KR20110062603A - Back light unit of luliquid crystal display including prism sheet - Google Patents

Abstract

PURPOSE: A liquid crystal display backlight unit is provided to distribute the brightness of light to a backlight unit and to secure maximum brightness value in one side of a liquid crystal panel. CONSTITUTION: An LED array is arranged in one side of a light guide plate. A prism sheet having a complex pattern is combined with a second pattern(103) that is processed to a first pattern and a second pattern and is located in the upper side of the light guide plate.

Description

LCD back light unit with prism sheet {BACK LIGHT UNIT OF LULIQUID CRYSTAL DISPLAY INCLUDING PRISM SHEET}

The present invention relates to a prism sheet for a liquid crystal display backlight unit. In particular, the present invention relates to a backlight unit for a liquid crystal display device comprising a prism sheet having a short side of the LED and having a composite pattern.

BACKGROUND ART Liquid crystal display devices have tended to be gradually widened due to their light weight, thinness, and low power consumption. The liquid crystal display device is used as a portable computer such as a notebook PC, office automation equipment, audio / video equipment, indoor and outdoor advertising display devices, and the like. The transmissive liquid crystal display device, which occupies most of the liquid crystal display device, displays an image by controlling an electric field applied to the liquid crystal layer to modulate the light incident from the backlight unit.

The backlight unit is roughly divided into a direct type and an edge type. The direct type backlight unit has a structure in which a plurality of optical sheets and a diffusion plate are stacked below the liquid crystal display panel and a plurality of light sources are disposed below the diffusion plate. BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the direct type | mold backlight unit which uses a thin cylindrical lamp as a light source.

The edge type backlight unit may be implemented to be thinner than the direct type backlight unit. Currently, LCD devices are changing from light source to LED. In particular, an edge type backlight unit for arranging LEDs that can be easily disposed is used.

In the direct type backlight unit that directly installs the light source over the entire area of the liquid crystal panel, light emitted from the light source is directly input to the liquid crystal panel, thereby obtaining bright luminance. However, the edge type has an economical advantage because the number of light sources is small, but it is difficult to obtain bright luminance on the entire liquid crystal panel because the number of light sources is small and the light is refracted. Therefore, in the case of the edge type backlight unit, an optical device for condensing light is essentially required.

In particular, in condensing light, it is important to distribute the luminance of light evenly over the entire liquid crystal panel. Moreover, the maximum luminance value should occur at the center of the front face of the panel. Designing an optical device that meets all of these requirements is a demand for economical edge type backlight units.

An object of the present invention is to provide a backlight unit for a liquid crystal display device in which the LED array is located on one side of the short length of the liquid crystal panel to solve the problems of the prior art. Another object of the present invention is to provide an optical device that guarantees a maximum luminance value at the center of the front face of the panel while distributing the brightness of light evenly over the front of the panel. It is still another object of the present invention to provide a prism sheet for maintaining the luminance of the front center of the panel in a 1Edge V-type LED array.

In order to achieve the above object, the backlight unit for a liquid crystal display device according to the present invention includes a light guide plate having a rectangular shape; An LED array arranged at one short side of the light guide plate; The prism sheet may be disposed on the light guide plate, and may include a prism sheet having a composite pattern in which a first pattern traveling in a first direction and a second pattern traveling in a second direction are combined.

The first direction in which the first pattern proceeds is a long side direction, and the second direction in which the second pattern proceeds is a short side direction and is perpendicular to each other.

The first direction may be a long side direction, and the second direction may be a direction in which ± 15 degrees is distorted with respect to the short side direction.

The first pattern is a cross-sectional shape cut in the direction of the short side of the prism sheet, two right angled isosceles triangles are arranged in series, the base is the same as the isosceles triangle, and one isosceles triangle is 2 to 3㎛ lower than the right isosceles triangle is higher Then comprise an arranged shape; The second pattern has a cross-sectional shape cut in the long side direction of the prism sheet, wherein two right angled isosceles triangles are continuously arranged, and a non-pattern section having no prism pattern at an interval corresponding to a multiple of the base of the right angled isosceles triangle is included. do.

The right isosceles triangle is a right isosceles triangle having two bases of 45 degrees and a base of 50 μm.

The ratio between the base of the rectangular isosceles triangle of the second pattern and the interval of the non-patterned interval may be any value selected from 1: 1 to 1:10.

The second pattern further includes a lens pattern having a semicircular cross-sectional shape at a central portion of the non-pattern section.

The present invention provides a backlight unit for a liquid crystal display device having low power consumption and low cost by using a small number of LED light sources by installing an LED array only on one side. In particular, in the case of the wide panel, by arranging the LED array along the short side of the liquid crystal panel, the power consumption can be further lowered using a smaller number of LED light sources, and the manufacturing cost can be lowered. In addition, it is possible to ensure a correct maximum luminance distribution in the central portion of the liquid crystal panel.

Hereinafter, the present invention will be described with reference to FIGS. 2 to 12. 2 is a cross-sectional view showing an edge type backlight unit including the LED array according to the present invention.

Referring to FIG. 2, the edge type backlight unit of the present invention includes an LED array 100 for irradiating light to a side surface of the LGP. The LED array 100 is coupled to the side of the light guide plate LG using a housing HOU. Optical sheets OPT are disposed between the light guide plate LG and the liquid crystal display panel LCDP. The optical sheets OPT may include at least one prism sheet, at least one diffusion sheet, and the like to diffuse light incident from the light guide plate LG, and may be substantially perpendicular to the light incident surface of the liquid crystal display panel LCDP. To deflect the path of light. The optical sheets OPT may further include a dual brightness enhancement film (DBEF). The guide panel GP surrounds the sides of the liquid crystal display panel LCDP and the edge type backlight unit and supports the liquid crystal display panel LCDP between the liquid crystal display panel LCDP and the optical sheets OPT. The cover bottom CB surrounds the housing HOU and the lower surface of the edge type backlight unit. The reflective sheet REF is disposed between the cover bottom CB and the light guide plate LG. The top case TP surrounds the top edge of the liquid crystal display panel LCDP and the side surface of the guide panel GP.

Various methods may be used to arrange LEDs in the edge type backlight unit as described above. For example, the arrangement of LED arrays on all four sides of a liquid crystal panel with an aspect ratio of 16: 9 is referred to as a '4 edge type'. When the LED array is disposed on the upper and lower horizontal sides, it is called '2Edge H', and the case where the LED array is placed only on one horizontal side is called '1Edge H'. In addition, when the LED array is arranged on the left and right vertical sides, it is called '2Edge V-type', and when the LED array is placed on only one vertical side, it is called '1Edge V-type'.

3A and 3B are diagrams schematically illustrating '2Edge H type' and '1Edge H type'. 3A and 3B illustrate the relationship between the prism sheet PR and the LED array 100 for convenience. If the LED array 100 is placed on as many sides as possible, a bright screen can be obtained, but it is disadvantageous in terms of cost because it requires a lot of LEDs. Therefore, '1Edge H-type', such as FIG. 3B, which arranges a high-performance LED on the upper side or the lower side along the horizontal side, is preferable. In this case, a prism sheet, which is a light collecting sheet, must be installed on the light guide plate in order to prevent luminance deterioration.

As the liquid crystal panel is changed from a structure having a 4: 3 ratio to a 16: 9 wide panel, more LEDs are required when adopting '1Edge H'. Therefore, it is conceivable to '1Edge V type' disposed on the vertical side with a relatively short length for the purpose of reducing the number of LEDs. FIG. 4 is a schematic view showing the LED array 100 arranged in a '1 Edge V-type' on the vertical short side of the prism sheet PR.

In the backlight unit for a liquid crystal display device of the '1 Edge V type', the center light profile of the front side of the liquid crystal panel is about 15 degrees. FIG. 5 is a graph showing luminance distribution measured per panel position in a liquid crystal panel front direction when a backlight unit of '1Edge V type' is used.

In order to correct the shift phenomenon of the center luminance value, the present invention has devised the following prism sheet. Hereinafter, exemplary embodiments of the present invention will be described with reference to FIGS. 6 to 15. FIG. 6 is a view illustrating a '1 Edge V-type' structure in which an LED array is arranged on one side of a prism sheet and a prism sheet according to Embodiment 1 of the present invention. FIG. 7A is a cross-sectional view taken along the line A-A 'of FIG. 6, and illustrates a first pattern of the prism sheet according to Example 1. FIG. FIG. 7B is a cross-sectional view taken along the line B-B ′ of FIG. 6, illustrating a second pattern of the prism sheet according to Example 1. FIG.

The prism sheet according to Example 1 has a shape combining two patterns. The first is the first pattern seen in the cross section cut along the short side of the prism sheet. Thus, the first pattern proceeds along the long side. The first pattern has a shape in which mountain patterns having a triangular shape are arranged in a line. In particular, the triangular shape consists of two shapes. The main triangular pattern is a right isosceles triangle with two base angles of 45 degrees and a vertex angle of 90 degrees. And the pitch value which is the space | interval of a main triangular pattern is about 50 micrometers. Therefore, in the geometric view, the height of the main triangle is arranged after two 25 μm main triangle patterns are successively arranged, and one sub triangle pattern is arranged. The sub triangular pattern is formed in the same shape as the main triangular pattern and has a height of only 2 to 3 μm. Thus, the sub triangular pattern has an isosceles triangle shape rather than a right triangle. And the height of the sub triangular pattern has about 22-23 micrometers.

The second one is the second pattern seen in the cross section cut along the long side of the prism sheet. Thus, the second pattern proceeds along the short side. The second pattern also has a shape in which mountain patterns having a right angled isosceles triangle shape adopted in the first pattern are arranged in a line. In the second pattern, right angled isosceles triangles each having two base angles of 45 degrees and a vertex angle of 90 degrees are continuously disposed with a 50 μm pitch value. However, after two right angled isosceles triangle patterns are continuously arranged, a pitch value of 100 μm of two right angled isosceles triangle patterns has no shape. The patternless spacing value without the prism may have any one selected from 50 μm, 100 μm, 150 μm, 200 μm, 250 μm, and 500 μm. That is, it has a multiple value of the pitch value of the rectangular isosceles triangle pattern of a 1st pattern and a 2nd pattern. That is, the ratio between the base of the right isosceles triangle and the patternless spacing may have any value selected from 1: 1 to 1:10. Among these, the most preferable result was obtained when the patternless spacing was 100 micrometers.

Accordingly, the prism sheet according to the first embodiment of the present invention has a complex shape in which the first pattern and the second pattern as described above are orthogonal to each other. In FIG. 6, it is shown that the direction of the mountain pattern pitch line of the first pattern and the direction of the mountain pattern pitch line of the second pattern intersect 90 degrees.

In another embodiment, the following prism sheet was devised. In Example 2, the 1st pattern was advanced horizontally, and the 2nd pattern was formed in the complex shape which cross | intersects, progressing in the direction rotated 15 degrees from the vertical direction. 8A and 8B are views showing a prism sheet according to the second embodiment of the present invention. 8A illustrates a case where the direction of the mountain pattern pitch line of the first pattern and the direction of the mountain pattern pitch line of the second pattern cross 105 degrees. 8B illustrates a case where the direction of the mountain pattern pitch line of the first pattern and the direction of the mountain pattern pitch line of the second pattern cross 75 degrees.

As another embodiment, in order to further improve light condensation, Embodiment 3 in which the shape of the second pattern is configured differently will be described. 9 is a cross-sectional view showing a second pattern of a prism sheet according to the third embodiment of the present invention. The prism sheet according to the third embodiment also has a pattern in which the first pattern and the second pattern are composited. In the prism according to the third embodiment, the first pattern has the same pattern as the first pattern described in the first and second embodiments. However, after two orthogonal isosceles triangular patterns are arranged successively in the second pattern, one lens pattern having a semicircular cross-sectional shape is disposed in the center of the space having a patternless interval of 100 μm without any pattern. It is preferable that the diameter of semi-circular cross-sectional shape is 50 micrometers which is a base of a right angled isosceles triangle here. That is, it has the same radius as 25 micrometers which is the height of a right angled isosceles triangle. The lens pattern having a semicircular cross-sectional shape may be formed as a hemispherical lens, or may be formed as a lens having a semi-cylindrical shape that is a blocked tunnel shape.

In another embodiment, Example 4 in which the prism surface of the prism sheet is processed to further increase the light diffusion effect is described. It is a figure which shows the state which the scratch added to the prism 103 surface of the prism sheet by Example 4 of this invention. A comb pattern may be added to the surface of each prism of the prism patterns according to the first to third embodiments of the present invention, so that the light is scattered and distributed evenly after passing through the prism.

As another embodiment, in order to increase the concealment effect, the fifth embodiment in which a bead is attached to the inside of the prism of the prism sheet will be described. 11 is a view showing a state in which the polydisperse or monodisperse beads 200 are attached to the inside of the prism 103 of the prism sheet according to the fifth embodiment of the present invention. By adding a plurality of polydisperse or monodisperse beads 200 inside each prism 103 of the prism pattern according to the first to fourth embodiments of the present invention, the physical strength of the prism acid pattern is reinforced, and the optical concealment effect Can be further increased.

When the prism sheets having the same composite pattern as those of the first and fifth embodiments were used, the panel center luminance of the liquid crystal display device using the 1Edeg V type back light unit in which the LED array was arranged on the short side of the liquid crystal panel was the maximum value. Can be expressed normally. FIG. 12 is a graph illustrating a distribution of maximum luminance values measured at the center of a panel in a liquid crystal display having a prism sheet and a '1 Edge H type' LED array according to embodiments of the present invention. As can be seen in Figure 12, it can be seen that the luminance value of the center portion is measured normally.

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.

BRIEF DESCRIPTION OF THE DRAWINGS The figure which shows the direct type | mold backlight unit which makes a thin cylindrical lamp the light source.

2 is a cross-sectional view showing an edge type backlight unit including the LED array according to the present invention.

3A and 3B are views schematically showing '2Edge H type' and '1Edge H type'.

4 is a schematic view showing an LED array arranged in a '1 Edge V-type' on the side of the prism sheet vertical short side;

FIG. 5 is a graph showing luminance distribution measured per panel position in a liquid crystal panel front direction when using a backlight unit of '1Edge V type'. FIG.

6 is a view showing a '1Edge V-type' structure in which the LED array is arranged on one side of the prism sheet and the prism sheet according to the first embodiment of the present invention.

FIG. 7A is a cross-sectional view taken along the line A-A 'of FIG. 6, illustrating a first pattern of a prism sheet according to Example 1. FIG.

FIG. 7B is a cross-sectional view taken along the line B-B 'of FIG. 6, illustrating a second pattern of the prism sheet according to Example 1. FIG.

8A and 8B show a prism sheet according to a second embodiment of the present invention.

9 is a cross-sectional view showing a second pattern of a prism sheet according to the third embodiment of the present invention.

10 is a view showing a state in which a scratch is added to the prism surface of the prism sheet according to the fourth embodiment of the present invention.

11 is a view showing a state in which polydisperse or monodisperse beads are attached to a prism of a prism sheet according to Embodiment 5 of the present invention.

FIG. 12 is a graph illustrating a distribution of maximum luminance values measured at the center of a panel in a liquid crystal display having a prism sheet and a '1 Edge H type' LED array according to embodiments of the present invention.

Description of the Related Art

TC: Top Case GP: Guide Panel

LCDP: Liquid Crystal Display Panel OPT: Optical Film

DIFF: diffuser LEDAR, 100: LED array

REF: reflector CASE: lamp housing

CB: Cover Bottom LG: Light Guide Plate

DBLU: Direct type backlight unit EBLU: Edge type backlight unit

PR: Prism Sheet 103: Prism

200: Bead

Claims (12)

A rectangular light guide plate; An LED array arranged at one short side of the light guide plate; And a prism sheet disposed on the light guide plate, the prism sheet having a composite pattern in which a first pattern traveling in a first direction and a second pattern traveling in a second direction are combined. The method of claim 1, And the first direction in which the first pattern proceeds is a long side direction, and the second direction, in which the second pattern proceeds, is a short side direction and perpendicular to each other. The method of claim 1, And the first direction is a long side direction, and the second direction is a direction shifted by ± 15 degrees with respect to the short side direction. The method of claim 1, The first pattern is a cross-sectional shape cut in the short side direction of the prism sheet, Two orthogonal isosceles triangles are arranged in succession, the base side being the same as the isosceles triangle, and one isosceles triangle whose height is 2 to 3 μm lower than the right isosceles triangle; The second pattern is a cross-sectional shape cut in the long side direction of the prism sheet, And two orthogonal isosceles triangles in a row and a non-pattern section having no prism pattern at intervals corresponding to multiples of the base of the right isosceles triangles. The method of claim 4, wherein The rectangular isosceles triangle is a right angle isosceles triangle having two bases of 45 degrees and a base of 50 μm. The method of claim 4, wherein And a ratio between the base of the rectangular isosceles triangle of the second pattern and the interval of the non-patterned interval is any value selected from 1: 1 to 1:10. The method of claim 4, wherein And the second pattern further includes a lens pattern having a semicircular cross-sectional shape at a central portion of the non-pattern section. The method of claim 7, wherein And a diameter of the lens pattern having the semicircular cross section is 50 µm. The method of claim 7, wherein The lens pattern having a semicircular cross-sectional shape is a hemispherical lens pattern having a diameter of 50 μm. The method of claim 7, wherein And the lens pattern having a semicircular cross-sectional shape is a semi-cylindrical lens pattern having a diameter of 50 µm. The method of claim 4, wherein And a scratch fringe on a surface of the prism pattern. The method of claim 4, wherein And a plurality of beads inside the prism pattern.

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