Patent Application
20080018841
In
As illustrated in
As the reaction gas 160 from the MFC 140 flows downward through the nozzle 120, a high voltage is applied between the power electrode 135 and the ground electrode 130, thereby generating a glow discharge, which energizes the flowing reaction gas 160 into a plasma state. As used herein, “plasma state” refers to a net neutral state of ions or electrons generated when energy is applied to neutral atoms or molecules. The energy of a plasma state is much higher than that of a gaseous state, and matter that is in a plasma state contains a large amount of reactive radicals, which enable the surface of a subject to be etched thereby. As the reaction gas 160 passes further through the nozzle 120, the density of the plasma increases. As the reaction gas 160 moves away from the lower ends of the power electrode 135 and the ground electrode 130, the density of the plasma decreases, thereby decreasing the amount of radicals present.
The substrate 110 disposed below the nozzle 120A includes a conductive film 112 and the alignment film 114, which are sequentially formed thereon. The substrate 110 may be a Thin Film Transistor (TFT) substrate or a color filter substrate of an LCD. The alignment film 114 may be an inorganic alignment film, and the conductive film 112 may be a common voltage terminal of the TFT substrate or a common electrode of the color filter substrate.
The TFT substrate includes a plurality of gate lines, data lines, and pixel electrodes. The gate lines extend in a row direction and are responsible for the transmission of gate signals, and the data lines extend in a column direction and are responsible for the transmission of data signals. The pixel electrodes are connected to switching devices connected to the gate lines and the data lines.
The color filter substrate is disposed above the TFT substrate. The color filter substrate includes red, green, and blue color filters corresponding to respective ones of the pixel electrodes so that a respective color can be displayed in each pixel. A common electrode made of a transparent conductive material, such as Indium Tin Oxide (ITO) or Indium Zinc Oxide (IZO), is disposed over the color filters.
An LCD typically includes a TFT substrate and a color filter substrate as described above, as well as a layer of a liquid crystal material having dielectric anisotropy interposed between the TFT and the color filter substrates. The liquid crystal layer functions to adjust the transmittance of light passing through the liquid crystal layer by changing the arrangement of liquid crystal molecules, which is effected by applying a voltage thereto from an external source. An alignment film for achieving a desired orientation of the molecules of the liquid crystal layer is disposed on each of the TFT and the color filter substrates.
A common voltage is applied to a common electrode of the color filter substrate via a common voltage terminal of the TFT substrate. To apply the common voltage, a transfer electrode is formed that connects the common electrode of the color filter substrate and the common voltage terminal of the TFT substrate.
However, since an alignment film is present between the common voltage terminal of the TFT substrate and the transfer electrode, it is necessary to etch away a selected portion of the alignment film formed on the common voltage terminal so that the common voltage terminal can contact the transfer electrode. Also, since an alignment film is present between the common electrode of the color filter substrate and the transfer electrode, it is likewise necessary to etch away a selected portion of the alignment film formed on the common electrode so that the common electrode can contact the transfer electrode.
When the alignment film etching apparatus 100 is in operation, atmospheric pressure plasma generated from the reaction gas 160 is sprayed from the nozzle 120 onto the upper surface of the alignment film 114 disposed below the nozzle 120 so as to selectably etch the surface of the alignment film 114, thereby forming an etched region 116 through which a selected portion of the underlying conductive film 112 is exposed. The conductive film 112 may be a transparent conductive film made of, e.g., ITO, IZO, or the like, or alternatively, a metal wire.
When the substrate 110 is a color filter substrate, the conductive film 112 may be a common electrode formed over the color filters. When the substrate 110 is a TFT substrate, the conductive film 112 may be a common voltage terminal formed on the TFT substrate to apply a common voltage to a common electrode.
The alignment film 114 may comprise an inorganic alignment film material. The alignment film 114 may be made of an inorganic material including silicon, e.g., amorphous hydrogenated silicon, silicon carbide (SiC), silicon oxide (SiOx), silicon nitride (Si3N4), or like materials. Such an inorganic alignment film can be formed by a so-called “thin film deposition process” using, e.g., sputtering, chemical vapor deposition, or the like, which is more advantageous in terms of productivity than a conventional printing method using a resin printing plate. Preferably, the alignment film 114 is made of silicon oxide (SiOx).
The alignment film 114 is easily etched by atmospheric pressure plasma generated from the reaction gas 160, whereas, the conductive film 112 disposed below the alignment film 114 is not easily etched by the atmospheric pressure plasma. That is, if the reaction gas 160 is selected such that the etching selectivity of the alignment film 114 with respect to the conductive film 112 is high, no etching damage will occur to the conductive film 112 disposed below the alignment film 114 during the etching of the alignment film 114.
In one exemplary embodiment, the reaction gas 160 may comprise a SF6-containing gas. For example, a mixture of gaseous N2 and SF6 in a ratio of from about 5:1 to about 50:1 may be used.
The plasma discharged from the lower end of the nozzle 120 of the alignment film etching apparatus 100 tends to disperse in all directions due to the low directionality of the nozzle. Thus, in order to etch a desired portion (referred to herein as an etched region 116) of the alignment film 114 using atmospheric pressure plasma without using a mask, it is necessary to control both the dimension of the nozzle 120 of the alignment film etching apparatus 100, and the distance between the nozzle 120 and the alignment film 114, and accordingly, these two dimensional parameters are deemed to be of primary importance, for the reasons discussed below.
An exemplary embodiment of a method for etching an LCD alignment film 114 so that the etched region 116 has relatively vertical sidewalls, i.e., a keen or sharp sidewall profile in the direction of the thickness of the film, is described below with reference to
Referring to
In order to maintain the ratio of the diameter B of the etched region 116 to the diameter A of the nozzle 120 to between about 1-2.5, the distance C between the nozzle 120 and the alignment film 114 should be controlled to be between about 0.25-0.75 mm. If the distance C between the nozzle 120 and the alignment film 114 is less than 0.25 mm, arcing may occur between the nozzle 120 and the alignment film 114. On the other hand, if the distance C between the nozzle 120 and the alignment film 114 is greater than about 0.75 mm, the etched region 116 will have an excessively broad sidewall profile.
Another exemplary embodiment of a method for forming an alignment film of a LCD in accordance with the present invention is described in detail below with reference to
Referring to
That is, it is preferable that the alignment film 114 in the active area adjacent to an etched region 116 has a relatively sharp sidewall profile, and is acceptable that the alignment film 114 in the periphery area adjacent to the etched region 116 has a broad profile, since the latter region is subsequently discarded. To achieve this desirable end, the tilt angle θ of the nozzle 120 with respect to the upper surface of the substrate 110 should be controlled to be between about 1-45 degrees, and more preferably, between about 5-25 degrees. If the tilt angle θ of the nozzle 120 exceeds about 45 degrees, a damage region D of the alignment film 114 in the active area, as illustrated in
Although the nozzle 120 is inclined at a selected angle relative to the substrate 110, the distance C between the nozzle 120 and the alignment film 114 should preferably still be controlled to be about 5 mm or less. Here, the distance C between the nozzle 120 and the alignment film 114 refers to the distance between the alignment film 114 and the center of the lower end of the annular nozzle 120. In this case, if the distance C between the nozzle 120 and the alignment film 114 exceeds about 5 mm, the plasma P flowing from the nozzle may disperse excessively and result in the alignment film 114 having an undesirably broad or sloping sidewall profile, such as that illustrated in
As described above, the diameter B of the etched region 116 should be controlled to be between about 1-2.5 times the diameter A of the nozzle 120. For example, when the diameter A of the nozzle 120 is about 1 mm, the diameter B of the etched region 116 will be about 1-2.5 mm. If the diameter B of the etched region 116 exceeds 2.5 times the diameter A of the nozzle 120, the plasma P may disperse excessively from the nozzle, resulting in the alignment film 114 in the active area, as well that in the periphery area, being etched with an undesirably broad profile. When the ratio of the diameter B of the etched region 116 to the diameter A of the nozzle 120 is maintained at about 1-2.5, as illustrated in
An exemplary embodiment of a method for manufacturing a TFT substrate and a color filter substrate of an LCD, each having an alignment film formed thereon using the above-described alignment film etching apparatus and methods is described below with reference to
Referring to
In the particular exemplary embodiment of
A TFT substrate and a color filter substrate respectively prepared by the TFT substrate manufacturing process (S310) and the color filter substrate manufacturing process (S310) are conjointly subjected to the liquid crystal cell process (S320). The liquid crystal cell process (S320) includes forming alignment films and seal lines on respective ones of the two substrates to define a plurality of unit liquid crystal cells, dripping a liquid crystal material into the unit liquid crystal cells, assembling the two substrates together, and cutting the resultant substrate assembly into individual unit liquid crystal cells using one of various possible cutting tools to yield a plurality of individual LCD panels.
After the liquid crystal cell process (S320), the module process (S330) is performed. In the module process (S330), driving circuits for supplying electrical signals to the liquid crystal cells are attached to the LCD panels.
Following is a more detailed description of the process flow of the liquid crystal cell process (S320) of
In the forming of the inorganic alignment films (S321), alignment films are respectively formed on the pixel electrodes of a TFT substrate and on the common electrode of a color filter substrate. The alignment films are formed at selected thicknesses over the entire surface of each of the TFT and color filter substrates. As a result of the presence of these alignment films on the two substrates, the molecules of the layer of liquid crystal material disposed between the two substrates are uniformly oriented, thereby ensuring uniform display characteristics over the entire screen area of the display.
The alignment films must have good adhesion property for adhering to a surface made of an electrode material (e.g., ITO), and a film uniformity of 1,000 Å or less at temperatures of 200° C. or less. Also, the alignment films must have sufficient chemical stability so as not to react with the liquid crystal material, must not function as electrical charge trapping media, and must have sufficiently high resistivity so as not to affect the operation of the liquid crystals. In addition, the physical properties of the alignment films must not be degraded when exposed to strong UV light for long periods of time. In view of these required characteristics, the alignment films may be inorganic alignment films. The alignment films are preferably made of amorphous hydrogenated silicon, silicon carbide (SiC), silicon oxide (SiOx), silicon nitride (Si3N4), or the like. The alignment films are more preferably made of silicon oxide (SiOx). Alignment films made of silicon oxide may be formed using sputtering or chemical vapor deposition techniques.
Depending on the process conditions, the respective surface of the alignment films can also be aligned using an additional ion-beam or an atomic-beam process.
After the alignment film formation (S321) is completed, the alignment films of the TFT substrate and the color filter substrate corresponding to transfer electrodes are etched to expose the underlying conductive films (S322). To achieve this, the alignment films are patterned using atmospheric pressure plasma generated by an alignment film etching apparatus of the type illustrated in
Next, a transfer electrode 440 is formed on the exposed portions of the conductive films (S323). Referring again to
Next, a seal line is formed along inside edges of the TFT substrate relative to the transfer electrode to firmly attach the TFT substrate and the color filter substrate together and to define a space, or cell gap, between the two substrates for receiving the liquid crystal material (S324). Referring again to
In the exemplary embodiment illustrated, the seal line 450 may comprise a mixture of a sealant, i.e., an adhesive used for attaching the TFT and color filter substrates to each other, and a plurality of rigid spacers for spacing the two substrates apart by a selected distance so as to define a uniform liquid crystal receiving space, or cell, between the two substrates. In order to maintain a uniform cell gap between the TFT substrate and the color filter substrate, the spacers are disposed not only in the seal line, but also in active areas of the LCD panels.
Next, a liquid containing liquid crystals is dripped onto the color filter substrate (S324) so as to form a uniform layer of the liquid crystal material between the two substrates. Additionally, it should be understood that, while the exemplary embodiment has been described in terms of a liquid crystal dripping technique, the present invention is not limited thereto, and the liquid crystal material may also be injected between the TFT and color filter substrates using a vacuum pressure injection technique.
Next, the TFT substrate with the seal line and the color filter substrate with the liquid crystals are aligned and mated with each other and treated with UV light or heat to cure the seal line so as to fix and seal the TFT substrate and the color filter substrate (S325) to each other. An allowance error for alignment of the two substrates is determined by a design margin of the two substrates. Referring to
Next, the resultant mother glass substrate assembly is cut into individual LCD cells to produce individual LCD panels (S326). To achieve this, a diamond wheel or the like may be used.
Next, an edge-polishing process may be also be performed on the substrates. In the edge-polishing process, side and edge portions of the TFT and color filter substrates are polished using, e.g., a diamond polishing stone rotating at a high speed.
Then, polarization substrates are respectively attached to an exterior surface of each of the two LCD substrates. The thus-completed LCD panels are subjected to an inspection process for inspecting the electro-optical characteristics and image quality of the panels.
The thus-completed LCD panels are then subjected to the module process (S330). The module process (S330) includes mounting driving integrated circuits (ICs) on the LCD panels, attaching Printed Circuit Boards (PCBs) to the LCD panels, and assembling the LCD panels with backlight units using mold frames, chasses, and other mechanical and structural elements.
For example, the driving ICs can be mounted on the LCD panels using Tape Automated Bonding (TAB) technology, Chip On Board (COB) technology, or Chip On Glass (COG) technology. The PCBs include multi-layered circuit devices and are electrically connected to the driving ICs via Flexible Printed Circuits (FPCs), or the like, to constitute the driving circuit units of the LCDs. The PCBs are formed using Surface Mount Technology (SMT), or the like, and then attached to the LCD panels. The LCD panels with the driving ICs and the PCBs are then referred to as “LCD panel assemblies.”
The individual LCD panel assemblies, together with their respective, separately formed backlight units, are then installed in respective mold frames and chasses to complete the LCDs.
In accordance with the exemplary embodiments illustrated and described herein, an alignment film is patterned to expose a common voltage terminal of a TFT substrate and a common electrode of a color filter substrate contacting a transfer electrode. However, it should be understood that the present invention is not limited to the particular embodiments illustrated and described. The present invention's method for patterning an alignment film can also be applied to any process for exposing a thin film disposed below an alignment film. For example, the alignment film patterning process of the present invention can also be applied to a process for exposing the ends of gate lines or data lines disposed below an alignment film. Since the ends of the gate lines or data lines must be connected to driving ICs, it is necessary to partially etch the alignment film in areas above the ends of the gate lines or the data lines, and the present invention provides an easy, efficient and accurate method for doing this.
Hereinafter, an alignment film etching apparatus according to still another exemplary embodiment of the present invention is described in detail with reference to
Referring to
A barrier 170 for improving the straightness of the flow of atmospheric pressure plasma is formed at a lower end of the dielectric nozzle 120. In other words, the barrier 170 extends from the lower end of the dielectric nozzle 120 toward a substrate 110 in a shape of, for example, an annulus. Since the barrier 170 serves to prevent the plasma discharged from the nozzle 120 from dispersing outwardly in all directions from the nozzle 120, the inner diameter D of the barrier 170 is preferably larger than the inner diameter A of the nozzle 120. The barrier 170 may be made of a non-metallic material that does not react with the plasma, for example, a dielectric material or a polymeric material. In order to prevent the barrier 170 from causing scratches to the substrate 110, the barrier 170 is preferably made of a polymeric material, for example, PTFE (Polytetrafluoroethylene), PEEK (Polyether ether ketone), or the like.
The barrier 170 is fixed to the lower end of the nozzle 120 by a buffer driver 180, and the buffer driver 180 is operative to adjustably move the barrier 170 up and down relative to the lower end of the nozzle 120.
As discussed above, the plasma discharged from the alignment film etching apparatus 105 tends to disperse in all directions due to low directionality. Thus, when the barrier 170 at the end of the nozzle 120 of the alignment film etching apparatus 105 is used with the apparatus, a desired portion (referred to herein as an etched region 116) of the alignment film 114 can be etched by an atmospheric pressure plasma without using a mask.
The operation of the barrier 170 to achieve directionality of the plasma is described below with reference to
When the substrate 110 has not yet been loaded into the lower portion of the alignment film etching apparatus 105, the buffer driver 180 moves the barrier 170 upward so that it is disposed in a standby state, as illustrated in
Next, when the substrate 110 has been loaded into the lower portion of the alignment film etching apparatus 105, the buffer driver 180 moves the barrier 170 downward, i.e., toward the substrate 110, as illustrated in
As the distance between the nozzle 120 and the alignment film 114 increases, the atmospheric pressure plasma P tends to disperse outwardly from the nozzle 120 in all directions. That is to say, a predetermined diameter B of the etched region 116 becomes larger than the diameter A of the nozzle 120. In order for the etched region 116 to have reproducibility, i.e., to have a predetermined diameter, the area in which the atmospheric pressure plasma P is formed between the nozzle 120 and the substrate 110 is preferably surrounded by the barrier 170. Accordingly, the diameter B of the etched region 160 can be controlled so as to be smaller than the diameter D of the barrier 170.
Further, when the atmospheric pressure plasma P is surrounded by the barrier 170, the atmospheric pressure plasma P becomes more concentrated, thereby increasing the etch rate.
As described above, in the exemplary alignment film etching apparatus according to the present invention, since an inorganic alignment film is used, any degradation of the alignment film due to the effects of a backlight unit or other peripherals is prevented. Furthermore, since the alignment film etching apparatus uses an atmospheric pressure plasma without needing a mask, the time required to manufacture LCDs is reduced and the number of devices required to manufacture the LCDs is minimized. In addition, the area in which the atmospheric pressure plasma is formed can be controlled very accurately by forming a barrier between a lower end of the nozzle of the apparatus and the substrate being processed. Additionally, alignment films having sharp sidewall profiles can be patterned by appropriately adjusting the diameter of the nozzle of the alignment film etching apparatus and the distance between the nozzle and the alignment film. Further, alignment films having sharp sidewall profiles can also be patterned by inclining the nozzle of the alignment film etching apparatus to a selected angle relative to the patterned surface of the alignment film.
By now, those of skill in this art will appreciate that many modifications, substitutions and variations can be made in and to the methods for forming LCD alignment films of the present invention and the LCDs manufactured thereby without departing from its spirit and scope. In light of this, the scope of the present invention should not be limited to that of the particular embodiments illustrated and described herein, as they are only exemplary in nature, but instead, should be fully commensurate with that of the claims appended hereafter and their functional equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2006-0069260 | Jul 2006 | KR | national |
| 10-2006-0130209 | Dec 2006 | KR | national |
