Apparatus for manufacturing liquid crystal panel and method thereof

An apparatus for manufacturing a liquid crystal panel in which two substrates are faced to each other with spacers interposed therebetween, applied with heat and pressure in an overlapped condition, and adhesive arranged between two substrates is cured for fixing, characterized in that at least one of a pair of pressurizing plates for applying pressure to the two substrates is a graphite plate and in that upper and lower pressurizing plates are made to be of different rigidity. The graphite plate of low rigidity is made to stick to the substrate, and shifts between substrates can be prevented while securing uniformity in gaps between substrates.

BACKGROUND OF THE INVENTION
 The present invention relates to an apparatus for manufacturing a liquid
 crystal panel and a method thereof. More particularly, it relates to an
 apparatus for manufacturing a liquid crystal panel and a method thereof in
 which two substrates are faced to each other with spacers interposed
 therebetween, and while applying pressure to these substrates, adhesive
 arranged at peripheral portions are cured to be adhered to the substrates.
 FIGS. 6 and 7 are schematic, sectional views for explaining a manufacturing
 method by means of a fixing apparatus for a liquid crystal panel as
 described in Japanese Unexamined Patent Publication No. 88018/1982. In
 FIGS. 6 and 7, 1 and 2 denote a pair of upper and lower substrates which
 are a color filter substrate and a TFT substrate having desired patterns
 formed thereon. Between the upper substrate 1 and the lower substrate 2,
 there are provided a plurality of spacers 51 of approximately 5 microns
 for maintaining the clearance, and the upper substrate 1 and the Lower
 substrate 2 are fixedly attached together at their peripheral portions via
 adhesive 52. This adhesive 52 finally serves as a bulkhead for enclosing
 liquid crystal within the substrates 1,2. 53 denotes a base (surface
 plate) that is made, for instance, of stainless steel, and 54 denotes a
 bendable material which covers at least one of the substrates. The
 bendable material might be a polyester film or silicone rubber sheet.
 According to this conventional manufacturing method for a panel, the
 spacers 51 are dispersed on an inner surface of either of the upper and
 lower substrates 1,2 and after applying adhesive to a peripheral portion
 of the other substrate, both are overlapped at high positioning accuracy.
 Further, the whole temperature is raised while applying pressure to the
 substrates, the adhesive 52 is cured, and the upper and lower substrates
 1,2 are fixedly attached together without generating any shifts.
 At this time, the substrates are maintained in a vessel comprising at least
 partly of a bendable material, at least one of the substrates is covered
 with the bendable material, and fixing of the substrates is performed in a
 condition in which the interior of the vessel is decompressed or pressure
 is applied on the vessel from the exterior. By the above arrangements,
 pressure can be applied to the substrates in an uniform manner.
 Such a method in which the substrates are applied with pressure by means of
 a material having bendable characteristics is effective in remarkably
 improving the uniformity of pressure application than compared to methods
 in which surface plates of high rigidity are employed. Consequently,
 irregularities or uniformities in display owing to deficiencies in gaps
 can be decreased.
 A manufacturing method for panels employing a heating method is proposed in
 Japanese Unexamined Patent Publication No. 232420/1993. As shown in FIG.
 8, there are respectively provided a plurality of hot plates 55 above and
 below substrates 1,2 in this method so that the whole panel can be heated.
 With this arrangement, characteristics such as rapid heating and soaking
 can be improved than compared to a method in which a side surface of the
 panel is heated employing a heater in a furnace.
 However, while the manufacturing method according to FIGS. 6 and 7 is
 effective to some extent with respect to deficiencies in gaps, it cannot
 prevent shifts in lateral directions of the upper and lower substrates 1,2
 or generation of wraps in the substrates. Especially in cases in which two
 pairs of substrates have been arranged in an aligning manner in a single
 vessel for the sake of improving productivity, it was found that the shift
 in lateral directions became larger. Further, this method presents a
 drawback that the substrates are apt to camber, depending on the way of
 heat transmission, since heating of the substrates 1,2 is performed in a
 furnace. That is, when heat is transmitted from downward the furnace,
 there is generated wrap like a bimetal, since the surface plate 53 of
 stainless steel is first heated, and since the thermal expansion
 coefficient of the surface plate 53 of stainless steel is larger than
 those of the substrates 1,2. If the wrap in the substrate becomes not less
 than a certain value, it cannot be assembled into a product and thus
 becomes a defective article. Especially, since requirements with respect
 to shapes of substrates are becoming increasingly higher accompanying
 requirements of thin-sizing of products in these years, this results in a
 drawback that the yield is further decreased. In case a gradually heating
 process or a method in which the rigidity is increased (the thermal
 capacity is increased) is employed for the sake of preventing cambers, it
 will not be acceptable in terms of productivity.
 On the other hand, in the method of FIG. 8 in which hot plates 55 are
 employed, heat is transmitted from the upper and lower substrates so that
 occurrence of wraps is decreased; however, it cannot prevent shifts of the
 upper and lower substrates in lateral directions by several .mu.m, and in
 case request for the positioning accuracy become higher for the sake of
 improving the performance of liquid crystal, shifts between substrates;
 will not be within acceptable values. Further, it has become relevant from
 experiments that in the prior art arrangement, the amount of shift became
 larger, than compared to a case in which the substrates 1,2 are disposed
 in the center of the surface plate, when they were shifted from the center
 or when small substrates have been disposed in an aligning manner. From
 these results, it has become relevant from experiments that shear stress
 is generated between the surface plate and the substrate and between both
 substrates owing to differences in coefficients of thermal expansion of
 upper and lower surface plates or differences in friction coefficients
 between a surface plate and a substrate depending on the position of the
 substrates and the upper and lower surface plates. Power is most apt to be
 released especially between substrate 1 and substrate 2 that are adhered
 to each other only at their peripheral portions by means of soft adhesive
 (that is cured after heating) so that shift is generated between the
 substrates 1,2.
 While increase of thermal capacity of the hot plates is effective for
 securing soaking characteristics in this conventional method, it presented
 a drawback that this was performed at the expense of heating/cooling
 speed.
 Further, in surface plates made of stainless steel that are designed to be
 flat at a room temperature, undulations might occur in the surface plates
 themselves depending on the temperature distribution in the surface
 plates. Therefore, there was presented a drawback that wraps occurred in
 substrates that were fixedly attached as to be parallel thereto at a
 certain area of dispersion.
 The present invention has been made in view of the above circumstances, and
 it is an object thereof to provide a manufacturing apparatus for a liquid
 crystal panel and a method thereof capable of decreasing amounts of
 overlapping shifts after fixing two substrates.
 SUMMARY OF THE INVENTION
 In accordance with a first aspect of the present invention, there is
 provided an apparatus for manufacturing a liquid crystal panel in which
 two substrates are faced to each other with spacers interposed
 therebetween, applied with heat and pressure in an overlapped condition,
 and adhesive arranged between the two substrates is cured for fixing,
 characterized in that at least one of a pair of pressurizing plates for
 applying pressure to the two substrates is a graphite plate and in that
 upper and lower pressurizing plates are made to be of different rigidity.
 It is preferable that at least one of the pressurizing plates is of a
 multi-layered arrangement, and a graphite plate is employed as a part of
 the multi-layered arrangement.
 The pressurizing plate of multi-layered arrangement is preferably provided
 with an inner space in at least one point positioned between the layers.
 It is preferable that the pressurizing plate of multi-layered arrangement
 is provided with a path for cooling at a nearer side with respect to the
 substrate and with a heater at a farther side with respect to the
 substrate.
 A coating film is preferably provided on a surface of the graphite plate.
 It is preferable that a graphite plate of high rigidity is fixed to a base
 by means of a pin or a heat insulator in order to deform a surface of the
 graphite plate in a convex or concave manner.
 It is preferable that there is provided a mechanism in which a closed space
 is formed by means of a pressurizing plate of low rigidity and an upper
 lid, and a substrate disposed in an exterior space with respect to the
 closed space is applied with pressure by making a pressure of the closed
 space higher relative to the exterior space.
 It is preferable that a frame body of a thickness approximately identical
 to that of the two substrates is arranged between the pair of pressurizing
 plates as to enclose the substrates, wherein the frame body is formed of
 tungsten, molybdenum, alloys thereof, graphite or iron-nickel alloy.
 It is preferable that differences in level are provided in the frame body,
 wherein the differences in level are set such that a height of an inner
 surface located on the side of the substrate is identical to or lower than
 the height of the substrate, and that a height of an outer surface on the
 opposing side is higher than the height of the inner surface.
 In accordance with a second aspect of the present invention, there is
 further provided a method for manufacturing a liquid crystal panel in
 which two substrates are faced to each other with spacers interposed
 therebetween, applied with heat and pressure in an overlapped condition,
 and adhesive arranged between the two substrates is cured for fixing,
 characterized in that at least one of a pair of pressurizing plates for
 applying pressure to the two substrates is a graphite plate and in that
 upper and lower pressurizing plates are made to be of different rigidity.
 According to the present invention, the arrangement for applying pressure
 to the substrates is composed of a graphite plate of thermal expansion
 coefficient close to that of a glass substrate and of a plate of low
 rigidity, and the pressurizing plate of low rigidity is made to stick to
 the substrate by providing differences in rigidity, shifts in substrates
 can be prevented while securing uniformity in gaps between substrates.
 According to another embodiment of the present invention, at least one of
 the pressurizing plates is made to be of multi-layered arrangement, and
 graphite plate is used at a part thereof. Further, a space has been
 provided at least at one portion between layers of this pressurizing plate
 of multi-layered arrangement. With these arrangements, soaking
 characteristics and flatness of the graphite plate can be improved.
 According to a further embodiment of the present invention, the
 pressurizing plate of multi-layered arrangement is provided with a path
 for cooling on a nearer side with respect to the substrate and a heater on
 a farther side with respect to the substrate. With this arrangement, rapid
 cooling/heating is enabled.
 According to a yet further embodiment of the present invention, a coating
 film is provided on the surface of the graphite plate. With this
 arrangement, long life of the graphite plate is enabled, and improvements
 in yield are also enabled.
 According to a still further embodiment of the present invention, in order
 to deform the surface of the graphite plate in a convex or concave manner
 the graphite plate of high rigidity is fixed by means of a plurality of
 pins or heat insulator. With this arrangement, it is enabled to control
 the shape of the finished substrate.
 According to another embodiment of the present invention, there is provided
 a mechanism in which a closed space is formed by means of a pressurizing
 plate of low rigidity and an upper lid, and a substrate disposed in an
 exterior space with respect to the closed space is applied with pressure
 by making a pressure of the closed space higher relative to the exterior
 space. With this arrangement, occurrence of bubbles is prevented since
 adhesive that is applied between the substrates will not be exposed to
 decompression, and consequently, leakage of liquid crystal can be
 prevented.
 According to a further embodiment of the present invention, a frame body of
 a thickness approximately identical to that of the two substrates is
 arranged between the pair of pressurizing plates as to enclose the
 substrates, wherein the frame body is formed of tungsten, molybdenum,
 alloys thereof, graphite or iron-nickel alloy. With this arrangement, the
 pressurizing plates are made to uniformly contact with the substrates in
 flat conditions.
 According to a still further embodiment of the present invention,
 differences in level are provided in the frame body, wherein the
 differences in level are set such that a height of an inner surface
 located on the side of the substrate is identical to or lower than the
 height of the substrate, and that a height of an outer surface on the
 opposing side is higher than the height of the inner surface, so that the
 pressure in the peripheral portions of the substrates can be heightened
 and the adhesive can be smashed in a stable manner. With this arrangement,
 shifts of substrates can be further decreased and uniformity in gaps
 between substrates can be secured.
 According to the method of the present invention, two substrates are
 applied with pressure by employing a graphite plate for at least one of a
 pair of pressurizing plates for applying pressure to the two substrates
 and upper and lower pressurizing plates are made to be of different
 rigidity. With this arrangement, the graphite plate of low rigidity is
 made to stick to the substrate so that shifts between substrates can be
 prevented while securing uniformity in gaps between substrates.

DETAILED DESCRIPTION
 EMBODIMENT 1
 A manufacturing apparatus for a liquid crystal panel according to an
 embodiment of the present invention and a method thereof is shown in FIG.
 1. 1,2 denote upper and lower substrates, 5 a graphite plate of high
 rigidity which is a pressurizing plate, and 6 a graphite plate of how
 rigidity which is another pressurizing plate. In this embodiment, four
 heaters 7 for heating are inserted into the graphite plate 5 of high
 rigidity. In order to secure soaking characteristics of the surface of the
 graphite plate 5, the heaters 7 are preferably set to be as remote as
 possible from the substrate 2. Further, 8 is a frame body disposed as to
 enclose around the substrates 1,2, which thickness is identical to that of
 the total thickness of the substrates 1,2. 9 is an upper lid for
 supporting the graphite plate 6 of low rigidity wherein the graphite plate
 6 of low rigidity is supported by means of a hook 10 and a hook (not
 shown). On the upper lid 9, there is provided a suction hole 11 so that
 the graphite plate 6 of low rigidity can be made to stick to the upper lid
 9 by performing vacuum drawing. 12 denotes an O ring comprising elastic
 member which is deformed when the graphite plate 5 of high rigidity and
 the graphite plate 6 of low rigidity are overlapped with each other and
 cuts off the interior surrounded by the graphite plates 5,6 and the
 exterior, wherein the interior is enabled to perform vacuum exhaust by
 means of vacuum piping 13. 14 denotes a base onto which the graphite plate
 5 of high rigidity is placed via heat insulator 15 which might, for
 instance, be ceramics.
 Basic operations will now be explained. As shown in FIG. 1, the substrates
 1,2 are disposed onto the graphite plate 5 while the graphite plate 5 of
 high rigidity and graphite plate 6 of low rigidity are in opened
 conditions. Then, the upper lid 9 is descended so that the graphite plate
 5 of high rigidity and graphite plate 6 of low rigidity come in contact
 via the O ring 12. At this time, the graphite plate 6 of low rigidity is
 set to be apart from the hook 10 and not to contact the upper lid 9. That
 is, the graphite plate 6 of low rigidity is maintained in a freely
 deformable condition. With this arrangement, the graphite plate 6 of low
 rigidity is made capable to follow the substrate 1 also in case the
 apparatus is heated/cooled. On the contrary, in case the graphite plate 6
 of low rigidity is fixedly attached to the hook 10 for maintaining the
 plate, there is presented a drawback that occurrence of a wrap in the
 graphite plate 6 of low rigidity is by all means unavoidable due to
 thermal deformation. Next, in case the interior enclosed by the graphite
 plates 5,6 is vacuum exhausted via the vacuum piping 13, the graphite
 plate 6 of low rigidity deforms and sticks as to be parallel to the
 substrate 1 without being restrained by any other members. Then, the
 graphite plate 5 of high rigidity is heated by the heaters 7, the
 substrates 1,2 are heated through heat transmission and are fixedly
 attached to each other through adhesive, similarly to conventional
 methods. Though the substrates 1,2 or graphite plates 5,6 are thermally
 expanded accompanying the heating, shifts can be restricted since the
 thermal expansion coefficients of the substrates 1,2 and the graphite
 plates 5,6 are substantially identical.
 After expiry of a prederermined time necessary for the curing of the
 adhesive, the heaters 7 are turned off, the pressure of the interior is
 returned to atmospheric pressure, and the upper lid 9 is lifted to take
 the substrates 1,2 out. At this time, by making the graphite plate 6 of
 low rigidity sucked at the upper lid 9, it is made possible to rapidly
 cool the graphite plate 5 of low rigidity to the temperature of the upper
 lid 9. These operations are repeated so that other substrates 1,2 are
 fixedly attached to each other. It should be noted that while graphite
 plates are employed as the pair of pressurizing plates for applying
 pressure to the two substrates in this embodiment, the present invention
 is not limited to this, and out of the pair of pressurizing plates, at
 least one of the pressurizing plates might be of graphite plate and the
 upper and lower pressurizing plates might be set to be of different
 rigidity.
 Further, the same effects can be obtained by using polytetra phloroethylene
 (PTFE) sintered glass fiber cloth of a similar thermal expansion
 coefficient instead of using a graphite plate 6 of low rigidity. However,
 though favorable effects could be obtained at initial stages of
 manufacturing when using a molybdenum plate which is a metal material of
 similar thermal expansion coefficient, it was found that repetitive usage
 thereof presented a drawback that the flatness was gradually degraded and
 deficiencies in gap or shifts occurred between the substrates 1,2. This is
 considered to be due to the fact that plastic deformation which is
 characteristic to metal materials locally occurs while repetitive
 heating/cooling is performed. Experiments have also been made with
 molybdenum of various thickness; however, in case the thickness is
 increased to a thickness at which no variations in flatness occur, the
 bendability which is a primary purpose was lost and resulted in
 deficiencies of gaps owing to occurrences of irregularities in pressure,
 or shifts occurred owing to unevenness in frictional force, and
 consequently, it was not suitable for usage.
 By employing the above arrangements and processes, it has been enabled to
 avoid occurrence of shifts between the substrates 1,2. That is, the
 arrangement according to this embodiment is capable to largely decrease
 shear stress generated between substrates.
 EMBODIMENT 2
 While the graphite plate 5 of high rigidity has been arranged to be of a
 single-layered arrangement in Embodiment 1, soaking characteristics of
 temperature within the graphite plate can be secured by arranging it to be
 of multi-layered arrangement. A sectional view of an apparatus for
 manufacturing a liquid crystal panel of this arrangement is shown in FIG.
 2. For the multi-layered structure, an inner space 17 is provided between
 a first graphite plate 5a of high rigidity into which a heater 7a is
 inserted and a second graphite plate 5b of high rigidity into which a
 cooling water piping 16 is inserted, and a heat insulator 15a of ceramics
 is disposed into the inner space 17. The heat insulator 15a functions as
 spacers for restricting deformation of the graphite plate 5b due to
 existence of the inner space 17. An example is shown in which a second
 heater 7b is provided at the upper lid 9.
 Operations of the above described arrangement will now be explained. First,
 the first graphite plate 5a of high rigidity is heated by the heater 7a.
 At this time, heat is conducted to the second graphite plate 5b of high
 rigidity via a peripheral portion of the first graphite plate 5a of high
 rigidity and, though only by small amounts, via the heat insulator 15a,
 and simultaneously, heat is transferred to the second graphite plate 5b of
 high rigidity via an air layer of the inner space 17. In case the plate is
 not of multi-layered arrangement, it is general that the temperature of
 the central portion becomes high; however, by inserting the heater 7a into
 the first graphite plate 5a of high rigidity that is remote from the
 substrates 1,2, the heat flow through the heat conduction from the
 peripheral portion becomes large, whereby it is enabled to heat the
 substrates 1,2 in a soaking manner. It should be noted that the
 temperature distribution can be controlled by altering the area of contact
 of the peripheral portion, the material for the heat insulator 15a or the
 contact area thereof, or the thickness of the air layer. At this time, by
 simultaneously inserting a second heater 7b into the upper lid 9, the
 graphite plate 6 of low rigidity can be indirectly heated, whereby the
 temperature distribution of the whole apparatus can be made uniform and
 the soaking characteristics of the substrates 1,2 can be further improved.
 Also, since the second heater 7b is an auxiliary heater that does not
 contact the substrates 1,2, the temperature of both heaters need not be
 controlled to be identical as was the case with conventional heaters, and
 the temperature shall be set to be close to that of the heater 7a. It
 should be noted that the reason for heating the substrates 1,2 in a
 soaking manner is that bows and shifts can be prevented since both of the
 substrates exhibit identical amounts of shrinkage at the time of cooling
 the substrates 1,2. After fixing of the substrates 1,2, rapid cooling is
 enabled by making, for instance, water flow through the cooling water
 piping 16, and the efficiency of product manufacturing can be improved. In
 this embodiment, the multi-layered arrangement makes it possible to
 decrease the interchange of heat between the first graphite plate 5a of
 high rigidity and second graphite plate 5b of high rigidity than compared
 to that of an uniform arrangement, whereby enabling simultaneous use of
 cooling water and heater, and exhibits a characteristic that the second
 graphite plate 5b of high rigidity can be rapidly heated by, for instance,
 terminating supply of cooling water while the heater 7a is being used.
 It should be noted that while the multi-layered structure in this
 embodiment is a two-layered structure, the present invention is not
 limited to a two-layered structure as long as heat from the heater is not
 directly transmitted to the substrates. Thus, in case the pressurizing
 plate which directly contacts the substrates is formed of a second
 graphite plate 5b of high rigidity of which thermal expansion coefficient
 is substantially identical to that of the substrates, it is not
 necessarily required that the first graphite plate 5a of high rigidity be
 a graphite plate, and the same effects can be obtained when it is formed
 of a metal material of which thermal expansion coefficient is different
 from that of the substrates, for instance, stainless steel, aluminum, or
 iron.
 Further, by providing a coating film of, for instance, glass on the surface
 of the graphite plate disposed on the side of the substrate, a portion at
 which it contacts the substrates 1,2 can be prevented from attrition also
 in repetitive manufacturing. With this arrangement, occurrence of
 deficiencies in products due to wear powder (contamination of foreign
 matters) can be prevented. Moreover, the coating film serves to decrease
 the abrasion coefficient with respect to substrates, and this action also
 provides the effect of preventing shifts.
 EMBODIMENT 3
 While there have been explained in Embodiments 1 and 2 arrangements for
 manufacturing while preventing wrap in the substrates 1,2 as much as
 possible, it will be explained in this embodiment an arrangement in which
 the substrates are controlled to assume a desired shape. First, a liquid
 crystal panel is generally preferred to assume a flat surface condition,
 and it is required to prevent a display portion of the liquid crystal
 panel from being disordered by external pressure or vibration. This
 requirement becomes increasingly important accompanying the thin-sizing of
 the liquid crystal panel. However, it has been known for a drawback in
 conventional art that the higher the accuracy required for the substrate
 becomes, the more the yield decreases. In this connection, it has been
 found that disorder of a display portion of a liquid crystal panel can be
 restricted by deliberately forming the substrate, for instance, in a
 slightly convex manner. FIG. 3 is an arrangement for an apparatus for
 realizing this, and 1 to 16 denote elements having identical or equivalent
 functions as those of Embodiment 2. 18 denotes a center pin which
 functions to push the multi-layered graphite plate of high rigidity up.
 The center pin 18 is, for instance, threaded with screw grooves, and its
 height can be adjusted. 19, 20 respectively denote a rotation stopping pin
 and a positioning pin, and 21 is a spring mechanism for pressing the
 peripheral portion of the graphite plate down (while FIG. 3 shows only one
 point, there are required at least two points and a curved surface is
 formed with more points, depending on the shape of the substrate). With
 these arrangements, the shape of the graphite plate 5, that is, the shapes
 of the substrates 1,2 can be controlled by pushing up with the center pin
 18 and pressing down with the spring mechanism 21. It should be noted that
 play is permitted to the positioning pin 20 since the graphite plate is
 required to be cambered.
 Further, by controlling the thickness of the heat insulator 15a, the shape
 of the graphite plate 5b, that is, the shapes of the substrates 1,2 can be
 controlled as well. Examples of suitably used materials for the heat
 insulator 15a are, for instance, silica glass or glass epoxy.
 In case the graphite plate of high rigidity has been made to be of
 multi-layered arrangement, there can be obtained an effect that when
 deforming the same to assume a curved surface, the graphite plate will not
 be destroyed by bending stress and that it can also be bent at small power
 since gliding between layers is enabled. Consequently, the bending
 mechanism can be simplified by making the graphite plate of high rigidity
 to be of multi-layered arrangement.
 It should be noted that while the substrate is made to be deformed in a
 convex manner in this embodiment, the present invention is not limited to
 this, and the substrate might alternatively deformed in a concave manner.
 Further, the present invention is not limited to be of a multi-layered
 structure, and the substrate might be deformed in a convex or concave
 manner in a single-layered structure.
 EMBODIMENT 4
 FIG. 4 is a sectional view showing still another embodiment of the present
 invention. In the arrangement of this embodiment, a second O ring 12a is
 interposed between the graphite plate 6 of low rigidity and the hook 10,
 and the suction hole 11 is made to be a hole for applying pressure,
 whereby the graphite plate 6 of low rigidity that is supported by the hook
 10 and the second O ring 12a forms a closed space together with the upper
 lid 9.
 Operations will now be explained. Air is injected from the suction hole 11
 into the closed space so that the pressure therein is made slightly higher
 than the atmospheric pressure. Then, the upper lid 9 is descended until
 the graphite plate 6 of low rigidity contacts the O ring 12. Thereafter,
 the pressure is further raised to make the graphite plate 6 of low
 rigidity stick to the substrate 1. At this time, a closed space is formed
 by the graphite plate 5a of high rigidity, the O ring 12, and the graphite
 plate 6 of low rigidity, while the vacuum piping 13 is set to be at least
 in a released condition for drawing air therefrom or is slightly vacuum
 drawn simultaneous with the formation of the closed space. It should be
 noted that in case no vacuum drawing is performed, the O ring 12 might
 also be omitted.
 It is an characteristic of the present invention that the graphite plate 6
 of low rigidity is not restrained. Thus, in case pressure is applied while
 the distance between the upper lid 9 and the graphite plate 5 of high
 rigidity is remote, the graphite plate 6 of low rigidity is excessively
 bent so that it is detached from the O ring 12a, thus, the above-mentioned
 operations are performed.
 By the above-mentioned operations, the substrates 1,2 can be uniformly
 applied with pressure similarly to the Embodiments 1 to 3 at substantially
 atmospheric pressure. The purpose for employing this arrangement is for
 enabling application of pressure to the substrates 1,2 at substantially
 atmospheric pressure. In conventional methods, it had been considered that
 no differences existed in characteristics of products in case differences
 in pressure occurred in the interior and exterior of the closed space,
 regardless whether the interior is set to vacuum or the exterior is set to
 be not less than atmospheric pressure. However, considerations indicated
 that the yield of products was improved by setting the substrates to
 atmospheric pressure. That is, in case the substrates 1,2 are disposed in
 a vacuum condition for heating, it could cause, though in small amounts,
 generation of voids in fixing adhesive, and this void would cause leakage
 of liquid crystal when liquid crystal was injected between the substrates
 1,2. While Japanese Unexamined Patent No. 188018/1982 disclosed a method
 in which the whole bendable material covering substrates was put into a
 pressurizing vessel for applying pressure thereto, the provision of
 holding down from a side of the substrates and exhausting gas in the
 interior of the substrates to the exterior in the present invention, it
 has been enabled to provide products of simple arrangements at high
 productivity and in a stable manner.
 EMBODIMENT 5
 In the preceding embodiments, the frame body 8 has been provided to enclose
 the substrates 1,2, and the frame body 8 has also been made of tungsten,
 molybdenum, alloys thereof, graphite or iron-nickel alloy. Accompanying
 the heating and cooling of the graphite plates 5,6, the frame body 8 is
 also heated and cooled, wherein the shear stress occurring between
 materials of the substrates 1,2 and the frame body 8 would be made minimum
 since the thermal expansion coefficients of the substrates 1,2 and the
 frame body 8 are substantially made to be identical. Consequently, the
 graphite plates are made to uniformly contact the substrates in flat
 conditions.
 In this embodiment, differences in level have been provided in frame body
 8a as shown in FIG. 5, and the differences in level are set such that the
 height of the inner surface located on the side of the substrates 1,2 is
 identical to or lower than the height of the substrates, and that the
 height of the outer surface on the opposing side thereof is higher than
 the height of the inner surface. With this arrangement, since force is
 acting on the graphite plate 6 of low rigidity so as to deform to the side
 of the substrate 1, the graphite plate 6 of low rigidity is slightly bent
 to the side of the substrate 1 when a clearance is formed between the
 substrate 1 and the frame body 8a, whereby the pressure in the peripheral
 portion of the substrate 1 can be increased to smash adhesive between the
 substrate 1 and substrate 2 in a stable manner. Consequently, shifts
 between substrates can be further decreased and uniformity in gaps between
 substrates can be secured.
 It should be noted that while the frame body is disposed like a picture
 frame, it is preferable to make it to be of divided type since torsion is
 apt to occur when it is of uniform type. Especially in case metal
 materials are employed, it is required to make it of divided type as a
 measure for coping with deformation for the same reasons as described
 above.
 As explained so far, the apparatus for manufacturing a liquid crystal panel
 according to the first aspect of the present invention is an apparatus for
 manufacturing a liquid crystal panel in which two substrates are faced to
 each other with spacers interposed therebetween, applied with heat and
 pressure in an overlapped condition, and adhesive arranged between the two
 substrates is cured for fixing, wherein at least one of a pair of
 pressurizing plates for applying pressure to the two substrates is a
 graphite plate and in that upper and lower pressurizing plates are made to
 be of different rigidity. With this arrangement, the graphite plate of low
 rigidity is made to stick to the substrate, and shifts between substrates
 can be prevented while securing uniformity in gaps between substrates.
 According to another embodiment of the present invention, at least one of
 the pressurizing plates is of a multi-layered arrangement, and a graphite
 plate is employed as a part of the multi-layered arrangement, and
 according to a further embodiment of the present invention, the
 pressurizing plate of multi-layered arrangement is provided with an inner
 space in at least one point positioned between the layers. With these
 arrangements, the soaking characteristics of the graphite plates can be
 improved, and shifts between substrates can be further restricted while
 further securing uniformity in gaps between substrates.
 According to a still further embodiment of the present invention, the
 pressurizing plate of multi-layered arrangement is provided with a path
 for cooling at a nearer side with respect to the substrate and with a
 heater at a farther side with respect to the substrate. With this
 arrangement, the soaking characteristics of the substrates can be
 improved, rapid cooling/heating is made possible, and improvements in
 quality and productivity can be obtained.
 According to a yet further embodiment of the present invention, a coating
 film is provided on a surface of the graphite plate. With this
 arrangement, a long-term duration of the graphite plate is enabled and
 improvements in yield and accuracy of the product can be obtained.
 According to another embodiment of the present invention, a graphite plate
 of high rigidity is fixed to a base by means of a pin or a heat insulator
 in order to deform a surface of the graphite plate in a convex or concave
 manner. With this arrangement, the shapes of the finally obtained
 substrates can be controlled.
 According to a further embodiment of the present invention, there is
 provided a mechanism in which a closed space is formed by means of a
 pressurizing plate of low rigidity and an upper lid, and a substrate
 disposed in an exterior space with respect to the closed space is applied
 with pressure by making a pressure of the closed space higher relative to
 the exterior space, whereby occurrence of bubbles in adhesive that is
 applied between the substrates can be prevented. Consequently, leakage of
 liquid crystal can be prevented and yield can be improved.
 According to a still further embodiment of the present invention, a frame
 body of a thickness approximately identical to that of the two substrates
 is arranged between the pair of pressurizing plates as to enclose the
 substrates, wherein the frame body is formed of tungsten, molybdenum,
 alloys thereof, graphite or iron-nickel alloy. With this arrangement, the
 graphite plates are made to uniformly contact the substrates in flat
 conditions and shifts between substrates can be restricted.
 According to a yet further embodiment of the present invention, differences
 in level are provided in the frame body, wherein the differences in level
 are set such that a height of an inner surface located on the side of the
 substrate is identical to or lower than the height of the substrate, and
 that a height of an outer surface on the opposing side is higher than the
 height of the inner surface, whereby the pressure in the peripheral
 portion of the substrates can be increased and adhesive can be smashed in
 a stable manner. With this arrangement, shifts between substrates can be
 further decreased and uniformity in gaps between substrates can be
 secured.
 The method for manufacturing a liquid crystal panel according to the second
 aspect of the present invention is a method for manufacturing a liquid
 crystal panel in which two substrates are faced to each other with spacers
 interposed therebetween, applied with heat and pressure in an overlapped
 condition, and adhesive arranged between the two substrates is cured for
 fixing, wherein at least one of a pair of pressurizing plates for applying
 pressure to the two substrates is a graphite plate and in that upper and
 lower pressurizing plates are made to be of different rigidity. With this
 arrangement, the graphite plate of low rigidity is made to stick to the
 substrate, and shifts between substrates can be prevented while securing
 uniformity in gaps between substrates.