KR100845250B1 - The backlight unit - Google Patents

Abstract

The present invention relates to a backlight unit that can reduce the number of optical components and the number of processes.

According to the present invention, a backlight unit includes a light source for generating light, a lamp housing installed to surround the light source to reflect light, a light guide plate for converting light from the light source into a surface light source, and light propagation from the light guide plate. And a prism reflector formed in a prism shape having a peak and a valley while condensing a path, and a prism sheet positioned at one of the light guide plate and below the light guide plate, and the prism reflector has a triangular cross section. The prism bar has a plurality of prism bars, and the prism reflector and the prism sheet are arranged such that the prism arrangement directions are perpendicular to each other.

By such a configuration, the backlight unit according to the present invention can reduce the number of optical components and the number of processes.

Description

Backlight Unit {THE BACKLIGHT UNIT}             

1 is a cross-sectional view showing a conventional backlight unit.

FIG. 2 is a view showing a prism sheet shown in FIG. 1. FIG.

3 is a cross-sectional view illustrating a backlight unit according to a first embodiment of the present invention;

FIG. 4 is a view showing an optical path incident on a prism reflector shown in FIG. 3. FIG.

5A and 5B show light intensities different in angle between incident light and reflected light incident on a prism reflector.

6 is a view showing a prism reflector of the backlight unit according to the second embodiment of the present invention.

<Description of Symbols for Main Parts of Drawings>

1, 31: lamp 3, 33: lamp housing

5, 35: LGP 7: Reflector

9, 41: diffusion sheet 11, 13, 39: prism sheet

17, 43: lower substrate 19, 45: liquid crystal

21, 47: upper substrate 37, 51: prism reflector

The present invention relates to a backlight unit, and more particularly to a backlight unit that can reduce the number of optical components and the number of processes.

Typically, a liquid crystal display (hereinafter referred to as "LCD") is a plurality of liquid crystal cells arranged in a matrix form and a plurality of control switches for switching the video signal to be supplied to each of these liquid crystal cells The amount of light transmitted from the backlight unit is adjusted by the configured liquid crystal panel to display a desired image on the screen.

Referring to FIG. 1, a conventional backlight unit includes a lamp 1 for generating light, a lamp housing 3 installed to surround the lamp 1, and light incident from the lamp 1 as a planar light source. The light guide plate 5 to be converted, the reflector 7 positioned below the light guide plate 5 to reflect the light traveling toward the lower surface and the side surface of the light guide plate 5 toward the upper surface, and light passing through the light guide plate 5 are diffused. A diffusion sheet 9 and first and second prism sheets 11 and 13 for adjusting a traveling direction of light via the diffusion sheet 9.

The liquid crystal panel is positioned on the backlight unit. The liquid crystal panel includes an upper substrate 21 having a color filter, a common electrode, and an upper alignment layer, a lower substrate 17 formed of a thin film transistor array (TFT), a pixel electrode, and a lower alignment layer. And an liquid crystal 19 injected into an inner space between the upper substrate 21 and the lower substrate 17.

The cold cathode fluorescent lamp is mainly used as the lamp 1 of the backlight unit, and the light generated by the lamp 1 is incident on the light guide plate 5 through an incident surface existing on the side of the light guide plate 5. The lamp housing 3 has a reflecting surface on its inner surface to reflect light from the lamp 1 toward the incident surface of the light guide plate 5. The light guide plate 5 has an inclined back surface and an exit surface that is horizontal, and is made such that the incidence surface and the exit surface of the light guide plate 5 form a right angle. The rear side of the light guide plate 5 is provided so that the reflecting plate 7 faces. The light guide plate 5 allows the light incident from the lamp 1 to reach a distance far from the lamp 1. The light guide plate 5 is generally formed of an acrylic resin (PMMA) having high strength and not easily being deformed or broken and having good transmittance. The reflector 7 serves to reduce light loss by reflecting light incident to itself through the back of the light guide plate 5 toward the light guide plate 5. When light from the lamp 1 is incident on the light guide plate 5, the light is reflected at a predetermined inclination angle from the rear surface, which is an inclined surface, and proceeds uniformly toward the exit surface. At this time, the light propagated to the lower surface and the side surface of the light guide plate 5 is reflected by the reflector 7 and proceeds toward the exit surface. Light emitted through the exit surface of the light guide plate 5 is diffused to the entire area by the diffusion sheet 9. On the other hand, when the light incident on the liquid crystal panel is vertical, the light efficiency is increased. To this end, it is preferable to stack two prism sheets so that the traveling angle of the light emitted from the light guide plate 5 is perpendicular to the liquid crystal panel. As shown in FIG. 2, the first and second prism sheets 11 and 13 are arranged such that the direction of the hill and the valley are staggered at a 90 degree angle. That is, the first prism sheet 11 arranged to have an acid and a valley in the x direction allows the y component of the light emitted from the diffusion sheet 9 to be incident perpendicularly to the z direction, that is, the liquid crystal panel. Similarly, the second prism sheet 13 arranged to have an acid and a valley in the y direction causes the x component of the light emitted from the diffusion sheet 9 to be incident perpendicularly to the z direction, that is, the liquid crystal panel. Thus, by arranging the first and second prism sheets 11 and 13 by 90 degrees, the light of x and y components is vertically incident to the z direction and the liquid crystal panel. As a result, since light emitted to the outside becomes less, light loss occurs.

The light generated from the backlight unit is incident on the liquid crystal panel.

In the liquid crystal panel, the liquid crystal 19 is driven by the voltage difference between the common electrode of the upper substrate 21 and the pixel electrode of the lower substrate 17 to selectively transmit light from the backlight unit to display an image.

Recently, as large screens, light weights, and high quality of LCDs are required, researches that can achieve lightness and high brightness are being conducted. In particular, researches for light weights of backlight units are being actively conducted. However, in the conventional backlight unit, there is a problem to counter the trend of weight reduction of the backlight unit by using two prism sheets to vertically incident light passing through the light guide plate to the liquid crystal panel.

Accordingly, an object of the present invention is to provide a backlight unit that can reduce the number of optical components and the number of processes.

In order to achieve the above object, the backlight unit according to an embodiment of the present invention is a light source for generating light, a lamp housing installed to surround the light source to reflect the light, and the light from the light source as a surface light source A light guide plate to be converted, a prism reflector formed in a prism shape having a peak and a valley while condensing while changing a path of light from the light guide plate, and a prism sheet positioned at one of the light guide plate below and on the light guide plate to focus light The prism reflector includes a plurality of prism bars having a triangular cross section, and the prism reflector and the prism sheet are arranged such that the prism arrangement directions are perpendicular to each other.

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According to another embodiment of the present invention, a backlight unit includes a light source for generating light, a lamp housing installed to enclose the light source to reflect light, a light guide plate for converting light from the light source into a surface light source, and the light guide plate And a prism reflector formed in a prism shape having a peak and a valley while converging the traveling path of light from the light source, and a prism sheet positioned at either one of the light guide plate and above the light guide plate to focus light. Is composed of a plurality of square pyramid prisms having a square pyramid shape.

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

With reference to Figures 3 to 6 will be described with respect to preferred embodiments of the present invention.

Referring to FIG. 3, the backlight unit according to the first exemplary embodiment focuses light onto a prism sheet 39 and a prism reflector 37.

The backlight unit includes a lamp 31 for generating light, a lamp housing 33 installed to surround the lamp 31, a light guide plate 35 for converting light incident from the lamp 31 into a planar light source, Located at the lower portion of the light guide plate 35 to reflect the light traveling to the lower surface and the side of the light guide plate 35 toward the upper surface, and to collect the light through the prism reflector plate 37 and the light guide plate 35 A prism sheet 39 and a diffusion sheet 41 for diffusing light passing through the prism sheet 39 are provided.

Such a backlight unit is applicable to various fields, and in particular, may be used in a liquid crystal display device. In the LCD, a liquid crystal panel is positioned on the backlight unit. The liquid crystal panel includes an upper substrate 47 having a color filter, a common electrode, and an upper alignment layer, a lower substrate 43 formed of a TFT array, a pixel electrode, and a lower alignment layer, and between the upper substrate 47 and the lower substrate 43. It consists of a liquid crystal 45 injected into the inner space of the.

A cold cathode fluorescent lamp is mainly used as the lamp 31 of the backlight unit, and the light generated by the lamp 31 is incident on the light guide plate 35 through an incident surface existing on the side of the light guide plate 35. The lamp housing 33 has a reflecting surface on its inner surface to reflect light from the lamp 31 toward the incident surface of the light guide plate 35. The light guide plate 35 has an exit surface that is horizontal to the inclined back surface and is manufactured so that the incident surface and the exit surface of the light guide plate 35 form a right angle. The prism reflector 37 is provided on the rear surface of the light guide plate 35 so as to face each other. The light guide plate 35 allows the light incident from the lamp 31 to reach a distance far from the lamp 31. The light guide plate 35 is generally formed of an acrylic resin (PMMA) having high strength and not easily being deformed or broken and having good transmittance.

The prism reflector 37 serves to reduce light loss by reflecting light incident to itself through the rear surface of the light guide plate 35 toward the light guide plate 35. Here, the front surface of the prism reflector 37 has the shape of peaks and valleys of the prism like the prism sheet, and the rear surface has a flat plane. The prism shape of the prism reflector 37 also serves as a prism sheet by condensing light from the light guide plate 35. For example, the vertex angle of the prism mountain of the prism reflector 37 is about 70 degrees to about 110 degrees, and in the case of 90 degrees, the efficiency of condensing light is the best. As shown in FIG. 4, when the incident angle of the light incident on the prism reflector 37 has an angle smaller than A direction, that is, the angle of 45 degrees, the light reflection angle of the light that reflects the prism reflector 37 has an angle smaller than 45 degrees. In addition, when the incident angle of light incident on the prism reflector 37 is in the B direction, that is, when the light incident angle is larger than 45 degrees, the optical path is changed and reflected at an angle smaller than 45 degrees. When light enters the prism reflecting plate 37 in the C direction, the light is reflected twice by being reflected by the prism reflecting plate 37. When light is uniformly incident on the prism reflector 37 as shown in FIG. 5A, the intensity of incident light is constant at all angles. At this time, the reflected light is reflected between ± 45 degrees incident light as shown in Figure 5b. However, as the light incident angle of the light incident on the prism reflector 37 increases, the amount of light loss lost increases. However, since the light is focused by the prism-shaped acid of the prism reflector 37, the amount of light lost decreases.

When light from the lamp 31 is incident on the light guide plate 35, it is reflected at a predetermined inclination angle from the rear surface, which is an inclined surface, and proceeds uniformly toward the exit surface. At this time, the light propagated to the lower surface and the side surface of the light guide plate 35 is reflected by the reflecting plate 37 to travel toward the exit surface. Light emitted through the exit surface of the light guide plate 35 is collected by the prism sheet 39. If the prism shape of the prism reflector 37 is placed in the x direction, the prism shape of the prism sheet 39 is placed in the y direction. In contrast, when the prism shape of the prism reflector 37 is placed in the y direction, the prism shape of the prism sheet 39 is placed in the x direction. In other words, when the prism reflector 37 condenses the light corresponding to the component in either of the x and y directions in the z direction, the prism sheet 39 condenses the component in a direction different from that of the prism reflector 37. As a result, the x and y components of the light can be focused in the z direction. In this case, the prism sheet 39 may be located above or below the light guide plate 35. The light passing through the prism sheet 39 is uniformly diffused to the entire area by the diffusion sheet 41.

The light generated from the backlight unit is incident on the liquid crystal panel.

In the liquid crystal panel, the liquid crystal 45 is driven by the voltage difference between the common electrode of the upper substrate 47 and the pixel electrode of the lower substrate 43 to selectively transmit light from the backlight unit to display an image.

Referring to FIG. 6, the backlight unit according to the second exemplary embodiment includes a prism reflector 51 having a reflective surface having a quadrangular pyramid shape. Hereinafter, descriptions of the same elements as in the first embodiment of the present invention will be omitted.

The reflective surface of the prism reflector 51 according to the second embodiment of the present invention has a plurality of quadrangular pyramids and four oblique planes forming the pyramid are triangular. The vertex angle θ of this triangle has an angle between 70 degrees and 110 degrees, and the efficiency of condensing at 90 degrees is best. The prism reflector 51 is positioned below the light guide plate (not shown) and reflects the light incident from the light guide plate and condenses the light into the light guide plate. The prism reflector 51 has a light condensing function in all directions. Thus, light passing through the light guide plate is incident on the liquid crystal panel (not shown) via a prism sheet (not shown) located on the light guide plate.

As described above, the backlight unit according to the present invention includes a prism reflector for reflecting light and condensing light. Accordingly, the backlight unit according to the present invention can reduce the number of optical components by reducing the number of optical components by replacing the two prism sheets with one sheet as compared with the conventional one can reduce the component cost and the process cost.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the technical spirit of the present invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification but should be defined by the claims.

Claims (7)

A light source for generating light, A lamp housing installed to surround the light source to reflect light; A light guide plate for converting light from the light source into a surface light source; A prism reflecting plate formed in a prism shape having a peak and a valley while condensing while changing a traveling path of light from the light guide plate, A prism sheet positioned below one of the light guide plate and on the light guide plate to focus light; The prism reflector comprises a plurality of prism bars having a triangular cross section, and the prism reflector and the prism sheet are arranged such that the prism arrangement directions are perpendicular to each other. The method of claim 1, The prism reflector is positioned under the light guide plate. The method of claim 2, The prism sheet is positioned between the light guide plate and the prism reflector. delete A light source for generating light, A lamp housing installed to surround the light source to reflect light; A light guide plate for converting light from the light source into a surface light source; A prism reflecting plate formed in a prism shape having a peak and a valley while condensing while changing a traveling path of light from the light guide plate, A prism sheet positioned below one of the light guide plate and on the light guide plate to focus light; The prism reflector is a backlight unit, characterized in that consisting of a plurality of square pyramid prism having a square pyramid shape. delete The method according to claim 1 or 5, The vertex angle of the prism mountain of the prism reflector is 70 to 110 degrees, the backlight unit.

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