KR101239076B1 - Liquid crystal display device with light guide panel of edge light type backlight unit - Google Patents

Abstract

The present invention provides a liquid crystal display device comprising a liquid crystal panel, a light emitting lamp for supplying light to the liquid crystal panel, and a light guide plate positioned to face the light emitting lamp and guiding the light emitted from the light emitting lamp toward the liquid crystal panel. ; A light incident surface on which a prism pattern made of a plurality of prism acids is formed on one side of the main body; And a reflector attached to the top of the prism acid to reflect light from the light emitting lamp and incident on the light guide plate, wherein the light incident from the light emitting lamp to the top of the prism mountain is reflected by the reflector. The light guide plate is incident on the light guide plate at an angle greater than the angle incident on the prism acid.

LED, Light Guide Plate, Prism, Reflector

Description

Liquid crystal display device employing a light guide plate of a side emitting type backlight unit {LIQUID CRYSTAL DISPLAY DEVICE WITH LIGHT GUIDE PANEL OF EDGE LIGHT TYPE BACKLIGHT UNIT}

1 is a cross-sectional view of a conventional liquid crystal display device.

2 is a schematic perspective view of an edge type backlight unit when LED is used as a light emitting lamp;

3 is a cross-sectional view showing a state in which light from the light emitting lamp is incident on the light guide plate on which the prism acid is formed.

Figure 4 is a first embodiment according to the present invention.

5 is a plan view showing a light emitting lamp and a light guide plate according to the first embodiment;

Figure 6 is a second embodiment according to the present invention.

7 is a third embodiment according to the present invention.

8 is a fourth embodiment according to the present invention.

Description of the main parts of the drawing

121, 221, 321, 421: Light emitting lamps 124, 224, 324, 424: Light guide plate

150, 250, 350, 450: prism acid 152, 252, 352, 452: reflector

Recently, the importance of the display device for displaying various information is increasing with the rapid development of the information and communication field, and one of the existing display devices (Cathode Ray Tube) has a certain limit to meet the latest trend of light weight and thinning. Could not. As a flat panel display, a liquid crystal display (LCD), a plasma display panel (PDP), and an electroluminescence display (ELD) have been developed to meet expectations, and research and development are actively conducted. It is becoming.

Among the display devices, the liquid crystal display device is a display device having advantages such as light weight, thinness, and low power, and is widely used not only for display devices such as notebook computers, but also for desktop computers and large TVs. have.

In general, a liquid crystal display device includes a driving unit for driving the liquid crystal panel and a backlight unit for supplying light to the liquid crystal panel, in addition to the liquid crystal display panel. . This is because the liquid crystal display does not emit light and thus requires a backlight unit, which is a separate device for irradiating light to the liquid crystal panel.

Hereinafter, a liquid crystal display device including a conventional backlight unit will be described with reference to the accompanying drawings.

1 is a schematic exploded perspective view showing a general liquid crystal display device.

As shown in FIG. 1, the liquid crystal display device 1 includes a liquid crystal panel 10 and a backlight unit 20. The backlight unit 20 is positioned below the liquid crystal panel 10, and integrated circuits electrically connected to each other by TCP (Tape Carrier Package 11) are mounted on the liquid crystal panel 10. The liquid crystal panel 10 includes an upper substrate and a lower substrate. The lower substrate is a thin film transistor substrate. A thin film transistor, which is a switching element, is formed in a plurality of pixels to apply an image signal to a pixel electrode formed in the pixel from the outside. In addition, a liquid crystal layer is formed between the upper substrate and the lower substrate to realize a desired image by adjusting the transmitted light according to the input image signal. Since the liquid crystal panel does not emit light by itself, light is supplied from the backlight unit. When light emitted from the backlight unit passes through the liquid crystal layer, the light transmittance is determined by the arrangement state of the liquid crystals to display an image.

The backlight unit is a direct method of directly dimming the front surface of the panel by arranging a light source on one side of the panel, and an edge method of reflecting / diffusing light rays on a light guide plate and a reflective sheet by disposing a light source on one side or a plurality of side surfaces of the panel. Divided. The direct method is usually used for large liquid crystal display devices, and the edge method is used for small liquid crystal display devices such as notebook computers.

The backlight unit 20 shown in FIG. 1 is an edge type backlight unit in which a light emitting lamp is installed at a side thereof. The backlight unit includes a light emitting lamp 21, a light guide plate 24, a reflecting plate 22, and an optical sheet 23, and the optical sheet 23 includes a diffusion sheet, a prism sheet, and a protective sheet. The light emitted from the light emitting lamp 21 reaches the liquid crystal panel 10 through the light guide plate 24 provided on the bottom surface of the liquid crystal panel 10. In this case, the light guide plate 24 emits light emitted from the light emitting lamp 21. It serves as a guide to (10). In this case, the light efficiency may be increased by diffusing and condensing light through the optical sheet 23 between the light guide plate 24 and the liquid crystal panel 10. The reflector 22 serves to reflect light such that the light emitted from the light emitting lamp 21 travels in the direction of the liquid crystal panel 10.

The backlight unit used as the light source of the liquid crystal display device is mainly used as a light emitting lamp (CFL), a light emitting diode (LED), and the like. However, LEDs (Light Emitting Diodes) are widely used in LCDs including mobile phones and PDFs, and are increasingly being used as light sources for large liquid crystal panels. This is due to the fact that the LED consumes less power, has a longer lifespan, and does not require an additional device such as an inverter, thereby making it thinner and having high color reproducibility.

However, when the liquid crystal display device is manufactured using the LED as the light emitting lamp, there is a problem in that bright spots and / or dark portions occur due to the characteristics of the LED. 2 is a schematic perspective view of an edge type backlight unit when LED is used as a light emitting lamp. When the light emitted from the LED 31 in the backlight unit enters the light guide plate 34, the light is incident due to the refractive index of the light guide plate 34, and as a result, the light is emitted in a predetermined angle range. There is a problem that the image is stained, such as the bright spot 42 appearing outwardly and the darker darkening part 40 appearing in order in comparison with other areas between the area and the non-emitted area.

In order to solve this problem, in the related art, a backlight unit having a light guide plate positioned to face the light emitting lamp and having a light incident surface provided with a prism pattern has been developed. In the light guide plate provided with the prism pattern in the direction of the light emitting lamp, light is incident through the prism surface and the light is refracted to change the incident angle of the light.

However, even the light guide plate on which the prism pattern was formed could not eliminate the phenomenon of bright spots and / or dark portions. That is, although the light path is refracted by the difference in refractive index between air and the light guide plate by the prism pattern, the optical path is changed, but the effect is not large. Therefore, there was still a problem that bright spots and / or dark areas appear.

The present invention is to solve the above problems, by varying the angle of the light incident to the light guide plate in various ways to reduce the bright spots and dark areas generated in the liquid crystal panel, to increase the brightness and uniformity of the light supplied from the light guide plate to the liquid crystal panel An object of the present invention is to provide an improved light guide plate and a liquid crystal display device including the same.

The present invention provides a liquid crystal display device comprising a liquid crystal panel, a light emitting lamp for supplying light to the liquid crystal panel, and a light guide plate positioned to face the light emitting lamp and guiding the light emitted from the light emitting lamp toward the liquid crystal panel. ; A light incident surface on which a prism pattern made of a plurality of prism acids is formed on one side of the main body; And a reflector attached to the top of the prism acid to reflect light from the light emitting lamp and incident on the light guide plate, wherein the light incident from the light emitting lamp to the top of the prism mountain is reflected by the reflector. The light guide plate is incident on the light guide plate at an angle greater than the angle incident on the prism acid.

The light emitting lamp includes an LED, and the reflector is formed on a part of the prism mountain of the prism pattern.

The prism pattern includes a symmetrical shape with respect to an axis extending from the light incident surface in a traveling direction of light, wherein the prism pattern includes a triangular horizontal cross section.

The edge type backlight unit used in the liquid crystal display device according to the present invention is to solve the bright spot and / or the dark portion generated in the conventional light guide plate even when the prism pattern is formed. do.

In the conventional edge type backlight unit, the light emitting lamp exists on one side of the light guide plate, and the light emitted from the light emitting lamp passes through the light guide plate to the liquid crystal panel. In this case, the light guide plate serves to guide the light. When the light emitting lamp is a point light source such as an LED, the light is radiated within a predetermined angle so that a bright spot and / or a dark part is generated. In this case, in order to reduce the bright spot and / or the dark portion, one end surface of the light guide plate, that is, the surface facing the light emitting lamp is formed to form a prism acid to bend the light in various directions.

3 is a cross-sectional view of a light incident from the light emitting lamp 21 incident on the light guide plate 24 on which the prism acid 50 is formed. As shown in FIG. 2, the refraction occurs when light is incident due to a difference in refractive index between the light guide plate 24 on which the prism acid 50 is formed and the air. At this time, the light emitted from the light emitting lamp 21 is incident through the light incident surface of the light guide plate 24 on which the prism acid 50 is formed, and the portion where the prism acid 50 is formed has a different angle than the light guide plate without the prism acid. Make it refracted Therefore, since the angle of incidence due to the difference in refractive index is slightly changed, the light path is changed, and thus the light spreadability is increased and the degree of bright spot and dark part is reduced than the linear light guide plate without prism acid. However, since the light incident on the light guide plate is refracted by the incident light at a predetermined angle, the light traveling in the light guide plate is less than a predetermined angle. In addition, since the light incident more than the critical angle is total reflection occurs, the light may not proceed to a specific part even when there is a prism, so that the bright spot or the dark part still exists even if the degree is reduced.

Therefore, the present invention attempts to solve the above problems by making the incident angle to the light guide plate larger, thereby reducing the bright spot and dark portion as much as possible and increasing the uniformity of light. The light guide plate according to the present invention is characterized in that a prism acid is formed on a surface on which light is incident and a reflector capable of totally reflecting light is mounted on a part of the prism acid. The light guide plate is refracted when the light is incident at a certain angle, and has a property of total reflection when entering the light at a specific angle or more (critical angle), so that light emitted from the light emitting lamp is refracted by entering the light guide plate as it is unless it is a specific critical angle. do. Therefore, point light sources such as LEDs have a limited radiation angle in the direction of the light guide plate, and the angle at which the incident light is refracted is also determined by the refractive index. Therefore, a dark part may not be spread in a specific direction, and the light rays may overlap. We have already seen that.

In this case, when the reflector is placed on the prism mountain, the reflector totally reflects the light, so that the direction of the light can be changed to an angle different from the angle incident on the existing prism mountain. In other words, the light reflected through the reflector is incident at an angle different from that of the conventional prism, and the square of the light is not refracted to reduce the bright spot or the dark part and the uniformity of the light transmitted through the liquid crystal panel. This will be better. That is, a uniform luminance distribution can be obtained on the light exiting surface exiting from the inside of the light guide plate, and the bright spots or dark portions appearing on the liquid crystal panel are reduced.

In this case, the prism pattern includes a shape formed to be symmetrical about an axis extending from the light incident surface in a traveling direction of light. In order to keep the light incident on the light guide plate uniformly, the prism pattern is preferably formed in a repetitive pattern. In particular, the prism pattern should be formed to be symmetrical to the axis on which light is incident so that the uniformity of the light on both sides is the same. Therefore, when forming the prism pattern according to the present invention is characterized in that the prism pattern is formed symmetrically about a predetermined axis.

Hereinafter, an embodiment will be described with reference to the drawings.

4 is a cross-sectional view showing a first embodiment according to the present invention. In the present invention, when the prism acid 150 is disposed on the light incident surface of the light guide plate 124 facing the light emitting lamp 121, the light path is shown. In practice, however, a plurality of prism acids are often arranged, but only one prism acid is formed in the drawings for easy understanding. In the present embodiment, the reflector 152 is attached to the top of the prism 150 with a predetermined size. In the case where the reflector 152 is attached, when the light is incident on the top of the prism 150 as shown, the light is reflected by the reflector 152 and the reflected light is incident on the light guide plate 124 at a large angle. The dark part can be compensated. In addition, when the bright spot and the dark portion alternately appear, it also serves to weaken the bright spot by reducing the amount of light entering the light guide plate 124 vertically.

5 is a plan view showing a light emitting lamp and a light guide plate according to the first embodiment. As shown, the light emitting lamp 121 is provided on one side of the light guide plate 124, and the light emitted from the light emitting lamp is incident on the prism 150 formed on the light incident surface of the light guide plate 124. The light is reflected by 152 to be incident on the light guide plate at a wide range of angles.

6 is a sectional view showing a second embodiment according to the present invention. In the present invention, the light guide plate on which the prism acid is formed is used as it is, but the difference from the first embodiment is that the reflector 252 is formed on one surface of the prism mountain, that is, on the surface corresponding to the hypotenuse of the prism mountain, not on the top of the prism mountain 250. It is a point. In this case, in order to obtain uniform light, the reflector 252 may be simultaneously formed on a surface symmetrical with respect to the top of the prism mountain 250. In this embodiment, the reflector 252 is formed at a portion that enters a certain area at an angle, thereby reducing the bright spot or the dark portion. In this case, the place where the reflector is formed and the size of the reflector may vary depending on various factors such as the size or shape of the prism acid and the distance to the light emitting lamp, and may be formed where the bright spot and / or the darkest part is reduced.

A third embodiment according to the present invention is shown in FIG. As shown in the third exemplary embodiment, the reflector 352 is formed only on one surface of the prism mountain 350, not symmetrically, for each prism mountain. In this case, for uniform reflection and incidence of light, the reflector 352 of the prism mountain 350 is preferably formed on the symmetrical surface of the prism acid with the concave portion of the prism mountain 350 being a symmetry line. .

In the fourth embodiment of FIG. 8, the pattern itself of the prism acid 450 is formed differently. The shape of the prism acid to which the reflector 452 is attached may be various shapes such as an arc shape or other semicircle, rather than a triangular cross section, which is a general shape. Since the direction of refraction of the light varies depending on the curvature, the uniformity of the light may be increased, and thus the cross-section of the prism acid is possible. In this case, the reflector may be formed on a part of the prism mountain and may include a reflector having a total reflection even in the case of a flat hypotenuse or a curved surface.

It is preferable that the reflector according to the present invention is a reflector capable of total reflection, but a reflector of a form that can be partially reflected may be used even if it is not total reflection. That is, if a part of the light can be reflected at a wide angle such that no bright spot or dark part is formed, a reflector functioning as part of refraction, transmission, and part reflection may also be applied. In this case, the degree of reflectance may be adjusted according to the degree of dark spots or bright lines.

As described above, the prism acid of the light guide plate may be formed in various forms. The prism acid does not mean only a prism shape, but is formed on one surface of the light guide plate and is formed in a shape having a predetermined height by inserting a pattern so that light may be refracted in various directions. Therefore, it is formed in the shape of the comb long and can be formed in the form of a cross section, in particular in the shape of an isosceles triangle, even if it is not formed in the shape of a comb long it may be possible to form a triangular pyramid. In addition, as shown in the eighth embodiment, it may be assumed that a part is curved.

It is obvious that various changes and modifications can be made by those skilled in the art through the above description, and the scope of the present invention is not limited only to the above-listed embodiments. In particular, although the shape of the prism acid has been described with reference to some embodiments, other types of prism acid may be possible, and the reflector may be formed on other types of prism acid. Therefore, the scope of the present invention should be defined by the scope of the claims rather than the details of the description.

According to the present invention, a path of light incident on the light guide plate can be variously changed by forming a prism acid on a light incident part of the light guide plate and forming a reflector capable of reflecting light on the prism acid. Accordingly, since the light incident on the light guide plate has various angles, a uniform luminance distribution can be obtained at the light exit surface exiting from the inside of the light guide plate, and the bright spots or dark portions appearing on the liquid crystal panel are reduced. As a result, since the defect of the liquid crystal display element is reduced and the image quality is increased, a reliable high quality liquid crystal display element can be provided.

Claims (7)

Liquid Crystal Panel, Light emitting lamp for supplying light to the liquid crystal panel, Located to face the light emitting lamp and comprises a light guide plate for guiding the light from the light emitting lamp to the liquid crystal panel, the light guide plate, A light guide plate body; A light incident surface on which a prism pattern made of a plurality of prism acids is formed on one side of the main body; And And a reflector attached to the top of the prism mountain to reflect light from the light emitting lamp and incident on the light guide plate, and the light incident from the light emitting lamp to the top of the prism mountain is reflected by the reflector, thereby causing the prism. The liquid crystal display device, characterized in that incident on the light guide plate at an angle greater than the angle incident on the acid. The method of claim 1, The light emitting lamp is a liquid crystal display device, characterized in that the LED. delete The method of claim 1, And the reflector reflects all of the light. The method of claim 1, The reflector is a portion of the liquid crystal display element, characterized in that for transmitting light and part. The method of claim 1, And a prism acid of the prism pattern formed in a shape symmetrical about an axis extending from the light incident surface in a traveling direction of light. The method of claim 1, The prism acid of the prism pattern, the horizontal cross-section is a liquid crystal display device, characterized in that the triangle.

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