KR20070107911A - Backlight unit - Google Patents

Abstract

According to the present invention, a prism plate is disposed at the bottom of the optical sheet portion, and the light emitted from the lamp is vertically reflected toward the lamp, and only the light emitted at an angle passes through the front surface where the diffusion sheet is disposed. To provide a backlight unit that can improve the uniformity of the brightness of the present invention, for this purpose is a cover bottom on a plate made of a metal or synthetic resin material; A plate-shaped reflector seated on the cover bottom and made of a metallic material of white or silver color; A plurality of lamps arranged in parallel on the reflecting plate; And an optical sheet part mounted on the top of the plurality of lamps and having a prism plate disposed at the bottom thereof.

Description

Backlight Unit {BACK LIGHT UNIT}

1 is a configuration diagram of an embodiment of a general edge type backlight unit.

2 is a configuration diagram of an embodiment of a general direct type backlight unit.

3 and 4 are various configuration diagrams of the backlight unit according to the present invention.

5 is an exemplary view for explaining a principle of improving the luminance uniformity of a prism plate applied to the present invention.

6A is an exemplary view of measuring luminance uniformity of a direct backlight unit from which an optical sheet unit is removed.

6B is an exemplary view of measuring luminance uniformity of a direct type backlight unit in which a prism sheet is disposed;

Figure 6c is an exemplary view simulating the luminance uniformity of the direct type backlight unit according to the present invention.

7A and 7B are various cross-sectional views of the diffusion plate applied to the present invention.

<Explanation of symbols for main parts of the drawings>

10, 110: Cover bottom 20, 120: Reflector

30, 130: cold cathode fluorescent lamp 40, 140: diffusion plate

50, 150: diffusion sheet 60: prism sheet

70, 170: multilayer reflective polarizing film 180: prism plate

190: optical sheet portion

The present invention relates to a backlight unit of a liquid crystal display device.

In recent years, as the society enters the information age, the display industry that processes and displays a large amount of information has been rapidly developed.

As a result, a liquid crystal display device (LCD device) has been developed that can meet various demands of the user, such as thinning, weight reduction, and low power consumption. Currently, the existing cathode-ray tube (CRT) has been developed. It is in the spotlight as an alternative next-generation display device.

In general, a liquid crystal display may be classified into a liquid crystal panel displaying an image largely seen by a user, and a back light unit for increasing the brightness of the image.

The liquid crystal panel has a structure in which a lower substrate and an upper substrate on which one electric field generating electrode is formed are arranged to face each other, and then a liquid crystal layer is interposed therebetween. In this case, the liquid crystal has a thin and long molecular structure, optical anisotropy having an orientation in the array, and polarization property in which the array direction changes when an electric field is artificially applied. On the other hand, the liquid crystal panel changes the arrangement direction of the liquid crystal by applying an electric field to the liquid crystal interposed between the upper substrate, the lower substrate and the field generating electrodes provided on each of them, and expresses the image with the refractive index of the changed light. However, the brightness of the image implemented only by the liquid crystal panel is very low, making it difficult for the user to identify. Accordingly, a backlight unit including a plurality of light sources is provided on the back of the liquid crystal panel to supply light to the liquid crystal panel, thereby displaying an image that can be identified by the user.

In general, the backlight unit may be classified into an edge type and a direct type according to the arrangement of light sources. Among these, a direct type backlight unit capable of high brightness to be suitable for large size and large screen is widely used. At this time, the edge type backlight unit installs a light source at one edge of the liquid crystal display device, and irradiates the liquid crystal display panel with light incident from the light source through the light guide plate and the plurality of optical sheets, and the direct type backlight unit unit is a liquid crystal display device. A plurality of light sources are disposed directly below the light source, and light incident from the light sources is irradiated onto the liquid crystal panel through the diffusion plate and the plurality of optical sheets.

1 is a configuration diagram of an exemplary edge type backlight unit, and a general edge type backlight unit includes a light emitting part, a waveguide part, and an optical sheet part.

The light emitting portion is composed of a lamp 8 and a lamp housing 7 for protecting the lamp.

The waveguide is located on the light guide panel 2 which makes the light emitted from the lamp 8 into a uniform surface light source, and is located on the rear surface of the light guide plate to reflect the light from the lamp and concentrate it toward the liquid crystal panel side (front). It consists of a reflecting plate (1) that serves to prevent the loss of light from the back or side of the light guide plate.

An optical sheet unit is disposed on the light guide plate to diffuse light from the light guide plate to improve the brightness of the light (diffuser sheet) (3), located on the top of the diffusion sheet to collect light from the light guide plate to improve the viewing angle It is composed of a prism sheet (4, 5) and a protector sheet (6) to be located on the top layer of the backlight unit to prevent damage to the diffusion sheet and prism sheet and to secure a desired viewing angle. have.

At this time, as described above, the prism sheet is composed of two upper and lower prism sheets 5 and 4 in order to increase the light collecting efficiency, and a prism pattern is formed on the upper surface of each prism sheet 4 and 5. have.

That is, the edge type backlight unit illustrated in FIG. 1 includes a light emitting part composed of a lamp 8 and a lamp housing 7, and a light guide plate and a reflecting plate to generate a uniform light distribution on the liquid crystal panel. Optical sheet portions such as the diffusion sheets 3 and 6 and the prism sheets 4 and 5 are disposed between the light guide plate and the liquid crystal panel in order to adjust the direction of the emitted light and to secure a desired viewing angle.

In this case, as shown in FIG. 1, the edge type backlight unit must include two prism sheets 4 and 5 to obtain a desired viewing angle. Therefore, as the number of prism sheets increases, there is a problem that not only light loss occurs due to the feedback of light emitted from the light guide plate, but also disadvantages in terms of cost reduction. Recently, luminance, light uniformity and color purity are higher than edge type methods. High direct type backlight unit is being used more and more mainly around LCD TV.

2 is a configuration diagram of an embodiment of a general direct type backlight unit.

That is, the general direct type backlight unit as shown in FIG. 2 includes a cover bottom 10 on a plate made of metal or a synthetic resin material, and a white or silver metal material seated on the cover bottom. It comprises a reflector 20 on a plate, a cold cathode fluorescent lamp 30 arranged in parallel on the reflecting plate, and an optical sheet portion 90 mounted on the plurality of cold cathode fluorescent lamps.

The optical sheet unit 90 includes a diffusion plate 40 seated on a vertical upper end of the cold cathode fluorescent lamp (hereinafter, simply referred to as a 'lamp'), a diffusion sheet 50 seated on an upper end of the diffusion plate, and the diffusion sheet. It comprises a prism sheet 60 seated on the top and a reflective polarizing film (MOF) 70 of a multi-layer structure seated on the top of the prism sheet.

Meanwhile, a liquid crystal panel (not shown) manufactured through a separate process is mounted on the upper end of the optical sheet unit 90, and the liquid crystal panel is coupled to the direct type backlight unit through a top frame (not shown). As a result, the liquid crystal display device is completed.

In this case, the general direct-backlit backlight unit shown in FIG. 2 implements high brightness by connecting a plurality of lamps in parallel, but since the lamp is a line light source, an additional diffusion sheet is required to prevent the occurrence of lamp fringes, and the luminance due to the lamp fringes There is a problem that is not uniform.

In addition, in general, the direct backlight unit should maintain a thick air gap (the height of the cover bottom), and the presence of such an air gap greatly increases the degree of freedom of sheet combination of the direct backlight unit. The result is a degradation.

That is, due to the decrease in the degree of freedom of sheet combination due to the presence of the air gap, a diffuser plate 40 should always be disposed on the lowermost surface of the optical sheet unit 90 of the direct type backlight unit. Since the sheet or the prism sheet does not have self-supporting force, there is a problem that the performance improvement of the direct backlight unit is limited due to this structure.

Therefore, an object of the present invention for solving the above problems is that the prism plate is disposed at the bottom of the optical sheet portion, the light emitted vertically out of the light emitted from the lamp is totally reflected toward the lamp, shipped diagonally It is to provide a backlight unit capable of improving the uniformity of the brightness of the lamp by passing only the light to the front surface where the diffusion sheet is disposed.

In order to achieve the above object, the backlight unit according to an embodiment of the present invention, the cover bottom on the plate made of a metal or synthetic resin material; A plate-shaped reflector seated on the cover bottom and made of a metallic material of white or silver color; A plurality of lamps arranged in parallel on the reflecting plate; And an optical sheet part mounted on the top of the plurality of lamps and having a prism plate disposed at the bottom thereof.

In addition, in the present invention, the optical sheet unit, and a prism plate seated on the vertical upper end of the lamp; A diffusion sheet seated on top of the diffusion plate; And a reflective polarizing film (MOF) having a multilayer structure seated on top of the diffusion sheet.

Further, in the present invention, the optical sheet portion further includes a diffusion plate seated between the prism plate and the diffusion sheet.

In addition, the prism plate and the diffusion plate in the present invention is characterized in that it has an air gap (air gap).

In addition, in the present invention, the prism plate is a prism pattern (mount) formed on the transparent substrate, the transparent substrate is characterized in that it has a predetermined thickness in order to have a self-supporting force.

In addition, in the present invention, the forming direction of the prism acid is characterized in that it is horizontal to the longitudinal direction of the lamp.

In addition, the thickness of the transparent substrate in the present invention is characterized in that 1mm to 3mm.

Further, in the present invention, the light emitted vertically from the lamp to the prism plate is reflected by the prism acid and returned to it, and the light emitted from the lamp not perpendicular to the prism plate passes through the prism acid. It features.

In the present invention, the prism acid of the prism plate is a stamp method formed directly on the transparent substrate, an injection method formed by a mold, a method formed by a mechanical processing method, a method using an ultraviolet resin, a transparent substrate And a laminating method for joining the prism sheet with each other.

In addition, in the present invention, the pitch of the prism acid is characterized in that several micrometers to several hundred micrometers.

In addition, in the present invention, the angle of the prism peak is characterized in that 90 to 110 degrees.

Further, in the present invention, the radius of curvature of the vertices of the prism acid is characterized in that 0.1 to 0.5mm.

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

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

3 and 4 are various configuration diagrams of the backlight unit according to the present invention.

First, as shown in FIG. 3, the backlight unit according to the present invention has a feature that a prism plate 180 is disposed between the diffusion plate 140 and the lamp 300.

That is, the backlight unit according to the present invention includes a cover bottom 110 formed of a metal or a synthetic resin material, and a reflector plate shaped of a metal material having a white or silver color seated on the cover bottom. 120, a cold cathode fluorescent lamp 130 arranged in parallel on the reflecting plate, and an optical sheet unit 190 mounted on the plurality of lamps.

The optical sheet unit 190 may include a prism plate 180 mounted on a vertical top of the cold cathode fluorescent lamp (hereinafter, simply referred to as a “lamp”) 300, a diffusion plate 140 mounted on the top of the prism plate, The diffusion sheet 150 is mounted on the top of the diffusion plate and a reflective polarizing film (MOF) 170 of a multi-layer structure is mounted on the top of the diffusion sheet.

At this time, the prism plate 180 is a prism pattern formed on a transparent plastic substrate (Substrate), has a thickness of about 1mm ~ 2mm to have a self-supporting force, the acid forming direction of the prism is horizontal to the longitudinal direction of the lamp It must be deployed.

In addition, in the backlight unit according to the present invention, as shown in FIG. 3, the diffusion plate 140, the diffusion sheet 150, and the like are disposed on the prism plate 180 with a slight air gap g. 4, the diffusion plates 140 ′ and 150 may be disposed directly on the prism plate 180, as shown in FIG. 4, and in both cases, improved uniformity compared to conventional sheet configurations. You can see the effect.

The reason is possible because the first layer (Layer) through which the light emitted from the lamp 300 passes through is the prism plate 180 instead of the diffusion plate 140, and the principle thereof will be described below with reference to FIG. 5. do.

5 is an exemplary view for explaining the principle of improving the luminance uniformity of the prism plate applied to the present invention.

When the thickness of the backlight unit is reduced in the conventional direct projection backlight unit as described above, the first phenomenon is that the lamp pattern is visible. In other words, the area where the lamp is visible is bright, and the lamp is dark between the lamps, and because the light and dark patterns appear repeatedly, the luminance uniformity of the backlight unit is low, which causes a thick air gap inside the backlight unit. .

However, as shown in FIG. 5, when the first layer passing through the lamp has a prism shape, the light 31 exiting the front of the lamp is returned by total reflection, and the light 32 and 33 obliquely exits the lamp. Passes through the front surface, and this principle solves the occurrence of bright patterns in the vertical direction of the lamp.

Thus, as in the backlight unit according to the present invention shown in Figures 3 and 4, by placing the prism plate 180 on the upper end of the lamp, that is, the lowest surface of the optical sheet portion 190, the brightness of the upper end of the lamp is reduced The brightness of the left and right sides of the upper end of the lamp may be improved, and thus, the luminance uniformity of the backlight unit may be improved as a whole.

FIG. 6A illustrates an example of measuring luminance uniformity of a direct type backlight unit from which an optical sheet unit is removed, and FIG. 6B illustrates an example of measuring luminance uniformity of a direct type backlight unit on which a prism sheet is disposed, and FIG. It is an exemplary view simulating the luminance uniformity of a direct type backlight unit.

First, FIG. 6A illustrates a result of measuring luminance uniformity with a two-dimensional plane analyzer on a lamp) after removing an optical sheet unit 190 including a diffuser plate in a general direct backlight unit. As shown, if there is no sheet on the lamp, the lamp pattern is clearly seen and cannot be used as a backlight unit for the LCD in this state.

Next, Figure 6b is a two-dimensional planar analyzer after the prism sheet having a hill angle of 90 degrees applied to the present invention on the lamp under the conditions of FIG. As a result of measuring the luminance uniformity, the lamp position is dark and the lamp left / right becomes bright, and the phenomenon such as one lamp splitting into two can be observed. This phenomenon is caused by the reversal of the lamp vertical emission light described with reference to FIG. 5, and may have an effect of reducing the pitch between lamps by half of the original lamp distance, thereby contributing to the reduction of the backlight unit thickness. .

Finally, FIG. 6C is a light simulation for a backlight unit under the same conditions as the present invention in which a prism sheet is replaced with a prism plate having a thickness of about 2 mm in the same configuration as that of FIG. 6B. As shown in FIG. 6B, the brightness of the front of the lamp is lowered and the surroundings become brighter, and thus the lamp splits into two. That is, in FIG. 6C, a part that appears slightly darker than the surrounding area is where the lamp is located.

On the other hand, in the state in which the ramp pitch is already reduced by half as shown in FIGS. 6B and 6C, the diffuser plate 140 may be disposed with a slight air gap as shown in FIG. Alternatively, as illustrated in FIG. 4, the uniformity of the backlight unit may be easily secured through the method of directly distributing the diffuser sheet 150, and at the same time, the thickness of the backlight unit may be greatly reduced.

7A and 7B are various cross-sectional views of the diffusion plate applied to the present invention.

That is, as shown in the figure, the prism plate 180 is composed of a flat transparent substrate 181 and a prism pattern (prism mountain) 182 formed thereon.

In this case, as the transparent substrate 181, all of a transparent plastic series such as PMMA, PC, and Acryl can be used. As a method of forming the prism pattern 182, a substrate may be used. A stamp method, which is directly formed on a substrate, an injection method by a mold, a V-cutting method, which is a mechanical processing method, and a formation method using an ultraviolet resin may be applied. In addition, a method of laminating a transparent substrate and a prism sheet is also possible.

Meanwhile, in FIG. 7A, the thickness t of the substrate 181 is about 1 to 3 mm, which may have self-supporting force, and the pitch p of the prism acid 182 is several μm to It is effective in a wide range up to several hundred μm, and the angle of the mountain can be obtained at the same time with the frontal turning effect of light and the improvement of luminance uniformity in the range of 90 to 110 degrees.

In addition, the prism pattern 182 (the prism mountain), as shown in FIG. 7B, gives a round with a radius of curvature of about 0.1 to 0.5 mm to transmit a certain amount of light in the vertical direction of the lamp to further improve luminance uniformity. You can also improve.

The direct type backlight according to the present invention as described above, by placing the prism plate at the position where the light emitted from the lamp passes for the first time, even if the thickness of the backlight unit is reduced by reducing the vertical brightness of the lamp and increasing the brightness around the lamp There is an effect that the uniformity can be maintained high.

In addition, the present invention has the effect that the light utilization efficiency can be improved by improving the luminance uniformity of the backlight unit.

In addition, according to the present invention, as the uniformity of the luminance is improved, the distance between lamps may be reduced by half of a conventional lamp pitch, thereby reducing the thickness of the backlight unit.

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 (12)

A cover bottom on a plate made of metal or synthetic resin material; A plate-shaped reflector seated on the cover bottom and made of a metallic material of white or silver color; A plurality of lamps arranged in parallel on the reflecting plate; And The backlight unit is mounted on the top of the plurality of lamps, the backlight unit including an optical sheet portion disposed on the bottom surface. The method of claim 1, The optical sheet unit, A prism plate seated on the vertical top of the lamp; A diffusion sheet seated on top of the diffusion plate; And A backlight unit comprising a reflective polarizing film (MOF) of a multi-layer structure is mounted on the top of the diffusion sheet. The method of claim 2, The optical sheet unit, And a diffusion plate seated between the prism plate and the diffusion sheet. The method of claim 3, wherein And the prism plate and the diffusion plate have an air gap. The method of claim 1, The prism plate, A prism pattern (mount) is formed on the transparent substrate, and the transparent substrate has a predetermined thickness to have a self supporting force. The method of claim 5, And the direction in which the prism acid is formed is parallel to the longitudinal direction of the lamp. The method of claim 5, The thickness of the transparent substrate is a backlight unit, characterized in that 1mm to 3mm. The method of claim 5, Light emitted vertically from the lamp to the prism plate is reflected by the prism acid and returned And light emitted from the lamp not perpendicular to the prism plate passes through the prism acid. The method of claim 5, The prism acid of the prism plate is Any one of a stamp method formed directly on the transparent substrate, an injection method formed by a mold, a method formed by a mechanical processing method, a method using an ultraviolet resin, a laminating method of bonding a transparent substrate and a prism sheet The backlight unit, characterized in that formed by. The method of claim 5, And a pitch of the prism acid is in the range of several micrometers to several hundred micrometers. The method of claim 5, The angle of the prism peak is a backlight unit, characterized in that 90 to 110 degrees. The method of claim 5, The radius of curvature of the vertices of the prism acid is a backlight unit, characterized in that 0.1 to 0.5mm.

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