Abstract:
An object of the invention is to improve patterning accuracy while maintaining low cost, high throughput and a high degree of freedom of an optical material in a matrix type display device and a manufacturing method thereof. In order to achieve the object, surface features, including structural surface features, a desired distribution of water repellency, liquid repellency, hydrophilicity and lyophilicity, or a desired potential distribution are formed by utilizing first bus lines in a passive matrix type display device or utilizing scanning lines, signal lines, common feeder lines, pixel electrodes, an interlayer insulation film, or a light shielding layer in an active matrix type display device. A liquid optical material is selectively coated at predetermined positions by utilizing the surface features.

Description:
[0001]     This is a Division of Application No. 09/077,029 filed May 18, 1998, which in turn is a National Stage Application of International Application No. PCT/JP97/03297 filed Sep. 18, 1997, which claims priority to Japanese Patent Application No. 8-248087, filed in the Japanese Patent Office on Sep. 19, 1996. The disclosures of the prior applications are hereby incorporated by reference in their entirety. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of Invention  
         [0003]     The present invention relates to a matrix type display device and a manufacturing method thereof, and particularly to a matrix type display device having a structure in which an optical material such as a fluorescent material (luminescent material), a light modulation material or the like is selectively arranged at predetermined positions on a display substrate, the optical material being liquid at least during coating, and a manufacturing method thereof wherein the optical material can accurately be arranged at the predetermined positions.  
         [0004]     2. Description of Related Art  
         [0005]     Matrix type display devices such as an LCD (Liquid Crystal Display), an EL (Electroluminescence) display device, and the like are frequently used as various display devices that are light weight, thin, and have high image quality and high definition. A matrix type display device comprises matrix-formed bus lines, an optical material (luminescent material or light modulation material), and if required, other components.  
         [0006]     In a monochromatic matrix type display device, wiring and electrodes must be arranged in a matrix on the display substrate, but the optical material can be uniformly coated over the entire surface of the display substrate.  
         [0007]     In contrast, for example, when a so-called matrix type color display device is realized by using an EL display device of the type that emits light by itself, it is necessary to arrange three pixel electrodes corresponding to the primary colors RGB of light for each pixel, and coat the optical material corresponding to any one of the primary colors RGB for each pixel electrode. Namely, the optical material must be selectively arranged at the predetermined positions.  
       SUMMARY OF THE INVENTION  
       [0008]     There is thus demand for developing a method of patterning the optical material. Suitable examples of effective patterning methods include etching and coating.  
         [0009]     The etching process is carried out as follows.  
         [0010]     First, a layer of an optical material is formed over the entire surface of the display substrate. Then a resist layer is formed on the optical material layer, exposed to light through a mask and then patterned. Then the optical material layer is patterned by etching in correspondence with the resist pattern.  
         [0011]     However, in this case, a large number of steps are required, and each of the materials and apparatus used is expensive, thereby increasing the cost. Also a large number of steps are required, and each of the steps is complicated, thereby deteriorating throughput. Further, depending upon chemical properties, some optical materials have low resistance to resist and an etchant, and thus these steps are impossible.  
         [0012]     On the other hand, the coating process is carried out as follows.  
         [0013]     First, an optical material is dissolved in a solvent to form a solution, and the thus-formed solution of the optical material is selectively coated at the predetermined positions on the display substrate by an ink jet method or the like. Then, if required, the optical material is solidified by heating, irradiation of light, or the like. In this case, a small number of steps are required, and each of the materials and apparatus used is inexpensive, thereby decreasing the cost. Also, a small number of steps are required, and each of the steps is simple, thereby improving throughput. Further, these steps are possible regardless of the chemical properties of the optical material used as long as a solution of the optical material can be formed.  
         [0014]     The coating patterning method is thought to be easily carried out. However, as a result of experiment, the inventors found that in coating the optical material by the ink jet method, the optical material must be diluted at least several tens of times with a solvent, and thus the solution obtained has high fluidity, thereby causing difficulties in holding the solution at the coating positions until it is completely solidified after coating.  
         [0015]     In other words, patterning precision deteriorates due to the fluidity of the solution of the optical material. For example, the optical material coated in a pixel flows to the adjacent pixels to deteriorate the optical properties of the pixels. Also variations occur in the coating areas in the respective pixels, thereby causing variations in the coating thickness and thus the optical properties of the optical material.  
         [0016]     Although this problem significantly occurs with an optical material for EL display devices or the like, which is liquid during coating and then solidified, the problem also occurs in cases in which a liquid crystal that is liquid both during and after coating is selectively coated on the display substrate.  
         [0017]     The present invention has been achieved in consideration of the unsolved problem of the prior art, and an object of the invention is to provide a matrix type display device in which a liquid optical material can securely be arranged at predetermined positions while maintaining characteristics such as low cost, high throughput, a high degree of freedom of the optical material, etc., and a manufacturing method thereof.  
         [0018]     One aspect of the invention relates to a matrix type display device having a structure in which an optical Material is selectively arranged at predetermined positions on a display substrate, the optical material being liquid at least during coating-at the predetermined positions, wherein a surface feature is formed at each of the predetermined positions for selectively coating the optical material.  
         [0019]     As used herein, surface feature refers to any one of a structural surface feature on a substrate, such as a bump, cavity or other structural feature, or other physical features, such as water repellency hydrophilicity, liquid repellency, lyophilicity or electric charge/potential distribution.  
         [0020]     One aspect of the invention thus permits selective arrangement of the optical material at the predetermined positions using the surface feature even if the optical material is liquid during coating. Namely, the matrix type display device is a high-quality matrix type display device comprising the optical material accurately arranged-at the predetermined positions.  
         [0021]     One aspect of the invention relates to a method of manufacturing a matrix type display device having a structure in which an optical material is selectively arranged at predetermined positions on a display substrate, the optical material being liquid at least during coating at the predetermined positions, the method comprising the steps of forming a surface feature at each of the predetermined positions and coating the liquid optical material at-the predetermined positions using the surface features.  
         [0022]     One aspect of invention comprises forming the surface features before coating the liquid optical material, and is thus capable of preventing the liquid optical material coated at the predetermined positions from spreading to the peripheries thereof. As a result, it is possible to improve the pattering precision while maintaining characteristics such as low cost, high throughput, the high degree of freedom of the optical material, etc.  
         [0023]     One aspect of the invention relates to the method of manufacturing a matrix type display device wherein a structural surface feature, i.e., difference in height, is formed in a concave shape in which each of the predetermined positions is lower than the periphery thereof so that the liquid optical material is coated at the predetermined positions with the surface of the display substrate coated with the liquid optical material turned upward.  
         [0024]     In this aspect of the invention, the surface of the display substrate which is coated with the optical material is turned upward to turn the concave portions formed by the difference in height upward. When the liquid optical material is coated on the insides of the concave portions, the optical material stays in the concave portions due to gravity, and the coated liquid optical material can stay in the concave portions due to gravity, surface tension and the like as long as the amount of the optical material coated is not too large. Therefore, in this state, the optical material can be solidified by, for example, drying to perform patterning with high precision and with no problem.  
         [0025]     One aspect of the invention relates to the method of manufacturing a matrix type display device wherein the difference in height has a convex shape in which each of the predetermined positions is higher than the periphery thereof so that the liquid optical material is coated at the predetermined positions with the surface of the display substrate that is coated with the optical material turned downward.  
         [0026]     In this aspect of the invention, when the surface of the display substrate coated with the optical material is turned downward, the convex portions formed by the difference in height are also turned downward. In coating the liquid optical material on the convex portions, the optical material concentrates on the convex portions due to surface tension, and the coated liquid optical material can stay on the convex portions due to surface tension as long as the amount of the optical material coated is not too large. Therefore, in this state, the optical material can be solidified by, for example, drying to perform patterning with high precision and with no problem.  
         [0027]     One aspect of the invention relates to a method of manufacturing a matrix type display device comprising an optical material selectively disposed at predetermined positions on a display device, the optical material being liquid at least during coating at the predetermined positions, the method comprising the steps of forming a plurality of first bus lines on the display substrate; coating the liquid optical material; forming surface features at each of the predetermined positions on the display substrate for coating the liquid optical material; coating the liquid optical material at the predetermined positions and forming a plurality of second bus lines crossing the first bus lines to cover the optical material.  
         [0028]     One aspect of the invention relates to a method of manufacturing a matrix type display device comprising an optical material selectively disposed at predetermined positions on a display device, the optical material being liquid at least during coating at the predetermined positions, the method comprising the steps of forming a plurality of first bus lines on the display substrate; forming surface features at each of the predetermined positions on the display substrate for coating the liquid optical material; coating the liquid optical material at the predetermined positions forming a plurality of second bus lines on a peeling substrate through a peeling layer; and transferring the structure peeled off from the peeling layer on the peeling substrate onto the display substrate coated with the optical material so that the first bus lines cross the second bus lines.  
         [0029]     In a method of manufacturing a so-called passive matrix type display device, this aspect of the invention comprises no step of forming a layer for the second bus lines on the upper surface of the optical material disposed, and then etching the layer, thereby decreasing damage to the base material such as the optical material or the like in the subsequent step.  
         [0030]     One aspect of the invention relates to a method of manufacturing a matrix type display device comprising an optical material selectively disposed at predetermined positions on a display device, the optical material being liquid at least during coating at the predetermined positions, the method comprising the steps of forming, on the display substrate, wiring including a plurality of scanning lines and signal lines, a pixel electrode corresponding to each of the predetermined positions, and switching elements for controlling the states of the pixel electrodes in accordance with the state of the wiring; forming surface features at each of the predetermined positions on the display substrate for coating the liquid optical material; and coating the liquid optical material at the predetermined positions.  
         [0031]     One aspect of the invention relates to a method of manufacturing a matrix type display device comprising an optical material selectively disposed at predetermined positions on a display device, the optical material being liquid at least during coating at the predetermined positions, the method comprising the steps of forming surface features at each of the-predetermined positions on the display substrate for coating the liquid optical material; coating the liquid optical material at the predetermined positions; forming wiring including a plurality of scanning lines and signal lines, a pixel electrode corresponding to each of the predetermined positions, and switching elements for controlling the states of the pixel electrodes in accordance with the state of the wiring on a peeling substrate through a peeling layer; and transferring the structure peeled off from the peeling layer on the peeling substrate onto, the display substrate coated with the optical material.  
         [0032]     In a method of manufacturing a so-called active-matrix type display device, this aspect of the invention comprises no step of forming a layer for the wiring and a layer for the pixel electrodes on the upper surface of the optical material disposed, and then etching the layers, thereby decreasing damage to the base material such as the optical material or the like in-the subsequent step, and damage to the scanning lines, the signal lines, the pixel electrodes or the switching elements due to coating of the optical material.  
         [0033]     One aspect of the invention relates to the method of manufacturing a matrix type display device wherein a difference in height is formed by using the first bus lines and has a concave shape in which each of the predetermined positions is lower than the periphery thereof so that in the step of coating the liquid optical material, the liquid optical material is coated at the predetermined positions with the surface of the display substrate coated with the liquid crystal material turned upward.  
         [0034]     In a method of manufacturing a so-called passive matrix type display device, this aspect of the invention comprises the step of forming a difference in height by using the first bus lines. As a result, the step of forming the first bus lines, in whole or in part, can also be used as-the step of forming the surface features, thereby suppressing an increase in the number of the steps.  
         [0035]     One aspect of the invention relates to the method of manufacturing a matrix type display device wherein a difference in height is formed by using the wiring and has a concave shape in which each of the predetermined positions is lower than the periphery thereof so that in the step of coating the liquid optical material, the liquid optical material is coated at the predetermined positions with the surface of the display substrate coated with the liquid crystal material turned upward.  
         [0036]     In a method of manufacturing a so-called active matrix type display device, this aspect of the invention comprises the step of forming a difference in height by using the wiring. As a result, part of the whole of the step of forming the wiring can also be used as the step of forming the surface features, thereby suppressing an increase in the number of the steps.  
         [0037]     One aspect of the invention relates to the method of manufacturing a matrix type display device wherein a difference in height is formed by using the pixel electrodes, and has a convex shape in which each of the predetermined positions is higher than the periphery thereof so that in the step of coating the liquid optical material, the liquid optical material is coated at the predetermined positions with the surface of the display substrate coated with the liquid crystal material turned downward.  
         [0038]     In a method of manufacturing a so-called active matrix type display device, this aspect of the invention comprises the step of forming a difference in height by using the pixel electrodes. As a result, the step of forming the wiring, in whole or in part, can also be used as the step of forming the surface features, thereby suppressing an increase in the number of the steps.  
         [0039]     One aspect of the invention relates to the method of manufacturing a matrix type display device comprising the step of forming an interlevel insulation film, wherein a difference in height is formed by using the interlevel insulation film, and has a concave shape in which each of the predetermined positions is lower than the periphery thereof so that in the step of coating the liquid optical material, the liquid optical material is coated at the predetermined positions with the surface of the display substrate coated with the liquid crystal material turned upward.  
         [0040]     In a method of manufacturing a so-called passive matrix type display device and a method of manufacturing a so-called active matrix type display device, this aspect of the invention comprises the step of forming a difference in height by using the interlevel insulation film. As a result, the step of forming the interlevel insulation film, in whole or in part, can also be used as the step of forming the surface features, thereby suppressing an increase in the number of the steps.  
         [0041]     One aspect of the invention relates to the method of manufacturing a matrix type display device comprising the step of forming a light shielding layer, wherein a difference in height is formed by using the light shielding layer, and has a concave shape in which each of the predetermined positions is lower than the periphery thereof so that in the step of coating the liquid optical material, the liquid optical material is coated at the predetermined positions with the surface of the display substrate coated with the liquid crystal material turned upward.  
         [0042]     In a method of manufacturing a so-called passive matrix type display device and a method of manufacturing a so-called active matrix type display device, this aspect of the invention comprises the step of forming a difference in height by using a light shielding layer. As a result, the step of forming the light shielding layer, in whole or in part, can also be used as the step of forming the surface features, thereby suppressing an increase in the number of f the steps. One aspect of the invention relates to the method of manufacturing a matrix type display device wherein in the step of forming the difference in height, the difference in height is formed by selectively removing-the coated liquid material. Resist or the like can be used as the liquid material. In the us-e of resist, the resist is coated over the entire surface of the display device by spin coating to form a resist film having an appropriate thickness, followed by exposure and etching of the resist film to form a convex portion corresponding to each of the predetermined positions, whereby the difference in height can be formed.  
         [0043]     This aspect of the invention can simplify the step of forming the difference in height and can easily form a large difference in height while decreasing damage to the base material.  
         [0044]     One aspect of the invention relates to the method of manufacturing a matrix type display device wherein a difference in height is formed on the peeling substrate through the peeling layer, and the structure peeled off from the peeling layer on the peeling substrate is transferred onto the display substrate.  
         [0045]     This aspect of the invention comprises the step of transferring the difference in height separately formed on the peeling substrate. Therefore, the invention can simplify the step of forming the surface features and can easily form a large difference in height while decreasing damage to the base material.  
         [0046]     One aspect of the invention relates to the method of manufacturing a matrix type display device wherein the height dr of the difference in height satisfies the following equation (1):
 
d a &lt;d r   (1)
 
         [0047]     wherein d a  is the thickness of a single coat of the liquid optical material.  
         [0048]     This aspect of the invention is capable of preventing the optical material from flowing out to the peripheries of the predetermined positions beyond the concave difference in height without contribution of surface tension of the liquid optical material.  
         [0049]     One aspect of the invention relates to the method of manufacturing a matrix type display device wherein the following equation (2) is satisfied:
 
 V   d /( d   b   ·r )&gt; E   t   (2)
 
         [0050]     wherein V d  is the driving voltage applied to the optical material, db is the total thickness of the respective coatings of the liquid optical material, r is the concentration of the liquid optical material, and Et is the minimum electric field strength (threshold electric field strength) at which a change in optical properties of the optical material occurs.  
         [0051]     This aspect of the invention defines the relation between the coating thickness and the driving voltage, thereby ensuring that the optical material exhibits an electro-optical effect.  
         [0052]     One aspect of the invention relates to the method of manufacturing a matrix type display device wherein the height dr of the difference in height satisfies the following equation (3):
 
d f =d r   (3)
 
         [0053]     wherein df is the thickness of the optical material at the time of completion.  
         [0054]     This aspect of the invention ensures flatness of the difference in height and the optical material at the time of completion, and uniformity in the optical properties of the optical material, and can prevent a short circuit.  
         [0055]     One aspect of the invention relates to the method of manufacturing a matrix type display device wherein the thickness at the time of completion satisfies the following equation (4)
 
 V   d   /d   f   &gt;E   t   (4)
 
         [0056]     wherein V d  is the driving voltage applied to the optical material, and E t  is the minimum electric field strength (threshold electric field strength) at which a change in optical properties of the optical material occurs.  
         [0057]     This aspect of the invention defines the relation between the coating thickness and the driving voltage, thereby ensuring that the optical material exhibits an electro-optical effect.  
         [0058]     One aspect of the invention relates to a method of manufacturing a matrix type display device comprising an optical material selectively disposed at predetermined positions on a display device, the optical material being liquid at least during coating at the predetermined positions, the method comprising the steps of enhancing the lyophilicity at the predetermined positions on the display device relative to the lyophilicity of the peripheries thereof, and coating the liquid optical material at the predetermined positions.  
         [0059]     In this aspect of the invention since the lyophilicity at the predetermined positions is enhanced before the liquid optical material is coated, the liquid optical material coated at the predetermined positions more easily stays at the predetermined positions than the peripheries thereof, and the difference in lyophilicity between each of the predetermined positions and the periphery thereof is sufficiently increased to prevent the liquid optical material coated at the predetermined positions from spreading to the peripheries thereof. As a result, it is possible to improve the precision of patterning while maintaining the properties such as low cost, high throughput and the high degree of freedom of the optical material.  
         [0060]     The step of enhancing the lyophilicity at the predetermined positions on the display substrate relative to the lyophilicity of the peripheries thereof possibly comprises enhancing the lyophilicity at the predetermined positions, enhancing the liquid repellency of the peripheries of the predetermined positions, or performing both methods.  
         [0061]     One aspect of the invention relates to a method of manufacturing a matrix type display device comprising an optical material selectively disposed at predetermined positions on a display device, the optical material being liquid at least during coating at the predetermined positions, the method comprising the steps of forming a plurality of first bus lines on the display device, enhancing the lyophilicity at the predetermined positions on the display device relative to the lyophilicity of the peripheries thereof, coating the liquid optical material at the predetermined positions, and forming a plurality of second bus lines crossing the first bus lines to cover the optical material.  
         [0062]     One aspect of the invention relates to a method of manufacturing a matrix type display device comprising an optical material selectively disposed at predetermined positions on a display device, the optical material being liquid at least during coating at the predetermined positions, the method comprising the steps of forming a plurality of first bus lines on the display device, enhancing the lyophilicity at the predetermined positions on the display device relative to the lyophilicity of the peripheries thereof, coating the liquid optical material at the predetermined positions, forming a plurality of second bus lines on a peeling substrate through a peeling layer, and transferring the structure peeled off from the peeling layer on the peeling substrate onto the display substrate coated with the optical material so that the first bus lines cross the second bus lines.  
         [0063]     In a method of manufacturing a so-called passive matrix type display device, this aspect of the invention comprises no step of forming a layer for the second bus lines on the disposed optical material and etching the layer. It is thus possible to decrease damage to the base material such as the optical material or the like in the subsequent step.  
         [0064]     One aspect of the invention relates to a method of manufacturing a matrix type display device comprising an optical material selectively disposed at predetermined positions on a display device, the optical material being liquid at least during coating at the predetermined positions, the method comprising the steps of forming, on the display device, wiring including a plurality of scanning lines and signal lines, a pixel electrode corresponding to each of the predetermined positions, and switching elements for controlling the states of the pixel electrodes in accordance with the state of the wiring; enhancing the lyophilicity at the predetermined positions on the display device relative to the lyophilicity of the peripheries thereof, and coating the liquid optical material at the predetermined positions.  
         [0065]     One aspect of the invention relates to a method of manufacturing a matrix type display device comprising an optical material selectively disposed at predetermined positions on a display device, the optical material being liquid at least during coating at the predetermined positions, the method comprising the steps of enhancing the lyophilicity at the predetermined positions on the display device relative to the lyophilicity of the peripheries thereof: coating the liquid optical material at the predetermined positions: forming wiring including a plurality of scanning lines and signal lines, a pixel electrode corresponding to the each of the predetermined positions, and switching elements for controlling the states of the pixel electrodes in accordance with the state of the wiring on a peeling substrate through a peeling layer; and transferring the structure peeled off from the peeling layer on the peeling substrate onto the display substrate coated with the optical material.  
         [0066]     In a method of manufacturing a so-called active matrix type display device, this aspect of the invention comprises no step of forming a layer for wiring and a layer for the pixel electrodes on the optical material disposed and etching these layers. It is thus possible to decrease damage to the base material such as the optical material or the like in the subsequent step, and damage to the scanning lines, the signal lines, the pixel electrodes or the switching elements due to coating of the optical material.  
         [0067]     One aspect of the invention relates to the method of manufacturing a matrix type display device wherein a distribution of high liquid repellency is formed along the first bus lines on the display substrate to enhance the lyophilicity at the predetermined positions on the display substrate relative to the lyophilicity of the peripheries thereof.  
         [0068]     In a method of manufacturing a so-called passive matrix type display device, this aspect of the invention comprises forming a distribution of high liquid repellency along the first bus lines. As a result, the step of forming the first bus lines, in whole or in part, can also be used as the step of enhancing the lyophilicity at the predetermined positions relative to the lyophilicity of the peripheries thereof, thereby suppressing an increase in the number of the steps.  
         [0069]     One aspect of the invention relates to the method of manufacturing a matrix type display device wherein a distribution of high liquid repellency is formed along the wiring on the display substrate to enhance the lyophilicity at the predetermined positions on the display substrate relative to the lyophilicity of the peripheries thereof.  
         [0070]     In a method of manufacturing a so-called active matrix type display device, this aspect of the invention comprises forming a distribution of high liquid repellency along the wiring. As a result, the step of forming the first bus lines, in whole or in part, can also be used as the step of enhancing the lyophilicity at the predetermined positions relative to the lyophilicity of the peripheries thereof, thereby suppressing an increase in the number of the steps.  
         [0071]     One aspect of the invention relates to the method of manufacturing a matrix type display device wherein the lyophilicity of the surfaces of the pixel electrodes on the display substrate are enhanced to enhance the lyophilicity at, the predetermined positions on the display substrate relative to the lyophilicity of the peripheries thereof.  
         [0072]     In a method of manufacturing a so-called active matrix type display device, this aspect of the invention comprises enhancing the lyophilicity of the surfaces of the pixel electrodes. As a result, the step of forming the pixel electrodes, in whole or in part, can also be used as the step of enhancing the lyophilicity at the predetermined positions relative to the lyophilicity of the peripheries thereof, thereby suppressing an increase in the number of the steps.  
         [0073]     One aspect of the invention relates to the method of manufacturing a matrix type display device comprising the step of forming an interlevel insulation film, wherein a distribution of high liquid repellency is formed along the interlevel insulation film on the-display substrate to enhance the lyophilicity at the predetermined positions on the display substrate relative to the lyophilicity of the peripheries thereof.  
         [0074]     In a method of manufacturing a so-called s passive matrix type display device, this aspect of the invention comprises forming a distribution of high liquid repellency along the interlevel insulation film. As a result, the step of forming the interlevel insulation film, in whole or impart, can also be used as the step of enhancing the lyophilicity at the predetermined positions relative to the lyophilicity of the peripheries thereof, thereby suppressing an increase in the number of the steps.  
         [0075]     One aspect of the invention relates to the method of manufacturing a matrix type display device comprising the step of forming an interlevel insulation film so that the surfaces of the pixel electrodes are exposed, wherein in forming the interlevel insulation film, a difference in height for coating the liquid optical material is formed in the boundary between the portion where the surface of each of the pixel electrodes is exposed and the periphery thereof, and the liquid repellency of the surface of the interlevel insulation film is enhanced to enhance the lyophilicity at the predetermined positions on the display substrate relative to the lyophilicity of the peripheries thereof.  
         [0076]     In this aspect of the invention the difference in height is formed in a concave shape by using the interlevel insulation film before the liquid optical material is coated, and the liquid repellency of the surface of the interlevel insulation film is enhanced to enhance the lyophilicity at the predetermined positions relative to the lyophilicity of the peripheries thereof. Therefore, the liquid optical material coated at the predetermined positions is prevented from spreading to the peripheries thereof. As a result, it is possible to further improve the patterning precision while maintaining the properties such as low cost, high throughput and the high degree of freedom of the optical material.  
         [0077]     One aspect of the invention relates to the method of manufacturing a matrix type display device comprising the step of forming a light shielding layer, wherein a distribution of high liquid repellency is formed along the light shielding layer on the display substrate to enhance the lyophilicity at the predetermined positions on the display substrate relative to the lyophilicity of the peripheries thereof.  
         [0078]     In a method of manufacturing a so-called passive matrix type display device and a method of manufacturing a so-called active matrix type O display device, this aspect of the invention comprises forming a distribution of high liquid repellency along the light shielding layer. As a result, the step of forming the light shielding layer, in whole or in part, can also be used as the step of enhancing the lyophilicity at the predetermined positions relative to the lyophilicity of the peripheries thereof, thereby suppressing an increase in the number of the steps.  
         [0079]     One aspect of the invention relates to the method of manufacturing a matrix type display device wherein a difference in lyophilicity between each of the predetermined positions and the periphery thereof is increased by irradiating ultraviolet rays or plasma of O 2 , CF 3 , Ar or the like.  
         [0080]     Thus, this aspect of the invention is capable of easily enhancing the liquid repellency of the surface of the interlevel insulation film, for example.  
         [0081]     One aspect of the invention relates to the method of manufacturing a matrix type display device comprising the step of enhancing the lyophilicity at the predetermined positions on the display substrate relative to the lyophilicity of the peripheries thereof.  
         [0082]     One aspect of the invention relates to the method of manufacturing a matrix type display device comprising the step of forming a difference in height in the boundary between each of the predetermined positions on the display substrate and the periphery thereof, for coating the liquid optical material.  
         [0083]     One aspect of the invention comprises forming a predetermined difference in height and enhancing the lyophilicity at the predetermined positions relative to the lyophilicity of the peripheries thereof before the liquid optical material is coated. Therefore, this aspect of the invention securely prevents the liquid optical material coated at the predetermined positions from spreading to the peripheries thereof. As a result, it is possible to further improve the patterning precision while maintaining the properties such as low cost, high throughput and the high degree of freedom of the optical material.  
         [0084]     One aspect of the invention relates to a method of manufacturing a matrix type display device comprising an optical material selectively disposed at predetermined positions on a display device, the optical material being liquid at least during coating at the predetermined positions, the method comprising the steps of forming a potential distribution on the display substrate so that the potential at each of the predetermined positions is different from that of the periphery thereof, and selectively coating the liquid optical material at the predetermined positions by using the potential distribution.  
         [0085]     This aspect of the invention comprises forming a potential distribution before the liquid optical material is coated so that the liquid optical material coated at the predetermined positions can be prevented from spreading to the peripheries thereof by the potential distribution. As a result, it is possible to improve the patterning precision while maintaining the properties such as low cost, high throughput and the high degree of freedom of the optical material.  
         [0086]     One aspect of the invention relates to a method of manufacturing a matrix type display device comprising an optical material selectively disposed at predetermined positions on a display device, the optical material being liquid at least during coating at the predetermined positions, the method comprising the steps of forming a potential distribution on the display substrate so that the potential at each of the predetermined positions is different from that of the periphery thereof, and coating the liquid optical material at the predetermined positions after charging the optical material to a potential where a repulsive force is generated between each of the predetermined positions and the periphery thereof.  
         [0087]     This aspect of the invention comprises generating a repulsive force between the liquid optical material that is coated at the predetermined positions and the peripheries thereof so as to prevent the liquid optical material coated at the predetermined positions from spreading to the peripheries thereof. As a result, it is possible to improve the patterning precision while maintaining the properties such as low cost, high throughput and the high degree of freedom of the optical material.  
         [0088]     One aspect of the invention relates to a method of manufacturing a matrix type display device comprising an optical material selectively disposed at predetermined positions on a display device, the optical material being liquid at least during coating at the predetermined positions, the method comprising the steps of forming a plurality of first bus lines on the display substrate, forming a potential distribution on the display substrate so that the potential at each of the predetermined positions is different from that of the periphery thereof, coating the liquid optical material at the predetermined positions after charging the optical material to a potential where a repulsive force is generated between each of the predetermined positions and the periphery thereof, and forming a plurality of second bus lines crossing the first bus lines to cover the optical material.  
         [0089]     One aspect of the invention relates to a method of manufacturing a matrix type display device comprising an optical material selectively disposed at predetermined positions on a display device, the optical material being liquid at least during coating at the predetermined positions, the method comprising the steps of forming a plurality of first bus lines on the display substrate, forming a potential distribution on the display substrate so that the potential at each of the predetermined positions is different from that of the periphery thereof, coating the liquid optical material at the predetermined positions after charging the optical material to a potential at which a repulsive force is generated between each of the predetermined positions and the periphery thereof, forming a plurality of second bus lines on a peeling substrate through a peeling layer, and transferring the structure peeled off from the peeling layer on the peeling substrate onto the display substrate coated with the optical material so that the first bus lines cross the second bus lines.  
         [0090]     In a method of manufacturing a so-called passive matrix type display device, this aspect of the invention comprises no step of forming a layer for the second bus lines on the upper surface of the disposed optical material and etching the layer, thereby decreasing damage to the base material such as the optical material or the- like in the subsequent step.  
         [0091]     One aspect of the invention relates to a method of manufacturing a matrix type display device comprising an optical material selectively disposed at predetermined positions on a display device, the optical material being liquid at least during coating at the predetermined positions, the method comprising the steps of forming on the display substrate wiring including a plurality of scanning lines and signal lines, a pixel electrode corresponding to each of the predetermined positions and switching elements for controlling the states of the pixel electrodes in accordance with the state of the wiring, forming a potential distribution on the display substrate so that the potential at each of the predetermined positions is different from that of the periphery thereof, and coating the liquid optical material at the predetermined positions after charging the optical material to a potential at which a repulsive force is generated between each of the predetermined positions and the periphery thereof.  
         [0092]     One aspect of the invention relates to a method of manufacturing a matrix type display device comprising an optical material selectively disposed at predetermined positions on a display device, the optical material being liquid at least during coating at the predetermined positions. The method comprises the steps of forming a potential distribution on the display substrate so that the potential at each of the predetermined positions is different from that of the periphery thereof, coating the liquid optical material at the predetermined positions after charging the optical material to a potential at which a repulsive force is generated between each of the predetermined positions and the periphery thereof, forming wiring including a plurality of scanning lines and signal lines, a pixel electrode corresponding to each of the predetermined positions and switching elements for controlling the states of the pixel electrodes in accordance with the state of the wiring on a peeling substrate through a peeling layer, and transferring the structure peeled off from the from the peeling layer on the peeling substrate onto the display substrate coated with the optical material.  
         [0093]     In a method of manufacturing a so-called active matrix type display device, this aspect of the invention comprises no step of forming a layer for the wiring and a layer for the pixel electrodes on the upper surface of the disposed optical material and etching these layers, thereby decreasing damage to the base material such as the optical material or the like in the subsequent step, and damage to the scanning lines, the signal lines, the pixel electrodes or the switching elements due to coating of the optical material.  
         [0094]     One aspect of the invention relates to the method of manufacturing a matrix type display device wherein the potential distribution is formed so that at least the peripheries of the predetermined positions on the-display substrate are charged.  
         [0095]     Thus, this aspect of the invention is capable of securely generating a repulsive force by charging the liquid optical material.  
         [0096]     One aspect of the invention relates to the method of manufacturing a matrix type display device wherein the potential distribution is formed by applying a voltage to the first bus lines.  
         [0097]     One aspect of the invention relates to the method of manufacturing a matrix 10 type display device wherein the potential distribution is formed by applying a voltage to the wiring.  
         [0098]     One aspect of the invention relates to the method of manufacturing a matrix type display device wherein the potential distribution ‘I is formed by applying a voltage to the pixel electrodes. The invention in accordance with claim  44  relates to the method of manufacturing a matrix type display device of the invention in accordance with claim  38 , wherein the potential distribution—is formed by successively applying a voltage to the scanning lines, and at the same time, applying a voltage to the signal lines, and applying a voltage to the pixel electrodes through the switching elements.  
         [0099]     One aspect of the invention relates to the method of manufacturing a matrix type display device comprising the step of forming a light shielding layer so that the potential distribution is formed by applying a voltage to the light shielding layer.  
         [0100]     One aspect of the invention comprises forming the potential distribution by using a component of the matrix type display device, and is thus capable of preventing an increase in the number of the steps.  
         [0101]     One aspect of the invention relates to the method of manufacturing a matrix type display device wherein the potential distribution is formed so that each of the predetermined positions has a polarity opposite to that of the periphery thereof.  
         [0102]     In this aspect of the invention an attractive force is generated between the liquid optical material and each of the predetermined positions, and repulsive force is generated between the liquid optical material and the peripheries of the predetermined positions, thereby making the optical material easy to stay at the predetermined positions, and improving the patterning precision.  
         [0103]     In the method of manufacturing a matrix type display device in one aspect of the invention, an inorganic or organic fluorescent material (luminescent material) can be used as the optical material. As the fluorescent material (luminescent material), an EL (Electroluminescent) material is suitable. In order to obtain the liquid optical material, the optical material may be dissolved in an appropriate solvent.  
         [0104]     In the method of manufacturing a matrix type display device in one aspect of the invention a liquid crystal can also be used as the optical material.  
         [0105]     One aspect of the invention relates to the method of manufacturing a matrix type display device wherein the switching elements are formed by using amorphous silicon, polycrystalline silicon formed by a high temperature process at 600° C. or higher, or polycrystalline silicon formed by a low temperature process at 600° C. or lower.  
         [0106]     This aspect of the invention can also improve the precision of patterning of the optical material. Particularly, in the use of polycrystalline silicon formed by a low temperature process, it is possible to decrease the cost by using a glass substrate, and improve performance due to high mobility. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0107]      FIG. 1  is a diagram of a circuit showing a portion. of a display device in accordance with a first embodiment of the present invention.  
         [0108]      FIG. 2  is an enlarged plan view showing the plane structure of a pixel region.  
         [0109]     FIGS.  3 ( a ) to  5 ( d ) are drawings showing the flow of a manufacturing process in accordance with the first embodiment.  
         [0110]      FIG. 6  is a sectional view showing a modified embodiment of the first embodiment.  
         [0111]     FIGS.  7 ( a ) and  7 ( b ) are a plan view and sectional view showing a second embodiment.  
         [0112]      FIG. 8  is a sectional view showing a portion of a manufacturing process in accordance with a third embodiment.  
         [0113]      FIG. 9  is a sectional view showing a portion of a manufacturing process in accordance with a fourth embodiment.  
         [0114]      FIG. 10  is a sectional view showing a portion of a manufacturing process in accordance with a fifth embodiment.  
         [0115]      FIG. 11  is a sectional view showing a portion of a manufacturing process in accordance with a sixth embodiment.  
         [0116]      FIG. 12  is a sectional view showing a portion of a manufacturing process in accordance with an eighth embodiment.  
         [0117]      FIG. 13  is a sectional view showing a modified embodiment of the eighth embodiment. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0000]     Preferred embodiments of the present invention will be described below on the basis of the drawings.  
         [0000]     (1) First Embodiment  
         [0118]     FIGS.  1  to  5 ( d ) are drawings illustrating a first embodiment of the present invention. In this embodiment, a matrix type display device and a manufacturing method thereof of the present invention are applied to an active matrix type EL display device. Specifically, these drawings show an embodiment in which a luminescent material as an optical material is coated, and scanning lines, signal lines and common current supply lines serve as wiring.  
         [0119]      FIG. 1  is a drawing of a circuit showing a portion of a display device  1  in this embodiment. The display device  1  comprises wiring including a plurality of scanning lines  131 , a plurality of signal lines  132  extending in the direction crossing the scanning lines  131 , and a plurality of common current supply lines  133  extending parallel to the signal lines  132 ; and a pixel region  1 A provided for each of the intersections of the scanning lines  131  and the signal lines  132 .  
         [0120]     For the signal lines  132 , a data side driving circuit  3  comprising a shift register, a level shifter, a video line, and an analog switch is provided. For the scanning lines  131 , a scanning side driving circuit  4  comprising a shift register and a level shifter is provided. Provided in each pixel region  1 A are: a switching thin film transistor  142  in which a scanning signal is supplied to a gate electrode through a scanning line  131 , a storage capacitor cap for holding an image signal supplied from a signal line  132  through the switching thin film transistor  142 , a current thin film transistor  143  in which the image signal held by the storage capacitor cap is supplied to a gate electrode, a pixel electrode  141  to which a driving current flows from a common current supply line  133  at the time of electrical connection to the common current supply line  133  through the current thin film transistor  143 , and a light emitting element  140  held between the pixel electrode  141  and a reflection electrode  154 .  
         [0121]     In this configuration, when the switching thin film transistor  142  is turned on by driving the scanning lines  131 , the potential of the signal lines  132  is held by the storage capacitor cap, and the on-off state of the current thin film transistor  143  is determined in accordance with the state of the storage capacitor cap. Then a current flows to the pixel electrode  141  from the common current supply lines  133  through the channel of the current thin film transistor  143 , and a current flows to the reflection electrode  154  through the light emitting element  140 , whereby the light emitting element  140  emits light in accordance with the amount of the current flowing therethrough.  
         [0122]     Each of the pixel regions  1 A has a planar structure in which the pixel electrode  141  having a rectangular planar shape is arranged so that the four sides thereof are surrounded by a signal line  132 , a common current supply line  133 , a scanning line  131  and a scanning line for another pixel electrode, as shown in  FIG. 2  which is an enlarged plan view-with the reflection electrode and the light emitting element removed.  
         [0123]     FIGS.  3 ( a ) to  5 ( d ) are sectional views successively showing the steps for manufacturing the pixel region  1 A, and correspond to a section taken along line-A-A in  FIG. 2 . The process for manufacturing the pixel region  1 A is described with reference to FIGS.  3 ( a ) to  5 ( d ).  
         [0124]     First, as shown in  FIG. 3 ( a ), on a transparent display substrate  121  is formed a base protective film (not shown) comprising a silicon oxide film having a thickness of about 2000 to 5000 angstroms by a plasma CVD method using TEOS (tetraethoxysilane) and oxygen gas as raw material gases according to demand. Next, the temperature of the display substrate  121  is set to about 350° C., and on the surface of the base protective film is formed a semiconductor film  200  comprising an amorphous silicon film having a thickness of about 300 to 700 angstroms by the plasma CVD method. The semiconductor film  200  comprising an amorphous silicon film is then subjected to the crystallization step by laser annealing or solid phase growth to crystallize the semiconductor film  200  to a polysilicon film. In laser annealing, for example, an excimer laser line beam having a long dimension of  400  mm and an output strength of, for example, 200 mJ/cm2 is used. The line beam is scanned so that a portion thereof corresponding to 90% of the laser strength peak in the direction of the short dimension is applied to each of the regions.  
         [0125]     Next, as shown in  FIG. 3 ( b ), the semiconductor film  200  is patterned to form an island-like semiconductor film  210 , and on the surface of the semiconductor film  210  is formed a gate insulating film  220 , comprising a silicon oxide film or nitride film having a thickness of about 600 to 1500 angstroms, by the plasma CVD method using TEOS (tetraethoxysilane) and oxygen gas as raw material gases. Although the semiconductor film  210  is used for the channel region and source/drain regions of the current thin film transistor  143 , another semiconductor film is also formed for forming the channel region and source/drain regions of the switching thin film transistor  142  in another sectional view. Namely, in the manufacturing process shown in FIGS.  3 ( a ) to  5 ( d ), two types of transistors  142  and  143  are simultaneously formed, but both transistors are formed according to the same procedure. Therefore, with respect to the transistors, only the current thin film transistor  143  is described below, and description of the switching thin film transistor  142  is omitted.  
         [0126]     Next, as shown in  FIG. 3 ( c ), a conductive film comprising a metallic film of aluminum, tantalum, molybdenum, titanium, tungsten, or the like is formed by a sputtering method, and then patterned to form a gate electrode  143 A.  
         [0127]     In this state, a high concentration of phosphorus ions is implanted to form source and drain regions  143   a  and  143   b  in the silicon thin film  210  in self-alignment to the gate electrode  143 . A portion into which the impurity is not introduced serves as a channel region  143   c.    
         [0128]     Next, as shown in  FIG. 3 ( d ), an interlevel insulation film  230  is formed, contact holes  232  and  234  are formed, and then trunk electrodes  236  and  238  are buried in the contact holes  232  and  234 , respectively.  
         [0129]     Next, as shown in  FIG. 3 ( e ), on the interlevel insulation film  230  are formed a signal line  132 , a common current supply line  133  and a scanning line (not shown in  FIG. 3 ). Each of the signal lines  132 , the common current supply lines  133  and the scanning lines is formed sufficiently thick regardless of the required thickness as wiring. Specifically, each of the lines is formed to a thickness of about 1 to 2 um. The trunk electrode  238  and each of the lines may be formed in the same step. In this case, the trunk electrode  238  is formed of an ITO film which will be described below.  
         [0130]     Then an interlevel insulation film  240  is formed to cover the upper surfaces of the lines, a contact hole  242  is formed at a position corresponding to the trunk electrode  236 , and an ITO film is formed to fill the contact hole  242  therewith, followed by patterning of the ITO film to form a pixel electrode  141  electrically connected to the source and drain region  143   a  at the predetermined position surrounded by the signal line  132 , the common current supply line  133  and the scanning line.  
         [0131]     In  FIG. 3 ( e ), the portion between the signal line  132  and the common current supply line  133  corresponds to the predetermined position where the optical material is arranged. A structural surface feature, or difference in height  111  is formed between the predetermined position and the periphery thereof by the signal line  132  and the common current supply line  133 . Specifically, the difference in height  111  is formed in a concave shape in which the predetermined position is lower than the periphery thereof.  
         [0132]     Next, as shown in  FIG. 4 ( a ), a liquid (a solution in a solvent) optical material (precursor)  114 A for forming a hole injection layer corresponding to a lower layer of the light emitting element  140  is discharged by an ink jet head method with the upper side of the display substrate  121  turned upward to selectively coat the optical material on the region (the predetermined position) surrounded by the difference in height  111 . Since detailed contents of the ink jet method are not included in the gist of the present invention, the contents are omitted (For such a method, refer to Japanese Unexamined Patent Publication Nos. 56-13184 and 2167751, for example).  
         [0133]     Materials for forming the hole injection layer include polyphenylenevinylene obtained from polytetrahydrothiophenylphenylene as a polymer precursor, 1,1-bis-(4-N,N-ditolylaminophenyl)cyclohexane, tris(8hydroxyquinolynol) aluminum, and the like.  
         [0134]     At this time, although the liquid precursor  114 A has high fluidity and tends to horizontally spread, the difference in height  111  is formed to surround the coating position, thereby preventing the liquid precursor  114 A from spreading to the outside of the predetermined position beyond the difference in height  111  as long as the amount of the liquid precursor  114 A coated in a single application is not excessively increased.  
         [0135]     Next, as shown in  FIG. 4 ( b ), the solvent of the liquid precursor  114 A is evaporated by heating or light irradiation to form a thin, solid hole injection layer  140   a  on the pixel electrode  141 . Depending upon the concentration of the liquid precursor  114 A, only a thin hole injection layer  140   a  is formed. Therefore, where a thicker hole injection layer  140   a  is required, the steps shown in FIGS.  4 ( a ) and ( b ) are repeatedly executed a necessary number of times to form the hole injection layer  140 A having a sufficient thickness, as shown in  FIG. 4 ( c ).  
         [0136]     Next, as shown in  FIG. 5 ( a ), a liquid (a solution in a solvent) of an optical material (organic fluorescent material)  114 B for forming an organic semiconductor film corresponding to an upper layer of the light emitting element  140  is discharged by the ink jet head method with the upper surface of the display substrate  121  turned upward to selectively coat the optical material on the region (the predetermined position) surrounded by the difference in height  111 .  
         [0137]     Organic fluorescent materials include cyanopolyphenylenevinylene, polyphenylenevinylene, polyalkylphenylene, 2,3,6,7-tetrahydro-11-oxo1H,5H,11H(1) benzopyrano[6,7,8-ij]-quinolizine-10carboxylic acid, 1,1-bis-(4-N,N-ditolylaminophenyl)cyclohexane, 2-13′,4′dihydroxyphenyl)-3,5,7-trihydroxy-1-benzopyrylium perchlorate, tris(8-hydroxyquinolynol)aluminum, 2,3,6,7-tetrahydro-9-methyl-11-oxo-1H,5H,11H(1) benzopyrano[6,7,8-ij]-quinolizine, aromatic diamine derivatives (TDP), oxydiazole dimers (OXD), oxydiazole derivatives (PBD), distyrylarylene derivatives (DSA), quinolynol metal complexes, beryllium-benzoquinolynol derivatives (Bebq), triphenylamine derivatives (MTDATA), distyryl derivatives, pyrazoline dimers, rubrene, quinacridone, triazole derivatives, polyphenylene, polyalkylfluorene, polyalkylthiophene, azomethine zinc complexes, porphyrin zinc complexes, benzoxazole zinc complexes, phenanthroineeuropiem complexes, and the like.  
         [0138]     At this time, although the liquid organic fluorescent material  114 B has high fluidity and tends to horizontally spread, the difference in height  111  is formed to surround the coating position, thereby preventing the liquid organic fluorescent material  114 B from spreading to the outside of the predetermined position beyond the difference in height  111  as long as the amount of the liquid organic fluorescent material  114 B coated in a single application is not excessively increased.  
         [0139]     Next, as shown in  FIG. 5 ( b ), the solvent of the liquid organic fluorescent material  114 B is evaporated by heating or light irradiation to form a solid organic semiconductor thin film  140   b  on the hole injection layer  140 A. Depending upon the concentration of the liquid organic fluorescent material  114 B, only a thin organic semiconductor film  140   b  is formed. Therefore, where a thicker organic semiconductor layer  140   b  is required, the steps shown in FIGS.  5 ( a ) and ( b ) are repeatedly executed a necessary number of times to form the organic semiconductor film  140 B having a sufficient thickness, as shown in  FIG. 5 ( c ).  
         [0140]     The hole injection layer  140 A and the organic semiconductor film  140 B constitute the light emitting element  140 . Finally, as shown in  FIG. 5 ( d ), the reflection electrode  154  is formed over the entire surface of the display substrate  121  or in stripes.  
         [0141]     In this embodiment, lines such as the signal line  132 , the common current supply line  133 , and the like are formed to surround the processing position where the light emitting element  140  is arranged, and are formed to have a thickness larger than the normal thickness to form the difference in height  111 , and the liquid precursor  114 A and the liquid organic fluorescent material  114 B are selectively coated. Therefore, this embodiment has the advantage that the patterning precision of the light emitting element  140  is high.  
         [0142]     Although the formation of the difference in height  111  causes the reflection electrode  154  to have a surface with relatively large unevenness, the possibility of producing a trouble such as disconnection or the like is significantly decreased by increasing the thickness of the reflection electrode  154  to some extent.  
         [0143]     In addition, since the difference in height  111  is formed by using the lines such as the signal line  132 , the common current supply line  133 , and the like, a new step is not added, and the manufacturing process is not significantly complicated.  
         [0144]     In order to securely prevent the liquid precursor  114 A and the liquid organic fluorescent material  11   4 B from flowing out from the inside of the difference in height  111 , the following relation is preferably established between the coating thickness da of the liquid precursor  114 A and the liquid organic fluorescent material  114 B and the height dr of the difference in height  111 .
 
d a &lt;d r   (1)
 
         [0145]     However, when the liquid organic fluorescent material  114 E is coated, the hole injection layer  140  A has already been formed, and thus the height dr of the difference in height  111  must be considered as a value obtained by subtracting the thickness of the hole injection layer  140 A from the initial thickness.  
         [0146]     Also, equation (1) is satisfied, and the following relation is established between the driving voltage Vd applied to the organic semiconductor film  140 B, the total thickness db of the liquid organic fluorescent material  114 B, the concentration r of the liquid organic fluorescent material  114 B, and the minimum electric field strength Et (threshold electric field strength) at which a change in optical properties of the organic semiconductor film  140 B occurs.
 
 V   d /( d   b   ·r )&gt; E   t   (2)
 
 In this case, the relation between the coating thickness and the driving voltage is defined, and it is ensured that the organic semiconductor film  140 E exhibits an electro-optical effect. 
 
         [0147]     On the other hand, in order to ensure the flatness of the difference in height  111  and the light emitting element  140  and uniformity in changes in the optical properties of the organic semiconductor film  140 B, and prevent short circuit, the following relation may be established between the thickness df of the light emitting  
         [0148]     element  140  at the time of completion and the height dr of the difference in height  111 :
 
d f =d r   (3)
 
         [0149]     In addition, if equation (3) is satisfied, and the following equation (4) is satisfied, the relation between the thickness of the light emitting element  140  at the time of completion and the driving voltage is defined, and it is ensured that the organic fluorescent material exhibits an electro-optical effect.
 
 V   d   /d   f   &gt;E   t   (4)
 
         [0150]     However, in this case, the thickness df is the thickness of the organic semiconductor film  140 B at the time of completion, not the thickness of the entire light emitting element  140 .  
         [0151]     The optical material which forms the upper layer of the light emitting layer  140  is not limited to the organic fluorescent material  114 B, and an inorganic fluorescent material may be used.  
         [0152]     Each of the transistors  142  and  143  as switching elements is preferably made of polycrystalline silicon formed by a low temperature process at 600° C. or less, thereby achieving low cost by using a glass substrate, and high performance due to high mobility. The switching elements may be made of amorphous silicon or polycrystalline silicon formed by a high temperature process at 600° C. or higher.  
         [0153]     Besides the switching thin film transistor  142  and the current thin film transistor  143 , another transistor may be provided, or a system of driving by only one transistor may be used.  
         [0154]     The difference in height  111  may be formed by using the first bus lines in a passive matrix display device, the scanning lines  131  in an active matrix display device, or the light shielding layer.  
         [0155]     In the light emitting element  140 , the hole injection layer  140 A may be omitted, though the efficiency of light emission (rate of hole injection) slightly deteriorates. Alternatively, an electron injection layer is formed between the organic semiconductor film  140 E and the reflection electrode  154  in place of the hole injection layer  140 A, or both the hole injection layer and the electron injection layer may be formed.  
         [0156]     Although, in this embodiment, the entire light emitting element  140  is selectively arranged in consideration of color display, for example, in a monochrome display device  1 , the organic semiconductor film  140 B may be uniformly formed over the entire surface of the display substrate  121 , as shown in  FIG. 6 . However, even in this case, the hole injection layer  140 A must be selectively arranged at each of the predetermined positions in order to prevent crosstalk, and thus it is significantly effective to coat the optical material by using the difference in height  111 .  
         [0000]     (2) Second Embodiment  
         [0157]      FIG. 7  is a drawing showing a second embodiment of the present invention in which a matrix type display device and a manufacturing method thereof in accordance with the present invention are applied to a passive matrix type display device using an EL display device.  
         [0158]      FIG. 7 ( a ) is a plan view showing the arrangement of a plurality of first bus lines  300  and a plurality of second bus lines  310  arranged perpendicularly to the first bus lines  300 , and  FIG. 7 ( b ) is a sectional view taken along line B-B in  FIG. 7 ( a ). The same components as the first embodiment are denoted by the same reference numerals, and description thereof is omitted. Since details of the manufacturing process are also the same as the first embodiment, the process is not shown in the drawings nor described.  
         [0159]     Namely, in this embodiment, an insulation film  320  of Si02, for example, is arranged to surround the predetermined position where the light emitting element  140  is disposed, to form the difference in height  111  between the predetermined position and the periphery thereof.  
         [0160]     Like the first embodiment, this structure is capable of preventing the liquid precursor  114 A and the liquid organic fluorescent material  114 B from flowing out to the periphery during selective coating, and has the advantage of achieving high-precision patterning.  
         [0000]     (3) Third Embodiment  
         [0161]      FIG. 8  is a drawing showing a third embodiment of the present invention in which, like in the first embodiment, a matrix type display device and a manufacturing method thereof in accordance with the present invention are applied to an active matrix type EL display device. Specifically, the difference in height  111  is formed by using the pixel electrode  141 , thereby permitting high-precision patterning. The same components as the above embodiments are denoted by the same reference numerals.  FIG. 8  is a sectional view showing an intermediate step of the manufacturing process, and the steps before and after this step are not shown nor described because they are substantially the same as the first embodiment.  
         [0162]     Namely, in this embodiment, the pixel electrode  141  is formed to have a thickness larger than—a normal thickness to form the difference in height  111  between the pixel electrode  141  and the periphery thereof. In other words, in this embodiment, the difference in height  111  is formed in a convex shape in which the pixel electrode  141  later coated with the optical material is higher than the periphery thereof.  
         [0163]     Like in the first embodiment, in order to form the hole injection layer corresponding to the lower layer of the light emitting element  140 , the liquid (a solution in a solvent) optical material (precursor)  114 A is discharged to coat the optical material on the upper surface of the pixel electrode  141 .  
         [0164]     However, unlike in the first embodiment, the liquid precursor  114 A is coated on the display substrate while the display substrate is reversed, i.e., in the state where the upper surface of the pixel electrode  141  that is coated with the precursor  114 A is turned downward.  
         [0165]     As a result, the liquid precursor  114 A stays on the upper surface of the pixel electrode due to gravity and surface tension, and does not spread to the periphery thereof. Therefore, the liquid precursor  114 A can be solidified by heating or light irradiation to form the same thin hole injection layer as shown in  FIG. 4 ( b ), and this step is repeated to form the hole injection layer. The organic semiconductor film can also be formed by the same method.  
         [0166]     In this way, in this embodiment, the liquid optical material is coated by using the difference in height  111  formed in a convex shape, thereby improving patterning precision of the light emitting element.  
         [0167]     The amount of the liquid optical material staying on the upper surface of the pixel electrode  141  may be adjusted by using inertial force such as centrifugal force or the like.  
         [0000]     (4) Fourth Embodiment  
         [0168]      FIG. 9  is a drawing showing a fourth embodiment of the present invention in which like in the first embodiment, a matrix type display device and a manufacturing method thereof in accordance with the present invention are applied to an active matrix type EL display device. The same components as the above embodiments are denoted by the same reference numerals.  FIG. 9  is a sectional view showing an intermediate step of the manufacturing process, and the steps before and after this step are not shown nor described because they are substantially the same as the first embodiment.  
         [0169]     Namely, in this embodiment, first the reflection electrode  154  is formed on the display substrate  121 , and then the insulation film  320  is formed on the reflection electrode  154  to surround the predetermined position where the light emitting element  140  is arranged later, and to form the difference in height  111  in a concave shape in which the predetermined position is lower than the periphery thereof.  
         [0170]     Like in the first embodiment, the liquid optical material is then selectively coated in the region surrounded by the difference in height  111  by the ink jet method to form the light emitting element  140 .  
         [0171]     On the other hand, scanning lines  131 , signal lines  132 , pixel electrodes  141 , switching thin film transistors  142 , current thin film transistors  143  and an insulation film  240  are formed on a peeling substrate  122  through a peeling layer  152 .  
         [0172]     Finally, the structure peeled off from the peeling layer  152  on the peeling substrate  122  is transferred onto the display substrate  121 .  
         [0173]     In this embodiment, the liquid optical material is coated by using the difference in height  111 , thereby permitting patterning with high precision.  
         [0174]     Further, in this embodiment, it is possible to decrease damage to the base material such as the light emitting element  140  in subsequent steps, or damage to the scanning lines  131 , the signal lines  132 , the pixel electrodes  141 , the switching thin film transistors  142 , the current thin film transistors  143  or the insulation film  240 , due to coating of the optical material.  
         [0175]     Although, in this embodiment, an active matrix type display device is described, a passive matrix type display device may be used.  
         [0000]     (5) Fifth Embodiment  
         [0176]      FIG. 10  is a drawing showing a fifth embodiment of the present invention in which like in the first embodiment, a matrix type display device and a manufacturing method thereof in accordance with the present invention are applied to an active matrix type EL display device.  FIG. 10  is a sectional view showing an intermediate step of the manufacturing process, and the steps before and after this step are not shown nor described because they are substantially the same as the first embodiment.  
         [0177]     Namely, in this embodiment, the difference in height  111  is formed in a concave shape by using the interlevel insulation film  240  to obtain the same operation and effect as the first embodiment.  
         [0178]     Also, since the difference in height  111  is formed by using the interlevel insulation film  240 , a new step is not added, and thus the manufacturing process is not significantly complicated.  
         [0000]     (6) Sixth Embodiment  
         [0179]      FIG. 11  is a drawing showing a sixth embodiment of the present invention in which like in the first embodiment, a matrix type display device and a manufacturing method thereof in accordance with the present invention are applied to an active matrix type EL display device. The same components as the above embodiments are denoted by the same reference numerals.  FIG. 11  is a sectional view showing an intermediate step of the manufacturing process, and the steps before and after this step are not shown and described because they are substantially the same as the first embodiment.  
         [0180]     Namely, in this embodiment, the difference in height  111  is not used for improving pattering precision, but the hydrophilicity of the predetermined position where the liquid optical material is coated is enhanced relative to the hydrophilicity of the periphery thereof to prevent the coated liquid optical material from spreading to the periphery.  
         [0181]     Specifically, as shown in  FIG. 11 , the interlevel insulation film  240  is formed, and then an amorphous silicon layer  155  is formed on the upper surface of the interlevel insulation film  240 . Since the amorphous silicon layer  155  has high water repellency relative to ITO which forms the pixel electrode  141 , a distribution of water repellency and hydrophilicity is formed in which the hydrophilicity of the surface of the pixel electrode  141  is high relative to the hydrophilicity of the periphery thereof.  
         [0182]     Like in the first embodiment, the liquid optical material is then selectively coated on the upper surface of the pixel electrode  141  by the ink jet method to form the light emitting element  140 , and finally the reflection electrode is formed.  
         [0183]     In this way, even in this embodiment, the liquid optical material is coated after a desired distribution of water repellency and hydrophilicity is formed, and thus the patterning precision can be improved.  
         [0184]     Of course, this embodiment can also be applied to a passive matrix type display device.  
         [0185]     Also this embodiment may comprise the step of transferring the structure formed on the peeling substrate through the peeling layer  152  onto the display substrate  121 .  
         [0186]     Although, in this embodiment, the desired distribution of water repellency and hydrophilicity is formed by using the amorphous silicon layer  155 , the distribution of water repellency and hydrophilicity may be formed by using a metal, an anodic oxide film, an insulation film of polyimide, silicon oxide, or the like, or other materials. In a passive matrix display device, the distribution may be formed by using the first bus lines, and in an active matrix type display device, the distribution may be formed by using the scanning lines  131 , the signal lines  132 , the pixel electrodes  141 , the insulation film  240  or the light shielding layer.  
         [0187]     Although, in this embodiment, description is made on the assumption that the liquid optical material is an aqueous solution, a solution of an optical material in another liquid may be used.  
         [0188]     In this case, liquid repellency and lyophiiicity to this solution may be required.  
         [0000]     (7) Seventh Embodiment  
         [0189]     A seventh embodiment of the present invention has the same sectional structure as the fifth embodiment shown in  FIG. 10 , and is thus described with reference to  FIG. 10 .  
         [0190]     Namely, in this embodiment, the interlevel insulation film  240  is formed by using Si02, and the surface of the interlevel insulation film  240  is irradiated with ultraviolet rays. Then the surface of the pixel electrode  141  is exposed, and the liquid optical material is selectively coated thereon.  
         [0191]     In this manufacturing process, not only the difference in height  111  is formed, but also a distribution of high liquid repellency is formed along the surface of the interlevel insulation film  240 , thereby enabling the coated liquid optical material to easily stay at the predetermined position due to both effects, i.e., the difference in height  111  and the liquid repellency of the interlevel insulation film  240 . Namely, since the effects of both the fifth embodiment and the sixth embodiment are exhibited, the patterning precision of the light emitting element  140  can further be improved.  
         [0192]     The time of ultraviolet irradiation may be before or after the surface of the pixel electrode  141  is exposed, and may be appropriately selected in accordance with the material for forming the interlevel insulation film  240  and the material for forming the pixel electrode  141 . Where ultraviolet irradiation is carried out before the surface of the pixel electrode  141  is exposed, since the inner wall of the difference in height  111  has low liquid repellency, the liquid optical material advantageously stays in the region surrounded by the difference in height  111 . Conversely, where ultraviolet irradiation is carried out after the surface of the pixel electrode  141  is exposed, it is necessary to perform vertical irradiation of ultraviolet rays so as to prevent an increase in the liquid repellency of the inner wall of the difference in height  111 . However, since ultraviolet irradiation is performed after the etching step for exposing the surface of the pixel electrode  141 , there is the advantage of eliminating the possibility that the liquid repellency deteriorates in the etching step.  
         [0193]     As the material for forming the interlevel insulation film  240 , for example, photoresist or polyimide may be used. These materials have the advantage that the film can be formed by spin coating.  
         [0194]     For some materials forming the interlevel insulation film  240 , liquid repellency may be enhanced by irradiation of plasma of 02, CF3, Ar or the like, for example, in place of ultraviolet irradiation.  
         [0000]     (8) Eighth Embodiment  
         [0195]      FIG. 12  is a drawing showing an eighth embodiment of the present invention in which, like in the-first embodiment, a matrix type display device and a manufacturing method thereof in accordance with the present invention are applied to an active matrix type EL display device. The same components as the above embodiments are denote.d by the same reference numerals.  FIG. 12  is a sectional view showing an intermediate step of the manufacturing process, and the steps before and after this step are not shown nor described because they are substantially the same as the first embodiment.  
         [0196]     Namely, in this embodiment, neither the difference in height  111  nor the distribution of liquid repellency and lyophilicity is used for improving the patterning precision, but the patterning precision is improved by using attraction force and repulsive force due to a potential.  
         [0197]     As shown in  FIG. 12 , the signals lines  132  and the common current supply lines  133  are driven, and the transistors not shown are turned on and off to form a potential distribution in which the pixel electrode  141  has a negative potential, and the interlevel insulation film  240  has a positive potential. Then the positively charged liquid optical material  114  is selectively coated at the predetermined position by the ink jet method.  
         [0198]     In this way, in this embodiment, a desired potential distribution is formed on the display substrate  121 , and the liquid optical material  114  is selectively coated by using attraction force and repulsive force between the potential distribution and the positively charged liquid optical material  114 , thereby improving the patterning precision.  
         [0199]     Particularly, in this embodiment, since the liquid optical material  114  is charged, the effect of improving the patterning precision is further increased by using not only spontaneous polarization but also electric charge.  
         [0200]     Although in this embodiment the invention is applied to an active matrix type display device, the invention can also be applied to a passive matrix type display device.  
         [0201]     This embodiment may further comprise the step of transferring the structure formed on the peeling substrate  121  through the peeling layer  152  onto the display substrate  121 .  
         [0202]     Also, in this embodiment, the desired potential distribution is formed by successively applying a potential to the scanning lines  131 , and at the same time, applying a potential to the signal lines  132  and the common current supply lines  133 , and applying a potential to the pixel electrodes  141  through the switching thin film transistor  142  and the current thin film transistor  143 . Since the potential distribution is formed by using the scanning lines  131 , the signal lines  132 , the common current supply lines  133  and the pixel electrodes  141 , an increase in the number of the steps can be suppressed. In a passive matrix type display device, the potential distribution may be formed by using the first bus lines or the light shielding layer.  
         [0203]     Although, in this embodiment, a potential is applied to both the pixel electrode  141  and the peripheral interlevel insulation film  240 , the present invention is not limited to this. For example, as shown in  FIG. 13 , a positive potential may be applied only to the interlevel insulation film  240 , with no potential applied to the pixel electrode  141 , and then the liquid optical material  114  may be coated after being positively charged. In this case, since the liquid optical material  114  can securely be maintained in a positively charged state after coating, it is possible to securely prevent the liquid optical material  114  from flowing out to the periphery due to the repulsive force between the optical material  114  and the peripheral interlevel insulation film  240 .  
         [0204]     Unlike in each of the above embodiments, for example, the difference in height  111  may be formed by coating a liquid material or forming a material on the peeling substrate through the peeling layer and then transferring the structure peeled off from the peeling layer on the peeling substrate onto the display substrate.  
         [0205]     Although, in each of the above embodiments, an organic or inorganic EL material is used as the optical material, the optical material is not limited to these materials, and may be a liquid crystal.  
       INDUSTRIAL APPLICABILITY  
       [0206]     As described above, in the present invention, since a liquid optical material is coated by using a difference in height, a desired distribution of liquid repellency and lyophilicity, or a desired potential distribution, there is the effect of improving the patterning precision of the optical material.