KR20070073114A - Backlight unit and liquid crystal display having the same - Google Patents

Abstract

A backlight assembly and an LCD(Liquid Crystal Display) including the same are provided to use a prism light guide panel and two prism sheet with low price, thereby enhancing the light condensing function and brightness property. A light guide panel(60) is arranged at a side of a light source and includes a geometrical shape formed at a side thereof. The first prism sheet(70) is arranged at the upper portion of the light guide panel and includes plural prism members formed at a side thereof. The second prism sheet(80) is arranged at the upper portion of the first prism sheet and includes plural second prism members formed at a side thereof. The geometrical shape includes a prism shape. The trough direction of the prism shape is crossed with that of the first and second prism members. The trough direction of the first prism member is crossed with that of the second prism member with a predetermined angle.

Description

Backlight assembly and liquid crystal display including the same {Backlight Unit and Liquid Crystal Display having the same}

1 and 2 are an exploded perspective view and a cross-sectional view schematically showing the structure of the backlight assembly according to the present invention.

3 is a cross-sectional view showing an example of a first or second prism sheet according to the present invention.

4A and 4B are cross-sectional views showing another example of the first or second prism sheet according to the present invention.

5 and 6 are exploded perspective views for explaining the prism patterns of the light guide plate, the first and second prism sheets;

7A to 7D are light distribution diagrams when the backlight assembly according to the present invention is applied.

<Explanation of symbols for the main parts of the drawings>

40 lamp unit 50 reflector

60: light guide plate 70: first prism sheet

80: second prism sheet 90: protective sheet

The present invention relates to a backlight assembly and a liquid crystal display including the same. More particularly, the present invention relates to a backlight assembly and a liquid crystal display including the same, which can improve brightness and reduce costs by changing the structure of the backlight assembly.

In general, the liquid crystal display (LCD) is expanding its application range due to features such as lightweight, thin, low-power drive, full-color, high-resolution implementation. Currently, liquid crystal displays are used in computers, notebooks, PDAs, telephones, TVs, and audio / video devices. In the liquid crystal display, a light transmittance is adjusted according to an image signal applied to a plurality of control switches arranged in a matrix to display a desired image on a panel of the liquid crystal display.

Since the liquid crystal display does not emit light by itself, a light source such as a backlight assembly is required. The backlight assembly is divided into a direct method of dimming the front surface of the panel by arranging a light source on one side of the panel, and an edge method of reflecting and diffusing light on a light guide plate and a reflective sheet by disposing a light source on one side or multiple sides of the panel. Lose. Currently, the backlight assembly is being researched and developed with the technical goal of thinning, lightening, high brightness and high efficiency.

The backlight assembly of a conventional general structure comprises a lamp unit, a light guide plate, a reflecting plate, a diffusion sheet, a prism sheet and a protective sheet. 1 and 2, the conventional backlight assembly had to use a diffusion sheet and two prism sheets on the light guide plate to improve luminance. However, this has a disadvantage in that the thickness of the backlight assembly is increased, and the liquid crystal display device cannot cope with the tendency of thin and short. In addition, since the light emitted from the light guide plate is not evenly distributed over the entire emission surface and the amount of light emitted from the light source is relatively small, a low luminance region having a lower luminance than other parts appears in the vicinity of the light source. As a result, a dark portion may occur, and in particular, a bright line and a dark line generated in the outer portion may not be effectively used for lighting, and thus a light guide plate having a large size should be used, which is a factor in miniaturizing the liquid crystal display device. In addition, a moiré phenomenon may occur on the liquid crystal panel, which may reduce display quality of the liquid crystal display due to the appearance defect.

The present invention is to solve the above problems, by using a prism light guide plate and two low-cost prism sheet, it is possible to improve the condensing function to improve the luminance characteristics, improve the appearance defects, and reduce the cost An object of the present invention is to provide a backlight assembly and a liquid crystal display device including the same.

The present invention includes a light source, a light guide plate disposed on one side of the light source and having a geometric shape on at least one surface thereof, and a plurality of first prism parts disposed on at least one surface of the light guide plate in order to achieve the above object. A first prism sheet and a second prism sheet disposed on an upper portion of the first prism sheet and including a plurality of second prism portions formed on at least one surface thereof are provided. The geometric shape may include a prism shape. The valley direction of the prism shape and the valley direction of the first prism portion may cross each other, and the valley direction of the prism shape and the valley direction of the second prism portion may cross each other.

The valley direction of the first prism portion and the valley direction of the second prism portion may cross each other at a predetermined angle, and the predetermined angle may be greater than 0 degrees and less than 30 degrees.

The first prism portion may face the second prism sheet, and the second prism portion may be formed on an upper surface of the second prism sheet.

The backlight assembly according to the present invention may further include a reflector disposed under the light guide plate, and may further include a protective sheet disposed over the second prism sheet.

The present invention includes a light source, an incident surface to which light emitted from the light source is incident, a rear surface including a plurality of prism shapes extending from one side of the incident surface and having a valley direction perpendicular to the incident surface, and an exit surface facing the defecation. A light guide plate, a first prism sheet disposed on an upper portion of the light guide plate, the first prism sheet including a plurality of first prism portions formed on at least one surface, and a plurality of second prism portions disposed on at least one surface of the first prism sheet; It provides a backlight assembly comprising a second prism sheet. The prism-shaped valley direction and the first prism portion valley direction may cross each other, and the prism-shaped valley direction and the second prism portion valley direction may cross each other.

The valley direction of the first prism portion and the valley direction of the second prism portion may cross each other at a predetermined angle, and the predetermined angle may be greater than 0 degrees and less than 30 degrees.

The cross-section of the first prism portion and the second prism portion may be different from each other.

The present invention provides a liquid crystal display device comprising the backlight assembly according to the above.

Hereinafter, with reference to the accompanying drawings will be described in detail a preferred embodiment of the present invention.

1 and 2 are an exploded perspective view and a cross-sectional view schematically showing the structure of the backlight assembly according to the present invention.

Referring to the drawings, the backlight assembly includes a lamp unit 40, a light guide plate 60, a reflecting plate 50, a first prism sheet 70, a second prism sheet 80, and a protective sheet 90.

The lamp unit 40 includes a lamp 20 for generating light and a lamp reflector 30 surrounding the lamp 20, and a cold cathode tube (CCFL) is mainly used as the lamp 20. Alternatively, an external electrode fluorescent lamp (EEFL) or a light emitting diode (LED) other than the cold cathode tube may be used as a light source.

The light guide plate 60 serves to convert a linear light source emitted from the lamp unit 40 into a surface light source, and is an injection molded body of a transparent resin such as polymethyl methacrylate (PMMA). Likewise, as the distance from the lamp unit 40 is reduced, the thickness has a wedge-shaped cross section.

The side surface of the light guide plate 60, which is the thickest part of the wedge shape, is an incident surface to which light is incident, and an upper surface of the upper and lower surfaces of the light guide plate 60 is an emission surface from which light is emitted. The opposite side is the back surface of the exit surface, that is, the back surface.

In the present embodiment, the wedge-shaped light guide plate is illustrated, but the present invention is not limited thereto.

The rear surface of the light guide plate 60 includes a fine pitch prism shape 65 formed so that light incident into the light guide plate 60 has a uniform light distribution on the front surface of the liquid crystal display panel. The valley direction of the prism shape 65 is formed in a direction orthogonal to the longitudinal direction of the lamp. The prism shape 65 formed on the back surface of the light guide plate 60 sets the incident angle of the light incident on the exit surface by reflecting the light incident into the light guide plate 60 from both sides of the prism to be less than or equal to the critical angle of the light guide plate 60. do. Therefore, the emission of light to the liquid crystal display panel is increased. In the present embodiment, only the prism shape is illustrated, but may include various geometric shapes such as pillars and horns.

The reflecting plate 50 is disposed under the light guide plate 60 and receives light that is not reflected by the prism shape 65 of the light generated from the lamp 20 and traveling to the rear surface of the light guide plate 60. By reflecting toward the exit surface of the light guide plate 60 again, it reduces the loss of light incident on the liquid crystal display panel and improves the uniformity of the light transmitted through the exit surface of the light guide plate 60.

The first and second prism sheets 70 and 80 are disposed on an exit surface of the light guide plate 60 and include a prism pattern on at least one surface of the first and second prism sheets 70 and 80. That is, the upper surface of the first and second prism sheets 70 and 80 includes a prism pattern, and the lower surface of the light guide plate 60 toward the exit surface is flat. The prism patterns of the first and second prism sheets 70 and 80 cross each other with the prism shape 65 formed on the rear surface of the light guide plate 60. At this time, the valley direction of the prism shape 65 and the valley direction of the prism patterns of the first and second prism sheets 70 and 80 are adjusted such that an angle at which they cross each other is greater than 0 degrees and equal to or less than 90 degrees. For example, as illustrated, the valley direction of the prism patterns of the first and second prism sheets 70 and 80 is perpendicular to the valley direction of the prism shape 65 formed on the rear surface of the light guide plate 60, that is, 90 degrees. Formed by crossing.

The protective sheet 90 is disposed on the second prism sheet 80, and serves to protect the surface of the second prism sheet 80. The protective sheet 90 also diffuses light in order to uniformize light distribution. It also plays a role.

In the backlight assembly having the structure, light emitted from the lamp 20 is deflected by a predetermined angle due to the prism shape 65 formed on the rear surface of the light guide plate 60 and directed toward the exit surface. In addition, the first and second prism sheets 70 and 80 formed on the light guide plate 60 collect light so that the traveling direction of the light emitted from the emission surface is directed in the vertical direction.

3 is a cross-sectional view showing an example of the first or second prism sheet according to the present invention.

Referring to FIG. 3, the first or second prism sheets 70 and 80 may change body paths 70a and 80a through which light flows and the paths of the introduced light on the body parts 70a and 80a. It includes a plurality of prismatic parts (70b, 80b) having a triangular shape. In other words, the first prism sheet 70 includes a plurality of first prism portions 70b on the body portion 70a, and the second prism sheet 80 includes a plurality of first prism portions on the body portion 80a. And two prism portions 80b.

In this embodiment, the cross-sections of the first and second prism portions 70b and 80b are formed in the shape of a triangle, preferably an isosceles triangle. Of course, the present invention is not limited thereto and may be formed in the shape of an isosceles triangle having different lengths of bases. The vertex angles α of the first and second prism parts 70b and 80b may be formed to have various angles. In addition, the first prism portion 70b and the second prism portion 80b may be formed to have a cross-sectional shape of an isosceles triangle having different vertices. For example, the first prism portion 70b of the first prism sheet 70 formed on the light guide plate 60 has a cross-sectional shape of an isosceles triangle having a vertex angle α ₁ of 80 degrees, and the first prism sheet 70 The second prism portion 80b of the second prism sheet 80 formed on) may be formed to have a cross-sectional shape of an isosceles triangle having a vertex angle α ₂ of 100 degrees. This is desirable for vertical condensing light having various exit angles. In addition, the first prism portion 70b and the second prism portion 80b may be formed in a rounded cross-sectional shape instead of the triangle cross-sectional shape as described above.

4A and 4B are cross-sectional views showing another example of the first or second prism sheet according to the present invention. This is almost the same as the above-described example, and only the shape of the cross section of the prism portion formed on the body portion is different.

As shown in FIG. 4A, the prism sheets 71 and 81 may include body portions 71a and 81a through which light is introduced, and a plurality of prisms to change paths of the light introduced on the body portions 71a and 81a. The parts 71b and 81b may be formed, and the prism parts 71b and 81b may be formed in a hemispherical cross-sectional shape. In addition, as shown in FIG. 4B, the prism sheets 72 and 82 have a plurality of body portions 72a and 82a through which light is introduced, and a plurality of prism sheets 72 and 82 so as to change a path of the introduced light on the body portions 72a and 82a. Prismatic portions 72b and 82b may be included, and the prism portions 72b and 82b may have a rectangular cross-sectional shape.

As such, the pattern shape of the prism sheet may be formed in a shape having various shapes in order to vertically collect lights having various emission angles. In addition, the first prism portion and the second prism portion may not have the same cross-sectional shape, and may be formed to have different cross-sectional shapes.

As mentioned above, the first or second prism portion formed on the first or second prism sheet is adjusted such that an angle crossing the prism shape formed on the rear surface of the light guide plate is greater than 0 degrees and equal to or less than 90 degrees. This will be described in detail below.

5 and 6 are exploded perspective views for explaining the prism patterns of the light guide plate and the first and second prism sheets.

Referring to FIG. 5, the direction of the prism shape formed on the rear surface of the light guide plate 60 and the direction of the prism patterns of the first and second prism sheets 70 and 80 are vertically intersected. The prism shape of the light guide plate 60 is arranged in the Y-axis direction, and the prism patterns of the first and second prism sheets 70 and 80 are arranged in the X-axis direction. That is, a plurality of prismatic shapes 65 formed on the rear surface of the light guide plate 60 and extending in the X-axis direction may be repeatedly arranged along the Y-axis. The plurality of first prism portions 70b formed on the body portion 70a of the first prism sheet 70 and extending in the Y-axis direction may be repeatedly arranged along the X axis. In addition, the second prism sheet 80 may be similarly disposed on the body portion 80a, and a plurality of second prism portions 80b extending in the Y-axis direction may be repeatedly arranged along the X-axis.

Light emitted from a lamp disposed on one side of the light guide plate 60 includes lights having various angles of incidence, among which light incident in the Y-axis direction is caused by the prism shape 65 of the light guide plate 60. The path is changed in the X-axis or Z-axis direction, and the light incident in the X-axis direction is the first and second prism portions 70b and 80b included in the upper surfaces of the first and second prism sheets 70 and 80. ) Is condensed entirely in the Z-axis direction.

Accordingly, the light incident at various angles is focused and emitted through the light guide plate, the first and second prism sheets in a direction perpendicular to the liquid crystal display panel, that is, in the Z-axis direction.

As described above, an example in which the valley direction of the prism shape formed on the rear surface of the light guide plate and the valley direction of the prism patterns of the first and second prism sheets are vertically intersected is described, but is not limited thereto. The angle can be adjusted to be greater than 0 degrees and less than 90 degrees. Preferably, the valley direction of the first prism portion and the second prism portion is adjusted to be 30 degrees or less from a vertical axis of the valley direction of the prism shape formed on the rear surface of the light guide plate. That is, when the back surface of the light guide plate includes a prism shape extending in the X axis direction and repeatedly arranged along the Y axis, the first and second prism parts repeatedly arranged along the X axis are in the axial direction within 30 degrees of the Y axis. It is preferably formed to extend.

Referring to FIG. 6, the first prism portion 70b formed on the first prism sheet 70 and the second prism portion 80b formed on the second prism sheet 80 are mutually formed at a predetermined angle β. It may be formed to intersect. At this time, the angle β at which the first prism portion 70b and the second prism portion 80b cross each other is preferably 30 degrees or less.

The backlight assembly having such a structure forms the first prism portion 70b and the second prism portion 80b so as to cross each other at a predetermined angle β without concentrating them in parallel, thereby condensing light having various emission angles in the vertical direction. can do.

As described above, the backlight assembly of the present invention forms the first and second prism sheets described above on a light guide plate having a prism shape formed on a rear surface thereof, thereby obtaining an excellent light condensing function and improving luminance. In addition, it is possible to improve the appearance characteristics by preventing the occurrence of the dark portion, which has the effect of improving the yield and reliability. The prism sheet used in the present invention is easy to manufacture and inexpensive, so that the cost can be reduced and productivity can be improved.

The present invention is not limited to the examples described above, and various modifications and variations are possible and can be applied in various ways. For example, although the prism shape of the light guide plate is arranged in the Y-axis direction, the first and second prism portions are described in the example of being arranged in the X-axis direction, but the present invention is not limited thereto. Direction and the first and second prism portions may be arranged in the Y-axis direction.

7A to 7D are photographs showing the distribution of light emitted by applying the backlight assembly according to the present invention. FIG. 7A shows the distribution of light emitted from the prism light guide plate, FIG. 7B shows the distribution of light emitted from the first prism sheet, FIG. 7C shows the distribution of light emitted from the second prism sheet, and FIG. 7D shows the protection. The distribution of light emitted from the sheet is shown. Herein, the light distribution means a luminance value according to color, and the red color is brighter.

Referring to the drawings, the light having various emission angles emitted from the lamp is routed in the X-axis or Z-axis direction through the light guide plate, is vertically focused within 35 degrees of the Z-axis through the first prism sheet, and then the second prism sheet Through condensing on the Z-axis can be achieved to achieve vertical condensing. The diffusion is then through the protective sheet for a uniform distribution of light.

As described above, the backlight assembly of the present invention forms the first and second prism sheets described above on the light guide plate having the prism pattern formed on the rear surface thereof, thereby obtaining an excellent light condensing function and improving luminance. In addition, it is possible to improve the appearance characteristics by preventing the occurrence of the dark portion, which has the effect of improving the yield and reliability. Prism sheet used in the present invention is easy to manufacture and inexpensive, can reduce the cost and improve the productivity.

As mentioned above, although this invention was demonstrated in detail using the preferable Example, the scope of the present invention is not limited to a specific Example and should be interpreted by the attached Claim. In addition, those skilled in the art should understand that many modifications and variations are possible without departing from the scope of the present invention.

The backlight assembly according to the present invention uses a prism light guide plate and two low-cost prism sheets to improve the light condensing function to improve luminance characteristics, improve appearance defects, improve yield and reliability, and reduce manufacturing costs. There is an advantage to improve productivity.

Claims (17)

Light source; A light guide plate disposed on one side of the light source and including a geometric shape on at least one surface thereof; A first prism sheet disposed on the light guide plate and including a plurality of first prism portions formed on at least one surface thereof; And And a second prism sheet disposed on the first prism sheet, the second prism sheet including a plurality of second prism portions formed on at least one surface thereof. The method according to claim 1, And the geometric shape comprises a prism shape. The method according to claim 2, And the valley direction of the prism shape and the valley direction of the first prism portion cross each other. The method according to claim 2 or 3, And the valley direction of the prism shape and the valley direction of the second prism portion intersect each other. The method according to any one of claims 1 to 3, And a valley direction of the first prism portion and a valley direction of the second prism portion cross each other at a predetermined angle. The method according to claim 5, And said predetermined angle is greater than 0 degrees and equal to or less than 30 degrees. The method according to claim 1, And the first prism portion faces the second prism sheet. The method according to claim 1 or 7, And the second prism portion is formed on an upper surface of the second prism sheet. The method according to claim 1, The backlight assembly further comprises a reflector disposed under the light guide plate. The method according to claim 1, And a protective sheet disposed over the second prism sheet. Light source; A light guide plate including an incident surface to which light emitted from the light source is incident, a rear surface including a plurality of prism shapes extending from one side of the incident surface and having a valley direction perpendicular to the incident surface, and an exit surface facing the defecation; A first prism sheet disposed on the light guide plate and including a plurality of first prism portions formed on at least one surface thereof; And And a second prism sheet disposed on the first prism sheet, the second prism sheet including a plurality of second prism portions formed on at least one surface thereof. The method according to claim 11, And the valley direction of the prism shape and the valley direction of the first prism portion cross each other. The method according to claim 11 or 12, And the valley direction of the prism shape and the valley direction of the second prism portion cross each other. The method according to claim 11 or 12, And a valley direction of the first prism portion and a valley direction of the second prism portion cross each other at a predetermined angle. The method according to claim 14, And said predetermined angle is greater than 0 degrees and equal to or less than 30 degrees. The method according to claim 11 or 12, The cross-section of the first prism portion and the second prism portion has a shape different from each other. Claim 1, Claim 2, Claim 3, Claim 11 or Claim 12 comprising a backlight assembly according to any one of the liquid crystal display device.

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