KR20030044238A - Liquid crystal display - Google Patents

Abstract

PURPOSE: A liquid crystal display device is provided to integrate a back light with an LCD by employing an organic EL unit as the back light, thereby reducing the thickness of the device and minimizing the device. CONSTITUTION: A liquid crystal display device includes upper and lower substrates(32,34) facing each other, an LCD panel(50) formed below the upper substrate and displaying images, an organic EL(electroluminescence) part(70) interposed between the lower substrate and the LCD panel for generating light, and a quarter wave plate and a polarization plate stacked on the outside of the upper substrate in sequence. The organic EL part includes organic EL-driving reflecting electrodes(73) for improving the luminous efficiency of the device, organic EL layers(71) formed on the organic EL driving reflecting electrodes for generating light, and organic EL driving transparent electrodes(72) interposed between the organic EL layers and the organic EL driving reflecting electrodes for driving the organic EL part.

Description

Liquid crystal display

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device in which the thickness of a product is reduced by adopting an organic EL element as a backlight and integrally manufacturing the liquid crystal display element.

In general, a liquid crystal display is a display that displays an image by transmitting and blocking light by using a liquid crystal material having dielectric anisotropy. A liquid crystal display device is a transmissive type that transmits backlight light to display an image and reflects natural light incident from the outside. It is divided into the reflection type which makes an image display.

The transmissive liquid crystal display device has a high brightness of the screen because the backlight is installed on its back and used as its own light source, but it is difficult to apply to a portable device because of the high power consumption. On the other hand, the reflective liquid crystal display device displays the image because the natural light incident from the outside is selectively transmitted by the switching action of the liquid crystal layer and is reflected back from the reflective film to be emitted to the front surface. It is difficult to use.

In order to solve the disadvantages of the transmissive and reflective liquid crystal display device, a transflective liquid crystal display device has recently been developed. The transflective liquid crystal display displays an image by using both external incident light and / or backlight light, and the configuration according to the embodiment is well shown in FIG. 1.

As shown in the figure, the transflective liquid crystal display includes upper and lower substrates 12 and 14 arranged in pairs at regular intervals to face each other, and on the lower surface of the upper substrate 12 and the upper surface of the lower substrate 14. The transparent electrodes 16 (16 '), the insulating layers 18 (18'), and the alignment layers 20 (20 ') are sequentially stacked, and the upper and lower substrates 12 are formed using the sealant 22. The liquid crystal layer 24 is formed by sealing and assembling 14 and injecting a liquid crystal material into the space therebetween. In addition, a polarizer 26 is attached to an outer surface (upper surface) of the upper substrate 12, and a natural light incident through the upper substrate 12 is reflected on the outer surface (lower surface) of the lower substrate 14 and the backlight BL is applied. In order to transmit light, a semi-transmissive reflective film 28 is attached.

The semi-transmissive reflective film 28 has a multilayer structure in which a high refractive index layer and a low refractive index layer are alternately formed, and has a polarization angle characteristic. Accordingly, the semi-transmissive reflective film 28 has a property of refracting and reflecting only light incident beyond the polarization angle among natural light incident from the outside, and ultimately combines reflection and polarization functions.

In the conventional transflective liquid crystal display device having the above-described configuration, the light incident from the outside is basically a polarizing plate 26, the liquid crystal layer 24 and the semi-transmissive reflective film 28, and the light reflected back to the liquid crystal layer ( It is designed to have a traveling path (L1) of the light to be emitted through the 24 and the polarizing plate 26, but sometimes the backlight (Back Light) is turned on and used at the same time can improve the brightness. A semi-transmissive liquid crystal display device having a general backlight is disclosed in Korean Laid-Open Patent No. 2001-053801. The backlight is formed of a lamp assembly composed of a lamp reflector, the light source of which surrounds the lamp and reflects the lamp light and is incident in the direction of the light guide plate, and the light guide plate which diffuses the incident lamp light and the back surface of the light guide plate, It consists of a reflecting sheet reflecting the lamp light, a diffusion sheet formed on the front surface of the light guide plate, a prism sheet and supported by a lower cover and a mold frame.

The liquid crystal display device has a limiting factor in the thickness of the product because the liquid crystal display (LCD) panel unit and the backlight is separated. In particular, when using LEDs (Light Emitted Diodes) or CCFLs (Cold Cathode Fluorescent Lamps) as the backlight, there are many problems that are limited due to the minimum thickness of the light source and the light guide plate that uniformly diffuses the light onto the screen. .

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a liquid crystal display device which realizes a compact and lightweight product by reducing the thickness of the product by adopting an organic EL element as a backlight and manufacturing it integrally with the liquid crystal display element. have.

1 is a cross-sectional view of a conventional liquid crystal display device;

2 is a cross-sectional view of a liquid crystal display device according to an embodiment of the present invention;

3 is a partially exploded perspective view of a liquid crystal display according to an exemplary embodiment of the present invention;

4 is a plan view of a transflective film of the liquid crystal display of FIG.

5 is a cross-sectional view of an organic EL unit of the liquid crystal display of FIG. 3;

6 is a cross-sectional view of a liquid crystal display device according to another embodiment of the present invention;

7 is an exploded perspective view of a portion of a liquid crystal display according to another exemplary embodiment of the present invention.

<Description of the reference numerals for the main parts of the drawings>

32 ... top board 34 ... bottom board

50 ... LCD panel part 51 ... Upper transparent electrode

52 ... bottom transparent electrode 55 ... liquid crystal layer

56 transflective film 57 openings

70.organic EL layer 71.organic EL layer

72.organic EL driving transparent electrode 73.organic EL driving reflective electrode

74 electron transport layer 75 light emitting layer

76 ... hole transport floor 77 ... intersection

According to an aspect of the present invention, there is provided an LCD device including an upper and lower substrates facing each other, an LCD panel portion formed under the upper substrate and displaying an image, and the lower substrate and the LCD panel portion. And an organic EL portion which intervenes to generate light, and a phase difference plate and a polarizing plate which are sequentially stacked on the outer side of the upper substrate.

In addition, the organic EL unit is formed on the upper surface of the lower substrate and reflects light upward, and is formed on the upper surface of the organic EL driving reflecting electrode, and in order of the electron transport layer, the light emitting layer, and the hole transport layer. And an organic EL driving transparent electrode interposed between the LCD panel portion and the organic EL layer and supplying holes to the hole transport layer to emit light from the light emitting layer.

In addition, the LCD panel portion is located on the bottom surface of the upper substrate and the upper surface of the organic EL portion, respectively, and are formed on the inner side of the upper and lower transparent electrodes facing each other, and the inside of the upper and lower transparent electrodes, respectively, and the surface is rubbed to provide liquid crystal And a liquid crystal layer in which a liquid crystal is filled between the upper and lower alignment layers to be aligned, and an insulating layer formed under the lower transparent electrode so as not to be shorted with the organic EL driving transparent electrode. It is characterized by.

The display device may further include a color filter interposed between the lower transparent electrode of the LCD panel and the insulating layer to form a plurality of pixels of different colors.

The insulating layer is a semi-transmissive reflective film having an opening, and the organic EL driving reflective electrode and the organic EL driving transparent electrode are all formed in a stripe shape and are orthogonal to each other.

The opening of the transflective film is formed so as to correspond to the intersection where the organic EL driving reflective electrode and the organic EL driving transparent electrode cross each other, and the organic EL driving transparent electrode is an ITO film.

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

2 and 3, a liquid crystal display according to an exemplary embodiment of the present invention includes an upper panel and a lower panel 32 and 34 positioned opposite to each other, and an LCD panel formed below the upper substrate 32. A portion 50 and an organic EL 70 portion interposed between the lower substrate 34 and the LCD panel portion 50 are included.

The lower substrate 34 is a material capable of supporting the product itself, and uses a material having heat resistance in the process of forming the organic EL unit 70 or the process of manufacturing the LCD panel 50. For example, glass or plastic may be used, and it is preferable to use a material having similar thermal expansion characteristics to that of the upper substrate 32.

The upper substrate 32 is preferably a material capable of supporting a product as a transparent material, for example, glass or plastic.

The organic electroluminescence (70) part 70 is formed on the upper surface of the organic EL driving reflecting electrode 73 and the organic EL driving reflecting electrode 73 formed on the upper surface of the lower substrate 34, and light is generated. And an organic EL driving transparent electrode 72 interposed between the organic EL layer 71 and the LCD panel 50.

As the cathode of the organic EL driving reflection electrode 73, a metal having a low work function is used as a cathode which is an electron injection electrode. This is because a high current density can be obtained in electron injection by lowering the barrier formed between the organic EL driving reflection electrode 73 and the organic EL layer 71. This can increase the luminous efficiency of the device. The organic EL driving reflection electrode 73 drives the organic EL portion 70 together with the organic EL driving transparent electrode 72. In other words, it serves as a cathode for supplying electrons to the electron transport layer 74. In addition, the organic EL driving reflection electrode 73 is formed of a metal to reflect the light generated in the organic EL layer 71 to proceed toward the upper substrate 32.

The organic EL layer 71 is laminated in the order of the electron transport layer 74, the light emitting layer 75, and the hole transport layer 76 from below. In other words, a hole transporting layer (HTL) 76, which is a hole transporting layer, and an electron transporting layer 74, which is an electron transporting layer, are formed on upper and lower surfaces of the light emitting layer 75, respectively. In addition, the electron transport layer 74, the light emitting layer 75, and the hole transport layer 76 are all organic thin films made of an organic compound.

The organic EL driving transparent electrode 72 has a high work function as an anode, which is a hole injection electrode, and uses a transparent metal oxide so that light emitted from the light emitting layer 75 can come out of the device, and is the most widely used hole injection electrode. ITO (Iinduim Tin Oxide). The organic EL driving transparent electrode 72 serves to drive the organic EL portion 70. That is, the anode serves to supply holes to the hole transport layer 76 to emit light from the light emitting layer 75. Since the organic EL driving transparent electrode 72 is formed in the traveling direction of light generated in the light emitting layer 75, it is preferable that the organic EL driving transparent electrode 72 is a transparent film such as an ITO film in order to increase transmittance.

The organic EL driving reflection electrode 73 and the organic EL driving transparent electrode 72 are formed in a stripe shape, and the organic EL driving reflection electrode 73 and the organic EL driving transparent electrode 72 are formed to be orthogonal to each other. Therefore, when power is supplied, light is generated only at the intersection portion 77 where the organic EL driving reflection electrode 73 and the organic EL driving transparent electrode 72 are orthogonal to each other. Therefore, the power consumption can be minimized because only the intersection portion 77 emits light.

The driving of the organic EL portion 70 having the above structure is performed as follows. As shown in FIG. 5, when a voltage is applied to the organic EL driving reflective electrode 73 and the organic EL driving transparent electrode 72, electrons injected from the organic EL driving reflective electrode 73 are transferred to the electron transport layer 74. ) Is moved to the light emitting layer 75. On the other hand, holes injected from the organic EL driving reflecting electrode 73 are moved to the light emitting layer 75 with the help of the hole transport layer 76. Electrons and holes encountered in the light emitting layer 75, which is an organic material, generate excitons, which are high energy excitons. At this time, the excitons are changed from the excited state to the ground state, whereby light is emitted from the light emitting layer 75. Will occur. The generated light is emitted toward the organic EL driving transparent electrode 72. In addition, the color of the light varies depending on which organic material constituting the emission layer 75, and all colors may be realized using respective organic materials emitting R, G, and B.

The upper and lower transparent electrodes 51 and 52 are formed to face the LCD panel 50 so as to face each other and cross at right angles. The upper transparent electrode 51 is formed on the bottom surface of the upper substrate 32, and the lower transparent electrode 52 is formed on the organic EL driving transparent electrode 72 of the organic EL unit 70. An insulating layer 56 is interposed therebetween to prevent a short circuit between the lower transparent electrode 52 and the organic EL driving transparent electrode 72. The upper and lower transparent electrodes 51 and 52 have a plurality of stripe shapes and are formed by an indium tin oxide (ITO) film or the like. Upper and lower alignment layers 53 and 54 are formed inside the upper and lower transparent electrodes 51 and 52, respectively. Surfaces of the upper and lower alignment layers 53 and 54 are rubbed in a predetermined direction so that the liquid crystals filled between the upper and lower alignment layers 53 and 54 are arranged in a predetermined direction. A nematic liquid crystal, a smetic liquid crystal, a cholesteric liquid crystal, or the like having a predetermined twist angle forms the liquid crystal layer 55.

The insulating layer 56 formed on the lower surface of the lower transparent electrode 52 is preferably a transflective reflective film 56 having an opening 57 formed therein. This causes the light generated in the organic EL portion 70 to diverge through the opening 57. The transflective film 56 is made of Cr, Al, or the like, and the surface thereof is a reflective surface that reflects light incident from the upper substrate 32 side.

In addition, referring to FIG. 4, an opening 57 having a predetermined size formed in the transflective film 56 partitions the transflective film 56 into a reflective area 56a and a transmissive area 56b. In this case, the total area of the opening 57 is preferably formed in an area ratio of 5% to 30% or less with respect to the total area of the transflective film 56. This is an appropriate limit to prevent the reflectance from decreasing by increasing the opening 57. The opening 57 can be easily manufactured by a photo process, a developing process, and a peeling process using a resist. The planar shape of the opening 57 may be square, or may be polygonal or elliptical. It is also possible to form the opening 57 at the same time as forming the transflective film 56, in which case the number of manufacturing steps may not be increased.

The opening 57 of the semi-transmissive reflective film 56 is formed so as to correspond to the intersection 77 where the organic EL driving transparent electrode 72 and the organic EL driving reflecting electrode 73 cross at right angles. Therefore, light generated at the intersection portion 77 travels toward the upper substrate 32 only through the opening 57. In this case, the light transmittance can be increased to minimize the power consumption.

The polarizer 80 is disposed on the outer surface of the upper substrate 32, and the retardation plate 81 is disposed between the polarizer 80 and the upper substrate 32.

Meanwhile, the color filter 78 may be interposed between the lower transparent electrode 52 of the LCD panel 50 and the transflective film 56 for color implementation. 6 and 7, a liquid crystal display according to another exemplary embodiment of the present invention includes an upper panel and a lower panel 32 and 34 positioned opposite to each other, and an LCD panel formed below the upper substrate 32. A portion 50 and an organic EL portion 70 interposed between the lower substrate 34 and the LCD panel portion 50 are included.

Here, the same reference numerals as in the above-described drawings refer to the same member having the same function, and are substantially the same as described above, and thus detailed description thereof will be omitted.

The color filter 78 is interposed between the lower transparent electrode 52 of the LCD panel 50 and the transflective film 56. The color filter 78 may form a plurality of pixels of different colors. Three color layers of R (red), G (green), and B (blue) are arranged in the color filter 78 in a predetermined pattern. On the surface of the color filter 78, a plurality of stripe lower transparent electrodes 52 are formed by an ITO film or the like. A plurality of stripe-shaped lower transparent electrodes 52 formed for each color layer of the color filter 78 intersect the upper transparent electrodes 51 formed on the bottom surface of the upper substrate 32.

In the opening 57, a plurality of spherical openings may be arranged in a horizontal arrangement for each pixel of the color filter 78 which forms a plurality of pixels of different colors. Alternatively, a plurality of circular openings may be discretely arranged for each pixel, or one large spherical opening may be arranged for each pixel. In order to prevent light leakage in each inter-pixel region in the transmissive mode, a black matrix layer, which is a light shielding portion formed between the colored layers of the color filter 78, is provided between the pixels in a plane manner. The black matrix layer is formed by depositing a Cr layer or a photosensitive black resin.

Referring to the operation of the liquid crystal display according to the present invention configured as described above are as follows.

In a dark environment, light is generated in the light emitting layer 75 of the organic EL layer 71 when a voltage is applied to the organic EL driving reflective electrode 73 and the organic EL driving transparent electrode 72 of the organic EL portion 70. When fluorescent molecules are deposited on the emission layer 75, colors of R, G, and B may be realized. Light generated in the light emitting layer 75 of the organic EL unit 52 passes through the organic EL driving transparent electrode 72, and the opening 57 and the lower transparent portion of the semi-transparent reflective film 56 of the LCD panel 50. Passes through the electrode 52 and enters into the liquid crystal layer 55. The transmittance may be improved by interposing the high transparent color filter 78 between the lower transparent electrode 52 and the transflective film 56. The light emitted through the liquid crystal layer 55 is sequentially passed through the retardation plate 81 and the polarizing plate 80 to be emitted to the outside.

In a bright environment, external light incident on the polarizing plate 80 passes through the liquid crystal layer 55 and then is reflected by the semi-transmissive reflecting film 56, and again passes through the polarizing plate 80 and is emitted to the outside.

In this case, the color can be realized by interposing the high transparent color filter 78 between the lower transparent electrode 52 and the transflective film 56.

As described above, the liquid crystal display device according to the present invention has an advantage of reducing the thickness of the product to realize a compact and light product by adopting an organic EL element as a backlight and integrally manufactured with the liquid crystal display element.

In addition, there is an advantage that a high-brightness product is possible by using a high-luminance organic EL device as a backlight.

In addition, since only a portion corresponding to the opening region emits light, a low power consumption backlight can be realized.

In addition, when the light emitting layer of the organic EL portion is set to R, G, and B patterns, use of a color filter is not necessarily required, and therefore a high-permeable color filter can be used. Therefore, high purity color can be realized by the light emitting layer of the organic EL unit in the transmissive mode, and there is an advantage that a brighter color can be realized in the reflective mode.

Although the present invention has been described with reference to one embodiment shown in the accompanying drawings, this is merely exemplary, and it will be understood by those skilled in the art that various modifications and equivalent other embodiments are possible. Could be. Therefore, the true scope of protection of the present invention should be defined only by the appended claims.

Claims (8)

Upper and lower substrates facing each other; An LCD panel unit formed below the upper substrate and displaying an image; An organic EL unit which generates light through the lower substrate and the LCD panel unit; And a phase difference plate and a polarizing plate which are sequentially stacked on the outer side of the upper substrate. The method of claim 1, An organic EL driving reflection electrode formed on an upper surface of the lower substrate and reflecting light upward; An organic EL layer formed on an upper surface of the organic EL driving reflection electrode and stacked from the bottom in order of an electron transport layer, a light emitting layer, and a hole transport layer; And an organic EL driving transparent electrode interposed between the LCD panel portion and the organic EL layer to supply holes to the hole transport layer to emit light from the light emitting layer. The method of claim 1, The upper and lower transparent electrodes disposed on the bottom surface of the upper substrate and the upper surface of the organic EL unit, respectively and opposed to each other; Upper and lower alignment layers formed inside the upper and lower transparent electrodes, respectively, to rub the surface thereof to align the liquid crystals; A liquid crystal layer in which a liquid crystal is filled between the upper and lower alignment layers; And an insulating layer formed under the lower transparent electrode to prevent a short circuit from the organic EL driving transparent electrode. The method according to any one of claims 1 to 3, And a color filter interposed between the lower transparent electrode of the LCD panel unit and the insulating layer to form a plurality of pixels of different colors. The method of claim 3, And the insulating layer is a transflective film having an opening. The method of claim 3, And the organic EL driving reflective electrode and the organic EL driving transparent electrode are each formed in a stripe shape and are orthogonal to each other. The method of claim 5, And the opening of the transflective film is formed so as to correspond to the intersection where the organic EL driving reflective electrode and the organic EL driving transparent electrode cross each other. The method of claim 3, And the organic EL driving transparent electrode is an ITO film.