Title of Invention

"LIQUID CRYSTAL DISPALY DEVICE"

Abstract

A liquid crystal display device (LCD) has a lower substrate, and has a lower electrode, a lower alignment layer, liquid crystals, an upper alignment layer and an upper substrate deposited sequentially on the lower substrate. The LCD is constructed such that the upper and lower substrates are used as retardation films for light compensation of the liquid crystal layers. The retardation films are directly used as substrates, to avoid the need of using glass substrates or plastic substrates having no birefringent anisotropy. Thus, the device structure is simplified, the overall thickness and weight of the device is considerably reduced, and the manufacturing cost is reduced accordingly.

Full Text

The present invention relates to a liquid crystal display device (LCD), and more particularly, to an LCD which can have a simplified structure by using a retardation film as a substrate, and can have reduced manufacturing cost. An LCD displays a desired image by controlling light intensity, by transmitting or shielding light depending on voltage and temperature change using liquid crystals. Liquid crystals are in an intermediate state between a liquid and a solid. LCDs have been widely used because of various advantages, that is, they have low electricity consumption, and are thin and compact devices. However, they still have problems in attaining large-scale devices, perfect coloration and wide viewing angle. An LCD is classified as one of several types according to its operation mode, for example, a dynamic scattering (DS) mode, a guest host (GH) mode, a twisted nematic (TN) mode, a super twisted nematic (STN) mode. The respective operation modes will now be explained briefly. The DS LCD utilizing an electro-optical effect of liquid crystals does not require a polarizing film and is less dependant upon viewing conditions. However, the DS LCD consumes a large amount of electricity. Specifically, a reflection type DS LCD has a mirror display plane, which causes a difficulty in viewing a displayed image. The GH LCD utilizes the anisotropy of a light absorption coefficient of the dichroic dye added to the liquid crystals. This enables color switching, achieves a wide viewing angle and allows a low drive voltage. The TN LCD has a thin film, made of anisotropic nematic liquid crystals having a positive dielectric constant, inserted between two glass substrates. There, transparent electrodes are coated so that the long axis of the liquid crystal molecules are in parallel with the glass substrate surfaces. There is a 90° twisted arrangement between upper and lower substrates. The TN LCD can be driven at a low voltage, and low power consumption and a long service life. However, the viewing angle of the TN LCD is limited. The STN LCD having a larger twist angle of the liquid crystal molecules than the TN LCD, can attain multiplex driving and high-definition picture quality. However, according to the STN mode, a non-selection state is colored due to a birefringence effect, thus it is difficult to display multiple colors. The conventional STN LCD has liquid crystals 11 filled into the central portion thereof. A sealing member is provided in the front, rear, left and right sides of a stacked structure to form an airtight vessel together with the upper and lower members, and the vessel is filled with liquid crystals. Upper and lower alignment layers, for directing the alignment of liquid crystals, are formed on the upper and lower surfaces, respectively, of the liquid crystals. Also, indium-tin oxide (ITO) electrodes, for supplying current to the liquid crystals, are respectively formed outside of the upper and lower alignment layers. Substrates, made of glass or plastic, are respectively installed outside of the ITO electrodes. Retardation films spaced apart from each other by a predetermined distance, are respectively installed outside of the substrates. Polarizing films are installed, each being spaced apart from the respective retardation films by a predetermined distance. A reflecting film is formed under the polarizing film. In the conventional STN LCD having the aforementioned structure, plastic substrates are widely used instead of glass substrates to produce a flexible LCD. However, in this case, if the plastic substrates having a birefringent anisotropy are interposed between the polarizing films, another retardation effect occurs due to the interaction with the polarizing films. This effect prevents the displaying of an image. Thus, it is necessary to employ plastic substrates having no birefringent anisotropy. Accordingly, the manufacturing method of such plastic substrates becomes different from that of the plastic substrates having a birefringent anisotropy, which increases the manufacturing cost of the LCD. Summary of the Invention It is an object of the present invention to provide an LCD which can have a simplified structure and manufacturing process, and reduced overall manufacturing cost, by using a retardation film as a flexible substrate. To accomplish the object of the present invention, there is provided an LCD having a lower substrate, a lower electrode, a lower alignment layer, liquid crystals, an upper alignment layer, an upper electrode and an upper substrate, deposited sequentially, wherein the upper and lower substrates are constructed to function as retardation films for light compensation of the liquid crystal layer. According to the present invention, since the LCD employs retardation films as substrates, without using glass or plastic substrates as in the conventional art, the device structure is simplified and the overall manufacturing cost is reduced. According to the present invention, there is provided a liquid crystal display device (LCD) comprising: an upper and a lower retardation films facing each other; an upper and a lower electrodes formed on the inside surfaces of the upper and lower retardation films respectively; an upper and a lower alignment layers formed on the inside surfaces of the upper and lower electrodes respectively; and liquid crystals located between the upper and lower alignment layers. Brief Description of the Drawings The above objects and advantages of the present invention will become more apparent by describing in detail a preferred embodiment thereof with reference to the attached drawings in which: FIG. 1 is a sectional view schematically showing the structure of a conventional STN LCD; and FIG. 2 is a sectional view schematically showing the structure of an STN LCD according to the present invention. Detailed Description of the Invention Referring to FIG. 1, the conventional STN LCD has liquid crystals 11 filled into the central portion thereof. (Although not shown herein, a sealing member is provided in the front, rear, left and right sides of a stacked structure to form an airtight vessel together with the upper and lower members, and the vessel is filled with liquid crystals.) Upper and lower alignment layers 12a and 12b, for directing the alignment of liquid crystals 11, are formed on the upper and lower surfaces, respectively, of the liquid crystals 11. Also, indium-tin oxide (ITO) electrodes 13a and 13b, for supplying current to the liquid crystals 11, are respectively formed outside of the upper and lower alignment layers 12a and 12b. Substrates 14a and 14b, made of glass or plastic, are respectively installed outside of the ITO electrodes 13a and 13b. Retardation films 15a and 15b spaced apart from each other by a predetermined distance, are respectively installed outside of the substrates 14a and 14b. Polarizing films 16a and 16b are installed, each being spaced apart from the respective retardation films 15a and 15b by a predetermined distance. A reflecting film 17 is formed under the polarizing film 16b. In the conventional STN LCD having the aforementioned structure, plastic substrates are widely used instead of glass substrates to produce a flexible LCD. However, in this case, if the plastic substrates having a birefringent anisotropy are interposed between the polarizing films 16a and 16b, another retardation effect occurs due to the interaction with the polarizing films 16a and 16b. Referring to FIG. 2, liquid crystals 21 are filled into the central portion of the LCD according to the present invention, and upper and lower alignment layers 22a and 22b, for directing the alignment of the liquid crystals 21, are respectively formed on the upper and lower surfaces, respectively, of the liquid crystals 21. Upper and lower ITO electrodes 24a and 24b, for supplying current to the liquid crystals 21 are formed on the outside surfaces of the upper and lower alignment layers 22a and 22b, respectively, and retardation films 26a and 26b are installed on the outside surfaces of the upper and lower ITO electrodes 24a and 24b, respectively. Here, the upper and lower electrodes 24a and 24b are made of 100~3000 A thick ITO single layer or multiple layers in which a metal layer and a metal oxide layer are stacked. At this time, the metal layer can be Ag, Cu, Al, Au or Cr, and the metal oxide layer can be SiOx, ITO, SnOx or InOx. The material of the retardation films 26a and 26b can be a polymer such as polyvinyl alcohol (PVA), polycarbonate (PC) or polyester sulfur (PES). The retardation films 26a and 26b are constructed to have compensation values of 200 to 700 nm and 1500-2500 nm, and a thickness of 10 to 2000 mm. The retardation films 26a and 26b serve to compensate light in addition to the function as conventional substrates. Also, insulating layers 23 a and 23b for protecting the alignment layers 22a and 22b, and a functional film (not shown) which is resistant to chemicals and is non-abrasive, for preventing electrode damage, are preferably formed, between the upper alignment layer 22a and the upper ITO electrode 24a, and between the lower alignment layer 22b and the lower ITO electrode 24b, respectively. Further, planarization layers 25a and 25b may be formed, between the upper retardation film 26a and the upper ITO electrode 24a, and between the lower retardation film 26b and the lower ITO electrode 24b, respectively, for the purpose of compensating a planarization degree, in the case when the planarization degree is poor. Also, other functional films may be formed, e.g., gas blocking layers for preventing the transmittance of oxygen, or solvent blocking layers for blocking various chemical solvents. Polarizing films 27a and 27b are installed above and below the retardation films 26a and 26b, respectively, being spaced apart therefrom by a predetermined distance. A reflecting film 28 is installed below the lower polarizing film 27b, being spaced apart therefrom by a predetermined distance. Here, the reflecting film 28 is installed in the case of a reflection-type device, but not installed in the case of a transmission-type device. Also, a color filter layer may be further provided between the polarizing films 27a and 27b. As described above, in the LCD according to the present invention, retardation films are directly used as substrates. This avoids the need to use glass substrates or plastic substrates having no birefringent anisotropy, like in the conventional LCD. Thus, the device structure is simplified, the overall thickness and weight of the device is considerably reduced, and the manufacturing cost is reduced accordingly. WE CLAIM: 1. A liquid crystal display device (LCD) comprising: an upper and a lower retardation films facing each other; an upper and a lower electrodes formed oil the inside surfaces of the upper and lower retardation films respectively; an upper and a lower alignment layers formed on the inside surfaces of the upper and lower electrodes respectively; and liquid crystals located between the upper and lower alignment layers. 2. The liquid crystal display device as claimed in claim 1, having insulating layers for protecting said alignment layers, formed between said upper alignment layer and said upper electrode, and between said lower alignment layer and said lower electrode. 3. The liquid crystal display device as claimed in claim 1, having planarization layers for compensating for a planarization degree of said retardation films, formed between said upper retardation film and said upper electrode, and between said lower retardation film and said lower electrode. 4. The liquid crystal display device as claimed in claim 1, having gas blocking layers formed between said upper retardation film and said upper electrode, and between said lower retardation film and said lower electrode. 5. The liquid crystal display device as claimed in claim 1, having solvent blocking layers formed between said upper retardation film and said upper electrode, and between said lower retardation film and said lower electrode. 6. The liquid crystal display device as claimed in claim 1, wherein said upper and lower electrodes are made of 100 to 3000 A thick Indium Tin Oxide single layer. 7. The liquid crystal display device as claimed in claim 1, wherein said upper and lower electrodes are made of 100 to 3000 A thick multiple layers in which a metal layer and a metal oxide layer are stacked. 8. The liquid crystal display device as claimed in claim 7, wherein said metal layer is one selected from the group consisting of Ag, Cu, Al, Au and Cr, and said metal oxide layer is one selected from the group consisting of SiOx, Indium Tin Oxide, SnOx, and InOx. 9. A liquid crystal display device (LCD), substantially as hereinbefore described with reference to the accompanying drawings.

Documents:

2814-del-1997-abstract.pdf

2814-del-1997-claims.pdf

2814-del-1997-correspondence-others.pdf

2814-del-1997-correspondence-po.pdf

2814-del-1997-description (complete).pdf

2814-del-1997-drawings.pdf

2814-del-1997-form-1.pdf

2814-del-1997-form-19.pdf

2814-del-1997-form-2.pdf

2814-del-1997-form-3.pdf

2814-del-1997-form-4.pdf

2814-del-1997-form-6.pdf

2814-del-1997-gpa.pdf

2814-del-1997-petition-138.pdf