KR20060063508A - Optical sheet and back light unit using the same - Google Patents

Abstract

An optical sheet for injecting light generated from a plurality of light sources according to the present invention into a panel includes a diffuser plate for diffusing light from the light sources and a predetermined area (x) on both sides of the light incident surface of the diffuser plate. The first diffused lens having a first thickness and the second diffused lens having a second thickness smaller than the first thickness of the diffused lens mounted on the central region of the diffuser plate can be made uniform in visible light incident on the entire area of the panel. In this case, the luminance of the image displayed on the panel is made uniform.

Description

Optical sheet and back light unit using the same             

1 is a perspective view for explaining a general liquid crystal display device.

2 is a cross-sectional view taken along the line AA ′ of FIG. 1;

3 is a view for explaining a visible light path of a general liquid crystal display.

4 is a view for explaining a liquid crystal display device according to an exemplary embodiment of the present invention.

FIG. 5 is a cross-sectional view taken along line BB ′ of FIG. 4.

6 is a cross-sectional view for explaining a diffusion member according to a first embodiment of the present invention.

7A to 7E are views for explaining a preferred diffusion layer in the present invention.

8 is a view for explaining a visible light path of the liquid crystal display according to the first embodiment of the present invention.

9 is a cross-sectional view for describing a liquid crystal display according to a second preferred embodiment of the present invention.

10 is a view for explaining a visible light path of the liquid crystal display according to the second embodiment of the present invention.

FIG. 11 is a view for explaining a liquid crystal display device according to a third embodiment of the present invention; FIG.

<Description of Symbols for Main Parts of Drawings>

2, 20: liquid crystal display panel 10, 100: optical sheet

12: diffusion plate 130: diffusion member

131 and 132: diffusion layers 14 and 140: reflector plates

34, 340: Case 36, 360: Lamp

The present invention relates to an optical sheet and a backlight unit using the same. More particularly, the luminance of an image displayed on a panel is uniformed by making the amount of visible light incident on both end regions of the panel equal to the amount of visible light incident on the central region. An optical sheet and a backlight unit using the same are provided.

In general, liquid crystal displays (hereinafter referred to as "LCDs") have tended to be increasingly wider in application due to features such as light weight, thinness, and low power consumption. According to this trend, LCDs are used for office automation equipment, audio / video equipment, and the like. On the other hand, the LCD is controlled to display the desired image on the screen by adjusting the transmission amount of the light beam according to the image signal applied to the plurality of control switches arranged in a matrix form.

Since the LCD is not a self-luminous display device, a light source such as a back light is required. Such LCD backlight has a direct type and an edge type. In the edge type system, a lamp is installed outside the flat plate, and light is incident from the lamp onto the entire surface of the liquid crystal display panel using a transparent light guide plate. The direct type places several lamps in the plane. A diffusion plate is provided between the lamp and the liquid crystal display panel to maintain a constant space between the liquid crystal display panel and the lamp. Cold Cathode Fluorescent Lamp ("CCFL") method that supplies power by inserting electrodes at both ends of the glass tube of the lamp, and external electrode that supplies power to the electrode part that surrounds both ends of the glass tube of the lamp with metal material Fluorescent lamp (External Electrode Fluorescent Lighting: "EEFL") is a method.

1 is a perspective view illustrating a general liquid crystal display, and FIG. 2 is a cross-sectional view taken along line AA ′ of FIG. 1.

1 and 2, a conventional liquid crystal display device includes a liquid crystal display panel 2 for displaying an image and a backlight unit for irradiating uniform light onto the liquid crystal display panel 2.

In the liquid crystal display panel 2, liquid crystal cells are arranged in an active matrix between upper and lower substrates, and pixel electrodes and a common electrode for applying an electric field to each of the liquid crystal cells are provided.

Each of these pixel electrodes is connected to a thin film transistor used as a switch element. The pixel electrode drives the liquid crystal cell along with the common electrode according to the data signal supplied through the thin film transistor to display an image corresponding to the video signal.

The backlight unit includes a case 34, a reflective sheet 14 stacked on the front surface of the case 34, a plurality of lamps 36 positioned on the reflective sheet 14, and a plurality of lamps 36. The diffusion plate 12 and the optical sheet 10 are provided on it.

The case 34 converts the path of the light generated from the lamps 36 by reflecting the visible light generated laterally from the plurality of lamps 36 toward the front side, that is, toward the diffuser plate 12.

The reflecting plate 14 is disposed between the upper surface of the case 34 and the plurality of lamps 36 to reflect the light generated from the lamps 36 onto the case 34 to be irradiated toward the diffuser plate 12. Improve the efficiency of light.

Each of the plurality of lamps 36 includes a glass tube, inert gases inside the glass tube, and a cathode and an anode portion of a metal material surrounding both ends of the glass tube, and the plurality of lamps 36 may include a case 34. Are arranged side by side.

The diffusion plate 12 allows the light emitted from the plurality of lamps 36 to propagate to the liquid crystal display panel and to be incident at a wide range of angles.

The optical sheets 10 improve the front luminance of the liquid crystal display by collecting light emitted from the diffusion plate 12.

In the conventional liquid crystal display having the above structure, the diffusion plate 12 for diffusing the visible light generated from the lamps 36 has a uniform diffusion rate, so that the vertical direction of the direction in which the lamps 36 are arranged side by side That is, when the lamps 36 are arranged in the horizontal direction, the image brightness of both end faces in the vertical direction is lowered.

3 is a view for explaining a visible light path of a general liquid crystal display.

As shown in FIG. 3, the distribution of the amount of visible light emitted from the diffuser plate 12 onto the panel 2 is an area b above the lamp 36 and an area c between the lamps 36. The amount of visible light emitted through the side area (a) corresponding to the edge area of the panel 2 is relatively less than the amount of visible light emitted to the edge area of the panel (2), so that it is displayed on the panel (2) corresponding to both side areas (a). The brightness of the image to be lowered.

Accordingly, it is an object of the present invention to provide an optical sheet and a backlight unit using the same to diffuse visible light generated from a lamp as much as possible to make visible light incident on the entire surface of the panel uniform, thereby making the luminance of an image displayed on the panel uniform. Is in.

In order to achieve the above object, an optical sheet for injecting light generated from a plurality of light sources according to an aspect of the present invention into a panel includes a diffuser plate for diffusing light from the light sources, and both side surfaces of the light incident surface of the diffuser plate. A first diffusion lens having a first thickness mounted on the predetermined region x and a second diffusion lens having a second thickness smaller than the first thickness of the diffusion lens mounted on the central region of the diffusion plate are provided.

In addition, each of the diffusion lenses of the optical sheet according to the present invention may be formed of a micro lens array or a lenticular lens array.

In addition, each diffusing lens according to the present invention is characterized in that it is formed of a hemispherical lens having a cross-sectional shape of at least one of a semicircle or a semi-ellipse.

In addition, each diffusing lens according to the present invention is a cylindrical lens having a semi-circular or semi-elliptic cross-sectional shape, formed side by side with the light source, or a plurality of cylindrical lenses having a predetermined length having a semi-circular or semi-elliptical cross-sectional shape and a light source. Characterized in that formed side by side.

In addition, the first diffusion lens of the optical sheet according to the present invention is characterized in that the thickness gradually decreases as the distance from the end of the diffusion plate.

On the other hand, the optical sheet for injecting light generated from a plurality of light sources according to another aspect of the present invention to the panel, a diffusion plate for diffusing the light from the light sources and on the predetermined region on both sides of the light incident surface of the diffuser plate It has a diffusion lens mounted.

In addition, the backlight unit according to another aspect of the present invention includes an optical sheet for injecting light generated from a plurality of light sources into a panel, the optical sheet comprising: a diffusion plate for diffusing light from the light sources; And a diffusion lens having a first thickness mounted on both side predetermined regions of the light incident surface of the diffusion plate, and a diffusion lens having a second thickness smaller than the first thickness of the diffusion lens mounted on the central region of the diffusion plate.

Other objects and features of the present invention in addition to the above object will be apparent from the description of the embodiments with reference to the accompanying drawings.

Hereinafter, with reference to Figures 4 and 11 attached to a preferred embodiment of the present invention will be described in detail.

4 is a diagram for describing a liquid crystal display according to an exemplary embodiment of the present invention, and FIG. 5 is a cross-sectional view taken along line BB ′ of FIG. 4.

4 and 5, the liquid crystal display according to the present invention includes a liquid crystal display panel 20 for displaying an image and a backlight unit for irradiating uniform light onto the liquid crystal display panel 20. .

In the liquid crystal display panel 20, liquid crystal cells are arranged in an active matrix between upper and lower substrates, and pixel electrodes and a common electrode for applying an electric field to each of the liquid crystal cells are provided.

Each of these pixel electrodes is connected to a thin film transistor used as a switch element. The pixel electrode drives the liquid crystal cell along with the common electrode according to the data signal supplied through the thin film transistor to display an image corresponding to the video signal.

The backlight unit includes a case 340, a reflective sheet 140 stacked on the front surface of the case 340, a plurality of lamps 360 positioned on the reflective sheet 140, and a plurality of lamps 360. The diffusion member 130 is provided on the surface.

The case 340 reflects visible light generated laterally from the plurality of lamps 360 toward the front surface, that is, the diffusion member 130, to improve the efficiency of the visible light.

The reflector plate 140 is disposed between the upper surface of the case 340 and the plurality of lamps 360 to reflect light generated from the lamps 360 onto the case 340 to be irradiated toward the diffusion member 130. Improve the efficiency of visible light.

Each of the plurality of lamps 360 includes a glass tube, inert gases inside the glass tube, and a cathode and an anode portion made of metal covering both ends of the glass tube. The plurality of lamps 360 may include a case 340. It is arranged side by side in one direction on the phase.

The optical sheets 100 improve the front luminance of the liquid crystal display by collecting the visible light emitted from the diffusion member 130. That is, the optical sheets 100 change the path of the visible light so that the visible light is incident in the vertical direction of the panel 20.

The diffusion member 130 diffuses the visible light generated by the plurality of lamps 360 to the maximum, thereby making the luminance of the image displayed on the panel 20 uniform.

6 is a cross-sectional view for describing a diffusion member according to a first exemplary embodiment of the present invention.

Referring to FIG. 6, the diffusion member 130 according to the present invention is formed on the first diffusion layer 131 and the first diffusion layer 131 for diffusing visible light generated from the lamp 360, and the lamp 360. And a second diffusion layer 132 corresponding thereto.

The first diffusion layer 131 may include a high refractive index material (eg, 'beads') that may diffuse light, and may be formed in a plate shape, and may diffuse visible light generated from the lamp 360. Incident on the optical sheets 100 and supporting the second diffusion layer 132.

The second diffusion layer 132 is formed on the rear surface of the first diffusion layer 131, that is, on the surface where the visible light generated from the lamp 360 is incident.

The second diffusion layer 132 is formed by a predetermined length x on both side surfaces of which the amount of visible light incident on the panel 20 is relatively small. That is, the second diffusion layer 132 for diffusing the visible light incident in the diagonal direction from the lamp 360 in the oblique direction is not reflected according to the refractive index and is incident in the vertical direction to the panel 20. form x).

In this case, the predetermined length x of the second diffusion layer formed on both sides of the first diffusion layer 131 may be set according to the separation distance between the lamps 360 and the separation distance between the case 340 and the lamp 360. The thickness t of the second diffusion layer 132 is preferably set according to the separation distance between the lamp 360 and the first diffusion layer 131.

The second diffusion layer 132 may be formed of a micro lens array or a lenticular lens array, and may be disposed in a direction parallel to the arrangement of the lamp 360. In addition, the lens array formed by the second diffusion layer 132 is preferably formed densely to avoid there is a space area in the first expansion sancheung 131.

7A to 7E are views for explaining a diffusion layer preferable in the present invention.

As shown in FIG. 7A, the second diffusion layer 132 according to the present invention may be formed by arranging lenses having a cylindrical shape in a direction parallel to the arrangement of the lamp 360 in a semicircular or semi-elliptic cross section. have.

As shown in FIGS. 7B and 7C, the second expansion layer 132 may be formed in a semispherical shape on the entire surface, or may be formed in a semi-elliptic shape as a whole, or a combination of hemispherical shape and semi-elliptic shape.

In addition, as shown in FIG. 7D, the second diffusion layer 132 may include a plurality of cylindrical lenses in which a lens having a cross-section in the form of a semi-circle and a semi-ellipse is cut by a predetermined length (x). It may be formed by placing in a side by side.

As shown in FIG. 7E and also as shown in FIG. 6E, the second diffusion layer 132 may be formed of a lens having a honeycomb or polygonal shape in cross section.

Each of the lenses forming the second diffusion layer 132 may be arranged in a honeycomb and polygonal shape to minimize an empty area in which the second diffusion layer 132 is not formed on the first diffusion layer 131. It is preferable.

In addition, various types of lenses illustrated in FIG. 7 may be regularly or irregularly combined to form the second diffusion layer 132.

8 is a view for explaining a visible light path of the liquid crystal display according to the first embodiment of the present invention.

As shown in FIG. 8, the second diffusion layers 132 disposed on both end surfaces of the liquid crystal display device change the path in the vertical direction by diffusing the visible light incident in the diagonal direction from the adjacent lamp 360.

Accordingly, the amount of visible light emitted through the side area a corresponding to the edge area of the panel 20 is similar in comparison to the area b on the lamp 360 and the area c of the lamp 360. Thus, the luminance of the image displayed on the panel 2 becomes uniform.

9 is a cross-sectional view for describing a liquid crystal display according to a second exemplary embodiment of the present invention.

As shown in FIG. 9, a second diffusion layer 132 having a first thickness t by a predetermined length x is formed on both side surfaces of which the amount of visible light incident on the panel 20 is relatively small. A second diffusion layer 132 having a second thickness is formed on the first diffusion layer 131 except for the length x.

In this case, the thickness t of the first lens of the second diffusion layer 132 and the second region corresponding to the center region of the panel 20 are formed in regions corresponding to both end surfaces of the panel 20 by a predetermined length (x). The ratio of the thickness t of the lens is preferably set according to the separation distance between the lamps 360.

The predetermined length x of the first lens of the second diffusion layer formed on both side surfaces of the first diffusion layer 131 may be set according to the separation distance between the lamp 360 and the case 340.

10 is a view for explaining a visible light path of the liquid crystal display according to the second embodiment of the present invention.

As shown in FIG. 10, the thickness t of the second diffusion layer 132 formed at both ends of the first diffusion layer 131 by a predetermined length (x) is the thickness of the second diffusion layer 132 formed in the central region ( Since it is formed relatively larger than t), visible light incident from the lamp 360 to both end surfaces of the first diffusion layer 131 is not reflected but diffused and incident on the panel 20.

Therefore, the amount of visible light incident on both end surfaces of the panel 20 and the amount of visible light incident on the central region are uniform.

In addition, the second diffusion layer 132 formed in the central region of the first diffusion layer 131 diffuses the visible light generated from the lamp 360 to uniform the visible light incident on the panel 20, thereby providing a panel 20. The luminance of the image displayed at &quot;

11 is a cross-sectional view for describing a liquid crystal display according to a third exemplary embodiment of the present invention.

As shown in FIG. 11, the thickness t of the second diffusion layer 132 formed on both sides of the panel 20 having a relatively small amount of visible light incident by a predetermined length x is equal to the center region at the edge region. The second diffusion layer 132 having a second thickness is formed on the first diffusion layer 131 except for a predetermined length (x).

Therefore, the thickness t of the second diffusion layer 132 formed on both end surfaces of the first diffusion layer 131 by a predetermined length x is relatively larger than the thickness t of the second diffusion layer 132 formed in the central region. The second diffusion layer 132 on both ends of the first diffusion layer 131 is formed to be larger than the second diffusion layer 132 of the adjacent first diffusion layer 131. The visible light incident on the both ends of the diagonal line is not reflected but diffused and incident on the panel 20.

Therefore, the amount of visible light incident on both end surfaces of the panel 20 and the amount of visible light incident on the central region are uniform.

On the other hand, the thickness t of the second diffusion layer 132 mounted by the predetermined length x of the first diffusion layer 131 may sequentially increase the thickness t of the second diffusion layer 132 in the edge region. have.

As described above, in the backlight unit of the liquid crystal display according to the present invention, the luminance of the image displayed on the panel is equalized by making the amount of visible light incident on both end regions of the panel equal to the amount of visible light incident on the central region. It is effective.

The degree of diffusion of the diffusion layer for diffusing visible light generated from the lamp is set differently according to the distance from the lamp, so that the luminance of the image displayed on the panel can be made uniform.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the technical spirit of the present invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification but should be defined by the claims.

Claims (10)

In an optical sheet for injecting light generated from a plurality of light sources into the panel, A diffuser plate for diffusing light from the light sources; A first diffusion lens having a first thickness mounted on both side predetermined regions (x) of the light incident surface of the diffusion plate; And a second diffusion lens having a second thickness smaller than the first thickness of the diffusion lens mounted on the central region of the diffusion plate. The method of claim 1, Each of the diffusion lenses, An optical sheet characterized in that it is formed of a micro lens array or a lenticular lens array. The method of claim 1, Each of the diffusion lenses, An optical sheet comprising a hemispherical lens having a cross-sectional shape of at least one of a semi-circle and a semi-ellipse. The method of claim 1, Each of the diffusion lenses, An optical sheet comprising a cylindrical lens having a cross-sectional shape of a semi-circle or semi-ellipse, parallel to the light source. The method of claim 1, Each of the diffusion lenses, An optical sheet comprising a plurality of cylindrical lenses having a cross-sectional shape of semicircle or semi-ellipse having a predetermined length in parallel with the light source. The method of claim 1, Each of the diffusion lenses, Optical sheet, characterized in that arranged in a honeycomb or polygonal form. The method of claim 1, The first diffusion lens, An optical sheet, characterized in that the thickness gradually decreases as the distance from the end of the diffusion plate. The method of claim 1, The diffusion plate, An optical sheet comprising a high refractive index material for diffusing the light. In an optical sheet for injecting light generated from a plurality of light sources into the panel, A diffuser plate for diffusing light from the light sources; And a diffusion lens mounted on both side predetermined areas of the light incident surface of the diffusion plate. A backlight unit of a liquid crystal display device having an optical sheet for injecting light generated from a plurality of light sources into a panel, The optical sheet, A diffuser plate for diffusing light from the light sources; A diffusion lens having a first thickness mounted on both side predetermined regions of the light incident surface of the diffusion plate; And a diffusion lens having a second thickness smaller than the first thickness of the diffusion lens mounted on the central region of the diffusion plate.

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