KR20100131300A - Back light unit and liquid crystal display device having thereof - Google Patents

Back light unit and liquid crystal display device having thereof Download PDF

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Publication number
KR20100131300A
KR20100131300A KR1020090050117A KR20090050117A KR20100131300A KR 20100131300 A KR20100131300 A KR 20100131300A KR 1020090050117 A KR1020090050117 A KR 1020090050117A KR 20090050117 A KR20090050117 A KR 20090050117A KR 20100131300 A KR20100131300 A KR 20100131300A
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KR
South Korea
Prior art keywords
light
prism
prism sheet
liquid crystal
guide plate
Prior art date
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KR1020090050117A
Other languages
Korean (ko)
Inventor
박재현
Original Assignee
엘지디스플레이 주식회사
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Priority to KR1020090050117A priority Critical patent/KR20100131300A/en
Publication of KR20100131300A publication Critical patent/KR20100131300A/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
    • G02B6/0053—Prismatic sheet or layer; Brightness enhancement element, sheet or layer
    • 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
    • G02F1/1336—Illuminating devices
    • G02F1/133615—Edge-illuminating devices, i.e. illuminating from the side

Abstract

PURPOSE: A backlight apparatus and a liquid crystal display device equipping the same for reducing a manufacturing cost are provided to minimize the thickness of the liquid crystal display by removing a diffusion sheet of the backlight. CONSTITUTION: A lamp(211) emits the light. A light guide substrate(213) guides the light emitted from the lamp. A first prism sheet(226) is horizontally extended to a progressive direction of the light on the light guide substrate. A second prism sheet(228) is extended to a first prism sheet of a triangle sheet.

Description

BACK LIGHT UNIT AND LIQUID CRYSTAL DISPLAY DEVICE HAVING THEREOF}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight device of a liquid crystal display device, and in particular, by constructing two prism sheets with an optical sheet that improves optical efficiency of light emitted from a lamp, light supplied to the liquid crystal panel can improve efficiency and reduce manufacturing costs. And a backlight device capable of minimizing its thickness and a liquid crystal display device having the same.

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 device is a transmissive display element, and displays a desired image on the screen by adjusting 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 device 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 3 and a rear surface of the liquid crystal panel 3 to supply light to the liquid crystal panel 3. Device 10. The liquid crystal panel 3 is where an actual image is realized. The liquid crystal layer formed between the transparent first substrate 3a and the second substrate 3b and the first substrate 3a and the second substrate 3b, such as glass. (Not shown). In particular, although not shown in the drawing, the first substrate 3a 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 3b is a color filter layer. It is a color filter substrate formed. In addition, a driving circuit unit 5 is provided on the side of the first substrate 3a to apply signals to the thin film transistor and the pixel electrode formed on the first substrate 3a, respectively.

The backlight device 10 includes a lamp 11 that actually emits light, a light guide panel 13 that guides the light emitted from the lamp 11 toward the liquid crystal panel 3, and emits the light from the lamp 11. Reflector 17 reflects the light to the light guide plate 13 to improve light efficiency, and is disposed on the light guide plate 13 to diffuse and collect light guided through the light guide plate 13 to improve light efficiency. It consists of an optical sheet consisting of an optical sheet 20 to.

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 incident on the liquid crystal panel 3 after the optical efficiency is improved by the optical sheet 20 disposed on the upper surface.

The optical sheet 20 is composed of a diffusion sheet and a prism sheet. After the incident light is diffused by the diffusion sheet, the traveling direction is changed to the front by the prism sheet and output.

2 is a perspective view showing in detail the optical sheet 16 consisting of the diffusion sheet and the prism sheet.

As shown in FIG. 2, the liquid crystal display device 1 includes a liquid crystal panel 40 and a backlight device 10. The backlight device 10 is positioned below the liquid crystal panel 40 to supply light to the liquid crystal panel 40.

The backlight device 10 includes a light source 11 made of a lamp, a housing 12 accommodating the light source 11, and a side surface of the backlight device 10 disposed under the liquid crystal panel 40 so as to contact the light source 11. A light guide plate 13 for supplying light input through the liquid crystal panel 40, a reflector plate disposed below the light guide plate 13 to reflect light incident to the bottom of the light guide plate 13 to the liquid crystal panel 40 ( 17) a first diffusion sheet 22 disposed between the liquid crystal panel 40 and the light guide plate 13 to diffuse light guided by the light guide plate 13, and the first diffusion sheet 22 and the liquid crystal panel. A first prism sheet 26 disposed between the plurality of prisms and arranged in a plurality of prisms in one direction to refract the light diffused in the diffusion sheet 22 to the front, the prism sheet 26 being disposed on the first prism sheet 26. The prism of the first prism sheet 26 is arranged in a direction perpendicular to the prism of the first prism sheet 26 The second prism sheet 28 for refracting the light again, and the second diffusion sheet 24 for supplying uniform light to the liquid crystal panel 40 by diffusing the light output from the second prism 28 once again. It consists of.

The first diffusion sheet 22 and the second diffusion sheet 24 diffuse the input light to make the light uniform, and the first prism sheet 26 and the second prism 28 have their prisms mutually different. Arranged vertically, the input light is refracted to the front side in the x-axis direction and the y-axis direction so that the light is input in front of the light, that is, perpendicular to the surface of the liquid crystal panel 40.

However, in the backlight device having the above structure, the first diffusion sheet 22, the second diffusion sheet 24, the first prism sheet 26, and the second prism sheet 28 are used as the optical sheet 20. Since it must be used, manufacturing costs increase. In addition, the optical sheet 20 causes the thickness of the backlight device to increase, thereby making it impossible to reduce the thickness of the liquid crystal display device.

An object of the present invention is to provide a backlight device and a liquid crystal display device having the same, which can reduce the manufacturing cost and reduce the thickness by removing the diffusion sheet.

Another object of the present invention is to provide a backlight device capable of improving light efficiency by arranging the prism of the upper and lower prism sheets facing downward and upper directions, respectively, and a liquid crystal display device having the same.

In order to achieve the above object, the backlight device according to the present invention comprises a lamp for emitting light; A light guide plate for guiding light emitted from the lamp; A first prism sheet having a plurality of prisms having a triangular cross section extending perpendicular to a traveling direction of light in the light guide plate; And a plurality of prisms having a triangular cross section, the second prism sheet extending perpendicularly to the first prism sheet, wherein the prism of the first prism sheet has a vertex disposed toward the light guide plate to totally reflect the incident light and to produce a second prism. The prism of the sheet is a vertex is arranged in the opposite direction to the light guide plate to refract the incident light, the prism of the first prism sheet is an acute angle of the vertex and the prism of the second prism sheet is an obtuse angle do.

The bottom of the prism of the first prism sheet has an angle of 60 ° or less, preferably 57 to 60 °, and the bottom of the prism of the second prism sheet has an angle of 45 ° or less, preferably 32 to 40 °.

The prism of the first prism sheet and the second prism sheet is made of an ultraviolet curable resin having a refractive index of 1.5 or more, and the ejection angle of light output from the light guide plate is 80 °.

In addition, the liquid crystal display apparatus according to the present invention is a liquid crystal panel in which an image is displayed; A lamp for emitting light; A light guide plate for guiding light emitted from the lamp; A first prism sheet having a plurality of prisms having a triangular cross section extending perpendicular to a traveling direction of light in the light guide plate; And a plurality of prisms having a triangular cross section, the second prism sheet extending perpendicularly to the first prism sheet, wherein the prism of the first prism sheet has a vertex disposed toward the light guide plate to totally reflect the incident light and to produce a second prism. The prism of the sheet has its vertices arranged in the opposite direction to the light guide plate to refract the incident light to the liquid crystal panel.The prism of the first prism sheet has an acute angle and the prism of the second prism sheet has an angle of vertex. It is characterized by an obtuse angle.

In the present invention, the following effects can be obtained.

First, in the present invention, not only the manufacturing cost is reduced by removing the backlight diffusion sheet, but also the thickness of the backlight device and the completed liquid crystal display device can be minimized.

Secondly, in the present invention, the prism of the first prism sheet having the acute angle of the vertex is directed toward the light guide plate, and the second prism sheet having the obtuse angle of the vertex has the prism facing the liquid crystal panel. In the 2 prism sheet, light is bent to supply light perpendicular to the surface of the liquid crystal panel, thereby greatly improving light efficiency.

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

3 is a diagram conceptually illustrating a path of light output from the light guide plate 113 after being guided to the light guide plate 113 in the liquid crystal display.

As shown in FIG. 3, the light emitted from the light source 111 in the backlight device of the liquid crystal display is incident on the light guide plate 113, and then totally reflected on the top and bottom surfaces of the light guide plate 113, and then at an angle greater than or equal to a threshold value. When incident to the upper surface of the furnace is output from the light guide plate 113 is supplied to the liquid crystal panel. In the case of using the wedge-shaped light guide plate 113 as shown in the drawing, the intensity according to the exit angle θ of the exit light is shown in FIG. 4.

As shown in FIG. 4, the emission angle θ of the light emitted from the light guide plate 113 is -80 ° ≦ θ ≦ 80 ° based on the normal of the upper surface of the light guide plate 113, but at most exit angles, The luminance is weak and the luminance is high between about 40 ° ≤θ≤80 °, and the emitted light is the highest at an angle (θ) of about 80 ° or more. This means that the outgoing light outputting the light guide plate 113 is mainly output at an angle of 80 ° or more.

On the other hand, the light output from the light guide plate 113 is refracted by the prism sheet (not shown) and is supplied perpendicular to the surface of the liquid crystal panel. However, as shown in FIG. 5, in order for the light guide plate 113 to be output and the light is refracted perpendicularly to the surface of the liquid crystal panel in the prism 126a of the prism sheet 126, a prism made of a UV resin having a refractive index of about 1.58. With respect to 126a, light must exit the light guide plate 113 at an angle of about 24 to 32 degrees (Snell's law).

However, as described above, since the light emitted from the light guide plate 113 is mostly emitted at an exit angle of 80 ° or more, the incident angle β of the light refracted by the prism 126a and incident on the liquid crystal panel does not become vertical. This may cause deterioration of the image quality of the device. In addition, when the exit angle θ of the light guide plate 113 is 80 ° or more, substantially the light emitted from the light guide plate 113 does not enter the prism sheet 126, but most of the light moves toward the side of the prism. That is, since the emitted light does not enter the prism sheet but proceeds to the side of the prism sheet, the emitted light does not supply to the liquid crystal panel but enters the side of the backlight device.

In the conventional backlight device, the diffusion sheet is provided between the light guide plate and the prism sheet to solve the above problems by scattering the light output from the light guide plate and changing the incident angle of the light incident on the prism sheet. In general, when the diffusion sheet is disposed on the light guide plate and the prism sheet to diffuse the light exiting the light guide plate, the brightness of the light is high between about 15 ° ≤θ≤45 °, especially at an angle (θ) of about 40 °. The brightness is the highest.

This angle is about 24 to 32 ° and a part of the angle of the light guide plate 113 of the outgoing light for exiting the light guide plate 113 and refracting light perpendicularly to the surface of the liquid crystal panel in the prism 126a of the prism sheet 126. Because of the overlap, the luminance of light incident on the liquid crystal panel is improved as compared with the structure without the diffusion sheet. However, even in such a structure, the brightness is the highest at an angle θ of about 40 degrees of the light diffused by the diffusion sheet, whereas the light is incident vertically to the liquid crystal panel at an angle of about 24 to 32 degrees. Light of the luminance is still not supplied vertically to the liquid crystal panel, so that the light efficiency is lowered.

The present invention is proposed to solve this problem. That is, in the present invention, the light having the maximum luminance, that is, the main exit light is vertically supplied to the liquid crystal panel so that the light efficiency is maximized. In addition, in the present invention, it is possible to reduce the manufacturing cost and minimize the thickness of the backlight device by providing light condensing properties by only two prism sheets without providing the diffusion sheet.

6 is a view showing a liquid crystal display device having a backlight device according to the present invention.

As shown in FIG. 6, the liquid crystal display device 201 according to the present invention includes a liquid crystal panel 240 and a backlight device 210. The backlight device 210 is positioned under the liquid crystal panel 240 to supply light to the liquid crystal panel 240.

The backlight device 210 is disposed under the liquid crystal panel 240 so that the light source 211 made of a lamp, the housing 212 for accommodating the light source 211, and the side surface contact the light source 211. A light guide plate 213 for supplying light input through the liquid crystal panel 240 and a reflector plate disposed under the light guide plate 213 to reflect light incident to the bottom of the light guide plate 213 to the liquid crystal panel 240. 217, a first prism sheet 226 disposed on an upper portion of the light guide plate 213 and having a plurality of prisms arranged in one direction to totally reflect the light emitted from the light guide plate 213, and the first prism sheet 226. The second prism sheet 228 is disposed on the second prism sheet 226 and arranged in a direction perpendicular to the prism of the first prism sheet 226 to refract the light refracted by the first prism sheet 226.

Although not shown in the drawings, a protective film for protecting the lower optical sheet may be further provided on the second prism sheet 228.

As shown in FIG. 7, the liquid crystal panel 240 includes a first substrate 250 and a second substrate 245 and a liquid crystal layer (not shown) therebetween. In the first substrate 250, a plurality of gate lines 256 and data lines 257 are arranged in a matrix to define a plurality of pixel regions P. In each pixel region P, a thin film transistor T ) And a pixel electrode 258 electrically connected to the thin film transistor T. Gate pads and data pads are formed at the ends of the gate line 256 and the data line 257 to connect the gate line 256 and the data line 257 with an external driving device to the gate line 256 and An external signal is input through the data line 225.

Although not shown in the drawing, the thin film transistor T is connected to the gate line 256, and includes a gate electrode through which the scan signal is input from the outside through the gate line 256, 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 258.

The second substrate 245 is formed in an image non-display area such as a gate line 256, a data line 257, or a thin film transistor T, in which no actual image is formed. Color consisting of a black matrix 246 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. Filter layer 247 is formed.

As described above, a liquid crystal layer (not shown) is formed between the configured first substrate 250 and the second substrate 245 to form the liquid crystal panel 240.

As the light source 211, a fluorescent lamp such as a CCFL (Cold Cathod Fluorouscent Lamp) is mainly used. A reflection layer is formed on an inner surface of the housing 212 in which the light source 211 is accommodated to reflect light emitted from the light source 211 to the light guide plate 213. In addition, the light source 211 may be formed on only one side of the light guide plate 213 as shown in FIG. 6, and the light emitted from the light source 211 may be formed on both sides of the light guide plate 213. It may be incident to the light guide plate 213 through both sides.

As the light source 211, 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 a backlight device, the color reproducibility is good and driving power can be reduced.

When such an LED is used as the light source 211 of the backlight device, when the light emitted from the LED is supplied to the liquid crystal panel, the monochromatic light is not directly supplied but the white light is supplied. The monochromatic light emitted from the light emitting device is converted into white light. Monochromatic light emitting devices and phosphors are used to make them, infrared light emitting devices and phosphors are used, or monochromatic light emitted from red (R), green (G) and blue (B) light emitting devices is mixed. That is, when using the LED as the light source 211 of the backlight device, a plurality of LEDs are arranged on the side of the light guide plate 213 to input white light or monochromatic light to the light guide plate 213.

The light guide plate 213 is made of polymethyl-methacrylate (PMMA). When light incident from one side or both sides is incident on the upper or lower surface of the light guide plate 213 at an angle less than or equal to a critical angle, the light is totally reflected by the light guide plate 213. When the light is processed from one side to the other side and the light is incident on the upper surface or the lower surface of the light guide plate 213 at an angle greater than the critical angle, the light is output to the outside and reflected by the reflecting plate 217 or incident on the first prism sheet 226.

In FIG. 6, as the light guide plate 213, a wedge shape in which the width thereof becomes narrower as the light guide plate 213 moves away from the region facing the light source 211, that is, in the traveling direction of the light, may be used. will be.

The prisms of the first prism sheet 226 and the second prism 228 are arranged perpendicular to each other, thereby refracting the input light toward the front side to improve the front luminance of the light. At this time, as shown in the figure, since the prism of the first prism sheet 226 and the second prism 228 is arranged vertically 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 240 perpendicularly.

The first prism sheet 226 and the second prism sheet 228 are ultraviolet curable resins having a refractive index of 1.5 or more on a base film mainly made of polyester (PET), polymethyl-methacrylate (PMMA), polycarbonate (PC), or the like. A regular prism is formed of a material such as PC to refrac the incident light, thereby reflecting and refracting the traveling direction of the light in the front direction. At this time, the prism is made of a triangular shape, such as a cross section, and the prism is arranged in a plurality of substantially isosceles triangular shapes extending from one side to the other side over the entire surface of the base film.

In FIG. 6, the prisms of the first prism sheet 226 and the second prism sheet 228 are illustrated in a triangular shape, but the prisms are not formed only in a triangular shape. Since the prism is for reflecting and refracting incident light, any shape capable of reflecting and refracting incident light may be possible. That is, various shapes such as hemispherical shape, polygonal shape such as square shape or pyramid, lens shape, etc. will be possible. In this sense the term prism may not be appropriate. However, the use of such terms is for convenience of description and does not imply any particular form. Accordingly, the term prism used in the detailed description does not refer to a specific shape, but refers to a specific shape formed on the first prism sheet 226 and the second prism sheet 228 that reflects and refracts incident light. .

In addition, although not shown in the drawings, the prism of the first prism sheet 226 and the second prism sheet 228 may be formed in a polygonal shape or at least one surface of a triangular shape or a lens shape. In addition, the base films of the first prism sheet 226 and the second prism sheet 228 include diffusing materials such as PMMA, poly-n-butylmethacrylate (PBMA), silica, PC, etc. Can be spawned.

At this time, an isosceles triangle image of the prism of the first prism sheet 226 is output from the lamp 211 and extends in a direction perpendicular to the traveling direction of the light incident on the light guide plate 213 (that is, the x-axis direction). The isosceles triangle image of the prism of the sheet 228 extends in the direction perpendicular to the extension direction of the isosceles triangle of the prism of the first prism sheet 226 (that is, the direction perpendicular to the traveling direction of the light).

The prism of the first prism sheet 226 is arranged so that its vertex is facing the surface of the light guide plate 213 (ie, the vertex is arranged downward) and the prism of the second prism sheet 228 has its vertex It is arranged to face the liquid crystal panel 240 (that is, the vertex is arranged toward the upper direction). Conventionally, the vertices of the first prism sheet and the second prism sheet are all disposed toward the liquid crystal panel, whereas in the present invention, the prism of the first prism sheet 226 and the prism of the second prism sheet 228 are mutually Facing in the opposite direction.

At this time, the vertex angle of the prism of the first prism sheet 226 is an acute angle of 90 degrees or less and the vertex angle of the prism of the second prism sheet 228 is an obtuse angle of 90 degrees or more.

As described above, the prism of the first prism sheet 226 is arranged toward the light guide plate 213 so as to totally reflect the light emitted from the light guide plate 213, particularly the light emitted at an exit angle of 80 ° or more, so that the liquid crystal panel ( 240 to be incident in the vertical direction, which will be described in detail as follows.

FIG. 8A is a diagram conceptually illustrating optical refraction by the first prism sheet 226 in the backlight device according to the present invention.

As shown in FIG. 8A, the light output from the lamp 211 and propagated from the light guide plate 213 is emitted at an exit angle θ of about 80 ° with respect to the normal of the light guide plate 213, and then the first prism. Entered into sheet 226. In this case, since the vertices of the prism are disposed toward the light guide plate 213, the light emitted from the light guide plate 213 is directly incident on the prism of the first prism sheet 226. The incident light is totally reflected at the prism 226a. Light traveling between two media with different refractive indices is totally reflected according to Snell's law. In the conventional backlight device, the light output from the light guide plate is input to the first prism sheet and refracted to be supplied to the liquid crystal panel. However, in the present invention, the light output from the light guide plate is input to the first prism sheet and totally reflected to the liquid crystal panel. Will be.

In the present invention, when light is emitted at an exit angle θ of about 80 ° with respect to the normal of the light guide plate 213, the bottom angle α1 of the prism is formed to be 60 ° or less, preferably 57 to 60 °. As described above, as the bottom angle α1 of the prism is formed at 57 to 60 °, light totally reflected by the prism is incident perpendicularly to the liquid crystal panel.

When light is incident on the liquid crystal panel, in order to maximize the brightness, the incident angle to the liquid crystal panel is most preferably -10 to 10 degrees with respect to the normal of the liquid crystal panel (that is, 80 to 100 degrees with respect to the surface of the liquid crystal panel). Do. Of course, the most ideal angle of incidence is 0 °, but in reality it is difficult to meet this angle, and since the high quality image can be realized even if light is incident at -10 to 10 °, the angle of incidence of light to the liquid crystal panel is It is preferable to set it as -10-10 degrees with respect to a normal line.

In the present invention, by forming the prism 226a of the first prism sheet 226 at an angle α1 of the triangular base at 57 to 60 °, the light emitted from the light guide plate 213 at an angle of about 80 ° is generated by Snell. By the law, total reflection from the prism 226a of the first prism sheet 226 is supplied to the liquid crystal panel at an angle of -10 to 10 ° with respect to the normal line of the liquid crystal panel.

9A and 9B are diagrams showing a light distribution diagram of output light output from a first prism sheet in a conventional backlight device, and a diagram showing a light distribution diagram of output light output from a first prism sheet of a backlight device according to the present invention.

As shown in FIG. 9A, in the conventional backlight device having two diffusion sheets and two prism sheets, output light is uniformly distributed at 0 to 90 ° with respect to the normal of the surface of the liquid crystal panel. In the present invention, it can be seen that light is distributed at about 0 ° with respect to the normal of the surface of the liquid crystal panel. Therefore, conventionally, light is not incident vertically with respect to the surface of the liquid crystal panel, but is uniformly incident at all angles, so that light efficiency is lowered. However, in the present invention to which the first prism sheet 226 is applied, light is mainly used for Since it is incident perpendicularly to the surface, the light efficiency is improved.

8B is a view conceptually illustrating the refraction of light by the second prism sheet 228 in the backlight device according to the present invention.

As shown in FIG. 8B, light emitted from the light guide plate 213 and totally reflected from the first prism sheet 226 is incident on the second prism sheet 228, and the prism 228a of the second prism sheet 228 is exposed. Is refracted by

As shown in FIG. 6, since the prism of the first prism sheet 226 and the prism of the second prism sheet 228 extend perpendicular to each other, the light is refracted in the vertical direction. That is, the first prism sheet 226 refracts light in the y-axis direction, that is, the light traveling direction in the light guide plate 213, and the second prism sheet 228 refracts light in the x-direction so that the light is liquid. Make sure to feed the panel vertically in the x, y-axis direction.

As shown in FIG. 8B, the prism of the second prism sheet 228 forms an obtuse angle at the vertex. Accordingly, in the present invention, the prism of the second prism sheet 228 is formed at an angle α2 of the triangular bottom surface of about 45 degrees or less, preferably 32 to 40 degrees.

When the bottom angle α2 of the second prism sheet 228 is 45 ° or more as in the related art, light is totally reflected by the first prism sheet 226 so that light is substantially perpendicular to the surface of the second prism sheet 228. After being incident, light is totally reflected by the prism and is incident again to the light guide plate 213. In addition, when light is incident at a predetermined angle with the surface of the second prism sheet 228, the light is refracted toward the side rather than the front side of the liquid crystal panel, thereby degrading the light efficiency.

However, when the bottom angle α2 of the prism of the second prism sheet 228 is formed to be about 45 ° or less, preferably 32 to 40 ° as in the present invention, light incident on the second prism sheet 228 is incident. It is refracted toward the front of the liquid crystal panel and is incident almost perpendicularly to the surface of the liquid crystal panel.

10A is a graph of light distribution and emission angle of output light when using a second prism sheet used in a conventional backlight device, and FIG. 10B is a light distribution diagram of output light when using a second prism sheet according to the present invention. This is a graph of the exit angle luminance.

As shown in FIG. 10A, when the second prism sheet of the conventional backlight is used, the light has the highest luminance at about −80 ° and 80 ° with respect to the normal direction of the surface of the liquid crystal panel, and the second highest at 0 °. That is, the light refracted by the second prism mostly proceeds in the -80 ° and 80 ° directions, and the remaining light travels in the 0 ° direction. However, about -80 degrees and 80 degrees directions with respect to the normal line direction of the surface of a liquid crystal panel are not a front direction but a side direction. Therefore, when the second prism of the conventional backlight is used, most of the light is not supplied to the liquid crystal panel but proceeds to the side of the backlight, thereby reducing the light efficiency.

On the other hand, as shown in FIG. 10B, in the present invention, when the bottom angle α2 of the prism of the second prism sheet 228 is formed to about 45 ° or less (36 ° in the drawing), the luminance is 0. It is the highest near, and close to zero in other areas. This means that most of the light refracted by the second prism sheet 228 is supplied at an angle of 0 ° with respect to the normal direction of the surface of the liquid crystal panel, and as a result, the light efficiency can be significantly improved as compared with the conventional art.

As described above, in the present invention, the diffusion sheet is removed and the two prism sheets are arranged so that the prism faces downward and upper, respectively, so that the light output from the light guide plate is totally reflected by the first prism sheet and refracted by the second prism sheet. By doing so, light perpendicular to the surface is supplied to the liquid crystal panel.

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. For example, the bottom angles of the prism of the first prism sheet and the prism of the second prism sheet may be the same or different on both sides. Also, the height or width of the prism may be set differently as needed. In other words, other examples or modifications of the present invention can be easily made by anyone who is engaged in the technical field to which the present invention belongs, the liquid crystal display device using the basic concept of the present invention.

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 conventional liquid crystal display device.

3 is a conceptual diagram illustrating a path of light output to a light guide plate of a backlight device;

4 is a diagram illustrating a relationship between an emission angle and luminance of light output from a light guide plate;

FIG. 5 is a conceptual diagram illustrating that a path of light output to the light guide plate is changed by a prism sheet in a backlight device; FIG.

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

7 is a view showing the structure of a liquid crystal panel of the liquid crystal display device according to the present invention;

8A and 8B are views showing total reflection and refraction of light by the first prism sheet and the second prism sheet in the backlight device according to the present invention, respectively.

9A and 9B are diagrams showing a light distribution diagram of output light output from a first prism sheet in a conventional backlight device, and a diagram showing a light distribution diagram of output light output from a first prism sheet of a backlight device according to the present invention.

10A is a graph of light distribution and emission angle luminance of output light when the second prism sheet used in the conventional backlight device is used, respectively.

10B is a graph of light distribution and emission angle luminance of output light when the second prism sheet according to the present invention is used.

Claims (11)

A lamp for emitting light; A light guide plate for guiding light emitted from the lamp; A first prism sheet having a plurality of prisms having a triangular cross section extending perpendicular to a traveling direction of light in the light guide plate; And A plurality of prisms having a triangular cross section is composed of a second prism sheet extending perpendicular to the first prism sheet, The prism of the first prism sheet has a vertex disposed toward the light guide plate to totally reflect the incident light, and the prism of the second prism sheet has a vertex disposed toward the opposite direction to the light guide plate to refract the incident light, and the prism of the first prism sheet The prism of the vertex is an acute angle and the prism of the second prism sheet is a backlight device, characterized in that the angle of the vertex obtuse. The backlight device of claim 1, wherein an angle of a bottom surface of the prism of the first prism sheet is 60 ° or less. The backlight device of claim 2, wherein an angle of a bottom surface of the prism of the first prism sheet is 57 to 60 °. The backlight device of claim 1, wherein an angle of a bottom surface of the prism of the second prism sheet is 45 ° or less. The backlight device of claim 1, wherein an angle of a bottom surface of the prism of the second prism sheet is 32 to 40 °. The backlight device according to claim 1, wherein the prisms of the first prism sheet and the second prism sheet are made of an ultraviolet curable resin having a refractive index of 1.5 or more. The backlight device of claim 1, wherein a pre-emergence angle of light output from the light guide plate is 80 °. The backlight device of claim 1, wherein the prism of the first prism sheet and the second prism sheet is made of an ultraviolet curable resin or a polycarbonate (PC) having a refractive index of 1.5 or more. The method of claim 1, wherein the first prism sheet and the second prism sheet further comprise a base film formed of polyester (PET), polymethyl-methacrylate (PMMA), or polycarbonate (PC). Backlight device. The backlight device of claim 9, wherein the base film comprises a diffusion material. A liquid crystal panel on which an image is displayed; A lamp for emitting light; A light guide plate for guiding light emitted from the lamp; A first prism sheet having a plurality of prisms having a triangular cross section extending perpendicular to a traveling direction of light in the light guide plate; And A plurality of prisms having a triangular cross section is composed of a second prism sheet extending perpendicular to the first prism sheet, The prism of the first prism sheet has a vertex disposed toward the light guide plate to totally reflect the incident light, and the prism of the second prism sheet has a vertex disposed toward the opposite direction to the light guide plate to refract the incident light and supply it to the liquid crystal panel. The prism of the first prism sheet has an acute angle of the vertex, and the prism of the second prism sheet has an obtuse angle of the vertex.
KR1020090050117A 2009-06-05 2009-06-05 Back light unit and liquid crystal display device having thereof KR20100131300A (en)

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102736144A (en) * 2011-04-12 2012-10-17 惠和株式会社 Light diffusion sheet, optical unit, backlight unit and liquid crystal display device
US9080748B2 (en) 2012-11-20 2015-07-14 Samsung Electronics Co., Ltd. Display panel having improved light-use efficiency, display device including the display panel, and method of manufacturing the display panel
CN114442368A (en) * 2020-11-06 2022-05-06 株式会社Lms Backlight unit

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102736144A (en) * 2011-04-12 2012-10-17 惠和株式会社 Light diffusion sheet, optical unit, backlight unit and liquid crystal display device
KR101362112B1 (en) * 2011-04-12 2014-02-12 케이와 인코포레이티드 Optical sheet, optical unit, backlight unit and liquid crystal display device
US9080748B2 (en) 2012-11-20 2015-07-14 Samsung Electronics Co., Ltd. Display panel having improved light-use efficiency, display device including the display panel, and method of manufacturing the display panel
CN114442368A (en) * 2020-11-06 2022-05-06 株式会社Lms Backlight unit
CN114442368B (en) * 2020-11-06 2024-03-29 株式会社Lms Backlight unit

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