JP2000513456A - Plasma addressed liquid crystal display - Google Patents

Abstract

(57) Abstract: A flat display device of the PALC type in which an electronic array of data elements, in particular, a plasma channel is defined by an organic material, preferably a polyimide material. A protective layer is provided on the polyimide wall to prevent deterioration. The separation electrode portion is provided on the opposing surface of the wall. A preferred method of manufacture is to provide a thick layer of polyimide material, provide a thin layer of photoresist thereon, pattern the photoresist, and then use the photoresist to pattern the polyimide layer into the desired wall configuration. I do. Next, the wall is covered with a thin dielectric sheet-like member to form a plasma channel.

Description

Description: FIELD OF THE INVENTION The present invention relates to a plasma addressed liquid crystal display panel, commonly referred to as a plasma addressed liquid crystal (PACL) display. BACKGROUND OF THE INVENTION Such an apparatus is referred to as "ITO" because indium-tin oxide is typically used, and has a first substrate on which parallel transparent column electrodes on which color filters are deposited are deposited; Correspond to the display rows intersecting all of the ITO columns filled with a low pressure ionizing gas such as helium, neon and / or argon, comprising parallel sealed plasma channels sealed by a thin transparent dielectric sheet, these channels having A second substrate which includes a separated cathode and an anode electrode and generates a plasma by ionizing a gas, and a liquid crystal material (LC) arranged between these substrates in a sandwich shape. This structure functions similarly to an active matrix liquid crystal display in which a plasma channel is disposed at each pixel location instead of a thin film transistor switch to act as a row switch and to selectively address a row of LC pixels. . In operation, successive lines of the data signal representing the image to be displayed are sampled at row locations and sampled data voltages are applied to the respective ITO columns. All but one of the row plasma channels are deionized or non-conductive. The plasma in one of the ionized select channels becomes conductive, effectively establishing a reference voltage on the adjacent side of the pixel row of the LC layer, thereby charging each LC pixel to the column potential supplied with the data signal. The ionized channel turns off to separate the charge on the LC pixel and store the data voltage over the frame period. When the next row of data appears in the ITO column, only the next plasma channel row is ionized, storing the data voltage in the next row of LC pixels, and so on. As is known, the attenuation of each LC pixel with respect to backlight or incident light is a function of the stored voltage across the pixel. A more detailed description of such points is unnecessary. The reason is that the construction, manufacture and operation of such a PACL device are described in the following US patents and publications: Buzaki et al., "16 Inch Full Color Plasma Addressed Liquid Crystal Display", Digest of Technical Paper, Paris, 1993, SID In. t., Symp., Soc. for Info. Displ. pp. This is because it is described in 883-886. SUMMARY OF THE INVENTION As is evident from the foregoing, a panel is an electronic array of data elements in the form of pixels, and a plasma channel selectively ionizes a gas sequentially by sequentially addressing the electrodes in the channel. Act as an addressing structure for the array to address one or more data elements. FIG. 2 shows a cross section of a plasma addressed liquid crystal display device described in the 1993 SID Digest. In the method described in the above publication for forming a plasma channel, a flat glass substrate is chemically etched to form parallel grooves defined by spaced apart ridges or mesas and to have a thickness of 30 mils on top of the mesas. A thin dielectric cover sheet in the range of −50 μm is adhered. In general, forming channels of uniform dimensions by forming plasma channels, typically of the order of 100-150 μm deep, by wet etching is problematic and time consuming. The problem of uniform dimensions is due to such factors as etch rate, channel wall roughness, local defects in the mesa, and non-uniformity of the structure separating the multiple channels. To make the cover sheet of the plasma channel portion more rigid, US Pat. No. 5,214,421 deposits electrodes on a flat bottom plate and etches back the top plate to form a semi-cylindrical channel (shown in FIG. 2). (Inverted version), and the residual glass at the top of the channel is made sufficiently thin to allow addressing of adjacent LC materials. However, because of the circular curve of the top plate, the thickness of the glass between the plasma discharge and the LC material, and thus the voltage drop across the LC material, varies significantly for each pixel. In practical situations, this reduces the number of gray levels in the dedisplay. In U.S. Pat. A structure in which a thin dielectric sheet is attached is described. This US patent does not describe a method for forming such ribs, and the use of screen printing for forming such ribs is described in EP-A-500 085 A2. It is an object of the present invention to provide an improved channel plate for an electronic array, especially for a flat display device. It is another object of the present invention to provide an improved plasma addressed display. It is still another object of the present invention to provide a method for manufacturing a plasma channel of a PALC display. According to a first embodiment of the present invention, a channel plate of an electronic array, in particular, a flat display device, is arranged on and spaced apart from a substantially transparent substrate and a plurality of mesas that planarize and define the channels. A thin dielectric sheet-shaped member. Each of the mesas is formed by a patterned layer of an organic material. Preferably, the organic material is a polyimide material. Each channel is provided with a separation electrode layer. Preferably, electrodes are provided on opposing surfaces of each pair of mesas that define a channel. In a preferred example, the display device is a PALC display device, and a plasma channel or a channel plate of the PALC display device is formed by a combination of a substrate, a separated polyimide wall or a mesa, and an upper thin dielectric sheet member. In a second embodiment of the present invention, the polyimide mesas are covered by one or more thin protective layers. Preferably, the protective layer is substantially transparent, electrically insulated and formed by a vapor deposition technique. This polyimide is commonly used as a protective layer in the manufacture of certain semiconductive devices. Such devices typically do not operate in an exhaust vessel, but operate in a gas to be activated and generate a plasma. Therefore, when polyimide is applied to a semiconductor device, a protective layer is usually not necessary for a polyimide material. In contrast, for application to the manufacture of channel plates for PALC displays, polyimide mesas are present in a gas-filled enclosure so that the composition of the gas can purely reduce the operating performance of the plasma. In this case, the deterioration of the vapor from the polyimide material can affect the operation of the channel plate due to the deterioration. By providing a protective layer on the polyimide mesa, the polyimide mesa is protected from ion bombardment when plasma is generated, thus preventing the inside of the plasma chamber from deteriorating. In a preferred embodiment of the method of the invention, the substrate is coated with a thick layer of polyimide, and then the thick composition is coated with a thin layer of photosensitive resist. Next, the photoresist is exposed to subject the coated substrate to a development treatment, and then the unexposed photoresist portions are removed, leaving the patterned photoresist at the proper position. The lower polyimide portion is then selectively removed to form a patterned polyimide layer, after which the remaining photoresist material is removed. Next, a protective layer is applied to the patterned polyimide layer and electrodes and a cover plate are provided. The main advantage in this case is that the channel walls are not roughened and the process is time-saving over known methods of forming the channel plate using wet chemical etching. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing the structure of a conventional flat panel display device, FIG. 2 is a perspective view showing a part of the structure of a conventional PALC display device, and FIGS. FIG. 7 is a cross-sectional view showing various steps of manufacturing a patterned polyimide layer used in manufacturing a plate. FIGS. 7 to 9 show still other various types of the patterned polyimide layer used in manufacturing a channel plate according to the method of the present invention. FIG. 10 is a cross-sectional view showing a partial structure of a channel plate of the present invention used in a PALC color display device. FIG. 1 shows a typical PALC display and a flat panel display representing operating electronics. In FIG. 1, the flat panel display comprises a display surface 12, which is formed by a rectangular planar array of usually identical data storage or display elements 16 spaced apart from each other by a predetermined distance in the vertical and horizontal directions. Including patterns. Each display element of this array represents a superimposed portion of a thin narrow electrode 18 generated in a vertical column and a narrow narrow channel 20 arranged in a horizontal row. (Hereinafter, this electrode 18 is sometimes referred to as a "column electrode.") Each display element 16 in a row of channels 20 represents one line of data. The dimensions of the rectangular display element 16 are typically determined by the widths of the column electrodes 18 and the channels 20. The row electrodes 18 are deposited on the major surface of the first non-conductive transparent substrate 34 (FIG. 2) and allow the channel rows to be typically incorporated into the second transparent substrate 36. It will be apparent to those skilled in the art that certain systems, such as direct-view or projection-type reflective displays, say that only one substrate is optically transparent. The column electrode 18 receives an analog voltage type data drive signal generated on the parallel output conductor 22 'by various ones of the output amplifier 23 (FIG. 2) of the data drive circuit 24, and the channel 20 is a data strobe means, that is, a strobe circuit. A voltage pulse type data strobe signal ヲ generated at the parallel output means 26 ′ by various output amplifiers 21 (FIG. 2) is received. Each channel 20 includes a reference electrode 30 (FIG. 2), which supplies a reference potential, such as a common ground voltage, to each channel 20 and data strobe 28. To enhance the image of the entire area of the display surface 14, the display system 10 uses a scan control circuit 32 that cooperates with the functions of the data drive circuit 24 and the data strobe circuit 28 to display the entire display element 16 of the display panel 12. The columns are addressed row by row in the row scan state as described above. The display panel 12 can use various types of electro-optic materials. For example, when a material that changes the polarization state of an incident light beam is used, the display panel 12 is located between a pair of polarizing filters, and these filters cooperate with the display panel 12 to control the light passing through the filters. Change the brightness. However, when a scattering liquid crystal cell is used as the electro-optic material, it is not necessary to use a polarizing filter. All such materials or material layers that attenuate transmitted or reflected light in response to a voltage across it are hereinafter referred to as electro-optical materials. Since liquid crystal materials are currently the most common example, the detailed description will be made with liquid crystal materials, but it is clear that the present invention is not limited thereto. A color filter (not shown) can be located within the display panel 12 to generate a multiple color image of controllable color intensity. For projection display, coloring can also be performed using three separate single color panels 12, each controlling one primary color. FIG. 2 shows a variation of PALC of such a flat display panel using a liquid crystal material. FIG. 2 shows only three of the column electrodes 18. The row electrode 20 is constituted by a plurality of elongated sealed parallel channels (FIG. 2) below a layer 42 of liquid crystal material. Each of the channels 20 is filled with an ionized gas 44, which is typically sealed with a thin dielectric sheet 45 of glass, and the first and second channels extend over the entire length of each channel in the interior channel surface. A second spaced apart elongated electrode 30, 31 is included. The first electrode 30 is grounded and is commonly referred to as an anode. The second electrode 31 is called a cathode. The reason is that this supplies a negative strobe pulse to the anode electrode sufficient to emit electrons from the cathode 31 and ionize the gas. As described above, each channel 20 is sequentially gas ionized by a strobe pulse to form a plasma and ground line connection to the pixel rows of the liquid crystal layer 42 described above. After the strobe pulse ends and deionization is performed, the next channel is strobed and turned on. Since each column electrode 18 intersects every pixel column, only one plasma row connection is made at a time to prevent crosstalk. PALC devices are typically manufactured by providing first and second substrates 34, 36 as described in a 1993 SID Digest article. The first substrate 34 includes a glass panel on which the ITO column electrodes 18 are deposited, and then performs a color filter process on the electrodes to form RGB strips (not shown), and further performs a black surrounding process and a liquid crystal alignment process. Is formed. Further, the second electrode 36, which is also a glass panel, is subjected to a masking process and an etching process to form a channel 20, then a plasma electrode material is deposited, and a masking process and an etching process are performed to form a cathode 31 and an anode 30. I do. The thin dielectric glass microsheet 45 is then sealed across the channel ridge 50, the channels 20 are sealed off, and the channels are evacuated to remove any low pressure ionized gas, such as helium and / or neon, or other gases. And then seal off. Next, the liquid crystal on the exposed surface of the microsheet 45 is aligned. Next, the two assembled substrates are separated from each other and arranged opposite to each other, the two liquid crystal alignment surfaces, the liquid crystal material 42 introduced into this space, and the electric connection portion where the column electrode 18 and the plasma electrodes 30 and 31 are formed. Assemble into a panel having In accordance with the present invention, the channel plate is comprised of substantially vertical mesa structures forming each flat sidewall, which are widely used by those skilled in the art of semiconductors in organic materials, particularly intermetal dielectric applications. It is constituted by a polymer dielectric such as a polyimide material. Such polyimide materials are preferred because they have a high dielectric constant and form a solution that is easily supplied by standard spin coating, and a variety of solutions that are readily available from many suppliers. This is because it has a form. However, by (a) forming a dielectric coating or layer of the desired thickness, (b) curing as by baking, (c) usually dissolving, softening in a suitable solvent, or etching by dissolution Generally, any organic material that can be patterned can be used. If such materials are photosensitive, individual materials can be used for patterning. In addition, patterning can be performed by a physical press, as in the case of using a CD. The channel plate structure in a preferred method is formed as follows. The starting point (FIG. 3) is a flat bottom plate 36, for example of glass, which forms a substantially transparent substrate for the plasma channel. A layer 38 of a polyimide material is conventionally deposited on the bottom plate 36 to a desired thickness. The preferred thickness of the PALC coating is 100-150 μm. Depending on the viscosity of the polyimide solution, this layer can be formed to a desired thickness in one or several layers by spin coating, or by spray coating, or by any known coating. On this polyimide layer 38, a layer of a photoresist 40 is provided. This photoresist layer is composed of many commercially available resists, such as 2P, ie, a diacrylic resist, and its thickness can be, for example, several (1-3) μm. The photoresist layer is then exposed to photosensitive radiation through a suitable mask 42, and then the photoresist 40 is subjected to standard development throughout. If a positive photoresist is used, the exposed photoresist portion 44 is depolymerized and softened by radiation that can be any radiation to which the photoresist is exposed, such as ultraviolet light, and the softened portion is easily removed (FIG. 4) Leave unexposed photoresist portions 46. Next, the polyimide region under the remaining photoresist portion 44 is eroded, softened or dissolved using a second developer solution suitably selected for the polyimide material, resulting in the photoresist being eroded as shown in FIG. The polyimide region under the hole 44 is also removed, thus leaving the patterned photoresist layer 46 above the similarly patterned polyimide layer 48. Any of a number of known suitable developer solutions can be used for the photoresist, and any of a number of known suitable developer solutions can also be used for the polyimide residue. Many developing solutions are already commercially available and can be easily obtained. Next, the remaining photoresist material 46 is removed with any suitable solvent (FIG. 6). After this removal step, the patterned polyimide layer 48 is cured by subjecting the substrate to a bake step at a temperature of, for example, about 400 ° C., known as “hard bake”. This process substantially thermally inactivates the polyimide material. FIGS. 3-6 illustrate a series of steps commonly used to form any desired pattern of polyimide walls or mesas, whether regular or irregular, the pattern of the mesas of a PALC display is generally very regular, All of the mesas have the same height, the same width, and the same pitch (equal spacing). FIG. 7 shows an intermediate (semi) product obtained after the sequential manufacturing steps of FIGS. 3-6, which is used particularly for the manufacture of channel plates for PALC displays. The assembly includes a substrate 36 having upright baked polyimide mesas or walls 50 as described above. A preferred wall height is approximately 80-150 μm, depending on the pixel size. This substrate is coated with a thin layer of protective material 52 by vapor deposition (FIG. 8). Suitable materials can be those commonly used in the electronics arts, such as glass, silicon oxide, silicon nitride, and aluminum oxide. The preferred thickness of the protective layer 52 is in the range of 20 nm to 10 μm. Any deposition technique can be used, such as chemical vapor deposition or sputtering or evaporation and generally at a temperature compatible with these materials. If the protective layer 52 is applied anywhere, this can eliminate the need for other photolithographic steps, and therefore the protective layer needs to be substantially transparent. The reason is that in the usual means of operating a PALC display, the light source is arranged on one side of the PALC display and the user observes the image from the other side, and this image is reflected by the addressed LCD imager to the incident light. This is because it is formed by attenuation. The protective material having the above-mentioned thickness range needs to be sufficiently transparent to white light. Also, other materials that can be transparent and that can protect the polyimide material from degradation from plasma can be substituted. After providing the protective layer 52, an electrode 54 can be provided on each channel by any known means, and preferably on the facing surface of the polyimide mesa 50 by any known means. The metal layer of the electrode, typically of copper and approximately 2-10 μm thick, can be patterned using photolithography. In the above-described second and third conventional examples, the configuration is described in which the flattening of the side wall portion of each channel is generally vertical and linear, and the electrodes are formed on the opposing surface of the vertical side wall by various processes including generally plasma etching. are doing. The plasma etching process described in the third conventional example is a preferable technique because it does not require an additional photolithography process (self-alignment process). The method of the present invention involves blanket deposition of a suitable electrode material and also includes an anisotropic plasma etching step, whereby the anisotropic plasma etching causes the electrode material to be located everywhere except at the bottom vertical section 54 as shown in FIG. Is preferably removed by etching. The last step of the process consists in gluing a thin flat dielectric sheet 56 of glass, for example, to the top of the mesa on the protective layer 52, thus forming a plurality of channels 58. The active channel 58 is formed by side walls 50, 52, a substantially planar substrate portion covered with a protective layer, and adjacent elongated grooves each planarized by a substantially planar top wall 64 opposite the bottom plate. The top sheet 56 is sealed along the top of the sidewall, as is known, for example by a molten glass frit or by anodic bonding, so that a sealed plasma channel 58 can be formed. In general, the resistance of polyimide to extremely high temperatures is limited. Therefore, when a melt frit is used, it is preferable that the temperature is not set to approximately 450 ° C. or higher. Alternatively, the edges (not shown) of the top sheet are sealed to the edges (not shown) of the bottom plate 36 to seal the structure and eliminate the need to seal individual channels. The reason is that a common gas is used for all the channels. The outer surface 66 of the top 56 is opposed to an LC layer (not shown). These channels are later filled with a gas suitable for the plate to generate as described above. The surface 52 of the protective layer shields the polyimide mesas from plate discharge and ion bombardment to prevent the organic polyimide material from contaminating the desired gas atmosphere. As noted above, the one shown in FIG. 10 shows a portion of a larger assembly. The reason for this is that typically a PALC display used for monitoring includes hundreds of column electrodes 18 and hundreds of plasma channels. All of the methods described in the above prior art examples are suitable for forming the remaining portion of the panel of the present invention. Another advantage of the present invention is that only one photolithographic step is required, as shown by mask 42 in FIG. The present invention relates to an electronic array of data elements including addressing, especially a flat display, a plasma-addressed display, such as a PALC display with small pitch channels for use in a computer monitor, workstation or TV set. It can be applied to all kinds. The polyimide material is an organic material suitable for forming the flattened wall of the channel of the channel plate, but the present invention is not limited to this. It can be replaced with other suitable organic materials. For example, a photoresist that can be developed in a wet or dry environment after exposure can be used. The preferred embodiment embodiment of FIG. 10 is a flattened wall having a width of approximately 20-50 μm, a height of approximately 50-160 μm, and a pitch of approximately 200-500 μm. Also, the dimensions in the drawings are not to scale and, in particular, the channels are enlarged. Further, although the channels of the substrate are typically straight, other means such as serpentine can be used. The present invention is not limited to the above-described example, and various modifications and changes can be made without departing from the scope of the invention.

────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Bruchmans Adrians El Ye             ー             Netherlands 5656             Fen Prof. Holstrahn 6 (72) Inventor Broninck Jacob             Netherlands 5656             Fen Prof. Holstrahn 6 (72) Inventor Khan Baba Ali             Netherlands 5656             Fen Prof. Holstrahn 6 (72) Inventor Quake Karel Herbert             Netherlands 5656             Fen Prof. Holstrahn 6

Claims (1)

[Claims] 1. It comprises elongated channels formed in a substrate and electrode surfaces for each of these channels.   In addition, a thin sheet-shaped member is placed on the flat wall defining the channel of the insulating material of the substrate.   An electronic array structure adapted to be provided comprising: a) said flat wall portion of an insulating material;   An electronic array structure, wherein the electronic array structure is made of a material. 2. The flat wall portion is made of a polyimide material.   Item 2. The electronic array structure according to Item 1. 3. The flat wall of the polyimide material is coated with a protective layer to prevent deterioration.   The electronic array structure according to claim 1, wherein: 4. Strip channel formed by substantially opposing flat walls on a substantially transparent substrate   Plasma addressing liquid crystal (PALC) display device   In the channel plate, a) the flat wall portion is made of a polyimide material.   A plasma channel plate characterized by the above-mentioned. 5. Each of the flat walls is covered with a protective layer to prevent deterioration.   The electronic array structure according to claim 4, characterized in that: 6. The protection layer of each of the flat walls includes a counter electrode.   6. The electronic array structure according to 5. 7. The flat wall has a width of approximately 20-50 μm and a height of approximately 50-160.   μm and the pitch thereof is 2000-5000 μm.   An electronic array structure according to claim 5. 8. An electron beam between the first substrate having data electrodes and the channel plate according to claim 4.   A plasma addressed electronic array comprising a layer of optical material. 9. In manufacturing an addressing structure for an electronic array: by the following steps:     (A) providing a substantially transparent substrate,     (B) forming a plurality of separating walls of an organic material on the substrate to form a plurality of channels;   Define     (C) forming a separation electrode layer portion in each channel;   Of manufacturing an electronic array addressing structure. Ten. In performing the step (b);     (B1) forming a layer of a polyimide material on the substrate,   Forming a layer of resist on the layer,     (B2) irradiating and developing the resist layer to form a space between the separation walls;   An opening is formed in the place to be formed,     (B3) subjecting the exposed polyimide material to a treatment for removing   The material is removed to form a separation wall of the organic material.   A method of manufacturing an electronic array addressing structure according to claim 9. 11． After the step (b), a layer of a protective material is applied on the separation wall.   The method of manufacturing an addressing structure for an electronic array according to claim 10, wherein:   Law. 12． The layer of protective material is deposited by evaporation or sputtering or evaporation   The addressing of an electronic array according to claim 11, wherein   The method of manufacturing the structure. 13. Characterized in that a separation electrode layer portion is provided on a facing surface of the separation wall portion.   The method of manufacturing an electronic array addressing structure according to claim 12. 14. A layer of electro-optical material and an active portion of the layer coupled to the layer of electro-optical material   Data electrodes that apply voltage to each other and extend generally perpendicular to these data electrodes   A plurality of elongated plasma tubes for selectively switching on said electro-optic portion.   Channels, each with a separate elongated cathode and anode plasma electrode and ionization fill gas.   For closing a plasma channel comprising a source electrode on a side facing the data electrode   In manufacturing a plasma addressed electro-optical display with a sheet:     (A) providing a substantially transparent substrate,     (B) forming a plurality of spaced electrodes of a polyimide material on the substrate;     (C) depositing a protective material on the separation wall to prevent deterioration,     (D) forming a separated electrode layer portion on the protective layer;     (E) disposing a thin dielectric sheet member on the protective layer on the separation layer;   Of a plasma-addressed electro-optical display, characterized in that:   Method.