KR102135611B1 - Direct type Backlight Unit and Liquid crystal display device having direct type backlight unit - Google Patents

Abstract

The direct type backlight unit according to the present invention includes a light source that emits light, a light guide plate having a light incident surface to which light from the light source is incident, and a light refracting surface to which the incident light is refracted, and surrounding the light source while underneath the light guide plate. It characterized in that it comprises an optical structure for injecting light to the light incident surface, by reducing the optical gap (optical gap) it is possible to slim the liquid crystal display device including a direct type backlight unit and a direct type backlight unit.

Description

Direct type backlight unit and liquid crystal display device having direct type backlight unit

The present invention relates to a liquid crystal display device, and more particularly, to a direct backlight unit having improved light diffusion performance while being slim and a liquid crystal display device including the same.

With the development of various portable electronic devices such as mobile communication terminals and notebook computers, the demand for a flat panel display apparatus that can be applied thereto is gradually increasing.

Among flat panel display devices, the liquid crystal display device has advantages of development of mass production technology, ease of driving means, realization of high image quality, low power consumption, and realization of a large screen. Accordingly, the liquid crystal display device may include a monitor such as an industrial terminal, a laptop computer, and a game machine; Portable terminals such as mobile phones, MP3s, PDAs, PMPs, PSPs, portable game machines, and DMB receivers; And household appliances such as refrigerators, microwave ovens, washing machines, and the like.

Since the liquid crystal display device is not a display device that emits light by itself, a backlight unit including a separate light source that provides light to visually express an image is provided on the rear surface of the liquid crystal display panel. That is, the light emitted from the backlight unit disposed under the liquid crystal display panel is incident on the liquid crystal display panel to adjust the amount of light transmitted according to the arrangement of the liquid crystal to display an image.

The backlight unit has two types, a direct type and an edge type, depending on the position of the light source.

The edge type is a light source disposed on the side of a flat plate, and light emitted from the light source is irradiated onto the entire surface of the liquid crystal display panel using a light guide plate. On the other hand, the direct type is a method in which a number of light sources are arranged on the rear surface of a liquid crystal display panel to directly irradiate light directly under the liquid crystal display panel.

In the state of active research on a large-area liquid crystal display device according to the needs of consumers, a direct type is more suitable for a large-area liquid crystal display device than an edge type.

Hereinafter, a direct type liquid crystal display device according to the prior art using a light emitting diode as a backlight will be described with reference to the drawings.

1 is a schematic cross-sectional view showing a direct type liquid crystal display device according to the prior art in which a light emitting diode is applied as a backlight.

Referring to FIG. 1, a direct-type liquid crystal display device according to the prior art, in which a light emitting diode is applied as a backlight, includes an optical sheet 60, a diffusion plate 50, and a diffraction lens (sequentially disposed under the liquid crystal display panel 70). 40), a light emitting diode 30, a reflector 20, and a cover bottom 10.

The liquid crystal display device includes a liquid crystal display panel 70 and a backlight unit behind it.

Here, although not shown in the drawing, the liquid crystal display panel 80 includes a thin film transistor array substrate and a color filter substrate bonded to each other by maintaining a uniform cell gap, and a liquid crystal layer formed by being injected between the two substrates. do.

The backlight unit includes a reflector 20 and a plurality of light emitting diodes 30 arranged side by side on the upper surface thereof, and a diffusion plate 50 and an optical sheet 60 are provided on the light emitting diode 30. Located.

At this time, light emitted from the plurality of light emitting diodes 30 enters the diffusion plate 50 through the diffraction lens 40.

The diffractive lens 40 is used to widen the cover area of the light emitted from the light emitting diode 30.

On the other hand, in recent years, the use area of a liquid crystal display device, as well as a portable computer, a desktop computer monitor, a wall-mounted television, etc. is gradually widening, and research on thin liquid crystal display devices having a large display area is actively being conducted.

Accordingly, attempts have been made to provide a thin liquid crystal display device by reducing the optical gap of the backlight unit, that is, the gap (O/G) between the reflector 20 and the diffuser plate 50.

However, when the distance (O/G) between the reflector 20 and the diffuser plate 50 is small, the light is emitted due to the feature that light from the light emitting diode 30 is concentrated at the center of the top of the light emitting diode 30. The center portion corresponding to the diode 30 generates a mura phenomenon of a light emitting diode having a bright but dark periphery, which causes a decrease in display quality of the liquid crystal display due to luminance reduction and luminance irregularity.

In addition, by increasing the number of light-emitting diodes 30, the mura phenomenon of the light-emitting diodes can be prevented from being seen, but this causes a cost increase problem and a heat dissipation problem due to the increase in the number of light-emitting diodes 30, and further It is becoming a factor that increases power consumption.

The present invention is designed to solve the above-mentioned conventional problems, and the present invention includes a direct type backlight unit and a direct type backlight unit capable of reducing the number of light emitting diodes and simultaneously reducing the optical gap. The purpose is to provide a liquid crystal display device.

In order to achieve the above object, the present invention, a light guide plate having a light source that emits light, a light incident surface to which light from the light source is incident, and a light refracting surface to which the incident light is refracted, and surrounding the light source while underneath the light guide plate It provides a direct-type backlight unit including an optical structure in which light is incident on the light incident surface.

The optical structure is in the form of an inverted truncated cone, and may be formed by having a first hole surrounding the light source at the center of the lower surface and a second hole at the center of the upper surface.

The first hole may have a cylindrical shape, and the second hole may have a conical shape.

The optical structure may be formed such that light incident on the light guide plate is totally reflected on the light refracting surface.

The optical structure may have a larger refractive index than the light guide plate.

The optical structure may be made of any one of acrylic, polymethyl methacrylate, polycarbonate, and polystyrene.

The optical structure may be formed by being attached to the light guide plate.

The present invention also includes a liquid crystal display panel for displaying an image using the light transmittance of the liquid crystal, and a direct type backlight unit according to any one of claims 1 to 7 for irradiating light to the liquid crystal display panel. It provides a liquid crystal display device characterized in that the configuration.

A cover bottom for receiving the direct type backlight unit, a top cover for covering the top and side edges of the liquid crystal display panel, and a support main seated on the cover bottom and surrounding the edges of the liquid crystal display panel and the direct type backlight unit are further provided. It can be configured to include.

According to the present invention as described above has the following effects.

The present invention forms an optical structure that allows light to enter the light guide plate so that light can be totally reflected from the light guide plate while enclosing the light source that emits light, so that light can be evenly distributed on the front of the liquid crystal display panel with a small number of light sources. The number of light sources can be reduced, and accordingly, the manufacturing cost and power consumption of the light sources can be reduced.

According to the present invention, the optical structure and the light guide plate are formed by being integrally attached, thereby reducing the optical gap, thereby making the liquid crystal display including the direct type backlight unit and the direct type backlight unit slim.

In addition, the present invention, even when the optical gap (optical gap) is reduced, because the light from the light source is distributed evenly distributed over the front of the liquid crystal display panel by an optical structure integrally attached to the light guide plate, a problem that the mura phenomenon occurs Can improve.

1 is a schematic cross-sectional view showing a direct type liquid crystal display device according to the prior art in which a light emitting diode is applied as a backlight.
2 is a schematic cross-sectional view of a direct type backlight unit according to an embodiment of the present invention.
3 is a three-dimensional view of the optical structure of the direct type backlight unit according to an embodiment of the present invention.
4 is a schematic cross-sectional view of a liquid crystal display device according to an exemplary embodiment of the present invention.

The terms "above" and "below" as described herein are meant to include the case where a certain configuration is formed immediately above or below another configuration, as well as when a third configuration is interposed between these configurations. do.

The term "connected" as used herein means to include not only a case in which one component is directly connected to another component but also a component indirectly connected to another component through a third component.

Modifiers such as "first" and "second" described in this specification are not meant to indicate the order of the corresponding components, but to distinguish the corresponding components from each other.

The terms used herein are only used to describe specific embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise.

As used herein, the term'include' is intended to designate the presence of a feature, number, step, action, component, part, or combination thereof described, one or more other features, numbers, steps, It should be understood that it does not preclude the existence or addition possibility of the operation, components, parts or combinations thereof.

Hereinafter, preferred embodiments of the present invention designed to solve the above problems will be described in detail with reference to the accompanying drawings.

2 is a schematic cross-sectional view of a direct type backlight unit according to an embodiment of the present invention, and FIG. 3 is a stereoscopic view of an optical structure of the direct type backlight unit according to an embodiment of the present invention.

As can be seen in Figure 2, the backlight unit according to an embodiment of the present invention comprises a printed circuit board 110, a light source 120, an optical structure 130, and a light guide plate 140.

The light source 120 is disposed on the printed circuit board 110.

Although not shown in the figure, the printed circuit board 110 is made of metal and is provided with a driving circuit (not shown) for driving the light source 120.

In addition, the printed circuit board 110 may be a metal core printed circuit board having a heat dissipation function so as to receive heat from the light source 120 and discharge it to the outside.

The light source 120 is electrically connected to the printed circuit board 110 and emits light according to driving power supplied from a driving circuit (not shown) of the printed circuit board 110 and has light to have a predetermined luminance. Emits.

In addition, the light source 120 may be a colored LED or a white LED that emits at least one color among colors such as red, blue, and green. In addition, the colored LED may include at least one of a red LED, a blue LED, and a green LED, and the arrangement and emission light of the light emitting diode 120 can be variously changed and applied.

In this case, as the light source 120, not only an LED (Light Emitting Diode), but also an EL (Electro Luminescence), CCFL (Cold Cathode Fluorescent Lamp), HCFL (Hot Cathode Fluorescent Lamp), and an external electrode emitting lamp (EEFL) can be used. Can. In the above, CCFL, HCFL and EEFL are linear light sources, and LED is a point light source.

2 and 3, the optical structure 130 is formed to surround the light source 120 on the printed circuit board 110.

The optical structure 130 causes light from the light source 120 to enter the light incident surface 141 of the light guide plate 140.

In particular, the optical structure 130 is incident on the light incident surface 141 so that light incident on the light guide plate 140 is totally reflected on the light refracting surface 142.

To this end, the optical structure 130 may be formed in the form of an inverted cone.

More specifically, the optical structure 130 is provided with a first hole H1 in the form of a cylinder to surround the light source 120 in the center of the lower surface. In addition, a second hole H2 in the form of a cone is provided at the center of the upper surface.

The light emitted from the light source 120 passes through the first hole H1 and enters the light incident surface 141 of the light guide plate 140 through the optical structure 130 or the first hole H1. After passing through the optical structure 130, the second hole (H2) is refracted to be incident on the light incident surface 141 of the light guide plate 140.

At this time, the light incident on the light incident surface 141 of the light guide plate 140 is totally reflected on the light refracting surface 142.

Here, the optical structure 130 is in the form of an inverted cone, the first hole (H1) has a cylindrical shape, and the second hole (H2) is shown in a conical shape, but the optical structure according to the present invention (130), The first hole H1 and the second hole H2 may include various forms for total reflection of the light incident on the light guide plate 140 at the light refracting surface 142.

To this end, the refraction and reflection of light according to the refractive index for total reflection to occur in the light refracting surface 142 may be expressed as [Equation] below, which is Snell's law.

[Mathematics]

Here, n1 is the refractive index of the optical structure 130 and n2 is the refractive index of the light guide plate 140. In addition, sinθ ₁ is the incident angle, and sinθ ₂ is the refractive angle.

In the above equation, the light incident from a medium having a high refractive index to a medium having a low refractive index has a larger refractive angle than the incident angle. At this time, when the light proceeds from a medium having a large refractive index to a medium having a small refractive index, if the incident angle is greater than the critical angle, total reflection occurs at the interface. Here, the critical angle means an incident angle when total reflection occurs.

That is, so that the total reflection occurs in the light refracting surface 142 (A), the optical structure 130 must have a larger refractive index than the light guide plate 140.

In addition, the optical structure 130 is made of a transparent material so that the light is transmitted while changing the path of light supplied from the light source 120. For example, the optical structure 130 includes any one of acrylic (Acryl), poly methyl methacrylate (PMMA: Poly Methyl Meta Acrylate), polycarbonate (PC: PolyCarbonate), and polystyrene (PS: PolyStyrene) Can be achieved.

The light guide plate 140 is formed by being attached to the optical structure 130.

The light guide plate 140 may uniformly disperse the light totally reflected from the light refracting surface 142 and uniformly transmit it.

To this end, the light guide plate 140 may be made of a transparent material so that the light is transmitted while changing the path of the light supplied from the light source 120. For example, it may be made of any one of acrylic (Acryl), polymethyl methacrylate (PMMA: Poly Methyl Meta Acrylate), polycarbonate (PC: PolyCarbonate), and polystyrene (PS: PolyStyrene). However, even in this case, the light guide plate 140 should be made of a material having a smaller refractive index than the optical structure 130.

The light guide plate 140 is attached to the optical structure 130 and is integrally formed.

Therefore, the optical structure 130 and the light guide plate 140 are formed by being integrally attached, thereby reducing an optical gap between the printed circuit board 110 and the light guide plate 140. Therefore, the direct-type backlight unit according to the present invention can be made slim.

In addition, since the optical structure 130 is attached to the light guide plate 140 to support the light guide plate 140, there is no need to form a separate support structure.

In the following, repeated descriptions of repeated parts in materials and structures of the respective structures will be omitted.

4 is a schematic cross-sectional view of a liquid crystal display device according to an exemplary embodiment of the present invention, and relates to a liquid crystal display device to which the backlight unit according to FIG. 2 is applied.

As can be seen from FIG. 4, the liquid crystal display device according to the exemplary embodiment of the present invention includes the direct-type backlight unit according to FIG. 2 described above, the liquid crystal display panel 200 on the direct-type backlight unit, and the direct-type backlight. It comprises a top cover 400 for mounting the unit and the liquid crystal display panel 200, a support main 300, and a cover bottom 500.

The liquid crystal display panel 200 is a part that plays a key role in image display, and includes an array substrate 210 and a color filter substrate 220 bonded to each other with a liquid crystal layer interposed therebetween.

At this time, under the premise of an active matrix method, although not clearly shown in the drawings, a pixel is defined by intersecting a plurality of gate lines and data lines on the inner surface of the array substrate 210, and a thin film transistor at each intersection point. (Thin Film Transistor: TFT) is provided and is connected one-to-one with the transparent pixel electrode formed in each ash.

In addition, as an example corresponding to each pixel on the inner surface of the color filter substrate 220, color filters of red (R), green (G), and blue (B) colors, and each of them are surrounded by gate lines and data. A black matrix is provided to cover non-display elements such as lines and thin film transistors. In addition, transparent common electrodes are provided to cover them.

A direct-type backlight unit that supplies light to the liquid crystal display panel 200 is provided.

The direct type backlight unit includes a printed circuit board 110, a light source 120, an optical structure 130, a light guide plate 140, and an optical sheet 150.

Light from the light source 120 is totally reflected by the light guide plate 140 through the optical structure 130 and is evenly distributed to the optical sheet 140 and emitted.

That is, in the liquid crystal display device according to the present invention, light from the light source 120 is emitted through the optical structure 130 integrally attached to the light guide plate 140, so that the liquid crystal display is performed even with a small light source 120. It is evenly distributed on the front surface of the panel 200 to allow light to enter, thereby reducing the number of the light sources 120, thereby reducing the manufacturing cost of the light source 120 and the power consumption generated by the light source 120 can do.

In addition, the optical structure 130 surrounding the light source 120 is formed by being integrally attached to the light guide plate 140, thereby forming an optical gap between the printed circuit board 110 and the light guide plate 140. It is possible to reduce the size of the liquid crystal display device.

In addition, the liquid crystal display device according to the present invention, even if the optical gap (optical gap) is reduced, the liquid crystal display panel by the optical structure 130, the light from the light source 120 is integrally attached to the light guide plate 140 (200) Since it is distributed evenly over the entire surface and released, a mura phenomenon does not occur.

The optical sheet 150 is disposed on the light guide plate 140 to improve luminance characteristics of light incident from the light guide plate 140 and emit it to the outside. To this end, although not shown, it may be configured to include a lower diffusion sheet, a lower prism sheet, an upper prism sheet, and an upper diffusion sheet.

The liquid crystal display panel 200 and the backlight unit are modularized through the top cover 400, the support main 300, and the cover bottom 500. The top cover 400 is a top surface and a side surface of the liquid crystal display panel 200. It is configured to display an image implemented in the liquid crystal display panel 200 by opening a front surface of the top cover 400 in a rectangular frame shape in which a cross section is bent in a “a” shape to cover an edge.

In addition, the cover bottom 500 forms a predetermined space so that the backlight unit can be accommodated.

The support main 300 having a rectangular frame shape that is seated on the cover bottom 500 and surrounds the edges of the liquid crystal display panel 200 and the backlight unit is combined with the top cover 140 and the cover bottom 500.

Meanwhile, the top cover 400 may be referred to as a case top or a top case, the support main 300 may be referred to as a guide panel or main support, or a mold frame, and the cover bottom 500 may also be referred to as a bottom cover.

Those skilled in the art to which the present invention pertains will appreciate that the above-described present invention can be implemented in other specific forms without changing its technical spirit or essential features.

For example, it has been described that the printed circuit board 110 is essentially included in all the above-described embodiments, but in the modified embodiment, the printed circuit board 110 may be omitted. In this case, the light source 120 and the optical structure 130 are directly formed on the cover bottom 500.

Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive. The scope of the present invention is indicated by the following claims rather than the above detailed description, and it should be interpreted that all changes or modifications derived from the meaning and scope of the claims and equivalent concepts are included in the scope of the present invention. do.

110: printed circuit board 120: light source
130: optical structure 140: light guide plate
141: light incident surface 142: light refractive surface
H1: Hole 1 H2: Hole 2
O/G: Optical gap

Claims (9)

A light source that emits light;
A light guide plate having a light incident surface to which light from the light source is incident and a light refractive surface to which the incident light is refracted; And
And an optical structure surrounding the light source and allowing light to enter the light incident surface under the light guide plate,
The upper surface of the optical structure is in contact with the lower surface of the light guide plate,
The lower surface of the optical structure is in contact with the upper surface of the printed circuit board,
The height of the optical structure is the direct backlight unit equal to the distance between the light guide plate and the printed circuit board. According to claim 1,
The optical structure is in the form of an inverted cone,
A first hole surrounding the light source in the lower center portion; And
A direct type backlight unit having a second hole in the upper center portion. According to claim 2,
The first hole has a cylindrical shape,
The second hole is a direct-type backlight unit having a conical shape. According to claim 1,
The optical structure is a direct type backlight unit formed so that light incident on the light guide plate is totally reflected on the light refracting surface. According to claim 1,
The optical structure is a direct type backlight unit having a larger refractive index than the light guide plate. According to claim 1,
The optical structure is a direct backlight unit comprising any one of acrylic, polymethyl methacrylate, polycarbonate, and polystyrene. According to claim 1,
The optical structure is a direct-type backlight unit formed by being attached to the light guide plate. A liquid crystal display panel that displays an image using the light transmittance of the liquid crystal; And
A liquid crystal display device comprising the direct-type backlight unit according to any one of claims 1 to 7 for irradiating light to the liquid crystal display panel. The method of claim 8,
A cover bottom for storing the direct type backlight unit;
A top cover covering the top and side edges of the liquid crystal display panel; And
A liquid crystal display device mounted on the cover bottom and further comprising a support main surrounding the edges of the liquid crystal display panel and the direct-type backlight unit.

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