Patent Publication Number: US-2013247621-A1

Title: Apparatus for forming lubricant layer on surface of glass and annealing furnace and glass manufacturing apparatus including the same

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation of International Application No. PCT/KR2012/001274 filed on Feb. 20, 2012, which claims priority to Korean Patent Application No. 10-2011-0015039 filed on Feb. 21, 2011, Korean Patent Application No. 10-2011-0039031 filed on Apr. 26, 2011, and Korean Patent Application No. 10-2012-0017150 filed on Feb. 20, 2012, in the Republic of Korea, the entire contents of which are incorporated herein by reference. 
     BACKGROUND OF THE DISCLOSURE 
     1. Field of the Disclosure 
     The present disclosure relates to a glass manufacturing technique, and more particularly, to an apparatus for forming a lubricant layer on the surface of a glass and an annealing furnace and a glass manufacturing apparatus including the same, which may prevent scratches from occurring at the surface of a glass and decrease corrosion of glass manufacturing equipment. 
     2. Description of the Related Art 
     Many kinds of flat glasses are being used in various fields like window panes, window screens of vehicles and mirrors. Such a flat glass may be manufactured in various ways. Among them, a representative method is a production method using a float process. For example, thin glass planes or glass films for TFT displays are frequently manufactured by the float process. The glass manufactured by the float process is called a float glass. 
       FIG. 1  is a schematic diagram showing a system for manufacturing a float glass. 
     As shown in  FIG. 1 , a glass is generally formed from a molten glass by using a float bath  10  where a molten metal M such as molten tin or molten tin alloy is stored and flows. At this time, a molten glass having a lower viscosity than the molten metal M and lighter than the molten metal M by about ⅔ is successively supplied into the float bath  10  through an inlet of the float bath  10 . The molten glass moves to the downstream of the float bath  10  while floating and spreading on the molten metal M. In this process, the molten glass nearly reaches an equivalent thickness according to its surface tension and gravity to form a glass strip or ribbon which is solidified to some extent. 
     In addition, the molten glass ribbon formed as above is transferred from the float bath  10  to an annealing furnace  20  and experiences an annealing process. In the annealing process, the glass is transferred from an inlet to an outlet of the annealing furnace  20  by transfer means such as a roller  30  or a belt. In addition, after the annealing process, the glass may also be carried by the transfer means such as the roller  30 . 
     While the glass is transferred in the annealing process or after the annealing process, the lower surface of the glass may come into contact with the transfer means such as the roller  30 . At this time, due to the transfer means such as the roller  30 , flows, cracks or scratches may occur at the lower surface of the glass. Particularly, if the above equipment is used continuously, impurities or glass fractures may be attached to the transfer means such as the roller  30 . In this case, scratches may occur more easily at the lower surface of the glass. 
     If scratches occur at the lower surface of the glass during a glass transferring process using the roller  30  or the lime, the quality and yield of glass greatly deteriorate. Therefore, efforts are being made to prevent scratches from occurring at the lower surface of a glass during the glass transferring process, particularly in the annealing furnace  20 , or during a process of transferring a glass after the annealing process. 
     Among them, a representative technique is to supply SO 2  gas to the lower surface of a glass at an initial stage of the glass annealing process or before the glass annealing process. If the SO 2  gas is sprayed to the lower surface of a glass as described above, the SO 2  gas reacts with alkali components of the glass, particularly sodium components, to form sulphate such as Na 2 SO 4 . In addition, the formed sulphate serves as a lubricant layer since its film strength is higher than that of a glass, thereby preventing scratches from occurring at the lower surface of the glass by the transfer means such as the roller  30  and improving the scratch resistance of the glass. 
     However, in case of a non-alkali glass substantially not containing an alkali component such as sodium, like a glass for LCD, even though SO 2  gas is supplied, a sulphate lubricant layer is not easily formed by an alkali metal such as Na 2 SO 4 . The SO 2  gas should react with components such as alkali earth metal like calcium in the glass to form a sulphate lubricant layer such as CaSO 4 , but the SO 2  gas does not easily react with alkali earth metals or the like in comparison to alkali metals such as sodium. Therefore, in order to form a lubricant layer such as CaSO 4 , an excessive amount of SO 2  gas should be used. However, if a lot of SO 2  gas is used, the production cost may increase accordingly. In addition, the toxicity of the SO 2  gas may act as a source of environmental pollution and cause serious harm to worker health. 
     Moreover, since manufacturing equipment or instruments such as the annealing furnace  20  may be easily corroded due to SO 2  gas, the productivity and process efficiency when manufacturing glasses may be adversely affected. For this reason, the SO 2  gas should be used as little as possible. However, in the conventional technique, an excessive amount of SO 2  gas should be inevitably used to form a lubricant layer for preventing scratches from occurring at the lower surface of a glass. 
     SUMMARY OF THE DISCLOSURE 
     Technical Problem 
     The present disclosure is designed to solve the problems of the prior art, and therefore it is an object of the present disclosure to provide an apparatus for forming a lubricant layer on the surface of a glass, which may use a small amount of SO 2  gas and effectively prevent scratches from occurring at the surface of the glass; an annealing furnace including the same; and a glass manufacturing apparatus including the same. 
     Other objects and advantages of the present disclosure will be understood by the following description and become more apparent from the embodiments of the present disclosure, which are set forth herein. It will also be apparent that objects and advantages of the present disclosure can be embodied easily by the means defined in claims and combinations thereof. 
     Technical Solution 
     In order to accomplish the above object, the present disclosure provides an apparatus for forming a lubricant layer on the surface of a glass, which includes: a SO 2  supply unit for supplying SO 2  gas; a O 2  supply unit for supplying O 2  gas; and a catalyst retaining unit for retaining a SO 2  gas oxidation catalyst, the catalyst retaining unit receiving SO 2  gas and O 2  gas from the SO 2  supply unit and the O 2  supply unit to generate SO 3  gas and supplying the generated SO 3  gas to a glass. 
     Preferably, the SO 2  gas oxidation catalyst includes V 2 O 5 . Also preferably, the catalyst retaining unit has a cylindrical shape with an inlet and an outlet and retains the SO 2  gas oxidation catalyst therein, SO 2  gas and O 2  gas flow into the catalyst retaining unit through the inlet, and SO 3  gas flows out of the catalyst retaining unit through the outlet. 
     Also preferably, the catalyst retaining unit has a structural shape containing the SO 2  gas oxidation catalyst as a component. 
     In another aspect, the present disclosure also provides an annealing furnace, which includes the apparatus for forming a lubricant layer on the surface of a glass, described above. 
     In another aspect, the present disclosure also provides a glass manufacturing apparatus, which includes the apparatus for forming a lubricant layer on the surface of a glass, described above. 
     Advantageous Effects 
     According to the present disclosure, since a lubricant layer is easily formed at the surface of a glass, particularly the lower surface of the glass which directly contacts transfer means such as a roller, the scratch resistance of the glass may be improved. Therefore, when the glass is transferred by the transfer means such as a roller and a belt during a manufacturing process such as a glass annealing process, it is possible to effectively prevent flaws, cracks or scratches from occurring at the lower surface of the glass. Therefore, a defect rate may be lowered during the glass manufacturing process and a high-quality glass may be obtained. In addition, since scratches at the glass decrease, time and costs required for polishing the glass may be reduced. 
     Further, according to the present disclosure, a sulphate lubricant layer may be sufficiently formed at the surface of a glass by using a small amount of SO 2  gas. Therefore, it is possible to suppress SO 2  gas with strong toxicity causing environmental pollution and bringing harmful working conditions to a worker who forms the lubricant layer. In addition, the SO 2  gas may be more simply purchased and treated at low costs. Moreover, it is possible to suppress that glass manufacturing equipment or instruments such as an annealing furnace from being corroded by the SO 2  gas, which may extend the life span of the glass manufacturing equipment or instruments. 
     Particularly, in case of a non-alkali glass substantially not containing an alkali metal such as sodium, like a glass for LCD, a sulphate lubricant layer may be sufficiently formed by using a relatively small amount of SO 2  gas. 
     In addition, since the time required for forming the sulphate lubricant layer is shortened, the time required for the entire glass manufacturing process may be shortened and the production cost may be reduced. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other objects and aspects of the present disclosure will become apparent from the following descriptions of the embodiments with reference to the accompanying drawings in which: 
         FIG. 1  is a schematic diagram showing a system for manufacturing a float glass; 
         FIG. 2  is a block diagram schematically showing a functional configuration of an apparatus for forming a lubricant layer on the surface of a glass according to a preferred embodiment of the present disclosure; 
         FIG. 3  is a cross-sectional view schematically showing an apparatus for forming a lubricant layer on the surface of a glass, which includes a cylindrical catalyst retaining unit, according to an embodiment of the present disclosure, in relation to an annealing furnace; 
         FIG. 4  is a cross-sectional view schematically showing an apparatus for forming a lubricant layer on the surface of a glass, which includes a cylindrical catalyst retaining unit, according to another embodiment of the present disclosure, in relation to an annealing furnace; 
         FIG. 5  is a cross-sectional view schematically showing an apparatus for forming a lubricant layer on the surface of a glass, which includes a cylindrical catalyst retaining unit, according to still another embodiment of the present disclosure, in relation to an annealing furnace; 
         FIG. 6  is a cross-sectional view schematically showing an apparatus for forming a lubricant layer on the surface of a glass, which includes a structural catalyst retaining unit, according to another further embodiment of the present disclosure, in relation to an annealing furnace; 
         FIG. 7  is a schematic diagram showing a device for supplying SO 2  gas and a SO 2  gas oxidation catalyst to a glass plate to cause an oxidation reaction of the SO 2  gas at the surface of the glass plate according to an embodiment of the present disclosure; 
         FIG. 8  is a diagram showing rates of forming a sulphate lubricant layer at a glass plate in an annealing furnace with different colors in a case where SO 3  gas is supplied to the annealing furnace by the apparatus for forming a lubricant layer on the surface of a glass according to an embodiment of the present disclosure; and 
         FIG. 9  is a diagram showing rates of forming a sulphate lubricant layer at a glass plate in an annealing furnace with different colors in a case where SO 3  gas is supplied directly to the annealing furnace according to a comparative example of the present disclosure. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Prior to the description, it should be understood that the terms used in the specification and the appended claims should not be construed as limited to general and dictionary meanings, but interpreted based on the meanings and concepts corresponding to technical aspects of the present disclosure on the basis of the principle that the inventor is allowed to define terms appropriately for the best explanation. 
     Therefore, the description proposed herein is just a preferable example for the purpose of illustrations only, not intended to limit the scope of the disclosure, so it should be understood that other equivalents and modifications could be made thereto without departing from the spirit and scope of the disclosure. 
       FIG. 2  is a block diagram schematically showing a functional configuration of an apparatus for forming a lubricant layer on the surface of a glass according to a preferred embodiment of the present disclosure. 
     Referring to  FIG. 2 , the apparatus for forming a lubricant layer on the surface of a glass according to the present disclosure includes a SO 2  supply unit  110 , an O 2  supply unit  120  and a catalyst retaining unit  130 . 
     The SO 2  supply unit  110  and the O 2  supply unit  120  supply SO 2  gas and O 2  gas to the catalyst retaining unit  130 , respectively. The SO 2  gas supplied by the SO 2  supply unit  110  reacts with the O 2  gas supplied by the O 2  supply unit  120  at the catalyst retaining unit  130  to generate SO 3  gas. In other words, under an oxidation circumstance where oxygen is present, the SO 2  gas reacts with oxygen and is oxidized into SO 3  gas as shown in Formula 1 below. 
       SO 2 ( g )+½×O 2 ( g )→SO 3 ( g )  Formula 1
 
     Meanwhile, the O 2  supply unit  120  may supply O 2  gas in various forms. For example, the O 2  supply unit  120  may supply pure O 2  gas or air so that the O 2  gas may be supplied to the catalyst retaining unit  130 . In addition, the O 2  supply unit  120  may supply moisture to the catalyst retaining unit  130 . In other words, the oxygen for oxidizing SO 2  gas may be supplied in various forms so that the oxidation of SO 2  gas may be activated. 
     Preferably, the SO 2  supply unit  110  may supply SO 2  gas at a flow rate of 0.05 Nm 3 /Hr to 10 Nm 3 /Hr. In addition, the O 2  supply unit  120  may supply O 2  gas at a flow rate of 0.05 Nm 3 /Hr to 10 Nm 3 /Hr. If the O 2  supply unit  120  supplies air so that the O 2  gas is supplied, the air may be supplied at a flow rate of 0.5 Nm 3 /Hr to 20 Nm 3 /Hr. 
     The SO 2  supply unit  110  may supply SO 2  gas at a flow rate of 0.05 Nm 3 /Hr to 7 Nm 3 /Hr. In other case, the SO 2  supply unit  110  may supply SO 2  gas at a flow rate of 3 Nm 3 /Hr to 10 Nm 3 /Hr. In addition, the O 2  supply unit  120  may supply O 2  gas at a flow rate of 0.05 Nm 3 /Hr to 7 Nm 3 /Hr. In other case, the O 2  supply unit  120  may supply O 2  gas at a flow rate of 3 Nm 3 /Hr to 10 Nm 3 /Hr. 
     In a case where the SO 2  gas and the O 2  gas are supplied at the above rates, the reaction of SO 2  gas and O 2  gas is activated, and so the SO 2  gas may be oxidized more actively into SO 3  gas. However, the supplying rate of SO 2  gas and O 2  gas may be changed in various ways according to various general conditions, and the present disclosure is not limited to the above rates. For example, the SO 2  supply unit  110  may supply SO 2  gas at a flow rate lower than 0.05 Nm 3 /Hr or higher than 10 Nm 3 /Hr. In addition, the O 2  supply unit  120  may supply O 2  gas at a flow rate lower than 0.05 Nm 3 /Hr or higher than 10 Nm 3 /Hr. 
     As described above, the catalyst retaining unit  130  receives SO 2  gas and O 2  gas from the SO 2  supply unit  110  and the O 2  supply unit  120  and allows SO 3  gas to be generated by the reaction of SO 2  gas and O 2  gas. In addition, the catalyst retaining unit  130  supplies the generated SO 3  gas to the surface of a glass. 
     The SO 3  gas supplied by the catalyst retaining unit  130  as described above may react with a certain component of the glass and generate sulphate near the surface of the glass. In addition, the sulphate may serve as a lubricant layer at the surface of the glass. Particularly, in case of a non-alkali glass, the SO 3  gas generated and supplied by the catalyst retaining unit  130  may react with a component such as calcium contained in the glass as shown in Formula 2 below to form a sulphate lubricant layer. 
       SO 3 ( g )+CaO( s )→CaSO 4 ( s )  Formula 2
 
     Even though Formula 2 shows only the process where SO 2  gas reacts with calcium oxide in the glass to form a CaSO 4  lubricant layer, the SO 2  gas may also react with another component of the glass to form a lubricant layer by another kind of sulphate. For example, the SO 2  gas may react with MgO or Cr 2 O 3  of the glass to form a sulphate lubricant layer such as MgSO 4  and Cr 2 (SO 4 ) 3 . Since the SO 3  gas supplied to the glass as described above reacts with a certain component of the glass and forms a lubricant layer at the surface by sulphate, it is possible to prevent flaws, cracks or scratches from occurring at the surface of the glass. 
     Preferably, the catalyst retaining unit  130  according to the present disclosure may supply SO 3  gas at a flow rate of 0.05 Nm 3 /Hr to 10 Nm 3 /Hr. In a case where the SO 3  gas is supplied at the above rate, a lubricant layer may be formed more actively at the lower surface of the glass. The catalyst retaining unit  130  may supply SO 3  gas at a flow rate of 0.05 Nm 3 /Hr to 7 Nm 3 /Hr. In other case, the catalyst retaining unit  130  may supply SO 3  gas at a flow rate of 3 Nm 3 /Hr to 10 Nm 3 /Hr. However, the SO 3  gas supplying rate of the catalyst retaining unit  130  may be changed in various ways according to various conditions such as a glass size or a shape of the apparatus for forming a lubricant layer on the surface of a glass, and the present disclosure is not limited to the above rate range. 
     Particularly, the catalyst retaining unit  130  according to the present disclosure retains a SO 2  gas oxidation catalyst. Here, the SO 2  gas oxidation catalyst represents a catalyst which may promote a chemical reaction of Formula 1 where SO 2  gas is oxidized into SO 3  gas. 
     Since the catalyst retaining unit  130  retains the SO 2  gas oxidation catalyst as described above, the catalyst retaining unit  130  promotes an oxidation reaction of SO 2  gas into SO 3  gas. In addition, as SO 2  gas is oxidized into SO 3  gas more and more, the sulphate lubricant layer, namely the CaSO 4  lubricant layer of Formula 2, may also be formed more and more by SO 3  gas. Therefore, according to the present disclosure, the sulphate lubricant layer such as CaSO 4  may be sufficiently formed at the surface of the glass by using just a small amount of SO 2  gas. 
     Preferably, the SO 2  gas oxidation catalyst may include V 2 O 5 . In other words, the catalyst retaining unit  130  may retain vanadium pentoxide as a part or all of the SO 2  gas oxidation catalyst. Such vanadium pentoxide is a representative SO 2  gas oxidation catalyst which promotes the oxidation reaction of SO 2  gas into SO 3  gas. Since V 2 O 5  has good resistance against catalyst inactivation of SO 2  gas, V 2 O 5  is a good SO 2  gas oxidation catalyst in the present disclosure. 
     In addition, various kinds of SO 2  gas oxidation catalysts may also be used in addition to V 2 O 5 . For example, Fe 2 O 3 , CuO, TiO 2 , Cr 2 O 3 , SiO 2 , CaO, Al 2 O 3 , WO 3  or the like may be used as the SO 2  gas oxidation catalyst, and at least two of them may be combined and used. As described above, the SO 2  gas oxidation catalyst is not limited to specific kinds and may promote the oxidation of SO 2  gas into SO 3  gas. 
     Moreover, the SO 2  gas oxidation catalyst may be used together with another material which enhances catalyst activation. For example, V 2 O 5  may be used together with K 2 O, K 2 SO 4 , K 2 S 2 O 7  or the like, which enhances catalyst activation of V 2 O 5 . Therefore, the catalyst retaining unit  130  may further retain at least one of K 2 O, K 2 SO 4  and K 2 S 2 O 7  in addition to V 2 O 5 . At this time, K 2 O, K 2 SO 4  or K 2 S 2 O 7  may be retained in the catalyst retaining unit  130  in various forms. For example, K 2 O, K 2 SO 4  or K 9 S 2 O 7  may be received in the catalyst retaining unit  130  in advance together with V 2 O 5  or may be supplied afterwards separately from V 2 O 5 . 
     As described above, according to the present disclosure, when the SO 2  gas is oxidized into SO 3  gas under an oxidation environment, the SO 2  gas oxidation catalyst activates the oxidation of SO 2  gas, and so a lubricant layer may be sufficiently formed at the surface of the glass by sulphate. Particularly, in case of a non-alkali glass substantially not containing alkali ions such as sodium, the lubricant layer may not be easily formed in comparison to the alkali glass. However, according to the present disclosure, since the oxidation reaction of SO 2  gas as shown in Formula 1 may be promoted by means of the SO 2  gas oxidation catalyst, in a non-alkali glass, a lubricant layer may be rapidly and sufficiently formed by means of sulphate by using a small amount of SO 2  gas. 
     Even though the above embodiments have been illustrated based on the case where the present disclosure is applied to a non-alkali glass, it does not mean that the present disclosure must be applied to a non-alkali glass. In other words, the present disclosure may also be applied to an alkali glass, and in case of an alkali glass, the formation of alkali metal sulphate such as Na 2 SO 4  may be promoted. Therefore, in this case, a lubricant layer may also be sufficiently formed by using a small amount of SO 2  gas. 
       FIG. 3  is a cross-sectional view showing the apparatus for forming a lubricant layer on the surface of a glass, which includes a cylindrical catalyst retaining unit  130  according to an embodiment of the present disclosure, in relation to the annealing furnace  20 . 
     Referring to  FIG. 3 , the glass formed in a forming process experiences an annealing process in the annealing furnace  20 . Here, the glass may be formed in various ways, and the present disclosure is not limited to a specific glass forming way. For example, a glass may be formed by a float process. In other words, a glass may be formed by supplying a molten glass to a float bath  10  storing a molten metal M and then floating or spreading the glass on the molten metal M as shown in  FIG. 1 . At this time, the thickness of a glass ribbon may be adjusted by controlling or changing the amount of glass put through the inlet of the float bath  10  or forming means such as a top roller installed in the float bath. This float glass manufacturing method includes cyclic successive processes and may operate constantly without a cessation, which allows flat glasses to be manufactured for several years without a pause. This is very suitable as a glass forming way. The present disclosure may be used for forming a lubricant layer on the surface of a glass formed by various glass forming methods such as a float process. 
     The glass formed in a float bath or the like as described above is put into the inlet  21  of the annealing furnace and is then annealed while being transferred toward the outlet  22  of the annealing furnace by at least one roller  30  provided at the annealing furnace  20 . At this time, the inlet  21  of the annealing furnace may have a temperature of about 700 to 800° C., and the outlet  22  of the annealing furnace may have a temperature of about 200 to 300° C. 
     As described above, the apparatus for forming a lubricant layer on the surface of a glass according to the present disclosure includes the SO 2  supply unit  110 , the O 2  supply unit  120  and the catalyst retaining unit  130 . Particularly, the catalyst retaining unit  130  may have a cylindrical shape with an inlet  131  and an outlet  132  as shown in  FIG. 3 . Here, the cylindrical shape means a shape with a hollow, and its section is not limited to a circular shape. For example, the cylindrical catalyst retaining unit  130  may be implemented in various shapes such as cylindrical, hexagonal and octagonal shapes. 
     Since the cylindrical catalyst retaining unit  130  has a hollow space as described above, SO 2  gas and O 2  gas may react to generate SO 3  gas. Particularly, since the catalyst retaining unit  130  according to the present disclosure retains the SO 2  gas oxidation catalyst such as V 2 O 5 , it is possible to further promote that SO 2  gas is oxidized in the catalyst retaining unit  130  to generate SO 3  gas. Therefore, a sufficient amount of SO 3  gas may be supplied to the surface of the glass, and so sulphate may be formed more actively at the lower surface of the glass by the SO 3  gas. Therefore, according to this embodiment, the lubricant layer is sufficiently formed at the lower surface of the glass by the sulphate, thereby preventing scratches from occurring at the lower surface of the glass due to transfer means such as the roller  30  located in the annealing furnace  20  and a roller provided at a process after the annealing furnace  20 . 
     Meanwhile, since the inlet  131  and the outlet  132  are provided at the cylindrical catalyst retaining unit  130 , SO 2  gas and O 2  gas may flow into the cylindrical catalyst retaining unit  130  through the inlet  131  and the SO 3  gas generated in the cylindrical catalyst retaining unit  130  may flow out through the outlet  132 . Even though  FIG. 3  illustrates that the cylindrical catalyst retaining unit  130  has two inlets  131  and one outlet  132 , respectively, it is just an example, and the number of inlet  131  and the number of outlet  132  may be variously selected in the catalyst retaining unit  130 . 
     As shown in  FIG. 3 , the catalyst retaining unit  130  may be located out of the annealing furnace  20  of the glass manufacturing apparatus. At this time, the outlet  132  of the catalyst retaining unit  130  connected to the inside of the annealing furnace  20  so that SO 3  gas may be supplied to the glass in the annealing furnace  20  through the outlet  132 . 
     The SO 2  gas oxidation catalyst may have a pellet form, a powder form or their combinations in the catalyst retaining unit  130 . For example, V 2 O 5  in a powder form or a pellet form such as rings or cylinders may be received in the catalyst retaining unit  130 . In a case where the SO 2  gas oxidation catalyst is included in a pellet form or a powder form, the reaction area increases and the oxidation reaction of the SO 2  gas may be performed more actively. However, the present disclosure is not limited to a specific form or state of the SO 2  gas oxidation catalyst and the SO 2  gas oxidation catalyst may be implemented in various forms or states if it may promote oxidation of SO 2  gas. 
     Preferably, as shown in  FIG. 3 , the catalyst retaining unit  130  may include a filter  133  in at least one of the inlet  131  and the outlet  132 . Here, the filter  133  filters the SO 2  gas oxidation catalyst and prevents the SO 2  gas oxidation catalyst such as V 2 O 5  from leaking out from the inside of the catalyst retaining unit  130 . Particularly, in a case where the SO 2  gas oxidation catalyst flows from the inside of the catalyst retaining unit  130  to the annealing furnace  20  and is attached to the surface of a glass, the glass quality may be deteriorated. However, if the filter  133  is provided to the inlet  131  and the outlet  132  of the catalyst retaining unit  130  as in this embodiment, this problem may be prevented. 
     Also preferably, the catalyst retaining unit  130  may be heated to a predetermined temperature. The reaction of SO 2  gas and O 2  gas as shown in Formula 1 may be performed actively at a predetermined temperature, for example about 500° C. Therefore, heat may be applied to the catalyst retaining unit  130  from the outside to reach a temperature at which the oxidation reaction of SO 2  gas is activated, thereby promoting the formation of a lubricant layer at the surface of the glass by SO 3  gas. Preferably, the catalyst retaining unit  130  may be heated to a temperature of 300° C. to 700° C. More preferably, the catalyst retaining unit  130  may be heated to a temperature of 450° C. to 650° C. 
     In addition, the SO 2  gas and the O 2  gas may be supplied in a heated state to the catalyst retaining unit  130  so that the SO 2  gas may be actively oxidized. For example, SO 2  gas and O 2  gas may be heated in the SO 2  supply unit  110  and the O 2  supply unit  120  or may be heated while being transferred from the SO 2  supply unit  110  and the O 2  supply unit  120  to the catalyst retaining unit  130 . 
     Meanwhile, the SO 3  gas flowing out from the outlet  132  of the catalyst retaining unit  130  is preferably kept over a predetermined temperature. SO 3  gas may be converted into a liquid state at a normal temperature, and in this case, the SO 3  gas generated at the catalyst retaining unit  130  may be adsorbed to a SO 3  supply tube or the like while being supplied to a glass into the annealing furnace  20 . In addition, SO 3  liquid may corrode glass manufacturing equipment made of SUS or the like. Therefore, the SO 3  gas flowing out from the catalyst retaining unit  130  is maintained over a predetermined temperature as described above so that the SO 3  gas is not liquefied, thereby preventing the above problem. 
     In order to maintain the SO 3  gas flowing from the catalyst retaining unit  130  over a predetermined temperature, various methods may be used. For example, a separate heating device may be provided to a SO 3  supply tube extending from the outlet  132  of the catalyst retaining unit  130  to the annealing furnace  20  to heat SO 3  gas. In other case, an insulator may be provided to the outside of the SO 3  supply tube so that the heat of SO 3  gas generated from the catalyst retaining unit  130  is not emitted out, thereby maintaining the SO 3  gas over a predetermined temperature. 
     Meanwhile, even though  FIG. 3  illustrates that a single catalyst retaining unit  130  is provided, it is just an example, and the present disclosure is not limited to the number of the catalyst retaining unit  130 . 
       FIG. 4  is a cross-sectional view showing an apparatus for forming a lubricant layer on the surface of a glass, which includes a plurality of cylindrical catalyst retaining units  130 , according to another embodiment of the present disclosure, in relation to the annealing furnace  20 . 
     Referring to  FIG. 4 , the apparatus for forming a lubricant layer on the surface of a glass includes three catalyst retaining units  130 . In addition, the outlet  132  of each of three catalyst retaining units  130  is connected to the inside of the annealing furnace  20  to supply the SO 3  gas generated therein to a glass in the annealing furnace  20 . As described above, the apparatus for forming a lubricant layer on the surface of a glass may include a plurality of catalyst retaining units  130 , and at this time, SO 2  gas oxidation catalysts retained in at least two catalyst retaining units  130  may be different from each other in their kinds. For example, in the embodiment of  FIG. 4 , SO 2  gas oxidation catalysts retained in three catalyst retaining units  130  may be V 2 O 5 , Fe 2 O 3  and CuO, which are different from each other. In this embodiment, since various kinds of SO 2  gas oxidation catalysts are used in a single apparatus for forming a lubricant layer on the surface of a glass, the effect may be improved. 
     In addition, even though  FIG. 3  illustrates that the catalyst retaining unit  130  is located at the outside of the annealing furnace  20 , the catalyst retaining unit  130  may also be located at the inside of the annealing furnace  20 . 
       FIG. 5  is a cross-sectional view schematically showing an apparatus for forming a lubricant layer on the surface of a glass, which includes a cylindrical catalyst retaining unit  130 , according to still another embodiment of the present disclosure, in relation to the annealing furnace  20 . 
     Referring to  FIG. 5 , the catalyst retaining unit  130  employed in the apparatus for forming a lubricant layer on the surface of a glass may be located at the inside of the annealing furnace  20  of the glass manufacturing apparatus. In a case where the catalyst retaining unit  130  is provided in the annealing furnace  20  as described above, the volume of an annealing furnace  20  or a glass manufacturing apparatus, which includes the apparatus for forming a lubricant layer on the surface of a glass according to the present disclosure, may be reduced. In addition, in this embodiment, due to the internal temperature of the annealing furnace  20 , heat may be constantly applied to the catalyst retaining unit  130  so that SO 2  gas may be actively oxidized. In addition, since the internal heat of the annealing furnace  20  is also applied to the SO 3  gas generated by the catalyst retaining unit  130 , it is possible to prevent the SO 3  gas from being liquefied. 
     Meanwhile, even though the embodiments of  FIGS. 3 to 5  have been illustrated based on the case where the catalyst retaining unit  130  has a cylindrical shape, the present disclosure is not limited to such a specific shape of the catalyst retaining unit  130 . In other words, in the apparatus for forming a lubricant layer on the surface of a glass according to the present disclosure, the catalyst retaining unit  130  may be present in various shapes. 
       FIG. 6  is a cross-sectional view schematically showing an apparatus for forming a lubricant layer on the surface of a glass, which includes the structural catalyst retaining unit  130 , according to another further embodiment of the present disclosure, in relation to the annealing furnace  20 . 
     Referring to  FIG. 6 , the catalyst retaining unit  130  may have a shape of a structure  134  which contains a SO 2  gas oxidation catalyst as a component. For example, the catalyst retaining unit  130  may be a structure containing V 2 O 5  as a component. The structure  134  containing such a SO 2  gas oxidation catalyst as a component may be implemented in various ways. For example, after coating glass fibers with filler and drying and thermally treating the same to form a structure, a SO 2  gas oxidation catalyst may be supported by the structure by means of a binder. 
     As described above, in a case where the catalyst retaining unit  130  has a form of the structure  134  containing the SO 2  gas oxidation catalyst as a component, the structure  134  may be implemented in a honeycomb (hive) type or a plate type. In addition, the structure  134  may be implemented in a pellet type such as cylinders and rings. 
     However, the present disclosure is not limited to such a specific forming method or type of the structure  134 , and the structure  134  containing the SO 2  gas oxidation catalyst as a component may be implemented by various structure manufacturing methods or in various structural types, well known in the art at the filing of the present disclosure. 
     Meanwhile, as shown in  FIG. 6 , the structure  134  containing the SO 2  gas oxidation catalyst as a component may be located at the inside of the annealing furnace  20  of the glass manufacturing apparatus. In this case, even though the apparatus for forming a lubricant layer on the surface of a glass according to the present disclosure is included thereon, the size of the annealing furnace  20  does not substantially increase, and the internal heat of the annealing furnace  20  may be utilized. 
     The annealing furnace  20  of the glass manufacturing apparatus according to the present disclosure includes the apparatus for forming a lubricant layer on the surface of a glass as described above. For example, the annealing furnace according to an embodiment of the present disclosure includes the apparatus for forming a lubricant layer on the surface of a glass as shown in  FIGS. 3 to 6 . If the annealing furnace  20  of the glass manufacturing apparatus according to the present disclosure is used, since the apparatus for forming a lubricant layer on the surface of a glass, included therein, may rapidly and sufficiently form a lubricant layer at the surface of a glass, particularly at the lower surface of the glass, it is possible to prevent scratches from occurring at the lower surface of the glass due to transfer means such as the roller  30  of the annealing furnace  20  or a roller after the annealing furnace  20 . 
     Preferably, the apparatus for forming a lubricant layer on the surface of a glass is provided at the inlet  21  of the annealing furnace. Since the inlet  21  of the annealing furnace has a higher temperature than the outlet  22 , the oxidation of SO 2  gas and the formation of sulphate by SO 3  gas may be promoted. In addition, since the sulphate lubricant layer is formed at the surface of the glass before the location of the roller  30  provided at the annealing furnace  20 , it is possible to prevent the lower surface of the glass from being damaged at an earlier stage. 
     In addition, the glass manufacturing apparatus according to the present disclosure includes the apparatus for forming a lubricant layer on the surface of a glass. Therefore, if the glass manufacturing apparatus according to the present disclosure is used, the damage of the lower surface of a glass, which may occur during a glass transferring process in the glass manufacturing method, may be effectively prevented. 
     Hereinafter, the present disclosure will be described in more detail based on examples and comparative examples. The embodiments of the present disclosure, however, may take several other forms, and the scope of the present disclosure should not be construed as being limited to the following examples. The embodiments of the present disclosure are provided to more fully explain the present disclosure to those having ordinary knowledge in the art to which the present disclosure pertains. 
     First, the examples and the comparative examples will be compared to look into the effect of promoting the formation of a sulphate lubricant layer at the surface of a glass, in a case where a SO 2  gas oxidation catalyst is supplied together with SO 2  gas as in the present disclosure. 
     Example 1 
       FIG. 7  is a schematic diagram showing a device for supplying SO 2  gas and an SO 2  gas oxidation catalyst to a glass plate to cause an oxidation reaction of the SO 2  gas at the surface of the glass plate according to an embodiment of the present disclosure. 
     As an example according to the present disclosure, as shown in  FIG. 7 , a glass plate for LCD with a size of 15×15 mm was prepared and sealed with an O-ring. After that, the glass plate was put into a quartz tube furnace  40  of 750° C., and SO 2  gas and O 2  gas were supplied thereto to make an environment of SO 2  5%, O 2  10%. In addition, V 2 O 5  powder was placed on the supply path of the SO 2  gas and the O 2  gas so that the V 2 O 5  powder served as a SO 2  gas oxidation catalyst. In addition, this state was maintained for 60 minutes so that the reactions of Formulas 1 and 2 occur in the tube furnace  40 . 
     And then, the tube furnace  40  was sufficiently cooled and all reaction gases were exhausted out of the tube furnace  40  by using nitrogen gas. 
     After that, the IC (Ion Chromatography) analysis was performed to the glass plate of Example 1. The analysis results are shown in Table 1 below. Here, the IC analysis is an analysis method for comparing the degree of sulphate such as CaSO 4  formed at the surface of the glass plate as a lubricant layer. For the IC analysis, each glass plate was put into 10 mg DI water and maintained at 60° C. for 10 minutes so that CaSO 4  at the surface of the glass plate is dissolved in the DI water, and the IC analysis was performed to the solution. At this time, the dissolution of CaSO 4  was checked by performing an ESCA analysis before or after the IC analysis. 
     Comparative Example 1 
     As a comparative example to be compared with Example 1, a glass plate for LCD with a size of 15×15 mm was sealed with an O-ring and then put into a tube furnace  40  of 750° C., and SO 2  gas and O 2  gas were supplied thereto to make an environment of SO 2  5%, O 2  10%, similar to Example 1. However, V 2 O 5  powder was not supplied, different from Example 1. In addition, this state was maintained for 60 minutes so that the reactions of Formulas 1 and 2 occur. After the glass plate of Comparative Example 1 was reacted, the tube furnace  40  was cooled and all reaction gases were exhausted out of the tube furnace  40  by using nitrogen gas. 
     After that, the IC analysis was performed to the glass plate of Comparative Example 1, similar to Example 1. The analysis results are shown in Table 1 below. 
     
       
         
           
               
               
               
               
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                   
                   
                   
                   
                   
                 IC 
               
               
                   
                 SO 2   
                 O 2   
                 Reaction 
                 Temp. 
                   
                 analysis 
               
               
                   
                 (%) 
                 (%) 
                 time (min) 
                 (° C.) 
                 V 2 O 5   
                 (ppm) 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 Example 1 
                 5 
                 10 
                 60 
                 750 
                 Used 
                 8.70 
               
               
                 Comparative 
                   
                   
                   
                   
                 X 
                 1.10 
               
               
                 Example 1 
               
               
                   
               
            
           
         
       
     
     Referring to Table 1, in case of Example 1 using V 2 O 5  as a SO 2  gas oxidation catalyst together with SO 2  gas and O 2  gas, the IC analysis result was 8.70 ppm. Meanwhile, in case of Comparative Example 1 where V 2 O 5  was not used and only SO 2  gas and O 2  gas were supplied to the glass, the IC analysis result was 1.10 ppm. From the results, it may be understood that CaSO 4  serving as a lubricant layer is formed much more on the surface of the glass plate in the case where V 2 O 5  serving as a SO 2  gas oxidation catalyst is used together with SO 2  gas. 
     Therefore, it could be understood that, when forming a sulphate lubricant layer at the surface of a glass by using SO 2  gas, if the SO 2  gas oxidation catalyst such as V 2 O 5  is used as in the present disclosure, the lubricant layer may be formed more easily. 
     Hereinafter, in a case where the apparatus for forming a lubricant layer on the surface of a glass according to a detailed embodiment of the present disclosure is provided to the annealing furnace, the effect of promoting the formation of a sulphate lubricant layer at the surface of a glass annealed in an annealing furnace will be discussed. 
     Example 2 
     As an example according to the present disclosure, as shown in  FIG. 3 , the apparatus for forming a lubricant layer on the surface of a glass, which contains V 2 O 5 , received SO 2  gas and O 2  gas, generated SO 3  gas, and supplied the SO 3  gas to the annealing furnace where a glass was annealed. At this time, the apparatus for forming a lubricant layer on the surface of a glass received the SO 2  gas at a flow rate of 6 Nm 3 /Hr and received the O 2  gas at a flow rate of 3 Nm 3 /Hr. After that, with respect to an annealed glass plate with a predetermined size, the IC analysis was performed to simulate a forming rate of sulphate, similar to Example 1. The analysis results are shown in  FIG. 8 . In other words,  FIG. 8  is a diagram showing rates of forming a sulphate lubricant layer (MSO 4 ) at a glass plate in an annealing furnace with different colors in a case where SO 3  gas is supplied to the annealing furnace by the apparatus for forming a lubricant layer on the surface of a glass according to an embodiment of the present disclosure. In  FIG. 8 , the left side represents a direction toward the inlet of the annealing furnace and the right side represents a direction toward the outlet of the annealing furnace. In addition, the apparatus for forming a lubricant layer on the surface of a glass supplied SO 3  gas near the inlet of the annealing furnace. Moreover, an amount of a sulphate lubricant layer formed on the entire glass plate with a predetermined size according to Example 2 is shown in Table 2 below. 
     Comparative Example 2 
     As a comparative example to be compared with Example 2, a glass having the same kind and size as that of Example 2 was annealed in the same annealing furnace as in Example 2. The annealing furnace did not include the apparatus for forming a lubricant layer, shown in  FIG. 3 , and SO 2  gas and O 2  gas were directly supplied to the annealing furnace. At this time, SO 2  gas was supplied to the annealing furnace at a flow rate of 6 Nm 3 /Hr, and O 2  gas contained in the air was supplied to the annealing furnace at a flow rate of 800 Nm 3 /Hr. After that, with respect to a glass plate annealed in the annealing furnace, the IC analysis was performed to simulate a forming rate of sulphate. The analysis results are shown in  FIG. 9 . In other words,  FIG. 9  is a diagram showing rates of forming a sulphate lubricant layer at a glass plate in an annealing furnace with different colors in a case where SO 3  gas is supplied directly to the annealing furnace according to a comparative example of the present disclosure. In  FIG. 9 , the left side represents a direction toward the inlet of the annealing furnace and the right side represents a direction toward the outlet of the annealing furnace, similar to  FIG. 8 . In addition, SO 2  gas and air were supplied from the inlet of the annealing furnace. Moreover, an amount of a sulphate lubricant layer formed on the entire glass plate according to Comparative Example 2 with the same size as in Example 2 is shown in Table 2 below. 
     
       
         
           
               
               
               
               
             
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                   
                   
                 IC analysis 
               
               
                   
                 SO 2   
                 O 2   
                 (ppm) 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                   
                 Example 2 
                 6 Nm 3 /Hr 
                  3 Nm 3 /Hr 
                 0.725 
               
               
                   
                 Comparative 
                 6 Nm 3 /Hr 
                 800 Nm 3 /Hr 
                 0.082 
               
               
                   
                 Example 2 
                   
                 (Air) 
               
               
                   
                   
               
            
           
         
       
     
     First, referring to  FIG. 9  according to Comparative Example 2, a blue color is generally shown except for a portion near the inlet of the annealing where SO 2  gas and air are supplied, namely a left portion on the drawing. This means that a forming rate (d[MSO 4 ]/dt) of the sulphate lubricant layer at the surface of the glass plate is substantially close to 0 (zero) in the annealing furnace. Therefore, it may be understood that a sulphate lubricant layer is substantially not formed at the surface of the glass in the entire annealing furnace. Meanwhile, referring to  FIG. 8  according to Example 2 of the present disclosure, the annealing furnace shows a light blue color close to a green color as a whole rather than a dark blue color. This means that the forming rate of the sulphate lubricant layer at the surface of the glass plate is in the range of 0.1 to 0.3 ppm/min in the annealing furnace. Therefore, it may be understood that the sulphate lubricant layer is actively formed at the surface of the glass in the entire annealing furnace. Particularly, a portion near the inlet of the annealing furnace where SO 3  gas is supplied, namely a left portion on the drawing, shows red and yellow colors, and so it may be understood that the forming rate of the sulphate lubricant layer is in the range of 0.4 to 0.6 ppm/min. From the above results, in a case where the apparatus for forming a lubricant layer on the surface of a glass according to the present disclosure supplies SO 3  gas into the annealing furnace, it may be understood that the sulphate lubricant layer may be effectively formed at the surface of a glass in comparison to a conventional technique where SO 2  gas and air are supplied into annealing furnace. 
     In addition, referring to  FIG. 2 , in Example 2, the entire amount of generated sulphate according to the IC analysis results is 0.725 ppm, but in Comparative Example 2, the entire amount of generated sulphate according to the IC analysis results is 0.082 ppm. From this, in a case where the apparatus for forming a lubricant layer on the surface of a glass according to the present disclosure, which retains V 2 O 5  to promote oxidation of SO 2  gas and supplies the generated SO 3  gas to the annealing furnace as shown in  FIG. 3  is included in the annealing furnace, it may be understood that the formation of a lubricant layer by sulphate at the surface of a glass, which is to be annealed, is further promoted. 
     The present disclosure has been described in detail. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the disclosure, are given by way of illustration only, since various changes and modifications within the spirit and scope of the disclosure will become apparent to those skilled in the art from this detailed description. 
     Meanwhile, even though the term “unit” has been used in the specification, the term “unit” just represents a logic component and is not limited to a physically distinguishable component, as apparent to those skilled in the art.