KR20130117225A - Light diffusion plate having non-uniform local microlens array pattern and liquid crystal display device comprising the same - Google Patents

Abstract

PURPOSE: A light diffusion plate including a local micro lens array (MLA) pattern and a liquid crystal display (LCD) device including the same are provided to improve image quality by removing a moire phenomenon. CONSTITUTION: An uneven local LMA pattern is located around a center lens and is smaller than the center lens. The uneven local LMA pattern is comprised of a plurality of peripheral lenses. [Reference numerals] (AA,BB,CC,DD,EE,FF) Light source

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a light diffusion plate having a nonuniform local microlens array pattern, and a liquid crystal display device including the same. 2. Description of the Related Art Liquid diffusing plate having a non-

The present invention relates to a light diffusion plate having a nonuniform local microlens array pattern and a liquid crystal display including the same. More particularly, the present invention relates to a liquid crystal display device having a local microlens array pattern having a non- And a liquid crystal display device including the light diffusion plate and the liquid crystal display device.

Generally, the liquid crystal display device has a tendency of widening its application range due to features such as light weight, thinness, and low power consumption driving. Accordingly, liquid crystal display devices are widely used as portable computers such as notebook PCs, office automation devices, and audio / video devices.

In general, a liquid crystal display device displays a desired image on a screen by controlling a light transmission amount according to an image signal applied to a plurality of switching elements for control arranged in a matrix form.

In such a liquid crystal display, a color filter substrate, which is an upper substrate, and a thin film transistor array substrate, which is a lower substrate, are opposed to each other, and a liquid crystal panel And a driver for supplying scan signals 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.

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

1 is an exploded perspective view of a conventional general liquid crystal display device. Referring to FIG. 1, a display device 100 includes a display panel 120 for displaying an image in front.

The mold frame 130 supporting the display panel 120 is provided at an edge of the display panel 120. Optical sheets 141, 143 and 150 are provided under the mold frame 130, that is, behind the display panel 120. 143 and 150 on the rear or side surfaces of the optical sheets 141, 143 and 150, that is, on the optical sheets 141, 143 and 150, A light source 160 is provided.

The light source 160 and the optical sheets 141, 143, and 150 are connected to a backlight unit (not shown) through a backlight unit .

1 illustrates a direct type backlight unit in which the light source 160 is positioned behind the optical sheets 141, 143 and 150 and a light emitting diode (LED) is used as the light source 160. The LED light source may be mounted on a substrate such as a PCB.

A reflective sheet 170 for reflecting the light traveling in a direction other than the direction of the display panel 120 and changing the path of the light toward the display panel 120 is provided under the light source 160.

A lower portion of the reflective sheet 170 is coupled to the display panel 120, the optical sheets 141, 143 and 150, the light source 160 and the reflective sheet 170, A cover 180, and an upper cover 110 which is coupled to the lower cover 180. The upper cover 110 is a structure for supporting the front edge of the display panel 120. The upper cover 110 has a display window for exposing the display area of the display panel 120. And, the side of the upper cover 110 is provided with a coupling means such as a screw hole (not shown) for coupling with the lower cover 180 to be described later.

Although not shown, a printed circuit board connected to the thin film transistor of the display panel 120 may be provided on one side of the display panel 120. A signal from the printed circuit board is transmitted to the thin film transistor through the wiring, The thin film transistor drives the liquid crystal by applying a voltage to the pixel according to the signal.

The components of the display panel will be described in detail below.

The display panel is not particularly limited as long as it can display an image, and various display panels such as a liquid crystal display panel and an electrophoretic display panel can be used. Hereinafter, a liquid crystal display panel will be described as an example.

The display panel 120 is provided in a rectangular plate shape having a long side and a short side. The display panel 120 includes a first substrate 121, a second substrate 122 opposed to the first substrate 121, and a liquid crystal (not shown) formed between the two substrates. The display panel 120 drives the liquid crystal to display an image forward. In order to drive the liquid crystal, a thin film transistor may be formed on the first substrate 121 and a color filter may be formed on the second substrate 122. In this case, the TFT may be referred to as a thin film transistor substrate and a color filter substrate.

Polarizing plates 120a and 120b are provided on the back surfaces of the first substrate 121 and the second substrate 122, respectively, to control the light transmission according to the orientation of the liquid crystal.

Since the liquid crystal itself is non-luminescent, a light source 160 is required to realize an image. The transmitted light from the light source 160 also includes an undesired vibration vector. In order to adjust the vibration vector of the transmitted light, a polarizing plate (not shown) is attached to the both sides of the display panel 120 such that the transmission axis crosses 90 degrees. The polarizing plate is polarized by the light having the specific vibration vector. Accordingly, the intensity of the transmitted light can be adjusted according to the degree of rotation of the polarization axis while passing through the display panel 120, thereby enabling the display from black to white.

The mold frame 130 is provided along the edge of the display panel 120. The mold frame is formed in a substantially rectangular ring shape. The mold frame 130 supports the display panel 120 and the optical sheets 141, 143 and 150. The mold frame 130 is coupled to the lower cover 180 to receive the optical sheets 141, 143 and 150, the light source 160 and the reflection sheet 170 therein. The mold frame 130 may be formed in a single number as shown in the drawing, but may be formed as a plurality of molds as needed.

The optical sheets 141, 143, and 150 serve to control light emitted from the light source 160. The optical sheets 141, 143 and 150 include a diffusion plate 150 positioned on the rear surface of the display panel 120. In addition to the diffusion sheet, a protective sheet 141, a prism sheet 143, and a diffusion sheet (not shown) may further be included.

The optical sheets 141, 143, and 150 may be used in plural as needed, and two or three sheets may be stacked. In addition, the protective sheet 141 or the prism sheet 143 may be omitted as necessary.

The prism sheet 143 functions to condense the light diffused by the diffusion plate 150 in a direction perpendicular to the plane of the upper display panel 120. The light passing through the prism sheet 143 is substantially vertically propagated to provide a uniform luminance distribution.

The protective sheet 141 located at the uppermost position protects the prism sheet 143 which is weak against scratches.

A plurality of light sources 160 for supplying light to the display panel 120 through the optical sheets 141, 143 and 150 are provided below the optical sheets 141, 143 and 150. As the plurality of light sources, an LED that is a point light source may be used, but the present invention is not limited thereto.

A reflective sheet 170 is disposed under the light source 160. The reflective sheet 170 reflects light incident on a lower portion of the light emitted from the plurality of light sources 160 in a direction opposite to the upper direction.

As described above, when the display panel does not emit light itself like the liquid crystal display panel, the light source 160 that supplies light separately is used. As described above, the light source 160 may be a point light source such as an LED, a cold cathode fluorescent lamp (CCFL), an external electrode fluorescent lamp (EEFL), a hot cathode fluorescent lamp Fluorescence Lamp, HCFL) can be used to provide light.

Since the light source is usually a point light source or a source of linear light, when the light emitted from the light source is directly used in the display panel, the dark portion and the bright portion are divided according to the density of the emitted light, Accordingly, it is necessary to change the path of the light emitted from the light source and increase the light efficiency. Particularly, the light diffusing plate diffuses light having specific directionality emitted from a light source, particularly a point light source, into light emitted in various orientations.

In the display device, the LED can be mounted in a small space with a light source corresponding to a point light source, and is a highly efficient light source because of its high luminance. However, the display panel should be provided in the form of a planar light source, but uniformization of the light is necessary as long as the LED is a point light source. In addition, even in the case where the light source is the optical rotation source, it is necessary to equalize the light in the direction perpendicular to the light emission direction of the optical source. Here, the uniformity of light means that the image of the light source is not visible on the display panel.

However, the diffusion plate used in the prior art has a problem that the light emitted from the light source must be uniformly diffused in the liquid crystal direction, but the diffusion is not sufficiently performed due to the asymmetric structure.

In order to improve this, a technique of forming a uniform micro lens array pattern on the surface of the light diffusion plate has been disclosed in Korean Patent Laid-Open No. 10-2012-0003277. However, in the case of such a light diffusion plate, the light diffusion is still insufficient, In the reduced direct type backlight unit (BLU), there is a disadvantage that a lamp mura phenomenon in which the edge of the display is whitish around the lamp is seriously occurred.

Therefore, there is a desperate need to develop a light diffusion plate that provides sufficient light diffusion, but does not have a lamp shading phenomenon or is remarkably reduced.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems of the prior art and it is an object of the present invention to provide a light diffusion plate which has sufficient light diffusion to further improve brightness and uniformity of light supplied to a liquid crystal panel, And to provide a liquid crystal display device with improved screen display quality.

According to an aspect of the present invention, there is provided a light diffusing plate having a local microlens array pattern having a nonuniform surface.

According to another aspect of the present invention, there is provided a liquid crystal display panel comprising: a liquid crystal display panel; Light source; And a light diffusion plate of the present invention located between the liquid crystal display panel and the light source.

According to the present invention, it is possible to obtain a liquid crystal display device in which the brightness and uniformity of light supplied to the liquid crystal panel are further improved, and the lamp blurring phenomenon is eliminated or significantly reduced, thereby further improving the screen display quality.

1 is an exploded perspective view of a liquid crystal display device using a conventional light diffusing plate.
2 is a schematic view showing a nonuniform local microlens array (MLA) pattern on a surface (upper surface) of a light diffusing plate according to an embodiment of the present invention.
FIG. 3 is a schematic view of an embossing formed surface and a photomicrograph of an embossed structure, which is the opposite surface (lower surface) of a surface on which a nonuniform local microlens array pattern is formed, according to an embodiment of the present invention.
FIG. 4 is a view showing luminance distribution, MURA phenomenon, and actual images of an optical diffusing plate and a comparative optical diffusing plate according to an embodiment of the present invention.

Hereinafter, the present invention will be described in more detail.

The optical diffusing plate of the present invention is characterized by having a local microlens array pattern on its surface.

In the present invention, the term " nonuniform local microlens array pattern " means that the size of the plurality of microlenses constituting the microlens array pattern (diameter in the case of a circular shape) is not uniform.

According to one embodiment of the present invention, the non-uniform local microlens array pattern comprises a central lens (i.e., a lens positioned directly above the light source); And a plurality of peripheral lenses positioned around the center lens and having a size smaller than that of the center lens.

The diameter of the center lens is preferably 100 占 퐉 or more (for example, 100 to 500 占 퐉), more specifically 100 to 200 占 퐉, from the viewpoint of improvement of brightness and prevention of unevenness. Also preferably, the peripheral lens has a diameter of 90% or less (for example, 50 to 90%) of the diameter of the central lens, and more specifically, a diameter of 80 to 90% of the diameter of the center lens.

According to a more preferred embodiment of the present invention, a plurality of peripheral lenses are distributed stepwise in the direction away from the central lens around the central lens, and the diameter of the peripheral lenses in the stepwise step is 90% or less (for example, 50 to 90 %, More specifically 80 to 90%). At this time, the peripheral lens may preferably be distributed over 2 to 5 steps. For example, when the peripheral lenses are distributed in two stages, the central lens diameter may be 100 占 퐉, and the peripheral lens diameter in one step may be 90 占 퐉 or less - the second peripheral lens diameter may be 81 占 퐉 or less.

The light diffusing plate of the present invention may have an embossed structure on the opposite side of the surface on which the non-uniform local microlens array pattern is formed. Such an embossing structure is preferable because it can function to help light diffusion and prevent scratches.

In addition, the optical diffusion plate of the present invention may include a plurality of beads in the inside thereof so that light scattering and diffusion can smoothly occur. There are no particular restrictions on the size and material of the beads, and may include, but are not limited to, silicon, urethane or acrylic beads having a diameter of, for example, 1 to 30 탆. There is no particular limitation on the content of the beads, and may be, for example, in an amount of 1 to 5% by weight of the total weight of the light diffusion plate, but are not limited thereto.

The material of the optical diffusing plate of the present invention is not particularly limited, and can be manufactured by using known optical diffusing plate materials such as polycarbonate (PC), polystyrene (PS), etc. singly or in combination.

The method of producing the optical diffusing plate of the present invention is also not particularly limited, and the known optical diffusing plate making method can be used as it is or modified appropriately. According to one embodiment of the present invention, a non-uniform local microlens array pattern can be formed on one surface while extruding a material for an optical diffusing plate, and an embossed structure can be formed on the other surface at the same time.

According to another aspect of the present invention, there is provided a liquid crystal display panel comprising: a liquid crystal display panel; Light source; And a light diffusion plate of the present invention located between the liquid crystal display panel and the light source.

The liquid crystal display device of the present invention may have the same structure as a conventional general liquid crystal display device shown in FIG. 1, for example, and includes a diffusion plate 150 of the present invention as a diffusion plate.

Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples. However, the scope of the present invention is by no means limited by these examples.

Example

A central micro lens array pattern having a plurality of single-stage peripheral lenses (diameter: 90 mu m) and a plurality of two-stage peripheral lenses (diameter: 80 mu m) (PC) was prepared by extrusion molding.

As a comparative example, a light diffusing plate (PC) having a uniform local microlens array pattern with a diameter of 100 mu m on its upper surface and an embossed lower surface was manufactured by extrusion molding.

For each of the manufactured light diffusing plates, luminance and mura phenomenon were measured using an LED point light source, and the results are shown in Table 1 and FIG.

[Table 1]

As can be seen from the results of Table 1 and FIG. 4, in the case of the optical diffusing plate according to the embodiment of the present invention, the brightness was improved and the mura phenomenon was remarkably reduced as compared with the comparative example.

100: display device
110: top cover
120: display panel
121: first substrate
122: second substrate
130: lead frame
141: Protective sheet
143: prism sheet
150: light diffuser plate
160: Light source
170: reflective sheet
180: Lower cover

Claims (9)

A light diffusing plate, characterized in that it has a nonuniform local microlens array pattern on its surface. The non-uniform local microlens array pattern of claim 1, further comprising: a center lens; And a plurality of peripheral lenses positioned around the center lens and having a size smaller than that of the center lens. The light diffusing plate according to claim 2, wherein the diameter of the center lens is 100 µm or more. The light diffusing plate of claim 2 wherein the peripheral lens has a diameter of 90% or less of the central lens diameter. The light diffusing plate of claim 2, wherein a plurality of peripheral lenses are distributed stepwise around the central lens in a direction away from the central lens, and the diameter of the peripheral peripheral lenses is 90% or less of the diameter of the previous stage lens. The light diffusion plate of claim 5, wherein the peripheral lens is distributed in two to five stages. The light diffusing plate according to claim 1, wherein an uneven local microlens array pattern has an embossed structure on the side opposite to the side on which the pattern is formed. The light diffusing plate according to claim 1, comprising a plurality of silicon, urethane or acrylic beads therein. A liquid crystal display panel;
Light source; And
A light diffusion plate according to any one of claims 1 to 8, positioned between the liquid crystal display panel and the light source;
And the liquid crystal display device.

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