KR100271036B1 - Backlight device - Google Patents

Abstract

PURPOSE: A back light device is provided to secure an optimum brightness distribution by partitioning a back surface of a light guide into a plurality of regions and forming a V-shaped protrusion pattern at every partitioned region. CONSTITUTION: A light source(150) is disposed at an edge of a light guide plate(180), and an unit for reflecting a light incident from the light source is formed on the light guide plate. The reflecting unit is formed by partitioning one plane(190) of the light guide plate into a plurality of regions, forming a V-shaped pattern(204) of the same shape at an entire surface of plural partitioned regions, and making a distance between the V-shaped patterns be different according to the position of the partitioned regions.

Description

BACK LIGHT DEVICE

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a backlight device of a liquid crystal display device used in a portable information communication device such as a personal computer, an audio visual (AV), a mobile computer, a game machine, a simulation device, etc., in particular, one component of the backlight device. It relates to a phosphor light guide plate.

In general, a liquid crystal display device includes a liquid crystal display and a TFT interposed between a pair of transparent substrates as shown in the exploded view of FIG. 1, and a liquid crystal display panel 10 including a driving IC or the like around an edge of the transparent substrate, and the liquid crystal display panel. It consists of a backlight device 20 and the case 1, 2 and the like located on the lower surface of 10.

The backlight device 20 converts line light incident from a light source into surface light and causes the surface light to be incident on the liquid crystal display panel 10.

The backlight device is largely divided into a direct type and an edge light type.

As shown in FIG. 2, which shows a plane cut along the line II-II of FIG. 1, a lamp 50 composed of a cold cathode tube or the like is mounted in the display area of the liquid crystal display panel.

The diffusion plate 40 is disposed on the lamp 50, and the light collecting plate 30 is disposed on the diffusion plate 40.

The reflector 60 is disposed on the lower surface of the housing 70, that is, under the lamp 50.

As shown in FIG. 3, which is cut along the line III-III of FIG. 1, the edge light type backlight device 22 includes a lamp 50 interposed between the U-shaped reflector 61 and the U-shaped reflector 61 disposed at an edge portion of the light guide plate 80. The reflector plate inlet is fixed to the edge of the light guide plate 80.

A reflecting plate 60 is disposed on the back side of the light guide plate 80, a diffuser plate 40 is disposed on the front side of the light guide plate 80, and a light collecting plate 30 is disposed on the diffuser plate 40.

In the direct type backlight device 21, since the lamp is located in the display area of the liquid crystal display panel, the luminance distribution of the lamp is very uneven, and the switching element of the liquid crystal display panel is easily deteriorated by the heat energy emitted from the lamp. The quality of falls.

Therefore, a light shielding film is formed along the pattern contour of the lamp to make the luminance distribution uniform, and a predetermined interval is provided between the lamp and the diffusion plate.

As a result, the thickness of the backlight device increases, and the advantages of the thinness of the liquid crystal display device cannot be utilized.

On the other hand, the edge light type backlight device 22 uses a transparent acrylic plate or the like as a light guide plate, and arranges a light source at an edge portion of the light guide plate.

If the dimming surface size is large, the thickness of the light guide plate is continuously changed so that the light guide plate is tapered, or the further away from the light source, the larger the area of the diffusion processing unit (dot printing unit) of the light guide plate is. Adjust

Therefore, the edge light type backlight device adjusts the uniformity of luminance by the light guide plate, and the thickness is thinner than that of the direct type backlight device because the lamp is disposed at the edge portion of the light guide plate.

In addition, since the lamp is disposed at the edge portion of the light guide plate, the heat energy emitted from the lamp hardly affects the switching element of the liquid crystal display panel and the like, which is advantageous for the quality of the liquid crystal display device.

In the above-described backlight device, an edge light type backlight device which is advantageous in thinning the liquid crystal display device and in which the thermal energy of the lamp does not greatly affect the liquid crystal display panel is particularly related to the present invention.

The edge light type backlight device has various structures limited by the prior art. In general, the structure and shape of the light guide plate are essential elements.

Some examples of the edge light type backlight device will be described in detail with reference to FIGS. 4 to 9.

4 is a cross-sectional view illustrating a mechanism of a conventional edge light type backlight device, and FIG. 5 is a cross-sectional view showing a modified structure of FIG. 4.

6 is a cross-sectional view of the rear surface 90 of the light guide plate 80 illustrated in FIGS. 4 and 5.

7, 8, and 9 are plan views illustrating patterns of geometric shapes formed on the rear surface 90 of the light guide plate 80 illustrated in FIGS. 4 and 5.

The light guide plate 80, which serves to transmit the light of the lamp to the liquid crystal display panel with a uniform luminance distribution, is typically a dot printed pattern 100 as shown in FIGS. 6A and 9 on a plate made of acrylic resin having a high light transmittance. Or a V-shaped bone pattern 105 or the like is formed as shown in FIGS. 6B, 7 and 8.

As described above, by forming the dot printing pattern 100 or the V-shaped bone pattern 105 on the light guide plate 80, the luminance of light incident on the display panel region may be uniformized.

Referring to FIG. 6B, the V-shaped bone pattern will be described as an example. As the V-shaped bone pattern moves from the n-th V-shaped bone pattern toward the n + n-th V-shaped bone pattern, that is, away from the lamp, the bone and the bone of the V-shaped bone pattern The interval between them is reduced in sequence.

The light guide plate on which the above pattern is formed is formed in a flat plate shape or a taper shape as shown in FIGS. 4 and 5.

In addition, the diffusion plate 40 formed on the light guide plate is made of PET polycarbonate or the like and is formed translucently.

Since the diffusion plate is made of translucent, it also serves to hide the dot printing pattern and the V-shaped bone pattern of the light guide plate.

Light passing through the diffusion plate is uniformly diffused and passes through the light collecting plate 30 provided on the diffusion plate.

The light collecting plate 30 collects the light passing through the student plate 40.

As an example, if the light has angles of Ø1 and Ø2 based on the normal line A as shown in FIG. 4, the light having the angle is refracted at a predetermined angle when passing through the light collecting plate 30, and the light is focused by the refraction. will be.

In some cases, two light collecting plates 30 may be arranged to improve luminance.

However, in the edge light type backlight device, there are various problems in the structure and shape of a conventional light guide plate.

First, in the structure in which the dot printing pattern 100 is formed on the rear surface 90 of the light guide plate as shown in FIG. 9, screen printing using volatilized ink, ultraviolet curable ink, or coloring ink containing titanium oxide having reflective particles causing diffuse reflection of light. When dot printing is performed by a method such as this, it is very difficult to adjust the viscosity of the printing ink because the diameter of the dot is gradually increased toward the direction away from the light source to increase the occupancy ratio of the light reflection layer per unit area of the light guide plate.

In more detail, the diameter of the light reflecting layer, that is, the dot print pattern 100 is formed to have a size of several tens of micrometers to several thousand micrometers.

Therefore, in the case of printing a dot print pattern, in the case of a dot print pattern having a small diameter of several tens of micrometers, since the ink for printing is difficult to pass through the screen, the viscosity of the ink for printing needs to be specified small. In the case of a dot printing pattern, it is necessary to increase the viscosity of the printing ink because the printing ink easily passes through the screen.

If the viscosity of the printing ink is adjusted to a high level due to the above conflicting conditions, a defect may occur in which the small diameter dot printing pattern is not partially printed. On the contrary, when the viscosity is lowered, a large diameter dot printing pattern may be smeared.

Therefore, it becomes very difficult to adjust both to the printing ink viscosity which satisfies both.

In addition to the above problems, since light is absorbed by the ink printed on the light guide plate and turned into heat, the luminance of the liquid crystal display is lowered and the light efficiency is lowered.

Secondly, in the structure of forming a V-shaped bone pattern 105 to cause diffuse reflection of light on the rear surface 90 of the light guide plate as shown in FIGS. 7 and 8, the light guide plate has a predetermined pattern such as longitudinal, transverse or elliptical shape and is far from the lamp. In the structure formed such that the interval between the pattern and the pattern is gradually narrowed toward the side, much trial and error and cost are required to find an optimal condition for achieving high brightness.

The present invention improves the means for diffusely reflecting the light incident from the edge portion of the light guide plate, that is, the means for multi-reflecting light in order to solve the problems of the conventional backlight device as described above.

The improvement method of this means divides the back part of the light guide plate which opposes the reflecting plate of a backlight device into several areas, and in each divided area, the geometric shape which has the same pattern, ie, U-shaped bone pattern, V-shaped bone pattern, etc. is engraved. Or, a number of embossed projection patterns, V-shaped projection patterns and the like are embossed.

Preferably, the geometric shape formed on the rear surface of the light guide plate is formed to be substantially parallel to the axis of the circular circle disposed at the edge portion of the light guide plate.

As an example, the V-shaped protruding pattern of the pattern is described. The spacing between the V-shaped protruding pattern and the V-shaped protruding pattern is different for each divided area of the light guide plate, and is formed in the same in each divided area.

By dividing the back surface of the light guide plate into several regions as described above, by forming different intervals between the V-shaped projection patterns for each region, even when the size of the light guide plate or the lamp is changed, it is easy to find the optimum luminance distribution with little time and cost. I can make it.

In addition, the problem of the conventional dot printing pattern is also improved.

The present invention improves the multi-reflective means of the light formed on the rear surface of the light guide plate, and forms a geometric shape such as a V-shaped protrusion pattern in the direction substantially perpendicular to the axis of the light source on the front surface of the light guide plate.

Unlike the rear surface, the front surface of the light guide plate does not need to form an interval such as a V-shaped projection pattern by dividing an area.

Since the geometric shape formed on the front surface of the light guide plate is configured to serve as a light collecting plate, it is more advantageous to realize high brightness and wide viewing angle.

Accordingly, it is an object of the present invention to efficiently configure a backlight device which is one component of a liquid crystal display device in order to have a high brightness and a wide viewing angle.

In particular, an object of the present invention is to efficiently configure a light guide plate, which is a component of a backlight device, so that the backlight device has an optimal luminance distribution.

1 is an exploded view of a liquid crystal display device,

2 is a conventional direct type backlight device,

3 is a conventional edge light type backlight device,

4 is a cross-sectional view for explaining the mechanism of the conventional edge-light backlight device,

5 is a cross-sectional view showing a modified structure of FIG.

6 is a cross-sectional view of the rear surface 90 of the light guide plate 80 shown in FIGS. 4 and 5;

7, 8, and 9 are plan views showing patterns of geometric patterns formed on the rear surface 90 of the light guide plate 80 shown in FIGS. 4 and 5;

10 is a cross-sectional view of the backlight device of the present invention,

11 and 13 are plan and three-dimensional views showing the pattern form of the geometric shape formed on the rear surface of the light guide plate of the present invention,

12 and 14 are plan and three-dimensional views showing patterns of geometric shapes formed on the front surface of the light guide plate of the present invention,

15 is a cross-sectional view showing a light guide plate having a constant thickness of the present invention.

16A to 16D are three-dimensional views showing another pattern of geometric shapes formed on the light guide plate of the present invention.

* Explanation of symbols for main parts of the drawings

21: direct type backlight device 22: edge light type backlight device

30, 130: light collecting plate 40, 140: diffuser plate

50, 150: Lamp 60, 160: Reflector

80, 180: LGP 90, 190: Back of LGP

91, 191: front surface of the light guide plate 100: dot printing pattern

105, 205: V-shaped bone pattern 204: V-shaped protrusion pattern

206: U-shaped bone pattern 211: Assisted protrusion pattern

The backlight device of the present invention will be mainly described with reference to FIGS. 10 to 16.

In the backlight device of FIG. 10, a light source, that is, a lamp 150, is disposed at an edge portion of the light guide plate 180 configured to taper to a transparent plate, as illustrated in FIG. 10, and a reflecting plate 160 is disposed to face the rear surface 190 of the light guide plate. The diffusion plate 140 is disposed to face 191, and the light collecting plate 130 is disposed on the diffusion plate 140.

The diffusion plate may use a holographic diffusion plate, and the light collecting plate may serve as a role.

In particular, the means for multi-reflecting the light incident on the light guide plate 180 in the lamp 150 divides one surface of the light guide plate (back surface 190 of the light guide plate in FIG. 10) into a plurality of areas (regions A, B, C, etc.) By forming a plurality of geometric shapes, such as the V-shaped projection pattern 204 having the same interval for each divided region of the light guide plate, and forming the interval between the geometric shapes differently depending on the position of the divided regions (A, B, C) Configured.

Hereinafter, the configuration and operation of the edge light type backlight device of the present invention will be described in detail.

As compared with the structure of the conventional edge light type backlight device, the edge light type backlight device of the present invention has the most distinctive feature as described above, which is a means for diffusely reflecting light incident on the light guide plate, that is, the geometric shape formed on the rear surface of the light guide plate. The pattern is efficiently constructed and arranged.

Therefore, the present embodiment will be described focusing on the structure and operation of the light guide plate, which is one component of the backlight device.

Example 1

As shown in FIG. 11, a V-shaped protrusion pattern 204 was formed on the back surface 190 of the transparent LGP 180 having a 4-inch size made of acrylic resin or the like.

The rear surface 190 of the light guide plate is divided into regions A to G, and each of the divided regions is provided with a plurality of V-shaped protrusion patterns 204 at substantially equal intervals so as to be substantially parallel to the axial direction of the lamp 150.

The V-shaped protrusion pattern 204 was formed to have a constant width d2, height d3, d2 100 mu m, and d 3 70 mu m.

The numerical values shown in Table 1 were applied to the width of each A to G on the rear surface of the light guide plate and the interval d1 between the V-shaped protrusion patterns 204 in the divided regions.

TABLE 1

More specifically, the widths of A, B, C, and D of FIG. 11 are 7.5 mm, 6 mm, 12 mm, and 12 mm, respectively, and V-shaped protrusion patterns formed in respective areas of A, B, C, and D are shown. 204 denotes d1 at intervals of 0 mm, 0.2 mm, 0.5 mm, and 0.4 mm, respectively.

When the backlight device was formed by forming the light guide plate as described above, the brightness distribution of the backlight device using the light guide plate of the first embodiment was more uniform when comparing the brightness distribution with the conventional backlight device. Could be easily formed.

After the light guide plate 180 was formed as described above, the V-shaped protrusion pattern 204 was added to the front portion 191 of the light guide plate such that it was substantially perpendicular to the central axis of the lamp 150 as shown in FIG. 12.

The V-shaped protrusion pattern 204 has a constant width d2, height d3, d2 of 100 μm, and d3 of 70 μm.

In addition, the interval d1 between the V-shaped protrusion patterns 204 was formed uniformly to 100 m.

As described above, a predetermined geometric shape is added to the front portion 191 of the light guide plate 180 to condense the light with uniform luminance distribution by means of multi-reflecting the light on the rear surface of the light guide plate, thereby widening the viewing angle.

Example 2

As shown in FIG. 13, the rear portion 190 of the light guide plate 180 having a size of 12.1 inches is divided into 16 (A to P) regions each having the same width of about 1 cm, and each divided region includes the axial direction of the lamp 150 and A plurality of V-shaped bone patterns 205 were formed at regular intervals so as to be substantially parallel.

The V-shaped bone pattern 205 has a constant width d2, height d3, d2 200 mu m, and d3 15 mu m constantly.

In addition, the value shown in Table 2 was applied to the interval d1 between the V-shaped bone patterns 205 in each divided area.

TABLE 2

After the light guide plate 180 was formed as described above, the V-shaped protrusion pattern 204 was added to the front portion 191 of the light guide plate such that it was substantially perpendicular to the central axis of the lamp 150 as shown in FIG. 14. The V-shaped protrusion pattern 204 formed on the front surface of the light guide plate had a width d2, a height d3, d2 100 μm, and d3 50 μm.

As described above, when the light guide plate was formed to form a backlight device, the same effect as in Example 1 was obtained when comparing the brightness distribution with the conventional backlight device.

In the first and second embodiments, the light guide plate 180 may be formed in a tapered form in order to more effectively adjust the uniformity of luminance. However, in some cases, the light guide plate may have the same thickness as in FIG. 15.

The geometric shape of the light guide plate described in Embodiments 1 and 2 is not limited to the pattern shape, and the shape of the assist projection pattern 211 as shown in FIGS. 16A and 16B or the U-shaped bone pattern 206 as shown in FIGS. 16C and 16D. It can be embossed or engraved.

It is preferable that d2 limiting the size of the geometric shape, which limits the size of the geometric shape, is 30 μm to 300 μm, and d3 has a shape within d2 × (0.05 to 1).

In the method of forming the geometric shape on the light guide plate, each of the molds having the geometric shape imprinted thereon may be extruded by combining the molds, or may be formed by cutting the light guide plate, that is, bite processing.

A feature of the present invention is that the backside 190 of the light guide plate is divided into a plurality of regions, and by forming a geometric shape having a different interval for each of the regions, the edge light type backlight device of the present invention is compared with the conventional edge light type backlight device. It is easy to adjust the brightness of the light and the light efficiency is increased.

Further, in the structure of the rear surface 90 of the light guide plate such as the conventional Figs. 8 and 9, the distance between the pattern and the pattern is gradually narrowed toward the farther away from the lamp 50, so it is optimal when the size of the light guide plate and the lamp is changed. Although it takes a lot of time and money to find the luminance distribution condition, applying the present invention can effectively find the optimal luminance distribution of the light guide plate by only a few simulations.

In addition, in the conventional backlight device of the edge light type, it is common to use two light collecting plates in order to increase the light collecting efficiency. However, in the backlight device of the present invention, a means capable of acting as a light collecting plate is added to the front surface of the light guide plate. Even if one light collecting plate is removed, the light collecting efficiency does not decrease.

The backlight device of the edge light type according to the present invention is an improvement of a means for uniformly reflecting light incident on the light guide plate so that the luminance distribution is uniformly maintained on all surfaces of the light guide plate.

That is, as shown in FIG. 10, the rear surface 190 of the light guide plate is divided into a plurality of regions, and a plurality of V-shaped protrusion patterns 204 having the same spacing are formed as one example for each of the divided regions.

As described above, by forming a means for uniforming the luminance distribution on the rear surface 190 of the light guide plate, it is possible to have an optimal luminance distribution, and it is possible to reduce trials and errors and costs for forming an optimal luminance distribution.

In addition, the light guide plate is less defective than the conventional dot printing pattern light guide plate and has an effect of stabilizing quality.

Claims (11)

A backlight device having a structure in which a light source is disposed at an edge portion of a light guide plate, and the light guide plate is provided with a means for multiplely reflecting light incident from the light source, wherein the means for multi-reflecting the light incident on the light guide plate is the light guide plate. Is formed by dividing one surface (first surface) of the substrate into a plurality of regions, a geometric pattern of the same shape is formed in front of the plurality of divided regions, and a distance between the geometric patterns is different from each other according to the positions of the divided regions. Backlight device, characterized in that. The backlight device of claim 1, wherein the geometric pattern formed on one surface (first surface) of the light guide plate is embossed or engraved. The backlight device of claim 1, wherein a geometric pattern formed on one surface (first surface) of the light guide plate is formed in a V shape. The backlight device according to claim 1, wherein the width of the geometric pattern formed on one surface (first surface) of the light guide plate is within 30 µm to 300 µm and the height is within 0.05 to 1 times the width. The backlight device of claim 1, wherein a geometric pattern formed on one surface (first surface) of the light guide plate is formed to be substantially parallel to an axis of the light source. The backlight device of claim 1, wherein a reflecting plate is added at a position opposite to a geometric pattern formed on one surface (first surface) of the light guide plate. The backlight device according to claim 6, wherein a diffusion plate is added to face the other surface (second surface) of the light guide plate, and a light collecting plate is added on the diffusion plate. The backlight device of claim 1, wherein a geometric pattern is added to the other surface (second surface) of the light guide plate in an embossed or intaglio form. The backlight device of claim 8, wherein the geometric pattern formed on the other surface (second surface) of the light guide plate is formed to be substantially perpendicular to the axis of the light source. The backlight device of claim 1, wherein the light guide plate is formed in a tapered shape. The backlight device of claim 7, wherein the diffusion plate is a holographic diffusion plate.

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