KR20100068102A - Liquid crystal display device - Google Patents

Abstract

PURPOSE: A liquid crystal display device is provided to supply light of relatively uniform brightness distribution, thereby improving screen display quality. CONSTITUTION: On the rear side of an optical path change sheet(103), plural light path change patterns(103b) are protruded toward a point light source(102). On the upper part of the optical path change sheet, a diffusing plate(104) is arranged with a fixed gap with the optical path change sheet. The diffusing plate diffuses light from the optical path change sheet. An optical sheet(105) arranged on the diffusing plate diffuses/concentrates light from the diffusing plate.

Description

[0001] LIQUID CRYSTAL DISPLAY DEVICE [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device having improved display quality due to improved brightness uniformity of light supplied to the liquid crystal panel.

BACKGROUND ART In general, liquid crystal display devices have tended to be gradually widened due to their light weight, thinness, and low power consumption. Accordingly, the liquid crystal display device is widely used as a portable computer such as a notebook PC, office automation equipment, audio / video equipment, and the like.

In general, a liquid crystal display device displays a desired image on a screen by adjusting the amount of light transmitted according to image signals applied to a plurality of control switching elements arranged in a matrix.

The liquid crystal display includes a liquid crystal panel in which a color filter substrate, which is an upper substrate, and a thin film transistor array substrate, which is a lower substrate, face each other and a liquid crystal layer is filled between the two substrates. And a driving unit for supplying a scan signal and image information to the liquid crystal panel to operate the liquid crystal panel.

Since the liquid crystal display is a non-light emitting device that does not emit light by itself, in order to implement an image, a light source for supplying light to the liquid crystal panel is required. Accordingly, the liquid crystal display includes a back light assembly including a light source for supplying light to the liquid crystal panel.

Conventionally, a cold cathode fluorescent lamp (CCFL) has been mainly used as a light source of a backlight assembly. However, in recent years, according to the trend toward miniaturization, thinness, and light weight of liquid crystal displays, light emitting diodes (LEDs), which are advantageous in power consumption, weight, and brightness, are advantageous. Increasingly, liquid crystal displays adopting a light emitting diode as a light source of a backlight assembly are increasing.

Hereinafter, a conventional liquid crystal display device will be described with reference to the accompanying drawings.

As shown in FIG. 1, a conventional liquid crystal display device includes a liquid crystal panel 1, a plurality of light emitting diodes 2 disposed under the liquid crystal panel 1, and supplying light to the liquid crystal panel 1. A diffusion plate 4 for diffusing light emitted from the light emitting diodes 2, an optical sheet 5 for diffusing and condensing the light emitted from the diffusion plate 4, and supplying the light to the liquid crystal panel 1; And a reflecting sheet 6 for reflecting the light emitted from the light emitting diode 2 to the lower portion of the light emitting diode 2 into the diffuser plate 4.

In the conventional general liquid crystal display device having the above configuration, the light emitted from the plurality of light emitting diodes 2 and passing through the diffusion plate 4 is placed on the top of the light emitting diodes 2 as shown in the simulation result of FIG. 5. The luminance of the corresponding region is relatively high, and thus the light having a large luminance deviation according to the position does not have a uniform distribution even though it passes through the optical sheet 5. Here, FIG. 2 is a simulation result of the luminance of the light of the diffusion plate 4 after the diffusion plate 4 is disposed on the light emitting diode 2 and the light emitting diode 2 is driven.

Therefore, in order to solve this problem, a lens is formed on the light emitting diode 2 to change the traveling direction of the light in the lateral direction, or use a large number of light emitting diodes 2, or diffuse with the light emitting diodes 2. Measures such as increasing the distance of the plate 4 have been devised.

However, when a lens is formed on the light emitting diode 2 to change the light traveling direction in the lateral direction, the amount of light traveling in the vertical or near vertical direction with respect to the back surface of the diffuser plate 4 decreases. There is a problem that dark spots in the form of dots occur in a region corresponding to 2). In the case where a large number of light emitting diodes 2 are used, the characteristics of the light emitting diodes 2 are affected by the heat generated from the light emitting diodes 2. If the diffusion plate 4 or the optical sheet 5 is deformed, or the distance between the light emitting diode 2 and the diffusion plate 4 is increased, the size of the entire liquid crystal display device is increased and thus the size of the liquid crystal display device is increased. There is a problem that does not meet the user's demand for a thinned model.

Accordingly, the present invention is to solve the above problems, an object of the present invention is provided with a light path changing sheet provided with a light path changing pattern for changing the path of the light emitted from the light emitting diode, the luminance uniformity of the light supplied to the liquid crystal panel It is to provide an improved liquid crystal display device.

Liquid crystal display device according to an embodiment of the present invention for achieving the above object, the liquid crystal panel; A plurality of point light sources disposed under the liquid crystal panel and supplying light to the liquid crystal panel; An optical path changing sheet disposed on an upper portion of the plurality of point light sources, and having a plurality of light path changing patterns protruding toward the point light source at a rear thereof to change a path of light emitted from the point light source; A diffuser plate disposed above the light path changing sheet at a predetermined distance from the light path changing sheet to diffuse light from the light path changing sheet; And an optical sheet disposed on the diffuser plate to diffuse and condense the light from the diffuser plate and supply the light to the liquid crystal panel. And a control unit. Each of the light path changing patterns of the plurality of light path changing sheets is formed so as to have a square light exit surface for emitting light into the light path changing sheet, and to have an acute angle with respect to the light exit surface. It is characterized in that it comprises a four light incident surface incident light.

In the liquid crystal display device according to the preferred embodiment of the present invention having such a configuration, the optical path changing sheet provided with the optical path changing pattern is provided so that the light emitted from the point light source is refracted to have a relatively uniform luminance distribution. Since the plate and the optical sheet pass through, the liquid crystal panel is supplied with light having a relatively uniform luminance distribution, thereby improving display quality.

Hereinafter, a liquid crystal display according to an exemplary embodiment of the present invention will be described in detail with reference to the accompanying drawings.

As shown in FIG. 3, a liquid crystal display according to a preferred embodiment of the present invention includes a liquid crystal panel 101; A plurality of point light sources 102 disposed under the liquid crystal panel 101 and supplying light to the liquid crystal panel 101; A plurality of light path change patterns 103b disposed on an upper portion of the plurality of point light sources 102 and protruding toward the point light sources 102 may be formed on the rear thereof to change a path of light emitted from the point light sources 102. Change sheet 103; A diffusion plate 104 disposed above the light path changing sheet 103 at a predetermined interval from the light path changing sheet 103 to diffuse light from the light path changing sheet 103; And an optical sheet 104 disposed on the diffuser plate 104 to diffuse and condense the light from the diffuser plate 104 and supply the light to the liquid crystal panel 101. It is configured to include. Each of the light path change patterns 103b of the plurality of light path change sheets 103 includes a square light exit surface 103b2 for emitting light into the light path change sheet 103 and the light exit surface. It is formed so as to have an acute angle with respect to 103b2, and is comprised including four light incidence surfaces 103b1 in which the light from the point light source 102 is incident.

Each component of the preferred liquid crystal display of the present invention having such a configuration will be described in detail as follows.

Referring to FIG. 3, the liquid crystal panel 101 includes a color filter substrate 101a, which is an upper substrate, and a thin film transistor array substrate 101b, which is a lower substrate, and includes a liquid crystal layer between the two substrates 101a and 101b. Not shown) is formed.

A plurality of point light sources 102 are disposed below the liquid crystal panel 101. The point light sources 102 adjacent to each other among the plurality of point light sources 102 have a spacing of 10 [mm] or more and 60 [mm] or less. Placed with D1).

The point light source 102 is an example of a light emitting diode (LED) in describing a liquid crystal display device according to a preferred embodiment of the present invention. Thus, the point light source 102 mentioned in the following description refers to a light emitting diode. However, the point light source 102 of the liquid crystal display device according to the present invention is not limited to the light emitting diode, and other type of point light source 102 other than the light emitting diode may be sufficiently employed.

3 and 4, an optical path changing sheet 103 is disposed on the point light source 102. The optical path changing sheet 103 includes a base sheet 103a and the base sheet 103a. And a plurality of light path changing patterns 103b which are formed on the rear surface of the light source and change the path of the light emitted from the point light source 103. Such a light path changing sheet 103 is formed to be hard without flexibility by using injection or compression, or is formed thin so as to have flexibility.

The base sheet 103a of the light path changing sheet 103 may be formed of any one selected from polycarbonate, polymethylmethacrylate, MS resin, polystyrene, and polyethylene. Is formed.

The base sheet 103a of the light path changing sheet 103 is composed of one or more layers. When the base sheet 103a is formed of one layer, beads are formed inside the base sheet 103a. If the base sheet 103a is composed of two or more layers, the beads may be formed in at least one of the two or more layers constituting the base sheet 103a.

As described above, the beads included in the base sheet 103a of the light path changing sheet 103 are at least one selected from polystyrene, polymethylmethacrylate, silica, and titanium oxide (TiO ₂ ). It is formed using one material.

Referring to FIG. 4, the light path changing pattern 103b of the light path changing sheet 103 is formed of the same material as that of the base sheet 103a and formed integrally with the base sheet 103a or the base. It may be formed of a material different from that of the sheet 103a.

At this time, when the light path changing pattern 103b is formed of a material different from that of the base sheet 103a, the light path changing pattern 103b is formed on the base sheet 103a by an ultraviolet (UV) curing agent and an acrylic type. It is formed by laminating any one selected from a monomer, an acrylic polymer, and a binder, and performing UV curing.

4 and 5, each of the light path change patterns 103b of the light path change sheet 103 has a square light exit surface 103b2 that emits light into the light path change sheet 103. And four light entering surfaces 103b1 formed to have an acute angle with respect to the light exiting surface 103b2 and to which light from the point light source 102 is incident.

The lowermost regions of the light path changing pattern 103b are located on a imaginary plane parallel to the base film 103a, and the uppermost region of the point light source 102 is also located on a imaginary plane parallel to the base film 103a. However, the virtual plane in which the lowermost region of the light path change pattern 103b is located and the virtual plane in which the uppermost region of the point light source 102 is located are separated from each other by 2 [mm] or more and 15 [mm] or less. D2).

FIG. 5 is a plan view of the light path changing pattern 103b viewed from below and a cross-sectional view of the light path changing pattern 103b vertically cut. Referring to FIG. 5, the light path changing pattern 103b is illustrated. The four sides of the light emitting surface 103b2 are each formed to have a length L1 of 100 [μm] or more and 150 [μm] or less, and the upper and lower width L2 is 0.2 or more and 0.8 times the sides of the light emitting surface mentioned above. It is formed so that it may become the following.

The light path changing pattern 103b is formed such that an angle θ formed between the light exiting surface 103b2 and the light entering surface 103b1 is 35 ° or more and 55 ° or less.

Referring to FIG. 5, the lowermost region (region A) of the light path change pattern 103b forms a curved surface which is part of a sphere, and the curvature of the curved surface is 2 [μm] or more and 200 [μm] or less, and more specifically, the curved surface. It is preferable that the curvature of is 2 [micrometer] or more and 20 [micrometer] or less. Here, the curvature is the radius of the imaginary sphere extending the curved surface formed by the lowermost region (region A) of the light path changing pattern 103b.

3 to 5 illustrate that the lowermost region (area A) of the light path changing pattern 103b has a curved shape, but the curved shape changes the light path in the process of manufacturing the light path changing pattern 103b. When curing the pattern forming material is caused by shrinkage of the material for forming the optical path pattern, the present invention is not limited thereto, and the lower region of the optical path changing pattern 103b forms a sharp shape. Various examples are possible without departing from the gist of the present invention. As such, when the lower region of the light path changing pattern 103b has a sharp shape, the light incident surface of the light path changing pattern will have a triangular shape.

Referring to FIGS. 3 and 4, a diffusion plate 104 is disposed on the light path changing sheet 103 provided with the light path pattern 103b as described above to diffuse light from the light path changing sheet 103. do.

Referring to FIG. 4, the diffusion plate 104 as described above is preferably disposed with a distance D3 of 5 [mm] or more and 20 [mm] or less.

In addition, an optical sheet 105 including a plurality of sheets supplied to the liquid crystal panel 101 after diffusing and condensing light from the diffusion plate 104 is disposed on the diffusion plate 104.

The optical sheet 105 may include a first and a second diffusion sheet, a prism sheet, and a third diffusion sheet. The combination example of the plurality of sheets constituting the optical sheet 105 is an example for explaining the present invention, but the present invention is not limited thereto, and the optical sheet 105 has a smaller or larger number of diffusion sheets. Various modifications may be made without departing from the spirit of the present invention, such as including or including two or more prism sheets.

Although not shown in detail in the drawing, a reflective sheet (not shown) reflecting the light emitted from the point light source 102 and proceeding to the bottom of the point light source 102 to the light path changing sheet 103 at the bottom of the point light source 102. H) is arranged.

In the liquid crystal display device according to the preferred embodiment of the present invention having the configuration as described above, the optical path changing pattern 103b of the optical path changing sheet 103 refracts the light emitted from the point light source 102 to be relatively Since a uniform luminance distribution is provided, light of a relatively uniform luminance distribution is supplied to the liquid crystal panel 101, thereby improving display quality.

FIG. 6 is a view illustrating a liquid crystal display device according to an exemplary embodiment of the present invention. After the light path changing sheet 103 and the diffusion plate 104 are disposed on a plurality of point light sources 102, the point light sources 102 are driven. In the liquid crystal display according to the preferred embodiment of the present invention, light emitted from a plurality of point light sources 102 is a light path. It can be seen that the light path changing pattern 103b of the change sheet 103 and the diffusion plate 104 are changed to have a relatively uniform luminance distribution, and thus the liquid crystal panel 101 has a uniform luminance distribution. It can be seen that light is supplied to improve the screen display quality.

7 is a graph showing light distribution according to the shape of the optical path changing pattern 103b formed on the optical path changing sheet 103 in the liquid crystal display according to the preferred embodiment of the present invention. That is, FIG. 7 is a graph showing light distribution when the point light source is driven after arranging the light path changing sheet 103 and the diffusion plate 104 on the plurality of point light sources 102. For convenience of description, FIG. Microlens shape, cone shape, prism as well as light distribution data for the light path change pattern 103b according to the present invention having a pyramid-like shape as shown in FIGS. The light distribution data for the light path change pattern of the shape, the lenticular shape and the light distribution data for the case in which the light path change pattern is not provided are shown. Referring to FIG. 7, the pattern of the pyramid-like shape is shown. The light distribution for the light path changing pattern 103b according to the invention can be relatively uniform compared to other cases.

Therefore, the liquid crystal display according to the exemplary embodiment of the present invention can provide a screen with improved display quality to the user since uniform surface light is supplied to the liquid crystal panel 101.

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

FIG. 2 is a simulation result of the brightness of light of a diffuser plate after dispersing the diffuser plate and driving the light emitting diode in the liquid crystal display of FIG. 1. FIG.

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

4 is a cross-sectional view illustrating a cross section taken along line II ′ of the liquid crystal display of FIG. 3.

5 is a plan view and a cross-sectional view of the light path changing pattern of the light path changing sheet of FIG.

6 is a simulation result of the brightness of light of a diffuser plate after arranging a light path changing sheet and a diffuser plate on the point light source and driving a light emitting diode in the liquid crystal display of FIG.

7 is a graph showing light distribution according to the shape of the optical path changing pattern formed on the optical path changing sheet.

** Description of the symbols for the main parts of the drawings **

101: liquid crystal panel 102: point light source

103: light path changing sheet 103a: base sheet

103b: light path changing pattern 103b1: light incident surface

103b2: Output surface 104: Diffusion plate

105: optical sheet

Claims (15)

A liquid crystal panel; A plurality of point light sources disposed under the liquid crystal panel and supplying light to the liquid crystal panel; An optical path changing sheet disposed on an upper portion of the plurality of point light sources, and having a plurality of light path changing patterns protruding toward the point light source at a rear thereof to change a path of light emitted from the point light source; A diffuser plate disposed above the light path changing sheet at a predetermined distance from the light path changing sheet to diffuse light from the light path changing sheet; And An optical sheet disposed on the diffuser plate to diffuse and collect light from the diffuser plate and supply the light to the liquid crystal panel; It is configured to include, Each of the plurality of light path changing patterns of the plurality of light path changing sheets has a square light exit surface for emitting light into the light path changing sheet, and is formed to have an acute angle with respect to the light exit surface so that light from a point light source may be formed. A liquid crystal display comprising four incident light incident surfaces. The method of claim 1, wherein the light path changing sheet comprises a base sheet and a light path changing pattern formed on the rear surface of the base sheet, And the base sheet is formed of any one selected from polycarbonate, polymethylmethacrylate, MS resin, polystyrene, and polyethylene. The liquid crystal display of claim 2, wherein the light path changing pattern is integrally formed of the same material as that of the base sheet. The method of claim 2, wherein the light path change pattern is formed of a material different from the base sheet, The light path changing pattern is formed by stacking any one selected from an ultraviolet (UV) curing agent, an acryl-based monomer, a polymer, and a binder on a base sheet and curing an ultraviolet (UV). Liquid crystal display characterized in that formed. The method of claim 1, wherein the light path change sheet is composed of one or more layers, And at least one of the layers constituting the light path changing sheet is formed to include beads therein. The liquid crystal of claim 5, wherein the beads are formed of at least one selected from polystyrene, polymethylmethacrylate, silica, and titanium oxide (TiO ₂ ). Display. The liquid crystal display device according to claim 1, wherein point light sources adjacent to each other among the plurality of point light sources are arranged at intervals of 10 [mm] or more and 60 [mm] or less. The virtual plane in which the uppermost region of the point light source is located and the virtual plane in which the lowermost region of the light path change pattern are located have a spacing of 2 [mm] or more and 15 [mm] or less. A liquid crystal display device. The liquid crystal display device according to claim 1, wherein each of the four sides of the light exit surface of the light path change pattern has a length of 100 [µm] or more and 500 [µm] or less. 10. The liquid crystal display device according to claim 9, wherein the upper and lower widths of the light path changing pattern are 0.2 times or more and 0.8 times or less of the sides of the light exit surface. The liquid crystal display device according to claim 1, wherein an angle formed between the light exiting surface and the light receiving surface is 35 degrees or more and 55 degrees or less. The liquid crystal display of claim 1, wherein the lower region of the light path changing pattern has a pointed shape. The liquid crystal display device according to claim 1, wherein the lower region of the light path changing pattern is a curved surface which is a part of a sphere, and the curved surface has a curvature of 2 [µm] or more and 200 [µm] or less. The liquid crystal display device according to claim 1, wherein the lower region of the light path changing pattern is a curved surface which is a part of a sphere, and the curved surface has a curvature of 2 [µm] or more and 20 [µm] or less. The liquid crystal display device according to claim 1, wherein the light path changing sheet and the diffusion plate are arranged at a distance of 5 [mm] or more and 20 [mm] or less.

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