KR20060055156A - Direct type back light - Google Patents

Abstract

The present invention relates to a direct type backlight having a lighter weight than a light guide plate type backlight and having a uniform light brightness than a conventional direct type backlight, the lower reflector having at least one concave portion on a surface opposing the display surface of the liquid crystal panel; At least one light emitting lamp disposed corresponding to the recess of the lower reflector, at least one upper reflector disposed above the light emitting lamp corresponding to the recess of the lower reflector, and between the upper reflector and the liquid crystal panel. It is characterized by including the optical sheet.

Direct type, backlight, reflector

Description

Direct Type Back Light

1 is a perspective view of a light guide plate backlight according to the prior art.

2A and 2B are cross-sectional views of a light guide plate type backlight according to the prior art.

3 is a perspective view of a direct backlight according to the prior art;

4 is a cross-sectional view of a direct backlight according to the prior art.

5 is a perspective view of a direct type backlight according to the present invention;

6 is a cross-sectional view of the direct type backlight on the line II ′ of FIG. 5.

7 is a cross-sectional view of a direct type backlight showing an optical path according to the present invention.

* Explanation of symbols on the main parts of the drawings

511: light emitting lamp 514: lower reflection plate

515: diffuser plate 516: prism sheet

550: upper reflector

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight that is a component of a liquid crystal display device, and more particularly, to a direct backlight having a lighter weight than a light guide plate backlight and having a thickness thinner than that of a conventional direct backlight. .

Recently, researches on flat panel displays have been actively conducted, and among them, liquid crystal display devices (LCDs), field emission display devices (FEDs), electro-luminescence display devices (ELDs), and PDPs (PDPs) Plasma Display Panels).

Among them, liquid crystal displays have a large contrast ratio, are suitable for gray scale display or moving image display, and have low power consumption. Therefore, the area of LCDs has been expanded to notebook PCs, desktop monitors, and LCD TVs.

However, since the liquid crystal display itself is non-luminescent, a separate external light source for irradiating light is required. In particular, in the case of a transmissive liquid crystal display device, a separate dimming device that emits light and guides the back of the LCD panel is necessary.

The backlight may vary from a light guide plate type to a direct type according to a method of projecting light.

Among them, the light guide plate type is a system in which tubular line light sources such as light emitting lamps (hot cathode and cold cathode) are provided on the side of the liquid crystal panel, and the light from the light emitting lamp is projected onto the entire liquid crystal panel screen using a transparent light guide plate. The direct type is a method in which the light emitted from the light emitting lamp selectively mounted on the lower part of the liquid crystal panel is diffused by a certain sheet installed between the light emitting lamp and the liquid crystal panel and distributed throughout the liquid crystal panel screen.

Hereinafter, a conventional backlight will be described in detail with reference to the accompanying drawings.                         

First, a liquid crystal display device using a backlight as a basic element will be described.

In general, a liquid crystal display device includes a liquid crystal panel in which upper and lower substrates are opposed to each other with a liquid crystal layer interposed therebetween, a polarizing plate attached to upper and lower surfaces of the liquid crystal panel to transmit only light in a predetermined direction, and the liquid crystal panel. A back light provided with a constant gap with respect to the front surface to provide light to the liquid crystal panel, a case surrounding the outside surface of the backlight to support the liquid crystal panel and the backlight, and an image attached to the outside of the case to display an image. It consists of a bezel part made of stainless steel surrounded by the edge except the effective area.

As such, a liquid crystal display requires a light source for providing light. When the liquid crystal panel is a transmissive type or a transflective type, a backlight mounted on the lower surface of the liquid crystal panel becomes an essential component.

Hereinafter, the backlight will be described in detail.

1 is a perspective view of a light guide plate backlight according to the prior art, and FIGS. 2A and 2B are cross-sectional views of a light guide plate backlight according to the prior art.

As shown in FIGS. 1 and 2A, the light guide plate backlight is provided with a main support 18 supporting the backlight component and the liquid crystal panel, and light emitted in one corner of the main support 18 to emit light. The lamp 11, the light guide plate 13 for uniformly supplying the light emitted from the light emitting lamp 11 to the liquid crystal panel, and the light emitting lamp 11 is fixed and at the same time the light from the lamp light guide plate 13 A lamp housing 10 for concentrating the light, a reflector 14 provided on a lower surface of the light guide plate 13 to reflect back light emitted from the light emitting lamp 11, and an upper portion of the light guide plate 13. Diffusion Sheet 15 to uniformly diffuse the light from the light guide plate 13 and a prism positioned on the diffuser plate 15 to condense the light diffused from the diffuser to transmit to the liquid crystal panel Prism Sheet 16 and on Prism Sheet 16 The protective sheet 17 which protects the prism sheet 16 in the part, and the case 3 which fastens the said main support 18 and the liquid crystal panel are comprised.

That is, the light guide plate backlight requires the light guide plate 13, the diffuser plate 15, the prism sheet 16, and the like to uniformly radiate the beneficiation emitted from the light emitting lamp 11 to the display surface.

Here, lamp wires 53a are connected to both ends of the light emitting lamp 11 for electrical connection with an external power source, and these lamp wires 53a are drawn out to the outside and are connected to an external power source through the connector 56. Not shown).

At this time, there is a case where the cross-section of the light guide plate 13 has a wedge shape and a uniform thickness where the thickness gradually becomes thin. The former is shown in FIG. 2A and the latter is shown in FIG. 2B. When the thickness of the light guide plate 13 is uniform, the light emitting lamp 11 is further provided on the other side.

As described above, the light emitted from the light emitting lamp 11 is focused on the light guide plate 13, and then passes through the light guide plate 13 and passes through the diffusion plate 15, the prism sheet 16, and the protective sheet 17. Delivered to the cotton.

However, the light guide plate type has a low price competitiveness due to the complicated sourcing and manufacturing process of various components, and a problem of light leakage caused by a problem of matching between the lamp and the lamp housing, and the luminance is lowered because light must pass through the light guide plate. There is a problem. In addition, since the weight of the backlight is increased by the light guide plate having a predetermined thickness, there is a limit in thinning the device. In addition, the light guide plate type is low in luminance and cannot be used in a large liquid crystal display device.

In order to solve this problem and in particular, a large size liquid crystal display device, a direct type backlight having a plurality of light emitting lamps mounted under the liquid crystal panel has been proposed to provide higher luminance and more uniform light quantity distribution than the light guide plate type.

In the case of the direct type, as a way to realize a high-brightness backlight, research and development of the direct type backlight have been made by arranging a plurality of light emitting lamps on the lower side of the display screen or by arranging one light emitting lamp in a U or W shape. It is going on.

Figure 3 is a perspective view of a direct backlight according to the prior art, Figure 4 is a cross-sectional view of the direct backlight according to the prior art.

Specifically, the conventional direct type backlight has a plurality of light emitting lamps 111 arranged at regular intervals, and a case 103 for fixing and supporting the light emitting lamps 111, as shown in FIGS. 3 and 4. ) And an optical sheet including a diffusion plate 115, a prism sheet 116, and a protective sheet 117 disposed between the light emitting lamp 111 and a liquid crystal panel (not shown).

The optical sheet is to provide a light source having a uniform distribution of brightness as a whole to prevent the shape of the light emitting lamp from appearing on the display surface of the liquid crystal panel, a plurality of sheets between the liquid crystal panel to enhance the light scattering effect Are placed.

The reflector plate 114 is disposed under the light emitting lamp 111 so that the light generated from the light emitting lamp 111 can be irradiated to the display unit of the liquid crystal panel. This is to maximize the utilization efficiency of the light.

The light emitting lamp 111 is a Cold Cathode Fluorescent Lamp (CCFL), and electrodes are disposed at both ends of a tube, respectively, and a power lead wire which transfers power for driving a lamp to both electrodes of the light emitting lamp. 109 and 109a are connected to emit light when power is applied to the electrode. The light emitting lamp 111 is fitted into grooves formed on both sides of the outer case 103.

However, in the case of the direct backlight as described above, various diffusion plates and optical sheets are required in order to emit uniform light without directly generating bright bright lines directly above the light emitting lamp, and between the light emitting lamp 111 and the liquid crystal panel. There was a problem in that the thickness is thick because a certain space must be secured.

The present invention has been made in order to solve the above problems, by configuring a lower reflector to have a concave portion at a predetermined interval and by placing a light emitting lamp in the concave to further include an upper reflector on each light emitting lamp, than the light guide plate backlight An object of the present invention is to provide a direct type backlight having a lighter weight and a uniform light thickness than a conventional direct type backlight.

In order to achieve the above object, the direct type backlight of the present invention includes a lower reflection plate having at least one recess on a surface of the liquid crystal panel facing the display surface, and at least one light emission disposed corresponding to the recess of the lower reflection plate. And a lamp, at least one upper reflecting plate disposed above the light emitting lamp corresponding to the recess of the lower reflecting plate, and an optical sheet formed between the upper reflecting plate and the liquid crystal panel.

That is, the present invention is characterized in that the luminance is uniform by further including an upper reflector in addition to the conventional lower reflector. In this case, the light emitting lamp is disposed inside the recess of the lower reflector, and the upper reflector is disposed on the light emitting lamp such that the upper and lower reflecting plates surround the light emitting lamp.

The upper reflector may be made of a material that completely reflects light, or partially insert a transmission material to transmit and diffuse light.

Therefore, the light emitting lamp is reflected not only in the lower reflecting plate but also in the upper reflecting plate to provide uniform light brightness, and unlike the light guide plate type, the light guide plate is unnecessary, so that the device can be made lighter and thinner.

Hereinafter, the direct type backlight according to the present invention will be described in detail with reference to the accompanying drawings.

5 is a perspective view of a direct backlight according to the present invention, FIG. 6 is a cross-sectional view of a direct backlight along the line II ′ of FIG. 5, and FIG. 7 is a cross-sectional view of a direct backlight showing an optical path according to the present invention. to be.

As shown in FIG. 5 and FIG. 6, the direct type backlight according to the present invention includes a lower reflector plate 514 having a plurality of recesses arranged at regular intervals, and are respectively inserted into the recesses so as to be parallel to the recesses. A plurality of light emitting lamps 511 for providing light, an upper reflecting plate 550 provided on an upper portion of a recess in which each of the light emitting lamps 511 is disposed, and an upper reflecting plate 550 disposed on the upper reflecting plate 550, The diffusion plate 515 uniformly diffuses the light, and a prism sheet 516 positioned on the diffusion plate 515 to collect and diffuse the light diffused from the diffusion plate.

A protective sheet for protecting the prism sheet may be further provided on the prism sheet 516. Generally, it is called an optical sheet including the diffusion plate, the prism sheet, and the protective sheet. The purpose is to prevent the shape of the light emitting lamp from appearing on the display surface of the liquid crystal panel and to provide a light source having a uniform brightness distribution as a whole. In order to enhance the light scattering effect, a plurality may be arranged.

The above components are accommodated and fixed by a support case (not shown). The direct type backlight configured as described above is disposed under the liquid crystal panel to provide flat light having uniform luminance to the liquid crystal panel.

In particular, as shown in FIG. 7, light leaking downward from the light emitting lamp 511 is reflected in multiple directions by the concave portion of the lower reflector 514 to provide uniform luminance. In the case of using a flat reflector without a concave portion, since the light is vertically reflected by the reflector, there is a problem that the luminance of the portion where the light emitting lamp is installed and the portion where the light emitting lamp is not provided are uneven.

The concave portion of the lower reflector 514 may be manufactured in various forms. The concave portion may have a curved surface or a straight surface, and the concave portion may have a flat shape, a U shape, or a W shape. However, the light emitting lamp is also made of straight, U-shaped, W-shaped so as to be parallel to the concave portion, and disposed so as to be located in the middle of the concave portion.

In addition, when the direct type backlight is used in a monitor or TV liquid crystal display device requiring high brightness, a plurality of light emitting lamps may be disposed. As the number of the light emitting lamps increases, the number of recesses in the lower reflector should vary accordingly. something to do.

In addition, the upper reflector 550 is further provided on the upper part of the light emitting lamp 511, and the light which is directly emitted upwards of the upper light emitting lamp 511 is reflected by the upper reflecting plate 550 in multiple directions to provide more uniform luminance. .

In this case, the width of the upper reflector 550 is smaller than the width of the recess of the lower reflector 514 to allow the light reflected between the lower reflector 514 and the upper reflector 550 to pass therethrough. In order to make the width of the upper reflector 550 larger than the width of the recess, the upper reflector 550 is provided at a predetermined interval from the recess.

In addition, the upper reflector 550 is disposed in a size corresponding to the concave portion, and the plurality of upper reflector 550 is not connected to each other and is separately stored and fixed by a support case. It may be connected in one piece. The connecting portion may be made of the same material as the upper reflector 550, and may be made of a transmission material to reduce luminance decrease.

The upper and lower reflecting plates 514 may be formed of a metal material such as Al having a high reflectance, and a transmissive part may be formed by inserting a transmissive material between the upper reflecting plates 550. That is, the light reflected by the upper reflector and the light passing through the upper reflector may be simultaneously implemented to provide more uniform brightness.

In the backlight having the above structure, when power is applied to the electrode of the light emitting lamp, electrons existing in the discharge space are attracted to the electrode and collide with each other to start discharge, and electrons flowing by the discharge collide with other electrons and are ultraviolet rays. Ultraviolet rays collide with the phosphor layer applied to the inner wall of the lamp to produce visible light. The visible light is emitted from the light emitting lamp toward the liquid crystal panel, and the light leaking out to the bottom is reflected in the multi direction toward the top by the recess of the lower reflector 514, and the light emitted from the upper is reflected by the upper reflector 550. Reflected in multiple directions or transmitted and diffused through the transmissive portion of the upper reflector plate to provide uniform luminance for all exit surfaces. Therefore, it is not necessary to use a light guide plate like a conventional light guide plate backlight to make a uniform planar light source, and by providing an upper reflector, it is possible to provide more uniform light than a conventional direct backlight.

On the other hand, the present invention described above is not limited to the above-described embodiment and the accompanying drawings, it is possible that various substitutions, modifications and changes within the scope without departing from the technical spirit of the present invention. It will be apparent to those of ordinary skill in Esau.

The direct type backlight of the present invention as described above has the following effects.

First, the light emitting lamp may be disposed inside the recess of the lower reflecting plate, and the upper reflecting plate may be further provided on the light emitting lamp to provide high luminance and uniform light brightness.                     

Second, unlike the light guide plate type, a heavy light guide plate is unnecessary, so that the device can be made lighter and thinner.

Claims (7)

A lower reflection plate having at least one concave portion on a surface of the liquid crystal panel facing the display surface; At least one light emitting lamp disposed corresponding to the concave portion of the lower reflector; At least one upper reflecting plate corresponding to a recess of the lower reflecting plate and disposed above the light emitting lamp; The direct type backlight, characterized in that it comprises an optical sheet formed between the upper reflector and the liquid crystal panel. The method of claim 1, Cross section of the recess is a direct type backlight, characterized in that made of a curved surface or a straight surface. The method of claim 1, And the at least one upper reflector is integrally connected to and supported in one piece. The method of claim 1, And the upper reflection plate partially has a transmissive portion. The method of claim 1, The direct type backlight is characterized in that the width of the upper reflector is larger or smaller than the width of the recess. The method of claim 1, The direct light type backlight, characterized in that the light emitting lamp and the recess is made of a straight, U-shaped or W-shaped. The method of claim 1, The optical sheet is a direct type backlight, characterized in that it comprises a diffusion plate, a prism sheet and a protective sheet.

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