Method for fabricating color filter of liquid crystal display device

A method for fabricating a color filter of an LCD device includes: providing a cliché having a plurality of grooves; filling Red, Green and Blue colored inks into the grooves of the cliché; and repositioning the Red, Green and Blue colored inks onto a substrate of the LCD device.

This application claims the benefit of the Korean Application No. 2002-85635 filed in Korea on Dec. 27, 2002, which is hereby incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a liquid crystal display device, and particularly, to color filters in a liquid crystal display device and a method of fabricating thereof.

2. Description of the Related Art

A cathode ray tube (CRT) monitor has mainly been used for displaying information in TV and computer so far. The CRT has high image quality and brightness. However, as an image screen grows larger, the depth of the CRT monitor becomes so big that the monitor occupies a very large volume. In addition, the weight of the CRT display has always been a problem in portable devices.

To address the problems above, flat panel display devices, such as liquid crystal displays, plasma display panels, organic electro luminescence displays, light emitting diodes and, field emission displays, have been used instead of a CRT monitor. Among these flat panel display devices, the liquid crystal display (LCD) device is used as a monitor of a notebook PC or of a desktop PC because the LCD has low power consumption. Color filters and a manufacturing thereof for a related art LCD device having all kinds of display applications will be described in detail with reference toFIGS. 1,2A and2B.

FIG. 1is a view showing a cross-section of a related art general LCD device. As shown inFIG. 1, the LCD device includes a lower substrate10, an upper substrate20, and a liquid crystal layer15formed in between the upper and lower substrates10and20. A thin film transistor T and a pixel electrode7are formed on the lower substrate10. The thin film transistor T includes: a gate electrode1to which a scan signal is applied; a semiconductor layer3for transmitting a data signal corresponding to the scan signal; a gate insulating layer2for isolating the semiconductor layer3and the gate electrode1electrically; a source electrode4formed on an upper part of the semiconductor layer3for applying the data signal; and a drain electrode5applying the data signal to the pixel electrode7. The semiconductor layer3comprises an active layer3aformed by depositing amorphous silicon (a-Si), and an n+ doped ohmic contact layer3bon both upper sides of the active layer3a. A passivation layer6and the pixel electrode7are formed on the thin film transistor T, and a first alignment layer4aformed for aligning liquid crystal molecules is formed on an upper part of the pixel electrode7. The pixel electrode7is made by a transparent conductor, such as indium tin oxide (ITO) or indium zinc oxide (IZO), so that the light can be transmitted through the pixel electrode.

A black matrix12is formed on the upper substrate20for preventing the light from leaking between pixels, and color filters11of Red R, Green G, and Blue B for realizing actual colors are formed on the black matrix12. A flattening layer (not shown) can be additionally formed on the color filter11for flattening the color filter and for improving an adhesive bond to a common electrode13subsequently formed on the color filter. The common electrode13is for applying voltage to the liquid crystal layer15. A second alignment layer4bfor aligning the liquid crystal molecules is formed on the common electrode13. A transparent conductor, such as ITO or IZO, is used as the common electrode13such that the light can be transmitted through the common electrode.

The LCD device is made by repeating processes, such as thin film deposition, and photolithography and etching processes, for each color used in the LCD device. Fabrication methods for color filters include: the stain method, pigment disperse method, and an electrophoresis deposition method. These three kinds of methods fabricate red, green, and blue primary color filters through three or more processes for each color of color filter.

The stain method includes processes for imparting photo-sensitivity to stainable polymer material, forming stain-subjected pattern, and staining the pattern with respective colors. In the color filter fabrication method of the stain method, a process of passing a stainable photosensitive film through the stain pattern is repeated for the respective R, G and B colors. Subsequently, the next step is forming a top coat layer.

The electrophoresis deposition method includes steps of forming electrophoresis deposition layers by extracting respective colors by electrophoresis. However, the process for forming the electrophoresis deposition layers on a transparent conductive layer has to be repeated three times to achieve each of the respective colors. Therefore, the fabrication process for the color filter takes a lot of time and has complicated process operations.

The pigment disperse method includes the steps of making a colored resist by dispersing the pigment on a resin and applying respective colored patterns. The steps of applying the colored resist and forming the colored pattern are repeated to achieve each of the respective red, green and blue colors, and therefore, fabrication time is increased and cost is increased. Also, to form the respective R, G and B color filters, the colored resist is deposited across the entire substrate and portions except the necessary portion should be removed. Since only ⅓ of the entire resist sheet is needed, ⅔ of the entire resist sheet should be removed, and therefore, the resist is heavily wasted.

An ink jet method for forming the color filters precisely were the color filters should be positioned on an LCD device has been suggested for solving the problems in the above methods. The ink jet method Red R, Green G and Blue B colored inks through an injection nozzle of an ink jet device onto to the lower substrate. The ink jet method can be used in the thin film transistor on color filter LCD device structure to preventing color filter mis-alignment and to improve the aperture rate.

FIGS. 2A and 2Bare views showing a fabrication method for a color filter of an LCD device in the ink jet method of the related art. As shown inFIG. 2A, the gate electrode51, the gate insulating layer52and the semiconductor layer53of a thin film transistor are formed on the transparent lower substrate50. Source and drain electrodes54and55, which are separated from each other with a predetermined gap, are formed on the semiconductor layer53using photolithography. In addition, a photoresist is patterned to form an ink separating wall56. A passivation layer57is then formed on the upper part of the wall56to protect the thin film transistor T.

As shown inFIG. 2B, the respective R, G and B colored inks60aare injected through the injection nozzle60into the pixels using the ink separating wall56. Subsequently, the colored inks60asolidify to form a color filter59in each respective pixel59. Accordingly, the waste of ink can be prevented since it is precisely positioned. However, the color filters for each color all are positioned in a step separate from a step of positioning all of the color filters of another color. Therefore, the process is complex since subsequent color filters of one color have to be positioned amongst other already positioned color filters of another color.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a method for manufacturing an LCD device that substantially obviates one or more problems due to limitations and disadvantages of the related art.

An object of the present invention is to prevent ink from being wasted and to simplify processes for forming all of the color filters.

To achieve the object of the present invention, as embodied and broadly described herein, there is provided a method for fabricating a color filter of an LCD device including providing a cliché having a plurality of grooves; filling Red, Green and Blue colored inks into the grooves of the cliché; and repositioning the Red, Green and Blue colored inks onto a substrate of the LCD device.

In another aspect, a method for fabricating color filters of a Liquid Crystal Display (LCD) device includes: providing a cliché having a plurality of grooves; filling Red, Green and Blue colored inks into the grooves of the cliché; transferring the colored inks filled into the grooves of the cliché onto a printing roll; and applying the Red, Green and Blue colored inks onto a substrate of the LCD device from the printing roll.

In another aspect, a method for fabricating color filters of a Liquid Crystal Display (LCD) device includes: providing a cliché having grooves same as a pattern of color filters; filling Red, Green and Blue colored inks into the cliché concurrently with an ink jet; transferring the Red, Green and Blue colored inks filled into the grooves of the cliché onto the printing roll; and applying the Red, Green and Blue colored inks onto a substrate of the LCD device by rotating the printing roll across the substrate.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 3A through 3Fare processing views showing the method for fabricating color filters of an LCD device according to an exemplary embodiment of the present invention. As shown inFIG. 3A, a substrate110is provided with a buffer layer103. For example, the buffer layer103can be a metallic, an organic or a silicon layer provided on the substrate110. Subsequently, grooves105are formed in the buffer layer103through a photolithography process to form a cliché100. The shape and position of the grooves105correspond to the R, G and B color filters, which will later be positioned on an LCD device.

As shown inFIG. 3B, red, green and blue colored inks are filled into the grooves105through the injection nozzles110a˜110cof respective R, G and B ink jet devices. The filling of colored ink123into the grooves105can be performed using the ink jet method. In the alternative, the ink jet device can include an ink supplying unit divided into red, green and blue colors, nozzles through which the ink is injected, and channels that are disposed between the respective ink supplying unit and the nozzles, and paths for moving the ink. When the inks in the ink supplying unit is compressed, the inks of R, G and B colors are injected from the nozzles at the same time. Accordingly, the inks of R, G and B colors can be filled simultaneously or concurrently into the grooves105of the cliché100. Thus, the ink filling time can be reduced and ink waste can be prevented.

After the ink filling process is ended, the colored ink123filled into the cliché100is allowed to solidify. After the colored inks123have solidified enough to somewhat retain the shape of the groove105, the colored inks123are separated from the buffer layer103and transferred onto a surface of a printing roll128as an ink pattern127. As shown inFIG. 3C, a blanket129can be used on the surface of the printing roll128in order to improve adhesive bonding of the printing roll with the colored inks123.

The buffer layer103makes the colored inks123separate easily from the cliché100such that the ink attaches onto the printing roll128easily and protects the substrate130from the shock of the printing roll128. In other words, the adhesive bond of the colored ink123with the buffer layer103is weaker than the adhesive bond of the colored ink with the printing roll128, and therefore, the ink will detach or be released from the buffer layer103. In the alternative, the grooves105may be formed by etching the substrate without forming the buffer layer on the substrate130. However, cracks may be generated on lower part of the substrate due to the impact of the printing roll128. The buffer layer103protects the substrate by absorbing the impact of the printing roll128.

The ink can be easily separated from the cliché100easily by using changes of adhesion property of the ink according to temperature differences between the cliché100and the printing roll128. An ink having improved adhesion as temperature increases can be used such that the ink can be easily separated from the cliché100when the temperature of the printing roll128is set to be higher than that of the cliché100. If the colored ink has the characteristic of improved adhesion as temperature decreases, the colored ink can be easily separated from the cliché100when the temperature of the printing roll128is set to be lower than that of the cliché100.

After transferring the colored ink filled in the cliché100onto the printing roll128, the ink pattern127formed on the printing roll128is moved to a stage150on which a substrate130is disposed. The ink patterns127of R, G and B colored inks123are applied onto the substrate130by rotating the printing roll only once across the substrate. The ink patterns127applied to the substrate130form the R, G and B color filters127a˜127c. The temperature of the substrate130can be controlled by installing a heater (not shown) in the stage150to make the ink patterns detach from the printing roll128and to make the ink patterns attach easily onto the substrate130easily. The heaters (not shown) is installed on the cliché100, the printing roll128, and on the stage150should be independably controllable and also should be able to maintain even temperatures throughout entire areas of the cliché100, the printing roll128and the stage150.

FIG. 3Eshows color filters of R, G and B colors127a,127band127cformed on the upper substrate130of an LCD device according to the above described processes. Generally, the color filters are formed by combining an ink jet method with a printing method to prevent ink from being wasted and to simplify the processes. As described above, the R, G and B color filters are formed sequentially one after another across the substrate without stopping to repeat the process for another color.

As shown inFIG. 3F, a black matrix131is deposited and patterned on the substrate130to be in between the R, G and B color filters127a,127band127c. The black matrix131can be a resin, a metal or some other opaque material. In the alternative, the black matrix131could be formed on the substrate130prior to the printing of the R, G and B color filters127a,127band127c. If the black matrix131is formed on the substrate130first, the R, G and B color filters127a,127band127care printed on the substrate such that they are aligned within the black matrix.

As described above, according to the method for fabricating color filter of the present invention, the R, G and B color inks are filled on the groove of cliché in the ink jet method, and after that, the inks are printed on the substrate at once in the printing method, and thereby, the repeated processes in the related art can be omitted to improve producing efficiency. The colored inks can be filled in concurrently by the ink jet method, and thereby, the material cost can be reduced and a competitive price can be ensured.