Referring toFIG. 1, the liquid crystal display801comprises a display unit100, a back light assembly600and a chassis700, on the whole.

The display unit100comprises a liquid crystal display (LCD) panel10, a tape carrier package20and a printed circuit board (PCB)30having a driving signal generating part (not shown).

The LCD panel10includes a TFT substrate2, a color filter substrate4and a liquid crystal layer interposed between the TFT substrate2and the color filter substrate4.

The TFT substrate2includes a transparent glass substrate. On the transparent glass substrate, a plurality of thin film transistors (not shown) each including a gate, a source, and a drain are formed in a matrix arrangement by the semiconductor thin film formation process.

Source terminals of all the thin film transistors in one column are connected to a data line (not shown). Gate terminals of all the thin film transistors in a row are connected to a gate line. The drain terminal of each thin film transistor is connected to an ITO electrode, which is a pixel electrode.

The color filter substrate4includes a transparent glass substrate. The transparent glass substrate4has a lattice type black matrix (not shown), an RGB pixel (not shown) and a transparent and conductive ITO (Indium Tin Oxide) electrode. Here, the RGB pixels are formed by patterning a photoresist mixed with RBG pigment. The ITO electrode functions as a common electrode.

The liquid crystal layer interposed between the TFT substrate2and the color filter substrate4includes a plurality of liquid crystal molecules. The liquid crystal molecules are arranged at a pretilt angle when an electric field is not applied between the pixel electrode and the common electrode. As the thin film transistors are turned on and an electric field is applied between the pixel electrode and the common electrode, the liquid crystal molecules are re-arranged depending on the intensity of the electric field, thereby passing incident light beams through the liquid crystal layer.

Thereafter, the light beams are collided with the RGB pixels of the color filter substrate4to display colors. The aforementioned procedure are very quickly and repeatedly conducted in a line unit or a dot unit, thereby displaying a desired image on the LCD panel.

Then, the liquid crystal layer itself is not the light emitting element but the light receiving element. So, in order to display an image with a desired high and uniform luminance, the LCD needs the back light assembly600.

Referring toFIG. 1, the back light assembly600includes a light supply unit group200, a mold frame300as a receiving container, optical sheets400and a display unit fixing cover500.

Referring toFIG. 1toFIG. 3, the light supply unit group200includes a plurality of light supply units150, each having a light guiding plate110and a lamp unit130.

The light guiding plate110is a rectangular shape when it is viewed from the top and is a wedge type in which its thickness decreases as it travels from one edge to the other edge facing the one edge. Here, a side wall112corresponding to the one edge where the light guiding plate is relatively thick serves as an incident face. An upper edge of the side wall perpendicular to the side wall serving as light incident face has a stepped portion114. The light guiding plate110also has side walls116and118facing each other. Each of the side walls116and118has a swaying preventive projection119projected from the surface thereof by a selected height. It is preferable that the projection119is made to have a rectangular parallelepiped shape. The projection119is coupled to the receiving container300to prevent the light guiding plate110from being unnecessary sway.

Beneath the light guiding plate110, a reflective layer (or a reflective dot) is formed by a silk screen method in order to further increase the luminance.

The lamp unit130includes a lamp cover132having a semi-cylindrical shape and a lamp134installed within the lamp cover132. The lamp cover134is fixed to the side wall112serving as the light incident face using various gluing ways.

Although the aforementioned embodiment shows and describes a light supply unit having only a single lamp, the light supply unit150can have at least two lamps.

FIG. 1shows the light supply unit group200in which four light supply units are coupled to each other. As shown inFIG. 1, the other edge of each of the light supply units150of the light supply unit group200is mounted on the stepped portion114of the light incident face112of adjacent light supply unit and is coupled thereto.

Unlike the aforementioned fabrication method of the light supply unit group200, the light supply unit group200can be also fabricated by an injection molding. When the injection molding method is used for the formation of the light supply unit group200, it is not appropriate to form the reflective layer on the rear surface of the light guiding plate110using the silk screen method because the rear surface is not flat. So, when the injection molding method is applied, a bottom surface of the mold used in the injection molding is corroded to have a rough surface functioning as the reflective layer. Thereafter, the lamp unit130is coupled to the fabricated light supply unit group200.

For the assembly, a reflecting plate210is received in the receiving container300and the light supply units group200is then received on the reflecting plate within the receiving container300.

As shown in FIG.1andFIG. 2, the receiving container300is a rectangular parallelepiped shape in which an upper surface is open and has a space where the light supply units group200is received.

After the light supply units group200is assembled with the receiving container300, an upper surface of the light supply unit group200should be leveled. Therefore, a bottom surface220of the receiving container300has a saw tooth structure such that it is properly coupled with the rear surface of the light supply unit group200.

In the aforementioned embodiment, the light supply unit group200is made up of four light supply units150. Accordingly, the rear surface of the receiving container300comes to have four saw tooth.

Meanwhile, as shown in FIG.1andFIG. 2, the receiving container300has a projection fixing groove235at a place corresponding to the swaying preventive projection119of the light supply unit group200. The projection fixing groove235is coupled with the swaying preventive projection119when assembling the light supply unit group200with the receiving container300.

When such constructed LCD operates, the lamp unit134of the light supply unit group200emits a lot of heat. In order to prevent the heat-induced efficiency degradation of the lamp134, the receiving container300has at least one heat irradiation hole240as shown in FIG.2.

The receiving container300also includes a plurality of openings250at its bottom, each of the openings having a rectangular plate shape. The openings250lightens the receiving container300.

On the light supply unit group200coupled to the receiving container300, at least one, preferably three diffusion sheets400are mounted.

The diffusion sheets300should be fixed to the receiving container300such that although the receiving container300is swayed or the diffusion sheets400are expanded by heat in a state where the light supply units group200is coupled to the receiving container300, the diffusion sheets400can withstand the sway or heat expansion.

To this end, bosses260for fixing the diffusion sheets400are formed at four corners of the receiving container300. Here, it is desirous that the boss260has a height greater than total thickness of the three diffusion sheets400.

For example, when the diffusion sheets400are three, the diffusion sheets400are classified into a first diffusion sheet410shown inFIG. 4band a second diffusion sheet420shown inFIG. 4a.

The first diffusion sheet410is one sheet and contacts to the upper surface of the light supply units group200. The second diffusion sheet420is remaining two sheets from among the three diffusion sheets400and is mounted on the upper surface of the first diffusion sheet410.

Referring toFIG. 4b,the first diffusion sheet410comprises a reflective member414formed at the boundary between the light supply units150to prevent the non-uniform luminance at the boundary and induce scattered reflection. The reflective member414is formed by silk screen method.

The second diffusion sheet420shown inFIG. 4aagain diffuses the light beams reflected irregularly by the first diffusion sheet410to thereby increase the luminance uniformity.

The first and second diffusion sheets410and420each is comprised of projections418and428having a coupling hole418aand428aat four corners thereof. The coupling hole418aand428ais inserted into the bosses260formed at four corners of the receiving container300. Here, the coupling hole418aand428ahas a specific structure considering the expansion of the diffusion sheets400by heat.

Specifically, in a state that image is normally displayed, a reference coupling hole is disposed at the left upper corner of the diffusion sheet400and has a diameter to such a degree that it is inserted into the boss260of the receiving container300.

Also, in the state that image is normally displayed, a coupling hole disposed at the left lower corner has a shape of an ellipse in which a horizontal diameter is greater than a vertical diameter. The elliptical coupling hole allows the diffusion sheet400to be expanded only along the horizontal direction when the diffusion sheet400is expanded by the heat.

The remaining two coupling holes disposed at the right upper and lower portions of the diffusion sheets have some tolerance compared with the diameters of the corresponding bosses.

When the above constituted diffusion sheet400is coupled to the boss260of the receiving container300to which the light supply units group200has been coupled, the diffusion sheet400is hardly swayed along the left and right directions while it can be easily taken off from the boss260.

Thus, in order to prevent the diffusion sheet400and the light supply units group200from being taken off and to fix the display unit100, a display unit fixing cover500covers the receiving container300.

As shown inFIG. 5, the display unit fixing cover500is a rectangular frame and is coupled to the receiving container300. Here, the receiving container300has a stepped portion290at an outer upper portion of the side wall such that the unit fixing cover500is rigidly coupled to the receiving container300.

The display unit fixing cover500has a pushing piece520pushing the swaying preventive projection119at its inner lower portion such that the light guiding plate110of the light supply unit group200coupled to the receiving container300does not deviate from the outside.

The display unit fixing cover500has a guide530for guiding the display unit100at a proper position during the assembly of the display unit100. The guide530is partially formed along the upper edge including three corners of the display unit fixing cover500. Two edge portions of the display unit fixing cover500that do not have the guide530is provided for bending the PCB30. In other words, the two edge portions allow the PCB30to be easily bent toward the rear face of the display unit fixing cover500.

Here, it is desirous that the bent PCB30should be bent toward the thinner portion of the light guiding plate112ashown in FIG.3. This is to prevent that semiconductor chips of tape carrier packages20are degenerated by the heat of the lamp unit130when the PCB30is bent to place at the lamp unit portion of the light supply unit group200.

In a state where the display unit100is coupled to the display unit fixing cover500, in order to prevent the display unit100from deviating from the display unit fixing cover500, to enhance a coupling force between the display unit fixing cover500and the receiving container300, and to protect the display unit from an external impact, a chassis700is coupled and fixed to the display unit fixing cover500and the receiving container300as shown in FIG.6.

FIG. 7shows the light supply units group200according to another embodiment of the present invention. Here, other elements expect the light supply units group can be identically applied to the present LCD. Accordingly, their descriptions are intentionally omitted.

Referring toFIG. 7, two light supply units group160and170are shown. Each of the light supply unit groups has two light supply units coupled to each other in the same way as described inFIG. 1to FIG.5. The two light supply unit groups160and170are coupled to each other such that thinner portion of unit light supply unit of one light supply unit group faces with thinner portion of unit light supply unit of the other light supply unit group. At this time, the bottom portion of the receiving container300should have such a structure capable of receiving the above constructed light supply unit group200.

FIG. 8shows the light supply units group according to still another embodiment of the present invention.

Referring toFIG. 8, the light supply unit group940comprises at least two flat light guiding plates910arranged in parallel and a lamp unit920disposed at one edge of the light guiding plate910or between the light guiding plates910.

Like the previous embodiments, the bottom portion of the receiving container300should have such a structure capable of receiving the light supply unit group940.

FIG. 9shows the light supply unit group980according to further still another embodiment of the present invention.

Referring toFIG. 9, the light supply units group980comprises a flat-type light guiding plate950disposed at the center portion, wedge-type light guiding plates960disposed at both sides of the flat-type light guiding plate950and a lamp unit970disposed between the flat-type light guiding plate950and the wedge-type light guiding plates960.

Likewise the previous embodiments, the bottom portion of the receiving container300should have such a structure capable of receiving the light supply unit group980.

As described above, the present invention can provide a liquid crystal display having high and uniform luminance by forming a light supply unit group comprising a plurality of light guiding plates and a lamp unit disposed therebetween.

Moreover, using the wedge-type light guiding plate and connecting plural wedge-type light guiding plates, the light guiding plate becomes lighter, although the screen size becomes large.

Further, since the heat generated from the lamp unit is effectively radiated to the outside, the degeneration of the semiconductor chips mounted on the PCB and the tape carrier packages can be prevented.