KR101189134B1 - LED and Liquid Crystal Display device using thereof - Google Patents

Abstract

The present invention relates to an LED and a liquid crystal display using the same. More particularly, the present invention relates to an LED having a reflective polarization function and a liquid crystal display having an improved light efficiency by using the same as a light source.

Specifically, the present invention is an LED chip that emits light forward; A lens covering the LED chip; Provided is an LED including a wire grid interposed into the lens in front of the LED chip, and a liquid crystal display including a liquid crystal panel disposed in front of at least one of the LEDs.

As a result, the LED according to the present invention repeats the regeneration by selective transmission and reflection of light therein, and as a result, it is possible to take a linear polarization of a specific horizontal component that reaches almost the majority of the light emitted from the LED chip. have. Therefore, when this is used as a light source of the liquid crystal display device, the light efficiency is greatly improved.

Description

LED and liquid crystal display device using same

1A and 1B are schematic diagrams showing optical characteristics of a general liquid crystal display device, respectively.

Figure 2 is a schematic diagram showing the optical characteristics of a typical wire-dried polarizing plate.

3 is a schematic exploded perspective view of a general liquid crystal display.

Figure 4 is a cross-sectional perspective view of the LED according to the present invention.

5 is a schematic view showing the polarization characteristics of the LED according to the present invention.

6 is a schematic exploded perspective view of a liquid crystal display according to the present invention.

<Description of the symbols for the main parts of the drawings>

100: LED 102: LED chip

104: lens 106: heat radiation slug

108: reflective surface 110: case

112 wire 114116 negative and positive lead

120: wire grid 150: liquid crystal panel

152, 154: first and second substrate 156: liquid crystal layer

162,164: first and second polarizer 170: LED backlight

176: optical sheet 174: reflective sheet

180: PCB

The present invention relates to a light emitting diode (LED) and a liquid crystal display device using the same. More specifically, an LED having a reflective polarization function and a liquid crystal display having greatly improved light efficiency by using the same as a light source. Relates to a device.

In line with the recent information age, the display field for displaying images through electrical signals has also been rapidly developed. Accordingly, a flat panel display device (FPD) having advantages of thinning, light weight, and low power consumption has been developed. Liquid Crystal Display Device (LCD), Plasma Display Panel Device (PDP), Electroluminescence Display Device (ELD), Field Emission Display Device (FED) It is introduced to replace the existing cathode ray tube (CRT) quickly.

Among them, the liquid crystal display device is excellent in moving image display and has a high contrast ratio, which is currently being used most actively in the fields of monitors and TVs, which are used for optical anisotropy, which is inherent in liquid crystals. The principle of image implementation using polarization is known. As is well known, liquid crystals have a thin and long molecular structure and optical anisotropy having directionality in the array, and polarization properties in which the molecular arrangement direction changes depending on the size when placed in an electric field. It is

In the liquid crystal display device, a liquid crystal panel interposed between two substrates having transparent field generating electrodes formed on opposite surfaces thereof and then bonded to the surface thereof and a backlight for supplying light from the rear surface thereof. A change in the direction of arrangement of the liquid crystal molecules by an electric field between two field generating electrodes of the liquid crystal panel, generating a difference in transmittance, and projecting the difference in transmittance of the liquid crystal panel to the outside using light emitted from the backlight. Is displayed.

In recent years, the active matrix type, which arranges pixels, which are the basic units of image expression, on a liquid crystal panel in a matrix and individually controls each of them with a switching element such as a thin film transistor (TFT) 1A and 1B are schematic diagrams showing optical characteristics according to operating states of a general liquid crystal display device, and a case where a TN (Twisted Nematic) mode liquid crystal is used for convenience. .

As can be seen, a general liquid crystal display device includes a liquid crystal panel 10 and a backlight 20 for supplying light from a rear surface thereof, wherein the liquid crystal panel 10 includes first and second surfaces facing each other with the liquid crystal layer 6 interposed therebetween. And first and second polarizers 12 and 14 attached to the second substrates 2 and 4 and outer surfaces of the first and second substrates 2 and 4, respectively.

At this time, the inner surface of the first substrate 2 is provided with a plurality of pixels mounted with a transparent pixel electrode and a thin film transistor for controlling the liquid crystal driving voltage transmitted to each of the pixel electrodes on and off, and the second substrate ( 4) The inner surface is provided with a color filter and a common electrode for color realization. In addition, the liquid crystal layer 6 interposed between the two substrates 2 and 4 is a TN mode, and in the voltage off state, the long axis direction of the molecules is kept in parallel with the two substrates 2 and 4. An alignment state twisted at an azimuth angle of 90 degrees from the first substrate 2 to the second substrate 4 is shown, and the polarization axes of the first and second polarizing plates 12 and 14 are perpendicular to each other.

The backlight 20 supplies scattered light close to natural light to the liquid crystal panel 10.

Accordingly, when the potential difference between the pixel electrode and the common electrode is lower than the threshold voltage of the liquid crystal molecules, the scattered light emitted from the backlight 20 is discharged by the first polarizing plate 12 as shown in FIG. 1A. Only linearly polarized light parallel to the polarization axis thereof is transmitted and the remainder is absorbed, and is rotated by 90 ° along its azimuth angle while passing through the liquid crystal layer 6, thereby passing through the second polarizing plate 14 to display normal white. do. Next, when the potential difference between the pixel electrode and the common electrode is greater than or equal to the threshold voltage of the liquid crystal molecules, the long axis of the liquid crystal molecules is arranged perpendicular to both substrates 2 and 4 as shown in FIG. Since the optical rotatory power of 90 ° is lost, linearly polarized light transmitted through the first polarizing plate 12 is blocked by the second polarizing plate 14 to display black.

In this case, various linearly polarized light is mixed in the scattered light emitted from the backlight 20, but for convenience, only the vertical component perpendicular to the horizontal component parallel to the polarization axis thereof based on an arbitrary first polarizing plate 12 is considered. The light emitted from the light emitting device is lost by about 50% while passing through the first polarizing plate 12 and is absorbed and reflected during the process of passing through the liquid crystal layer 6 including the first and second substrates 2 and 4. Again part is lost, indicating a very weak disadvantage in terms of brightness.

Accordingly, a reflection type polarizing plate that reflects linear polarization that does not pass through the polarizing plate and improves light efficiency by regeneration has been introduced. A representative example thereof is a wire grid polarizer.

2 is a schematic view for explaining the optical characteristics of the general wire grid polarizing plate 30, which is a wire grid 34 made of a fine metal pattern is arranged in parallel on the insulating substrate 32, Under the premise that the spacing or period between the wire grids 34 is sufficiently smaller than the wavelength of the incident light, linearly polarized light parallel to the arrangement direction thereof is transmitted, but the rest is reflected.

Accordingly, when the reflective sheet 42 or the like is arranged to be parallel to the wire grid polarizer 30 with the light source 40 interposed therebetween, the linearly polarized light reflected from the wire grid polarizer 30, and optionally a vertical component, is formed by the reflective sheet 42. The reflection is again reproduced as scattered light in which the vertical component and the horizontal component are mixed, and are incident on the wire grid polarizing plate 30, and the selective transmission and reflection by the polarization characteristic of the light are constantly repeated.

As a result, light loss can be minimized by using the wire grid polarizer 30.

On the other hand, as a light source of a backlight for a liquid crystal display device, a cold cathode fluorescent lamp (CCFL) or an external electrode fluorescent lamp (EEFL) is used. Therefore, it is classified into a side light type and a direct type, and the former light metering type separates light of a light source emitted from at least one side of the rear of the liquid crystal panel with a light guide panel (LGP). While refracting the light into the liquid crystal panel, the latter direct type supplies light by directly placing a plurality of light sources facing the rear of the liquid crystal panel.

3 is a schematic exploded perspective view of a general direct type liquid crystal display device using the wire grid polarizer 30 as described above, and the same reference numerals are given to the same parts having the same role as the backlight 50. ) Includes a plurality of fluorescent lamps 52 arranged on an arbitrary plane facing the rear surface of the liquid crystal panel 10 to emit light forward, and interposed between the fluorescent lamps 52 and a diffusion sheet and a light collecting sheet. A plurality of optical sheets 56 and a reflective lamp 54 facing the liquid crystal panel 10 with the fluorescent lamp 52 interposed therebetween, wherein the plurality of optical sheets 56 and the liquid crystal panel ( 10) a wire grid polarizing plate 30 is interposed therebetween.

However, the above-described general liquid crystal display device exhibits some problems, one of which is that the light efficiency of the wire grid polarizer 30 does not meet expectations.

More specifically, since the general wire grid polarizing plate 30 may not serve as a perfect transmission and reflector, a part of the linear polarization parallel to the polarization axis thereof is reflected due to surface reflection and also transmits a part of the vertical linear polarization. Accordingly, the performance of the wire grid polarizing plate 30 is generally expressed by a polarization extinction ratio and transmittance defined by the following relationship, for convenience, a horizontal component parallel to the polarization axis of the wire grid polarizing plate 30 and a vertical perpendicular to the polarization axis of the wire grid polarizing plate. Considering only linear polarization of the components,

Polarization extinction ratio = (Si / St) | pi,

Transmittance = (Pt / Pi) | si

In this case, Si / St represents an optical power ratio with respect to the vertical component (Si) of the light incident on the wire grid polarizer 30 and the part (St) of the vertical component transmitted through the wire grid polarizer 30. , Pi / Pt represents the optical power ratio for the horizontal component (Pi) of the light incident on the wire grid polarizer 30 and the portion (Pt) of the horizontal component transmitted through the wire-grid polarizer 30, respectively, The performance of the grid polarizer 30 is closely related to the optical power.

In addition, the optical power is a value directly affected by the traveling distance and the type of the medium. In the conventional LCD, the wire grid polarizer 30 maintains a constant distance from the fluorescent lamp 52, and a plurality of optical fibers therebetween. As the sheet 56, a light collecting sheet such as a diffusion sheet or a prism sheet is interposed.

Therefore, the light emitted from the first fluorescent lamp 52 is incident to the wire grid polarizer 30, and is accompanied with continuous light loss during the regeneration process by the reflection between the wire grid polarizer 30 and the reflective sheet 54. As a result, it is difficult to expect as much light efficiency as desired.

Accordingly, the present invention has been made to solve the above problems, and an object of the present invention is to present a concrete method for greatly improving the light efficiency of a liquid crystal display device. Recently, LED (Light Emitting Diode) has been increasingly used as an alternative light source for fluorescent lamps to achieve color reproduction and brightness improvement without using toxic mercury (Ag). The backlight is especially called the LED backlight.

Accordingly, the present invention is to provide an LED and a liquid crystal display using the same as a specific method for achieving the above object, an environmentally friendly, inherent advantages of color reproducibility and brightness, and greatly improved light efficiency as a light source for a liquid crystal display. .

In order to achieve the above object, the present invention and the LED chip to shine forward; A lens covering the LED chip; It provides an LED comprising a wire grid interposed into the lens in front of the LED chip.

In this case, the lens has a light transmittance of 90% or more, and the wire grid is characterized in that the intervening in the direction of terminating the lens, the wire grid is a plurality of parallel to each other and arranged to form a shape. The plurality of wire grids may be formed of a fine metal pattern of one material selected from aluminum (Al), silver (Ag), and chromium (Cr), and the spacing between the wire grids may be 200 nm or less. . In this case, the LED chip is mounted and the heat dissipating slug to provide a reflective surface; A case surrounding the heat dissipation slug; And a positive electrode and a negative electrode lead electrically connected to the LED chip and exposed to the outside of the case.

In another aspect, the present invention provides a liquid crystal display device using the LED according to the above description, comprising a liquid crystal panel disposed in front of the at least one LED.

At least one PCB characterized in that it further comprises a reflective sheet parallel to the liquid crystal panel with the at least one LED therebetween, at least one PCB on which the at least one LED is mounted; The reflective sheet further includes a through hole penetrating the reflective sheet to have a one-to-one correspondence with the plurality of LEDs, wherein the reflective sheet exposes the LED and covers the PCB. In addition, it characterized in that it further comprises a plurality of optical sheets interposed between the LED and the liquid crystal panel.

In addition, the liquid crystal panel and the first substrate of the LED side; A second substrate facing the front side of the first substrate; And a liquid crystal layer positioned between the first and second substrates, wherein the liquid crystal layer is in a TN mode and is attached to an outer surface of the first substrate facing the LEDs, the liquid crystal layer being in the same direction as the wire grid. A first polarizing plate having a polarization axis; And a second polarizing plate attached to an outer surface of the second substrate on the front side and having a polarization axis in a direction orthogonal to the first polarizing plate. Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. .

4 is a cross-sectional structure diagram of the LED 100 according to the present invention. The LED chip 102 emits light, the lens 104 covering the lens 104, and the lens to maintain a certain distance from the LED chip 102. 104 includes a wire grid 120 interposed therein.

More specifically, first, the LED chip 102 is composed of a forward junction of a P-type semiconductor that provides a positive hole as a substantially light emitting portion and an n-type semiconductor that provides an electron.

In addition, the LED chip 102 is seated on the heat dissipation slug 106, which is made of metal as a part that conducts and discharges the high temperature heat accompanying the light emission of the LED chip 102 to the outside. As the upper surface on which the 102 is seated, a reflective surface 108 having high reflection efficiency is defined.

Next, the heat dissipation slug 106 is bordered by a case 110 serving as a housing, and the case 110 has a cathode and an anode lead electrically connected to each other through an LED chip 102 and a wire 112. 114 and 116 are provided, each of which is exposed to the outside.

The upper part of the case 110 covers and protects the reflecting surface 108 and the wire 112 of the heat dissipation slug 106 including the LED chip 102, and at the same time, the injection from the LED chip 102. There is a lens 104 that controls the angle of light, which can take various forms depending on the purpose.

In this case, in particular, the above-described lens 104 is interposed with a wire grid 120 to maintain a constant distance from the LED 102 chip, which consists of a plurality of fine metal patterns arranged in parallel with each other to terminate the lens 104. It may be buried, and as the material, aluminum (Al), silver (Ag), chromium (Cr), etc., which have high reflection efficiency, may be used, and red and green including blue color may be used. In order to obtain a high light output ratio, that is, a high extinction ratio (ER), with respect to the three primary colors of Hg), the interval including the width of the metal pattern is preferably 200 nm or less.

To this end, the wire grid 120 may be implemented by a photolithography process which is well known as a micropattern implementation technique.

On the other hand, the LED 100 according to the present invention having the above-described structure, the wire grid 120 placed on the light irradiation path of the LED chip 102 which is a substantially light source and the LED chip 102 between the wire grid 120. By providing the reflective surface 108 of the heat dissipating slug 106 in parallel with (), the repetition of the light by selective transmission and reflection of the light is repeated, and as a result, the light efficiency is greatly improved.

That is, Figure 5 is a schematic diagram showing the optical characteristics of the LED 100 according to the present invention, the reflecting surface 108 and the wire grid 120 of the LED chip 102 and the lens 104 and the heat radiation slug 106 ) Is a cross-sectional view showing only a part of the same. In the following description, only the horizontal component parallel to the arrangement direction of the wire grid 120 and the vertical component perpendicular to the arrangement direction of the wire grid 120 are considered among the polarization components of the light emitted from the LED chip 102 for convenience.

Accordingly, the light emitted from the first LED chip 102 is incident to the wire grid 120, and thus linearly polarized light parallel to the arrangement direction of the wire grid 120, optionally horizontal, is transmitted to the outside of the lens 104. Although linear polarization, which is perpendicular to the arrangement direction of the wire grid 120, the vertical component is reflected. At this time, the vertical component reflected by the wire grid 120 is reproduced as scattered light in which the vertical component and the horizontal component are mixed again during the reflection by the reflecting surface 108 of the heat radiation slug 106, and the horizontal component thereof Through the grid 120 and the vertical component is reflected again, the LED 100 according to the present invention is continuously repeated by the selective transmission and reflection according to the polarization characteristics of the light therein.

In addition, any absorbing optical configuration is formed between the LED chip 102 and the reflective surface 108 of the heat dissipation slug 106 including the wire grid 120 where the regeneration process is performed by selective transmission and reflection according to the polarization characteristic of the light. Therefore, in front of the LED 100, it is possible to take a linear polarization of the horizontal component to almost the majority of the light emitted from the LED chip 102. In this case, in order to obtain more improved light efficiency, the lens 104 of the LED 100 preferably exhibits a high transmittance in the range of 90% or more.

Therefore, when using the LED 100 according to the present invention as a light source of the liquid crystal display device can greatly improve the light efficiency, Figure 6 is a simplified exploded perspective view of the liquid crystal display device using the LED 100 as a specific example. .

As can be seen, the liquid crystal display according to the present invention includes a liquid crystal panel 150 and an LED backlight 170 positioned on a rear surface thereof, and the dual LED backlight 170 includes an LED 100 used as a light source. The structure of a direct type | mold is shown.

First, the liquid crystal panel 150 is composed of the first and second substrates 152 and 154 bonded to each other with the liquid crystal layer 156 interposed therebetween. On the inner surface of the first substrate 152 called a substrate or array substrate, a plurality of gate lines and data lines intersect to define pixels, and a thin film transistor is provided at each intersection to mount the transparent pixel electrodes mounted on each pixel. And one-to-one correspondence is connected. In addition, an RGB color filter corresponding to each pixel is formed on the inner surface of the second substrate 154 called an upper substrate or a color filter substrate. A black matrix covering non-display elements such as transistors is provided, and the transparent common electrode covers them.

In addition, a liquid crystal panel driving circuit is connected to the liquid crystal panel, which is a gate driving circuit which scans an on / off signal of a thin film transistor to a gate line, and a data driving circuit which transmits an image signal to a data line. It is divided into two and positioned to two adjacent edges of the liquid crystal panel.

Accordingly, in the liquid crystal panel 150 having the above-described structure, when the thin film transistor selected for each gate line is turned on by the on / off signal of the gate driver circuit that is scanned and transmitted, the signal voltage of the data driver circuit is changed through the data line. The liquid crystal molecules are transferred to the electrodes, and thus the arrangement direction of the liquid crystal molecules is changed by the vertical electric field between the pixel electrode and the common electrode, thereby indicating a difference in transmittance.

In this case, the liquid crystal layer 156 interposed between the substrates 152 and 154 may be in a TN mode.

Next, the LED backlight 170 is provided on a rear surface of the liquid crystal panel 150 so that the transmittance difference represented by the liquid crystal panel 150 may be projected to the outside. On one plane of the LED 100 according to the invention is arranged.

In this case, the LED 100 according to the present invention has a shape in which the wire grid 120 is interposed into the lens 104 in front of the LED chip 102 seated on the reflective surface 108 of the heat dissipation slug 106 as described above. In addition, the optical efficiency can be greatly improved through selective transmission and regeneration by reflection according to the polarization characteristics of light appearing between the reflective surface 108 and the wire grid 120 (see FIGS. 4 and 5).

On the other hand, in the liquid crystal display device according to the present invention, when the liquid crystal layer 156 of the liquid crystal panel 150 is arbitrarily in the TN mode, the arrangement direction of the wire grid 120 of the LED 100 on the outer surface of the first substrate 152 The first polarizer 162 having the same polarization axis as that of the second polarizer 162 may be attached, and the second polarizer 164 having the polarization axis perpendicular to the first polarizer 162 may be attached to the outer surface of the second substrate 154.

In addition, the liquid crystal display according to the present invention may further include a variety of optical members according to the purpose, specifically, a plurality of LEDs 100 can be arranged on the reflective sheet 174 to reduce the light loss, these A plurality of optical sheets may be interposed between the LED 100 and the liquid crystal panel 150.

In addition, the LED 100 according to the present invention can implement white light by color mixing by arranging RGB LEDs emitting red, green, and blue according to a predetermined rule, and then lighting them all at once. In this case, the RGB LEDs are arranged by unit array. The LED array mounted on the PCB 180 can be configured, and the reflective sheet 174 exposes only the LED 100 in the liquid crystal panel direction by penetrating through holes corresponding to each LED 100 one-to-one. The PCB 180 may represent a covering shape.

As described above, the LED according to the present invention repeats the reproduction by the selective transmission and reflection of light therein, and particularly in the lens of the LED in which the selective transmission and reflection of the light is repeated as described above. Unlike other conventional absorbent optical components such as optical sheets are excluded, high light efficiency can be obtained.

As a result, there is an advantage in that it can take a linear polarization of a specific horizontal component that reaches almost the majority of the light emitted from the LED chip.

In addition, by interposing a wire grid inside the LED, sufficient color mixing space can be secured in the LED backlight. Therefore, when the LED according to the present invention is used as a light source of a liquid crystal display device, the light efficiency and color reproducibility are greatly improved. have.

Claims (12)

An LED chip emitting light forwardly; A lens covering the LED chip; A wire grid interposed into the lens in front of the LED chip LED comprising a. The method of claim 1, The lens has a light transmittance of 90% or more LED. The method of claim 1, The wire grid LED interposed in the direction of terminating the lens. The method of claim 1, The wire grids are formed in a plurality of parallel spaced spaced apart from each other, wherein each of the plurality of wire grids is made of a fine metal pattern of a material selected from aluminum (Al), silver (Ag), chromium (Cr). Characteristic LED. 5. The method of claim 4, An LED having a spacing between adjacent wire grids of 200 nm or less. The method of claim 1, A heat dissipation slug on which the LED chip is seated and providing a reflective surface; A case surrounding the heat dissipation slug; Anode and cathode lead electrically connected to the LED chip and exposed to the outside of the case LED further comprising. A liquid crystal display device using the LED according to any one of claims 1 to 6, Liquid crystal panel disposed in front of the at least one LED Liquid crystal display comprising a. 8. The method of claim 7, Reflective sheet parallel to the liquid crystal panel with the at least one LED interposed therebetween Liquid crystal display further comprising. 9. The method of claim 8, At least one PCB on which the at least one LED is mounted; A through hole penetrated through the reflective sheet in a one-to-one correspondence with the at least one LED. The liquid crystal display device further comprising: the reflective sheet covers the PCB while exposing the LED. 8. The method of claim 7, A plurality of optical sheets interposed between the at least one LED and the liquid crystal panel Liquid crystal display further comprising. 8. The method of claim 7, The liquid crystal panel includes a first substrate on the LED side; A second substrate facing the front side of the first substrate; A liquid crystal layer positioned between the first and second substrates Liquid crystal display further comprising. 12. The method of claim 11, The liquid crystal layer is in TN mode, A first polarizer attached to an outer surface of the first substrate facing the LED and having a polarization axis in the same direction as the wire grid; A first polarizing plate attached to an outer surface of the second substrate on the front side and having a polarization axis in a direction orthogonal to the second polarizing plate; Liquid crystal display further comprising.

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