Patent Publication Number: US-2006011507-A1

Title: Supporting bar for substrate cassette

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
      This application claims the benefit of priority under 35 USC § 119 from Japan Application No. 2004-156755, Publication No. ______ entitled SUPPORTING BAR FOR SUBSTRATE CASSETTE, filed May 26, 2004. The disclosure of which is incorporated by reference in its entirety herein for all purposes.  
     FIELD OF THE INVENTION  
      The present invention relates to a substrate storage cassette used in a manufacturing process of a glass substrate used for a liquid crystal display, for example. More particularly, the present invention relates to the central support component (support bar) allotted in each step of a cassette.  
     BACKGROUND OF THE INVENTION  
      The conventional liquid crystal display element has been manufactured by forming patterns, such as a picture element electrode, wiring, etc., on one side of the liquid crystal display element substrate, forming an orientation film by an application or adhesion processing on it, carrying out a rubbing processing of this orientation film so that the liquid crystal molecules are oriented regularly to the orientation surface, subsequently pasting two substrates for liquid crystal display elements through seal material so that the sides on which picture element electrode, wiring, etc., of the above-mentioned substrates for liquid crystal display elements face each other at a uniform interval, and then enclosing liquid crystal into the space formed between the substrates. In the manufacturing process of such a liquid crystal display element, multiple processing devices, such as a spatter processing device used for forming a picture element electrode, etc., a chemical vapor deposition device, a spin coater which applies orientation film, and a rubbing device which performs rubbing of the orientation film, etc., were used.  
      Therefore, after finishing processing of the substrate with one processing device, in order to move the substrate to another processing device for processing, the substrate needed to be stored temporarily, and a box type cassette was used for this storage.  
      A conventional storage cassette has: a front side which is open to insert and remove a substrate; a top side; a bottom side; left and right sides of the storage cassette; a back side; and substrate end support parts that project from the left and right sides of the storage cassette towards the inside of the storage cassette to support both right and left ends of the substrate or plate.  
      Since the storage cassette structure supports only both ends of a glass substrate, the central part of the substrate bends greatly when a large-sized glass substrate is used. And, when a substrate transfer fork, such as a robot performed transfer of a substrate, there were problems because the transfer fork could not smoothly carry the substrate because the transfer fork either contacted the bent portion of the central part of the glass substrate contained directly above the substrate inserted into the storage cassette, or the substrate was scratched. Moreover, since the storage amount to a cassette fell sharply when the interval of the substrates is expanded in order to avoid contact of glass substrates, there was a problem of causing decline in production efficiency.  
      The following disclosures may be relevant to various aspects of the present invention and may be briefly summarized as follows:  
      In order to reduce this warping of the glass substrate central part, the Japan Unexamined Patent Publication Heisei 9-36219 proposed to lessen the warping of the central part by increasing the length of the shelf pieces that jut out from both the right and left sides of the loading opening of the storage cassette over the length of conventional shelf pieces. However, when the shelf pieces jutting out are lengthened in this manner, in order to make a substrate transfer fork not contact the shelf pieces, the width of the fork must be reduced. In addition, although the Heisei 9-36219 application indicates the use of carbon fibers as conductive material, it is not used as a strengthening fiber.  
      On the other hand, in order to support the center of a substrate in addition to supporting both ends of the stored glass substrate, it is proposed to prepare a central support part (e.g., support bar) projecting from aforementioned back side of the storage cassette towards the front of the storage cassette. With this support bar, it has been supposed that the maximum warping at the substrate central part decreases and contact between the substrates of the steps (or the left and right shelf pieces) above and below can be prevented. See the following publications: Japan Unexamined Patent Publication 2000-7148; 2000-142876 and 2003-341784.  
      However, the trend of making lighter and larger the substrate for liquid crystal display elements has advanced further, and in terms of size, glass substrate of a size with which a length of one side amounts to 2000 mm, and the thickness is getting smaller from 0.7 mm to 0.5 mm. For this reason, with the conventional support bar using metals with low flexural rigidity, such as aluminum, the problem that it cannot suppress the warping at the glass substrate central part newly occurred.  
      In addition, as a result of elongating the support bar along with the trend of enlarging the glass substrate, the bending vibration generated at the time of loading and unloading the glass substrates from the cassette is less likely to decrease, and the manufacture line speed is reduced. Furthermore, since the material (mainly metal material, such as iron, stainless steel, aluminum, etc.) used for conventional support bars have a large density, it also caused the problem of a steep increase in weight of the storage cassette.  
      In view of the above problems, it is desirable for the present invention to offer a support bar, which can prevent contact between the horizontal glass substrates or plates inserted in the steps (or the left and right shelf pieces) above and below each substrate or plate in vertical succession. It is desirable that the substrates or plates of the present invention prevent contact, even at the time of storing a large-sized glass substrate, while it does not cause a steep increase in the whole storage cassette weight, and that it further increases the manufacture line speed by the excellent vibration dampening properties and improves production efficiency.  
     SUMMARY OF THE INVENTION  
      Briefly stated, and in accordance with one aspect of the present invention, there is provided a plate cassette support bar in a plate cassette, wherein said plate cassette accommodates a multiplicity of plates, each having a center, in a horizontal manner and in multiple levels in the vertical direction, said plate cassette support bar provides support to control warping at the center of each of the plates, said plates characterized by being formed of a carbon fiber reinforced composite material that contains 30% or more by volume ratio of high-elasticity carbon fiber with a tensile modulus of 490-950 GPa.  
      Pursuant to another aspect of the present invention, there is provided a plate cassette support bar disclosed above, characterized by said plate cassette support bar having a hollow shape.  
      Pursuant to another aspect of the present invention, there is provided a plate cassette support bar disclosed in the preceding paragraphs, said plate cassette support bar comprising a fixed end that attaches to the plate cassette and a free end opposite the fixed end, said free end having a tip, said plate cassette support bar characterized by a perimeter of the said plate cassette support bar in a direction perpendicular to a longitudinal direction of the plate cassette support bar being smaller from its fixed end toward the tip at its free end.  
      Pursuant to another aspect of the present invention, there is provided a plate cassette support bar disclosed the preceding paragraph, characterized by the perimeter at the tip being ⅓- 9/10 the perimeter at the fixed end of the plate cassette support bar.  
      Pursuant to another aspect of the present invention, there is provided a plate cassette support bar disclosed in the preceding paragraphs, characterized by the plate cassette support bar having a hollow square pipe shape with a taper, wherein the width of said plate cassette support bar narrows as the tip is approached.  
      Pursuant to another aspect of the present invention, there is provided a plate cassette support bar disclosed in the preceding paragraphs, characterized by comprising a heat-cured laminated structure containing a pre-preg sheet in which carbon fibers comprising high-elasticity carbon fibers of tensile modulus 490-950 GPa are unidirectionally oriented at 0±5° to a longitudinal direction of the plate cassette support bar.  
      Pursuant to another aspect of the present invention, there is provided a plate cassette support bar disclosed in the preceding paragraphs, characterized by comprising a heat-cured laminated structure wherein a pre-preg sheet having a high-elasticity carbon fibers of tensile modulus 490-950 GPa are unidirectionally oriented at 0±5° to the longitudinal direction of the support bar, is laminated on the outer layer of a pre-preg sheet in which high-elasticity carbon fibers of tensile modulus of less than 490 GPa are unidirectionally oriented at 90±5° to the longitudinal direction of the support bar, and a cross pre-preg sheet containing reinforcing fibers is wrapped around the outermost layer.  
      Pursuant to another aspect of the present invention, there is provided a plate cassette comprising edge support members that support the edges of the plates, each plate having a center, said edge support members being positioned on both a right side and a left side of a plate feed opening, and support bars that are attached at a side opposite the plate feed opening, the support bars having free ends opposite thereto, disposed in a line or in a multiplicity of lines in a vertical direction with the free ends at the plate feed opening, and that support said plates to control warping at the center of each of said plates, and which accommodates a multiplicity of plates in a horizontal manner in multiple levels in a vertical direction, wherein which plate cassette is characterized by the support bars being the support bar disclosed. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The invention will be more fully understood from the following detailed description, taken in connection with the accompanying drawings, in which:  
       FIG. 1  is an outline perspective diagram showing an example of the substrate cassette using the support bar of the present invention.  
       FIG. 2  is a perspective view showing the attachment of the support bar to the support component.  
       FIGS. 3A-3I  show perspective views of examples of the form of the support bar of the present invention.  
       FIG. 4  shows a perspective view of an example of a hollow structure (e.g., a hollow circular pipe).  
       FIGS. 5A-5C  show views of an example of a hollow support bar of the present invention.  FIG. 5A  is a perspective view,  FIG. 5B  is a plan view and  FIG. 5C  is a side view.  
       FIGS. 6A-6C  show views of an example of a hollow support bar of the present invention.  FIG. 6A  is a perspective view,  FIG. 6B  is a plan view and  FIG. 6C  is a side view.  
       FIG. 7  is a graphical depiction showing the free oscillating attenuation waveform in the evaluation of the vibration dampening properties. The graph shows amplitude vs. time.  
       FIG. 8  is a graphical depiction showing the vibration dampening properties of the hollow support bar of this invention shown in Execution Example 1. The graph shows bending distortion vs. lapsed time.  
       FIG. 9  is a graphical depiction showing the vibration dampening properties of the hollow support bar of this invention shown in Comparison Example 1. The graph shows bending distortion vs. lapsed time.  
       FIG. 10  is a graphical depiction showing the vibration dampening properties of a solid support bar shown in Comparison Example 2. The graph shows bending distortion vs. lapsed time.  
       FIG. 11  is a graphical depiction showing the logarithmic dampening of the support bars of Execution Example 1 and Comparison Examples 1 and 2. The graph shows logarithmic dampening vs. bending distortion. 
    
    
      While the present invention will be described in connection with a preferred embodiment thereof, it will be understood that it is not intended to limit the invention to that embodiment. On the contrary, it is intended to cover all alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims.  
     DETAILED DESCRIPTION OF THE INVENTION  
      In the present invention, by constituting the support bar from carbon fiber reinforced composite material, which is lightweight and has high rigidity, there is only a small increase in weight even for a large substrate cassette. The support bar of the present invention is composed of carbon fiber reinforced composite material, which is lightweight and an excellent vibration dampening properties as well as high flexural rigidity.  
      By making a support bar into a hollow pipe structure, deflection or warping of the support bar from its own weight is suppressed and it is an excellent way to make the support bar lightweight. In addition, by decreasing the perimeter of the support bar from the immobilized end to the tip, a support bar being better or more improved in vibration dampening properties can be obtained, and since the vibration of the carried-in or inserted substrate is decreased in a short time, the substrate loading speed improves and working efficiency improves remarkably.  
      Reference is now made to the drawings for a detailed description of the present invention.  
       FIG. 1  shows an outline perspective diagram serving as an example of a glass substrate cassette  1  which has the support bar of this invention, and carrying in and taking out of the substrate  4 , such as a glass substrate, are performed from the direction of Arrow A of this figure.  
      The shelf pieces  2  used as the end support parts to support the ends of the substrates to be stored are prepared on both the right and left sides of the substrate loading opening, the support bars  3  which have the immobilized end fixed to the opposite side of the substrate loading opening. The component  5  is prepared in one line in the vertical direction as shown in the figure, and suppresses the deflection or warping at the central part of the substrates or plates and maintains the substrates leveled in the storage cassette.  
      Although this figure shows a glass substrate cassette in which the support bars  3  of one line in the vertical direction are prepared almost at the center of the opposite side of the substrate loading opening, it is not limited to this, and it can be in multiple lines as long as the warping of the central part of the substrate is suppressed.  
      Although the support bars  3  are fixed in one line in the vertical direction at a predetermined pitch to the support component  5 , the immobilization method is not specified. However, many known methods of immobilizing the support bars can be applied. For example,  FIG. 2  shows a well known method in which multiple slots  51  into which the support bars  3  can be inserted are prepared at a predetermined pitch on a side of the support component  5 , the support bars  3  are inserted therein and are further immobilized by a means, such as bolt bundle.  
      In the present invention, the support bar  3  is constituted from carbon fiber reinforced composite material (CFRP) using carbon fibers having a specific tensile modulus in order to make the support bar have excellent properties such as being lightweight in nature, having flexural rigidity, heat resistance, etc. In the present invention, 30% or more of the highly elastic carbon fibers have a tensile modulus of 490-950 GPa used by the volume ratio as carbon fibers. Sufficient rigidity is not acquired when the volume ratio is less than 30%, and the component having high vibration dampening properties is not obtained. It is preferable that the volume ratio of carbon fibers used in the present invention is 40% or more.  
      Additionally, it is good to use all strengthening fibers made of highly elastic carbon fibers, or some may be constituted from other strengthening fibers, such as carbon fibers having a tensile modulus of less than 490 GPa, glass fibers, aramid fibers, silicon carbide, fibers, and other well-known strengthening fibers. A preferable result is brought in many cases when, for example, the highly elastic carbon fibers are limited to 90% by the volume ratio and used in combination with other strengthening fibers, especially the carbon fibers having a tensile modulus of less than 490 GPa, in the remainder.  
      It is not necessary for such support bars  3  to have the shape of a square pillar as shown in  FIG. 1 , and it may have various pillar-shaped structures, for example, as shown in  FIG. 3 , the cross-section form of the pillar-shaped structure may be a triangle ( FIG. 3 ( a )), a trapezoid ( FIG. 3  ( b )), a polygon ( FIG. 3 ( c )), a circle ( FIG. 3 ( d )), a semicircle ( FIG. 3  ( e )), the shape of a letter C ( FIG. 3  ( f )), the shape of an upside down letter U ( FIG. 3 ( g )), the shape of a letter T ( FIG. 3  ( h )), the shape of a letter I ( FIG. 3  ( i )), etc. In addition, although the support bar  3  may have a pure structure of the carbon fiber reinforced composite material or a solid structure, such as a skin core structure which uses other material as the core layer and the carbon fiber reinforced composite material concerning this invention as the skin layer, etc., it is desirable to have a hollow structure emasculated in the center in the above-mentioned cross-section for a lightweight support bar  3 .  
      For example, square pillar pipes, etc. shown in  FIGS. 5 and 6  are made into hollow circular pipes as the circular hollow structure as shown in  FIG. 3  ( d ) and  FIG. 4 . The length of the support bars is determined suitably according to the size of the substrates to be stored, since it is sufficient if they can support the substrates so that the warping of the central part of the substrates to be stored is suppressed, and in this invention, the longer the length of the support bars is, the more remarkable its effect becomes (i.e., the less likely the warping of the central part).  
      The present invention is particularly useful when the length of the support bars is 500 mm or more. The width of the support bars is not specified. It is sufficient to secure the minimum width of the support bar as long as it is sufficient to provide the strength and the flexural rigidity required in order to suppress the warping of the central part of the substrates to be stored are maintained according to how to combine the materials to be used. Additionally, the height can be suitably set so that the minimum strength and flexural rigidity can be secured in relation to the width in the range of the storage pitch of the substrates.  
      In addition, in order to acquire a high vibration dampening properties, it is desirable to have the structure where the perimeter of the direction that intersects perpendicularly with its longitudinal direction becomes smaller as the tip part that is a free end as opposed to the immobilized end of the support bar. Especially, the combination with hollow structure is a desirable mode.  
      When reducing the perimeter towards the tip part of the support bar in this way, it is desirable for the perimeter of the tip part is ⅓ or more, more preferably ½ or more, of the perimeter of the side of the immobilized end. Although effect will be taken on the vibration dampening properties if the perimeter is made smaller, even a little as compared with that of having the same perimeter, it is desirable to make it 9/10 or less, more preferably ⅗ or less.  
      Here, “the longitudinal direction” is the direction of a line that connects the cross-sectional center of gravity (G 1 ) by the immobilized side end of a hollow shape (the support component  5  side) and the cross-sectional center of gravity (G 2 ) of the tip part as shown in  FIG. 5 . In order to make the perimeter smaller towards the tip part, for example, in the case of an angle pipe form, when the width and height of the immobilized end side are expressed as H 1  and T 1  and the width and height of the tip part as H 2  and T 2 , respectively, a taper form in which only the width narrows towards the tip (H 1 &gt;H 2 , T 1 =T 2 ) shown in  FIG. 5 ((A) a perspective diagram, (B) a top view, (C) a side view), a taper form in which only the thickness narrows towards the tip (H 1 =H 2 , T 1 &gt;T 2 ), shown in  FIG. 6  ((A) a perspective diagram, (B) top view, (C) a side view), a taper form in which both the width and height narrow towards the tip (H 1 &gt;H 2 , T 1 &gt;T 2 ), etc. are mentioned.  
      In addition, as for the mode of making the perimeter smaller towards the tip direction, it is not limited to the mode of decreasing it evenly from the immobilized end side to the tip part shown in  FIGS. 5 and 6 , but various modes. For example, the mode by which the perimeter is not changed at the portion around the immobilized end and it is made gradually smaller from that point on to the free end, or that by which the perimeter is made to decrease up to the midpoint of the longitudinal direction and the rest is made constant from that point on, etc. are other such modes.  
      In addition, the tip part may be in an open state as shown in  FIGS. 5 and 6 , or the tip part may be in a closed state by bending the prepreg sheet at the time of manufacturing the hollow component mentioned herein. Or, a cap made of an elastic component, such as rubber, etc., may be inserted to the tip part of an open state.  
      The manufacturing method of the support bar of this invention is explained hereafter and especially the manufacturing method of the support bar of a hollow structure having a tapered shape as shown in  FIGS. 5 and 6 , but it can be easily understood by the industry concerned that the method explained below may be changed suitably to manufacture a support bar of other forms.  
      For example, a removable core and an original-form prepreg sheet are first prepared in the preparation process. The removable core is formed into a tapered shape to correspond to the shape or form of the interior of the support bar. The material of the removable core has a certain amount of rigidity in order to function as the interior support mandrel at the time of laminating the prepreg sheet, has the characteristic that the removable core does not change its shape by the temperature lower than the heating temperature in the heating process in order to function as the interior mold mandrel at the time of forming the support bar, and can be easily taken out from the CFRP component after molding. From this viewpoint, as the material of the removable core, for example, metals, such as aluminum, iron, stainless steel, etc., MC nylon resin, polyimide resin, etc. are suitable. Since the thermal expansion rate of the above-mentioned removable core materials (e.g., metal, resin, etc.) is larger than CFRP, the removable core contracts by cooling after heating, and the removable core is easy to take out from the interior of the molded CFRP component.  
      In addition, mold release material may be applied to the surface of the removable core if needed. As the mold release material, it may be applied by any method, such as application of a chemical (for example, a surface-active agent etc.) by spraying, use of a mold release sheet, such as a Teflon® sheet, etc.  
      In addition, the thermal non-deforming properties of the removable core at the above-mentioned predetermined temperature means that it has the properties with which it hardly changes its shape at the heating temperature in the below-mentioned heating process. By hardly changing its shape at the above-mentioned heating temperature, it means that the material of the core material does not melt or that curve, warping, twist, wrinkle, fold, etc. are not caused to the component of the core material under the heating conditions mentioned herein. In addition, the above-mentioned predetermined temperature means the temperature of about 100-190 degrees C. or more, corresponding to the molding temperature of the matrix resin of the original-form prepreg sheet mentioned later.  
      For example, the removable core for creating the support bar of  FIG. 5  is a mandrel of which the cross-section has the shape of an oblong rectangle-like square and which is processed into a taper shape with which the width narrows towards the tip. In addition, for the removable core for producing the support bar component of  FIG. 5 , the height becomes smaller towards the tip.  
      The original-form prepreg sheet comprises the matrix resin impregnated into a sheet made of carbon fibers, and is an un-hardened sheet. For example, it is desirable to use the highly elastic carbon fiber prepreg sheet having a tensile modulus of 490-950 GPa as the base for the multiple prepreg sheets to be laminated, and to use carbon fiber prepreg sheet having a tensile modulus of less than 490 GPa for the remainder.  
      In addition, the prepreg sheet containing the above-mentioned glass fiber or other fibers may be added in some part within the limitation, which does not spoil the support performance as support bar component. As the matrix resin, thermosetting resin, such as epoxy resin, phenol resin, cyanate resin, unsaturated polyester resin, polyimide resin, bismaleimide resin, etc., are used. In this case, any material, which can bear a high temperature/high moisture environment, such as vulcanized rubber, is preferred.  
      In addition, for the above-mentioned thermosetting resin, fine particles consisting of rubber or resin may be added to the thermosetting resin for the purpose of giving shock resistance and toughness, or a thermoplastic resin is dissolved in the thermosetting resin may be used.  
      As the sorts of carbon fibers, although there are those of the PAN (i.e., polyacryloniprile) system of less than 490 GPa and those of the pitch system of 490-950 GPa, by this invention, both of these are used in combination. In this case, those of the pitch system have the feature that the elasticity is high and those of the PAN system have the feature that tensile strength is high.  
      In addition, as the original-form prepreg sheet, there are unidirectional sheets in which the strengthening fibers are oriented all in the same direction and cross sheets, such as plain woven fabric, twill fabric, satin fabric, 3-axis fabric, etc. As for the highly elastic carbon fiber prepreg sheet of 490-950 GPa, it is preferable to use a unidirectional sheet. As for the original-form prepreg sheet, it is preferable to prepare the sheet in various types by making the sort of the strengthening fibers differ, making the use ratio of the strengthening fibers to matrix resin differ, or making the orientation state of the strengthening fibers differ, and to select multiple original-form prepreg sheets to be used so that the CFRP component with the optimal flexural rigidity is formed according to the glass substrate to hold.  
      In addition, the pieces of prepreg sheet of a predetermined size are similarly formed about all the original-form prepreg sheets selected above. Next, laminating pasting of the pieces of prepreg sheet is carried out in each side of the core material (laminating process).  
      The pieces of prepreg sheet are non-hardened, and since it has a certain amount of adhesive power, pasting is carried out only by piling up the sheets one by one on the removable core to which mold release processing is performed. In this case, adhesion lamination is carried out by making it adhere to the lower layer film or sheet while applying heat with an iron etc until it becomes the desired thickness (for example, about 1-7 mm). The desired thickness at this time is preferably slightly thicker than the required thickness of the robot hand that loads and unloads the substrates into the substrate cassette with the amount of the volume reduction at the time of a prepreg sheet carrying out heating hardening foreseen. In the lamination of prepreg sheets, unidirectional sheets in which the carbon fibers are oriented with a ˜right angle (90±5°) to the longitudinal direction (henceforth “90° orientation”) are laminated in multiple levels at the innermost part (that is, the lowest layer), and unidirectional sheets oriented in ˜parallel (0±5°) to the longitudinal direction (henceforth “0° orientation”) are laminated in multiple levels on top of it.  
      In this case, in addition to the above-mentioned sheets, unidirectional sheets oriented in the slanted direction (45±15° or 135±15°) (henceforth “45° or 135° orientation”) or cross prepreg sheets oriented in two directions of 45° and 135°, etc., may be laminated in combination.  
      In this case, 0° orientation sheets have the warping prevention properties and vibration dampening properties of the longitudinal direction. 90° orientation sheets have the effect of controlling collapse of the hollow structure. Furthermore, by combining 45° orientation sheets and 135° orientation sheets, twist rigidity and twist vibration dampening properties are additionally improved. As for the cross sheets, it has the effect based on the above-mentioned combination of unidirectional sheets.  
      In addition, as a laminating order, it is preferable for the ease of taking out the removable core to have 90° orientation sheet in the lowest layer (the innermost side).  
      That is, because the pipe-like CFRP support bar does not contract much when thermal hardening is carried out, the strengthening fibers parallel to the perimeter of the removable core by constituting the inner side of the pipe-like CFRP support bar with 90° orientation sheets. This is because the contraction rate in the non-fiber orientation direction is lower than the contraction rate in the fiber arrangement direction with regard to the contraction rate as a sheet due to the carbon fibers having a lower thermal contraction rate than the matrix resin.  
      In addition, since the sheets that are laminated in the upper layers (that is, the outer sheets) have a higher contribution rate to the quality of the support bar (that is, flexural rigidity, etc.), it is desirable to laminate the 0° orientation sheets in the layer upper than the 90° orientation sheets from a viewpoint of warping prevention properties. The combination and the laminating order of the prepreg sheets to be used are determined taking this point into consideration.  
      In the present invention, it is preferable to use the highly elastic carbon fiber prepreg sheets of 490-950 GPa, particularly for the 0° orientation sheets.  
      By carrying out laminating pasting of the prepreg sheets to all the sides of the core material in this way, the laminated component in the state where the laminated object of the prepreg sheets was formed on the perimeter surface of the removable core is formed.  
      Then, the perimeter of this laminated component is covered by winding one roll or a few rolls of the cross prepreg sheet (covering process). In addition, the cross prepreg sheet is an non-hardened sheet in which the above-mentioned matrix resin was made to impregnate into the strengthening fibers woven in multiple directions, and as the strengthening fibers, fabric-like carbon fibers, glass fibers, aramid fibers, silicon carbide fibers, etc. are desirable. In addition, a sheet having high flexibility and adhesiveness is desirable so that it adheres tightly to the laminated component and covers it.  
      After this covering process, exterior mold forms are pushed onto it from all four directions, the non-hardened component of this state is out into a vacuum packed, and by heating, and the support bar component of this invention is formed.  
      The heating conditions in this case is that it is heated by the rate of 2-10° C./min from room temperature, it is maintained for about 10-180 minutes at about 100-190° C., heating is stopped after that, and it is cooled by natural cooling and it is returned to normal temperature.  
      Since any prepreg sheet contains thermosetting resin, it hardens into a state where they are pasted to each other at the surface or the edge of each sheet. In addition, putting the non-hardened component into a vacuum packing serves the purpose of sucking out the air bubbles between the sheets etc. produced at the laminating process, and the purpose of applying the external pressure (that is, atmospheric pressure) mostly equally to the non-hardened component.  
      In addition, the external pressure of the specific direction may be applied to the non-hardened component. For example, by putting pressure from the top by a weight etc. in a way that a gap is not produced between the exterior mold form and the thickness setting board, the flatness of the top side of the CFRP support bar  3  (that is, the substrate support side) improves and the size (especially thickness) accuracy of the CFRP support bar  3  becomes high, and by putting pressure in the direction which the connection interfaces are pushed against each other by a vise etc., the connection at the edge of the prepreg sheets improves.  
      Then, the core material is taken out (removing process). The CFRP support bar  3  of hollow structure is formed by this. According to this embodiment of the present invention, since the CFRP support bars  3  are constituted not as a solid object but as a hollow structured object, lightweight support bars can be attained.  
      Therefore, generation of warping or vibration at the tip of the support bar due to the self weight or the load of the substrates to be loaded can be prevented, and the support accuracy of the substrates and the loading/unloading nature can be increased.  
      According to this embodiment of the present invention, since the removable core bears two functions as the interior support mandrel at the time of laminating the prepreg sheets and as the interior mold mandrel at the time of carrying out heating forming the support bar  3 , the formation of the CFRP board (i.e., laminating of the prepreg sheets) and the formation of the CFRP support bar (i.e., mutual connection between the prepreg sheets and the adjacent wall parts) can be performed simultaneously.  
      In addition, since the perimeter surface was covered with the cross prepreg sheets, when post-processing operations such as cutting, opening slot, etc., is performed, fuzz and fraying produced at the processing part can be prevented in the present invention.  
      By this, while processability improves, there is no fear of damaging precision substrates, such as a substrate for liquid crystal displays, a substrate for plasma displays, a silicon wafer, etc., and it also has the advantage that there is little generation of dust, etc.  
      Additionally, there are other advantages that a level difference, etc., produced at the connection part of the prepreg sheet edge are covered to improve the appearance and that the connection parts of the prepreg sheets are reinforced, by covering by the cross prepreg sheet.  
      In addition, although the above-mentioned explanation explained the method of manufacturing the support bar by combining pieces of multiple prepreg sheets as the manufacturing method, the present invention is not so limited. For example, the method of winding a long prepreg sheet around the perimeter surface of the core material and laminating, etc., is also possible.  
      When manufacturing the pipe type support bar, which has a circular, hollow cross-section shown in  FIG. 4 , the following procedures are performed.  
      The shape of the circular cross-section, which has a taper, is used as the shape of the removable core of the support bar. That is, the diameter is made larger on the side that corresponds to the immobilized end of the CFRP support bar, and the diameter is made smaller on the side that corresponds to the free end.  
      As for the length of the mandrel, it is desirable to make it a little longer than the length of the support bar. Metal, such as aluminum, iron, and stainless steel, can be used as the material of the mandrel. As the prepreg sheets, 0° orientation sheets and 90° orientation sheets are used. 45° orientation sheets and 135° orientation sheets can also be added.  
      The prepreg sheets are cut out in advance as follows:  
      The prepreg sheets to be wound around the circular mandrel usually have a trapezoid form. When the number of lamination of the prepreg sheet to the removable core at the free end and at the immobilized end are made the same, the upper bottom and the lower bottom of the trapezoid have the length computed by (the circumference of the free end)×(the number of times of laminating) and (the circumference of the immobilized end)×(the number of times of laminating).  
      Additionally, the height of the trapezoid is about the same as the length of the CFRP support bar. When the number of times of laminating the prepreg sheet to the removable core differs between the free end and the immobilized end, by the same calculation method as the case where the above-mentioned numbers of times of laminating are the same number, the lengths of the upper bottom and the lower bottom of the trapezoid can be computed, and the prepreg sheet can be cut out.  
      In the case of the 0° orientation sheet, the direction of the height of the trapezoid form becomes almost parallel to the orientation direction of the strengthening fibers.  
      On the other hand, with the 90° orientation sheet, the upper bottom or the lower bottom of the trapezoid becomes almost parallel to the orientation direction of the strengthening fibers.  
      It is preferable in an embodiment of the present invention to have the 90° orientation sheet as the innermost layer, and to position the 0° orientation sheet on the outside about the laminating order of the prepreg. This is for considering that the mandrel can be easily taken out after formation by surrounding the innermost side of the hollow circular pipe, i.e., the outside of the mandrel, by the 90° orientation sheet having a small thermal contraction rate so that the hollow circular pipe does not contract in the direction of the circumference at the time of thermal hardening.  
      After winding the predetermined prepreg on the removable core, tapes that contracts by heating, such as a polypropylene tape and a tape made of PET, are wound from the outside to fix prepreg, and overheating hardening is carried out in oven.  
      The heating conditions is that it is heated by the rate of 2-10 degrees C./min from room temperature, it is maintained for about 10-180 minutes at about 100-190 degrees C., heating is stopped after that, and it is cooled by natural cooling and it is returned to normal temperature, and by taking out the removable core after this, a hollow circular pipe type CFRP support bar is obtained.  
      Although the above explanation explained the example about the CFRP support bar  3  using the carbon fiber reinforced composite material, which contains highly elastic carbon fibers, about other components, which constitute a substrate cassette, conventionally well-known things can be used.  
      Furthermore, it is also possible to attain a lightweight and rigid substrate cassette, simultaneously, by constituting the shelf pieces  2  of the end support parts or the frame on the bottom side and the frame on the ceiling side, and the frame on the back side which serves as the opposite side of the substrate loading opening, etc., similarly from the carbon fiber reinforced composite material.  
      Although each shelf piece  2  of these end support parts is made into the shape of a broad board in  FIG. 1 , it is also possible, for example, to allot multiple shelf pieces  2  having a width about the same as the support bar  3  to both the right and left sides of the substrate loading opening at predetermined intervals, or to regard two lines or three lines as one unit and to allot each unit at predetermined intervals as shown in  FIG. 1 .  
     EXECUTION EXAMPLES  
      Hereafter, although this invention is concretely explained with reference to the execution examples, this invention is not limited only to these execution examples.  
     Execution Example 1  
      After preparing a trapezoidal aluminum removable core with a height of 6.9 mm, a width of 54.9 mm in a fixed end, and its width of 24.9 mm in a tip part as a removable core, the prepreg sheet B in which pitch system carbon fibers with its tensile elasticity of 240 GPa was oriented at 90 degrees in the longitudinal direction of the removable core, the prepreg sheet A in which pitch system carbon fibers with its tensile elasticity of 800 GPa was oriented at 0 degrees in the longitudinal direction of the removable core, and a cross prepreg sheet C which was oriented at 0 degrees and 90 degrees for the outer layer were laminated to the removable core in this order in the numbers listed in the Table 1 and were hardened by heat. After it was hardened, the removable core was taken out, and then a support bar in the shape of a hollow trapezoid with a taper with its width of 60 mm in a fixed end, its width of 30 mm in a tip part, its height of 12 mm, its wall thickness of 2.55 mm, and its length of 1000 mm was obtained.  
                               TABLE 1                                   Laminated   Total               Direction of   number of   thick-           Thickness   laminating   sheets   ness       Prepreg type   (mm/sheet)   (degree)   (sheet)   (mm)                                                    Cross prepreg sheet C   0.25   0/90   1   0.25       Prepreg sheet A   0.22   0   5   1.1       Prepreg sheet B   0.20   90   6   1.2       The core material   6.9   —   —   6.9       Prepreg sheet B   0.20   90   6   1.2       Prepreg sheet A   0.22   0   5   1.1       Cross prepreg sheet C   0.25   0/90   1   0.25       Total           24   12.0                  
 
     Comparison Example 1  
      After preparing an aluminum removable core with its thickness of 7.1 mm and its width of 55.1 mm as a the core material, the prepreg sheet B in which pitch system carbon fibers with its tensile elasticity of 240 GPa was oriented at 90 degree in the longitudinal direction of the removable core. The prepreg sheet B′ in which pitch system carbon fibers with its tensile elasticity of 240 GPa was oriented at 0 degree in the longitudinal direction of the removable core, and a cross prepreg sheet C which was oriented at 0 degree and 90 degree for the outer layer were laminated to the removable core in this order in the numbers listed in the Table 2 and were hardened by heat, and the removable core was taken out, a hollow CFRP support bar in the shape of a hollow trapezoid with its width of 60 mm in a fixed end, its width of 60 mm in a tip part, its height of 12 mm, its thickness of 2.45 mm, and its length of 1000 mm was obtained.  
                               TABLE 2                                   Laminated   Total               Direction of   number of   thick-           Thickness   laminating   sheets   ness       Prepreg type   (mm/sheet)   (degree)   (sheet)   (mm)                                                    Cross prepreg sheet C   0.25   0/90   1   0.25       Prepreg sheet B′   0.20   0   9   1.8       Prepreg sheet B   0.20   90   2   0.4       The core material   7.1   —   —   7.1       Prepreg sheet B   0.20   90   2   0.4       Prepreg sheet B′   0.20   0   9   1.8       Cross prepreg sheet C   0.25   0/90   1   0.25       Total           24   12.0                  
 
     Comparison Example 2  
      After laminating the prepreg sheet B′ and the cross prepreg sheet C to the above-mentioned laminated product of the prepreg sheet B without using a the removable core and hardening it with heat, a solid CFRP support bar with its width of 60 mm, its height of 12 mm, and its length of 1000 mm was obtained. The lamination of each prepreg sheet was as in the following table 3.  
                               TABLE 3                                   Laminated   Total               Direction of   number of   thick-           Thickness   laminating   sheets   ness       Prepreg type   (mm/sheet)   (degree)   (sheet)   (mm)                                                    Cross prepreg sheet C   0.25   0/90   1   0.25       Prepreg sheet B   0.20   0   22   4.4       Prepreg sheet B   0.20   90   13   2.6       Prepreg sheet B   0.20   0   22   4.4       Cross prepreg sheet C   0.25   0/90   1   0.25       Total           59   12.0                  
 
      The measurement and the evaluation on the decrease table characteristic of oscillating of the support bars obtained in the execution Example 1 and the comparison Example 1 and 2 were performed according to the following method:  
      The support bar was pinched at a point, which was 150 mm from one end with a jig for fixation, and was maintained horizontally in the state of cantilever.  
      Strain gages were prepared at the 50 mm point in the longitudinal direction from the fixed part, or, at the top and bottom sides of the fixed part, which were about 200 mm from the end of support bar.  
      After the initial flexure was given to the support bar by hanging a weight with its mass of 5 kg at the end of the free vibration side of the bar, and the support bar was vibrated by cutting the wires that was used to hang, the bending vibration dampening properties of the support bar was measured by measuring the bend and the strain in the decrease table of free oscillating.  
      The bend and the strain were measured for 10 seconds, and while calculating the frequency of vibration of the normal mode of the support bar from the obtained free oscillating attenuation waveform ( FIG. 7 ), the logarithmic dampening (Δ) was also calculated by the following formula (1).  
      In  FIG. 7  and the following formula (1), T represents the time one cycle took, Xn represents initial oscillating amplitude intensity, Xn represents the oscillating amplitude intensity of the time nT, and n represents the number of amplitude.  
             Formula   ⁢           ⁢   1                           Δ   =       1   n     ⁢   ln   ⁢       x   0       x   n                 (   1   )             
 
      The results are shown in the following Table 4 and the drawings, respectively.  
                               TABLE 4                                   Execution   Comparison   Comparison           Example 1   Example 1   Example 2                                                    Mass (kg)   0.48   0.6   1.6       Peculiar pitch (Hz)   38.2   18.6   16.4       Bending vibration                   dampening property       Logarithmic   Line a   Line b   Line c       dampening:  FIG. 11                    
 
      According to the above-mentioned results, the support bar produced by the method of this invention has high frequency of vibration of the normal mode and is excellent in its vibration dampening properties.  
      Consequently, since the vibration of the support can be canceled in a very short time, it is possible to improve the working efficiency.  
      In addition, it is possible to further lower the self weight by making it into a taper form, and especially when it is necessary to orientate many support bars in many steps, it becomes clear that the effect for making the substrate cassette lighter is more compared to that when making the structure in which the inside is hollow.  
      It is, therefore, apparent that there has been provided in accordance with the present invention, a support bar that fully satisfies the aims and advantages hereinbefore set forth. While this invention has been described in conjunction with a specific embodiment thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims.