KR20110077268A - Light guide plate for polarizing light, back light unit and liquid crystal display device having thereof - Google Patents

Light guide plate for polarizing light, back light unit and liquid crystal display device having thereof Download PDF

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Publication number
KR20110077268A
KR20110077268A KR1020090133783A KR20090133783A KR20110077268A KR 20110077268 A KR20110077268 A KR 20110077268A KR 1020090133783 A KR1020090133783 A KR 1020090133783A KR 20090133783 A KR20090133783 A KR 20090133783A KR 20110077268 A KR20110077268 A KR 20110077268A
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KR
South Korea
Prior art keywords
light
light guide
liquid crystal
guide plate
guide layer
Prior art date
Application number
KR1020090133783A
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Korean (ko)
Inventor
김성기
이재원
Original Assignee
엘지디스플레이 주식회사
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Priority to KR1020090133783A priority Critical patent/KR20110077268A/en
Publication of KR20110077268A publication Critical patent/KR20110077268A/en

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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/0001—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems
    • G02B6/0011—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the light guides being planar or of plate-like form
    • G02B6/0033—Means for improving the coupling-out of light from the light guide
    • G02B6/005—Means for improving the coupling-out of light from the light guide provided by one optical element, or plurality thereof, placed on the light output side of the light guide
    • G02B6/0055—Reflecting element, sheet or layer
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/0001—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems
    • G02B6/0011—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the light guides being planar or of plate-like form
    • G02B6/0033—Means for improving the coupling-out of light from the light guide
    • G02B6/0056—Means for improving the coupling-out of light from the light guide for producing polarisation effects, e.g. by a surface with polarizing properties or by an additional polarizing elements
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333—Constructional arrangements; Manufacturing methods
    • G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
    • G02F1/133524—Light-guides, e.g. fibre-optic bundles, louvered or jalousie light-guides
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333—Constructional arrangements; Manufacturing methods
    • G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
    • G02F1/133528—Polarisers

Abstract

The liquid crystal display device of the present invention is to reduce the manufacturing cost and to reduce the thickness, the liquid crystal panel that displays an image; A light source for emitting light; A light guide plate having one side facing the light source and guiding light incident from the light source to one side, and polarizing the incident light in one direction to supply the liquid crystal panel; An optical sheet disposed on the light guide plate to improve efficiency of light input from the light guide plate; And a polarizing plate attached to the liquid crystal panel to adjust the transmittance of light transmitted through the liquid crystal panel.

LCD, LGP, polarized light, S wave, P wave

Description

LIGHT GUIDE PLATE FOR POLARIZING LIGHT, BACK LIGHT UNIT AND LIQUID CRYSTAL DISPLAY DEVICE HAVING THEREOF}

The present invention relates to a light guide plate for polarizing light, to a backlight device and a liquid crystal display device having the same, and to a light guide plate for polarizing light capable of guiding and polarizing light to improve brightness. It is about.

Recently, with the development of various portable electronic devices such as mobile phones, PDAs, and notebook computers, there is a growing demand for flat panel display devices for light and thin applications. Such flat panel displays have been actively researched, such as liquid crystal displays (LCDs), plasma display panels (PDPs), field emission displays (FEDs), and vacuum fluorescent displays (VFDs). Currently, liquid crystal displays (LCDs) are mainly in the spotlight for the realization of large-area screens.

The liquid crystal display is a transmissive display and displays a desired image on the screen by controlling the amount of light passing through the liquid crystal layer by the refractive index anisotropy of the liquid crystal molecules. Therefore, in the liquid crystal display device, a back light unit, which is a light source passing through the liquid crystal layer, is provided for displaying an image. In general, the backlight unit may be classified into two types.

First is a side type backlight device in which a lamp is provided on the side of the liquid crystal panel to provide light to the liquid crystal layer, and second is a direct type backlight device in which the lamp provides light directly from the lower part of the liquid crystal panel.

The side type backlight device may be installed on the side of the liquid crystal panel to supply light to the liquid crystal layer through the reflection plate and the light guide plate. Therefore, since the thickness can be made thin, it is mainly used in notebooks and the like which require a thin display device.

The direct type backlight device is not only applied to a large area liquid crystal panel because the light emitted from the lamp is directly supplied to the liquid crystal layer, so that high brightness is possible.

FIG. 1 is a diagram schematically illustrating a structure of a liquid crystal display device having an edge type backlight device.

As shown in FIG. 1, the liquid crystal display device 1 is largely provided on a liquid crystal panel 40 and a rear surface of the liquid crystal panel 40 to supply light to the liquid crystal panel 3. Device 10. The liquid crystal panel 3 is where the actual image is realized, and the liquid crystal layer formed between the transparent first substrate 50 and the second substrate 45 such as glass, and the first substrate 50 and the second substrate 45. (Not shown). In particular, although not shown in the drawing, the first substrate 50 is a TFT substrate on which a driving element such as a thin film transistor and a pixel electrode are formed, and the second substrate 45 is a color filter layer. It is a color filter substrate formed. In addition, the driving circuit unit 5 is provided on the side of the first substrate 50 to apply a signal to the thin film transistor and the pixel electrode formed on the first substrate 50, respectively.

The backlight device 10 may include a lamp 11 that actually emits light, a light guide panel 13 that guides light emitted from the lamp 11 toward the liquid crystal panel 40, and emits light from the lamp 11. It consists of an optical sheet consisting of a reflector 17 reflecting light to the light guide plate 13 to improve light efficiency, a diffusion sheet 15 and a prism sheet 20 disposed on the light guide plate 13.

In the backlight device 10 having the structure described above, light emitted from the lamps 11 provided on both sides of the light guide plate 13 is incident on the light guide plate 13 through the side surface of the light guide plate 13, and the incident light is guided by the light guide plate ( 13 is supplied to the liquid crystal panel 40 through the upper surface, and then the optical efficiency is improved by the optical sheet and then incident to the liquid crystal panel 40.

The light output from the light guide plate 13 is incident on the diffusion sheet 15 and the prism sheet 20 of the optical sheet, and is diffused by the diffusion sheet, and then its propagation direction is changed to the front by the prism sheet 20. Is output.

Flat plates 5a and 5b are disposed on the upper and lower surfaces of the liquid crystal panel 40, respectively. The light emitted from the backlight device 10 is polarized in the first polarizing plate 5a attached to the first substrate 50 and the polarization state of the light is converted while passing through the liquid crystal layer, and then attached to the second substrate 45. It is emitted to the outside through the second polarizing plate 5b. In this case, the image is realized by adjusting the transmittance of light transmitted through the second piece light plate 5b according to the change in the polarization state of the light by the liquid crystal layer.

However, the above liquid crystal display device has the following problems. In the liquid crystal display device, polarizing plates 5a and 5b must be attached to upper and lower parts in order to polarize the light incident on the liquid crystal panel. The polarizing plates 5a and 5b are expensive films and the manufacturing cost increases as the polarizing plates are attached. The thickness of the liquid crystal display device is increased. In addition, there is a problem that the manufacturing process is complicated because the process for attaching the polarizing plate is added.

The present invention is to solve the above problems, to provide a light guide plate, a backlight device and a liquid crystal display device having a light guide plate which can reduce the manufacturing cost and thickness by removing the polarizing plate attached to the lower portion of the liquid crystal panel. It is done.

In order to achieve the above object, the light guide plate according to the present invention comprises a first light guide layer; And a second light guide layer formed on the first light guide layer to reflect the S-wave of the input light and transmit unpolarized light.

The refractive index of the first light guide layer is greater than that of the second light guide layer, wherein the refractive index of the first light guide layer is 1.45-1.60 and the refractive index of the second light guide layer is 1.30-1.36. The second light guide layer is formed obliquely at a Brewster angle with respect to an upper surface of the first light guide layer.

In addition, the backlight device according to the present invention includes a light source for emitting light; And light emitted from the light source is incident on one side of the light source by facing one side of the light source, and reflects the S-waves of the light that is formed in the first light guide layer and the first light guide layer and outputs the light upward. The non-light is composed of a light guide plate made of a second light guide layer through which light is transmitted.

In addition, the liquid crystal display device according to the present invention comprises a liquid crystal panel that displays an image; A light source for emitting light; A light guide plate having one side facing the light source and guiding light incident from the light source to one side, and polarizing the incident light in one direction to supply the liquid crystal panel; An optical sheet disposed on the light guide plate to improve efficiency of light input from the light guide plate; And a polarizing plate attached to the liquid crystal panel to adjust the transmittance of light transmitted through the liquid crystal panel.

At this time, the polarization direction of the polarized light output from the light guide plate and the optical axis of the polarizing plate are perpendicular to each other.

In the present invention, since a separate polarizing plate is not necessary under the liquid crystal panel, the thickness of the liquid crystal display device can be reduced and manufacturing cost can be reduced.

Hereinafter, a backlight device and a liquid crystal display device having the same according to the present invention will be described in detail with reference to the accompanying drawings.

The best way to reduce the manufacturing cost and reduce the thickness of the liquid crystal display device by the polarizing plate is to remove the polarizing plate itself from the liquid crystal display device and to provide an alternative article. That is, it is provided with an optical member that performs a polarizing function of a lower cost and thinner than the polarizing plate. However, even in this case, it is impossible to solve the increase in manufacturing cost and increase in thickness by the optical member.

Another method of reducing the manufacturing cost and reducing the thickness of the liquid crystal display device by the polarizing plate is to impart a polarization function to the configuration originally provided in the liquid crystal display device. In this case, the original configuration does not increase the manufacturing cost or increase the thickness of the liquid crystal display device.

The present invention reduces the manufacturing cost and reduces the thickness of the liquid crystal display device by providing a polarizing function to the light guide plate of the original configuration to remove the polarizing plate. The light guide plate and the liquid crystal display device according to the present invention will be described in detail as follows.

2 is an exploded perspective view showing the structure of a liquid crystal display device according to the present invention, and FIG. 3 is a cross-sectional view of the liquid crystal display device according to the present invention.

As shown in FIGS. 2 and 3, the liquid crystal display device 100 includes a liquid crystal panel 140 and a backlight device 110. In this case, the backlight device 110 is positioned below the liquid crystal panel 140 to supply light to the liquid crystal panel 140.

The backlight device 110 is disposed under the liquid crystal panel 140 such that the light source 111 emits light and supplies the light to the liquid crystal panel 140, and the side surface is in contact with the light source 111. ) A light guide plate 113 for supplying light input from the light to the liquid crystal panel 140, a reflector disposed below the light guide plate 113 to reflect light incident to the bottom of the light guide plate 113 to the liquid crystal panel 140. 117, a diffusion sheet 115 disposed between the liquid crystal panel 140 and the light guide plate 113 to diffuse light guided by the light guide plate 113, the diffusion sheet 115 and the liquid crystal panel 140. A first prism sheet 120 disposed between the first prism sheet 120 and the first prism sheet 120, the prism being disposed on the first prism sheet 120, the prism being arranged on the first prism sheet 120. The prism sheet 120 is arranged in a direction different from that of the prism, so that the first prism It consists of a second prism sheet 130, which again refracts the refracted light at 120.

In addition, a polarizer 105 is attached to an upper surface of the liquid crystal panel 140. However, unlike the related art, the polarizer is not attached to the lower surface of the liquid crystal panel 140. In the present invention, the light guide plate 113 not only functions to guide light to the liquid crystal panel 140 but also serves as a polarizer attached to the lower portion of the liquid crystal panel 140.

Light emitted from the backlight device 110 is incident on the light guide plate 113, and the light guide plate 113 polarizes and outputs the incident light, and the output light is diffused from the diffusion sheet 115 and the prism sheets 120 and 130. After the light is collected, the light is supplied to the liquid crystal panel 140. At this time, the light guide plate 113 guides the incident natural light from one side to the other side and simultaneously outputs light polarized in one direction to the liquid crystal panel 140.

That is, since the light guide plate 113 does not simply guide light to the liquid crystal panel 140 but polarizes and guides input light, the light guide plate 113 may be referred to as a polarization light guide plate.

The light incident on the liquid crystal panel 140 is transmitted through the polarizing plate 105, and then is output to the outside through the polarizing plate 105. At this time, since the polarization state of the light output from the light guide plate 113 and the optical axis of the polarizing plate 105 are vertical, the transmittance of the light passing through the polarizing plate 105 is adjusted according to the orientation of the liquid crystal molecules of the liquid crystal layer, thereby controlling the image in the liquid crystal display device. Will be able to implement

As shown in FIG. 4, the liquid crystal panel 140 includes a first substrate 150 and a second substrate 145 and a liquid crystal layer (not shown) therebetween. When the plurality of gate lines 156 and the data lines 157 are arranged in a matrix to define the plurality of pixel regions P in the first substrate 150, thin film transistors T may be formed in each pixel region P. FIG. ) And a pixel electrode 158 electrically connected to the thin film transistor T. Gate pads and data pads are formed at the ends of the gate line 156 and the data line 157 to connect the gate line 156 and the data line 157 with an external driving device so that the gate line 156 and An external signal is input through the data line 125.

Although not shown in the drawing, the thin film transistor T is connected to the gate line 156 to receive a gate signal from the outside through the gate line 156, and a gate insulating layer formed on the gate electrode. And a semiconductor layer formed on the gate insulating layer and activated as a scan signal is input to a gate electrode to form a channel, and formed on the semiconductor layer to form a channel on the semiconductor layer by a scan signal. A source electrode and a drain electrode apply the image signal input through the pixel electrode 158.

The second substrate 145 is formed in an image non-display area such as a gate line 156, a data line 157, or a thin film transistor T, in which no actual image is formed. Color consisting of a black matrix 146 that transmits and prevents deterioration of image quality, and a sub color filter layer of R (Red), G (Green), and B (Blue) formed in the pixel to realize an actual image. The filter layer 147 is formed.

As described above, a liquid crystal layer (not shown) is formed between the configured first substrate 150 and the second substrate 145 to form the liquid crystal panel 140, and the second substrate of the liquid crystal panel 140 is formed. The polarizer 105 is attached to the 145.

As the light source 111, a fluorescent lamp such as a cold cathode lamp (CCFL) is mainly used. A reflection layer is formed on an inner surface of the housing 112 in which the light source 111 is accommodated to reflect the light emitted from the light source 111 to the light guide plate 113. In addition, the light source 111 may be formed only on one side of the light guide plate 113 as shown in FIG. 3, and the light emitted from the light source 111 may be formed on both sides of the light guide plate 113. It may be incident to the light guide plate 113 through both sides.

As the light source 111, not only a fluorescent lamp but also a light emitting device (LED) may be used. The LED is a light source that emits light by itself, and emits R, G, and B monochromatic light, and thus, when applied to the backlight unit, the color reproducibility is good and driving power can be reduced.

When such an LED is used as the light source 111 of the backlight unit, when the light emitted from the LED is supplied to the liquid crystal panel, the monochromatic light is not directly supplied, but white light is supplied, thereby making the monochromatic light emitted from the light emitting device into white light. For this purpose, a monochromatic light emitting device and a phosphor are used, or an infrared wavelength light emitting device and a phosphor are used, or the monochromatic light emitted from the red (R), green (G) and blue (B) light emitting devices is mixed. That is, when using LED as the light source 111 of a backlight part, several LED is arrange | positioned at the side surface of the light guide plate 113, and white light or monochromatic light is input into the light guide plate 113. FIG.

The diffusion sheet 115 is used to diffuse the light output from the light guide plate 113 to make the luminance constant. The diffusion sheet 115 is manufactured by distributing spherical seeds made of acrylic resin on a base film made of polyethylene terephthalate (PET). . The light output from the light guide plate 113 is diffused in the spherical seed so that the brightness of the light output is uniform. Although the diffusion sheet 115 is disposed only between the light guide plate 113 and the first prism sheet 120, a diffusion sheet may be additionally provided between the second prism sheet 130 and the liquid crystal panel 140. Could be

The prism sheets 120 and 130 form a regular prism with an acrylic resin on a base film mainly made of polyethylene terephthalate (PET), thereby refracting incident light so that the light propagates in the front direction. At this time, the prisms of the first prism sheet 120 and the second prism 130 are arranged perpendicular to each other, and the front light of the light is improved by refracting the input light toward the front side. At this time, as shown in the figure, since the prism of the first prism sheet 120 and the second prism 130 is vertically arranged in different directions, that is, x-direction and y-direction, x- of the incident light Direction and y-direction are refracted to allow light to enter the liquid crystal panel 140 vertically.

The light guide plate 113 polarizes the light input from the side to the other side while propagating from one side to the other side, and then supplies the light to the liquid crystal panel 140. That is, the light guide plate 113 of the present invention not only plays the same role as the general light guide plate but also plays the same role as the general polarizer.

5 is a view showing the structure of a light guide plate according to the present invention.

As shown in FIG. 5, the light guide plate 113 according to the present invention has a first light guide layer 113a made of a material having a high refractive index and a first light guide layer inside the first light guide layer 113a at a predetermined width. The second light guide layer 113b is formed at a predetermined angle θ and has a lower refractive index than the first light guide layer 113a.

The first light guide layer 113a is made of a high refractive material such as polymethyl-methacrylate (PMMA) or glass or polyethylene terephthalate (PET), and preferably has a refractive index of about 1.45-1.60, and the second light guide layer 113b. ) Is formed of a low refractive material such as a high fluorinated polymer, and preferably has a refractive index of about 1.30-1.36.

The light guide plate 113 may be formed of polymethyl-methacrylate (PMMA) or glass or polyethylene terephthalate (PET) to form a first light guide layer 113a having a wedge shape having a narrower thickness on one side of both sides. After etching the first light guide layer 113a, a low refractive index material such as a high fluorinated polymer is filled in the etched region.

In the light guide plate 113 configured as described above, when light is incident through the side surface, partly polarized light is output to the outside while the light is transmitted through the second light guide layer 113b, and the light that is not polarized is light guide plate 113. Proceeds to the other side of, all the light is polarized and transmitted to the outside while passing through the plurality of second light guide layer (113b).

FIG. 6 is a diagram illustrating the principle of polarization and guidance of light in the light guide plate 113 having the above structure.

As shown in FIG. 6, the light output from the light source 110 disposed on the side of the light guide plate 113 is unpolarized light including S and P waves perpendicular to each other as natural light. After the natural light is incident and propagated to the side of the first light guide layer 113a and reaches the first second light guide layer 113b, part of the natural light is reflected on the surface of the second light guide layer 113b, and the remaining light is The second light guide layer 113b penetrates and propagates.

At this time, when the light incident on the second light guide layer 113b is incident at the Brewster angle, the light reflected by the second light guide layer 113b is completely polarized, and thus S wave is output. At this time, assuming that light is incident perpendicularly to the side of the first light guide layer 113a, the Brewster angle may be determined according to the formation angle of the second light guide layer 113b. When using a PMMA having a refractive index of 1.56 as the first light guide layer 113a and a high fluorinated polymer having a refractive index of ni as 1.34 as the second light guide layer 113b, the Brewster is nt / ni = 1.16. The angle θ becomes θ = tan −1 (nt / ni) = tan −1 1.16 = 49.26 °.

In other words, as shown in FIG. 7, since the angle between the normal direction of the surface of the second light guide layer 113b and the incident direction of light is the Brewster angle θ, the refractive index nt is increased to the first light guide layer 113a. When using a PMMA of 1.56 and a high fluorinated polymer having a refractive index (ni) of 1.34 as the second light guide layer 113b, the upper surface of the first light guide layer 113a and the surface of the second light guide layer 113b are used. The angle is the Brewster angle θ. As a result, when the second light guide layer 113b is formed at an angle of θ = 49.26 ° with the top surface of the first light guide layer 113a, the S-wave completely polarized on the surface of the second light guide layer 113b is reflected. The liquid crystal panel 140 is supplied.

The light transmitted through the second light guide layer 113b is lightly polarized light. That is, light containing part of P wave and S wave. When the finely polarized light reaches the second second light guide layer 113b, a part of the S-waves are reflected from the surface of the second second light guide layer 113b and supplied to the liquid crystal panel 140. The finely polarized light is transmitted again to the second light guide layer 113b, and the above process is repeated until the second light guide layer 113a reaches the other side of the first light guide layer 113a. ) Is supplied.

Meanwhile, the reflecting plate 117a may be disposed outside the other side surface of the first light guide layer 113a. As such, when the reflecting plate 117a is disposed, the reflecting plate 117a reflects light reaching the other side of the first light guide layer 113a and enters the first light guide layer 113a again. At this time, the incident light is also finely polarized light (of course, the S wave is mostly reflected and output by the previous process, but the S wave component still remains).

Light that is incident again on the other side of the first light guide layer 113a by the reflector plate 117a is incident on the second light guide layer 113b, and a part of the S wave is formed on the surface of the second light guide layer 113b. Is reflected. The reflected S-wave propagates to the lower part of the light guide plate 113, and then is reflected back by the reflecting plate 117 disposed under the light guide plate 113 and supplied to the liquid crystal panel 140. The light transmitted through the second light guide layer 113b is reflected by the second wave guide layer 113b and then reflected by the reflector plate 117 to be supplied to the liquid crystal panel 140.

The above process is repeated until the light reaches one side of the first light guide layer 113a, that is, the side opposite to the light source 110, and the polarized S wave is supplied to the liquid crystal panel 140.

As described above, in the present invention, the light incident to one side of the light guide plate 113 is polarized with the S wave of light until it is propagated to the other side and reflected from the other side and propagated to one side and is supplied to the liquid crystal panel 140.

The light (S wave) output from the light guide plate 113 is supplied to the liquid crystal panel 140 in a state in which the light is uniformly and straightness is improved in the diffusion sheet 115 and the prism sheets 120 and 130. The polarizing plate 105 attached to the upper surface of the liquid crystal panel 140 has an optical axis perpendicular to the polarization direction of the light output from the light guide plate 113. Therefore, when no signal is applied to the liquid crystal panel 140, that is, in the off state, the S-wave output from the light guide plate 113 maintains the polarization state while leaving the liquid crystal panel 140 and then the polarizing plate 105. Are all absorbed by), and the black state is displayed on the screen.

When a signal is applied to the liquid crystal panel 140, that is, in an on state, the S wave polarized and output from the light guide plate 113 passes through the liquid crystal layer of the liquid crystal panel 140 as it is, and thus the polarization state is changed to P wave. White is transmitted through the second polarizing plate 105.

In addition, if the intensity of the signal applied to the liquid crystal panel 140 is properly adjusted, the arrangement of the liquid crystal molecules of the liquid crystal layer of the liquid crystal panel 140 can be appropriately controlled, so that the degree of retardation can be adjusted. As a result, the gray level can be displayed by adjusting the transmittance of light passing through the liquid crystal layer when the liquid crystal panel 140 is turned on.

As described above, in the present invention, the light guide plate 113 not only guides the light to the liquid crystal panel 140 but also polarizes the light by the light guide plate 113. Thus, the liquid crystal panel is conventionally attached to the lower side of the liquid crystal panel 140. There is no need for a polarizer to polarize the light supplied to 140. Therefore, since the polarizing plate is not necessary, the thickness of the liquid crystal display device can be reduced and manufacturing cost can be reduced.

Meanwhile, in the above description, the liquid crystal panel and the backlight device are described in a specific structure, but this is for convenience of description and not for limiting the present invention. According to the present invention, a light guide plate that removes a polarizing plate under the liquid crystal panel used in the related art and polarizes light incident on the backlight device, that is, a polarizing light guide plate is provided so as to polarize and guide the light supplied to the liquid crystal panel. The liquid crystal panel and the backlight device may also be applied to the present invention. In other words, other examples or modifications of the present invention can be easily created by anyone in the technical field to which the liquid crystal display device using the basic concept of the present invention belongs.

1 is a view showing the structure of a conventional liquid crystal display device.

2 is an exploded perspective view showing the structure of a liquid crystal display device according to the present invention;

3 is a cross-sectional view showing the structure of a liquid crystal display device according to the present invention.

4 is a cross-sectional view showing the structure of a liquid crystal panel of the liquid crystal display device according to the present invention.

5 is a view showing the structure of a light guide plate of the liquid crystal display device according to the present invention.

6 is a view showing the polarization state of light in the light guide plate of the liquid crystal display device according to the present invention.

7 is a view showing an angle of a second light guide layer in the light guide plate according to the present invention;

Claims (11)

A first light guide layer; And a second light guide layer formed on the first light guide layer to reflect S-waves of the input light and transmit unpolarized light. The light guide plate of claim 1, wherein a refractive index of the first light guide layer is larger than a refractive index of the second light guide layer. The light guide plate according to claim 2, wherein the refractive index of the first light guide layer is 1.45-1.60 and the refractive index of the second light guide layer is 1.30-1.36. The light guide plate of claim 2, wherein the first light guide layer is made of polymethyl-methacrylate (PMMA), glass, or polyethylene terephthalate (PET). The light guide plate of claim 2, wherein the second light guide layer is formed obliquely at a Brewster angle with respect to an upper surface of the first light guide layer. A light source for emitting light; And One side faces the light source, and light emitted from the light source is incident through the one side, reflects the S-waves of the light that is formed in the first light guide layer and the first light guide layer, and outputs the light upwards, and is not polarized. A backlight device comprising a light guide plate made of a second light guide layer for transmitting light. The method of claim 6, A first reflector disposed on the other side of the light guide plate to reflect light output to the other side of the light guide plate; And And a second reflecting plate reflecting the S-waves reflected from the second light guiding layer among the light reflected from the first reflecting plate and incident to the second light guiding layer and outputting the reflected S wave to the upper part of the light guiding plate. . The backlight device of claim 6, wherein the light source comprises a fluorescent lamp or a light emitting device (LED). A liquid crystal panel on which an image is displayed; A light source for emitting light; A light guide plate having one side facing the light source and guiding light incident from the light source to one side, and polarizing the incident light in one direction to supply the liquid crystal panel; An optical sheet disposed on the light guide plate to improve efficiency of light input from the light guide plate; And And a polarizing plate attached to the liquid crystal panel to adjust transmittance of light transmitted through the liquid crystal panel. The method of claim 9, wherein the light guide plate, A first light guide layer; And a second light guide layer formed on the first light guide layer to reflect S-waves of the input light and transmit unpolarized light. The liquid crystal display of claim 9, wherein the polarization direction of the polarized light output from the light guide plate and the optical axis of the polarizing plate are perpendicular to each other.
KR1020090133783A 2009-12-30 2009-12-30 Light guide plate for polarizing light, back light unit and liquid crystal display device having thereof KR20110077268A (en)

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KR1020090133783A KR20110077268A (en) 2009-12-30 2009-12-30 Light guide plate for polarizing light, back light unit and liquid crystal display device having thereof

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KR1020090133783A KR20110077268A (en) 2009-12-30 2009-12-30 Light guide plate for polarizing light, back light unit and liquid crystal display device having thereof

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR20160062340A (en) * 2014-11-24 2016-06-02 엘지디스플레이 주식회사 Backlight unit and liquid crystal display device using the same

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR20160062340A (en) * 2014-11-24 2016-06-02 엘지디스플레이 주식회사 Backlight unit and liquid crystal display device using the same

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