KR20080112846A - Optical sheet and back light assembly of luquid crystal display equipped with the prism sheet - Google Patents

Abstract

An optical sheet capable of changing density of protrusion according to location of lamp and back light assembly of liquid crystal display including the same are provided to improve an optical property of a back light assembly by evenly moving a light generated from a light source into a LCD panel. An optical sheet(210) capable of changing density of protrusion according to location of lamp comprises a body(214) and a protrusion part(213). In the body, the optical sheet is faced with a light source. The protrusion part is formed on the body, and comprises a first protrusion part(213a) and a second protrusion part(213b). The first protrusion part has the most high density distribution in a vertical direction. The second protrusion part is a different shape with the first protrusion part. A density of the first protrusion part gradually decreases based on a domain of the vertical direction of the light source.

Description

Optical sheet and back light assembly of luquid crystal display equipped with the prism sheet

1 and 2 are views for explaining a backlight assembly of a conventional direct type liquid crystal display device.

3 and 4 show the movement of light in a conventional backlight assembly.

5 is a configuration diagram of a backlight assembly according to a first embodiment of the present invention.

6 is a view for explaining an optical sheet according to a first embodiment of the present invention.

7 is a view for explaining the density distribution of the first protrusion and the second protrusion, according to the embodiment;

8 is a block diagram of a backlight assembly according to a second embodiment of the present invention.

9 is a view for explaining an optical sheet according to a second embodiment of the present invention.

10 and 11 are views for explaining the shape of the second protrusion in the upper protrusion according to the embodiment of the present invention.

12 is a graph for examining luminance characteristics of the optical sheet according to the first embodiment of the present invention.

The present invention relates to an optical sheet, and more particularly, to an optical sheet having different densities of protrusions in consideration of the position of a lamp.

The liquid crystal display device includes a liquid crystal display panel, which includes a TFT array substrate in which unit pixels are arranged and thin film transistors are arranged as switching elements for each unit pixel, and the TFT array substrate faces and expresses colors. A color filter substrate, and a liquid crystal layer filled between the two substrates.

Since the liquid crystal display panel does not emit light by itself, light must be supplied from the outside in order to express an image.

In addition, the LCD may be classified into an edge type and a direct type according to a structure in which a backlight, which is a light source, is installed. The edge type has a backlight assembly formed on the side of the liquid crystal display panel, and the direct type has a backlight assembly formed under the liquid crystal display panel.

Edge type liquid crystal display devices are mainly used for small liquid crystal display devices, and direct type liquid crystal display devices are mainly used for large liquid crystal display devices.

1 and 2 illustrate a backlight assembly of a conventional direct type liquid crystal display.

In the backlight assembly, as a light source, a plurality of bar lamps 103 are formed under a liquid crystal display panel (not shown) in parallel to each other and are protected by a lower cover 101 which is a mold frame. The upper surface of the lower cover 101 is provided with a reflecting plate 102 for reflecting the light of the lamp 103 to the liquid crystal panel, a plurality of lamps 103 are arranged on the reflecting plate 102. Further, a diffusion plate 104 for uniformly diffusing the light generated from the lamp 103 into the liquid crystal panel, a diffusion sheet 105 placed on the diffusion plate 104, and the diffusion sheet 105. A prism sheet 106 is further provided for refracting the light diffused by.

In addition, although not shown, in general, a protective sheet (not shown) is further provided on the prism sheet 106, and thus, a cost of the product is increased as a plurality of films or sheets are used in the direct backlight assembly in the related art. Will rise.

The diffusion plate 104 and the diffusion sheet 105 are supported by the edge of the lower cover.

A plurality of lamps 103, which are light sources, are formed on the reflecting plate 102 in parallel with each other, and the lamps 103 are supported by the lamp fixing members 111.

Electrodes for supplying power to the lamp are formed at both ends of the lamp 103, the lamp electrode is supported by the lamp support 112 formed on both sides of the lower substrate (101). In addition, an electrode supply line (not shown) for supplying power to the lamp is connected to both electrodes of the lamp 103.

The power supply lines are connected to each other to form a closed circuit around a single lamp. In the closed circuit, an inverter that converts a DC voltage applied from the outside into an AC voltage and supplies a current to the lamp is installed.

In general, a cold cathode fluorescent lamp (CCFL) is used as the lamp. Looking at the structure of the lamp, the lamp includes a light emitting part coated with a fluorescent material and an external device for applying a voltage to the lamp. It can be divided into electrode parts.

Meanwhile, a problem occurring in the conventional direct type backlight assembly will be described with reference to FIG. 3.

3 and 4 are diagrams showing the movement of light in a conventional backlight assembly.

Referring to FIG. 3, as a lamp is used as a light source, which is generally circular in cross section, the light emitted from the lamp is not evenly incident on all regions of the diffusion plate.

That is, as shown, the diffuser plate portion 3A positioned above the light source has a high density of incident light, but the diffuser plate portion 3B positioned in the region between the light source and the light source has a relatively high density of incident light. low.

In addition, the incident angle of the incident light is often greater than the magnitude of the critical angle at which the incident light is reflected in the portion 3B of the diffuser plate formed at the position of the region between the lamp and the lamp, and is reflected from the surface of the diffuser plate, and the reflected light is directed toward the lamp side. There is a problem that the movement to eventually lower the optical efficiency of the backlight assembly.

In addition, since the density of light incident on the region of the diffuser plate located in the area between the lamp and the lamp is low, the luminance of light emitted through the liquid crystal display becomes uneven and the image cannot be clearly displayed through the liquid crystal display. There is a problem.

The present invention is proposed to solve the above problems, the light generated from the light source to be evenly moved to the side of the liquid crystal display panel, an optical sheet capable of improving the optical characteristics of the backlight assembly and the liquid crystal display with the optical sheet It is an object to propose a backlight assembly of the device.

An optical sheet according to an embodiment is an optical sheet for moving light moved from a light source toward a liquid crystal display panel, wherein the optical sheet has a body portion facing the light source and a protrusion formed on the body portion. The protrusion includes a first protrusion formed to have the highest density distribution vertically above the light source, and a second protrusion having a shape different from that of the first protrusion, wherein the density of the first protrusion is vertically above the light source. It is characterized in that it gradually decreases based on the area.

In addition, the optical sheet of another embodiment is an optical sheet for moving the light from the light source to the liquid crystal display panel side, the optical sheet is a body portion for forming a substrate, and a lower protrusion for diffusing the light emitted from the light source And an upper protrusion formed on an upper surface of the body portion, wherein the upper protrusion is formed of a first protrusion and a second protrusion of different shapes.

According to another aspect of the present invention, a backlight assembly includes a lamp for generating light; A reflection plate installed under the lamp and reflecting light generated from the lamp; And an optical sheet disposed above the reflecting plate and configured to guide incident light toward a liquid crystal display panel, wherein the optical sheet has upper projections having different density patterns based on vertically upwards of the light source. It is characterized by.

Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention will be described in detail. However, the spirit of the present invention is not limited to the embodiments in which the present invention is presented, and those skilled in the art who understand the spirit of the present invention easily suggest other embodiments by adding, changing, adding, and deleting elements within the scope of the same idea. Although this may be done, this also falls within the scope of the spirit of the present invention.

5 is a configuration diagram of a backlight assembly according to a first embodiment of the present invention, and FIG. 6 is a view for explaining an optical sheet according to the first embodiment of the present invention.

First, a photograph is attached to FIG. 5 that the density of the convex pattern formed on the optical sheet according to the first embodiment is different. The backlight assembly of the embodiment includes a light source 205 for generating light and the light source ( A reflecting plate 206 disposed below the light source 205 is included to move the light generated from the 205 vertically upward.

The optical sheet 210 of the embodiment for improving light diffusion and condensing efficiency is disposed above the light source 205, and the liquid crystal display panel is positioned above the optical sheet 210.

In addition, a diffusion sheet may be further provided between the optical sheet 210 and the liquid crystal display panel. In the drawing of the embodiment, two sheets of the first diffusion sheet 201 and the second diffusion sheet 202 are stacked. It is also possible to use only one diffusion sheet according to the application of the embodiment.

The shape of the optical sheet 210 according to the first embodiment will be described with reference to FIG. 6.

The optical sheet 210 of the first embodiment includes a body portion 214 forming a substrate and a protrusion region formed to have a predetermined curved shape.

In particular, the optical sheet 210 is formed to have the first protrusion 213a and the second protrusion 213b having different shapes according to the position of the light source 205, and with respect to the position of the light source 205. A first protrusion 213a is formed in an area of the optical sheet located vertically upward from the light source 205, and a second is formed in an area of the optical sheet located vertically upward with respect to an area between the light sources 205. The protrusion 213b is formed.

Although only the first protrusion 213a is formed in the vertically upward area of the light source 205, the second protrusion may be formed in the area of the optical sheet positioned vertically above the light source 205. . However, since the density of the first protrusion is formed in a portion of the optical sheet corresponding to the vertically upward area of the light source 205, it should be remembered for the understanding of the embodiment of the present invention.

The light is diffused by the first protrusion 213a of the optical sheet formed above the light source 205, and the light is focused by the second protrusion 213b positioned in the area between the light sources. do.

To this end, the first protrusion 213a is formed in a finer pattern than the unit structure of the second protrusion 213b to diffuse light, and the density of each protrusion is one surface of the optical sheet, as shown in FIG. 7. The first protrusion 213a and the second protrusion 213b formed in the cross-sectional shape are different from each other, and the first protrusion 213a is formed so as to have the highest density in the vertically upward direction of the light source.

The second protrusion 213b is formed so as to have the highest density in an area vertically upward with respect to the area between the light sources.

In detail, referring to FIG. 7, the densities of the first protrusions and the second protrusions represent the number of curved shapes per unit area, based on the plan view of the optical sheet.

In FIG. 7, two cases are shown in relation to the density distribution of the first protrusion and the second protrusion, and the density of the first protrusion is the highest in the vertical upper portion of the light source 205, and the vertical direction of the light source 205 is shown. The density of the first protrusion is gradually reduced relative to the upper side.

In particular, the maximum density above the light source of the first protrusion 213a may be formed to have 60 to 95%, and is formed to have a density of 5 to 40% in the lowest density region. The second protrusion 213b is formed to have a maximum density of 60 to 95% and a minimum density of 5 to 40%.

In addition, when the distance between the light sources 205 is referred to as L, a region having the highest density and the lowest density of the first protrusion may be formed. That is, as shown in the lower graph of FIG. 7, the density of the first protrusion (or the second protrusion) may be linearly reduced or increased.

In particular, when the length of the section in which the region where the density of the first protrusion and the second protrusion are formed is set to D, the D has a size in the range of L / 30 to L / 5.

The shape of the first protrusion 213a and the second protrusion 213b may be defined as having a smaller size of the first protrusion 213a than the size of the second protrusion 213b. The size of the protrusions located vertically upward of the light source 205 may be seen to be more finely formed.

In addition, the protrusions may be manufactured by using a molding mold patterned in a shape opposite to the shape projected by the roll-coating method.

8 is a configuration diagram of a backlight assembly according to a second embodiment of the present invention, and FIG. 9 is a view for explaining an optical sheet according to a second embodiment of the present invention.

First, portions described separately from the shape of the optical sheet according to the first embodiment will be a pattern formed under the body portion of the optical sheet, and the pattern of protrusions formed on the upper side of the optical sheet will be the same as in the previous embodiment. Do.

In FIG. 8, a photograph is attached to show that the density of the convex pattern formed in the optical sheet according to the second embodiment is different. The backlight assembly of the embodiment includes a light source 305 for generating light and the light source 305. Reflector plate 306 is disposed below the light source 305 to move the light generated from the vertically upward.

An optical sheet 310 according to an embodiment for improving light diffusion and condensing efficiency is disposed above the light source 305, and a liquid crystal display panel is positioned above the optical sheet 310.

In addition, a diffusion sheet may be further provided between the optical sheet 310 and the liquid crystal display panel. In the drawing of the exemplary embodiment, two sheets of the first diffusion sheet 301 and the second diffusion sheet 302 are stacked. It is also possible to use only one diffusion sheet according to the application of the embodiment.

The shape of the optical sheet 310 according to the second embodiment will be described with reference to FIG. 9.

The optical sheet 310 may include a body 314 forming a substrate, an upper protrusion 313 on which convex portions patterns having different shapes are formed on the upper side of the body 314, and the body 314 of the body 314. The lower side has a lower protrusion 315 formed to face the light source 305.

In particular, the upper protrusion 313 of the optical sheet 310 may have the first protrusion 313a and the second protrusion 313b having different shapes according to the position of the light source 305 as in the case of the previous embodiment. The density distribution in which the first protrusion 313a and the second protrusion 313b are formed is the same as in the previous embodiment.

In addition, a lower protrusion 315 is formed on a lower surface of the optical sheet 310 to face the light source 305, and the lower protrusion 315 diffuses the light emitted from the light source 305. As it serves for the convex portions of the predetermined thickness protruding shape is randomly arranged.

Although the cross-sectional shape of the lower protrusion 315 is formed to have a predetermined radius of curvature, it may be formed in a prism pattern.

Thus, the light emitted from the light source 305 is diffused by the lower protrusion 315 of the optical sheet and then introduced into the body portion 314 of the optical sheet 310, and the body portion 314. The light moving upward from the light is diffused or collected by the upper protrusion 313.

That is, the light flowing into the optical sheet is diffused by the first protrusion 313a of the upper protrusion 313, is collected by the second protrusion 313b, passes through the upper diffusion sheet, and then moves to the liquid crystal display panel. Done.

10 and 11 are views for explaining the shape of the second protrusion in the upper protrusion according to the embodiment of the present invention.

In the foregoing description of the first and second embodiments, the protrusions formed on the upper surface of the optical sheet have first protrusions 213a and 313a and second protrusions 313a and 313b having different density patterns depending on the position of the light source. ).

The shapes of the second protrusions 313a and 313b provided in a larger shape than the first protrusions 213a and 313a are shown in FIGS. 10 and 11, and are formed in a prism array pattern as shown in FIG. 10. The cross section as shown in FIG. 11 may be formed in an array pattern of circles or ellipses.

FIG. 12 is a graph illustrating luminance characteristics of the optical sheet according to the first exemplary embodiment of the present invention, and it may be determined whether luminance distribution is evenly displayed based on the light source 205.

In detail, the luminance distribution of the light emitted from the light source 205 is shown by reference numeral 12A, and the luminance is higher as it is positioned above the light source 205.

In the case where the optical sheet according to the embodiment of the present invention is applied in the backlight, the luminance distribution is formed more evenly, as shown at 12B.

Further, in the case where the diffusion sheet is laminated and used together with the optical sheet according to the embodiment of the present invention, as shown at 12C, a uniform luminance distribution is achieved.

By the optical sheet and the backlight assembly of the liquid crystal display device provided with the optical sheet, the light generated from the light source is evenly moved to the liquid crystal display panel side, thereby improving the optical properties of the backlight assembly.

Claims (9)

An optical sheet for moving light moved from a light source toward a liquid crystal display panel, The optical sheet has a body portion facing the light source and a protrusion formed on the body portion, The protrusion includes a first protrusion formed to have the highest density distribution vertically above the light source, and a second protrusion having a shape different from that of the first protrusion. The density of the said 1st protrusion part is reduced gradually with respect to the area | region vertically upward of the said light source. The method of claim 1, The first protrusion is formed to have a density of 60 to 95% in the vertically upward area of the light source. The method of claim 1, And the density of the first protrusion is linearly reduced or increased. An optical sheet for moving light moved from a light source toward a liquid crystal display panel, The optical sheet is formed to have a body portion forming a substrate, a lower protrusion for diffusing light emitted from the light source, and an upper protrusion formed on an upper surface of the body portion. The upper protrusion is an optical sheet, characterized in that consisting of the first and second protrusions of different shapes. The method of claim 4, wherein And the first protrusion is formed in a number having a density of 60 to 95% in a region vertically upward of the light source on the surface of the body portion. In the backlight assembly is provided with an optical sheet for improving the optical characteristics of the light emitted from the light source, The optical sheet is composed of a body portion to which the light emitted from the light source is introduced, and an upper protrusion for emitting the light passing through the body portion to the upper side, The upper protrusion is a backlight assembly, characterized in that the protrusion density pattern is formed differently based on the vertical upward of the light source. The method of claim 6, The upper protrusion is made of a first protrusion and a second protrusion different in cross-sectional shape, And the first protrusion is arranged to have the highest density pattern in the vertically upward direction of the light source. A lamp for generating light; A reflection plate installed under the lamp and reflecting light generated from the lamp; And An optical sheet disposed on an upper side of the reflecting plate and configured to guide incident light toward a liquid crystal display panel; The optical sheet is a backlight assembly, characterized in that the upper protrusions having different density patterns with respect to the vertical upward of the light source is formed. The method of claim 8, A lower protrusion of a predetermined thickness convex shape is further formed below the optical sheet to face the light source. The lower protrusion is a backlight assembly, characterized in that the protrusions formed with a predetermined thickness is formed randomly.

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