Patent Publication Number: US-2021163333-A1

Title: Glass roll, glass roll manufacturing method, and quality evaluation method

Description:
TECHNICAL FIELD 
     The present invention relates to a glass roll, a glass roll manufacturing method, and a glass roll quality evaluation method. 
     BACKGROUND ART 
     As is well known, mobile devices, such as smartphones and tablet PCs, which have been rapidly spreading in recent years are required to be small in weight. Therefore, under the actual circumstances, glass substrates adopted in such devices are being reduced in thickness. As a result, a glass film obtained by reducing a thickness of a glass substrate to a thickness of a film (for example, a thickness of 300 μm or less) has been developed and manufactured. 
     The glass film is extremely small in thickness and hence has such flexibility that allows the glass film to be easily bent by hand. With this, for example, a glass roll can be manufactured by winding up a band-shaped glass film, which is continuously formed by an overflow down-draw method, around a winding core into a roll shape. In addition, in this glass roll, the band-shaped glass film may also be subjected to various processes (for example, division of unnecessary portions) through use of a roll-to-roll mode (see Patent Literature 1). 
     In the roll-to-roll mode, a band-shaped glass film wound around a first winding core as a glass roll is unwound from the first winding core and processed while being conveyed. After that, the processed band-shaped glass film is wound up around a second winding core different from the first winding core to obtain a glass roll again. 
     CITATION LIST 
     
         
         Patent Literature 1: JP 2017-077995 A 
       
    
     SUMMARY OF INVENTION 
     Technical Problem 
     Incidentally, when the above-mentioned roll-to-roll mode is used, there are the following problems to be solved. 
     Specifically, when the roll-to-roll mode is used, as illustrated in  FIG. 10 a   , a band-shaped leader  200  for pulling and guiding a band-shaped glass film  100  to a second winding core (not shown) may be coupled to the band-shaped glass film  100  through intermediation of a tape  300 . In such a case, in order to appropriately perform processing on the band-shaped glass film  100 , it is ideal that the subsequent band-shaped glass film  100  pass through, without deviation, a passage line through which the preceding leader  200  has passed. However, as illustrated in  FIG. 10 b   , due to excessive skew of the band-shaped glass film  100  (indicated by the outlined arrows in  FIG. 10 b   ), a passage line of the band-shaped glass film  100  deviates in a width direction, and in some cases, does not match with the passage line of the leader  200  (indicated by the two-dot chain lines in  FIG. 10 b   ). As a result, there is a defect in that the processing cannot be appropriately performed. 
     Further, as illustrated in  FIG. 11 a   , when nip rollers  600  formed of a pair of rollers configured to nip the band-shaped glass film  100  in a thickness direction of the band-shaped glass film  100  is arranged on a conveyance path of the band-shaped glass film  100  extending from a first winding core  400  to a second winding core  500 , there also occurs a problem caused by slack of the band-shaped glass film  100 . Specifically, as illustrated in  FIG. 11 b   , slack occurs in only one of end portions in a width direction of the band-shaped glass film  100  (hereinafter referred to as “single slack”) on an immediate upstream side of the nip rollers  600  on the conveyance path, and the single slack gradually deteriorates, with the result that the band-shaped glass film  100  may be broken. 
     The present invention that has been made in view of the above-mentioned circumstances has a technical object to provide a glass roll in which the occurrence of skew and single slack in a band-shaped glass film can be prevented when the roll-to-roll mode is used. 
     Solution to Problem 
     As a result of extensive studies, the inventors of the present invention have found that the occurrence of skew and single slack in the band-shaped glass film in the case of using the roll-to-roll mode is caused by creases formed on the band-shaped glass film. Then, the inventors of the present invention have found that, when the balance in number and size of the creases is unsatisfactory between the creases present in one side end portion in a width direction of the band-shaped glass film and the creases present in another side end portion thereof, skew and single slack are liable to occur. The above-mentioned creases may be present not only on the band-shaped glass film but also on, for example, a band-shaped resin film having a similar shape. However, even when the roll-to-roll mode is used for the band-shaped resin film, skew and single slack are less liable to occur. This is because of the following reason. The resin is rich in stretchability, and the creases are stretched by application of tension to the band-shaped resin film at the time of using the roll-to-roll mode. Thus, even when the above-mentioned balance is unsatisfactory, the influence thereof is small. Meanwhile, the creases formed on the band-shaped glass film are hardly stretched even with application of tension at the time of using the roll-to-roll mode. Therefore, when the above-mentioned balance is unsatisfactory, the influence caused by the creases cannot be eliminated, and skew and single slack are liable to occur. 
     According to the present invention which has been made based on the findings described above to solve the above-mentioned problem, there is provided a glass roll comprising a band-shaped glass film which is wound into a roll shape and has creases formed thereon, wherein the band-shaped glass film comprises an effective section in which one side edge and another side edge in a width direction extend in parallel to each other, and in which each of a leading end portion and a trailing end portion extends in parallel to the width direction of the band-shaped glass film, and wherein, when a length from the leading end portion to the trailing end portion along a surface of the effective section is measured along each of a first position along the one side edge of the band-shaped glass film and a second position along the another side edge of the band-shaped glass film, a difference between a first measurement length and a second measurement length which are respectively measured along the first position and the second position is 400 ppm or less of a longer measurement length of the first measurement length and the second measurement length. 
     In the glass roll of the present invention, the first measurement length and the second measurement length are each obtained by measuring the length from the leading end portion to the trailing end portion of the effective section along the surface of the effective section in the band-shaped glass film. When measurement along the surface is performed as described above, the influence of irregularities on the surface caused by the creases is reflected on the measurement results of both the measurement lengths, and the number quantity and size magnitude of the creases present between the leading end portion and the trailing end portion of the effective section along each of the first position and the second position are reflected as the magnitude of the measurement lengths on the measurement results. In this case, the first position and the second position are a position along the one side edge and a position along the another side edge in the width direction of the band-shaped glass film, respectively. In view of the foregoing, when the difference between the measurement lengths is found, the validity of the balance in number and size of the creases between the one side end portion and the another side end portion in the width direction of the band-shaped glass film is determined based on the magnitude of the difference. When the difference between both the measurement lengths is smaller, the balance is more satisfactory. Here, as a result of extensive studies, the inventors of the present invention have found that, when the roll-to-roll mode is used for the glass roll in which the difference between both the measurement lengths is 400 ppm or less of the longer measurement length of both the measurement lengths, the occurrence of skew and single slack in the band-shaped glass film can be prevented. As described above, according to the glass roll of the present invention, when the roll-to-roll mode is used, the occurrence of skew and single slack in the band-shaped glass film can be prevented. 
     In the glass roll of the present invention, both the first measurement length and the second measurement length are measured in the effective section in which the one side edge and the another side edge in the width direction of the band-shaped glass film extend in parallel to each other, and in which each of the leading end portion and the trailing end portion extends in parallel to the width direction of the band-shaped glass film. With this, the difference between lengths of the one side end portion and the another side end portion (lengths along a longitudinal direction of the band-shaped glass film), as well as the validity of the balance in number and size of the creases between the one side end portion and the another side end portion in the width direction of the band-shaped glass film, are prevented from being reflected as the difference between both the measurement lengths. For example, unlike the case of the glass roll of the present invention, when the lengths from the leading end portion to the trailing end portion of the band-shaped glass film along the surface of the band-shaped glass film are measured along the first position and the second position, instead of the effective section, to be defined as both the measurement lengths, the following defects may occur. Specifically, in the case in which the length of the one side end portion and the length of the another side end portion in the width direction of the band-shaped glass film are different from each other, even when the balance in number and size of the creases between the one side end portion and the another side end portion is satisfactory, the difference between both the measurement lengths may be increased by being added with the difference in length between the one side end portion and the another side end portion. Therefore, there is a risk in that the validity of the balance may not be accurately determined based on the difference between both the measurement lengths. In order to eliminate such risk, both the measurement lengths are measured in the effective section as described above. 
     In the above-mentioned glass roll, it is preferred that the difference between the first measurement length and the second measurement length be 200 ppm or less of the longer measurement length of the first measurement length and the second measurement length. 
     With this, the balance in number and size of the creases between the one side end portion and the another side end portion in the width direction of the band-shaped glass film becomes further satisfactory. Therefore, when the roll-to-roll mode is used, the above-mentioned configuration is more advantageous for preventing the occurrence of skew and single slack in the band-shaped glass film. 
     In the above-mentioned glass roll, it is preferred that the difference between the first measurement length and the second measurement length be 100 ppm or less of the longer measurement length of the first measurement length and the second measurement length. 
     With this, the balance in number and size of the creases between the one side end portion and the another side end portion in the width direction of the band-shaped glass film becomes even further satisfactory. Therefore, when the roll-to-roll mode is used, the above-mentioned configuration is even more advantageous for preventing the occurrence of skew and single slack in the band-shaped glass film. 
     In the above-mentioned glass roll, it is preferred that, when a length from the leading end portion to the trailing end portion along the surface of the effective section is measured as a third measurement length along a widthwise center line prevented from having the creases on the band-shaped glass film in addition to the first measurement length and the second measurement length, a larger difference of a difference between the first measurement length and the third measurement length and a difference between the second measurement length and the third measurement length is 500 ppm or less of a longest measurement length of the first measurement length, the second measurement length, and the third measurement length. 
     When processing is performed on the band-shaped glass film through use of the roll-to-roll mode, it is desired that the number and size of the creases formed on the band-shaped glass film be suppressed to the extent possible in order to suitably perform the processing. In this case, as described above, the number quantity and size magnitude of the creases present between the leading end portion and the trailing end portion of the effective section are reflected as the magnitude of the measurement length on the measurement results of the first measurement length and the second measurement length. Meanwhile, the third measurement length is obtained by measuring the length from the leading end portion to the trailing end portion of the effective section along the flat widthwise center line prevented from having the creases. That is, the influence of irregularities on the surface caused by the creases is not reflected on the measurement result of the third measurement length. In view of the foregoing, in the case in which the difference between the first measurement length and the third measurement length, and the difference between the second measurement length and the third measurement length are each found, when these differences are smaller, the number and size of the creases present in each of the one side end portion and the another side end portion in the width direction of the band-shaped glass film are more suppressed. As a result of extensive studies, the inventors of the present invention have found that, when the roll-to-roll mode is used for the glass roll in which the larger difference of the above-mentioned two differences is 500 ppm or less of the longest measurement length of the first measurement length to the third measurement length, the band-shaped glass film can be suitably processed. As described above, according to the glass roll of the present invention, the above-mentioned configuration is advantageous for suitably performing processing on the band-shaped glass film through use of the roll-to-roll mode. 
     In the above-mentioned glass roll, it is preferred that the larger difference be 300 ppm or less of the longest measurement length of the first measurement length, the second measurement length, and the third measurement length. 
     With this, the number and size of the creases present in each of the one side end portion and the another side end portion in the width direction of the band-shaped glass film are further suppressed. Thus, the above-mentioned configuration is further advantageous for suitably performing processing on the band-shaped glass film through use of the roll-to-roll mode. 
     In the above-mentioned glass roll, it is preferred that the larger difference be 200 ppm or less of the longest measurement length of the first measurement length, the second measurement length, and the third measurement length. 
     With this, the number and size of the creases present in each of the one side end portion and the another side end portion in the width direction of the band-shaped glass film are even further suppressed. Thus, the above-mentioned configuration is even further advantageous for suitably performing processing on the band-shaped glass film through use of the roll-to-roll mode. 
     Further, according to the present invention which has been made to solve the above-mentioned problem, there is provided a glass roll manufacturing method, comprising: a forming step of cooling and solidifying a glass ribbon, which is obtained by forming molten glass into a band shape with a forming trough, while pulling the glass ribbon in a longitudinal direction, to thereby obtain a band-shaped glass film having creases formed thereon; a dividing step of dividing both unnecessary portions that are respectively present at both ends in a width direction of the band-shaped glass film from an effective portion positioned between both the unnecessary portions; a winding step of winding up the divided band-shaped glass film formed of the effective portion into a roll shape, to thereby obtain a glass roll; and a measurement step of measuring, in a section to be measured which is formed along a longitudinal direction of the effective portion and in which each of a leading end portion and a trailing end portion extends in parallel to the width direction of the band-shaped glass film, a length from the leading end portion to the trailing end portion along a surface of the section to be measured along each of one side end portion and another side end portion in a width direction of the effective portion, wherein, when a difference between a first measurement length and a second measurement length which are respectively measured along the one side end portion and the another side end portion is more than 400 ppm of a longer measurement length of the first measurement length and the second measurement length, a first adjusting step of adjusting to reduce the difference between the first measurement length and the second measurement length is performed. 
     According to the method of the present invention, when the measurement step is performed, the validity of the balance in number and size of the creases between the one side end portion and the another side end portion in the width direction of the effective portion to be wound up as the divided band-shaped glass film is found as the difference between both the first measurement length and the second measurement length. When the difference between both the measurement lengths is more than 400 ppm of the longer measurement length of both the measurement lengths, that is, when the balance is unsatisfactory, the first adjusting step is performed. With this, the difference between both the measurement lengths is adjusted to be reduced, thereby improving the balance. As a result, it is possible to manufacture the glass roll by winding up the divided band-shaped glass film formed of the effective portion having satisfactory balance. When the roll-to-roll mode is used for this glass roll, the occurrence of skew and single slack in the divided band-shaped glass film can be suitably prevented. 
     In the above-mentioned glass roll manufacturing method, it is preferred that the first adjusting step comprise a step of adjusting to reduce a difference between speeds at which both one side end portion and another side end portion in a width direction of the glass ribbon respectively connected to the one side end portion and the another side end portion of the effective portion are cooled and solidified. 
     As a result of extensive studies, the inventors of the present invention have found that the deterioration of the balance in number and size of the creases between the one side end portion and the another side end portion in the width direction of the effective portion is caused by a difference between speeds at which both the one side end portion and the another side end portion in the width direction of the glass ribbon respectively connected to the one side end portion and the another side end portion of the effective portion are cooled and solidified. With this, when the difference between both the measurement lengths is more than 400 ppm of the longer measurement length of both the measurement lengths, the first adjusting step is performed to adjust to reduce the difference between the speeds at which the one side end portion and the another side end portion of the glass ribbon are cooled and solidified, thereby being capable of effectively improving the balance. 
     In the above-mentioned glass roll manufacturing method, it is preferred that, when the difference between the first measurement length and the second measurement length is more than 400 ppm of the longer measurement length, both the measurement step and the first adjusting step be alternately performed until the difference between the first measurement length and the second measurement length reaches 400 ppm or less of the longer measurement length while the section to be measured is changed to a new section every time the measurement step is performed. 
     With this, the effective portion having satisfactory balance in number and size of the creases between the one side end portion and the another side end portion in the width direction can be reliably formed. Therefore, it is possible to reliably manufacture the glass roll in which the divided band-shaped glass film formed of the effective portion having satisfactory balance is wound. 
     In the above-mentioned glass roll manufacturing method, it is preferred that the measurement step comprise measuring a length from the leading end portion to the trailing end portion along the surface of the section to be measured as a third measurement length along a center portion prevented from having the creases positioned between the one side end portion and the another side end portion of the effective portion in addition to the first measurement length and the second measurement length, and, when at least one of two differences comprising a difference between the first measurement length and the third measurement length and a difference between the second measurement length and the third measurement length is more than 500 ppm of a longest measurement length of the first measurement length, the second measurement length, and the third measurement length, a second adjusting step of adjusting to reduce the difference that is more than 500 ppm of the longest measurement length out of the two differences be performed. 
     With this, the difference between the first measurement length and the third measurement length, and the difference between the second measurement length and the third measurement length can be found in association with performance of the measurement step. It is determined whether or not the number and size of the creases are suppressed in each of the one side end portion and the another side end portion in the width direction of the effective portion (divided band-shaped glass film) based on the two differences. When at least one of the two differences is more than 500 ppm of the longest measurement length of the first measurement length to the third measurement length, that is, when the number and size of the creases are not sufficiently suppressed, the second adjusting step is performed. With this, of the two differences, the difference that is more than 500 ppm of the longest measurement length is adjusted to be reduced, thereby suppressing the number and size of the creases. As a result, it is possible to form the effective portion in which the number and size of the creases present in the one side end portion and the another side end portion are suppressed to the extent possible, and it is possible to manufacture the glass roll in which the divided band-shaped glass film formed of the effective portion is wound. Then, when the roll-to-roll mode is used for the glass roll, processing on the divided band-shaped glass film can be suitably performed. 
     In the above-mentioned glass roll manufacturing method, it is preferred that the second adjusting step be a step of adjusting to reduce a difference between speeds at which the one side end portion and the another side end portion of the glass ribbon are cooled and solidified and a speed at which the center portion positioned between both the one side end portion and the another side end portion is cooled and solidified. 
     As a result of extensive studies, the inventors of the present invention have found that the insufficient suppression of the number and size of the creases in the one side end portion and the another side end portion of the effective portion is caused by differences between speeds at which the one side end portion and the another side end portion of the glass ribbon are cooled and solidified and a speed at which the center portion positioned between both the end portions is cooled and solidified. Therefore, when at least one of the two differences is more than 500 ppm of the longest measurement length of the first measurement length to the third measurement length, the differences between the speeds at which the one side end portion and the another side end portion of the glass ribbon are cooled and solidified and the speed at which the center portion thereof is cooled and solidified are adjusted to be reduced by performing the second adjusting step. With this, the number and size of the creases can be effectively suppressed. 
     In the above-mentioned glass roll manufacturing method, it is preferred that, when at least one of the two differences is more than 500 ppm of the longest measurement length, both the measurement step and the second adjusting step be alternately performed until both the two differences reach 500 ppm or less of the longest measurement length while the section to be measured is changed to a new section every time the measurement step is performed. 
     With this, it is possible to reliably form the effective portion in which the balance in number and size of the creases is satisfactory between the one side end portion and the another side end portion in the width direction, and the number and size of the creases present in both the end portions are also sufficiently suppressed. Therefore, it is possible to reliably manufacture the glass roll of high quality comprising the divided band-shaped glass film formed of the effective portion. 
     In the above-mentioned glass roll manufacturing method, it is preferred that a measurement unit be used for measuring each of the measurement lengths, and the measurement unit comprise a rotating body which is allowed to move in a thickness direction of the section to be measured in conformity with irregularities on the surface of the section to be measured caused by the creases while rotating through friction with the surface of the section to be measured under a state of being held in contact with the surface of the section to be measured, and be configured to measure each of the measurement lengths based on a distance by which the rotating body rolls on the surface of the section to be measured. 
     With this, the rotating body provided to the measurement unit can move in the thickness direction of the section to be measured in conformity with the irregularities on the surface of the section to be measured. Therefore, when each of the measurement lengths is measured, the risk in that the creases are pressurized to be crushed with a force applied to the creases can be reliably eliminated. With this, the influence of the irregularities on the surface caused by the creases can be accurately reflected on the measurement result of each of the measurement lengths, and by extension, the measurement accuracy of each of the measurement lengths can be improved. 
     In the above-mentioned glass roll manufacturing method, it is preferred that the section to be measured be divided from the effective portion and discarded. 
     With this, the section to be measured in which the surface may have been contaminated through contact with the rotating body provided to the measurement unit is discarded without forming a part of the divided band-shaped glass film (effective portion) forming the glass roll. Therefore, it is possible to manufacture the glass roll comprising only the divided band-shaped glass film in which the surface is in a clean state. 
     In the above-mentioned glass roll manufacturing method, it is preferred that a speed at which each part is cooled and solidified through use of three heating units that are respectively configured to heat the one side end portion, the another side end portion, and the center portion positioned between the one side end portion and the another side end portion of the glass ribbon be adjusted. 
     With this, the speeds at which the one side end portion, the another side end portion, and the center portion of the glass ribbon are cooled and solidified can be easily adjusted individually. Therefore, the above-mentioned configuration is advantageous for manufacturing the glass roll of higher quality. 
     Further, according to the present invention, there is provided a glass roll quality evaluation method, comprising: a sampling step of extracting a sample glass roll from a plurality of glass rolls manufactured under the same condition; a measuring step of measuring, in an effective section in which one side edge and another side edge in a width direction of a band-shaped glass film forming the sample glass roll and having creases formed thereon extend in parallel to each other and in which each of a leading end portion and a trailing end portion extends in parallel to the width direction of the band-shaped glass film, a length from the leading end portion to the trailing end portion along a surface of the effective section along each of one side end portion and another side end portion in the width direction of the band-shaped glass film through use of a roll-to-roll mode; and a determination step of determining validity of quality of the plurality of glass rolls excluding the sample glass roll based on a difference between one side measurement length and another side measurement length which are respectively measured along the one side end portion and the another side end portion. 
     According to the method of the present invention, through performance of the measuring step, the validity of the balance in number and size of the creases between the one side end portion and the another side end portion in the width direction of the band-shaped glass film forming the sample glass roll is found as the difference between both the one side measurement length and the another side measurement length. When the difference between both the measurement lengths is smaller, the balance is more satisfactory. When the roll-to-roll mode is used, skew and single slack are less liable to occur in the band-shaped glass film. In this case, the sample glass roll is extracted from the plurality of glass rolls in the sampling step, and the plurality of glass rolls are manufactured under the same condition. That is, the sample glass roll and each of the plurality of glass rolls excluding the sample glass roll can be considered to be substantially the same glass rolls. Therefore, when the sample glass roll can prevent the above-mentioned occurrence of skew and single slack, each of the plurality of glass rolls excluding the sample glass roll can also be considered to be able to similarly prevent the occurrence of skew and single slack. As described above, according to the method of the present invention, the quality of the plurality of glass rolls can be suitably evaluated in association with performance of the determination step based on the difference between both the measurement lengths. 
     In the above-mentioned glass roll quality evaluation method, it is preferred that the determination step comprise determining that the quality of the plurality of glass rolls excluding the sample glass roll is accepted when the difference between the one side measurement length and the another side measurement length is 400 ppm or less of a longer measurement length of the one side measurement length and the another side measurement length. 
     With this, the band-shaped glass film forming each of the plurality of glass rolls in which the quality has been determined to be accepted in the determination step has sufficiently satisfactory balance in number and size of the creases between the one side end portion and the another side end portion in the width direction. With this, each of the plurality of glass rolls can be evaluated as a glass roll in which the occurrence of skew and single slack in the band-shaped glass film can be suitably prevented when the roll-to-roll mode is used. 
     In the above-mentioned glass roll quality evaluation method, it is preferred that the measuring step comprise measuring a length from the leading end portion to the trailing end portion along the surface of the effective section as a center measurement length along a center portion prevented from having the creases positioned between the one side end portion and the another side end portion of the band-shaped glass film through use of the roll-to-roll mode in addition to the one side measurement length and the another side measurement length, and, in the determination step, when the difference between the one side measurement length and the another side measurement length is 400 ppm or less of the longer measurement length of the one side measurement length and the another side measurement length, and a larger difference of a difference between the one side measurement length and the center measurement length and a difference between the another side measurement length and the center measurement length is 500 ppm or less of a longest measurement length of the one side measurement length, the another side measurement length, and the center measurement length, it is determined that the quality of the plurality of glass rolls excluding the sample glass roll is accepted as being excellent. 
     With this, the band-shaped glass film, which forms each of the plurality of glass rolls in which the quality has been determined to be accepted as being excellent in the determination step, has sufficiently satisfactory balance in number and size of the creases between the one side end portion and the another side end portion in the width direction. In addition, the number and size of the creases present in each of the one side end portion and the another side end portion are sufficiently suppressed. Thus, each of the plurality of glass rolls can be evaluated as a glass roll in which the occurrence of skew and single slack in the band-shaped glass film can be suitably prevented when the roll-to-roll mode is used and in which processing can be suitably performed on the band-shaped glass film. 
     In the above-mentioned glass roll quality evaluation method, it is preferred that a measuring unit be used for measuring each of the measurement lengths, and the measuring unit comprise a rotating body which is allowed to move in a thickness direction of the effective section in conformity with irregularities on the surface of the effective section caused by the creases while rotating through friction with the surface of the effective section under a state of being held in contact with the surface of the effective section, and be configured to measure each of the measurement lengths based on a distance by which the rotating body rolls on the surface of the effective section. 
     With this, the influence of the irregularities on the surface caused by the creases can be accurately reflected on the measurement result of each of the measurement lengths, and the measurement accuracy of each of the measurement lengths can be improved. 
     Advantageous Effects of Invention 
     According to the present invention, a glass roll in which the occurrence of skew and single slack in a band-shaped glass film can be prevented when the roll-to-roll mode is used can be provided. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view for illustrating a glass roll according to an embodiment of the present invention. 
         FIG. 2 a    is a plan view for illustrating a state in which a band-shaped glass film forming the glass roll according to the embodiment of the present invention is imaginarily unwound over an entire length from a winding core. 
         FIG. 2 b    is a plan view for illustrating a state in which the band-shaped glass film forming the glass roll according to the embodiment of the present invention is imaginarily unwound over an entire length from the winding core. 
         FIG. 3  is a side view for illustrating a mode of measuring a first measurement length to a third measurement length in the glass roll according to the embodiment of the present invention. 
         FIG. 4  is a plan view for illustrating the mode of measuring the first measurement length to the third measurement length in the glass roll according to the embodiment of the present invention. 
         FIG. 5 a    is a side view for illustrating the mode of measuring the first measurement length to the third measurement length in the glass roll according to the embodiment of the present invention under a state in which the periphery of a roller encoder is enlarged. 
         FIG. 5 b    is a side view for illustrating the mode of measuring the first measurement length to the third measurement length in the glass roll according to the embodiment of the present invention under the state in which the periphery of the roller encoder is enlarged. 
         FIG. 5 c    is a side view for illustrating the mode of measuring the first measurement length to the third measurement length in the glass roll according to the embodiment of the present invention under the state in which the periphery of the roller encoder is enlarged. 
         FIG. 6  is a side view for illustrating a glass roll manufacturing method according to an embodiment of the present invention. 
         FIG. 7  is a plan view for illustrating the glass roll manufacturing method according to the embodiment of the present invention. 
         FIG. 8  is a front view for illustrating the glass roll manufacturing method according to the embodiment of the present invention. 
         FIG. 9  is a view for illustrating a glass roll quality evaluation method according to an embodiment of the present invention. 
         FIG. 10 a    is an explanatory plan view for illustrating a problem in a related-art glass roll. 
         FIG. 10 b    is an explanatory plan view for illustrating the problem in the related-art glass roll. 
         FIG. 11 a    is an explanatory side view for illustrating a problem in the related-art glass roll. 
         FIG. 11 b    is an explanatory perspective view for illustrating the problem in the related-art glass roll. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Now, a glass roll, a glass roll manufacturing method, and a glass roll quality evaluation method according to embodiments of the present invention are described with reference to the accompanying drawings. 
     &lt;Glass Roll&gt; 
     First, a glass roll is described. 
     As illustrated in  FIG. 1 , a glass roll  1  comprises a band-shaped glass film  2  having flexibility and a band-shaped protective sheet  3  having flexibility. The band-shaped protective sheet  3  is configured to protect the band-shaped glass film  2  from the occurrence of a scratch and the like. The glass roll  1  is formed of the band-shaped glass film  2  and the band-shaped protective sheet  3  wound around a winding core  4  into a roll shape under a state in which the band-shaped glass film  2  and the band-shaped protective sheet  3  are superposed on one another. The band-shaped glass film  2  is formed so as to have a substantially uniform thickness over an entire width thereof, and has a thickness of, for example, 300 μm or less. In addition, the band-shaped glass film  2  has an entire length of, for example, 100 m or more. 
     Here, in this embodiment, the band-shaped protective sheet  3  has a width dimension larger than that of the band-shaped glass film  2 , but the present invention is not limited thereto. As a modification example of this embodiment, both the band-shaped glass film  2  and the band-shaped protective sheet  3  may have the same width dimension, or the band-shaped glass film  2  may have a width dimension larger than that of the band-shaped protective sheet  3 . 
     The state in which the band-shaped glass film  2  forming the glass roll  1  is imaginarily unwound over the entire length from the winding core  4  is illustrated in  FIG. 2 a   . As illustrated in  FIG. 2 a   , in the band-shaped glass film  2 , a leading end portion  2   a  that is one end portion along a longitudinal direction of the band-shaped glass film  2  and a trailing end portion  2   b  that is another end portion thereof are each formed in parallel to a width direction of the band-shaped glass film  2 . 
     The band-shaped glass film  2  is glass formed by cooling and solidifying a glass ribbon, which is obtained by forming molten glass into a band shape, while pulling the glass ribbon in a longitudinal direction as typified by an overflow down-draw method. Edge portions (parts each having a thickness larger than those of other parts) formed at both ends in the width direction along with the forming are divided and removed. The band-shaped glass film  2  comprises one side end portion  2   c  in the width direction comprising a first position P 1  described later, another side end portion  2   d  comprising a second position P 2  described later, and a center portion  2   e  comprising a widthwise center line CL and being positioned between both the end portions  2   c  and  2   d . In the one side end portion  2   c  and the another side end portion  2   d , creases  5  are formed to cause irregularities to be present on a surface  2   f . Meanwhile, in the center portion  2   e , the creases  5  are not formed, and the surface  2   f  is flat. 
     Here, in this embodiment, the creases  5  are formed in the one side end portion  2   c  and the another side end portion  2   d  among three parts comprising the one side end portion  2   c , the another side end portion  2   d , and the center portion  2   e  of the band-shaped glass film  2 , but the present invention is not limited thereto. As a modification example of this embodiment, the creases  5  may be formed in only one of the three parts. For example, the creases  5  may be formed in only the one side end portion  2   c  or only the another side end portion  2   d.    
     The band-shaped glass film  2  comprises an effective section  6  in which a first measurement length L 1  to a third measurement length L 3  described later are to be measured. The effective section  6  is a section in which one side edge  2   g  and another side edge  2   h  in the width direction extend in parallel to each other in the band-shaped glass film  2 , and a leading end portion  6   a  and a trailing end portion  6   b  thereof each extend in parallel to the width direction. That is, the effective section  6  has a rectangular shape in plan view of the band-shaped glass film  2 . With this, when the effective section  6  is formed so as to be longest in the band-shaped glass film  2  illustrated in  FIG. 2 a   , the entire length of the band-shaped glass film  2  forms the effective section  6 . In this case, the leading end portion  2   a  of the band-shaped glass film  2  and the leading end portion  6   a  of the effective section  6  are matched with each other, and the trailing end portion  2   b  of the band-shaped glass film  2  and the trailing end portion  6   b  of the effective section  6  are matched with each other. 
     Here, based on the definition of the effective section  6 , when each of the leading end portion  2   a  and the trailing end portion  2   b  of the band-shaped glass film  2  extends in a direction inclined with respect to the width direction as illustrated in  FIG. 2 b    as a modification example of this embodiment, the effective section  6  becomes a section obtained by excluding parts indicated by the cross-hatching even when the effective section  6  is formed so as to be longest. In this case, the leading end portion  2   a  of the band-shaped glass film  2  and the leading end portion  6   a  of the effective section  6  are not matched with each other, and the trailing end portion  2   b  of the band-shaped glass film  2  and the trailing end portion  6   b  of the effective section  6  are not matched with each other. 
     As is apparent from the description above, the length of the effective section  6  (length along the longitudinal direction of the band-shaped glass film  2 ) may be set to an arbitrary length. It is preferred that the length of the effective section  6  be set to 20 m or more. 
     The first measurement length L 1 , the second measurement length L 2 , and the third measurement length L 3  are lengths obtained by measuring lengths from the leading end portion  6   a  to the trailing end portion  6   b  along the surface  2   f  of the effective section  6 , respectively, along the first position P 1  along the one side edge  2   g  of the band-shaped glass film  2 , the second position P 2  along the another side edge  2   h  thereof, and the widthwise center line CL thereof. When each of the measurement lengths L 1  to L 3  is measured along the surface  2   f , the influence of the irregularities on the surface  2   f  caused by the creases  5  is reflected on the measurement results of the first measurement length L 1  and the second measurement length L 2 , and the number quantity and size magnitude of the creases  5  are reflected as the magnitude of the measurement length on the measurement results. Meanwhile, the measurement result of the third measurement length L 3  is not influenced by the irregularities on the surface  2   f  caused by the creases  5 . 
     The first position P 1  and the second position P 2  are positions respectively apart from the one side edge  2   g  and the another side edge  2   h  by 50 mm toward an inner side in the width direction. In this embodiment, the first measurement length L 1  and the second measurement length L 2  respectively measured along the first position P 1  and the second position P 2  are measured through use of a roller encoder  7  described later. Therefore, when obstacles that hinder the measurement using the roller encoder  7  are present at the above-mentioned positions apart by 50 mm, the positions apart from the obstacles are respectively defined as the first position P 1  and the second position P 2  instead. Specifically, positions apart from the obstacles by 10 mm toward an inner side in the width direction are respectively defined as the first position P 1  and the second position P 2 . Examples of the obstacle include a reinforcing tape affixed to the surface  2   f  along the longitudinal direction in order to reinforce the band-shaped glass film  2 . 
     A difference between the first measurement length L 1  and the second measurement length L 2  (absolute value of L 1 -L 2 ) is 400 ppm or less of a longer measurement length of both the measurement lengths L 1  and L 2 . When this condition is satisfied, the balance in number and size of the creases  5  present between the one side end portion  2   c  and the another side end portion  2   d  of the band-shaped glass film  2  becomes satisfactory in terms of preventing the occurrence of skew and single slack in the band-shaped glass film  2  when a roll-to-roll mode is used. The difference between both the measurement lengths L 1  and L 2  is preferably 200 ppm or less of the longer measurement length, more preferably 100 ppm or less of the longer measurement length. 
     In addition, of a difference between the first measurement length L 1  and the third measurement length L 3  (absolute value of L 1 -L 3 ) and a difference between the second measurement length L 2  and the third measurement length L 3  (absolute value of L 2 -L 3 ), a larger difference is 500 ppm or less of a longest measurement length of the first measurement length L 1  to the third measurement length L 3 . When this condition is satisfied, the number and size of the creases  5  present in each of the one side end portion  2   c  and the another side end portion  2   d  of the band-shaped glass film  2  are sufficiently suppressed in terms of suitably performing processing on the band-shaped glass film  2  when the roll-to-roll mode is used. The above-mentioned larger difference is preferably 300 ppm or less of the longest measurement length, more preferably 200 ppm or less of the longest measurement length. 
     &lt;Measurement Mode of First Measurement Length to Third Measurement Length&gt; 
     Now, the measurement mode of the first measurement length L 1  to the third measurement length L 3  is described. 
     For example, as illustrated in  FIG. 3 , the first measurement length L 1  to the third measurement length L 3  are measured in the glass roll  1  according to this embodiment through use of the roll-to-roll mode. Specifically, each of the measurement lengths L 1  to L 3  is measured at a measurement position MP on a conveyance path while the band-shaped glass film  2  forming the glass roll  1  is unwound and conveyed from a first winding core  8  serving as the winding core  4 . After that, the band-shaped glass film  2  having passed through the measurement position MP is wound up around a second winding core  9  different from the first winding core  8  to obtain a glass roll  10  again. 
     The leading end portion  2   a  of the band-shaped glass film  2  is coupled to a trailing end portion of a band-shaped leader (not shown) that is wound up around the second winding core  9  ahead of the band-shaped glass film  2 . That is, the band-shaped glass film  2  is conveyed by being pulled by the leader. 
     The band-shaped protective sheet  3  superposed on the band-shaped glass film  2  in the glass roll  1  is unwound from the first winding core  8  together with the band-shaped glass film  2 . After that, the band-shaped protective sheet  3  is separated from the band-shaped glass film  2  and collected as a first sheet roll  11 . In addition, the band-shaped glass film  2  having passed through the measurement position MP is wound up around the second winding core  9  under a state of being superposed on a band-shaped protective sheet  13  supplied from a second sheet roll  12 . 
     The band-shaped glass film  2  being conveyed to the second winding core  9  after being unwound from the first winding core  8  is in a state of being stretched over a plurality of rollers  14  arranged along the conveyance path. In each of the plurality of rollers  14 , an axis extends along the width direction of the band-shaped glass film  2 . Each of the plurality of rollers  14  may be a drive roller connected to a drive source (for example, a motor) or may be a free roller. 
     Of the plurality of rollers  14 , a roller  15  arranged at the measurement position MP is arranged so as to nip the band-shaped glass film  2  that passes through the measurement position MP in a horizontal posture in the thickness direction together with a roller  7   a  provided to the roller encoder  7 . Specifically, the roller  15  is brought into abutment against the band-shaped glass film  2  from below, and the roller  7   a  is brought into abutment against the band-shaped glass film  2  from above. The diameter of the roller  15  is set to be larger than that of the roller  7   a.    
     Here, as a modification example of this embodiment, the roller  15  may be brought into abutment against the band-shaped glass film  2  from above, and the roller  7   a  provided to the roller encoder  7  may be brought into abutment against the band-shaped glass film  2  from below. 
     The roller encoder  7  functions as a measuring unit configured to measure each of the measurement lengths L 1  to L 3 . The roller  7   a  serving as a rotating body provided to the roller encoder  7  is allowed to rotate without sliding through friction with the surface  2   f  of the effective section  6  under a state of being always held in abutment against the surface  2   f . Each of the measurement lengths L 1  to L 3  is measured based on a distance by which the roller  7   a  rolls on the surface  2   f . Further, there is no particular limitation on a material for a rotation peripheral portion of the roller  7   a  that is brought into abutment against the surface  2   f . However, it is required to eliminate a risk in that each of the measurement lengths L 1  to L 3  is inaccurately measured due to sliding between the surface  2   f  and the rotation peripheral portion. Therefore, in this embodiment, silicon rubber that is suitable for preventing sliding is used as the material for the rotation peripheral portion. 
     As illustrated in  FIG. 4 , there are arranged three roller encoders  7  configured to respectively measure the first measurement length L 1 , the second measurement length L 2 , and the third measurement length L 3  to be measured along the first position P 1 , the second position P 2 , and the widthwise center line CL. Three rollers  7   a  respectively provided to the three roller encoders  7  are arranged along the width direction of the band-shaped glass film  2 , and are positioned at the same point on the conveyance path of the band-shaped glass film  2 . 
     As illustrated in  FIG. 5 a    to  FIG. 5 c   , the roller  7   a  provided to each of the roller encoders  7  can move in the thickness direction of the effective section  6  in conformity with the irregularities on the surface  2   f  of the effective section  6  caused by the creases  5 . Thus, as illustrated in  FIG. 5 a    to  FIG. 5 c   , when the roller  7   a  climbs over the crease  5  having reached the measurement position MP along with conveyance of the band-shaped glass film  2 , the roller  7   a  moves upward from an initial position indicated by the two-dot chain line to a position indicated by the solid line in  FIG. 5 b   . The “initial position” corresponds to a position given when the roller  7   a  rolls on a flat part without the creases  5  in the effective section  6 . In addition, the roller  7   a  is configured to always apply a certain load (load that acts in the thickness direction of the band-shaped glass film  2 ) to the effective section  6 . The magnitude of the load is set to such a degree that the roller  7   a  does not crush and flatten the crease  5  while the state in which the roller  7   a  and the surface  2   f  are always held in abutment against each other can be maintained. 
     As a modification example of this embodiment, the magnitude of the load applied by the roller  7   a  applies to the effective section  6  may be set to such a degree that the roller  7   a  crushes and flattens the crease  5 . Also in this case, the first measurement length L 1 , the second measurement length L 2 , and the third measurement length L 3  can be measured without any problem. 
     When the rollers  7   a  respectively provided to the roller encoders  7  finish rolling from the leading end portion  2   a  to the trailing end portion  2   b  along the surface  2   f  of the effective section  6  on the first position P 1 , the second position P 2 , and the widthwise center line CL, each of the measurement lengths L 1  to L 3  is measured. As a result, the difference between both the measurement lengths L 1  and L 2 , the difference between the first measurement length L 1  and the third measurement length L 3 , and the difference between the second measurement length L 2  and the third measurement length L 3  are found. 
     &lt;Glass Roll Manufacturing Method&gt; 
     Now, a manufacturing method for manufacturing the glass roll  1  is described. 
     As illustrated in  FIG. 6  to  FIG. 8 , the manufacturing method of the present invention comprises: a forming step of cooling and solidifying a glass ribbon  18 , which is obtained by forming molten glass  17  into a band shape with a forming trough  16 , while pulling the glass ribbon  18  in a longitudinal direction, to thereby obtain a band-shaped glass film  19  having the creases  5  formed thereon; a dividing step of dividing both unnecessary portions  19   a  and  19   a  that are respectively present at both ends in a width direction of the band-shaped glass film  19  from an effective portion  19   b  positioned between both the unnecessary portions  19   a  and  19   a ; a winding step of winding up the divided band-shaped glass film  2  formed of the effective portion  19   b  into a roll shape, to thereby obtain the glass roll  1 ; and a measurement step of measuring, in a section S to be measured (section indicated by the hatched lines in  FIG. 7 ) which is formed in the effective portion  19   b , lengths from a leading end portion Sa to a trailing end portion Sb along the surface  2   f , respectively, along the one side end portion  2   c , the another side end portion  2   d , and the center portion  2   e  positioned between both the end portions  2   c  and  2   d  in the width direction of the effective portion  19   b.    
     Further, the manufacturing method of the present invention comprises performing a first adjusting step of adjusting to reduce, based on the result of the measurement step, a difference between speeds at which both one side end portion  18   a  and another side end portion  18   b  in the width direction of the glass ribbon  18  respectively connected to the one side end portion  2   c  and the another side end portion  2   d  of the effective portion  19   b  are cooled and solidified. In addition, the manufacturing method of the present invention comprises performing a second adjusting step of adjusting to reduce, based on the result of the measurement step, differences between speeds at which both the end portions  18   a  and  18   b  of the glass ribbon  18  are cooled and solidified and a speed at which a center portion  18   c  positioned between both the end portions  18   a  and  18   b  is cooled and solidified. 
     Here, the phrase “reduce a difference between speeds at which parts of the glass ribbon  18  are cooled and solidified” means reducing a distance (distance along a vertical direction in this embodiment) along a path between a point at which one part is cooled and solidified and a point at which another part is cooled and solidified on a path through which the glass ribbon  18  passes. Thus, when the difference between the speeds at which both the parts are cooled and solidified is zero, both the parts are cooled and solidified at the same point on the path through which the glass ribbon  18  passes. 
     When the forming step is performed, there are used, mainly, the forming trough  16  having a wedge shape for the overflow down-draw method, a roller group  20  formed of roller pairs arranged vertically in a plurality of stages, which are configured to pull down the glass ribbon  18  flowing down from the forming trough  16  while nipping the glass ribbon  18  from both front and back sides, and a heater group  21  formed of three heaters  21   a ,  21   b , and  21   c  serving as heating units capable of respectively heating both the end portions  18   a  and  18   b  and the center portion  18   c  of the glass ribbon  18  that is flowing down. Of the three components  16 ,  20 , and  21  to be used in the forming step, the configurations and operations of the forming trough  16  and the roller group  20  have already been known. Therefore, the detailed description thereof is omitted, and only the heater group  21  is described in detail. 
     The heater group  21  is arranged in an annealing furnace (not shown) configured to anneal the glass ribbon  18  to a temperature equal to or lower than a strain point, and the heaters  21   a ,  21   b , and  21   c  forming the heater group  21  are arranged at the same point on a path through which the glass ribbon  18  flows down. That is, the heaters  21   a ,  21   b , and  21   c  are located at the same height position. The heaters  21   a ,  21   b , and  21   c  may each independently change the magnitude of heat energy applied to the glass ribbon  18 . With this, the speeds at which the one side end portion  18   a , the another side end portion  18   b , and the center portion  18   c  of the glass ribbon  18  are cooled and solidified can be individually adjusted. 
     Here, in this embodiment, only one heater group  21  is arranged on the path through which the glass ribbon  18  flows down, but the present invention is not limited thereto. As a modification example of this embodiment, a plurality of heater groups  21  may be vertically arranged in a plurality of stages along the path through which the glass ribbon  18  flows down. In addition, as long as the difference between the speeds at which the parts of the glass ribbon  18  are cooled and solidified can be changed, it is not required to arrange the three heaters  21   a ,  21   b , and  21   c . For example, as a modification example of this embodiment, only the heater  21   c  among the three heaters may be arranged. 
     The one side end portion  18   a  of the glass ribbon  18  comprises a part that becomes the unnecessary portion  19   a  of the band-shaped glass film  19  after being cooled and solidified and a part that becomes the one side end portion  2   c  in the effective portion  19   b  of the band-shaped glass film  19  after being cooled and solidified. Similarly, the another side end portion  18   b  comprises a part that becomes the unnecessary portion  19   a  of the band-shaped glass film  19  after being cooled and solidified and apart that becomes the another side end portion  2   d  in the effective portion  19   b  of the band-shaped glass film  19  after being cooled and solidified. Further, the center portion  18   c  of the glass ribbon  18  becomes the center portion  2   e  of the effective portion  19   b  after being cooled and solidified. 
     The band-shaped glass film  19  obtained in the forming step is formed so as to have a thickness of, for example, 300 μm or less. The unnecessary portion  19   a  of the band-shaped glass film  19  comprises an edge portion having a thickness larger than those of the other parts. The mode by which the creases  5  are formed on the band-shaped glass film  19  is not limited to the description in this embodiment. Here, there is given a case as an example in which the creases  5  are formed in both the unnecessary portions  19   a  and  19   a  of the band-shaped glass film  19  and the one side end portion  2   c  and the another side end portion  2   d  of the effective portion  19   b , and the creases  5  are not formed in the center portion  2   e  of the effective portion  19   b.    
     Here, in this embodiment, the band-shaped glass film  19  is formed by the overflow down-draw method. However, as a modification example of this embodiment, the band-shaped glass film  19  may be formed by a slot down-draw method, a redraw method, or the like. 
     The conveyance direction of the band-shaped glass film  19  conveyed vertically downward after being formed is converted from a vertically downward direction to a horizontal direction by a roller group  22  formed of a plurality of rollers arranged along a curved conveyance track. Then, while the band-shaped glass film  19  is conveyed in the horizontal direction by a conveyor  23 , a plate-shaped body  24 , and a conveyor  25 , the band-shaped glass film  19  is caused to sequentially pass through a measurement position X and a dividing position Y on the conveyance path. 
     Here, in this embodiment, in the conveyance path of the band-shaped glass film  19 , the measurement position X is arranged in a section through which the band-shaped glass film  19  is conveyed in the horizontal direction, but the present invention is not limited thereto. As a modification example of this embodiment, the measurement position X may be arranged in the section through which the band-shaped glass film  19  is conveyed in the vertically downward direction. 
     In the measurement step performed at the measurement position X, a first measurement length (hereinafter referred to as “first measurement length LL 1 ”), a second measurement length (hereinafter referred to as “second measurement length LL 2 ”), and a third measurement length (hereinafter referred to as “third measurement length LL 3 ”) that are respectively measured along the one side end portion  2   c , the another side end portion  2   d , and the center portion  2   e  of the effective portion  19   b  are measured through use of three roller encoders  26  that each function as a measurement unit. The “center portion  2   e ” of the effective portion  19   b  means a part having a width of 200 mm positioned at the center in the width direction of the effective portion  19   b . In addition, the “one side end portion  2   c ” and the “another side end portion  2   d ” of the effective portion  19   b  mean parts each positioned on an outer side in the width direction of the center portion  2   e . Each of the measurement lengths LL 1  To LL 3  is measured at an arbitrary position within a width of each of the one side end portion  2   c , the another side end portion  2   d , and the center portion  2   e.    
     The section S to be measured in which each of the measurement lengths LL 1  to LL 3  is to be measured is a section which is formed along a longitudinal direction of the effective portion  19   b  of the band-shaped glass film  19  and in which each of the leading end portion Sa and the trailing end portion Sb extends in parallel to the width direction. That is, the section S to be measured has a rectangular shape in plan view of the band-shaped glass film  19 . The length of the section S to be measured (length along the longitudinal direction of the band-shaped glass film  19 ) may be set to an arbitrary length, and the length of the section S to be measured is set to preferably 20 m or more. 
     Each of the measurement lengths LL 1  to LL 3  is measured along the surface  2   f  of the section S to be measured. Therefore, the influence of the irregularities on the surface  2   f  caused by the creases  5  is reflected on the measurement results of the first measurement length LL 1  and the second measurement length LL 2 , and the number quantity and size magnitude of the creases  5  are reflected as the magnitude of the measurement length on the measurement results. Meanwhile, the measurement result of the third measurement length LL 3  is not influenced by the irregularities on the surface  2   f  caused by the creases  5 . 
     Each of the roller encoders  26  used for performing the measurement step has the same configuration as that of the roller encoder  7  described in the &lt;Measurement Mode of First Measurement Length to Third Measurement Length&gt; section and can perform the same operation as that of the roller encoder  7 . Therefore, the description thereof is omitted here. When rollers  26   a  serving as rotating bodies respectively provided to the roller encoders  26  finish rolling from the leading end portion Sa to the trailing end portion Sb along the surface  2   f  of the section S to be measured in the one side end portion  2   c , the another side end portion  2   d , and the center portion  2   e  of the effective portion  19   b , measurement of each of the measurement lengths LL 1  to LL 3  is completed. 
     As a result of the measurement step, when a difference between both the first measurement length LL 1  and the second measurement length LL 2  (absolute value of LL 1 -LL 2 ) is more than 400 ppm of a longer measurement length of both the measurement lengths LL 1  and LL 2 , the first adjusting step is performed. The first adjusting step may be performed independently or performed together with the second adjusting step described later. 
     In this embodiment, description is given of an example in which the first measurement length LL 1  is longer than the second measurement length LL 2 , and the difference between both the measurement lengths LL 1  and LL 2  is more than 400 ppm of the first measurement length LL 1 . In this case, in the one side end portion  2   c  of the effective portion  19   b , the number of the creases  5  is excessively large, and the size of each of the creases  5  is excessively large as compared to those of the another side end portion  2   d . Thus, the balance in number and size of the creases  5  present between both the end portions  2   c  and  2   d  deteriorates. 
     Here, as a result of extensive studies, the inventors of the present invention have found that the deterioration of the balance in number and size of the creases  5  present between the one side end portion  2   c  and the another side end portion  2   d  of the effective portion  19   b  is caused by an unsatisfactory balance between the difference in speed at which the center portion  18   c  and the one side end portion  18   a  of the glass ribbon  18  are cooled and solidified and the difference in speed at which the center portion  18   c  and the another side end portion  18   b  are cooled and solidified. In general, the speed at which the center portion  18   c  is cooled and solidified is higher than the speeds at which any of both the end portions  18   a  and  18   b  are cooled and solidified. In this embodiment, the difference between the speeds at which the center portion  18   c  and the one side end portion  18   a  are cooled and solidified is excessively larger than the difference between the speeds at which the center portion  18   c  and the another side end portion  18   b  are cooled and solidified. 
     In order to correct such state, the difference between the speeds at which both the end portions  18   a  and  18   b  of the glass ribbon  18  are cooled and solidified is adjusted to be reduced through use of the heaters  21   a ,  21   b , and  21   c . As a result, the balance between the difference in speed at which the center portion  18   c  and the one side end portion  18   a  of the glass ribbon  18  are cooled and solidified and the difference in speed at which the center portion  18   c  and the another side end portion  18   b  are cooled and solidified is improved. Preferably, the difference between the speeds at which both the end portions  18   a  and  18   b  are cooled and solidified is adjusted to be zero so that both the end portions  18   a  and  18   b  are cooled and solidified at the same point on the path through which the glass ribbon  18  flows down. 
     Specifically, any of the following operations (A) and (B) is performed. (A) Under a state in which the speed at which one of the one side end portion  18   a  and the another side end portion  18   b  is cooled and solidified is fixed, the speed at which another of the one side end portion  18   a  and the another side end portion  18   b  is cooled and solidified is brought close to the speed at which one of the one side end portion  18   a  and the another side end portion  18   b  is cooled and solidified. As a specific example, under a state in which the speed at which the another side end portion  18   b  is cooled and solidified is fixed, the speed at which the one side end portion  18   a  is cooled and solidified is increased. (B) While the speeds at which both the one side end portion  18   a  and the another side end portion  18   b  are cooled and solidified are changed, the speeds at which both the one side end portion  18   a  and the another side end portion  18   b  are cooled and solidified are brought close to each other. As a specific example, while the speeds at which both the one side end portion  18   a  and the another side end portion  18   b  are cooled and solidified are increased, the speeds at which both the one side end portion  18   a  and the another side end portion  18   b  are cooled and solidified are brought close to each other. 
     After the first adjusting step is performed, the measurement step is performed again through use of a section different from the above-mentioned section S to be measured as a new section S to be measured. The “new section S to be measured” is a section along the longitudinal direction of the effective portion  19   b  formed after the first adjusting step is performed. 
     As a result of the measurement step performed again, when the difference between both the measurement lengths LL 1  and LL 2  is equal to or less than 400 ppm of the first measurement length LL 1 , the above-mentioned balance is considered to have been improved, and the state of the operation of the heaters  21   a ,  21   b , and  21   c  is maintained in the state after the first adjusting step. 
     Meanwhile, as a result of the measurement step performed again, when the difference between both the measurement lengths LL 1  and LL 2  is still more than 400 ppm of the first measurement length LL 1 , both the measurement step and the first adjusting step are alternately performed until the difference between both the measurement lengths LL 1  and LL 2  reaches 400 ppm or less of the first measurement length LL 1  while the section S to be measured is changed to a new section every time the measurement step is performed. 
     Further, as a result of the measurement step, when at least one of two differences comprising a difference between the first measurement length LL 1  and the third measurement length LL 3  (absolute value of LL 1 -LL 3 ) and a difference between the second measurement length LL 2  and the third measurement length LL 3  (absolute value of LL 2 -LL 3 ) is more than 500 ppm of a longest measurement length of the first measurement length LL 1  to the third measurement length LL 3 , the second adjusting step is performed. The second adjusting step may be performed independently or performed together with the first adjusting step. 
     In this embodiment, description is given of an example in which both the two differences comprising the difference between the first measurement length LL 1  and the third measurement length LL 3  and the difference between the second measurement length LL 2  and the third measurement length LL 3  are more than 500 ppm of the first measurement length LL 1  that is longest among the first measurement length LL 1  to the third measurement length LL 3 . In this case, the number and size of the creases  5  cannot be sufficiently suppressed in both the one side end portion  2   c  and the another side end portion  2   d  of the effective portion  19   b.    
     Here, as a result of extensive studies, the inventors of the present invention have found that the insufficient suppression of the number and size of the creases  5  in the one side end portion  2   c  and the another side end portion  2   d  of the effective portion  19   b  is caused by a large difference between the speeds at which the center portion  18   c  and the one side end portion  18   a  of the glass ribbon  18  are cooled and solidified and between the speeds at which the center portion  18   c  and the another side end portion  18   b  of the glass ribbon  18  are cooled and solidified. In this embodiment, the speeds at which the one side end portion  18   a  and the another end portion  18   b  are cooled and solidified are excessively slower than that of the center portion  18   c.    
     In order to correct such state, the differences between the speeds at which both the end portions  18   a  and  18   b  of the glass ribbon  18  are cooled and solidified and the speed at which the center portion  18   c  is cooled and solidified are adjusted in order to reduce the difference in speed through use of the heaters  21   a ,  21   b , and  21   c . Preferably, the differences between the speeds at which both the end portions  18   a  and  18   b  are cooled and solidified and the speed at which the center portion  18   c  is cooled and solidified are adjusted to be zero so that both the end portions  18   a  and  18   b  and the center portion  18   c  are cooled and solidified at the same point on the path through which the glass ribbon  18  flows down. 
     Specifically, any of the following operations (C) and (D) is performed. (C) Under a state in which one of the speeds at which both the end portions  18   a  and  18   b  are cooled and solidified and the speed at which the center portion  18   c  is cooled and solidified is fixed, another of the speeds at which both the end portions  18   a  and  18   b  are cooled and solidified and the speed at which the center portion  18   c  is cooled and solidified is brought close to one of the speeds at which both the end portions  18   a  and  18   b  are cooled and solidified and the speed at which the center portion  18   c  is cooled and solidified. As a specific example, under a state in which the speed at which the center portion  18   c  is cooled and solidified is fixed, the speeds at which both the end portions  18   a  and  18   b  are cooled and solidified are increased. Further, as another specific example, under a state in which the speeds at which both the end portions  18   a  and  18   b  are cooled and solidified are fixed, the speed at which the center portion  18   c  is cooled and solidified is decreased. (D) Both the speeds at which both the end portions  18   a  and  18   b  are cooled and solidified and the speed at which the center portion  18   c  is cooled and solidified are changed to bring both the speeds close to each other. As a specific example, the speeds at which both the end portions  18   a  and  18   b  are cooled and solidified are increased, and the speed at which the center portion  18   c  is cooled and solidified is decreased, to thereby bring both the speeds close to each other. 
     After the second adjusting step is performed, the measurement step is performed again through use of a section different from the above-mentioned section S to be measured as a new section S to be measured. The “new section S to be measured” is a section along the longitudinal direction of the effective portion  19   b  formed after the second adjusting step is performed. 
     As a result of the measurement step performed again, when both the difference between the first measurement length LL 1  and the third measurement length LL 3  and the difference between the second measurement length LL 2  and the third measurement length LL 3  are 500 ppm or less of the first measurement length LL 1  that is longest, the number and size of the creases  5  are considered to have been sufficiently suppressed in both the one side end portion  2   c  and the another side end portion  2   d . Then, the state of the operation of the heaters  21   a ,  21   b , and  21   c  is maintained in the state after the second adjusting step. 
     Meanwhile, as a result of the measurement step performed again, when the difference between both the measurement lengths LL 1  and LL 2  is more than 500 ppm of a longest measurement length of the first measurement length LL 1 , both the measurement step and the second adjusting step are alternately performed until the difference between both the measurement lengths LL 1  and LL 2  reaches 500 ppm or less of a longest measurement length of the first measurement length LL 1  while the section S to be measured is changed to a new section every time the measurement step is performed. 
     In the measurement step performed once or a plurality of times, there is a fear in that the surface  2   f  of a section serving as the section S to be measured in the effective portion  19   b  may have been contaminated through contact with the roller  26   a  provided to the roller encoder  26 , and hence the section serving as the section S to be measured is divided from a section of the effective portion  19   b  to be wound and discarded. Further, in the effective section  19   b , a section that is formed before the difference between both the measurement lengths LL 1  and LL 2  reaches 400 ppm or less of the longer measurement length (in this case, the first measurement length LL 1 ) is also divided from the section of the effective portion  19   b  to be wound and discarded as a defective section. The detail is described later. 
     The band-shaped glass film  19  having reached the dividing position Y after passing through the measurement position X is subjected to the dividing step, and cutting is performed along boundary lines B 1  and B 2  between the effective portion  19   b  and both the unnecessary portions  19   a  and  19   a  through use of a laser  27 . With this, both the unnecessary portions  19   a  and  19   a  are divided from the effective portion  19   b . Cutting through use of the laser  27  may be performed, for example, by a laser cleaving method that has been already known. Both the unnecessary portions  19   a  and  19   a  after being divided are dropped down from the conveyor  25  and discarded. 
     The effective portion  19   b  (the band-shaped glass film  2  after being divided), which have been divided from both the unnecessary portions  19   a  and  19   a  and have passed through the dividing position Y, is caused to pass through a slack conveyance position Z at which the effective portion  19   b  is conveyed under a state of being slack downward to reach the winding core  4 . The section serving as the section S to be measured and the effective portion  19   b  excluding the section determined to be the defective section are caused to pass through the slack conveyance position Z to reach the winding core  4 . The section determined to be the defective section and the section serving as the section S to be measured are divided from the section to be wound without reaching the winding core  4 , and dropped downward at the slack conveyance position Z to be discarded. 
     As described above, when the effective portion  19   b  formed of a section other than the section to be discarded is wound up around the winding core  4  to complete winding of a desired length, the glass roll  1  is completed. When the effective portion  19   b  is wound up around the winding core  4 , the effective portion  19   b  is wound up under a state of being superposed on the band-shaped protective sheet  3  supplied from a third sheet roll  28 . 
     Here, in this embodiment, the difference between the speeds at which both the one side end portion  18   a  and the another side end portion  18   b  of the glass ribbon  18  are cooled and solidified is adjusted in order to reduce the difference in speed in the first adjusting step, but the present invention is not limited thereto. The first adjusting step may be performed in a mode different from that of this embodiment as long as the difference between both the measurement lengths LL 1  and LL 2  is adjusted to be reduced. 
     In addition, in this embodiment, the differences between the speeds at which both the end portions  18   a  and  18   b  of the glass ribbon  18  are cooled and solidified and the speed at which the center portion  18   c  positioned between both the end portions  18   a  and  18   b  is cooled and solidified are adjusted in order to reduce the difference in speed in the second adjusting step, but the present invention is not limited thereto. The second adjusting step may be performed in a mode different from that of this embodiment as long as, of the two differences comprising (absolute value of LL 1 -LL 3 ) and (absolute value of LL 2 -LL 3 ), the difference that is more than 500 ppm of the longest measurement length of LL 1  to LL 3  is adjusted to be reduced. 
     &lt;Glass Roll Quality Evaluation Method&gt; 
     Now, a method of evaluating quality of the glass roll  1  is described. In the description of the evaluation method of the present invention, the same elements as those described in the &lt;Glass Roll&gt; section, the &lt;Measurement Mode of First Measurement Length to Third Measurement Length&gt; section, and the &lt;Glass Roll Manufacturing Method&gt; section are denoted by the same reference symbols as those in the description therein, and overlapping description is omitted. 
     A flow of the evaluation method of the present invention is illustrated in  FIG. 9 . In the evaluation method of the present invention, first, a sampling step of extracting a sample glass roll  1   a  from the plurality of glass rolls  1  manufactured under the same condition is performed. The plurality of glass rolls  1  are manufactured under the same forming condition (the state of the operation of the heaters  21   a ,  21   b , and  21   c  is also the same), the same dividing condition, and the same winding condition, for example, by the &lt;Glass Roll Manufacturing Method&gt;. 
     Here, in this embodiment, only one glass roll  1  is extracted as the sample glass roll  1   a , but the present invention is not limited thereto. As a modification example of this embodiment, two or more glass rolls  1  may be extracted. With this, the accuracy of determination in a determination step described later can be enhanced in proportion to an increase in number of the samples. In addition, as one example, the frequency of extraction when only one sample glass roll  1   a  is extracted is preferably one for every three days, more preferably one for every two days, still more preferably one for every day of manufacturing of the glass rolls. 
     The sample glass roll  1   a  extracted in the sampling step is subjected to a measuring step. In the measuring step, in the band-shaped glass film  2  having the creases  5  formed thereon, which forms the sample glass roll  1   a , the lengths from the leading end portion  2   a  to the trailing end portion  2   b  along the surface  2   f  of the effective section  6  are measured through use of the roll-to-roll mode. Specifically, the above-mentioned lengths are respectively measured along the one side end portion  2   c , the another side end portion  2   d , and the center portion  2   e  positioned between both the end portions  2   c  and  2   d  in the width direction of the effective section  6 , and the measurement results are respectively defined as one side measurement length (hereinafter referred to as “one side measurement length ML 1 ”), another side measurement length (hereinafter referred to as “another side measurement length ML 2 ”), and center measurement length (hereinafter referred to as “center measurement length ML 3 ”). 
     Here, the “center portion  2   e ” of the effective section  6  means a part having a width of 200 mm positioned at the center in the width direction of the effective section  6 . In addition, the “one side end portion  2   c ” and the “another side end portion  2   d ” of the effective section  6  mean parts each positioned on an outer side in the width direction of the center portion  2   e.    
     The specific mode for measuring the one side measurement length ML 1 , the another side measurement length ML 2 , and the center measurement length ML 3  is substantially the same as that ( FIG. 3  to  FIG. 5 c   ) for measuring the first measurement length L 1 , the second measurement length L 2 , and the third measurement length L 3 , and hence only differences from the measurement mode of the first measurement length L 1  to the third measurement length L 3  are described. 
     The first measurement length L 1 , the second measurement length L 2 , and the third measurement length L 3  are respectively measured along the first position P 1 , the second position P 2 , and the widthwise center line CL. Meanwhile, the one side measurement length ML 1 , the another side measurement length ML 2 , and the center measurement length ML 3  are lengths that are respectively measured along an arbitrary position within a width of the one side end portion  2   c , an arbitrary position within a width of the another side end portion  2   d , and an arbitrary position within a width of the center portion  2   e . That is, these three arbitrary positions may be or may not be matched with the first position P 1 , the second position P 2 , and the widthwise center line CL, respectively. 
     When the measuring step is completed, the determination step of determining validity of quality of the plurality of glass rolls  1  excluding the sample glass roll  1   a  is performed based on the difference between both the one side measurement length ML 1  and the another side measurement length ML 2 . 
     Here, the sample glass roll  1   a  and each of the plurality of glass rolls  1  excluding the sample glass roll  1   a  are manufactured under the same condition and can be considered to be substantially the same glass rolls  1 . Therefore, when the occurrence of skew and single slack in the band-shaped glass film  2  can be prevented in the sample glass roll  1   a  when the roll-to-roll mode is used, the same effect is considered to be attained also in each of the plurality of glass rolls  1 . In addition, when processing can be preferably performed on the band-shaped glass film in the sample glass roll  1   a  when the roll-to-roll mode is used, the same effect is considered to be attained also in each of the plurality of glass rolls  1 . 
     In the determination step, when a difference between both the measurement lengths ML 1  and ML 2  (absolute value of ML 1 -ML 2 ) is 400 ppm or less (preferably 200 ppm or less, more preferably 100 ppm or less) of a longer measurement length of both the measurement lengths ML 1  and ML 2 , it is determined that the quality of the plurality of glass rolls  1  excluding the sample glass roll  1   a  is accepted. Specifically, the plurality of glass rolls  1  excluding the sample glass roll  1   a  are determined to be the glass rolls  1  in which the occurrence of skew and single slack in the band-shaped glass film  2  can be prevented when the roll-to-roll mode is used. 
     In addition, when, of a difference between the one side measurement length ML 1  and the center measurement length ML 3  (absolute value of ML 1 -ML 3 ) and a difference between the another side measurement length ML 2  and the center measurement length ML 3  (absolute value of ML 2 -ML 3 ), a larger difference is 500 ppm or less (preferably 300 ppm or less, more preferably 200 ppm or less) of a longest measurement length of the three measurement lengths ML 1 , ML 2 , and ML 3 , it is determined that the quality of the plurality of glass rolls  1  excluding the sample glass roll  1   a  is accepted as being excellent. Specifically, the plurality of glass rolls  1  excluding the sample glass roll  1   a  are determined to be the glass rolls  1  in which the occurrence of skew and single slack in the band-shaped glass film  2  can be prevented when the roll-to-roll mode is used and in which processing can be preferably performed on the band-shaped glass film  2 . 
     EXAMPLES 
     In order to examine the presence or absence of the effects of the present invention, each of eight kinds of glass rolls (Examples: six kinds, Comparative Examples: two kinds) shown in the following [Table 1] and eight kinds of glass rolls (Examples: five kinds, Comparative Examples: three kinds) shown in [Table 2] was inspected for whether or not the occurrence of skew and single slack in the band-shaped glass film can be prevented when the roll-to-roll mode is used. In each of the glass rolls shown in [Table 1], the band-shaped glass film having a thickness of 100 μm is wound into a roll shape. In each of the glass rolls shown in [Table 2], the band-shaped glass film having a thickness of 50 μm is wound into a roll shape. 
     In this inspection, when the roll-to-roll mode was used, the band-shaped glass film was pulled and conveyed by a leader having the same width dimension as that of the band-shaped glass film. With this, when no skew occurs in the band-shaped glass film, end portions in a width direction of the subsequent band-shaped glass film pass through, without deviation, a passage line through which end portions in a width direction of the preceding leader have passed. 
     In addition, in this inspection, nip rollers (not shown) formed of a pair of rollers configured to nip the band-shaped glass film in the thickness direction were arranged on a conveyance path. With this, when skew occurs beyond an allowable range in the band-shaped glass film, single slack of the band-shaped glass film deteriorates on an immediate upstream side of the nip rollers, and there is an increased risk in that the band-shaped glass film may be broken. 
     “Calculation result 1” in items of the calculation result in [Table 1] and [Table 2] indicates a ratio between the difference between the first measurement length L 1  and the second measurement length L 2  (absolute value of L 1 -L 2 ) and the longer measurement length of both the measurement lengths L 1  and L 2 . When the value of the measurement result 1 is decreased, the balance in number and size of the creases is satisfactory between the one side end portion and the another side end portion in the width direction of the band-shaped glass film. 
     “Calculation result 2” in items of the calculation result in [Table 1] and [Table 2] indicates a ratio between the difference between the first measurement length L 1  and the third measurement length L 3  (absolute value of L 1 -L 3 ) and the longest measurement length of all the measurement lengths L 1 , L 2 , and L 3 . In addition, “Calculation result 3” indicates a ratio between the difference between the second measurement length L 2  and the third measurement length L 3  (absolute value of L 2 -L 3 ) and the longest measurement length of the first to third measurement lengths L 1 , L 2 , and L 3 . When a relatively larger value of the calculation result 2 and the calculation result 3 is decreased, the number and size of the creases present in each of the one side end portion and the another side end portion in the width direction of the band-shaped glass film are suppressed. 
     “Skew amount” in items of the roll-to-roll result in [Table 1] and [Table 2] is a value measured as described below. Specifically, the “Skew amount” is a value measured by determining how much a passage line through which the end portions in the width direction of the subsequent band-shaped glass film have passed deviates at a maximum in the width direction from a passage line through which the end portions in the width direction of the preceding leader have passed at a fixed point on the conveyance path of the band-shaped glass film. 
     The results of the inspection are shown in [Table 1] and [Table 2]. Each value shown in [Table 1] and [Table 2] is a value per 30,000 mm (per 30 m) of the third measurement length L 3 . 
     
       
         
           
               
               
               
               
             
               
                   
                 TABLE 1 
               
             
            
               
                   
                   
               
               
                   
                 Measurement result 
                   
                   
               
            
           
           
               
               
               
               
               
            
               
                   
                 First 
                 Second 
                 Third 
                   
               
            
           
           
               
               
               
               
               
               
            
               
                   
                 measure- 
                 measure- 
                 measure- 
                 Calculation result 
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                   
                 Band-shaped 
                 ment 
                 ment 
                 ment 
                 Calcula- 
                 Calcula- 
                 Calcula- 
                 Roll-to-roll result 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                   
                 glass film 
                 length 
                 length 
                 length 
                 tion 
                 tion 
                 tion 
                 Skew 
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
               
            
               
                   
                 Thickness 
                 Width 
                 L1 
                 L2 
                 L3 
                 result 1 
                 result 2 
                 result 3 
                 amount 
                 Single 
                   
               
               
                   
                 μm 
                 mm 
                 mm 
                 mm 
                 mm 
                 ppm 
                 ppm 
                 ppm 
                 mm 
                 slack 
                 Breakage 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
               
            
               
                 Example 1 
                 100 
                 500 
                 30,004.5 
                 30,004.8 
                 30,000 
                 10 
                 150 
                 160 
                 2 
                 None 
                 None 
               
               
                 Example 2 
                 100 
                 500 
                 30,006 
                 30,005.7 
                 30,000 
                 10 
                 200 
                 190 
                 2 
                 None 
                 None 
               
               
                 Example 3 
                 100 
                 500 
                 30,006.6 
                 30,006 
                 30,000 
                 20 
                 220 
                 200 
                 2 
                 None 
                 None 
               
               
                 Example 4 
                 100 
                 500 
                 30,008.1 
                 30,006 
                 30,000 
                 70 
                 270 
                 200 
                 4 
                 None 
                 None 
               
               
                 Example 5 
                 100 
                 500 
                 30,003.9 
                 30,007.2 
                 30,000 
                 110 
                 130 
                 240 
                 15 
                 None 
                 None 
               
               
                 Example 6 
                 100 
                 500 
                 30,004.2 
                 30,010.5 
                 30,000 
                 210 
                 140 
                 350 
                 17 
                 Occurrence 
                 None 
               
               
                 Comparative 
                 100 
                 500 
                 30,018.6 
                 30,006.3 
                 30,000 
                 410 
                 620 
                 210 
                 33 
                 Occurrence 
                 Occurrence 
               
               
                 Example 1 
               
               
                 Comparative 
                 100 
                 500 
                 30,023.1 
                 30,009.3 
                 30,000 
                 460 
                 770 
                 310 
                 39 
                 Occurrence 
                 Occurrence 
               
               
                 Example 2 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
               
             
               
                   
                 TABLE 2 
               
             
            
               
                   
                   
               
               
                   
                 Measurement result 
                   
                   
               
            
           
           
               
               
               
               
               
            
               
                   
                 First 
                 Second 
                 Third 
                   
               
            
           
           
               
               
               
               
               
               
            
               
                   
                 measure- 
                 measure- 
                 measure- 
                 Calculation result 
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                   
                 Band-shaped 
                 ment 
                 ment 
                 ment 
                 Calcula- 
                 Calcula- 
                 Calcula- 
                 Roll-to-roll result 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                   
                 glass film 
                 length 
                 length 
                 length 
                 tion 
                 tion 
                 tion 
                 Skew 
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
               
            
               
                   
                 Thickness 
                 Width 
                 L1 
                 L2 
                 L3 
                 result 1 
                 result 2 
                 result 3 
                 amount 
                 Single 
                   
               
               
                   
                 μm 
                 mm 
                 mm 
                 mm 
                 mm 
                 ppm 
                 ppm 
                 ppm 
                 mm 
                 slack 
                 Breakage 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
               
            
               
                 Example 7 
                 50 
                 800 
                 30,010.5 
                 30,008.4 
                 30,000 
                 70 
                 350 
                 280 
                 3 
                 Occurrence 
                 None 
               
               
                 Example 8 
                 50 
                 800 
                 30,005.1 
                 30,001.5 
                 30,000 
                 120 
                 170 
                 50 
                 15 
                 None 
                 None 
               
               
                 Example 9 
                 50 
                 800 
                 30,005.4 
                 30,001.2 
                 30,000 
                 140 
                 180 
                 40 
                 11 
                 None 
                 None 
               
               
                 Example 10 
                 50 
                 800 
                 30,013.8 
                 30,008.1 
                 30,000 
                 190 
                 460 
                 270 
                 18 
                 Occurrence 
                 None 
               
               
                 Example 11 
                 50 
                 800 
                 30,009 
                 30,003 
                 30,000 
                 200 
                 300 
                 100 
                 14 
                 Occurrence 
                 None 
               
               
                 Comparative 
                 50 
                 800 
                 30,030.9 
                 30,013.5 
                 30,000 
                 580 
                 1,030 
                 450 
                 45 
                 Occurrence 
                 Occurrence 
               
               
                 Example 3 
               
               
                 Comparative 
                 50 
                 800 
                 30,027.3 
                 30,012 
                 30,000 
                 510 
                 910 
                 400 
                 44 
                 Occurrence 
                 Occurrence 
               
               
                 Example 4 
               
               
                 Comparative 
                 50 
                 800 
                 30,026.4 
                 30,012 
                 30,000 
                 480 
                 880 
                 400 
                 39 
                 Occurrence 
                 Occurrence 
               
               
                 Example 5 
               
               
                   
               
            
           
         
       
     
     As is apparent from the results shown in [Table 1] and [Table 2], it is understood that, in each of Examples in which the value of the calculation result 1 was 400 ppm or less, breakage of the band-shaped glass film did not occur unlike each of Comparative Examples. It is assumed that such a result was obtained because of the following reason. In each of Examples, the skew amount was significantly suppressed as compared to that of each of Comparative Examples, and the occurrence of single slack was able to be substantially eliminated. In Example 6 in [Table 1], and Examples 7, 10, and 11 in [Table 2], single slack slightly occurred, but the single slack was able to be prevented from deteriorating to such a degree as to break the band-shaped glass film. It is presumed from the foregoing that, according to the glass roll of the present invention, the occurrence of skew and single slack in the band-shaped glass film can be suppressed when the roll-to-roll mode is used, with the result that the breakage of the band-shaped glass film can be avoided. 
     REFERENCE SIGNS LIST 
     
         
         
           
               1  glass roll 
               1   a  sample glass roll 
               2  band-shaped glass film 
               2   c  one side end portion 
               2   d  another side end portion 
               2   e  center portion 
               2   f  surface 
               2   g  one side edge 
               2   h  another side edge 
               5  crease 
               6  effective section 
               6   a  leading end portion 
               6   b  trailing end portion 
               7  roller encoder 
               7   a  roller 
               16  forming trough 
               17  molten glass 
               18  glass ribbon 
               18   a  one side end portion 
               18   b  another side end portion 
               18   c  center portion 
               19  band-shaped glass film 
               19   a  unnecessary portion 
               19   b  effective portion 
               21  heater group 
               21   a  to  21   c  heater 
               26  roller encoder 
               26   a  roller 
             CL widthwise center line 
             L 1  first measurement length 
             L 2  second measurement length 
             L 3  third measurement length 
             P 1  first position 
             P 2  second position 
             S section to be measured 
             Sa leading end portion 
             Sb trailing end portion