KR20110062506A - Backlight unit - Google Patents

Abstract

PURPOSE: A backlight unit is provided to offer viewing angle to a backlight unit by arranging a reflective optical component having slope aperture and to increase uniform luminance. CONSTITUTION: A plurality of light sources is arranged on a backlight unit and emits light. An optical plate(60) is arranged on the light source in order to diffuse light which is emitted from the light source. The optical plate has a plurality of openings(63). The opening has an inner wall.

Description

Backlight Unit {BACKLIGHT UNIT}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight unit (BLU), and more particularly to a backlight unit (BLU) provided with a reflective optical panel having an inclined aperture on its inner surface to provide uniform brightness. will be.

In a backlight unit (BLU) for LCD, a line light source or a point light source is used. The cold light source includes a cold cathode fluorescent lamp (CCFL), a hot cathode fluorescent lamp (HCFL), an external electrode fluorescent lamp (EEFL), and the like. LED is mainly used as a point light source. The backlight unit BLU is classified into a top-emitting type and a side-emitting type.

In the top emission type backlight unit (BLU) 10 using the LED (LED), as shown in Figure 1, the LED light source 12 is arranged on the printed circuit board 11, the LED light source 12 The diffusion plate 13, the diffusion sheet 15, the prism sheet 17 composed of a pair of prism sheets 17a and 17b, the protective film 19, and the like are laminated on the substrate. In the upward emission backlight unit (BLU) 20 using the cold cathode fluorescent lamp (CCFL), as shown in FIG. 2, the cold cathode fluorescent lamp light source 21 is arranged on the reflective film 22 and the cold cathode. On the fluorescent lamp light source 21, a diffusion plate 13, a diffusion sheet 15, a prism sheet 17 composed of a pair of prism sheets 17a and 17b, a protective film 19, and the like are stacked.

Up-emitting backlight units (BLUs) 10 and 20 can obtain a uniform brightness and an appropriate viewing angle by using the structure shown in FIGS. 1 and 2.

Although not shown in the drawings, the LED light source or the cold cathode fluorescent lamp is disposed on the side of the light guide plate, and the side emission type backlight unit in which a diffusion sheet, a prism sheet composed of a pair of prism sheets, and a protective film are stacked on the light guide plate. Even with (BLU), uniform luminance and an appropriate viewing angle can be obtained.

However, according to the requirements of LCD, the number of optical components such as a reflective film, a diffusion plate, a diffusion sheet, a prism sheet, and a protective film applied to the backlight unit BLU is controlled. Except for this, approximately 4 to 5 optical components are required. This essential optical component is a major factor that increases the manufacturing cost of the backlight unit (BLU) and further increases the manufacturing cost of the LCD (LCD). Therefore, LCD or backlight unit (BLU) manufacturers or related component manufacturers are developing various technologies to reduce the number of these necessary optical components, but there is a limit in reducing the manufacturing cost of the backlight unit (BLU). At present, it is required to further reduce the number of such optical components required to significantly reduce the manufacturing cost of the backlight unit (BLU).

Accordingly, an object of the present invention is to reduce the number of essential optical components of the backlight unit (BLU).

Another object of the present invention is to provide a uniform brightness and a narrow viewing angle to the backlight unit BLU by disposing a reflective optical component having an opening having an inclined inner surface on a light source.

In order to achieve the above object, a backlight unit according to the present invention comprises: a plurality of light sources arranged on a substrate to emit light; And an optical plate disposed on the light source for diffusing the light emitted from the light source and narrowing the time of view, the optical plate having a plurality of openings, the opening having a larger exit and larger diameter than the inlet. It has a photographic inner wall.

Preferably, the surface of the optical plate is either a reflective metal or a reflective metal film, and a reflective film may be disposed on a substrate on an outer portion of the light source.

Preferably, a transparent optical plate support for supporting the optical plate may be disposed on either the upper surface or the lower surface of the optical plate.

Preferably, the curved surface may be formed on any one of the upper surface, the lower surface, and the upper and lower surfaces of the optical plate support part.

According to the present invention, the light emitted from the light source at a large inclination angle with respect to the vertical line of the light source is changed to a direction substantially close to the vertical line and passes through the opening, and is also emitted in a direction close to the vertical line. A portion of the reflective optical plate is sequentially reflected on the lower surface and the reflective film to pass through the opening relatively far from the light source, thereby removing an excessively bright area. Therefore, an appropriate viewing angle and uniform brightness can be provided to the LCD panel.

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

3 is an exploded perspective view schematically showing a structure of an upward emitting backlight unit applied to the backlight unit of the present invention, and FIG. 4 schematically shows the overall structure of the optical plate 60 shown in FIG. It is an enlarged view of a structure. Parts having the same structure and action are given the same reference numerals.

Referring to FIG. 3, the upward emission backlight unit 100 includes a printed circuit board 51, a light source 52, and a reflective optical plate 60. In addition, an optical sheet, for example, a diffusion sheet 55, a protective film 19, and the like may be sequentially disposed on the reflective optical plate 60. On the surface of the printed circuit board 51 where the light source 52 is not disposed, the light emitted from the light source 52 does not pass through the opening 63 (shown in FIG. 4) of the optical plate 60. When reflected, a reflective film 53 (shown in FIG. 5) may be formed to reflect this light and allow it to pass through the opening 63 of the optical plate 60.

Here, the light sources 52 are arranged in a grid on the printed circuit board 51. The light source 52 employs, for example, an LED (LED) emitting white light or monochromatic light. The white light source can be obtained by combining semiconductor diodes emitting red light, green light, and blue light, or by covering a resin containing a fluorescent substance in an LED (LED) emitting blue light or ultraviolet light.

In addition, as shown in FIG. 4, the reflective optical plate 60 has a structure in which a plurality of openings 63 are arranged in a direction orthogonal to the entire surface of the main body 61. The main body 61 is a rectangular flat plate, for example. The inlet and outlet of the opening 63 are square, and the inner wall 63c of the opening 63 forms an inclined surface in which the outlet area becomes larger than the inlet area from the inlet to the outlet. Of course, although not shown in the drawings, the openings may be arranged irregularly, and the inlet and the outlet of the openings may be various shapes other than square. The main body 61 has reflectivity. In particular, the lower surface of the main body 61 and the inner wall 63c of the opening 63 must have reflectivity, and preferably have a reflectivity of 80% or more.

On the other hand, the optical plate 60 forms a metal plate or a metal sheet, forms a reflective resin, coats a metal film having a better reflectance on the molded metal plate or a metal sheet, or coats a metal film having a good reflectance on the molded resin sheet. It can be produced by the method. It is also possible to produce an optical plate by the method different from the above-mentioned method. In addition, the heat emitted from the light source or the heat absorbed by the optical part without passing through the light source may include a metal plate or a metal sheet for the optical plate and a metal for a housing (not shown) of the backlight unit BLU (not shown). By connecting to each other by) can be quickly emitted to the outside of the backlight unit (BLU).

In addition, although not shown in the figure, the openings may be arranged irregularly, and the inlet and outlet of the openings may have various shapes other than square. In LCD, the area ratio of the outlet and the inlet of the opening may vary depending on the luminance uniformity or the time required in the horizontal and vertical directions. Accordingly, the inlet and the outlet of the opening may have various shapes such as one shape, for example, rhombic, elliptical, rectangular, closed curve, etc., and the inclined inner wall of the opening may be in the horizontal and vertical direction of the LCD. You may have different angles of inclination with respect to it. The openings may also be arranged diagonally instead of orthogonally. The openings may also be arranged more densely in any direction rather than regularly arranged. Moreover, although the space | interval of an opening part may not be constant and may vary, for example, it is also possible to make a space | interval of an opening part smaller in the part between a light source and a light source rather than directly over a light source. In addition, the inlet and the outlet of the opening may have different shapes.

In addition, the optical plate 60 can be replaced by the optical plate 70 shown in FIG. 6A or the optical plate 80 shown in FIG. 6B. That is, in the case of the optical plate 70, for example, the square opening 73 is arranged only in a required partial region of the entire surface of the rectangular body 71. In the case of the optical plate 80, for example, the circular openings 83 are uniformly arranged throughout the surface of the circular body 81. Of course, the optical plate 60 may be a planar or curved surface of various shapes depending on the use instead of a square or a circle.

In addition, when the optical plate 60 is thin, as shown in FIG. 6A, as the transparent support of the optical plate 60, a transparent plate 75 much thicker than the optical plate 60 may be used. By arrange | positioning on the lower surface of 60, the curvature of the optical plate 60 can be prevented. Of course, although not shown in the figure, it is also possible to arrange the transparent plate 75 on the upper surface of the optical plate 60. At this time, it is possible to contact the transparent plate 75 to the optical plate 60 or to adhere the transparent plate 75 to the optical plate 60. In addition, in order to increase the diffusivity of the light or to prevent the light emitted immediately above the light source from being reflected from the lower surface of the optical plate and incident to the light source, a curved surface is formed on the upper surface, the lower surface, or both the upper and lower surfaces of the transparent plate 75. It is also possible. The curved surface of the transparent plate 75 can be freely selected according to the use from a wave type, a pyramid type, a lenticular type, an emboss type, and the like.

5 is an exemplary view showing a path that progresses while light emitted from a light source passes through an opening of an optical plate in the backlight unit BLU of the present invention.

As shown in FIG. 5, the inlet 63a of the opening 63 is formed through the main body 61 so as to have a smaller area than the outlet 63b, so that the inner wall 63c of the opening 63 may be inclined. Achieve. Although the area ratio of the exit 63b and the inlet 63a varies with brightness uniformity and time required for the backlight unit, 1.5 to 3 times is preferable. Although the interval between neighboring outlets 63b is W1, although not shown, it may be zero depending on the uniformity or time of the required luminance. The width W2 of the outlet 63b is preferably in the range of about 10 μm to 1 mm, and more preferably in the range of about 20 μm to 100 μm. The height of the opening 63, that is, the thickness of the main body 61, is in the range of about 10 µm to 1 mm, and more preferably in the range of about 20 µm to 100 µm. On the other hand, when the optical plate 60 is applied to a general display panel such as an advertising panel, an instruction panel, a signal panel, or the like, the size of the optical plate 60 is larger than when the optical plate 60 is applied to the backlight unit. It may be big. That is, the width W2 of the outlet 63b is preferably in the range of about 0.1 mm to 10 mm, more preferably in the range of about 0.2 mm to 5 mm. The height of the opening 63, that is, the thickness of the main body 61, is preferably in the range of about 0.1 mm to 10 mm, more preferably in the range of about 0.2 mm to 5 mm.

The inclination angle of the inner wall 63c of the opening 63 is preferably in the range of about 15 degrees to 30 degrees with respect to the vertical line, and more preferably in the range of about 20 degrees to 25 degrees.

In addition, the lower surface of the main body 61, the upper surface, and the inner side wall 63c of the opening 63 have reflectivity, and preferably have a reflectance of 80% or more.

Thus, as shown in FIG. 5, light sources 52a and 52b emitted from the light sources 52, for example, LEDs, on the printed circuit board 51 are directly on the light source 52 without any reflection from the main body 61. It passes through the located opening 63, that is, the first opening. The light 52c emitted from the light source 52 sequentially reflects the lower surface 61a of the main body 61 on the right side of the first opening and the reflective film 53 on the printed circuit board 51 so as to sequentially reflect the first light. It passes through the opening 63 adjacent to the opening, that is, the second bend. The light 52d emitted from the light source 52 includes the lower surface 61a of the main body 61 on the right side of the first opening, the reflective film 53 on the printed circuit board 51, and the second opening. The inner wall 63c is sequentially reflected to pass through the outlet of the second opening in a substantially vertical line. The light 52e emitted from the light source 52 reflects the inner wall 63c of the second opening portion and passes through the outlet of the second opening portion in a substantially vertical line. Of course, although not shown in the figure, it is also possible for the light emitted from the light source 52 to be reflected a plurality of times and pass through the opening on the right side of the second opening, for example, the third, fourth and fifth openings.

Meanwhile, in FIG. 5, for convenience of description, the light source, for example, two LEDs are disposed on the printed circuit board and two openings are formed in the main body of the optical plate. Of course, the number is not limited to this.

Thus, as shown in FIG. 5, the entirety of the light emitted from the light source 52 does not pass through the opening 63 on the vertical line, that is, the first opening, and a substantial portion of the light emitted from the light source 52 The reflection passes through the adjacent second openings, third openings, and the like, so that light can be dispersed, that is, a diffusion effect can be obtained. In addition, the light incident obliquely through the inlet of the opening is reflected one or more times by the inclined surface which is the inner wall of the opening and passes through the outlet of the opening in a direction close to the vertical line. Therefore, the optical plate of the present invention can be regarded as simultaneously performing the functions of the conventional diffusion plate or the diffusion sheet and the prism sheet.

When the maximum inclination angle of the light passing through the opening 63 with respect to the vertical line of the opening 63 is calculated, the height of the opening 63 is H, the maximum exit width of the opening 63 is W2, and the opening 63 When the maximum inlet width of W is W3, and the angle where the advancing direction of the light emitted from the light source 52 forms a vertical line is θ, the value of θ can be represented by Equation (1).

 θ = arctan [(W2 + W3) / 2H]

In Equation 1, a viewing angle may be adjusted according to the value of θ. For example, when W2 + W3 = 2H, θ becomes 45 degrees. It is possible to reduce the time by increasing the value of H or decreasing the value of W2 + W3, but it is preferable to determine the value of H and the value of W2 + W3 in consideration of the workability of the optical plate 60.

Although the backlight unit BLU is advantageous to be applied to LCD products as the distance between the light source 52 and the optical plate 60 is smaller, the opening unit 63 may be used depending on the distance between the light source and the optical plate required. You need to change the dimensions of the. In order to obtain uniform luminance on the surface of the backlight unit BLU, the smaller the width W3 of the inlet 63 is, the better. In order to obtain a small view from the surface of the backlight unit BLU, the larger the height H of the opening 63 and the width W3 of the inlet 63, the more advantageous, and the smaller the difference between W3 and W2, the better. Do. Therefore, in order to simultaneously obtain a uniform luminance and a small time, a trade-off of the values of H and W2 + W3 is required.

Although the present invention has been described in detail with respect to the use of the backlight unit (BLU), the present invention can also be applied to display panels such as advertising panels, signal panels, indicator panels, and the like. That is, the present invention can also be usefully used for the purpose of forming a uniform brightness and a suitable time on the optical plate with light spreading radially or in an arbitrary direction from a light source. Therefore, the said optical plate is applicable also for illumination. In addition, although the number and arrangement of the light sources vary depending on the application, if there is more than one light source, the present invention can obtain uniform luminance and narrow viewing time on the display panel.

In the present invention, LEDs, cold cathode fluorescent lamps (CCFL), hot cathode fluorescent lamps (HCFL), and external electrode fluorescent lamps (EEFL) are exemplified as light sources, but only general lamps such as incandescent lamps, fluorescent lamps, gas lamps, etc. Alternatively, the optical plate of the present invention may be applied to the backlight unit BLU and the display panel by using other illumination.

Meanwhile, the present invention has been described in connection with the above-mentioned preferred embodiments, but various substitutions, changes, or modifications are possible without departing from the spirit and scope of the present invention. Therefore, the claims of the present invention should not be limited to the description of the preferred embodiment and the drawings, but should include such substitutions, changes, or modifications belonging to the gist of the present invention.

1 is an exploded perspective view schematically showing the structure of a conventional direct-emitting LED type backlight unit for an LCD.

Figure 2 is an exploded perspective view schematically showing the structure of a conventional direct-emitting cold cathode fluorescent lamp type backlight unit for LCD.

Figure 3 is an exploded perspective view schematically showing the structure of the upward emission backlight unit applied to the backlight unit of the present invention.

FIG. 4 schematically shows the overall structure of the optical plate 60 shown in FIG. 3 and shows an enlarged view of a part of the structure.

5 is an exemplary view showing a path that progresses while light emitted from a light source passes through an opening of an optical plate in the backlight unit BLU of the present invention.

FIG. 6A is a diagram schematically illustrating a structure of a rectangular optical plate having a rectangular opening formed in a portion thereof.

6 (b) is a diagram showing the structure of a circular optical plate in which circular openings are formed throughout.

     *** Explanation of symbols for the main parts of the drawing ***

10,20,100: backlight unit (BLU) 11,51: printed circuit board

12,21,52: light source 13: diffuser plate

15,55: diffusion sheet 17,17a, 17b: prism sheet

19,59: protective film 22,53: reflective film

52a, 52b, 52c, 52d, 52e: optical 60, 70, 80: optical plate

61,71,81: main body 61a: lower surface

63, 73, 83: opening 63a: inlet 63b: outlet

63c: inner wall 75: transparent plate

Claims (4)

A plurality of light sources emitting light, arranged on the substrate; And An optical plate disposed on the light source for diffusing the light emitted from the light source and narrowing the view; The optical plate has a plurality of openings, and the openings have a larger inner wall than the inlet and an inclined inner wall. The backlight unit of claim 1, wherein a surface of the optical plate is one of a reflective metal and a reflective metal film, and a reflective film is disposed on a substrate of an outer portion of the light source. The backlight unit of claim 1, wherein a transparent optical plate support unit for supporting the optical plate is disposed on one of an upper surface and a lower surface of the optical plate. The backlight unit of claim 3, wherein a curved surface is formed on one of an upper surface, a lower surface, and an upper and lower surfaces of the optical plate support unit.

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