Abstract:
A method of fabricating an LCD panel is provided, which forms a uniform gap between a pair of transparent substrates over the whole display area, provides high display quality, and decreases the contamination level to liquid crystal of sealing material. This method comprises the steps of: (a) providing a first transparent substrate; (b) providing a second transparent substrate; (c) forming a first sealing member on the first transparent substrate to surround a display area; the first sealing member being used for sealing a liquid crystal; the first sealing member having a first closed pattern; (d) forming a second sealing member on the first or second substrate to surround the first sealing member; the second sealing member having a second closed pattern; (e) dropping a liquid crystal on the first or second substrate in the display area; (f) coupling the first and second substrates with each other to form a gap between the first and second substrates in a vacuum atmosphere, forming a closed inner space between the first and second substrates by the first and second sealing members; the liquid crystal being confined in the inner space; (g) curing the second sealing member after the step (f), and (h) curing the first sealing member after the step (f). The steps (g) and (h) are performed at different times from each other.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a Liquid-Crystal Display (LCD) panel and a method of fabricating the same and more particularly, to a LCD panel that provides a substantially uniform cell gap between opposing substrates and that displays images with excellent quality over the whole display area, and a method of fabricating the panel.  
           [0003]    2. Description of the Prior Art  
           [0004]    A LCD panel generally has a configuration including a pair of transparent, opposed substrates (e.g., glass substrates) fixed at a specific gap, a frame-shaped sealing member located between the substrates to couple the substrates with each other so as to form an inner space therebetween, spacer particles dispersed in the space to keep the gap, and a liquid crystal filled in the space.  
           [0005]    With the LCD panels of the active-matrix addressing type, typically, Thin-Film Transistors (TFTs) are formed on one of the pair of substrates and a color filter is formed on the other. Usually, the substrate with TFTs is termed the “TFT array substrate” while the substrate with a color filter is termed the “color filter substrate”.  
           [0006]    Conventionally, to fill the inner space between the substrates with liquid crystal, the “substrate dipping process” and the “liquid crystal dispensing process” have been developed and used practically. The substrate dipping process was developed in early days and has ever been used in practice and thus, the technique for performing the substrate dipping process has been diversified. On the other hand, the liquid crystal dispensing process was developed in recent years and has been getting popular. However, the technique for performing the liquid crystal dispensing process has not been diversified compared with the substrate dipping process. Thus, there is the demand to grow or expand this technique.  
           [0007]    With both the first and second methods of fabricating the LCD panel using the substrate dipping process and the liquid crystal dispensing process, the same process steps are carried out in their early stages. For example, in the patterning process, necessary parts or elements (e.g., dielectric layers, transparent electrodes, switching elements or devices, and color filter layers) are formed on the respective substrates. In the rubbing process subsequent to the patterning process, alignment layers (e.g., polyimide layers) are formed by printing on the inner surfaces of the substrates and then, the layers are rubbed to form grooves extending in the same direction or different directions for orientating the liquid crystal molecules toward a specific direction or directions. The following process steps are different in the fabrication methods using the dipping and dispensing methods.  
           [0008]    FIGS.  1  and FIGS. 2A to  2 C show the LCD panel fabrication method using the substrate dipping process, which may be termed the first prior-art method later.  
           [0009]    After the rubbing process C 1  as explained above, the sealing member formation process C 2  is carried out. In this process C 2 , as shown in FIG. 2A, two frame-shaped sealing members  132  are formed on the inner surface of a lower transparent substrate  131  at a specific distance. Each of the members  132  is used for the LCD panel. The member  132  is continuously written to draw a rectangular frame on the substrate  11  by dispensing a material for the sealing member  132  from the nozzle of a known dispenser. A proper epoxy-system thermosetting resin is used for the member  132 . Needless to say, the member  132  may be formed by the known screen printing method.  
           [0010]    As shown in FIG. 2A, the frame-shaped sealing member  132  has a pattern of an approximately rectangular closed curve with an opening  133 . The member  132  is formed to surround the display area  114 , in other words, the member  132  extends around the periphery of the area  114 . The opening  133  is used as an inlet through which liquid crystal is injected into the inside of the member  132 .  
           [0011]    After the sealing member formation process C 2 , the substrate coupling process C 3  is carried out. In this process, another transparent substrate (not shown, an upper transparent substrate), is overlaid the lower substrate  131  so as to overlap entirely with each other, forming a substrate assembly. At this time, each cell on the lower substrate  131  is opposed to the corresponding cell on the upper substrate.  
           [0012]    Thereafter, a pressure is applied to the substrate assembly with a pressing plate, setting the gap between the lower and upper substrates at a desired value.  
           [0013]    If spacer particles are used for keeping the gap between the substrates, they are spayed or arranged on the inner surface of the lower substrate  131  in the display area  114  surrounded by the sealing member  132  prior to the substrate coupling process C 3 .  
           [0014]    Subsequent to the substrate coupling process C 3 , the sealing member curing process C 4  is carried out. In this process, the sealing member  132  is cured with the heater provided on the pressing plate. This process C 4  may be carried out by placing the substrate pair in an oven and by heating the atmosphere in the oven up to a specific temperature.  
           [0015]    Thereafter, the substrate cutting process C 5  is carried out. In this process, the substrate pair or substrate assembly is cut to divide it into LCD panel assemblies  100 . The cutting operation of the substrate pair is performed along the cutting line that surrounds each sealing member  132 , forming a rectangular-ring-shaped specific area outside the display area  114  in each panel assembly  100 . The assembly  100  thus divided is shown in FIG. 2B.  
           [0016]    In the method explained here, two panel assemblies  100  are produced from the substrate pair. The way to form a plurality of panel areas in the same substrate pair like this has been extensively performed in practice, because it is advantageous to raising the productivity.  
           [0017]    Typically, the position of the cutting line is set in such a way that the cutting line involves a necessary module or unit including the driver circuit which will be provided on the lower substrate  131  outside the sealing member  132  in a subsequent process.  
           [0018]    After the substrate cutting process C 5 , the liquid crystal injecting process C 6  is performed, which utilizes typically a vacuum atmosphere. In this case, the panel assembly  100  is placed in a vacuum chamber of a specific vacuum apparatus at an atmospheric pressure. Next, the air in the chamber is evacuated and then, the assembly  100  is dipped into a liquid crystal stored in the container so that the inlet  133  of the assembly  100  is immersed in the crystal. Thereafter, the pressure in the chamber is raised gradually toward the atmospheric pressure, thereby injecting the crystal into the inner space of the assembly  100  due to the pressure difference between the inner space and the outside.  
           [0019]    In the process C 6  utilizing a vacuum atmosphere, the liquid crystal can be injected into the space of the panel assembly  100  until the pressure difference between the inner space and the outside is equal to zero. Typically, it takes about 10 hours to fill the inner space of the assembly  10  with the liquid crystal.  
           [0020]    Subsequent to the liquid crystal injecting process C 6 , the inlet closing or blocking process C 7  is performed. In this process, as shown in FIG. 2C, a thermosetting blocking material  134  (e.g., thermosetting epoxy resin) is attached to the inlet  133  ant then, the material  134  is heated to be cured. Thus, the inlet  133  is blocked by the material  134 . At this time, a proper pressure may be applied to the panel assembly  100  under control to generate a force drawing the material  134  into the space. This is to ensure the blocking of the inlet  133  by the material  134 .  
           [0021]    The liquid crystal thus injected into the inner space and filling the same forms a liquid crystal layer  115  between the two substrates.  
           [0022]    In the polarizer plate attaching process C 8 , a polarizer plate (not shown) is attached to the outer surface of each of the lower and upper substrate. The polarizer plate is provided to allow the component of light whose plane of polarization is in a specific direction to selectively pass through. The plates on the two substrates are fixed in such a way that their polarization directions are perpendicular.  
           [0023]    Through the above-described process steps, the LCD panel  100   a  is completed, as shown in FIG. 2C.  
           [0024]    FIGS.  3 , and FIGS. 4A and 4C show the LCD panel fabrication method using the liquid crystal dispensing process, in which a primary or main sealing member for sealing a liquid crystal and a secondary or auxiliary sealing member for keeping the inner space between the substrates at a specific vacuum condition are used. This method may be termed the second prior-art method later.  
           [0025]    After the rubbing process B 1  which is the same as the process A 1  as explained above, the sealing member formation process B 2  is carried out. In this process B 2 , as shown in FIG. 4A, two frame-shaped primary sealing members  220  are formed on a lower transparent substrate  201  at a specific distance. Also, a frame-shaped secondary sealing member  212  is formed on the substrate  201  to surround the two members  220  at a specific distance. The primary members  220  may be formed on the lower substrate  201  while the secondary member  212  may be formed on another substrate (i.e., an upper substrate).  
           [0026]    Each of the primary members  220  is used for the LCD panel. Each of the primary members  220  and the secondary member  212  is continuously written to draw a rectangular frame on the substrate  131  by dispensing a material for the sealing member  220  and  212  from the nozzle of a known dispenser. A proper acrylic-system ultraviolet (UV)-curing resin is used for the members  220  and  212 . Needless to say, the members  220  and  212  may be formed by the known screen printing method.  
           [0027]    As shown in FIG. 4A, each of the frame-shaped primary sealing members  220  has a pattern of an approximately rectangular closed curve without any opening. The member  220  is formed to surround the display area  214 , in other words, the member  220  extends around the periphery of the area  214 . On the other hand, the frame-shaped secondary sealing members  212  has a pattern of an approximately rectangular closed curve without any opening. The member  212  is formed to involve the primary members  220  and to extend along the periphery of the substrate  201 . As seen from the explanation and FIG. 4A, no inlet for injecting a liquid crystal is provided on the substrate  201 . This is unlike the previously-explained first method using the substrate dipping process shown in FIGS.  1  and FIGS. 2A to  2 C.  
           [0028]    After the sealing member formation process B 2 , the liquid crystal dispensing and substrate coupling process B 3  is carried out. In this process, unlike the previously-explained first method using the substrate dipping process, a liquid crystal is dispensed on the inner surface of the lower substrate  201  prior to coupling the substrates.  
           [0029]    The assembly apparatus used for this purpose comprises typically a pressuring mechanism and an evacuating mechanism.  
           [0030]    The pressuring mechanism includes an upper surface plate movable vertically and a lower surface plate movable horizontally. When the assembly of the lower and upper substrates is located between the lower and upper surface plates, it may be applied with a pressure as desired. The lower plate is larger in size than the upper plate and thus, the peripheral area of the lower plate protrudes from the upper plate when the upper plate is placed on the lower plate.  
           [0031]    The evacuating mechanism has a lid formed by a top wall and a side wall extending along the periphery of the top wall, forming an inner space. The bottom of the lid is open. The upper surface plate of the pressuring mechanism is located in the inner space of the lid. When the lid along with the upper surface plate is lowered toward the lower surface plate of the pressuring mechanism until the opening lower end of the lid contacts closely the protruding periphery of the lower surface plate, a closed space is formed in the lid. The closed space, which is sandwiched by the lower and upper surface plates in the lid, communicates with a pumping system by way of tubes.  
           [0032]    The upper surface plate is movable vertically with respect to the lid and therefore, the distance between the upper and lower surface plates is changeable. Thus, the pressure applied to the substrate assembly in the closed space is adjustable minutely.  
           [0033]    The liquid crystal dispensing and substrate coupling process B 3  is carried out in the following way using the above-described assembly apparatus.  
           [0034]    First, the upper substrate  202  is attached to the upper surface plate of the assembly apparatus by suction while the lower substrate  201  is attached to the lower surface plate thereof by suction. Next, a liquid crystal is dropped in the display areas  214  of the lower substrate  201  which is surrounded by the respective primary sealing members  220 .  
           [0035]    Thereafter, the lower plate is slid to the position just below the upper plate and aligned thereto. The upper plate is lowered to be overlaid on the lower substrate  201  and then, the lid is lowered, contacting closely the bottom end of the lid with the periphery of the lower plate. Thus, the closed space is formed between the upper and lower plates.  
           [0036]    Following this, the air existing in the closed space thus formed is evacuated by the evacuating mechanism, forming a vacuum atmosphere that surrounds the lower and upper substrates  201  and  202 . The pressing force of the upper plate to the lower plate is raised to apply a pressure to the upper substrate  202 . Thus, the gap  205  between the lower and upper substrate  201  and  202  is minutely adjusted as desired.  
           [0037]    Through the above-described processes, the lower substrate  201  is coupled with the upper substrate  202  by way of the primary and secondary sealing members  220  and  212 , forming a liquid crystal layer  215  in the gap  205 . In other words, a LCD panel assembly  200  comprising the lower and upper substrates  201  and  202 , the sealing members  220  and  212 , and the liquid crystal layer  215  is produced. The state at this stage is shown in FIG. 4B.  
           [0038]    Subsequently, the applied pressure to the upper plate is removed and then, the lower plate on which the LCD panel assembly  200  is placed is slid outwardly from the overlaying position. The assembly  200  is subjected to a diselectrification process and then, taken out of the assembly apparatus and sent to the subsequent sealing member curing process B 4 .  
           [0039]    In the sealing member curing process B 4 , the sealing members  220  and  212  are cured by irradiating specific UV light to the members  220  and  212 . This process is performed in 30 minutes after the space that surrounds the assembly  200  has been released to the atmospheric pressure.  
           [0040]    Next, the gap uniformizing process B 5  is carried out. The uniformization of the gap  205  between the lower and upper substrates  201  and  202  coupled together progresses due to the pressing force caused by the difference between the atmospheric pressure applied to the outer surfaces of the panel assembly  200  and the inner pressure thereof. Specifically, due to the deformation of the lower and upper substrate  201  and  202  and the deformation of the liquid crystal layer  215  in the gap  205 , the gap  205  is uniformized gradually. If spacer particles are dispersed in the gap  205 , the particles are deformed by the pressing force as well, resulting in the gap  205  being uniformized.  
           [0041]    Even after the pressure difference between the atmospheric pressure and the inner pressure of the panel assembly  200  decreases during the gap uniformizing process, the vacuum space  221  formed between the primary sealing members  220  and the secondary sealing member  212  tends to keep the pressure difference unchanged. Therefore, after the assembly  200  is left in the atmospheric pressure, the uniformizing process B 5  of the gap  205  continues until the pressing force generated by the atmospheric pressure balances the stress of the assembly  200 .  
           [0042]    If the primary and secondary sealing members  220  and  212  are left uncured after the panel assembly  200  is left in the atmospheric pressure, the secondary sealing member  212  tends to break. In this case, the vacuum space  221  tends to disappear and as a result, the gap uniformization does not progress at desired high level. At the same time, due to the break of the secondary sealing member  212 , there is a danger that the atmospheric pressure applies directly to the primary sealing member  220 , resulting in the member  220  itself being broken. Accordingly, as described above, the time to start the curing process is set in 30 minutes after the space that surrounds the assembly  200  has been released to the atmospheric pressure, thereby setting the gap uniformizing period to overlap with the periods before and after the curing process.  
           [0043]    After the gap uniformizing process B 5 , the substrate cutting process B 6  is performed In this process, the panel assembly  200  is cut to divide it into LCD panels  200   a  (see FIGS. 5A and 5B). The cutting operation of the panel assembly  200  is performed along the cutting line that surrounds each primary sealing member  220 , forming a rectangular-ring-shaped specific area outside the display area  114  in each panel  200   a.  The panel  200   a  thus divided is shown in FIGS. 5A and 5B. Thus, the LCD panel  200   a  is produced.  
           [0044]    Typically, the position of the cutting line is set in such a way that the cutting line involves a necessary module or unit including the driver circuit which will be provided on the lower substrate  201  outside the primary sealing member  220  in a subsequent process.  
           [0045]    After the substrate cutting process B 6 , the polarizer plate attaching process B 7  is carried out. In this process, a polarizer plate (not shown) is attached to the outer surface of each of the lower and upper substrate  201  and  202  of each LCD panel  200   a.  The polarizer plate is provided to allow the component of light whose plane of polarization is in a specific direction to selectively pass through. The plates on the two substrates are fixed in such a way that their polarization directions are perpendicular.  
           [0046]    Through the above-described process steps, the LCD panel  200   a  is completed. As seen from the above explanation, the liquid crystal injection and inlet blocking processes are unnecessary and thus, there is an advantage that the overall process time is decreased compared with the method using the liquid crystal injection process.  
           [0047]    With the second method using the liquid crystal dispensing process, the gap uniformizing process B 5  is performed after curing the primary sealing members  220 . Thus, the deformation of the members  220  follow sufficiently the deformation of the lower and upper substrates  201  and  202  and thus, some dimensional difference occurs between the gap in the periphery of the display area  214  (i.e., the vicinity of the primary sealing member  220 ) and the gap at the center of the area  214 . As a result, there arises a problem that the gap is nonuniform in the entire area  214 .  
           [0048]    For example, as shown in FIG. 5A, the gap g 2  in the vicinity of the primary sealing member  220  is greater than the gap g 1  in the center of the area  214  (i.e., g2&gt;g1). Alternately, as shown in FIG. 5B, the gap g 2  is less than the gap g 1  (i.e., g2&lt;g1). As a result, in the periphery of the area  214  (i.e., in the vicinity of the member  220 ), the gap varies (i.e., decreases or increases) from the member  220  to the center of the area  214 . If the gap change becomes excessively large, concentric interference fringes occur in the periphery of the area  214 .  
           [0049]    The interference fringes occur due to the following principle.  
           [0050]    As shown in FIG. 6, a pair of transparent substrates  71  and  72  are placed to be opposed to each other, where the gap between the substrates  71  and  72  varies. If monochromic incident light with a wavelength of λ enters the pair of substrates  71  and  72 , a light beam reflected by the inner surface of the substrate  71  and a light beam reflected by the inner surface of the substrate  72  interferes. Although other reflected light beams are present and they may interfere, they are omitted for simplification of discussion here.  
           [0051]    If the gap is uniform (i e., d1=d2=d3) , the interference state are equal in the whole substrates  71  and  72  and as a result, no bright and dark fringe appears. However, the gap is nonuniform as shown in FIG. 6, some bright and dark interference fringes appear according to the gap change.  
           [0052]    The condition of the interference fringes seems that the fringes are formed at the positions where the gap difference is equal to (λ/2). The reason of this is explained below.  
           [0053]    First, the gap at the first bright part B 1  is defined as d 1  while the gap at the second bright part B 2  next to the part B 1  is defined as d 2 . In this case, the difference between the optical path lengths at the parts B 1  and B 2  is given as 2(d2−d1), because the light beam goes and returns between the substrates  71  and  72 .  
           [0054]    The first and second bright conditions are established when the difference between the optical path lengths at the parts B 1  and B 2  is equal to the wavelength λ, i.e., λ=2(d2−d1). Thus, the gap difference at the parts B 1  and B 2  is given as (d2−d1)=λ/2.  
           [0055]    Usually, the wavelength λ of the incident light is approximately 500 to 550 nm (i.e., 0.5 to 0.55 μm) and thus, the gap difference at the parts B 1  and B 2  is approximately 0.25 μm.  
           [0056]    Practically, the gap between the substrates  71  and  72  is filled with a liquid crystal. Thus, the light propagating in the crystal has a wavelength of λ/n, where n is the refractive index of the crystal. As a result, (d2−d1)=λ/2 n  is established.  
           [0057]    For example, if the refractive index n of the crystal is 1.4 (i.e., n=1.4) and the wavelength λ of the incident light (green light) is 550 nm (λ=550 nm), the gap difference is given as (d2−d1)=λ/2 n =550/(1.4×2)=196 nm≈0.2 μm.  
           [0058]    With the second prior-art method with the liquid crystal dispensing process, the gap difference as large as 0.2 μm occurs frequently. Thus, the concentric interference fringes are formed and as a result, the display quality degrades.  
           [0059]    Moreover, with the second prior-art method using the liquid crystal dispensing process, there is the following problem about the material of the primary sealing members  220 .  
           [0060]    Specifically, in this method, thermosetting resins have been used for the sealing members  220  for a long time. At present, various kinds of thermosetting resins are available for this purpose and therefore, an optimum thermosetting resin is selectable as desired. For example, a thermosetting resin with a less contamination property to a specific liquid crystal to be used is available for the members  220 .  
           [0061]    Also, since no UV light is used, there is no possibility that the liquid crystal and/or the orientation layers degrade in the fabrication process sequence. However, the thermosetting resins used for this purpose are low in viscosity and therefore, they tend to have a long curing time.  
           [0062]    Furthermore, unlike this, with the first prior-art method using the substrate dipping process, the pressure of the atmosphere surrounding the panel  100  does not vary prior to the sealing member curing process C 4 . Thus, there is no possibility that the pressing force is applied to the uncured sealing member due to the atmospheric pressure.  
           [0063]    With the second prior-art method using the liquid crystal dispensing process, it is essential that the atmospheric pressure is applied to the uncured sealing members  220  and  212  in the sealing member curing and substrate coupling process B 4 . This means that the material for the members  220  and  212  needs to have a viscosity that withstand the force due to the atmospheric pressure and a short curing time that allows the material for the members  220  and  212  to cure before the members  220  and  212  break due to the force. It is difficult to find or select the material satisfying these two requirements. As a result, UV curing resins are usually used for the members  220  and  212 .  
           [0064]    If UV curing resins are used, there arises a problem that the liquid crystal and the alignment layers tend to degrade due to irradiation of UV light.  
           [0065]    Also, UV curing resins available to sealing members  220  and  212  have been used in practice in recent years. Thus, only a few resins of this type are available for this purpose. For example, there is a case where only one resin of this type is accessible for the practical purpose. Accordingly, UV curing resins, which are higher in contamination property to the liquid crystal than thermosetting resins, are essentially selected.  
           [0066]    To decrease the contamination level to liquid crystal, there is a problem that the contamination level of UV curing resins to liquid crystal needs to be improved in the future. Also, it is essential to use UV curing resins in spite of their bad contamination property to liquid crystal.  
           [0067]    With the first prior-art method using the substrate dipping process, since a thermosetting resin is used for the sealing members  132 , there is an advantage about the contamination level to liquid crystal. However, as explained previously, there is a problem that the injection time of liquid crystal is long. There is another problem that the connection part of the inlet  133  of the member  132  to the blocking member  134  tends to be applied with stress concentration, resulting in the member  134  being broken.  
           [0068]    In addition, from the viewpoint of shortening the overall process time, the second prior-art method using the liquid crystal dispensing process tend to be used extensively instead of the first prior-art method using the substrate dipping process.  
         SUMMARY OF THE INVENTION  
         [0069]    Accordingly, an object of the present invention is to provide an LCD panel and a method of fabricating the panel that form a uniform gap between a pair of substrates over the whole display area.  
           [0070]    Another object of the present invention is to provide an LCD panel and a method of fabricating the panel that provide high display quality.  
           [0071]    A still another object of the present invention is to provide an LCD panel and a method of fabricating the panel that decreases the contamination level to liquid crystal of sealing material.  
           [0072]    A further object of the present invention is to provide an LCD panel and a method of fabricating the panel that prevent liquid crystal and alignment layers from degrading due to UV light irradiation.  
           [0073]    A still further object of the present invention is to provide an LCD panel and a method of fabricating the panel that decrease the time for uniformizing the gap between the substrates.  
           [0074]    A still further object of the present invention is to provide an LCD panel and a method of fabricating the panel that improves the strength of the sealing members against stress concentration.  
           [0075]    The above objects together with others not specifically mentioned will become clear to those skilled in the art from the following description.  
           [0076]    According to a first aspect of the present invention, a method of fabricating an LCD panel is provided, which comprises the steps of:  
           [0077]    (a) providing a first transparent substrate  
           [0078]    (b) providing a second transparent substrate;  
           [0079]    (c) forming a first sealing member on the first transparent substrate to surround a display area;  
           [0080]    the first sealing member being used for sealing a liquid crystal;  
           [0081]    the first sealing member having a first closed pattern;  
           [0082]    (d) forming a second sealing member on the first or second substrate to surround the first sealing member;  
           [0083]    the second sealing member having a second closed pattern;  
           [0084]    (e) dropping a liquid crystal on the first or second substrate in the display area;  
           [0085]    (f) coupling the first and second substrates with each other to form a gap between the first and second substrates in a vacuum atmosphere, forming a closed inner space between the first and second substrates by the first and second sealing members;  
           [0086]    the liquid crystal being confined in the inner space;  
           [0087]    (g) curing the second sealing member after the step (f); and  
           [0088]    (h) curing the first sealing member after the step (f).  
           [0089]    The steps (g) and (h) are performed at different times from each other.  
           [0090]    With the method fabricating an LCD panel according to the first aspect of the present invention, the second substrate is coupled with the first substrate and then, the second sealing member is cured and subsequently, the first sealing member is cured. In other words, the time for curing the second sealing member is apart from the time for curing the first sealing member.  
           [0091]    Since the second sealing member is cured prior to the first sealing member, the inside of the coupled substrates is kept at a vacuum state, thereby preventing the first sealing member from being applied directly with the atmospheric pressure. Thus, there is no need to use a high viscosity material enough to withstand the atmospheric pressure for the first sealing member and to cure the first sealing member promptly not to be broken due to application of the atmospheric pressure. In other words, a low viscosity material can be used for the first sealing member and at the same time, the first sealing member can be kept uncured for a desired period of time.  
           [0092]    Also, the second sealing member can be cured after the first and second substrates are coupled together. Thus, the vacuum level in the inner space of the coupled first and second substrates can be kept for a long time. In other words, if the coupled first and second substrates are left in the atmospheric pressure after the second sealing member is cured, the first and second substrates can be pressed sufficiently by the atmospheric pressure. Accordingly, if the coupled first and second substrates are left in the atmospheric pressure to uniformize the gap between the coupled first and second substrates after the second sealing member is cured, almost all the gap uniformizing process can be conducted in the state where the first sealing member is not cured. In this case, the first sealing member can deform according to the deformation of the coupled first and second substrates, in other words, the deformation of the first and second substrates is not restricted by the height of the cured first sealing member. Therefore, the gap difference between the central and peripheral parts of the display area is decreased, thereby uniformizing the gap over the whole display area. As a result, the gap difference can be limited within the range where no interference fringes occur, which means that poor display quality is not caused by the interference fringes, improving the display quality. If a low viscosity material is used fro the first sealing member, this advantage of improved quality is enhanced.  
           [0093]    On the other hand, because there is no need to use a high viscosity material for the first sealing member and to cure the first sealing member promptly not to be broken, the selectable range for materials available to the first sealing member is expanded. In other words, as a material for the first sealing member, a thermosetting resin which is lower in viscosity and longer in curing time than UV curing resins may be used. In particular, this is valuable because it enables addition of a variety of thermosetting resins to the material for the first sealing member. For example, a material with a less contamination property to liquid crystal is selectable according to the type of liquid crystal to be used. If a thermosetting resin is used for the first sealing member, no UV light is irradiated to the liquid crystal and alignment layers, which leads to an additional advantage that a high-quality LCD panel can be fabricated without using UV light.  
           [0094]    Moreover, if a thermosetting resin is used for the first sealing member and a UV curing resin is used f or the second sealing member, the curing times for the first and second sealing members can be easily separated from each other. This is due to the following reason.  
           [0095]    Specifically, when UV light is irradiated to the coupled first and second substrates to thereby cure the second sealing member, the first sealing member is never cured. Contrarily, when heat is applied to the coupled first and second substrates to thereby cure the first sealing member, the second sealing member is never cured. Thus, the separation of the curing times for the first and second sealing members can be ensured easily.  
           [0096]    Since the second sealing member is directly applied with the atmospheric pressure, Thus, to ensure a desired vacuum state in the coupled first and second substrates by the second sealing member, the second sealing member needs to have a resistance high enough for the pressure. On the other hand, it is preferred that the first sealing member is easily deformed to improve the gap uniformity and to shorten the gap uniformizing time. Therefore, if the material for the first sealing member is lower in viscosity than the material for the second sealing member, the required characteristics for the first and second sealing members can be enhanced without any difficulty.  
           [0097]    The first sealing member is continuous to form a closed pattern without any inlet for liquid crystal injection and no blocking material is used for blocking or closing the inlet. Thus, stress concentration does not occur in the first sealing member, which leads to improvement of the breaking resistance of the first sealing member.  
           [0098]    In summary, with the method of fabricating an LCD panel according to the first aspect of the invention, more uniform gap is formed in the whole display area and the display quality is enhanced. The contamination of liquid crystal due to the sealing material is suppressed or eliminated and the degradation of the liquid crystal and alignment layers induced by UV light irradiation is prevented. The gap uniformizing time is shortened and the mechanical strength of the first sealing member is increased.  
           [0099]    According to a second aspect of the present invention, another method of fabricating an LCD panel is provided, which comprises the steps of:  
           [0100]    (a) providing a first transparent substrate;  
           [0101]    (b) providing a second transparent substrate;  
           [0102]    (c) forming a first sealing member on the first transparent substrate to surround a display area;  
           [0103]    the first sealing member being used for sealing a liquid crystal;  
           [0104]    the first sealing member having a first closed pattern;  
           [0105]    (d) forming a second sealing member on the first or second substrate to surround the first sealing member;  
           [0106]    the second sealing member having a second closed pattern;  
           [0107]    (e) dropping a liquid crystal on the first or second substrate in the display area;  
           [0108]    (f) coupling the first and second substrates with each other to form a gap between the first and second substrates in a vacuum atmosphere, forming a closed inner space between the first and second substrates by the first and second sealing members;  
           [0109]    the liquid crystal being confined in the inner space;  
           [0110]    (g) curing the second sealing member after the step (f);  
           [0111]    (h) keeping the coupled first and second substrates in an atmosphere that uniformizes the gap between the coupled first and second substrates after the step (h); and  
           [0112]    (i) curing the first sealing member after the step (h).  
           [0113]    With the method fabricating an LCD panel according to the second aspect, the step (h) is additionally provided to the method according to the first aspect. Thus, because of substantially the same reason as explained in the method of the first aspect, there are the same advantages as those in the method of the first aspect.  
           [0114]    In a preferred embodiment of the method according to the first or second aspect of the invention, the step (h) of curing the first sealing member is performed in a period ranging from 5 minutes to 120 minutes after the step (g) of curing the second sealing member is completed. If the period is less than 5 minutes, the obtainable gap uniformity is insufficient. If the period is greater than 120 minutes, the productivity is lowered, which is not practical.  
           [0115]    In another preferred embodiment of the method according to the first or second aspect of the invention, the first sealing member is made of a thermosetting resin.  
           [0116]    In still another preferred embodiment of the method according to the first or second aspect of the invention, the first sealing member is made of a thermosetting resin and the second sealing member is made of a UV curing resin.  
           [0117]    According to a third aspect of the present invention, a still another method of fabricating an LCD panel is provided, which comprises the steps of:  
           [0118]    (a) providing a first transparent substrate;  
           [0119]    (b) providing a second transparent substrate;  
           [0120]    (c) forming a first sealing member on the first transparent substrate to surround a display area;  
           [0121]    the first sealing member being made of a thermosetting resin;  
           [0122]    the first sealing member being used for sealing a liquid crystal;  
           [0123]    the first sealing member having a first closed pattern;  
           [0124]    (d) forming a second sealing member on the first or second substrate to surround the first sealing member;  
           [0125]    the second sealing member being made of a UV curing resin;  
           [0126]    the second sealing member having a second closed pattern;  
           [0127]    (e) dropping a liquid crystal on the first or second substrate in the display area;  
           [0128]    (f) coupling the first and second substrates with each other to form a gap between the first and second substrates in a vacuum atmosphere, forming a closed inner space between the first and second substrates by the first and second sealing members;  
           [0129]    the liquid crystal being confined in the inner space;  
           [0130]    (g) curing the second sealing member after the step (f); and  
           [0131]    (h) curing the first sealing member after the step (f).  
           [0132]    The steps (g) and (h) are performed at different times from each other.  
           [0133]    With the method fabricating an LCD panel according to the third aspect, the first sealing member is made of a thermosetting resin while the second sealing member is made of a UV curing resin. The other steps are substantially the same as the method of the first aspect. Thus, because of substantially the same reason as explained in the method of the first aspect, there are the same advantages as those in the method of the first aspect.  
           [0134]    In a preferred embodiment of the method according to the first or second or third aspect of the invention, a material for the first sealing member is lower in viscosity than a material fort the second sealing member.  
           [0135]    In another preferred embodiment of the method according to the first or second or third aspect of the invention, a material for the first sealing member has a viscosity in a range from 1,000 N·s/m 2  to 10,000 N·s/m 2 . If the viscosity of the material for the first sealing member is less than 1,000 N·s/m 2 , the uncured first sealing member has an insufficient resistance against the applied pressure. If the viscosity of the material for the first sealing member is greater than 10,000 N·s/m 2 , the gap uniformity is insufficient and the time for gap uniformization is too long.  
           [0136]    In still another preferred embodiment of the method according to the first or second or third aspect of the invention, a material for the second sealing member has a viscosity in a range from 6,000 N·s/m 2 to 100,000 N·s/m 2 . If the viscosity of the material for the second sealing member is less than 6,000 N·s/m 2 , the uncured second sealing member has an insufficient resistance against the applied pressure. If the viscosity of the material for the second sealing member is greater than 100,000 N·s/m 2 , the second sealing member is difficult to have the second closed pattern as desired.  
           [0137]    In a further preferred embodiment of the method according to the first or second or third aspect of the invention, a material for the first sealing member has a viscosity in a range from 1,000 N·s/m 2  to 10,000 N·s/m 2  and a material for the second sealing member has a viscosity in a range from 6,000 N·s/m 2  to 100,000 N·s/m 2 .  
           [0138]    According to a fourth aspect of the present invention, an LCD panel is provided, which comprises:  
           [0139]    (a) a first transparent substrate;  
           [0140]    (b) a second transparent substrate coupled with the first substrate to form a gap between the first and second substrates;  
           [0141]    a closed inner space being formed between the first and second substrates by a sealing member;  
           [0142]    the sealing member being formed to surround a display area;  
           [0143]    the sealing member having a closed pattern; and  
           [0144]    (c) a liquid crystal layer formed in the inner space between the first or second substrate.  
           [0145]    The gap has a value in a periphery of the display area and a value at a center of the display area, where the values have a difference within a limit for causing no interference fringe.  
           [0146]    With the LCD panel according to the fourth aspect of the present invention, the sealing member is formed to surround the display area and has the closed pattern and therefore, no stress concentration occurs in or near the member. Thus, the resistance of the member against the applied pressure is enhanced.  
           [0147]    Also, the sealing member is made of a thermosetting resin, it has a less contamination property to the liquid crystal layer and at the same time, the liquid crystal layer and alignment layers are not affected badly by UV light.  
           [0148]    Since the values of the gap in the periphery of the display area and at the center of the display area have a difference within a limit for causing no interference fringe, high display quality is realized over the whole display area.  
           [0149]    According to a fifth aspect of the present invention, another LCD panel is provided, which comprises:  
           [0150]    (a) a first transparent substrate;  
           [0151]    (b) a second transparent substrate coupled with the first substrate to form a gap between the first and second substrates;  
           [0152]    a closed inner space being formed between the first and second substrates by a sealing member;  
           [0153]    the sealing member being formed to surround a display area;  
           [0154]    the sealing member being made of a thermosetting resin;  
           [0155]    the sealing member having a closed pattern; and  
           [0156]    (c) a liquid crystal layer formed in the inner space between the first or second substrate.  
           [0157]    The gap has a value in a periphery of the display area and a value at a center of the display area, where the values have a difference within a limit for causing no interference fringe.  
           [0158]    With the LCD panel according to the fifth aspect of the present invention, because of the same reason as the panel according to the fourth aspect, there are the same advantages as those in the panel of the fourth aspect.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0159]    In order that the present invention may be readily carried into effect, it will now be described with reference to the accompanying drawings.  
         [0160]    [0160]FIG. 1 is a flowchart showing the process steps of a first prior-art method of fabricating an LCD panel, which includes the liquid crystal dipping process.  
         [0161]    [0161]FIG. 2A is a schematic plan view showing the lower transparent substrate, on which the sealing members are formed in the process C 2  of the flowchart in FIG. 1.  
         [0162]    [0162]FIG. 2B is a schematic cross-sectional view along the line parallel to the lower and upper substrates showing the structure of the panel cut in the process C 5  of the flowchart in FIG. 1, where the liquid crystal is not injected into the space yet.  
         [0163]    [0163]FIG. 2C is a schematic cross-sectional view along the line parallel to the lower and upper substrates showing the structure of the panel in the process C 7  of the flowchart in FIG. 1, where the liquid crystal inlet is blocked by the blocking member.  
         [0164]    [0164]FIG. 3 is a flowchart showing the process steps of a second prior-art method of fabricating an LCD panel, which includes the liquid crystal dropping process.  
         [0165]    [0165]FIG. 4A is a schematic plan view showing the lower transparent substrate, on which the primary and secondary sealing members are formed in the process B 2  of the flowchart in FIG. 3.  
         [0166]    [0166]FIG. 4B is a schematic cross-sectional view along the line perpendicular to the lower and upper substrates showing the structure of the panel after the gap is uniformized in the process B 5  of the flowchart in FIG. 3, where the liquid crystal has been filled into the space.  
         [0167]    [0167]FIG. 5A is a schematic cross-sectional view along the line perpendicular to the lower and upper substrates showing the structure of the panel cut in the process B 6  of the flowchart in FIG. 3, where the gap g 1  is less than the gap g 2 .  
         [0168]    [0168]FIG. 5B is a schematic cross-sectional view along the line perpendicular to the lower and upper substrates showing the structure of the panel cut in the process B 6  of the flowchart in FIG. 3, where the gap g 1  is greater than the gap g 2 .  
         [0169]    [0169]FIG. 6 is an enlarged, partial cross-sectional of a pair of opposing transparent substrates, which shows the principle of the interference fringes.  
         [0170]    [0170]FIG. 7 is a flowchart showing the process steps of a method of fabricating an LCD panel according to an embodiment of the invention.  
         [0171]    [0171]FIG. 8A is a schematic plan view showing the lower transparent substrate, on which the primary and secondary sealing members are formed in the process A 2  of the flowchart in FIG. 7.  
         [0172]    [0172]FIG. 8B is a schematic cross-sectional view along the line perpendicular to the lower and upper substrates showing the structure of the panel after the gap is uniformized in the process A 5  of the flowchart in FIG. 7.  
         [0173]    [0173]FIG. 8C is a schematic cross-sectional view along the line perpendicular to the lower and upper substrates showing the structure of the panel cut in the process A 7  of the flowchart in FIG. 7.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0174]    Preferred embodiments of the present invention will be described in detail below while referring to the drawings attached.  
         [0175]    A method of fabricating an LCD panel according to an embodiment of the invention comprises the steps as shown by the flowchart in FIG. 7.  
         [0176]    In the pre-process A 0 , a pair of transparent substrates  1  and  2  for the LCD panel are prepared, as shown in FIG. 8B. The substrates  1  and  2  are typically made of transparent glass. On the substrate  1  (i.e., the lower substrate), necessary parts and elements such as active elements (e.g., TFTs), data lines, and scan lines, are provided. On the other substrate  2  (i.e., the upper substrate), a color filter layer and other necessary parts are formed. An alignment layer (e.g., polyimide resin, not shown) is formed on the inner surface of each of the lower and upper substrates  1  and  2 .  
         [0177]    In the rubbing process A 1  after the pre-process A 0 , the alignment layers on the lower and upper substrates  1  and  2  are rubbed with a buff wrapped around the rotatable roller in specific directions. Thus, minute grooves are formed on the surface of each alignment layer.  
         [0178]    In the sealing member formation process A 2  after the rubbing process A 1 , as shown in FIG. 8A, two primary sealing members  13  and a secondary sealing member  12  are formed on the lower substrate  1 . Each of the primary sealing members  13  has a pattern of a rectangular closed curve without any opening, in other words, the member  13  extends around the periphery of the display area  14 . The secondary sealing member  12  has a pattern of a rectangular closed curve as well. The primary members  13  are formed on the lower substrate  1  to be apart from each other at a specific distance. The secondary sealing member  12  is formed to surround the two primary members  13  at a specific distance. In other words, the member  12  is formed to involve the primary members  13  and to extend along the periphery of the substrate  1 . The primary members  13  may be formed on the lower substrate  1  while the secondary member  12  may be formed on the upper substrate  2 , and vice versa.  
         [0179]    Each of the primary sealing members  13  is used for the LCD panel. Each of the primary members  13  and the secondary sealing member  12  is continuously written to draw a rectangular frame on the lower substrate  1  by dispensing proper materials for the sealing members  13  and  12  from the nozzle of a known dispenser. Unlike the first prior-art method shown in FIG. 1, no inlet for injecting liquid crystal is provided in the primary sealing members  13 . Needless to say, the members  13  and  12  may be formed by the known screen printing method.  
         [0180]    A proper epoxy-system thermosetting resin is used for the primary members  13 . A proper acrylic-system UV-curing resin is used for the secondary member  12 . The material for the members  13  is lower in viscosity than the material for the member  12 . Preferably, the material for the primary members  13  has a viscosity in the range from 1,000 N·s/m 2  to 10,000 N·s/m 2  while the material for the secondary member  12  has a viscosity in the range from 6,000 N·s/m 2  to 100,000 N·s/m 2 .  
         [0181]    In the liquid crystal dispensing and substrate coupling process A 3  after the sealing member forming process A 2 , a liquid crystal is dispensed on the lower substrate  1  prior to coupling the substrates  1  and  2 .  
         [0182]    The assembly apparatus used for this process A 3  comprises typically a pressuring mechanism and an evacuating mechanism.  
         [0183]    The pressuring mechanism includes an upper surface plate movable vertically and a lower surface plate movable horizontally. When the assembly of the lower and upper substrates is located between the lower and upper surface plates, it may be applied with a pressure as desired. The lower plate is larger in size than the upper plate and thus, the peripheral area of the lower plate protrudes from the upper plate when the upper plate is placed on the lower plate.  
         [0184]    The evacuating mechanism has a lid formed by a top wall and a side wall extending along the periphery of the top wall, forming an inner space. The bottom of the lid is open. The upper surface plate of the pressuring mechanism is located in the inner space of the lid. When the lid along with the upper surface plate is lowered toward the lower surface plate of the pressuring mechanism until the opening lower end of the lid contacts closely the protruding periphery of the lower surface plate, a closed space is formed in the lid. The closed space, which is sandwiched by the lower and upper surface plates in the lid, communicates with a pumping system by way of tubes.  
         [0185]    The upper surface plate is movable vertically with respect to the lid and therefore, the distance between the upper and lower surface plates is changeable. Thus, the pressure applied to the substrate assembly in the closed space is adjustable minutely.  
         [0186]    The liquid crystal dispensing and substrate coupling process A 3  is carried out in the following way using the above-described assembly apparatus. In the following explanation, FIG. 8B is referred.  
         [0187]    First, the upper substrate  2  is attached to the upper surface plate of the assembly apparatus by suction while the lower substrate  1  is attached to the lower surface plate thereof by suction. Next, a liquid crystal is dropped in the display areas  14  of the lower substrate  1  which is surrounded by the respective primary sealing members  13 .  
         [0188]    Thereafter, the lower plate is slid to the position just below the upper plate and aligned thereto. The upper plate is lowered to be overlaid on the lower substrate  1  and then, the lid is lowered, contacting closely the bottom end of the lid with the periphery of the lower plate. Thus, the closed space is formed between the upper and lower plates.  
         [0189]    Following this, the air existing in the closed space thus formed is evacuated by the evacuating mechanism, forming a vacuum atmosphere that surrounds the lower and upper substrates  1  and  2 . The pressing force of the upper plate to the lower plate is raised to apply a pressure to the upper substrate  2 . Thus, the gap  5  between the lower and upper substrate  1  and  2  is minutely adjusted as desired.  
         [0190]    Through the above-described processes, the lower substrate  1  is coupled with the upper substrate  2  by way of the primary and secondary sealing members  13  and  12 , forming a liquid crystal layer  15  in the gap  5 . In other words, a LCD panel assembly  30  comprising the lower and upper substrates  1  and  2 , the sealing members  13  and  12 , and the liquid crystal layer  15  is produced. The state at this stage is shown in FIG. 8B.  
         [0191]    Subsequently, the applied pressure to the upper plate is removed and then, the lower plate on which the LCD panel assembly  30  is placed is slid outwardly from the overlaying position. The assembly  30  is subjected to a diselectrification process and then, taken out of the assembly apparatus and sent to the subsequent sealing member curing process A 4 .  
         [0192]    In the secondary sealing member curing process A 4 , the secondary sealing member  12  is cured by irradiating specific UV light to the member  12 . This process is performed immediately after the space that surrounds the LCD panel assembly  30  has been released to the atmospheric pressure.  
         [0193]    To perform this process, the LCD panel assembly  30  is taken out of the assembly apparatus and then transferred to a UV irradiation apparatus, in which UV light is irradiated to the assembly  30 . In this case, it will take several minutes for the secondary sealing member  12  to cure completely after the assembly  30  has been subjected to the atmospheric pressure.  
         [0194]    Alternately, a UV irradiation apparatus may be built in the assembly apparatus. In this case, after the lower and upper substrates  1  and  2  are coupled together, UV light is irradiated to the secondary sealing member  12  in the vacuum atmosphere prior to the release to the atmospheric pressure. There is an additional advantage that the closed space  21  can be kept in a high vacuum state.  
         [0195]    Next, the gap uniformizing process A 5  is carried out. The uniformization of the gap  5  between the lower and upper substrates  1  and  2  coupled together progresses due to the pressing force caused by the difference between the atmospheric pressure applied to the outer surfaces of the LCD panel assembly  30  and the inner pressure thereof. Specifically, due to the deformation of the lower and upper substrate  1  and  2  and the deformation of the liquid crystal layer  15  in the gap  5 , the gap  5  is uniformized gradually. If spacer particles are dispersed in the gap  5 , the particles are deformed by the pressing force as well, resulting in the gap  5  being uniformized.  
         [0196]    In the process A 5 , the primary sealing members  13  are uncured and the material for the secondary sealing member  12  is low in viscosity and therefore, the members  13  are sandwiched by the lower and upper substrate  1  and  2  with pressure. Thus, the members  13  deform sufficiently according to the deformation of the substrates  1  and  2 . This means that the gap  5  is uniformized not only in the central part of the display area  14  but also the periphery of the area  14  at approximately the same level. As a result, the value of the gap  5  in the periphery of the area  14  and the value at the central part of the area  14  have a difference within the limit for causing no interference fringe. In particular, the fact that the material for the first sealing members  13  is lower in viscosity than the material for the secondary sealing member  12  contributes the decrease of the time required for gap uniformization.  
         [0197]    Additionally, in the gap uniformizing process, the vacuum space  21  formed by the primary sealing members  13  and the secondary sealing member  12  between the substrates  1  and  2  keeps the pressure difference from the atmospheric pressure even after the pressure difference between the liquid crystal layer  15  and the atmospheric pressure decreases. As a result, the gap uniformization can be realized at high level. Therefore, after the panel assembly  30  is left in the atmospheric pressure, the uniformizing process A 5  of the gap  5  continues until the pressing force generated by the atmospheric pressure balances the stress of the LCD panel assembly  30 .  
         [0198]    If the primary and secondary sealing members  13  and  12  are left uncured after the LCD panel assembly  30  is left in the atmospheric pressure, the secondary sealing member  12  tends to break. In this case, the vacuum space  21  tends to disappear and as a result, the gap uniformization does not progress at desired high level. At the same time, due to the break of the secondary sealing member  12 , there is a danger that the atmospheric pressure applies directly to the primary sealing members  13 , resulting in the assembly  30  itself being broken. However, in the method according to the embodiment, the time to start the curing process is set immediately after the space that surrounds the assembly  30  has been released to the atmospheric pressure. Thus, there is no danger that the assembly  30  itself is broken.  
         [0199]    After the gap uniformizing process A 5 , the main sealing member curing process A 6  is performed in a time ranging from 5 minutes to 120 minutes.  
         [0200]    In the process A 6 , the panel assembly  30  is heated or sintered to cure the primary sealing members  13 . It is ideal that the main sealing members  13  are kept uncured in the gap uniformizing process A 5  and that the curing of the members  13  is completed immediately after the gap uniformizing process A 5  is finished. If the heating time is shorter than 5 minutes, the gap uniformizing time is insufficient. If the heating time is longer than 120 minutes, the productivity is lowered. As a result, it is practical that a thermosetting resin having a curing time of approximately 30 minutes to 120 minutes at a temperature of 70° C. to 150° C. is used.  
         [0201]    Since the primary sealing members  13  are made of a thermosetting resin, it takes several tens minutes to cure the members  13 . However, in the process A 6 , the members  13  are surrounded by the secondary sealing member  12  that has been already cured and that is not broken by the atmospheric pressure. That is, the members  13  are protected by the member  12  from the atmospheric pressure. Accordingly, there is an additional advantage that the heating time for the primary members  13  can be set considerably long without anxiety about the members  13  being broken by the atmospheric pressure.  
         [0202]    For example, the secondary member  12  is cured in 5 minutes after the panel assembly  30  is subjected to the atmospheric pressure. The curing of the primary members  13  is started at the time 50 minutes after the curing of the member  12  is completed. The heating time for the members  13  is set at 30 minutes. In this case, the gap uniformizing process A 5  is 55 minutes (=5+50 minutes). In this case, the 50 minutes includes the heating time of 30 minutes.  
         [0203]    If the atmospheric pressure does not balance the stress of the assembly  30  yet after the primary members  13  is completely cured, the gap uniformization progresses even after the primary members  13  are cured. In other words, part of the gap uniformizing process A 5  may be placed after the primary sealing member curing process A 6 . To enhance the gap uniformity and to shorten the time for the gap uniformizing process A 5 , it is preferred to increase the time for the gap uniformizing process A 5  that is carried out while the members  13  are uncured.  
         [0204]    After the primary sealing member curing process A 6 , the substrate cutting process A 7  is performed. In this process, the panel assembly  30  is cut to divide it into LCD panels  30   a.  The cutting operation of the assembly  30  is performed along the cutting line that surrounds each primary sealing member  13 , forming a rectangular-ring-shaped specific area outside the display area  14  in each panel  30   a.  The panel  30   a  thus divided is shown in FIG. 8C. Thus, the LCD panel  30   a  is produced.  
         [0205]    After the substrate cutting process A 7 , the polarizer plate attaching process A 8  is carried out. In this process, a polarizer plate (not shown) is attached to the outer surface of each of the lower and upper substrate  1  and  2  of the panel  30   a.  The polarizer plate is provided to allow the component of light whose plane of polarization is in a specific direction to selectively pass through. The plates on the two substrates are fixed in such a way that their polarization directions are perpendicular.  
         [0206]    Through the above-described process steps, the LCD panel  30   a  is completed. As seen from the above explanation, the liquid crystal injection and inlet blocking processes are unnecessary and thus, there is an advantage that the overall process time is decreased compared with the method using the liquid crystal injection process.  
         [0207]    With the method of fabricating a LCD panel according to the embodiment of the invention using the liquid crystal dispensing process, the material for the primary sealing members  13  is a thermosetting resin with a viscosity in a range from 1,000 N·s/m 2  to 10,000 N·s/m 2 , which is lower than the viscosity of the material for the secondary sealing member  12 . The member  12  is cured immediately after the member  12  is subjected to the atmospheric pressure and then, the primary members  13  are cured in the time from 5 minutes to 120 minutes.  
         [0208]    Therefore, the deformation of the primary sealing members  13  follow sufficiently the deformation of the lower and upper substrates  1  and  2  and thus, it is not limited by the height of the members  13 . This means that the dimensional difference occurring between the gap  5  in the periphery of the display area  14  (i.e., the vicinity of the primary sealing members  13 ) and the gap  5  at the center of the area  14  decreases. As a result, the gap  5  is substantially uniform in the entire area  14 , in other words, the difference of the gap  5  in the a periphery of the area  14  and at the center of the area  14  is within the limit for causing no interference fringe. This leads to high or excellent display quality.  
         [0209]    Since the primary sealing members  13  are made of a thermosetting resin, the contamination to the liquid crystal layer  15  is decreased and the degradation of the layer  15  and the alignment layers due to UV light irradiation is prevented. Because of the above-identified viscosity of the members  13 , the time required for the gap uniformizing process is shortened.  
         [0210]    As the material for the secondary sealing member  12 , any material with a viscosity ranging from 6,000 N·s/m 2  to 100,000 N·s/m 2  may be used. The material for the member  12  is not limited to a UV curing resin if it can be cured before the primary sealing members  13  are cured.  
         [0211]    With the method according to the embodiment of the invention, the material for the primary sealing members  13  is a thermosetting resin with a viscosity ranging from 1,000 N·s/m 2  to 10,000 N·s/m 2 , which is lower than the viscosity of the material for the secondary sealing member  12 . The material for the member  12  is a UV curing resin with a viscosity ranging from 6,000 N·s/m 2  to 100,000 N·s/m 2 . These setting on the viscosity is determined or selected have the technical significance described below.  
         [0212]    With the primary sealing members  13 , the gap uniformity needs to be raised and the gap uniformizing time needs to be shortened. In other words, the viscosity of the material for the members  13  is determined in such a way that the gap uniformity level is high enough for preventing the interference fringes and that the gap uniformizing time is shortened as much as possible. Thus, it is not practical to use a material with a viscosity greater than 10,000 N·s/m 2  for the members  13 .  
         [0213]    To uniformize the gap  5 , it is preferred that the viscosity of the material for the members  13  is as low as possible. However, the lowest viscosity is determined due to the following reason.  
         [0214]    Specifically, after the substrate coupling process A 3 , the coupled substrates  1  and  2  are subjected to the atmospheric pressure and thus, the liquid crystal layer  15  is expanded. The gap uniformizing process is carried out while the layer  15  is surrounded by the primary members  13 . At this time, due to the pressure difference between the vacuum space  21  and the layer  15 , the members  13  are kept to be applied with a pressure directing from the layer  15  to the space  21 . Thus, the members  13  need to have a viscosity that withstands this pressure. It is not practical to use a material with a viscosity less than 1,000 N·s/m 2  for the members  13 .  
         [0215]    On the other hand, the material for the secondary sealing member  12  has a viscosity that withstands the vacuum atmosphere during the time from the exposure to the atmospheric pressure to the curing of the member  12 . Thus, it is practical to use a material with a viscosity greater than 6,000 N·s/m 2  for the member  12 .  
         [0216]    To keep the vacuum state, it is preferred that the viscosity of the material for the secondary member  12  is as high as possible. However, if it is excessively high, the member  12  is difficult or unable to be written as desired by using a dispenser. To make it possible to draw a desired pattern with the material with a dispenser of this type, it is not practical to use a material with a viscosity greater than 100,000 N·s/m 2  for the member  12 . If the screen printing method is used for this purpose, the viscosity needs to be lowered further. Thus, it is practical that the viscosity of the material for the member  12  is equal to or less than 100,000 N·s/m 2 .  
         [0217]    Since the secondary member  12  needs to keep the vacuum atmosphere, the material for the member  12  needs to have as a high viscosity as possible. However, it is preferred that the material for the member  13  has a lower viscosity than the material for the member  12  to facilitate the gap uniformization.  
         [0218]    Because of the above-described technical significance, in the method according to the embodiment of the invention, the viscosity of the material for the primary members  13  is set to be lower than the material for the secondary member  12 . Also, the viscosity of the material for the member  13  is in the range from 1,000 N·s/m 2  to 10,000 N·s/m 2  and at the same time, the viscosity of the material for the member  12  is in the range from 6,000 N·s/m 2  to 100,000 N·s/m 2 .  
         [0219]    Any epoxy-system thermosetting resin may be used if it has a viscosity from 1,000 N·s/m 2  to 10,000 N·s/m 2 . Any acrylic-system UV curing resin may be used if it has a viscosity from 6,000 N·s/m 2  to 100,000 N·s/m 2 . However, the invention is not limited to these materials.  
         [0220]    While the preferred form of the present invention has been described, it is to be understood that modifications will be apparent to those skilled in the art without departing from the spirit of the invention. The scope of the present invention, therefore, is to be determined solely by the following claims.